University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Talanta

  • Publisher: Elsevier
  • FAD Code: TALT
  • CODEN: TLNTA2
  • ISSN: 0039-9140
  • Abbreviation: Talanta
  • DOI Prefix: 10.1016/j.talanta,10.1016/0039-9140
  • Language: English
  • Comments: Fulltext from 1958 V1

Citations 1191

"Selective Stopped-flow Sequential Injection Method For The Spectrophotometric Determination Of Titanium In Dental Implant And Natural Moroccan Phosphate Rock"
Talanta 2007 Volume 71, Issue 3 Pages 1405-1410
Fotini S. Kika and Demetrius G. Themelis

Abstract: The present work reports the first sequential injection (SI) method for the spectrophotometric determination of Ti(IV). The method is based upon the reaction of Ti(IV) with chromotropic acid (CA) in acidic medium to form a water-soluble complex (?max = 420 nm). The chemical and instrumental variables of the system that affected the reaction were studied. Selectivity was greatly enhanced using ascorbic acid. A linear calibration graph was obtained in the range 0.2-10.0 mg L-1 Ti(IV) at a sampling frequency of 24 h-1. The precision was satisfactory (sr = 1.5% at 5.0 mg L-1 Ti(IV), n = 12) and the 3? limit of detection, cL, was 0.7 mg L-1 (n = 10). The developed method proved to be adequately selective and was applied successfully to the analysis of real samples (dental implant and natural Moroccan phosphate rock) giving accurate results based on recovery studies (98-105%). © 2006 Elsevier B.V. All rights reserved.

"Sequential Injection Analysis With Second-order Treatment For The Determination Of Dyes In The Exhaustion Process Of Tanning Effluents"
Talanta 2007 Volume 71, Issue 3 Pages 1393-1398
V. Gómez, J. Font and M.P. Callao

Abstract: A sequential injection (SI)-DAD spectrophotometric method to control the exhaustion of dyes in a mixture of three dyes from a tanning industry process has been developed. It is based on an interdiffusion process of the sample and reagents which leads to a gradual fall in pH through the channel to the detector recording a data matrix. The aim of this paper is to develop a second-order calibration model that is unaffected by interferents by applying multivariate curve resolution with alternating least squares (MCR-ALS). We obtained a linear calibration in the 5-30 mg L-1 range with a correlation coefficient of 0.999 for each dye with detection limits of 2.6, 3.9 and 2.1 mg L-1 for Acid Red, Acid Brown and Acid Orange, respectively. The simultaneous determination of the three dyes from tanning samples showed a satisfactory precision for the three analytes. The method has been validated comparing the concentration of some spiked samples with the expected concentration using a t-paired test. When we used this method to study the exhaustion of dyes, we found that there were several stages in this process. These data may be the key to optimising the exhaustion process. © 2006 Elsevier B.V. All rights reserved.

"Evaluation Of The Antioxidant Power Of Honey, Propolis And Royal Jelly By Amperometric Flow Injection Analysis"
Talanta 2007 Volume 71, Issue 3 Pages 1387-1392
S. Buratti, S. Benedetti and M.S. Cosio

Abstract: In this paper is described the applicability of a flow injection system, operating with an amperometric detector, for measurement in rapid and simple way the antioxidant power of honey, propolis and royal jelly. The proposed method evaluates the reducing power of selected antioxidant compounds and does not require the use of free radicals or oxidants. Twelve honey, 12 propolis and 4 royal jelly samples of different botanical and geographical origin were evaluated by the electrochemical method and the data were compared with those obtained by the DPPH assay. Since a good correlation was found (R2 = 0.92) the proposed electrochemical method can be successfully employed for the direct, rapid and simple monitoring of the antioxidant power of honeybee products. Furthermore, the total phenolic content of samples was determined by the Folin-Ciocalteau procedure and the characteristic antioxidant activities showed a good correlation with phenolics (R2 = 0.96 for propolis and 0.90 for honey). © 2006 Elsevier B.V. All rights reserved.

"Simultaneous On-line Preconcentration And Determination Of Trace Metals In Environmental Samples Using A Modified Nanometer-sized Alumina Packed Micro-column By Flow Injection Combined With ICP-OES"
Talanta 2007 Volume 71, Issue 3 Pages 1239-1245
Chaozhang Hang, Bin HuCorresponding Author Contact Information, E-mail The Corresponding Author, Zucheng Jiang and Nan Zhang

Abstract: A novel organic reagent 3-(8-quinolinylazo)-4-hydroxybenzoic acid (QAHBA) was synthesized for chemically modified nanometer-sized alumina, and it was characterized with infrared spectrum and 1H NMR spectra. By using modified nanometer-sized alumina as micro-column packing material, a new method of flow injection (FI) on-line pre-concentration coupled to ICP-OES was developed for simultaneous determination of trace metals (Ag, Pd, Au, Ga, In and Nb) in geological and environmental samples. The effects of pH, sample flow rate, sample volume, elution and interfering ions on the recovery of the analytes have been investigated. Under the optimized operating conditions, the adsorption capacity of the modified nanometer-sized alumina for Ag, Pd, Au, Ga, In and Nb were found to be 5.1, 7.6, 17.7, 15.6, 8.1 and 12.3 mg g-1, respectively. With 4 min pre-concentration time and 24 s elution time, the enrichment factor was 10 and the sample frequency was 10 h-1. The detection limits of this method for Ag, Pd, Au, Ga, In and Nb were 0.12, 0.44, 0.27, 0.19, 0.54 and 0.18 ?g l-1, respectively, while the RSDs were 1.6, 2.3, 4.5, 1.6, 1.9 and 1.7% (n = 7, c = 50 ng mL-1), respectively. The proposed method has been applied to the determination of these trace metals in geological-certified reference materials and natural water samples with satisfactory results. © 2006 Elsevier B.V. All rights reserved.

"Amperometric Detection Of Hydrazine By Cyclic Voltammetry And Flow Injection Analysis Using Ruthenium Modified Glassy Carbon Electrodes"
Talanta 2007 Volume 71, Issue 3 Pages 1219-1225
Jill S. PinterCorresponding Author Contact Information, E-mail The Corresponding Author, Kenneth L. Brown, Paul A. DeYoung and Graham F. Peaslee

Abstract: Glassy carbon electrodes modified with (5-amino-1,10-phenanthroline)bis(bipyridine)ruthium(II) chloride hydrate, [(bpy)2Ru(5-phenNH2)]Cl2⋅H2O, are shown to oxidize hydrazine with excellent sensitivity. The presence of an amine group on the ruthenium complex facilitates electropolymerization onto the electrode surface. Using cyclic voltammetry, a large catalytic current is observed upon oxidation of hydrazine in phosphate buffer (pH 5.0), compared to the current obtained from the ruthenium-modified electrode with no hydrazine present. The sensitivity of cyclic voltammetry is sufficient for obtaining a linear calibration curve for hydrazine over the range of 10^-5 to 10^-2 M. Hydrodynamic amperometry was used to determine the working potential for flow injection analysis. The limit of detection for hydrazine was determined to be 8.5 µM using FIA. The thickness of these films was shown to increase linearly with the number of electropolymerization cycles, in the range of 1000-2500 nm for 5-20 cycles, respectively, using Rutherford backscattering spectrometry (RBS). RBS analysis also suggests that the film is multilayered with the outermost layers containing a high ruthenium concentration, followed by layers where the concentration of ruthenium decreases linearly and approaches zero at the electrode surface. © 2006 Elsevier B.V. All rights reserved.

"Enzymatic Oxidation Of Tert-butylcatechol In The Presence Of Sulfhydryl Compounds: Application To The Amperometric Detection Of Penicillamine"
Talanta 2007 Volume 71, Issue 3 Pages 1198-1204
Angel A.J. Torriero, Corresponding Author Contact Information, E-mail The Corresponding Author, Hugo D. Piol, Noelia A. Martínez, Nancy V. Panini, Julio Raba and Juana J. Silber

Abstract: The high sensitivity that can be attained using an enzymatic system and mediated by 4-tert-butylcatechol (4-TBC) has been verified by on-line interfacing of a rotating biosensor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in presence of hydrogen peroxide catalyzed the oxidation of 4-TBC, whose back electrochemical reduction was detected on glassy carbon electrode surface at -150 mV. Thus, when penicillamine (PA) was added to the solution, these thiol-containing compounds participate in Michael type addition reactions with 4-TBC to form the corresponding thioquinone derivatives, decreasing the peak current obtained proportionally to the increase of its concentration. The highest response for PA was obtained around pH 7. This method could be used to determine PA concentration in the range 0.02-80 ?M (r = 0.998). The determination of PA was possible with a limit of detection of 7 nM, in the processing of as many as 50 samples per hour. The HRP-rotating biosensor was successfully applied to the determination of PA in pharmaceutical formulations. © 2006 Elsevier B.V. All rights reserved.

"Autonomous Microfluidic System For Phosphate Detection"
Talanta 2007 Volume 71, Issue 3 Pages 1180-1185
Christina M. McGraw, Shannon E. Stitzel, John Cleary, Conor Slater and Dermot Diamond

Abstract: Miniaturization of analytical devices through the advent of microfluidics and µtotal analysis systems is an important step forward for applications such as medical diagnostics and environmental monitoring. The development of field-deployable instruments requires that the entire system, including all necessary peripheral components, be miniaturized and packaged in a portable device. A sensor for long-term monitoring of phosphate levels has been developed that incorporates sampling, reagent and waste storage, detection, and wireless communication into a complete, miniaturized system. The device employs a low-power detection and communication system, so the entire instrument can operate autonomously for 7 days on a single rechargeable, 12 V battery. In addition, integration of a wireless communication device allows the instrument to be controlled and results to be downloaded remotely. This autonomous system has a limit of detection of 0.3 mg/L and a linear dynamic range between 0 and 20 mg/L.

"Development Of An MSFIA-MPFS Pre-treatment Method For Radium Determination In Water Samples"
Talanta 2007 Volume 71, Issue 3 Pages 1172-1179
Y. Fajardo, E. Gómez, F. Garcias, V. Cerdà and M. Casas

Abstract: A new automatic method for pre-concentration and separation of radium in water samples has been developed. Such method combines both multisyringe (MSFIA) and multi-pumping (MPFS) flow analysis techniques allowing to analyze larger sample volumes with a higher throughput than other previous methodologies. Ra adsorbed on MnO2, deposited on cotton fiber, is eluted with hydroxylamine and subsequently coprecipitated with BaSO4. 226Ra activity is determined off-line by using a low background proportional counter. The procedure yield is (90 ± 3)% and its lower limit of detection 0.05 Bq L-;1. This method has been applied satisfactorily to different types of spiked water (tap, mineral and seawater).

"Sensitive Determination Of Phenothiazines In Pharmaceutical Preparation And Biological Fluid By Flow Injection Chemiluminescence Method Using Luminol-KMnO4 System"
Talanta 2007 Volume 71, Issue 3 Pages 1124-1129
Yinhuan Li, Weifen Niu and Jiuru Lu

Abstract: A flow injection chemiluminescence method was described for the determination of four phenothiazine drugs, namely, chlorpromazine hydrochloride, perphenazine hydrochloride, fluphenazine hydrochloride and thioridazine hydrochloride. Strong Chemiluminescence (CL) signal was produced when above-mentioned drug was injected into the mixed stream of luminol with KMnO4. The linear ranges of the method were 0.0020-1.0 ?g/mL chlorpromazine hydrochloride, 0.0040-3.0 ?g/mL perphenazine hydrochloride, 0.0020-5.0 ?g/mL fluphenazine hydrochloride and 0.0050-1.0 ?g/mL thioridazine hydrochloride. The detection limits were 0.4 ng/mL chlorpromazine hydrochloride, 0.7 ng/mL perphenazine hydrochloride, 2 ng/mL fluphenazine hydrochloride and 0.7 ng/mL thioridazine hydrochloride. The proposed method was applied to the determination of chlorpromazine hydrochloride in injections and in mental patient's urine samples and the satisfactory results were achieved. The possible CL reaction mechanism was also discussed briefly. © 2006 Elsevier B.V. All rights reserved.

"A Novel Spectrophotometric Method For Batch And Flow Injection Determination Of Cyanide In Electroplating Wastewater"
Talanta 2007 Volume 71, Issue 3 Pages 1088-1095
Saad S.M. HassanCorresponding Author Contact Information, E-mail The Corresponding Author, Mohamed S.A. Hamza and Ali E. Kelany

Abstract: A sensitive and highly selective spectrophotometric method is described for the determination of cyanide. It is based on a reaction of cyanide with aquacyanocobyrinic acid heptamethyl ester (ACCbs) reagent (orange color) at pH 9.5 to give dicyanocobester (DCCbs) (violet color). The increase of the absorption bands of the reaction product at 368 and 580 nm and the decrease of the reagent band at 353 nm are linearly proportional to the cyanide concentration. The method is used in static mode for determining cyanide over the concentration range 0.04-1.20 ?g mL-1 with a detection limit of 0.02 ?g mL-1 and for hydrodynamic analysis of 0.4-5.2 ?g mL-1 cyanide. Application for batch and flow injection monitoring of cyanide in electroplating wastewater samples gives results agree within ± 1.2% with those obtained by the standard potentiometry using the cyanide ion selective electrode. The method is practically free from interferences by PO43-, NO3-, NO2-, SO42-, F-, Cl-, Br-, I-, S2- and SCN- ions and gives results with average recoveries of 97.6-99.2%. Advantages offered by using ACCbs as a chromogen for cyanide assay are: (i) high selectivity and sensitivity of the coordination site of the reagent towards cyanide ion; (ii) fast reaction, since legation takes place at the axial position of the reagent; (iii) good solubility and stability of the reagent in aqueous solutions over a wide pH range; (iv) high stability of the reagent (ACCbs) and the colored complex product (DCCbs) and (v) possible absorbance measurements at three different wavelengths. © 2006 Elsevier B.V. All rights reserved.

"Development Of A Reversed FIA System For The Spectrophotometric Determination Of Sb(III) And Total Sb In Antileishmanial Drugs"
Talanta 2007 Volume 71, Issue 3 Pages 1047-1053
Vanessa G.K. Almeida, Mônica F. Lima and Ricardo J. Cassella

Abstract: This paper reports the development of a reversed flow injection system for the spectrophotometric determination of Sb(III) and total Sb in antileishmanial drugs. The analytical system is based on the selective reaction between Sb(III) and bromopyrogallol red (BPR) with the decrease of the absorbance at 555 nm. Total Sb concentration was determined after reduction of all Sb(V) to Sb(III) with KI and ascorbic acid. The influence of system variables (chemical and flow type) and the possible interference of high amounts of Sb(V) on Sb(III) was studied as well as the suitable conditions for preparation of samples. It was verified that the use of Triton X-100 enhanced the sensitivity of the methodology and that the previous sonication of the samples was fundamental to achieve accurate results. Under optimized conditions the reversed FIA system was able to process 63 samples per hour with a detection limit of 29 ng mL-1 and a RSD of 3.8% (0.25 µg mL-1 level). Real samples of commercial antileishmanial drugs were analyzed, being observed no statistical difference between the results obtained by the developed system and FAAS or manual methodology in relation to total Sb concentration.

"An Ion-exchange Method For Speciation Of Antimony By Flow Injection Electrothermal Atomic Absorption Spectrometry"
Talanta 2007 Volume 71, Issue 2 Pages 918-922
F. Sánchez RojasCorresponding Author Contact Information, E-mail The Corresponding Author, C. Bosch Ojeda and J.M. Cano Pavón

Abstract: In this work, a simple pre-concentration system, achieved by replacing the sample tip of the autosampler arm by a micro-column packed with Amberlite IRA-910 or silica gel chelating resin functionalised with 1,5-bis(di-2-pyridyl)methylene tbiocarbohydrazide (DPTH-gel), is developed for the determination of Sb(V) and total antimony, respectively. Different factors including pH of sample solution, ionic strength, concentration and volume of eluent, sample flow rate, sample loading time and matrix effects for pre-concentration were investigated. The method has been applied to the determination of antimony species in different samples. © 2006 Elsevier B.V. All rights reserved.

"Flow-injection Chemiluminescence Determination Of Formaldehyde In Water"
Talanta 2007 Volume 71, Issue 2 Pages 900-905
Kamil Motyka, Antonije Onjia, Pavel Mikuška, Corresponding Author Contact Information, E-mail The Corresponding Author and Zbyněk Večeřa

Abstract: A modification of the Trautz-Schorigin reaction into a flow-injection analysis configuration is described. Different approaches were used at the optimization of chemiluminescence determination of formaldehyde in water based on the reaction of formaldehyde, gallic acid and hydrogen peroxide in an alkaline solution. Detection system with a 218 µL chemiluminescence cell was optimized by both a one-variable-at-a-time method, and a modified simplex method. A calibration graph is linear in the concentration range 4 x 10^-8 to 1 x 10^-5 M HCHO. The detection limit of formaldehyde for a signal-to-noise ratio of 3 is 4 x 10^-8 M. The relative standard deviations for 15 repeated measurements of 1 x 10^-6 and 5 x 10^-6 mol L-1 HCHO are 4.32 and 3.33%, respectively. The analysis time is 1.5 min. The method was applied to the determination of formaldehyde in urban rainwater. A comparison of results found by proposed method with those obtained by fluorimetric reference method provided a good agreement. © 2006 Elsevier B.V. All rights reserved.

"On-line Stripping Voltammetry Of Trace Metals At A Flow-through Bismuth-film Electrode By Means Of A Hybrid Flow-injection/sequential-injection System"
Talanta 2007 Volume 71, Issue 2 Pages 758-765
Anastasios Economou and Anastasios Voulgaropoulos

Abstract: In this work, we describe an automated stripping analyzer operating on a hybrid flow-injection/sequential-injection (FIA/SIA) mode and utilizing a bismuth-film electrode (BiFE) as a flow-through sensor for on-line stripping voltammetry of trace metals. The instrument combines the advantages of FIA and SIA and is characterized by simplicity, low-cost, rapidity, versatility and low consumption of solutions. The proposed analytical flow methodology was applied to the determination of Cd(II) and Pb(II) by anodic stripping voltammetry (ASV) and of Ni(II) and Co(II) by adsorptive stripping voltammetry (AdSV). The steps of the rather complex experimental sequence (i.e. the bismuth-film formation, the analyte accumulation, the voltammetric stripping and the electrode cleaning/regeneration) were conducted on-line and the critical parameters related to the respective analytical procedures were investigated. In ASV, for a accumulation time of 180 s the limits of detection for Cd(II) and Pb(II) were 2 and 1 ?g l-1, respectively (S/N = 3) and the relative standard deviations were 5.3% and 4.7%, respectively (n = 8). In AdSV, for a total sample volume of 1000 µL, the limits of detection for Ni(II) and Co(II) were 1 ?g L-1 (S/N = 3) and the relative standard deviations were 5.5% and 6.2%, respectively (n = 8). The measurement frequency ranged between 15 and 20 stripping cycles h-1. The results indicate that the BiFE is well suited as a flow-through detector for on-line stripping analysis and, by virtue of its low toxicity, can serve as a viable alternative to mercury-based flow-through electrodes. © 2006 Elsevier B.V. All rights reserved.

"Ultratrace Determination Of Cadmium By Cold Vapor Atomic Absorption Spectrometry After Preconcentration With A Simplified Cloud Point Extraction Methodology"
Talanta 2007 Volume 71, Issue 2 Pages 582-587
Jamshid L. ManzooriCorresponding Author Contact Information, E-mail The Corresponding Author, Hossein Abdolmohammad-Zadeh and Mohammad Amjad

Abstract: A simplified micelle-mediated extraction methodology for the pre-concentration of ultratrace levels of cadmium as a prior step to its determination by cold vapor atomic absorption spectrometry (CV-AAS) has been developed. The methodology is based on the cloud point extraction (CPE) of cadmium at pH 8 by using the non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) without adding any chelating agent. Cadmium cold vapor was generated from 2 mL of the extracted surfactant-rich phase by means of sodium tetrahydroborate (3%, w/v) as a reducing agent and hydrochloric acid (0.2 mol l-1) as a carrier solution. Several important variables that affect the cloud point extraction and cold vapor cadmium generation efficiency were investigated and optimized. The pre-concentration of only 50 mL of solution in the presence of 0.06% (v/v) PONPE 7.5 gives an enhancement factor of 62. The calibration graph using the pre-concentration system was linear in the range of 4-100 ng L-1 with a correlation coefficient of 0.9992. Detection limit (3 s) obtained in the optimal conditions was 0.56 ng l-1. The relative standard deviation (RSD) for six replicate determinations at 20 ng L-1 Cd level was 3.2%. The proposed method was successfully applied to the ultratrace determination of cadmium in water samples. © 2006 Elsevier B.V. All rights reserved.

"On-line Enrichment System For Manganese Determination In Water Samples Using FAAS"
Talanta 2007 Volume 71, Issue 1 Pages 406-410
Marta Knap, Krzysztof Kilian and Krystyna Pyrzynska

Abstract: An on-line pre-concentration procedure for the determination of manganese using flow-injection approach with flame atomic absorption spectrometry as a detection method is described. The proposed method is based on the complexation between Mn(II) and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP). Two approaches were investigated for enrichment of manganese; the formation of Mn-TCPP complex in a solution followed by its retention on a sorbent and the sorption of manganese ions onto the TCPP-modified resin. The best results was obtained for the first approach when 10^-5 M reagent was on-line mixed with an aqueous sample solution and passed through the microcolumn packed with anion-exchange resin Amberlite IRA-904 for 5 min. The sorbed complexes were then eluted with 0.5 mL of 2 M HNO3. A good precision (2.2-3.1% RSD for 50 ?g L-1 manganese) and the enrichment factor of 30 were obtained with the detection limit of 12 ?g L-1 for 5 min loading time. The interference of anions and cations has been studied to optimize the conditions and the method was applied for determination of manganese in natural water samples. The results obtained by FI-FAAS and ETAAS (as a reference method) were not statistically different for a significance level of 0.05. © 2006 Elsevier B.V. All rights reserved.

"Development Of A Long-life Capillary Enzyme Bioreactor For The Determination Of Blood Glucose"
Talanta 2007 Volume 71, Issue 1 Pages 391-396
Ja-an Annie Ho, Li-chen Wu, Nien-Chu Fan, Ming-Shih Lee, Hung-Yi Kuo and Chung-Shi Yang

Abstract: A long-life capillary enzyme bioreactor was developed that determines glucose concentrations with high sensitivity and better stability than previous systems. The bioreactor was constructed by immobilizing glucose oxidase (GOx) onto the inner surface of a 0.53 mm i.d. fused-silica capillary that was part of a continuous-flow system. In the presence of oxygen, GOx converts glucose to gluconic acid and hydrogen peroxide (H2O2). Hydrogen peroxide detection was accomplished using an amperometric electrochemical detector. The integration of this capillary reactor into a flow-injection (FIA) system offered a larger surface-to-volume ratio, reduced band-broadening effects, and reduced reagent consumption compared to packed column in FIA or other settings. To obtain operational (at ambient temp) and storage (at 4°C) stability for 20 weeks, the glucose biosensing system was prepared using an optimal GOx concentration (200 mg/mL). This exhibited an FIA peak response of 7 min and a detection limit of 10 µM (S/N = 3) with excellent reproducibility (coefficient of variation, CV < 0.75%). It also had a linear working range from 101 to 104 µM. The enzyme activity in this proposed capillary enzyme reactor was well maintained for 20 weeks. Furthermore, 20 serum samples were analyzed using this system, and these correlated favorably (correlation coefficient, r2 = 0.935) with results for the same samples obtained using a routine clinical method. The resulting biosensing system exhibited characteristics that make it suitable for in vivo application.

"Application Of Manganese(IV) Dioxide Microcolumn For Determination And Speciation Of Nitrite And Nitrate Using A Flow Injection Analysis-flame Atomic Absorption Spectrometry System"
Talanta 2007 Volume 71, Issue 1 Pages 359-364
Meissam Noroozifar, Mozhgan Khorasani-Motlagh, Aboozar Taheri and Marjan Homayoonfard

Abstract: A flow injection (FI) method with flame atomic absorption spectrometry (FAAS) detection was developed for the determination and speciation of nitrite and nitrate in foodstuffs and wastewaters. The method is based on the oxidation of nitrite to nitrate using a manganese(IV) dioxide oxidant microcolumn where the flow of the sample through the microcolumn reduces the MnO2 solid phase reagent to Mn(II), which is measured by FAAS. The absorbance of Mn(II) are proportional to the concentration of nitrite in the samples. The injected sample volume was 400 µL with a sampling rate of analyzes was 90 h-1 with a relative standard deviation better than 1.0% in a repeatability study. Nitrate is reduced to nitrite in proposed FI-FAAS system using a copperized cadmium microcolumn and analyzed as nitrite. The calibration curves were linear up to 20 mg L-1 and 30 mg L-1 with a detection limit of 0.07 mg L-1 and 0.14 mg L-1 for nitrite and nitrate, respectively. The results exhibit no interference from the presence of large amounts of ions. The method was successfully applied to the speciation of nitrite and nitrate in spiked natural water, wastewater and foodstuff samples. The precision and accuracy of the proposed method were comparable to those of the reference spectrophotometric method.

"Chemiluminometric Determination Of The Pesticide 3-indolyl Acetic Acid By A Flow Injection Analysis Assembly"
Talanta 2007 Volume 71, Issue 1 Pages 318-323
A.I. Pimentel Neves, J.R. Albert-Garc&iacute;a and J. Mart&iacute;nez Calatayud

Abstract: A new method is proposed for the chemiluminescent determination of the pesticide 3-indolyl acetic acid by means of an flow injection analysis system. The chemiluminescence emission is obtained by oxidation of the analyte with Ce (IV) in nitric acid and presence of β-cyclodextrine.The continuous-flow method allows the determination of 159 samples h-1 of 3-indolyl acetic acid in an interval of concentrations over the range 0.5-15.0 mg l-1. The limit of detection was 0.1 µg L-1 and the RSD (n, 17) at 2.0 mg L-1 of the pesticide level was 2.7%. The method was applied to water samples.

"A Novel Method For Flow Injection Analysis Of Total Antioxidant Capacity Using Enzymatically Produced ABTS+ And Biamperometric Detector Containing Interdigitated Electrode"
Talanta 2007 Volume 71, Issue 1 Pages 213-220
Stjepan Milardovic, Irena Kerekovi&#263;, Romano Derrico and Vlatko Rumenjak

Abstract: Application of interdigitated array microelectrodes as electrochemical sensors for determination of antioxidant capacity is reported. Electrochemical measurements with interdigitated electrodes (IDE) were studied in both stationary solutions and the flow system. The method is based on biamperometric measurements using ABTS+|ABTS redox couple in phosphate buffer solution, pH 7.40. During analysis, the ABTS radical cation was enzymatically produced by peroxidase in a tubular flow-through reactor. The performance of bioreactor was tested at different concentrations of immobilized enzyme, ABTS and hydrogen peroxide. The influence of flow rate on proper operation of the bioreactor was also studied. The results of antioxidant activity were determined using Trolox as a standard. The applied IDE detector accomplished good sensitivity of 0.3 nA/µM of Trolox and offered linear range between 20 to 500 µM of Trolox.The comparison of results (R2 = 0.9915) for antioxidant activity between spectroscopic and FIA biamperometric measurements by interdigitated electrodes confirmed the applicability of the proposed method for determination of antioxidant capacity.

"Potentiometric Measurements In Sequential Injection Analysis Lab-on-valve (SIA-LOV) Flow-system"
Talanta 2007 Volume 71, Issue 1 Pages 160-164
Timo Kikas and Ari Ivaska

Abstract: Advantages of using sequential injection analysis lab-on-valve (SIA-LOV) in potentiometric measurements are studied with Ca2+ sensitive solid-contact ion-selective electrodes (SC-ISE) and pH electrode based on polyaniline (PANI). Experiments show that Ca2+-SC-ISE requires a stopped flow mode to be used in order to get longer equilibration time. On the other hand, PANI based pH electrode gives better results under flow conditions. SIA-LOV was found to be a flexible solution handling system for potentiometric measurements. The technique gives a possibility to fine-tune the calibration range or even recondition the electrode before every measurement without losing in linear range of calibration. © 2006 Elsevier B.V. All rights reserved.

"Separation And Determination Of Alpinetin And Cardamonin In Alpinia Katsumadai Hayata By Flow Injection-micellar Electrokinetic Chromatography"
Talanta 2007 Volume 71, Issue 1 Pages 155-159
Lihong Liu, Xingguo ChenCorresponding Author Contact Information, E-mail The Corresponding Author and Zhide Hu

Abstract: A simple, rapid, and accurate method for the separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata was developed by combination of flow injection (FI)-micellar electrokinetic chromatography (MEKC) for the first time. The analysis was carried out using an unmodified fused-silica capillary (50 ?m i.d.; total length 13.6 cm; effective length 10.3 cm) and direct ultraviolet (UV) detection at 214 nm. The sample throughput was 11-24 samples per hour using the background electrolyte (BGE) containing 4 mM sodium borate-8 mM NaH2PO4 (pH 8.1)-8 mM sodium dodecyl sulfate (SDS)-19% (v/v) ethanol. The repeatabilities (n = 4) reached relative standard deviation values (RSD) of 3.0% and 2.5% for the peak areas and 2.5% and 3.1% for peak heights of alpinetin and cardamonin, respectively. Regression equations revealed linear relationships (r2: 0.9993-0.9994) between the peak area of each analyte and the concentration. Recoveries were in the range 90-92% and 99-105% for alpinetin and cardamonin, respectively. © 2006 Elsevier B.V. All rights reserved.

"Determination Of Proteins By Flow Injection Analysis Coupled With The Rayleigh Light Scattering Technique"
Talanta 2007 Volume 71, Issue 1 Pages 109-114
Ying Li, Lijun Dong, Yaheng Zhang, Zhide Hu and Xingguo Chen

Abstract: A novel flow injection analysis (FIA) method with Rayleigh light scattering (RLS) detection was developed for the determination of protein concentrations. This method is based on the weak intensity of RLS of p-nitrohenzene-azo-3,6 disulfo-1-amino-8-naphthol-7-azo-benzene disodium salt (Amide Black-10B) which can be enhanced by addition of protein in weakly acidic solution. It has proved that the application of this method to quantify the proteins by using human serum albumin was available in real samples. In addition, this method is very sensitive (the determination limits are 0.11 µg/mL for human serum albumen (HSA) and 0.85 µg/mL for bovine serum albumen, BSA), simple, rapid and tolerance of most interfering substances. The FIA-RLS method was more stabile than the general RLS method and the average RSD value of FIA-RLS less than general RLS. The effects of different interfering substances will be also examined. The amount of proteins in human serum sample was determined and the maximum relative error was no more than 3.00% as well as the recovery was between 94.9 and 105.9%.

"Flow Injection Determination Of Thyroxine In Pharmaceutical Preparations Using Tris(2,2′-bipyridyl)ruthenium(III)-NADH Chemiluminescence Detection"
Talanta 2007 Volume 71, Issue 1 Pages 56-61
Amir Waseem, Mohammad Yaqoob and Abdul Nabi

Abstract: A flow injection (FI) method is reported for the determination of thyroxine based on its enhancement of chemiluminescence (CL) from the Ru(bpy)33+-NADH system. The calibration graph was linear over the range 2.0^-10 x 10^-8 mol L-1 (r2 = 0.9989) with relative standard deviations (RSD) in the range 2.0-4.5% (n = 4). The limit of detection (3σ blank) was 1.0 x 10^-9 mol L-1 with sample throughput of 120 h-1. The effect of some organic compounds, anions and cations were studied for l-thyroxine determination. The method was applied to pharmaceutical preparations and the results obtained were in reasonable agreement with the amount labeled. The method was statistically compared with the results obtained by RIA; no significant disagreement at 95% confidence limit was observed. A calibration graph of NADH over the range 1.3 x 10^-8 - 1.3 x 10^-6 mol L-1 was also established (r2 = 0.9992) with RSD in the range 1.0-3.5% (n = 4). The limit of detection (3σ) was 1.0 x 10^-10 mol L-1 NADH.

"Photolytic Oxidation Of As Species For Determination Of Total As (including The 'hidden' As Fraction) In Coastal Seawater By Hydride Generation-atomic Fluorescence Spectrometry"
Talanta 2007 Volume 71, Issue 1 Pages 51-55
E. Castro, I. Lavilla and C. Bendicho

Abstract: Ultraviolet irradiation (photolysis) in alkaline medium was applied for pretreatment of seawater samples so as to accurately determine total As by continuous-flow hydride generation-atomic fluorescence spectrometry. This sample pretreatment is meant to convert non-reducible As forms into inorganic As, which easily forms arsine. The optimized parameters were the treatment time and the pH of the medium. The behavior of four hydride-reactive As species [As(III), As(V), MMA, DMA], and AsB, i.e. a typical non-hydride-reactive As species, when subjected to UV irradiation was studied. UV irradiation at pH 1 lead to conversion of all species into As(V) with the exception of AsB and DMA. Conversions of DMA and AsB into As(V) at pH 11 in less than 30 min were observed under UV irradiation. The limit of detection of As (measured as As(V)) by hydride generation-atomic fluorescence spectrometry was 0.1 ?g/L and the repeatability of the oxidation procedure was about 10%. The method was applied to determination of total and directly reducible As at 11 sampling points of the Galician Coast (Atlantic Ocean, Spain). Total As concentrations were in the range 1.4-4.8 ?g/L. A significant As fraction, between 20 and 44%, depending on the sampling point, corresponded to non-reducible As which was converted by UV irradiation into hydride-reactive As. This fraction should represent the sum of DMA, which yields a low sensitivity in the continuous flow-AFS system, and the hidden As fraction. © 2006 Elsevier B.V. All rights reserved.

"Sequential Injection Analyzer For Glycerol Monitoring In Yeast Cultivation Medium"
Talanta 2006 Volume 71, Issue 2 Pages 941-947
Burkhard Horstkotte, Elisabeth Werner, Ali Kazemi Seresht, Gesine Cornelissen, Olaf Elsholz, V&iacute;ctor Cerd&agrave; Mart&iacute;n and Reiner Luttmann

Abstract: A smart and versatile flow system for the at-line monitoring of glycerol based on sequential injection analysis is proposed. Formaldehyde, generated by oxidation of glycerol with sodium periodate, is transformed into 2,4-diacetyl-1,4-dihydrolutidine applying the Hantzsch condensation reaction with acetylacetone and ammonium. Dual-wavelength detection was carried out to minimize the contribution of the schlieren effect using a single blue LED. In-line sample dilution is accomplished applying the concept of zone-penetration and a new concept of sample splitting. Under optimized physical and chemical variables, regression curves over two dynamic working ranges of 0.1-4 and 1-40 g L-1 were attained. The injection throughputs were 14 and 12 h-1, respectively. Applying on-line data evaluation and conditional inquiries, the smart and independent selection of the adequate analytical procedure for the required working range was accomplished. The system was successfully applied to the at-line monitoring of glycerol in a continuous, cell-free medium flow from a yeast cultivation process during batch and fed-batch phase with glycerol as the only carbon source.

"Determination Of Trace Elements In Natural Waters By Inductively Coupled Plasma Time Of Flight Mass Spectrometry After Flow Injection Preconcentration In A Knotted Reactor"
Talanta 2006 Volume 71, Issue 1 Pages 44-50
Boryana Dimitrova-Koleva, Karima Benkhedda, Elisaveta Ivanova and Freddy Adams

Abstract: A flow injection on-line sorption system was developed for the separation and pre-concentration of traces of Ag, Cd, Co, Ni, Pb, U and Y from natural water samples with subsequent detection by ICP TOF MS. Simultaneous pre-concentration of the analytes was achieved by complexation with the chelating reagent 1-phenyl-3-methyl-4-benzoylpyrazol-5-one immobilized on the inner walls of a (200 cm x 0.5 mm) PTFE knotted reactor. The analytes were eluted and transported to an axial ICP TOF MS system with 1% (v/v) HNO3 containing 0.3 µg L-1 of Rh as an internal standard using ultrasonic nebulization. The detection limits (3σ) varied from 0.3 ng L-1 for Y to 15.2 ng L-1 for Ni and the precision (RSD) was better than 4%. Using a loading time of 90 s and a sample flow rate of 4.5 mL min-1, enhancement factors of 3-14 were obtained for the different analytes in comparison with their direct determination by ICP TOF MS with ultrasonic nebulization without pre-concentration. The accuracy of the method was demonstrated by analysis of water based certified reference materials.

"On-line Sample Treatment And FT-IR Determination Of Doxylamine Succinate In Pharmaceuticals"
Talanta 2006 Volume 70, Issue 5 Pages 1100-1106
Josep F. Ventura-Gayete, Miguel de la Guardia and Salvador Garrigues

Abstract: A low solvent consumption method for Fourier transform infrared spectroscopy (FT-IR) determination of doxylamine succinate in pharmaceuticals has been developed. The analyte was continuous and selectively extracted with a 13% (v/v) ethanol:chloroform solvent mixture, recirculating the solvent through the sample and monitoring the process by FT-IR. Doxylamine succinate was determined by on-line standard addition measuring the peak area in the regions 1730-1710 and 1485-1462 cm-1 corrected with a two-point baseline established between 2000 and 1800 cm-1. This new method implies low volumes of chloroformic solvent mixture, only 2.6 mL per sample, in front of classical batch FT-IR methods, improving analytical efficiency and reducing waste generation. The on-line extraction and standard addition determination of doxylamine succinate allowed a throughput of 10 h-1.

"Automated On-line Separation Preconcentration System For Palladium Determination By Graphite Furnace Atomic Absorption Spectrometry And Its Application To Palladium Determination In Environmental And Food Samples"
Talanta 2006 Volume 70, Issue 5 Pages 979-983
F. S&aacute;nchez Rojas, C. Bosch Ojeda and J.M. Cano Pav&oacute;n

Abstract: A flow injection (FI) system was used to develop an efficient on-line sorbent extraction pre-concentration system for palladium by graphite furnace atomic absorption spectrometry (GFAAS). The investigated metal was pre-concentrated on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The palladium is eluted with 40 µL of HCl 4 M and directly introduced into the graphite furnace. The detection limit for palladium under the optimum conditions was 0.4 ng mL-1. This procedure was employed to determine palladium in different samples. © 2006 Elsevier B.V. All rights reserved.

"Kinetic Determination Of Cysteine On Flow Injection System By Utilizing Catalytic Complexation Reaction Of Cu(II) With 5,10,15,20-tetrakis (4-N-trimethylammino-phenyl) Porphyrin"
Talanta 2006 Volume 70, Issue 4 Pages 791-796
Jianhua Liu and Jun-ichi Itoh

Abstract: A kinetic method for the determination of cysteine on flow injection system is described. Cysteine was found as a catalyst for the complexation reaction of Cu(II) with an ultra sensitive colorimetric reagent of 5,10,15,20-tetrakis (4-N-trimethylammino-phenyl) porphyrin (TTMAPP) ( = 4.8 x 105 cm-1 M-1 at 433 nm), which was used as the indicator reaction in this paper. Soret band of either the porphyrin or the produced complex ( = 4.6 x 105 cm-1 M-1 at 411 nm) can be used for detection. The continuous flow injection system greatly enhanced the analytic precision and efficiency of the kinetic method, giving a relative standard deviation of 0.73% for a 0.1 µg mL-1 cysteine with 10 injections at a throughput of 30 h-1. The detection limits (3S/N) in this case was 15 ng mL-1 and the working dynamic range was over 25 ng mL-1 to 1 µg mL-1. Sugars, organic acids and amino acids that are possible in coexistence with cysteine could be tolerated at high concentrations. This method was critically compared with the Ellman's reagent in the determinations of cysteine contents of three pharmaceutical injections for hepatic diseases and one permanent wave agent and showed better applicability in the respect of matrix interferences.

"The Development Of Sequential Injection Analysis Coupled With Lab-on-valve For Copper Determination"
Talanta 2006 Volume 70, Issue 3 Pages 656-660
Tapparath Leelasattarathkul, Saisunee Liawruangrath, Mongkon Rayanakorn, Winai Oungpipat and Boonsom Liawruangrath

Abstract: A sequential injection analysis (SIA) using lab-on-valve with air segmentation and spectrophotometric detection was designed for copper(II) determination. It is based on the reaction of copper(II) and 2-carboxy-2'-hydroxy-5'-sulfoformazyl benzene (Zincon) in a weak alkaline solution between the air zones. Beer\'s Law was obeyed over the range of 0.1-2.0 mg L-1 copper(II) with a correlation coefficient 0.9985 and a slope of 0.2893 absorbance unit/mg L-1. The relative standard deviation was 2.0% for a series of 10 measurements of 0.5 mg L-1 copper(II) solution. The detection limit (3 S/N) and the limit of quantification (LOQ) were 0.05 and 0.17 mg L-1 respectively. This method has been successfully applied to determination of copper(II) in wastewater with a sample throughput of 120 h-1. The method is superior to the batchwise method in that it provides fully automation, rapidity, less reagents and sample consumption with little waste generation.

"Flow Injection On-line Solid Phase Extractive Preconcentration Of Palladium(II) In Dust And Rock Samples Using Exfoliated Graphite Packed Microcolumns And Determination By Flame Atomic Absorption Spectrometry"
Talanta 2006 Volume 70, Issue 2 Pages 437-443
R.S. Praveen, S. Daniel, T. Prasada Rao, S. Sampath and K. Sreenivasa Rao

Abstract: A sensitive and efficient flow injection pre-concentration and matrix-separation technique using exfoliated graphite (EG) as column material was developed prior to flame atomic absorption spectrometry (FAAS) determination of palladium(II) in street/fan blade dust and rock samples. The method is based on the sorption of palladium(II)-diethylammonium dithiocarbamate chelate (which was found to be better among various thioligands) complex on to EG material and its subsequent elution with acidified methanol (0.01 M HCl in methanol). Using 8 mL of the sample, the detection limit achieved was 1.0 µg l-1. The accuracy of the method developed was checked by analyzing certified reference material SARM-7. The precision obtained for five successive determination of 100 µg L-1 of palladium(II) was 2.4%. The performance of EG material was compared with allotropes of carbon in terms of pH, chelate concentration, weight of column material, sensitivity enhancement (w.r.t. conventional FAAS), detection limit, calibration range, selectivity and precision. Furthermore, performance of the EG material packed column was compared with commercially available C18 bonded silica gel/alumina columns for on-line FIA-FAAS determination of palladium(II).

"Fast Simultaneous Spectrophotometric Determination Of Naphazoline Nitrate And Methylparaben By Sequential Injection Chromatography"
Talanta 2006 Volume 70, Issue 2 Pages 408-413
Petr Chocholou&#353;, Dalibor &Scaron;at&iacute;nsk&yacute; and Petr Solich

Abstract: Fast simultaneous determination of naphazoline nitrate and methylparaben in pharmaceuticals using separation method based on a novel reversed-phase sequential injection chromatography (SIC) is described in this contribution as an alternative to classical HPLC. A Chromolith™ Flash RP-18e (25 mm x 4.6 mm) column (Merck®, Germany) and a FIAlab® 3000 system (USA) with a six-port selection valve and 5.0 mL syringe pump were used for sequential injection chromatographic separations in our study. The mobile phase used was methanol/water (40:65, v/v), pH 5.2 adjusted with triethylamine 0.8 µl mL-1 and acetic acid, at flow rate 0.9 mL min-1. UV detection provided by DAD detector and two wavelengths were simultaneously monitored for increasing sensitivity of determination. Detector was set up at 220 nm for naphazoline nitrate and 256 nm for methylparaben and ethylparaben (IS). There is no necessity to use pre-adjustment of sample of nasal drops (only dilution with mobile phase) so the time of the whole analysis is very short. The validation parameters have shown good results: linearity of determination for both components (naphazoline nitrate and methylparaben), correlation coefficient >0.999; repeatability of determination (RSD) in the range 0.5-1.6% at three different concentration levels, detection limits 0.02 µg mL-1 (naphazoline nitrate) and 0.20 µg mL-1 (methylparaben and ethylparaben), and recovery from the pharmaceutical preparations in the range 100.06-102.55%. The chromatographic resolution between peaks of compounds was more than 4.0 and analysis time was less than 4 min under the optimal conditions. The advantages and drawbacks of SIC against classical HPLC are discussed showing that SIC can be an advantageous alternative in many cases.

"Multienzymatic-rotating Biosensor For Total Cholesterol Determination In A FIA System"
Talanta 2006 Volume 70, Issue 2 Pages 244-250
Eloy Salinas, Valeria Rivero, Angel A.J. Torriero, Delia Benuzzi, Mar&iacute;a I. Sanz and Julio Raba

Abstract: Fabrication of an amperometric-rotating biosensor for the enzymatic determination of cholesterol is reported. The assay utilizes a combination of three enzymes: cholesterol esterase (ChE), cholesterol oxidase (ChOx) and peroxidase (HRP); which were co-immobilizing on a rotatory disk. The method is developed by the use of a glassy carbon electrode as detector versus Ag/AgCl/3 M NaCl in conjunction with a soluble-redox mediator 4-tert-butylcatechol (TBC). ChE converts esterified cholesterol to free cholesterol, which is then oxidized by ChOx with hydrogen peroxide as product. TBC is converted to 4-tert-butylbenzoquinone (TBB) by hydrogen peroxide, catalyzed by HRP, and the glassy carbon electrode responds to the TBB concentration. The system has integrated a µpacked-column with immobilized ascorbate oxidase (AAOx) that works as prereactor to eliminate l-ascorbic acid (AA) interference. This method could be used to determine total cholesterol concentration in the range 1.2 µM-1 mM (r = 0.999). A fast response time of 2 min has been observed with this amperometric-rotating biosensor. Lifetime is up to 25 days of use. The calculated detection limits was 11.9 nM. Reproducibility assays were made using repetitive standards solutions (n = 5) and the percentage standard error was less than 4%.

"A Flow-injection Chemiluminescence Method For The Determination Of Some Estrogens By Enhancement Of Luminol-hydrogen Peroxide-tetrasulfonated Manganese Phthalocyanine Reaction"
Talanta 2006 Volume 70, Issue 1 Pages 219-224
Lun Wang, Ping Yang, Yongxin Li and Changqin Zhu

Abstract: A novel flow-injection chemiluminescence (FI-CL) method for the determination of estrogens is proposed, based upon its enhancing effect on the CL reaction of luminol with hydrogen peroxide catalyzed by tetrasulfonated manganese phthalocyanine (MnTSPc) in alkaline solution. Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentration of estrone in the range of 1.0 x 10^-7 to 1.0 x 10^-6 mol/l, estradiol in the range of 9.0 x 10^-8 to 1.0 x 10^-6 mol/l and estriol in the range of 3.0 x 10^-7 to 2.0 x 10^-6 mol/l, respectively. The detection limits were 5.1 x 10^-8 mol/l for estrone, 7.2 x 10^-9 mol/l for estradiol and 6.5 x 10^-8 mol/l for estriol with a relative standard deviation of 2.8% for 5.0 x 10^-7 mol/l estrone, 2.4% for 1.0 x 10^-7 mol/l estradiol, and 3.1% for 7.0 x 10^-7 mol/l estriol (n = 11). This method has been applied to the determination of estrogen in pharmaceutical injections and tap water with satisfactory results. © 2006 Elsevier B.V. All rights reserved.

"A Simple And Sensitive Chromium Speciation Procedure By Hyphenating Flow Injection On-line Preconcentration With Catalytic Spectrophotometry"
Talanta 2006 Volume 70, Issue 1 Pages 139-145
Han Cui, Ronghuan He and Jianhua Wang

Abstract: A high sensitive chromium speciation procedure based on spectrophotometric detection was developed by coupling flow injection on-line pre-concentration with a catalytic indicator reaction. Chromium(VI) is retained on a mini-column packed with polystyrene anion exchange resin (strong basic 717 resin), which was afterwards eluted with a small volume of NaNO3 solution. The eluted Cr(VI) is then directed to catalyze the decoloration of alizarin cyanine green (ACG) in the presence of bromate as oxidizing reagent, and the absorbance change is proportional to the concentration of Cr(VI). With a sampling volume of 12 mL and a loading time of 120 s, an enrichment factor of 26.5 was achieved for the pre-concentration. The most distinct feature of this procedure is characterized by its overall detection limit, i.e., 50 ng l-1, which is much superior to those achieved by FAAS, and comparable to those obtained by inductively coupled plasma mass spectrometry (ICPMS) and electrothermal atomic absorption spectrometry (ETAAS). The procedure was validated with a certified reference material. It was also applied to the speciation of chromium in a series of surface water samples. © 2006 Elsevier B.V. All rights reserved.

"The Development Of Iodide-based Methods For Batch And On-line Determinations Of Phosphite In Aqueous Samples"
Talanta 2006 Volume 69, Issue 5 Pages 1292-1299
Roman A. Barco, Deepa G. Patil, Weihong Xu, Lin Ke, Crist S. Khachikian, Grady Hanrahan and Tina M. Salmassi

Abstract: Recent developments in the field of microbiology and research on the origin of life have suggested a possible significant role for reduced, inorganic forms of phosphorus (P) such as phosphite [HPO32-, P(+III)] and hypophosphite [H2PO2-, P(+I)] in the biogeochemical cycling of P. New, robust methods are required for the detection of reduced P compounds in order to confirm the importance of these species in the overall cycling of P in the environment. To this end, we have developed new batch and flow injection (FI) methods for the determination of P(+III) in aqueous solutions. The batch method is based on the reaction of P(+III) with a mixed-iodide solution containing tri-iodide (I3-) and penta-iodide (I5-). The oxidation of P(+III) consumes free I3- and I5- in solution. The remaining I3- and I5- subunits are then allowed to react with the amylose content in starch to form a blue complex, which has a λmax of 580 nm. The measurement of this blue complex is directly correlated with the concentration of P(+III). The on-line FI method employs the same reaction between P(+III) and mixed-iodide producing phosphate [P(+V)] that is determined spectrophotometrically by the molybdenum blue method employing ascorbic acid at a λmax of 710 nm. The linear range for both the batch and FI determination of P(+III) was 1.0-50 µM with detection limits of 0.70 and 0.36 µM, respectively. Interference studies for the batch method show that arsenite [As(+III)] and sulfite [S(+IV)] can also be determined by this technique; however, these interferences can be circumvented by oxidizing As(+III) and S(+IV) using KMnO4 which is an ineffective oxidant for P(+III). Both methods were applied to P(+III) determinations in ultra-pure water and simulated creek water. Results and analytical figures of merit are reported and future work is considered.

"Peroxidase Immobilized On Amberlite IRA-743 Resin For On-line Spectrophotometric Detection Of Hydrogen Peroxide In Rainwater"
Talanta 2006 Volume 69, Issue 5 Pages 1208-1214
Renato Camargo Matos, Eunice Oliveira Coelho, Cabrini Ferraz de Souza, Felipo Amaral Guedes and Maria Auxiliadora Costa Matos

Abstract: The importance of atmospheric hydrogen peroxide (H2O2) in the oxidation of SO2 and other compounds has been well established. A spectrophotometric method for the determination of hydrogen peroxide in rainwater is proposed. This method is based on selective oxidation of hydrogen peroxide using an on-line tubular reactor containing peroxidase immobilized on Amberlite IRA-743 resin. The hydrogen peroxide in the presence of phenol, 4-aminoantipyrine and peroxidase, produces a red compound (? = 505 nm). Beer's law is obeyed in a concentration range of 1-100 ?mol L-1 hydrogen peroxide with an excellent correlation coefficient (r = 0.9991), at pH 7.0, with a relative standard deviation (RSD) <2%. The detection limit of the method is 0.7 ?mol L-1 (4.8 ng of H2O2 in a 200 µL sample). Measurements of hydrogen peroxide in rain samples were carried out over the period from November 2003 to January 2005, in the central area of the Juiz de Fora city, Brazil. The concentration of H2O2 varied from values lower than the detection limit to 92.5 ?mol l-1. The effects of the presence of nonseasalt (NSS) SO42-, NO3- and H+ in the concentration of hydrogen peroxide in the rainwater had been evaluated. The average concentrations of H2O2, NO3-, NSS SO42- and SO42- are 23.4, 18.9, 7.9 and 10.3 ?mol l-1, respectively. The pH values for 82% of the collected samples are greater than 5.0. The spectrophotometeric method developed in this work that uses enzyme immobilized on the resin ion-exchange compared with the amperometric method did not present any significant difference in the results. © 2006 Elsevier B.V. All rights reserved.

"Flow Injection Hydride Generation Electrothermal Atomic Absorption Spectrometric Determination Of Toxicologically Relevant Arsenic In Urine"
Talanta 2006 Volume 69, Issue 5 Pages 1112-1117
Panayot K. Petrov, Ivan Serafimovski, Trajce Stafilov and Dimiter L. Tsalev

Abstract: Analytical procedure for the determination of toxicologically relevant arsenic (the sum of arsenite, arsenate, monomethylarsonate and dimethylarsinate) in urine by flow injection hydride generation and collection of generated inorganic and methylated hydrides on an integrated platform of a transverse-heated graphite atomizer for electrothermal atomic absorption spectrometric determination (ETAAS) is elaborated. Platforms are pre-treated with 2.7 µmol of zirconium and then with 0.10 µmol of iridium which serve both as an efficient hydride sequestration medium and permanent chemical modifier. Arsine, monomethylarsine and dimethylarsine are generated from diluted urine samples (10-25-fold) in the presence of 50 mmol L-;1 hydrochloric acid and 70 mmol L-;1 l-cysteine. Collection, pyrolysis and atomization temperatures are 450, 500, 2100 and 2150°C, respectively. The characteristic mass, characteristic concentration and limit of detection (3s) are 39 pg, 0.078 µg L-;1 and 0.038 µg L-;1 As, respectively. The limits of detection in urine are ~0.4 and 1 µg L-;1 with 10- and 25-fold dilutions. The sample throughput rate is 25 h-;1. Applications to several urine CRMs are given.

"Microchip Flow-injection Analysis Of Trace 2,4,6-trinitrotoluene (TNT) Using Mercury-amalgam Electrochemical Detector"
Talanta 2006 Volume 69, Issue 4 Pages 984-987
Joseph Wang and Martin Pumera

Abstract: This paper reports on a microfluidic device for the flow-injection/electrochemistry analysis of nitroaromatic explosive. The response is very fast (150 assays/h), highly sensitive (detection limit 7.0 ?g L-1), reproducible and stable (RSD = 2.0%; n = 30) and linear (over 20-100 ?g L-1 range). Relevant experimental parameters have been optimized. The new microsystem offers great promise for on-site monitoring of TNT, with significant advantages of speed/warning, sample size, efficiency and cost. Most favorable S/N characteristics were obtained at the Hg/Au-amalgam end-channel detector. © 2005 Elsevier B.V. All rights reserved.

"Flow Injection Chemiluminescence Determination Of Paracetamol"
Talanta 2006 Volume 69, Issue 4 Pages 976-983
Wirat Ruengsitagoon, Saisunee Liawruangrath and Alan Townshend

Abstract: A simple chemiluminometric method using flow injection has been developed for the determination of paracetamol (acetaminophen), based on the chemiluminescence produced by the reduction of tris(2,2'-bipyridyl)ruthenium(III). The latter is obtained by oxidation of tris(2,2'-bipyridyl)ruthenium(II) by potassium permanganate in dilute sulphuric acid in the presence of paracetamol. A standard or sample solution was injected into the ruthenium(II) stream (flow rate 1.5 mL min-1) which was then merged with potassium permanganate in dilute sulphuric acid stream (flow rate 0.5 mL min-1). The chemiluminescence intensity is enhanced by the presence of manganese(II) ions. Under the optimum conditions, a linear calibration graph was obtained over the range of 0.3-50.0 µg mL-1 and the detection limit was 0.2 µg mL-1 (s/n = 3). The relative standard deviation of the proposed method calculated from 20 replicate injections of 5.0 µg mL-1 paracetamol was 1.1%. The sample throughput was 90 h-1. The method was successfully applied to the determination of paracetamol in commercial pharmaceutical formulations.

"An Improved Flow-injection System For Spectrophotometric Determination Of Molybdenum And Tungsten In Tool Steels"
Talanta 2006 Volume 69, Issue 4 Pages 927-931
Ana P.G. Gervasio, Paula R. Fortes, Silvia R.P. Meneses, Carlos E.S. Miranda and Elias A.G. Zagatto

Abstract: A flow-injection procedure for simultaneous spectrophotometric determination of tungsten and molybdenum in steel alloys is proposed. The method exploits the catalytic effects of Mo(VI) and W(VI) on the rate of iodide oxidation by hydrogen peroxide under acidic conditions. A novel strategy for ion-exchange separation of the potential interfering species is proposed, and an AG50W-X8 cationic resin mini-column is used. The sample is injected twice, originating two sequential plugs, citrate being added to one of them in order to suppress the W(VI) catalytic activity thus providing the kinetic discrimination. The system handles 70 samples per hour and requires 1.6 mg KI per determination. A linear response is verified up to 10 mg L-1 Mo (or W) in the injectate, and signal additivity is 98-103%. Results are precise (RSD < 0.04) and in agreement with ICP-OES. Running a standard reference material (IPT-50) assessed also accuracy. © 2005 Elsevier B.V. All rights reserved.

"Flow Injection Spectrophotometric Determination Of Andrographolide From Andrographis Paniculata"
Talanta 2006 Volume 69, Issue 4 Pages 900-905
Wirat RuengsitagoonCorresponding Author Contact Information, E-mail The Corresponding Author, Kunnatee Anuntakarun and Chantana Aromdee

Abstract: A simple flow injection colorimetric procedure for determining andrographolide was proposed. It is based on the reaction between andrographolide with 3,5-dinitrobenzoic acid, resulting in an intense purplish red complex with a suitable absorption at 536 nm. A standard or sample solution was injected into the 3,5-dinitrobenzoic acid stream (flow rate of 1.0 mL min-1) which was then merged with potassium hydroxide stream with the same flow rate. Optimum conditions for determining andrographolide were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 5.0-150.0 ?g mL-1 and the detection limit was 1.50 ?g mL-1 (3?). The relatives standard deviation of the proposed method calculated from 10 replicate injections of 10.0 and 80.0 ?g mL-1 andrographolide were 0.66% and 1.64%, respectively. The sample throughput was 50 h-1. The proposed method has been satisfactorily applied to the determination of andrographolide in herb plant samples. © 2005 Elsevier B.V. All rights reserved.

"Arsenic Speciation In Freshwater Organisms From The River Danube In Hungary"
Talanta 2006 Volume 69, Issue 4 Pages 856-865
Richard Schaeffer, Kevin A. Francesconi, Norbert Kienzl, Csilla Soeroes, P&eacute;ter Fodor, L&aacute;szl&oacute; V&aacute;radi, Reingard Raml, Walter Goessler and Doris Kuehnelt

Abstract: Total arsenic and arsenic species were determined in a range of freshwater samples (sediment, water, algae, plants, sponge, mussels, frog and fish species), collected in June 2004 from the river Danube in Hungary. Total arsenic concentrations were measured by ICPMS and arsenic species were measured in aqueous extracts of the samples by ion-exchange HPLC-ICPMS. In order to separately determine the efficiency of the extraction method and the column recovery, total arsenic concentrations in the extracts were obtained in three ways: (i) ICPMS determination after acid digestion; (ii) flow injection analysis performed directly on the extract; (iii) the sum of arsenic species eluting from the HPLC column. Extraction efficiencies were low (range 10^-64%, mean 36%), but column recovery was acceptable (generally >80%) except for the fish samples, where substantial, currently unexplained, losses were observed. The dominating arsenic species in the extracts of freshwater algae were arsenosugars, whereas arsenate [As(V)] was present only as a minor constituent. On the other hand, plant extracts contained only inorganic arsenic, except for two samples which contained trace amounts of dimethylarsinate (DMA) and the tetramethylarsonium cation (TETRA). The oxo-arsenosugar-phosphate (ca. 35% of extractable arsenic) and the oxo-arsenosugar-glycerol (ca. 20%) as well as their thio-analogues (1-10%) were found in the mussel extracts, while arsenobetaine (AB) was present as a minor species only. In general, fish extracts contained only traces of arsenobetaine, and the oxo-arsenosugar-phosphate was the major arsenic compound. In addition, samples of white bream contained thio-arsenosugar-phosphate; this is the first report of a thio-arsenical in a fish sample. The frog presented an interesting arsenic speciation pattern because in addition to the major species, arsenite [As(III)] (30%) and the tetramethylarsonium cation (35%), all three intermediate methylation products, methylarsonate (MA), dimethylarsinate and trimethylarsine oxide (TMAO), and arsenate were also present. Collectively, the data indicate that arsenobetaine, the major arsenical in marine animals, is virtually absent in the freshwater animals investigated, and this represents the major difference in arsenic speciation between the two groups of organisms.

"Coupling Of Sequential Injection With Liquid Chromatography For The Automated Derivatization And On-line Determination Of Amino Acids"
Talanta 2006 Volume 69, Issue 4 Pages 841-847
Constantinos K. Zacharis, Georgios A. Theodoridis and Anastasios N. Voulgaropoulos

Abstract: The principle of sequential injection (SI) was exploited to develop a fully automated pre-column derivatization procedure combined on-line to liquid chromatography (LC). Using SI-LC derivatization 14 amino acids were determined fluorimetrically in pharmaceuticals with o-phthaldialdehyde (OPA) as the derivatization reagent. The SI system was used for the handling of samples and reagents, on-line mixing and introduction to the LC injection system. Chemical (pH and reagents concentrations) and instrumental variables (sample and reagent volumes, reaction time and flow rate) were optimized to attain the highest reaction yield and detector signal. Reversed phase chromatographic resolution of 14 amino acids was achieved within 35 min using gradient elution. The automated operation of the coupled SI-LC system resulted in very satisfactory performance. The method was applied for the simultaneous determination of amino acids in pharmaceutical formulations.

"Determination Of Gentamicin In Pharmaceutical Formulations Using Peroxyoxalate Chemiluminescent Detection In Flow-injection Analysis"
Talanta 2006 Volume 69, Issue 3 Pages 763-768
Jos&eacute; M. Fern&aacute;ndez-Ramos, Ana M. Garc&iacute;a-Campa&ntilde;a, Ferm&iacute;n Al&eacute;s-Barrero and Juan M. Bosque-Sendra

Abstract: A simple and sensitive procedure for the determination of gentamicin is presented, based on the use of the peroxyoxalate chemiluminescent (PO-CL) system in presence of imidazole as a catalyst. The gentamicin has to be previously derivatized with o-phthaladehyde (OPA) in order to obtain a fluorophore, which participates in the PO reaction, producing a CL emission proportional to the gentamicin concentration. The method is developed by using a particular flow-injection analysis (FIA) manifold, employing sodium dodecyl sulfate (SDS) micellar medium as a carrier in order to avoid the degradation of PO in water. The optimization of the instrumental and chemical variables affecting the CL reaction was rigorously carried out by using experimental design methodology. The method has been successfully applied to pharmaceutical formulations. © 2005 Elsevier B.V. All rights reserved.

"Automation Of Simultaneous Release Tests Of Two Substances By Sequential Injection Chromatography Coupled With Franz Cell"
Talanta 2006 Volume 69, Issue 3 Pages 730-735
J. Klimundov&aacute;, D. &Scaron;atinsk&yacute;, H. Sklen&aacute;&#345;ov&aacute; and P. Solich

Abstract: This presented paper deals with a methodology for the separation and simultaneous determination of two active substances in topical pharmaceutical formulation composed of lidocaine (L) and prilocaine (P). The methodology described is based on the sequential injection chromatography (SIC) with UV detection. Monolithic Column Chromolith Flash RP-18, 25 mm x 4.6 mm (Merck, Germany) was used. Separation was performed using elution with binary mobile phase composed of acetonitrile-phosphate buffer 0.05 M (40:80 (v/v)) + 0.01% triethylamine (adjusted to pH 7.1 with H3PO4) at a flow rate of 0.6 mL min-1. The analysis duration was <7 min. The method was linear over the range of 2.5-200 mg L-1 with a detection limit of 0.25 mg L-1 for both substances.The system was then coupled with Franz cell. Fully automated system for the in vitro release testing of semisolid dosage forms based on sequential injection analysis (SIA) was developed. Simultaneous measurement of L and P release was done by this system. Samples were taken in 10.5 min intervals during 4 h of the release test. Each test was followed by calibration with five standard solutions. Receiving medium was replenished automatically by the system.

"Enzymatic Rotating Biosensor For Ciprofloxacin Determination"
Talanta 2006 Volume 69, Issue 3 Pages 691-699
Angel A.J. Torriero, Juan J.J. Ruiz-D&iacute;az, Eloy Salinas, Eduardo J. Marchevsky, Mar&iacute;a I. Sanz and Julio Raba

Abstract: The high sensitivity that can be attained using an enzymatic system and mediated by catechol has been verified by on-line interfacing of a rotating biosensor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP [EC 1.11.1.7], immobilized on a rotating disk, in the presence of hydrogen peroxide, catalyzed the oxidation of catechol, whose back electrochemical reduction was detected on a glassy carbon electrode surface at -200 mV. Thus, when ciprofloxacin (CF) was added to the solution, this piperazine-containing compound participate in Michael addition reactions with catechol to form the corresponding piperazine-quinone derivatives, decreasing the peak current obtained, in proportion with the increase of its concentration. The highest response for CF was obtained around pH 7. This method could be used to determine CF concentration in the range of 0.02-65 µM (r = 0.999). The determination of CF concentration was possible with a detection limit of 0.4 nM, in the processing of as many as 25 samples per hour. Application of this analysis to different pharmaceutical samples containing CF supports the utility of the HRP-rotating biosensor.

"A Sequential Injection Fluorometric Procedure For Rapid Determination Of Total Protein In Human Serum"
Talanta 2006 Volume 69, Issue 3 Pages 681-685
Xuwei Chen and Jianhua Wang

Abstract: A sensitive procedure for the quantification of total protein bovine serum albumen (BSA) in human serum was presented with sequential injection sampling and fluorometric detection. A few microliters of sample and fluorescamine solutions were aspirated into the holding coil to facilitate the reaction of protein with fluorescamine by giving rise to a blue-green-fluorescent derivative. The derivative was afterwards excited by a 400 nm radiation from a UV radiator, and the emitted fluorescence was monitored at the wavelength of 470 nm. By loading 5.0 µl of sample and 4.0 µl of fluorescamine solution 0.075% (m/v), a linear calibration graph was obtained within 0.3-12.5 µg mL-1, and a detection limit (3σ) of 0.1 µg mL-1 was achieved, along with a sampling frequency of 40 h-1 and a RSD value of 2.1% at the 5.0 µg mL-1 levels. Protein contents in human serums were analyzed by using the present procedure, and reasonable agreements were obtained with those obtained by a documented spectrophotometric (Biuret) method.

"Flow-injection Fluorometric Quantification Of Pyruvate Using Co-immobilized Pyruvate Decarboxylase And Aldehyde Dehydrogenase Reactor: Application To Measurement Of Acetate, Citrate And L-lactate"
Talanta 2006 Volume 69, Issue 3 Pages 637-642
Tadayuki Tsukatani and Kiyoshi Matsumoto

Abstract: A flow-injection system for the quantification of pyruvate based on the coupled reactions of pyruvate decarboxylase (PDC) and aldehyde dehydrogenase (AlDH) was conceived and optimized. A co-immobilized PDC and AlDH reactor was introduced into the flow line. Sample and reagent (NAD+) were injected into the flow line by an open sandwich method and the increase of NADH produced by the immobilized-enzyme reactor was monitored fluorometrically at 455 nm (excitation at 340 nm). Linear relationships between the responses and concentrations of pyruvate were observed in the ranges of 2.0 x 10^-5 to 1.5 x 10^-3 M at the flow rate of 1.0 mL min-1 and 5.0 x 10^-6 to 1.0 x 10^-3 M at the flow rate of 0.5 mL min-1. The relative standard deviation for 10 successive injections was 0.95% at the 1.0 mM level. This FIA system for pyruvate was applied to the measurement of acetate, citrate and l-lactate. © 2005 Elsevier B.V. All rights reserved.

"Flow Injection Direct Spectrophotometric Assay For The Speciation Of Trace Chromium(III) And Chromium(VI) Using Chromotropic Acid As Chromogenic Reagent"
Talanta 2006 Volume 69, Issue 3 Pages 615-620
Demetrius G. ThemelisCorresponding Author Contact Information, E-mail The Corresponding Author, Fotini S. Kika and Anastasios Economou

Abstract: A new rapid and sensitive FI assay is reported for the simultaneous direct spectrophotometric determination of trace Cr(VI) and Cr(III) in real samples. The method is based upon the reaction of Cr(VI) with chromotropic acid (CA) in highly acidic medium to form a water-soluble complex (?max = 370 nm). Cr(III) reacts with CA only after its on-line oxidation to Cr(VI) by alkaline KIO4. The determination of each chromium species in the sample was achieved by absorbance differences. The calibration curves were linear over the range 3-4000 ?g L-1 and 30-1200 ?g L-1 for Cr(VI) and Cr(III), respectively, while the precision close to the quantitation limit was satisfactory in both cases (sr = 3.0% for Cr(VI) and 4.0% for Cr(III) (n = 10) at 10 and 50 ?g L-1 level, respectively). The method developed proved to be adequately selective and sensitive (cL = 1 and 10 ?g L-1 for Cr(VI) and Cr(III), respectively). The application of the method to the analysis of water samples (tap and mineral water) gave accurate results based on recovery studies (93-106%). Analytical results of real sample analysis were in good agreement with certified values. © 2005 Elsevier B.V. All rights reserved.

"Analytical Strategy Photodegradation/chemiluminescence/continuous-flow Multicommutation Methodology For The Determination Of The Herbicide Propanil"
Talanta 2006 Volume 69, Issue 3 Pages 608-614
J.R. Albert-Garc&iacute;a, M. Catala Icardo and J. Mart&iacute;nez Calatayud

Abstract: The present paper is dealing with an analytical strategy based on coupling photodegradation, chemiluminescence and multicommutation continuous-flow methodology for the determination of the pesticide Propanil, a common herbicide. The pesticide solution is inserted as small segments sequentially alternated with segments of the solution for adjusting the suitable medium for the photodegradation. Both flow-rates (sample and medium) are adjusted to required time for photodegradation, 2.0 min; and then, the resulting solution is also sequentially inserted as segments alternated with segments of the oxidizing solutions system, 1.00 x 10^-4 mol L-1 potassium permanganate in 2.00 mol L-1 sulphuric acid medium. The calibration range, from 10 ?g L-1 to 25 mg l-1, resulted in a linear behavior over the range 10 ?g l-1-5 mg L-1 and fitting the linear equation: I = 780.30C + 95.28; correlation coefficient 0.9999. The limit of detection was 8 ?g L-1 and the sample throughput 20 h-1. After testing the influence of a large series of potential interferents the method is applied to water samples obtained from different places and to one formulation. The method is valid for the determination of other pesticides from the same chemical family, namely: alachlor, flumetsulam, furalaxyl and ofurace. Calibration graphs, limits of detection, repeatability and determination in water samples are obtained for each reported pesticide. © 2005 Elsevier B.V. All rights reserved.

"Speciation Analysis Of Inorganic Arsenic By A Multisyringe Flow Injection System With Hydride Generation–atomic Fluorescence Spectrometric Detection"
Talanta 2006 Volume 69, Issue 2 Pages 500-508
L.O. Leal, R. Forteza and V. Cerd&agrave;

Abstract: In this study, a new technique by hydride generation-atomic fluorescence spectrometry (HG-AFS) for determination and speciation of inorganic arsenic using multisyringe flow injection analysis (MSFIA) is reported. The hydride (arsine) was generated by injecting precise known volumes of sample, a reducing sodium tetrahydroborate solution (0.2%), hydrochloric acid (6 M) and a pre-reducing solution (potassium iodide 10% and ascorbic acid 0.2%) to the system using a multisyringe burette coupled with one multi-port selection valve. This solution is used to pre-reduce As(V) to As(III), when the task is to speciate As(III) and As(V). As(V) is determined by the difference between total inorganic arsenic and As(III). The reagents are dispensed into a gas-liquid separation cell. An argon flow delivers the arsine into the flame of an atomic fluorescence spectrometer. A hydrogen flow has been used to support the flame. Nitrogen has been employed as a drier gas (Fig. 1). Several variables such as sample and reagents volumes, flow rates and reagent concentrations were investigated in detail. A linear calibration graph was obtained for arsenic determination between 0.1 and 3 µg l-;1. The detection limit of the proposed technique (3sb/S) was 0.05 µg l-;1. The relative standard deviation (RSD) of As at 1 µg l-;1 was 4.4 % (n = 15). A sample throughput of 10 samples per hour was achieved. This technique was validated by means of reference solid and water materials with good agreement with the certified values. Satisfactory results for speciation of As(III) and As(V) by means of the developed technique were obtained.
Arsenic(3+) Arsenic(5+) NWRI TMDA-54.3 NRCC CASS-4 BCR 279 Fluorescence Speciation Volatile generation Multisyringe Interferences

"Flow Injection Potentiometric Determination Of Clobutinol Hydrochloride"
Talanta 2006 Volume 69, Issue 2 Pages 481-487
Y.M. Issa and S.I.M. Zayed

Abstract: New clobutinol (Clob) ion-selective polyvinyl chloride (PVC) membrane electrodes, based on the ion-associates of Clob with phosphotungstic acid or phosphomolybdic acid were prepared using dibutyl phthalate as plasticizing solvent. The electrodes were characterized in terms of membrane composition, temperature and pH. The sensors showed a near-Nernstian response over the concentration ranges (6.31 x 10^-6)-(1.00 x 10^-2) and (5.01 x 10^-5)-(1.00 x 10^-2) M in the case of clobutinol-phosphotungstate ((Clob)3-PT) applying batch and flow injection (FI) analysis, respectively, and (1.58 x 10^-5)-(1.00 x 10^-2) and (5.01 x 10^-5)-(1.00 x 10^-2) M in case of clobutinol-phosphomolybdate ((Clob)3-PM) for batch and FI analysis systems, respectively. The electrodes were successfully applied for the potentiometric determination of ClobCl in pharmaceutical preparation and urine in steady state and flow injection conditions. The electrodes exhibit good selectivity for Clob with respect to a large number of inorganic cations, sugars and amino acids.

"Flow-injection Turbidimetric Determination Of Homatropine Methylbromide In Pharmaceutical Formulations Using Silicotungstic Acid As Precipitant Reagent"
Talanta 2006 Volume 69, Issue 1 Pages 239-242
Larissa S. Canaes, Oldair D. Leite and Orlando Fatibello-Filho

Abstract: A flow-injection turbidimetric procedure exploiting merging zones is proposed for determining homatropine methylbromide (HMB) in pharmaceutical preparations. The determination is based on the precipitation reaction of homatropine methylbromide with silicotungstic acid in acidic medium to form a precipitate, which was measured at 410 nm. The analytical curve was linear in the HMB concentration range from 8.1 x 10^-5 to 2.2 x 10^-4 mol l-1, with a detection limit of 5.0 x 10^-6 mol l-1. The recoveries ranged from 96 to 103%, the sampling frequency was 70 determinations per hour and relative standard deviations were less than 1.5% (n = 10). The results obtained for commercial formulations using the FIA procedure were in good agreement with those obtained by using a comparative method. © 2005 Elsevier B.V. All rights reserved.

"Flow-injection Chemiluminescence Simultaneous Determination Of Cobalt(II) And Copper(II) Using Partial Least Squares Calibration"
Talanta 2006 Volume 69, Issue 1 Pages 160-165
Baoxin LiCorresponding Author Contact Information, E-mail The Corresponding Author, Dongmei Wang, Jiagen Lv and Zhujun Zhang

Abstract: A flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co2+ and Cu2+ using partial least squares (PLS) calibration. This method is based on the fact that both Co 2+ and Cu2+ catalyse the CL reaction of luminol-H 2O2, and that their kinetic characteristics of Co 2+ and Cu2+ are significantly different in the luminol-H2O2 system. The CL intensity was measured and recorder at different reaction times of luminol-H2O 2Co2+Cu2+, and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed of 16 sample solutions using an orthogonal calibration design for two component mixtures. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co 2+ and Cu2+ determination, and was successfully applied to the simultaneous determination of both analytes in real water sample. The present paper demonstrated that the simultaneous determination of two metal ions without any prior separation has been possible using flow-injection CL system. © 2005 Elsevier B.V. All rights reserved.

"An Analytical Application Of The Electrocatalysis Of The Iodate Reduction At Tungsten Oxide Films"
Talanta 2006 Volume 69, Issue 1 Pages 148-153
Jos&eacute; Roberto Caetano da Rocha, Tiago Luiz Ferreira, Roberto Manuel Torresi and Mauro Bertotti

Abstract: Films of non-stoichiometric tungsten oxides have been deposited onto glassy carbon surfaces by electrodeposition from acidic W(VI) solutions and the chemical stability of these oxides was investigated by using the electrochemical quartz crystal microbalance. At these modified surfaces, rotating disc electrode voltammetric experiments indicated that iodate is electrocatalytically reduced in a mass-transport controlled process. The influence of the film thickness on the response to iodate was investigated and the results indicated a linear relationship between catalytic current and film thickness for relatively thin oxide layers. The modified electrode was employed successfully as an amperometric sensor for iodate in a flow injection apparatus. The linear response of the developed method is extended from 5 ?mol L-1 to 5 mmol L-1 iodate with a limit of detection (signal-to-noise = 3) of 1.2 ?mol L-1. The repeatability of the method for 41 injections of a 1 mmol L-1 iodate solution was 0.8% and the throughput was determined as 123 h-1. Interference from other oxidant anions such as nitrate and nitrite was not noticeable, whereas bromate and chlorate interfere at slight levels. The method was used in the determination of the iodate content in table salt samples. © 2005 Elsevier B.V. All rights reserved.

"Novel Analytical Applications Of Porphyrin To HPLC Post-column Flow Injection System For Determination Of The Lanthanides"
Talanta 2006 Volume 69, Issue 1 Pages 61-67
Jun-ichi Itoh, Jianhua Liu and Masashi Komata

Abstract: A novel indirect substitution spectrophotometric methodology using porphyrin is developed for the determination of some metals that do not react with porphyrin directly. The methodology is concerned with a multistep reaction system, which consists of 3 complexation reactions that occur in a sequence of EDTA with metal, EDTA with Cu(II) and porphyrin with Cu(II). The complexation reaction of Cu(II) with a cationic porphyrin, meso-tetrakis (4-N-trimethylaminophenyl)-porphine (ttmapp), which has a high molar absorptivity about 5 x 105 l mol-1 cm-1, serves for spectrophotometric detection. This methodology was verified through individual determinations of 14 species of lanthanides following a batchwise procedure, which was further developed to an automatic procedure on a HPLC post-column flow injection system for simultaneous analysis of the lanthanides. Compared with the conventional post-column derivatization method using 4-(2-pyridylazo) resorcinol (PAR), the analytical sensitivity was greatly improved in this method and the results also showed good linearity.

"Alumina Modified By Dimethyl Sulfoxide As A New Selective Solid Phase Extractor For Separation And Preconcentration Of Inorganic Mercury(II)"
Talanta 2006 Volume 69, Issue 1 Pages 55-60
Ezzat M. SolimanCorresponding Author Contact Information, E-mail The Corresponding Author, Mohamed B. Saleh and Salwa A. Ahmed

Abstract: Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1 ± 0.1 mmol g-1 of alumina. Hg(II) uptake was 1.90 mmol g-1(distribution coefficient log Kd = 5.658) at pH 1.0 or 2.0, 1.68 mmol g-1 (log Kd = 4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g-1 (log Kd < 3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values ? 3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2 l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100 mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5 ± 0.5, 98.5 ± 0.5 and 103.0 ± 1.0) based on excellent enrichment factor 1000, along with a good precision (RSD% 0.51-0.97%, N = 3) demonstrate the accuracy and validity of the new modified alumina sorbent for pre-concentrating ultratrace amounts of Hg(II) with no matrix interference. © 2005 Elsevier B.V. All rights reserved.

"Oxidative Extraction Versus Total Decomposition Of Soil In The Determination Of Thallium"
Talanta 2006 Volume 68, Issue 5 Pages 1736-1739
Monika Jakubowska, Wlodzimierz Zembrzuski and Zenon Lukaszewski

Abstract: An aqua regia extraction and a total decomposition of soil were compared in terms of thallium determination. A sequential extraction of soil, according to the BCR protocol, was also performed for additional information on thallium distribution in soil fractions. Certified reference material - soil GBW 07401 of Chinese origin, containing 1 ± 0.2 ppm of thallium was used in these experiments. Thallium was determined by flow injection-differential pulse-anodic stripping voltammetry (FI-DP-ASV). Only 35% of total thallium was extracted in the aqua regia extraction, while the total decomposition led to satisfactory recovery. The sequential extraction showed that only 5% of thallium in GBW 07401 is dissolvable in the four BCR procedure fractions, and that 95% of the element is entrapped in the residual parent matter. These results show that the aqua regia extraction does not ensure complete thallium extraction from soil. Surprisingly, the total decomposition is significantly less time consuming than the aqua regia extraction. © 2005 Elsevier B.V. All rights reserved.

"Electroanalysis Of Sulfonamides By Flow Injection System/high-performance Liquid Chromatography Coupled With Amperometric Detection Using Boron-doped Diamond Electrode"
Talanta 2006 Volume 68, Issue 5 Pages 1726-1731
Anchana Preechaworapun, Suchada Chuanuwatanakul, Yasuaki Einaga, Kate Grudpan, Shoji Motomizu and Orawon Chailapakul

Abstract: Sulfonamides (SAs) were electrochemically investigated using cyclic voltammetry at a boron-doped diamond (BDD) electrode. Comparison experiments were carried out using a glassy carbon electrode. The BDD electrode provided well-resolved oxidation, irreversible cyclic voltammograms and higher current signals when compared to the glassy carbon electrode. Results obtained from using the BDD electrode in a flow injection system coupled with amperometric detection were illustrated. The optimum potential from a hydrodynamic voltammogram was found to be 1100 mV versus Ag/AgCl, which was chosen for the HPLC-amperometric system. Excellent results of linear range and detection limit were obtained. This method was also used for determination of sulfonamides in egg samples. The standard solutions of 5, 10, and 15 ppm were spiked in a real sample, and percentage of recoveries was found to be between 90.0 and 107.7.

"Flow-injection In-line Complexation For Ion-pair Reversed Phase High Performance Liquid Chromatography Of Some Metal-4-(2-pyridylazo) Resorcinol Chelates"
Talanta 2006 Volume 68, Issue 5 Pages 1720-1725
Supalax Srijaranai, Saiphon Chanpaka, Chutima Kukusamude and Kate Grudpan

Abstract: Flow injection (FI) was coupled to ion-pair reversed phase high performance liquid chromatography (IP-RPHPLC) for the simultaneous analysis of some metal-4-(2-pyridylazo) resorcinol (PAR) chelates. A simple reverse flow injection (rFI) set-up was used for in-line complexation of metal-PAR chelates prior to their separation by IP-RPHPLC. The rFI conditions were: injection volume of PAR 85 µL, flow rate of metal stream 4.5 mL min-1, concentration of PAR 1.8 x 10^-4 mol L-1 and the mixing coil length of 150 cm. IP-RPHPLC was carried out using a C18 ?Bondapak column with the mobile phase containing 37% acetonitrile, 3.0 mmol L-1 acetate buffer pH 6.0 and 6.2 mmol L-1 tetrabutylammonium bromide (TBABr) at a flow rate of 1.0 mL min-1 and visible detection at 530 and 440 nm. The analysis cycle including in-line complexation and separation by IP-RPHPLC was 16 min, which able to separate Cr(VI) and the PAR chelates of Co(II), Ni(II) and Cu(II). © 2005 Elsevier B.V. All rights reserved.

"Multicommutation-NIR Determination Of Hexythiazox In Pesticide Formulations"
Talanta 2006 Volume 68, Issue 5 Pages 1700-1706
Josep F. Ventura-Gayete, Sergio Armenta, Salvador Garrigues, &Aacute;ngel Morales-Rubio and Miguel de la Guardia

Abstract: A multicommutated flow-system was designed in order to increase analytical throughput and for controlling thermal effects on the NIR spectra for determination of Hexythiazox in pesticide formulations. An on-line standard addition was carried out showing the versatility and repeatability of multicommutation for the on-line mixing and dilution of solutions. Results obtained for commercial samples were statistically comparable with those obtained by an HPLC-reference method. Multicommutation-NIR allows the analysis of 52 samples per hour, in front of the 30 samples per hour analyzed by the NIR-batch procedure and the 7 samples per hour analyzed by HPLC-reference method.

"Optimization By Means Of Responses Surface Of An Analytical Sequence Using A Sequential Injection System"
Talanta 2006 Volume 68, Issue 5 Pages 1617-1622
Alberto Pasamontes and M Pilar Callao

Abstract: An experimental design method was applied to determine the optimum working conditions for sequential injection analysis (SIA) to obtain second-order data that will be treated using multivariate curve resolution with alternating least squares (MCR-ALS).The critical step is to design an analytical sequence that provides relevant information. This sequence depends on parameters related to the system, the chemical reaction, and the chemometric treatment of the data. Also, from the multiple responses that quantify the quality of this analytical sequence, a single response is determined from the desirability function.This method involves a factor-screening step, in which both the global desirability function and the individual responses are considered and a response surface-modelling step, in which the most relevant factors are considered.

"Amperometric Detection Of Ultra Trace Amounts Of Hg(I) At The Surface Boron Doped Diamond Electrode Modified With Iridium Oxide"
Talanta 2006 Volume 68, Issue 5 Pages 1610-1616
Abdollah SalimiCorresponding Author Contact Information, E-mail The Corresponding Author, E-mail The Corresponding Author, Vali Alizadeh and Rahman Hallaj

Abstract: Iridium oxide (IrOx) films formed electrochemically on the surface boron doped diamond electrode by potential cycling in the range -0.2 to 1.2 V from a saturated solution of alkaline iridium(III) solution. A strongly adherent deposit of iridium oxide is formed after 5-10 potential scans. The properties, stability and electrochemical behavior of iridium oxide layers were investigated by atomic force microscopy and cyclic voltammetry. The boron doped diamond (BDD) electrode modified with electrodeposition of a thin film, exhibited an excellent catalytic activity for oxidation of Hg(I) over a wide pH range. The modified electrode shows excellent analytical performance for Hg(I) amperometric detection. The detection limit, sensitivity, response time and dynamic concentration ranges are 3.2 nM, 77 nA ?M-1, 100 ms and 5 nM-5 ?M. These analytical parameters compare favorably with those obtained with modern analytical techniques and recently published electrochemical methods. © 2005 Elsevier B.V. All rights reserved.

"Single-step Microwave Digestion With HNO3 Alone For Determination Of Trace Elements In Coal By ICP Spectrometry"
Talanta 2006 Volume 68, Issue 5 Pages 1584-1590
Jie Wang, Tetsuya Nakazato, Kinya Sakanishi, Osamu Yamada, Hiroaki Tao and Ikuo Saito

Abstract: A microwave digestion method with HNO3 alone was conducted at a temperature as high as 250°C for determination of 19 trace elements (Li, Be, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Cd, Cs, Ba, Hg, and Pb) in coal jointly by inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and flow injection ICP-MS (FI-ICP-MS). The validity of determination was assessed by using three standard coals, SRM 1632 c, BCR 180, and SARM 19. It was found that the high-temperature digestion led to an extensive decomposition of the organic matrix and clay in coal, and no dissolved and solid carbon remained in the final solution after evaporation. Good recoveries were observed for all trace elements in three coals, with the exception of V, Rb, and Cs in high-ash SARM 19. Additionally, FI-ICP-MS combined with the present digestion without evaporation pretreatment was proved to be a rapid and efficient approach for determination of ultra-trace elements such as Se, Cd, and Hg in coal. © 2005 Elsevier B.V. All rights reserved.

"Electrochemiluminescent Behavior Of Allopurinol In The Presence Of Ru(bpy)32+"
Talanta 2006 Volume 68, Issue 5 Pages 1544-1549
Yuwu Chi, Junlin Xie and Guonan Chen

Abstract: The electrochemiluminescent (ECL) response of allopurinol was studied in aqueous media over a wide pH range (pH 2-13) using flow injection (FI) analysis. It was revealed that allopurinol itself had no ECL activity, but could greatly enhance the ECL of Ru(bpy)32+ in alkaline media giving rise to a sensitive FI-ECL response. The effects of experimental conditions including the mode of applied voltage signal, the potential of working electrode, pH value, the flow rate of carrier solution, and the concentration of Ru(bpy)32+ and allopurinol on the ECL intensity were investigated in detail. The most sensitive FI-ECL response of allopurinol was found at pH 12.0, where the FIA-ECL intensity showed a linear relationship with concentration of allopurinol in the range 1 x 10^-8 mol L-1 to 5 x 10^-7 mol L-1, and the detection limit was 5 x 10^-9 mol L-1.

"Determination Of Pentavalent Antimony In Antileishmaniotic Drugs Using An Automated System For Liquid-liquid Extraction With On-line Detection"
Talanta 2006 Volume 68, Issue 5 Pages 1536-1543
Luciano Augusto Trivelin, Jarbas Jos&eacute; Rodrigues Rohwedder and Susanne Rath

Abstract: An automated system for liquid-liquid extraction flow analysis (LLE-FA) for the determination of Sb(V) in antileishmanial drugs is presented. The method is based on extraction in a 5 mL glass extraction chamber of an ion pair formed between hexachloroantimoniate anion and rhodamine B cation into toluene. The detection system consists of a green light emitting diode (LED) and a photodiode. The system is controlled by a microcomputer using a program written in Visual Basic 3.0. The extraction process was optimized and the following experimental parameters were established: sample loop of 150 µL; reagent loop of 900 µL; stirring time of 100 s; phase separation time of 80 s; volumetric ratio of 1:1 (aqueous/organic). The method was in-house validated for the determination of Sb(V) in meglumine antimoniate. The following performance criteria were obtained: linearity of 0.9989, linear range of 7.0 x 10^-5 to 7.2 x 10^-4 mol Sb(V) L-1, sensitivity of 1.61 x 106 ± 2 arbitrary units L mol-1 (P < 0.05), intra-assay precision of 3.5% (n = 5; 4.1 x 10^-4 mol L-1 Sb(V). Whereas the method is selective in the presence of Sb(III), As(III) and Pb(II) at concentrations up to one tenth of the concentration of Sb(V), As(V) interferes. The accuracy of the method was evaluated through comparison of results obtained from analyzes of pharmaceutical formulations by the proposed LLE-FA method with those obtained by inductively coupled plasma optic emission spectrometry (ICP OES) and differential pulse polarography for total antimony and Sb(III), respectively. The proposed method presented an analytical frequency of eight analysis per hour and is suitable for Sb(V) determination in the quality control of drugs employed for the treatment of leishmaniasis.

"The Potential Of Combining Solid-phase Optosensing And Multicommutation Principles For Routine Analyses Of Pharmaceuticals"
Talanta 2006 Volume 68, Issue 5 Pages 1482-1488
Juan F. Garc&iacute;a-Reyes, Eulogio J. Llorent-Mart&iacute;nez, Pilar Ortega-Barrales and Antonio Molina-D&iacute;az

Abstract: In this work, we have explored the analytical potential of combining solid-phase optosensing and multicommutation principles, applied to the field of routine analyzes of pharmaceuticals. This marriage benefits from the advantaging features of both concepts: the ability of multicommutation to provide increased repeatability, easier sample handling, reduced sample and reagent consumption as well as minor waste generation, combined with the enhancement of both sensitivity and selectivity obtained when a solid support is used to carry out the spectroscopic measurements directly on it. This approach has been evaluated by developing a method for the simultaneous analysis of two active principles (piroxicam and pyridoxine) in pharmaceutical formulations, using a non-polar sorbent as a solid support to attain the separation and subsequent pre-concentration/detection of the targeted analytes. A multicommutated flow-through multisensor based on the direct intrinsic solid-phase UV absorbance measurements of the analytes on a packed C18 silica gel bed was then thoroughly developed. The usefulness of this approach was assessed when it was applied to the determination of piroxicam and pyridoxine in different pharmaceutical formulations obtaining remarkable results.

"The Use Of A Micropump Based On Capillary And Evaporation Effects In A Microfluidic Flow Injection Chemiluminescence System"
Talanta 2006 Volume 68, Issue 4 Pages 1384-1389
Yan-Xia Guan, Zhang-Run Xu, Jing Dai and Zhao-Lun Fang

Abstract: The performance of a micropump operating on evaporation and capillary effects, developed for microfluidic (lab-on-a-chip) systems, was studied employing it as the fluid drive in a microfluidic flow injection (FI) system, with chemiluminescence (CL) detection. The micropump featured simple structure, small dimensions, low fabrication cost and stable and adjustable flow-rates during long working periods. Using a micropump with 6.6 cm2 evaporation area, with the ambient temperature and relative humidity fluctuating within 2 h in the ranges 20-21°C and 30-32%, respectively, an average flow-rate of 3.02 µL/min was obtained, with a precision better than 1.2% RSD (n = 61). When applied to the microchip FI-CL system using the luminol/hexacyanoferrate/H2O2 reaction, a precision of 1.4% RSD (n = 11) was obtained for luminol at a sampling frequency of 30 h-1.

"Mercury Determination By Cold Vapor Atomic Absorption Spectrometry Utilizing UV Photoreduction"
Talanta 2006 Volume 68, Issue 4 Pages 1366-1370
Ryan F. Bendl, Jeremy T. Madden, Allison L. Regan and Neil Fitzgerald

Abstract: A method for the determination of mercury via UV photoreduction has been investigated. Mercury vapor was generated by the reduction of mercury species in an acetic acid solution using UV radiation. Detection of the volatile mercury was accomplished by atomic absorption spectrometry. An optimized system was found to provide a detection limit (defined as the concentration giving a signal equal to three times the standard deviation of the blank) of 2.1 ?g L-1 with a precision of 2.9% relative standard deviation (n = 8) for a 500 ?g L-1 mercury standard. The effect of various metal ions on the mercury signal was investigated and the method validated with a NRCC certified dogfish liver material (DOLT-3) using the method of standard additions. A reaction pathway is hypothesized for UV photoreduction. © 2005 Elsevier B.V. All rights reserved.

"Enzymatic Rotating Biosensor For Cysteine And Glutathione Determination In A FIA System"
Talanta 2006 Volume 68, Issue 4 Pages 1343-1352
Juan J.J. Ruiz-D&iacute;az, Angel A.J. Torriero, Eloy Salinas, Eduardo J. Marchevsky, Mar&iacute;a I. Sanz and Julio Raba

Abstract: The high sensitivity that can be attained using an enzymatic system and mediated by catechols has been verified by on-line interfacing of a rotating biosensor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in presence of hydrogen peroxide catalyzed the oxidation of catechols, whose back electrochemical reduction was detected on glassy carbon electrode surface at -150 mV. Thus, when l-cysteine (Cys) or glutathione (GSH) was added to the solution, these thiol-containing compounds participate in Michael addition reactions with catechols to form the corresponding thioquinone derivatives, decreasing the peak current obtained proportionally to the increase of its concentration. Cys was used as the model thiol-containing compound for the study. The highest response for Cys was obtained around pH 7. This method could be used to determine Cys concentration in the range 0.05-90 µM (r = 0.998) and GSH concentration in the range 0.04-90 µM (r = 0.999). The determination of Cys and GSH were possible with a limit of detection of 0.7 and 0.3 nM, respectively, in the processing of as many as 25 samples per hour. Current response of the HRP-rotating biosensor is not affected by the oxidized form of GSH and Cys (glutathione disulfide, GSSG, and l-cystine, respectively), by sulfur-containing and alkyl-amino compounds such as methionine and lysine, respectively. The interferences from easily oxidizable species such as ascorbic acid and uric acid are lowest.

"Use Of Nickel Implanted Boron-doped Diamond Thin Film Electrode Coupled To HPLC System For The Determination Of Tetracyclines"
Talanta 2006 Volume 68, Issue 4 Pages 1329-1335
Surudee Treetepvijit, Anchana Preechaworapun, Narong Praphairaksit, Suchada Chuanuwatanakul, Yasuaki Einaga and Orawon Chailapakul

Abstract: The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)-20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05-100 ppm with the overall average recoveries from 83.3 to 102.5% and RSD of less than 10%. The proposed method was further applied to analyze shrimp samples.

"Determination Of Total Mercury In Biological Samples Using Flow Injection CVAAS Following Tissue Solubilization In Formic Acid"
Talanta 2006 Volume 68, Issue 4 Pages 1259-1263
Masahiko Kan, Scott N. Willie, Christine Scriver and Ralph E. Sturgeon

Abstract: Total mercury in biological samples was determined by flow injection (FI) cold vapor atomic absorption spectrometry (CVAAS) following tissue solubilization with formic acid. A mixture of potassium bromide and potassium bromate was used to decompose organomercury compounds prior to their reduction with sodium borohydride. A gold amalgam system was used to achieve lower detection limits when required. National Research Council Canada certified reference materials dogfish liver (DOLT-3), dogfish flesh (DORM-2) and lobster hepatopancreas (TORT-2), as well as oyster tissue (NIST SRM 1566b) and mussel tissue (NIST SRM 2976) were used to assess the accuracy of the method. The method of standard additions provided the most accurate results. Limit of detection (LOD) for Hg in the solid sample of 0.001 and 0.01 ?g g -1 were achieved with and without amalgamation, respectively. The precision of measurement for 1.6 ng mL-1 methylmercury was 2.7% using the amalgam system. © 2005 Elsevier B.V. All rights reserved.

"Fluorimetric Determination Of Histamine In Wine And Cider By Using An Anion-exchange Column-FIA System And Factorial Design Study"
Talanta 2006 Volume 68, Issue 4 Pages 1126-1134
Gloria del Campo, Beatriz Gallego and I&ntilde;aki Berregi

Abstract: A study has been performed of the conditions for the reaction of histamine with o-phthaldehyde in a flow injection analysis system employing three channels, using an anion-exchange column to eliminate sample matrix interferences. Factorial design was used to determine which operational parameters should be included in the optimization and their optimal values were found. The method developed shows good selectivity for histamine determination in alcoholic beverages. A linear response of up to 2.0 mg L-1 was observed and the detection and quantification limits were 30 and 101 µg l-1, respectively. The repeatability, measured by the RSD for 10 replicate injections, was 0.84 and 0.52% for histamine solutions of 0.20 and 2.0 mg l-1, respectively. The recoveries obtained in wine and cider samples were close to 100% and a sample frequency of 24 samples per hour was achieved.

"A Mediator-free Screen-printed Amperometric Biosensor For Screening Of Organophosphorus Pesticides With Flow-injection Analysis (FIA) System"
Talanta 2006 Volume 68, Issue 4 Pages 1089-1095
Mianhong Shi, Jingjing Xu, Song Zhang, Baohong Liu and Jilie Kong

Abstract: A mediator-free amperometric biosensor for screening organophosphorus pesticides (OPs) in flow-injection analysis (FIA) system based on anticholinesterase activity of OPs to immobilized acetylcholinesterase enzyme (AChE) has been developed. The enzyme biosensor is prepared by entrapping AChE in Al2O3 sol-gel matrix screen-printed on an integrated 3-electrode plastic chip. This strategy is found not only increase the stability of the embedded AChE, but also effectively catalyze the oxidative reaction of thiocholine, making the Al2O3-AChE biosensor detects the substrate at 0.25 V (versus Ag/AgCl), hundreds mini-volt lower than other reported mediator-free ones. The Al2O3-AChE biosensor is thus coupled to FIA system to build up a simple and low-cost FIA-EC system for screening OPs in real samples. A wide linear inhibition response for dichlorvos, typical OP, is observed in the range of 0.1-80 ?M, corresponding to 7.91-84.94% inhibition for AChE. The detection limit for dichlorvos is achieved at 10 nM in the simulated seawater for 15 min inhibiting time, which allows the biosensor quantitatively detects the ecotoxicological effect of the real samples from the seaports in eastern China, where the OPs pollution is confirmed by GC-MS. © 2005 Elsevier B.V. All rights reserved.

"A Critical Examination Of The Components Of The Schlieren Effect In Flow Analysis"
Talanta 2006 Volume 68, Issue 4 Pages 1076-1082
Ana Cristi B. Dias, Eduardo P. Borges, Elias A.G. Zagatto and Paul J. Worsfold

Abstract: The Schlieren effect is a consequence of light inflections altering the spectrophotometric measurements that are due to the formation of optical artefacts such as mirror and lenses inside the flowing sample. It may influence signal-to-noise ratio, sample throughput and measurement repeatability in spectrophotometric flow-based procedures. It was critically examined, in order to provide guidelines for system design. Results demonstrate that the magnitude of the Schlieren effect is governed by the combined influence of two components. The first is related to loss of light by reflection at sharp liquid interfaces and prevails under poor mixing conditions. In this situation the transmitted light becomes more intense and somewhat erratic. The second is related to light refraction in regions with pronounced refractive index gradients, and prevails under good mixing conditions. It can lead to positive or negative modifications of the transmitted light, the direction being dependent on the relevance of these components. The importance of the solubility of the chemical species involved, the possibility of interactions with the inner wall of the tubing, and the feasibility of dual-wavelength spectrophotometry for compensating purposes are discussed. © 2005 Elsevier B.V. All rights reserved.

"Preconcentration And Speciation Of Chromium In Drinking Water Samples By Coupling Of On-line Sorption On Activated Carbon To ETAAS Determination"
Talanta 2006 Volume 68, Issue 4 Pages 1065-1070
R.A. Gil, S. Cerutti, J.A. G&aacute;squez, R.A. Olsina and L.D. Martinez

Abstract: An on-line flow injection (FI) pre-concentration-electrothermal atomic absorption spectrometry (ETAAS) method is developed for trace determination of chromium in drinking water samples by sorption on a conical minicolumn packed with activated carbon (AC) at pH 5.0. The chromium was removed from the minicolumn with 1.0% (v/v) nitric acid. An enrichment factor (EF) of 35-fold for a sample volume of 10 mL was obtained. The detection limit (DL) value for the pre-concentration method proposed was 3.0 ng l-1. The precision for 10 replicate determinations at the 0.5 µg L-1 Cr level was 4.0% relative standard deviation (RSD), calculate with the peak heights obtained. The calibration graph using the pre-concentration system for chromium was linear with a correlation coefficient of 0.9992 at levels near the detection limits up to at least 50 µg l-1. The method was successfully applied to the determination of Cr(III) and Cr(VI) in drinking water samples.

"Determination Of Total And Dissolved Amount Of Iron In Water Samples Using Catalytic Spectrophotometric Flow Injection Analysis"
Talanta 2006 Volume 68, Issue 3 Pages 969-973
S. Lunvongsa, M. Oshima and S. Motomizu

Abstract: A flow injection spectrophotometric method has been developed for the determination of dissolved and total amounts of iron in tap and natural water samples. The method for the determination of iron employs a sample acidification step in order to decompose iron hydroxide and iron-complexes into free iron, Fe(III) and Fe(II). The amounts of free iron were detected using a catalytic action of Fe(III) and Fe(II) on the oxidation of N,N-dimethyl-p-phenylenediamine in the presence of hydrogen peroxide. Increase in absorbance of oxidized product was detected spectrophotometrically at 514 nm. The proposed method allows 0.02 and 0.06 µg l-;1 of LOD and LOQ, respectively, with relative standard deviation (RSD) below 2%. The accuracy and the precision of the method were evaluated by the analysis of the standard reference material, river water. The developed method was successfully applied to real water samples.
Spectrophotometry

"A Gravity Driven Micro Flow Injection Wetting Film Extraction System On A Polycarbonate Chip"
Talanta 2006 Volume 68, Issue 3 Pages 895-901
Zengxuan Cai, Hengwu Chen, Biao Chen and Chaobiao Huang

Abstract: A µflow injection wetting film liquid-liquid extraction system has been developed for trace analyte concentration and on-chip detection. A hydrophobic channel fabricated on a polycarbonate chip was used to support the wetting film, and hydrostatic pressure generated by the difference in liquid levels was employed to drive the fluids. Sequential injection of segments of aqueous sample solution and organic solvent was conducted by switching the sample- or solvent-containing vials to an on-chip sampling probe, and detection was performed by a co-focused, laser induced fluorescence detector. Using butyl rhodamine B as a model analyte and butanol as the solvent for both film-coating and elution, various experimental conditions such as hydrostatic pressure, coating time, channel length, sampling volume, and sample acidity were investigated. Under optimized conditions, a 24-fold enrichment factor was obtained with the consumption of about 3 µL sample solution, and a detection limit (3σ) of 6.0 x 10^-9 M butyl rhodamine B was achieved at the sampling rate of 19 h-1. Eleven consecutive runs of a 1.0 x 10^-5 M butyl rhodamine B solution produced a relative standard deviation of 1.5% for the detected fluorescence signals.

"Determination Of Nitrogen In Hydrolyzed Protein Formulations By Continuous Vapour Phase FTIR"
Talanta 2006 Volume 68, Issue 3 Pages 836-841
N.M.M. Coelho, S. Garrigues and M. de la Guardia

Abstract: An on-line system with vapor generation (VG) and Fourier transform infrared (FTIR) spectrometric detection has been developed for the determination of free ammonium and organic nitrogen in agrochemical formulations containing hydrolyzed proteins. Commercial samples were digested, in batch mode, with sulphuric acid and the obtained solution was alkalinized on-line to transform the NH4+ to NH3 that was continuously monitored by FTIR. Free ammonium was determined in the same system after simple dilution of undigested samples with water. Different gas phase separators were assayed in order to introduce gaseous NH3 into a home made IR gas cell of 10 cm pathlength, where the corresponding FTIR spectra were acquired by accumulating 10 scans per spectrum. The 967.0 cm-1 band was used for the quantification of ammonia. The figures of merit of the proposed method involve a linear range up to 100 mg L-1, a limit of detection (3σ) of 1.4 mg L-1 of N, a limit of quantification (10σ) of 4.8 mg L-1 of N, a precision (RSD) of 3.0% for 10 replicate determinations of a 10.0 mg L-1 of N and a sample measurement frequency of 60 h-1. The method was successfully applied to the determination of free ammonium and total N in commercial amino acid formulations and results compare well with those obtained by the Kjeldhal method.

"Mercury Determination By FI-CV-AAS After The Degradation Of Organomercurials With The Aid Of An Ultrasonic Field: The Important Role Of The Hypochlorite Ion"
Talanta 2006 Volume 68, Issue 3 Pages 813-818
J.L. Capelo, G.M. Rivas, L.G. Oliveira, C. Vilhena, A.C. Santos, T. Valada, M. Galesio, P. Oliveira, M.D.R. Gomes da Silva, E.M. Gaspar, et al.

Abstract: Due to new findings, the methodology based on room-temperature ultrasonic irradiation (sonolysis) for conversion of organomercurials into inorganic mercury [J.L. Capelo, I. Lavilla, C. Bendicho, Anal. Chem. 72 (2000) 4979-4984.] is further investigated. Inorganic mercury is selectively determined by Flow Injection-Cold Vapour Atomic Absorption Spectrometry (FI-CV-AAS) using SnCl 2/HCl. Complete oxidation of methyl-mercury can be accomplished within 90 s whilst phenyl and diphenyl-mercury can be degraded within 10 s using a 50% sonication amplitude (100 W nominal power) provided by a probe ultrasonic device (20.5 kHz frequency) and a 1 mol L-1 HCl liquid medium with the presence of hypoclorite ion. The importance of hypochlorite in reduction of organomercurials by stannous chloride is highlighted. Oxidation kinetics indicated a pseudo first-order reaction for methyl-mercury, phenyl-mercury, and dipheny-mercury.

"Automatic Chemiluminescence-based Determination Of Carbaryl In Various Types Of Matrices"
Talanta 2006 Volume 68, Issue 3 Pages 586-593
Jos&eacute; Antonio Murillo Pulgar&iacute;n, Aurelia Ala&ntilde;&oacute;n Molina and Pablo Fern&aacute;ndez L&oacute;pez

Abstract: Carbaryl, a modern pesticide widely used for both agricultural and non-agricultural purposes, was determined from the chemiluminescence produced in its reaction with Ce(IV) in a nitric acid medium containing rhodamine 6G as sensitizer, using flow-injection techniques. A straightforward automatic method based on measurements peak height and peak area, which are directly proportional to the carbaryl concentration, was thus developed. Calibration graphs are linear over the concentration range from 50 to 2000 ng mL-1. The limit of detection, as determined according to Clayton, is 45.6 and 28.7 ng mL-1 for peak height and peak area measurements, respectively. The relative standard deviation for 10 samples was less than 1.4% with both types of measurements. Two commercial formulations containing carbaryl were analyzed using both types of measurements, which provided acceptable recovery values. Solid-phase extraction was used to concentrate and separate the analyte from the matrix. The method was successfully applied to the analysis of spiked water samples as well as in soil and grain samples. The proposed method exhibited a high selectivity no other pesticide containing the naphthalene group such as antu, napropamide or naftalam, etc., was found to interfere with the determination of carbaryl.

"Using Sequential Injection Analysis For Fast Determination Of Phosphate In Coastal Waters"
Talanta 2005 Volume 70, Issue 3 Pages 513-517
Carsten Frank, Friedhelm Schroeder, Ralf Ebinghaus and Wolfgang Ruck

Abstract: A sequential injection analysis system (SIA) is described which is suited for the fast determination of filterable molybdate reactive phosphate (FRP, 0.2 µm) in coastal waters. It processes up to 270 samples per hour with a detection limit (3σ) of 0.05 µM and is used for surface mapping of phosphate in areas with steep concentration gradients like the Wadden Sea. The determination is based on the reaction of phosphate with acidic molybdate to phosphomolybdate, which builds non-fluorescent ion pairs with rhodamine 6G. The remaining rhodamine fluorescence is detected at 550 nm with an excitation at 470 nm. Syringe pump, valve and detector were controlled by a self made python programme, which was optimized for high speed SIA measurements in monitoring applications.

"Spectrophotometric Determination Of Sulphate In Automotive Fuel Ethanol By Sequential Injection Analysis Using Dimethylsulphonazo(III) Reaction"
Talanta 2005 Volume 68, Issue 3 Pages 992-999
Fabio Santos de Oliveira and Mauro Korn

Abstract: A sensitive SIA method was developed for sulphate determination in automotive fuel ethanol. This method was based on the reaction of sulphate with barium-dimethylsulphonazo(III) leading to a decrease on the magnitude of analytical signal monitored at 665 nm. Alcohol fuel samples were previously burned up to avoid matrix effects for sulphate determinations. Binary sampling and stop-flow strategies were used to increase the sensitivity of the method. The optimization of analytical parameter was performed by response surface method using Box-Behnker and central composite designs. The proposed sequential flow procedure permits to determine up to 10.0 mg SO42- L-1 with RSD <2.5% and limit of detection of 0.27 mg l-1. The method has been successfully applied for sulphate determination in automotive fuel alcohol and the results agreed with the reference volumetric method. In the optimized condition the SIA system carried out 27 samples per hour.

"FIA-near-infrared Spectrofluorimetric Trace Determination Of Hydrogen Peroxide Using Tricarchlorobocyanine Dye (Cy.7.Cl) And Horseradish Peroxidase (HRP)"
Talanta 2005 Volume 68, Issue 3 Pages 876-882
Bo Tang, Li Zhang and Ke-hua Xu

Abstract: A new kind of near-infrared fluorescence agent, tricarbochlorocyanine dye (Cy.7.Cl), had been synthesized in house and used for near-infrared spectrofluorimetric determination of hydrogen peroxide (H2O2) by flow injection analysis (FIA) for the first time. The oxidation reaction of Cy.7.Cl with H2O2 occurred under the catalysis of horseradish peroxidase (HRP) and it was studied in detail. The possible reaction mechanism was discussed. Under optimal experimental conditions, fluorescence from Cy.7.Cl displayed excitation and emission maxima (ex/em) at 780 and 800 nm, respectively. The two linear working ranges were 1.86 x 10^-7 to 4.11 x 10^-7 mol L-1 and 4.11 x 10^-7 to 7.19 x 10^-6 mol L-1, respectively. The detection limit was 5.58 x 10^-8 mol L-1 of H2O2. The effect of interferences was studied. The proposed method was successfully applied to the determination of hydrogen peroxide in rainwater, serum and plant samples.

"Fluorimetric Determination Of Aminocaproic Acid In Pharmaceutical Formulations Using A Sequential Injection Analysis System"
Talanta 2005 Volume 68, Issue 3 Pages 857-862
Paula C.A.G. Pinto, M. L&uacute;cia M.F.S. Saraiva, Jo&atilde;o L.M. Santos and Jos&eacute; L.F.C. Lima

Abstract: A sequential injection analysis (SIA) methodology for the fluorimetric determination of aminocaproic acid in pharmaceutical formulations is proposed. The developed analytical procedure is based on the derivatization reaction of the aminocaproic primary amine with o-phthalaldehyde (OPA) and N-acetylcysteine (NAC) and fluorimetric detection of the formed product (λex = 350 nm; λem = 450 nm). The implementation of a SIA flow system allowed for the development of a simple, fast and versatile automated methodology, which exhibits evident advantages regarding the US Pharmacopoeia 24 (USP 24) reference procedure. By combining the SIA time-based sample insertion with a subsequent zone sampling approach, which permitted to select for detection of a well-defined sample zone, it was possible to implement an on-line dilution strategy that enabled the expansion of the analytical working range of the methodology, and thus its application in dissolution studies, without manifold re-configuration.Linear calibration plots were obtained for aminocaproic acid concentrations up to 6 x 10^-5 mol l-1. The developed methodology exhibit a good precision, with a RSD < 2.0% (n = 15) and the detection limit was 2.5 x 10^-7 mol l-1. The obtained results complied with those furnished by the reference procedure with a relative deviation lower than 1.2%. No interference was found.

"Sequential Injection Lab-on-valve Simultaneous Spectrophotometric Determination Of Trace Amounts Of Copper And Iron"
Talanta 2005 Volume 68, Issue 3 Pages 527-534
Shinsuke Ohno, Norio Teshima, Tadao Sakai, Kate Grudpan and Miroslav Polasek

Abstract: A sequential injection (SI) method in a lab-on-valve (LOV) format for simultaneous spectrophotometric determination of copper and iron has been devised. The detection chemistry is based on the complex formation of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]aniline (5-Br-PSAA) with copper(II) and/or iron(II) at pH 4.6. Copper(II) reacts with 5-Br-PSAA to form the complex which has an absorption maximum at 580 nm but iron(III) does not react. In the presence of a reducing agent only iron(II)-5-Br-PSAA complex is formed and detected at 558 nm. Under the optimum experimental conditions, the determinable ranges are 0.1-2 mg L-1 for copper and 0.1-5 mg L-1 for iron, respectively, with a sampling rate of 18 h-1. The limits of detection are 50 µg L-1 for copper and 25 µg L-1 for iron. The relative standard deviations (n = 15) are 2% for 0.5 mg L-1 copper and 1.8% for 0.5 mg L-1 iron when determined in standard solutions. The recoveries range between 96 and 105% when determining 0.25-2 mg L-1 of copper and 0.2-5 mg L-1 of iron in artificial mixtures at copper/iron ratios of 1:10 to 5:1. The proposed SI-LOV method is successfully applied to the simultaneous determination of copper and iron in multi-element standard solution and in industrial wastewater samples.

"A Simple Strategy For Determining Ethanol In All Types Of Alcoholic Beverages Based On Its On-line Liquid-liquid Extraction With Chloroform, Using A Flow Injection System And Fourier Transform Infrared Spectrometric Detection In The Mid-IR"
Talanta 2005 Volume 68, Issue 2 Pages 470-479
M&aacute;ximo GallignaniCorresponding Author Contact Information, E-mail The Corresponding Author, E-mail The Corresponding Author, Carlos Ayala, Maria del Rosario Brunetto, Jose Luis Burguera and Marcela Burguera

Abstract: In this work, a simple strategy for the determination of ethanol in all types of alcoholic beverages using Fourier transform infrared spectrometric detection has been developed. The methodological proposal includes the quantitative on-line liquid-liquid extraction of ethanol with chloroform, through a sandwich type cell equipped with a PTFE membrane, using a two-channel manifold; and direct measurement of the analyte in the organic phase, by means of Fourier transform infrared spectrometry. The quantification was carried out measuring the ethanol absorbance at 877 cm-1, corrected by means of a baseline established between 844 and 929 cm-1. The procedure, which does not require any sample pretreatment (except for the simple degassing of beer and gassy wine samples, and a simple dilution of spirits with water), was applied to determine ethanol in different alcoholic beverages such as beers, wines and spirits. The results obtained highly agree with those obtained by a derivative FTIR spectrometric procedure, and by head space-gas chromatography with FID detection. The proposed method is simple, fast, precise and accurate. Moreover, it can be easily adapted to any infrared spectrometer equipped with a standard transmission IR cell, and provides attractive analytical features, which are comparable to, or better than those offered by other published methods. In consequence, it represents a valid alternative for the determination of ethanol in alcoholic beverages, and could be suitable for the routine control analysis. © 2005 Elsevier B.V. All rights reserved.

"Speciation Of Mercury In Salmon Egg Cell Cytoplasm In Relation With Metallomics Research"
Talanta 2005 Volume 68, Issue 2 Pages 465-469
Takuya Hasegawa, Motoki Asano, Kohei Takatani, Hirotaka Matsuura, Tomonari Umemura and Hiroki Haraguchi

Abstract: Speciation of mercury in salmon egg cell cytoplasm was investigated by surfactant-mediated high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICP-MS), where an ODS (octadecylsilica) column coated with a bile acid derivative, CHAPS (3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate), was used for species separation. Prior to the speciation analysis, total Hg in the cell cytoplasm was determined by ICP-MS at m/z 202 in a flow injection mode. For the precise measurement, salmon egg cell cytoplasm was diluted five-fold with 0.1 M Tris (Tris(hydroxymethyl)aminomethane)-HNO3 buffer solution, and the standard addition method was employed. Thus, the total concentration of Hg in cell cytoplasm was estimated to be 12.4 ng g-1 on the wet weight basis. Next, the cell cytoplasm diluted five-fold with 0.1 M Tris-HNO 3 buffer solution was analyzed by surfactant-mediated HPLC with the dual detection system of a UV absorption detector and an ICP-MS instrument. Two peaks corresponding to some proteins and small molecules were mainly observed in those chromatograms. When salmon egg cell cytoplasm was diluted five-fold with 0.01 M Tris buffer solution or pure water, some precipitates appeared probably because of precipitation of hydrophobic proteins in cytoplasm. After the precipitates were eliminated with a membrane filter, the filtrate was subjected to the analysis by surfactant-mediated HPLC/UV/ICP-MS. As a result, the peaks for small molecular species of Hg were clearly observed at the retention time near 4.0 min (corresponding to low-molecular weight zone) in the chromatograms with UV absorption detection as well as with Hg- and S-specific ICP-MS detections. The small molecule bound with Hg was identified as cysteine through the cysteine-spiked experiment. In addition, the protein fraction on the chromatogram obtained by using the CHAPS-coated ODS column was further analyzed by SEC (size exclusion chromatography). Consequently, several protein peaks with molecular weight of 300, 50 and 12 kDa were observed in all the detections of UV absorption, Hg and Se, although two peaks among them were coincident in the case of S. These results indicate that Hg in salmon egg cell cytoplasm binds with proteins containing selenocysteine and/or cysteine residues in proteins. © 2005 Elsevier B.V. All rights reserved.

"A Novel Stopped Flow Injection - Amperometric Procedure For The Determination Of Chlorate"
Talanta 2005 Volume 68, Issue 2 Pages 459-464
Orawan Tue-Ngeun, Jaroon Jakmunee and Kate Grudpan

Abstract: A novel stopped flow injection - amperometric (sFI-Amp) procedure for determination of chlorate has been developed. The reaction of chlorate with excess potassium iodide and hydrochloric acid, forming iodine/triiodide that is further electrochemically reduced at a glassy carbon electrode at +200 mV versus Ag/AgCl electrode is employed. In order to increase sensitivity without using of too high acid concentration, promoting of the reaction by increasing reaction time and temperature can be carried out. This can be done without increase of dispersion of the product zone by stopping the flow while the injected zone is being in a mixing coil which is immersed in a water bath of 55 ± 0.5°C. In a closed system of FIA, a side reaction of oxygen with iodide is also minimized. Under a set of conditions, linear calibration graphs were in the ranges of 1.2 x 10^-6-6.0 x 10^-5 mol l-1and 6.0 x 10^-5-6.0 x 10^-4 mol l-1. A sample throughput of 25 h-1 was accomplished. Relative standard deviation was 2% (n = 21, 1.2 x 10^-4 mol L-1 chlorate). The proposed sFI-Amp procedure was successfully applied to the determination of chlorate in soil samples from longan plantation area. © 2005 Elsevier B.V. All rights reserved.

"Rapid And Reagent-saving Immunoassay Using Innovative Stirring Actions Of Magnetic Beads In Microreactors In The Sequential Injection Mode"
Talanta 2005 Volume 68, Issue 2 Pages 437-441
K. Tanaka and H. Imagawa

Abstract: We developed new ELISA techniques in sequential injection analysis (SIA) mode using microreactors with content of a few microliters. We immobilized antibodies on magnetic beads 1.0 ?m in diameter, injected the beads into microreactors and applied rotating magnetic fields of several hundred gauss. Magnetic beads, suspended in liquid in density of approximately 10 9-1010 particles per millilitre, form a large number of thin rod clusters, whose length-wise axes are oriented in parallel with the magnetic field. We rotate the Nd magnets below the center of the microreactor by a tiny motor at about 2000-5000 rpm. These rotating clusters remarkably accelerate the binding rate of the antibodies with antigens in the liquid. The beads are trapped around the center of the rotating magnetic field even in the flowing liquid. This newly found phenomenon enables easy bead handling in microreactors. Modification of reactor walls with selected blocking reagents was essential, because protein-coated beads often stick to the wall surface and cannot move freely. Washing steps were also shortened. © 2005 Elsevier B.V. All rights reserved.

"Microfluidic Cells With Interdigitated Array Gold Electrodes: Fabrication And Electrochemical Characterization"
Talanta 2005 Volume 68, Issue 2 Pages 429-436
Daniela Daniel and Ivano G.R. Gutz

Abstract: Microfluidic flow cells combined with an interdigitated array (IDA) electrode and/or individually driven interdigitated electrodes were fabricated and characterized for application as detectors for flow injection analysis. The gold electrodes were produced by a process involving heat transfer of a toner mask onto the gold surface of a CD-R and etching of the toner-free gold region by short exposure to iodine-iodide solution. The arrays of electrodes with individual area of 0.01 cm2 (0.10 cm of length x 0.10 cm of width and separated by gaps of 0.05 or 0.03 cm) were assembled in microfluidic flow cells with 13 or 19 ?m channel depth. The electrochemical characterization of the cells was made by voltammetry under stationary conditions and the influence of experimental parameters related to geometry of the channels and electrodes were studied by using K4Fe(CN) 6 as model system. The obtained results for peaks currents (I p) are in excellent agreement with the expected ones for a reversible redox system under stationary thin-layer conditions. Two different configurations of the working electrodes, Ei, auxiliary electrode, A, and reference electrode, R, on the chip were examined: Ei/R/A and R/Ei/A, with the first presenting certain uncompensated resistance. This is because the potentiostat actively compensates the iR drop occurring in the electrolyte thin layer between A and R, but not from R to each E i. This is confirmed by the smaller difference between the cathodic and anodic peak potentials for the second configuration. Evaluation of the microfluidic flow cells combined with (individually driven) interdigitated array electrodes as biamperometric or amperometric detectors for FIA reveals stable and reproducible operation, with peak heights presenting relative standard deviations of less than 2.2%. For electrochemically reversible species, FIA peaks with enhanced current signal were obtained due to redox cycling under flow operation. The versatility of microfluidic flow cells, produced by simple and low-cost technique, associated with the rich information content of electrochemical techniques with arrays of electrodes, opens many future research and application opportunities. © 2005 Elsevier B.V. All rights reserved.

"A Downsized Flow Set Up Based On Multicommutation For The Sequential Photometric Determination Of Iron(II)/iron(III) And Nitrite/nitrate In Surface Water"
Talanta 2005 Volume 68, Issue 2 Pages 422-428
M&aacute;rio Almir Feres and Boaventura F. Reis

Abstract: In this work, a downsized flow set up designed based on multicommutation concept for photometric determination of iron(II)/iron(III) and nitrite/nitrate is surface water is described. The flow system network comprised a set of three-way solenoid valves, reaction coil and a double-channel flow cell, which were nested in order to obtain a compact and small-size instrument. To accomplish the downsizing requirement light source (LED) and radiation detection (phototransistor) were coupled to the flow cell. In order to demonstrated the effectiveness of the system, the photometer methods based on Griess reaction and 1-10-phenantroline for nitrite and iron(II) determination, respectively, were selected. Under computer control the set up provided facilities to handle four reagent solutions employing a single pumping channel, thus permitting also the determination of nitrate and iron(III) after its reduction to nitrite and to iron(II), respectively. The overall system performance was demonstrated working several days running standard solution, no significant variation of base line, linear response range and slop (less than 1%) were observed. The usefulness of the downsized system was ascertained by analyzing a set of surface water. Aiming to access the accuracy sample were also analyzed employing reference procedures and no significant difference at 95% confidence level were observed for the four analytes. Other profitable features such as analytical throughput of 40 determination per hour; relative standard deviation of 1%; linear response range between 50 and 300 ?g l -1 for nitrite and nitrate, 0.5-6.0 mg L-1 iron(II) and iron(III); low reagent consumption 75 ?g for nitrate/nitrite and 0.6 mg for iron(II)/iron(III) per determination; and 2.4 mL waste generation per determination were also achieved. © 2005 Elsevier B.V. All rights reserved.

"Exploiting Sequential Injection Analysis With Lab-at-valve (LAV) Approach For On-line Liquid-liquid Micro-extraction Spectrophotometry"
Talanta 2005 Volume 68, Issue 2 Pages 416-421
Rodjana Burakham, Somchai Lapanantnoppakhun, Jaroon Jakmunee and Kate Grudpan

Abstract: Sequential injection analysis (SIA) with lab-at-valve (LAV) approach for on-line liquid-liquid micro-extraction has been exploited. Sample, reagent and organic solvent were sequentially aspirated into a coil attached to a central port of a conventional multiposition selection valve, where the extraction process was performed. The aqueous and organic phases were separated in a conical separating chamber LAV unit attached at one port of the valve. The organic phase containing extracted product was then monitored spectrophotometrically. The system offers a novel alternative on-line automated extraction in a micro-scale and has been successfully demonstrated for the assays of diphenhydramine hydrochloride (DPHH) in pharmaceutical preparations and anionic surfactant in water samples. © 2005 Published by Elsevier B.V.

"Sequential Injection Spectrophotometric Determination Of Ritodrine Hydrochloride Using 4-aminoantipyrine"
Talanta 2005 Volume 68, Issue 2 Pages 401-405
Jacobus F. van Staden, Negussie W. Beyene, Raluca-Ioana Stefan and Hassan Y. Aboul-Enein

Abstract: A sequential injection spectrophotometric determination of ritodrine hydrochloride is described. The method is based on the condensation of aminoantipyrine with phenols in the presence of an alkaline oxidizing agent to yield a pink colored product the absorbance of which is monitored at 503 nm. Different sequential injection analysis (SIA) parameters including reagent concentrations have been optimized and used to obtain the analytical figures of merit. A linear concentration range of 3.1-123.5 ?mol L-1 and a detection limit (as 3?-value) of 1.0 ?mol L-1 were obtained. The precision was 2.4 and 2.3% relative standard deviation (RSD) at 6.2 and 15.4 ?mol L-1, respectively. This method is superior over previously reported ones in terms of linear range, short analysis time, high sample throughput, excellent reagent economy and minimum waste generation. © 2005 Published by Elsevier B.V.

"Batch-injection Stripping Voltammetry (tube-less Flow-injection Analysis) Of Trace Metals With On-line Sample Pretreatment"
Talanta 2005 Volume 68, Issue 2 Pages 394-400
Marek Trojanowicz, Przemys&#322;aw Ko&#378;mi&#324;ski, Humberto Dias and Christopher M.A. Brett

Abstract: The most essential limitation of batch-injection analysis (BIA) methodology compared to other flow methods (CFA, FIA, SIA) is the lack of possibility of on-line sample processing in the measuring system. Some procedures of on-line sample pretreatment in BIA are possible by changing the plastic tip of the automatic micropipette used for sample injection into a flow-through reactor, e.g. by packing it with a bed of a solid sorbent. This concept is employed in the voltammetric stripping determinations of trace metals using a bed of commercial chelating resin Chelex-100. It was found that, besides the electrochemical pre-concentration of analytes in the form of amalgams on the surface of mercury thin film electrodes, an approximately 10-fold additional pre-concentration can be achieved on the packed sorbent bed by using different volumes of aspirated sample solution and eluent. This procedure allows also efficient elimination of some matrix effects. © 2005 Elsevier B.V. All rights reserved.

"On-line Generation And Hydrolysis Of Methyl Borate For The Spectrophotometric Determination Of Boron In Soil And Plants With Azomethine-H"
Talanta 2005 Volume 68, Issue 2 Pages 374-381
Pablo Carrero, Auristela Malav&eacute;, Edyleiba Rojas, Carlos Rond&oacute;n, Yaneira Petit de Pe&ntilde;a, Jos&eacute; Luis Burguera and Marcela Burguera

Abstract: A continuous-flow system for boron determination in soils and plants with spectrophotometric detection using the azometihine-H-boron complex method was developed. In order to avoid the interferences of concomitants present in samples and to increase the sensitivity, the element was separated on-line from the matrix by methyl borate generation. For this purpose, a concentrated sulfuric acid sample solution was combined with methanol in 1:3 ratio which produce enough heating for the esterification reaction without external source. Subsequently, the methyl borate produced was stripped by the addition of a nitrogen flow and separated from the bulk solution in a gas-liquid separator to be then hydrolyzed in an ammonium-phosphate buffer solution (pH 6.8). Finally, the new bulk of phases were separated in a second gas-liquid separator and the liquid phase was combined with azomethine-H to form a boron complex for its detection at 420 nm. The effects of a number of possible interferents, both anionic and cationic were evaluated. The most severe depressions were caused by fluoride and potassium for which a concentration of 100 ?g mL-1 caused a 5% depression on the signal. A linear response was obtained between the detection limit of 0.05 ?g mL-1 (3? of the blank) and 50 ?g mL-1 of boron. The precision (RSD%) for 10 consecutive readings of the same solution (5.0 ?g mL-1 of boron) was 2.6%. Recoveries of boron added to the samples before the extraction process were 94, 97, and 101% for soil, fruit tissue, and leaf tissue, respectively. The developed system was applied to the determination of boron in soil, fruits tissue, and leaves tissue of coffee plantations from different towns of Me?rida State, Venezuela. © 2005 Elsevier B.V. All rights reserved.

"Single Reaction Interface In Flow Analysis"
Talanta 2005 Volume 68, Issue 2 Pages 351-358
Marta F.T. Ribeiro, Jo&atilde;o L.M. Santos, Jos&eacute; L.F.C. Lima, Ana C.B. Dias and Elias A.G. Zagatto

Abstract: The dual or multiple reaction interface concept, commonly associated to the distinct flow techniques, was replaced by a single interface concept, which do not no rely on the utilisation of a well-defined and compelling sample volume but only on mutual penetration of sample and reagent zones at a single reaction interface where both sample and reagent met together prior to detection. In the proposed approach basic principles of flow analysis, such as controlled dispersion and reaction zone formation, are not influenced by sample and reagent volumes but determined exclusively by the extension of the overlap of two adjoining quasi-infinite zones enhanced by multiple flow reversals and the pulsed nature of the flowing streams. The detector is positioned at the core of the flow manifold (not in the conventional terminal position), and repetitive flow reversals enable interface manipulations, including multi-detection of the entire reaction interface or the monitoring of the evolution of a pre-selected interface zone by using suitable reversal cycle times. The implementation of the developed approach was facilitated due to the configuration simplicity and operational versatility of multi-pumping flow systems. Its performance was evaluated by monitoring processes involving two or four-solution reaction interfaces. © 2005 Elsevier B.V. All rights reserved.

"Interfacing In-line Gas-diffusion Separation With Optrode Sorptive Preconcentration Exploiting Multisyringe Flow Injection Analysis"
Talanta 2005 Volume 68, Issue 2 Pages 343-350
Laura Ferrer, Graciela de Armas, Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: An automatic multisyringe flow injection analysis (MSFIA) system coupling a flow-through optical fiber diffuse reflectance sensor with in-line gas-diffusion (GD) separation is proposed for the isolation, pre-concentration and determination of traces of volatile and gas-evolving compounds in samples containing suspended solids, with no need for any preliminary batch sample treatment. The flowing methodology overcomes the lost of sensitivity of the in-line separation technique, when performed in a uni-directional continuous-flow mode, through the implementation of disk-based solid-phase extraction schemes. The high selectivity and sensitivity, the low reagent consumption and the miniaturization of the whole assembly are the outstanding features of the automated set-up. The proposed combination of techniques for separation, flow analysis, pre-concentration and detection was applied satisfactorily to sulfide determination in environmental complex matrixes. The method based on multicommutation flow analysis involves the stripping of the analyte as hydrogen sulfide from the donor channel of the GD-module into an alkaline receiver segment, whereupon the enriched plug merges with well-defined zones of the chormogenic reagents (viz., N,N-dimethyl-p-phenylenediamine (DMPD) and Fe(III)). The in-line generated methylene blue dye is subsequently delivered downstream to the dedicated optrode cell furnished with a C18 disk, while recording continuously the diffuse reflectance spectrum of the pre-concentrated compound. This procedure provides a linear working range of 20-500 µg l-;1 sulfide with a relative standard deviation of 2.2% (n = 10) at the 200 µg L-;1 level, and a detection limit of 1.3 µg L-;1.
Sulfide Sea Ground Waste Optrode Gas diffusion Preconcentration Multisyringe Multicommutation

"Preconcentration And Speciation Of Inorganic And Methyl Mercury In Waters Using Polyaniline And Gold Trap-CVAAS"
Talanta 2005 Volume 68, Issue 2 Pages 329-335
M.V. Balarama Krishna, D. KarunasagarCorresponding Author Contact Information, E-mail The Corresponding Author, S.V. Rao and J. Arunachalam

Abstract: Applicability of polyaniline (PANI) has been investigated for the pre-concentration and speciation of inorganic mercury (Hg2+) and methyl mercury (CH3Hg+) in various waters (ground, lake and sea waters). Preliminary experiments (batch) with powdered PANI for the quantitative removal of both Hg2+ and CH3Hg+ showed that the retention of Hg2+ was almost independent of pH while a pH dependent trend from pH 1 to 12 was seen for CH3Hg+ with maximum retention at pH > 5. Time dependence batch studies showed that a contact time of 10 min was sufficient to reach equilibrium. The Kd values were found to be ?8 x 104 and ?7 x 10 3 for Hg2+ and CH3Hg+, respectively. Subsequently column experiments were carried out with PANI and the separation of the species was carried out by selective and sequential elution with 0.3% HCl for CH3Hg+ and 0.3% HCl-0.02% thiourea for Hg 2+. This was then followed by further pre-concentration of mercury on a gold trap and its determination by CVAAS. The uptake efficiency studies showed that the PANI column was able to accumulate up to 100 mg Hg 2+/g and 2.5 mg CH3Hg+/g. This method allows both pre-concentration and speciation of mercury with pre-concentration factors around 120 and 60 for Hg2+ and CH3Hg+, respectively. The interfering effects of various foreign substances on the retention of mercury were investigated. © 2005 Elsevier B.V. All rights reserved.

"The Chromatomembrane Method Used For Sample Preparations In The Spectrophotometric Determination Of Zinc And Copper In Pharmaceuticals"
Talanta 2005 Volume 68, Issue 2 Pages 318-322
Ganden Supriyanto and J&uuml;rgen Simon

Abstract: The chromatomembrane cell (CMC) was used to extract zinc and copper and to pre-concentrate them for their separation from pharmaceutical preparations. The method performance was evaluated at the determination of the enrichment factor, the linearity of response, the reproducibility, the accuracy and the sensitivity. In practice a five-fold enrichment has been enough provided that sample sizes of 0.825 mL were introduced. Good linearities for zinc and copper (r2 > 0.99) were observed under this condition. The relative standard deviation (<3%) proved the good reproducibility of the method. The accuracy has been verified using model solutions, which were prepared from a certified reference. Recoveries of 98.8, 99.5 and 100.3% were achieved with solutions containing 0.1, 0.3 and 0.5 ?g mL-1 Zn(II), respectively. In case of copper 101.2, 99.6 and 100.6% recovery were obtained for 0.1, 0.4 and 0.7 ?g mL-1 Cu(II), respectively. The detection limits (three-fold of the signal-to-noise ratio) were estimated at 0.04 ?g mL-1 for both. The proposed method was applied on pharmaceutical preparations and the results were found to be in a good agreement with the contents guaranteed by the producers. © 2005 Elsevier B.V. All rights reserved.

"Flow-injection Photometric Determination Of Manganese(II) Based On Its Catalysis Of The Periodate Oxidation Of N,N-bis(2-hydroxy-3-sulfopropyl)tolidine"
Talanta 2005 Volume 68, Issue 2 Pages 312-317
Shigenori NakanoCorresponding Author Contact Information, E-mail The Corresponding Author, Yuko Matumoto1 and Masahiro Yoshii

Abstract: A novel flow-injection spectrophotometric method has been developed for the determination of manganese(II) at sub-nanogram/ml levels. The method is based on its catalytic effect on the oxidation of N,N?-bis(2-hydroxy-3-sulfopropyl)tolidine (HSPT) by periodate. The catalytic effect of manganese(II) was enhanced by the presence of 2,2?-bipyridine as an activator. By monitoring the change in absorbance of the oxidation product of HSPT at 670 nm, manganese(II) ranging 0.02-3.0 ng mL-1 could be determined with the relative standard deviations of less than 2%. The interfering ions were effectively suppressed by the addition of 2,2?-iminodiethanol and citric acid. The proposed method is directly applicable to the determination of manganese in lake and river water samples. © 2005 Elsevier B.V. All rights reserved.

"On-line Preconcentration And Speciation Of Arsenic By Flow Injection Hydride Generation Atomic Absorption Spectrophotometry"
Talanta 2005 Volume 68, Issue 2 Pages 298-304
Cristine Ingrid S. Narcise, Lilibeth dlC. CooCorresponding Author Contact Information, E-mail The Corresponding Author and Florian R. del Mundo

Abstract: A flow injection-column pre-concentration-hydride generation atomic absorption spectrophotometric (FI-column-HGAAS) method was developed for determining ?g/l levels of As(III) and As(V) in water samples, with simultaneous pre-concentration and speciation. The speciation scheme involved determining As(V) at neutral pH and As(III + V) at pH 12, with As(III) obtained by difference. The enrichment factor (EF) increased with increase in sample loading volume from 2.5 to 10 ml, and for pre-concentration using the chloride-form anion exchange column, EFs ranged from 5 to 48 for As(V) and 4 to 24 for As(III + V), with corresponding detection limits of 0.03-0.3 and 0.07-0. 3 ?g/l. Linear concentration range (LCR) also varied with sample loading volume, and for a 5 mL sample was 0.3-5 and 0.2-8 ?g/l for As(V) and As(III + V), respectively. Sample throughput, which decreased with increase in sample volume, was 8-17 samples/h. For the hydroxide-form column, the EFS for 2.5-10 mL samples were 3-23 for As(V) and 2-15 for As(III + V), with corresponding detection limits of 0.07-0.4 and 0.1-0.5 ?g/l. The LCR for a 5 mL sample was 0.3-10 ?g/l for As(V) and 0.2-20 ?g/l for As(III + V). Sample throughput was 10^-20 samples/h. The developed method has been effectively applied to tap water and mineral water samples, with recoveries ranging from 90 to 102% for 5 mL samples passed through the two columns. © 2005 Elsevier B.V. All rights reserved.

"Coupling On-line Of A Dialyser With A Flow-continuous System To Separate Vitamin B12 From Milk"
Talanta 2005 Volume 68, Issue 2 Pages 292-297
Gustavo Medina-Alonso, Minerva Carrasco-Fuentes and Mar&iacute;a del Pilar Ca&ntilde;izares-Mac&iacute;as

Abstract: The use of membranes for on-line separations in flow-through dialyser as a part of a flow system is extremely useful for automated samples preparation. In this paper a method to couple the dialysis and the UV detection on-line of Vitamin B12 from milk is proposed. Firstly, the milk samples were pre-treated with trichloroacetic and centrifuged (to eliminate proteins and fats) and later, using a dialyser coupled a flow-continuous manifold was possible dialyse the Vitamin B12, which was monitored spectrophotometrically at 361 nm. On the other hand, the milk samples were also dialysed on-line but without the acid treatment and the results were compared. The influence of various parameters, including the pump speed for both the donor and acceptor stream, dialysis time, donor and acceptor loop volume on dialysis efficiency was studied. The method was applied to different kinds of milk (skimmed and semi-skimmed milk, evaporated milk, lactose free milk and liquid and powder whole milk). The relative standard deviation (RSD) of the proposed method was of 0.45% and the obtained dialysis percentage was of 5.8%. The proposed method very easy permit a pre-treatment of the sample, quick and on-line with the detection. The dialysis process permitted the pass of vitamin and avoided the pass of other analytes as proteins in the case of the milk samples without acid treatment. © 2005 Elsevier B.V. All rights reserved.

"Rapid Determination Of Lead Extracted By Acetic Acid From Glazed Ceramic Surfaces By Flow Injection On-line Preconcentration And Spectrophotometric Detection"
Talanta 2005 Volume 68, Issue 2 Pages 287-291
Mai Kuramochi, Kenichi Tomioka, Masanori Fujinami and Koichi Oguma

Abstract: A rapid method has been developed for the determination of lead extracted by acetic acid from glazed ceramic surfaces by flow injection analysis without any pretreatment. An aliquot of 4% acetic acid solution, which has been kept in a teacup for 24 h in the dark, is injected into a carrier solution (1 M nitric acid) and passed through a Pb-Spec resin column. After washing the column with an ammonium nitrate solution, the lead adsorbed on the column is eluted with an ammonium oxalate solution and then merged with a 4-(2-pyridylazo)resorcinol (PAR) solution, followed by measurement of the absorbance of the lead-PAR complex at 530 nm. The detection limit, concentration giving a signal equal to three times the standard deviation of the blank signal, is 8 ng mL -1. The relative standard deviation of measurements at the 0.8 ?g mL-1 level is 0.35% (n = 5). The sample throughput is 12 per hour. © 2005 Elsevier B.V. All rights reserved.

"Clean Analytical Methodology For The Determination Of Lead With Arsenazo III By Cyclic Flow-injection Analysis"
Talanta 2005 Volume 68, Issue 2 Pages 281-286
Michio ZenkiCorresponding Author Contact Information, E-mail The Corresponding Author, Kazuyoshi Minamisawa and Takashi Yokoyama

Abstract: A clean analytical methodology, where the sample determined and the reagent used are both toxic, has been proposed. A cation exchange mini-column was incorporated after the flow-through cell for on-line regeneration of the main reagent and the accumulation of heavy metal ions. The method involves the spectrophotometric determination of lead with Arsenazo III, the accumulation of lead onto the cationic exchanger, and subsequent regeneration of the chromogenic reagent, which makes the system reversible and the reagents reusable. The developed method provides a satisfactory way to cut down on the toxic reagent consumption and the produced volume of waste, an important step towards the zero emissions research initiative concept. The excellent repeatability and reproducibility, and the simplicity of this method are well suited for continuous measurements. The method was successively applied to the assay of lead in high-octane gasoline. © 2005 Elsevier B.V. All rights reserved.

"Determination Of Trace Amounts Of Bromide By Flow Injection/stopped-flow Detection Technique Using Kinetic-spectrophotometric Method"
Talanta 2005 Volume 68, Issue 2 Pages 274-280
K. Uraisin, D. Nacapricha, S. Lapanantnoppakhun, K. Grudpan and S. Motomizu

Abstract: A simple, sensitive and selective method for the determination of bromide in seawater by using a flow injection/stopped-flow detection technique was examined. The detection system was developed for a new kinetic-spectrophotometric determination of bromide in the presence of chloride matrix without any extraction and/or separation. The detection was based on the kinetic effect of bromide on the oxidation of methylene blue (MB) with hydrogen peroxide in a strongly acidic solution. Large amounts of chloride could enhance the sensitivity of the method as an activator. The decolorisation of the blue color of MB was used for the spectrophotometric determination of bromide at 746 nm. A stopped-flow approach was used to improve the sensitivity of the measurement and provide good linearity of the calibration over the range of 0-3.2 ?g mL-1 of bromide. The relative standard deviation was 0.74% for the determination of 2.4 ?g mL-1 bromide (n = 5). The detection limit (3?) was 0.1 ?g mL-1 with a sampling frequency of 12 h-1. The influence of potential interfering ions was studied. The proposed method was applied to the determination of bromide in seawater samples and provided satisfactory results. © 2005 Elsevier B.V. All rights reserved.

"Gas Diffusion Sequential Injection System For The Spectrophotometric Determination Of Free Chlorine With O-dianisidine"
Talanta 2005 Volume 68, Issue 2 Pages 268-273
Raquel B.R. Mesquita and Ant&oacute;nio O.S.S. Rangel

Abstract: A gas diffusion sequential injection system for spectrophotometric determination of free chlorine is described. The detection is based in the colorimetric reaction between free chlorine and a low toxicity reagent o-dianisidine. A gas diffusion unit is used to isolate free chlorine from the sample in order to avoid possible interferences. This feature results from the conversion of free chlorine to molecular chlorine (gaseous) with sample acidification. With minor changes in the operating conditions, two different dynamic ranges were obtained enhancing the application both to water samples and bleaches. The results obtained with the developed system were compared to the reference method, iodometric titration and proved not to be statistically different. A detection limit of 0.6 mg ClO-/L was achieved. Repeatability was evaluated from 10 consecutive determinations being the results better than 2%. The two dynamic ranges presented different determination rates: 15 h-1 for 0.6-4.8 mg ClO-/L (water samples) and 30 h-1 for 0.047-0.188 g ClO-/L (bleaches). © 2005 Elsevier B.V. All rights reserved.

"Exploiting Guava Leaf Extract As An Alternative Natural Reagent For Flow Injection Determination Of Iron"
Talanta 2005 Volume 68, Issue 2 Pages 262-267
Thapanon Settheeworrarit, Supaporn Kradtap Hartwell, Somchai Lapanatnoppakhun, Jaroon Jakmunee, Gary D. Christian and Kate Grudpan

Abstract: Guava leaf extract is utilized as an alternative natural reagent for quantification of iron. The flow injection technique enables the use of the extract in acetate buffer solution without the need of further purification. Some properties of the extract such as its stability and ability to form a colored complex with iron were studied. The proposed system is an environmentally friendly method for determination of iron with less toxic chemical wastes. © 2005 Elsevier B.V. All rights reserved.

"Automated Portable Analyzer For Lead(II) Based On Sequential Flow Injection And Nanostructured Electrochemical Sensors"
Talanta 2005 Volume 68, Issue 2 Pages 256-261
Wassana Yantasee, Charles Timchalk, Glen E. Fryxell, Brian P. Dockendorff and Yuehe Lin

Abstract: A fully automated portable analyzer for toxic metal ion detection based on a combination of a nanostructured electrochemical sensor and a sequential flow injection system has been developed in this work. The sensor was fabricated from a carbon paste electrode modified with acetamide phosphonic acid self-assembled monolayer on mesoporous silica (Ac-Phos SAMMS) which was embedded in a very small wall-jet (flow-onto) electrochemical cell. The electrode is solid-state and mercury-free. Samples and reagents were injected into the system and flowed through the electrochemical cell by a user programmable sequential flow technique which required minimal volume of samples and reagents and allowed the automation of the analyzer operation. The portable analyzer was evaluated for lead (Pb) detection due to the excellent binding affinity between Pb and the functional groups of Ac-Phos SAMMS as well as the great concern for Pb toxicity. Linear calibration curve was obtained in a low concentration range (1-25 ppb of Pb(II)). The reproducibility was excellent; the percent relative standard deviation was 2.5 for seven consecutive measurements of 10 ppb of Pb(II) solution. Excess concentrations of Ca, Ni, Co, Zn, and Mn ions in the solutions did not interfere with detection of Pb, due to the specificity and the large number of the functional groups on the electrode surface. The electrode was reliable for at least 90 measurements over 5 days. This work is an important milestone in the development of the next-generation metal ion analyzers that are portable, fully automated, and remotely controllable. © 2005 Elsevier B.V. All rights reserved.

"Reagents Regeneration Flow Injection Analysis (RRFIA) For Spectrophotometric Determination Of Methamphetamine Coupled With Solvent Extraction"
Talanta 2005 Volume 68, Issue 2 Pages 253-255
Norio Teshima, Nobukazu Fukui and Tadao Sakai

Abstract: Methamphetamine (MPA), being a stimulant drug, reacts with tetrabromophenolphthalein ethyl ester (TBPEH) to form a red-violet ion associate, TBPEHMPA, in 1,2-dichloroethane (DCE) at pH 9. The maximum absorption wavelength was at 570 nm. After measuring, yellow TBPEH with DCE could be regenerated by mixing with the buffer solution at pH 3. The regenerated TBPEH/DCE could be reused as an ion association reagent and extracting solvent. In addition, the reagent regeneration could be performed by the on-line flow injection system and the cyclic flow injection analysis system was demonstrated for the determination of MPA without consumption of ion association reagent and organic solvent. The calibration curve was linear in the range of 0.5-3.5 x 10^-5 M with good repeatability. The sample throughput was 20 h-1. © 2005 Elsevier B.V. All rights reserved.

"Autoadaptative Sequential Injection System For Nitrite Determination In Wastewaters"
Talanta 2005 Volume 68, Issue 2 Pages 245-252
M. Baeza, J. Bartrol&iacute; and J. Alonso

Abstract: A novel autoadaptative sequential injection system for the analysis of nitrite is described. The automatic determination uses a direct spectrophotometric method, based on the Griess-Ilosvay reaction. In this method the absorbance of the purple azo dye formed is measured at 555 nm. In the sequential injection operation, the sample and the reagent are aspirated and mixed by reverse flow. The sequencing and overlapping of stacked (reagent) zones as well as selection of volumes have been studied in detail. The proposed analytical system is intelligent, simple and robust, allowing for nitrite determination in a double concentration range, by a simple and automatic programmable operation change. These two ranges are 0.0-3.0 and 0.0-20.0 ppm with detection limits being 0.048 and 0.4 ppm, respectively. Next surroundings have been developed allowing autocalibration and independent monitoring of nitrite concentration. The experimental set-up has been evaluated applying it to real samples analysis of very diverse concentration samples coming from a WWTP. The throughput of the method was 12 samples per hour. © 2005 Elsevier B.V. All rights reserved.

"Sequential Injection Chemiluminescence Immunoassay For Anionic Surfactants Using Magnetic Microbeads Immobilized With An Antibody"
Talanta 2005 Volume 68, Issue 2 Pages 231-238
RuiQi Zhang, Koji Hirakawa, Daisuke Seto, Nobuaki Soh, Koji Nakano, Takashi Masadome, Kazumi Nagata, Kazuhira Sakamoto and Toshihiko Imato

Abstract: A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0-500 ppb) under optimum conditions. The time required for analysis is less than 15 min.

"Sensitive Sequential Injection Determination Of Naproxen Based On Interaction With -cyclodextrin"
Talanta 2005 Volume 68, Issue 2 Pages 226-230
Eftychia-Pavlina Zisiou, Paula C.A.G. Pinto, M. L&uacute;cia M.F.S. Saraiva, Christophe Siquet and Jos&eacute; L.F.C. Lima

Abstract: A sensitive sequential injection analysis (SIA) methodology for the fluorimetric determination of naproxen is proposed. The developed automatic analytical procedure is based on the complexation of naproxen with ?-cyclodextrin (?-CD) yielding an enhanced fluorimetric signal (?ex = 280 nm, ?em = 356 nm). Linear calibration plots were obtained for naproxen concentrations up to 1 x 10^-5 mol l-1. The developed methodology exhibited a good precision, with a RSD < 2.1% (n = 15). The detection limit of the determination was 1.9 x 10^-7 mol L-1 with a sampling rate of about 70 h-1. The automatic method was applied to the determination of naproxen in pharmaceutical formulations. The obtained results were compared with those furnished by the reference procedure and the relative deviations were lower than 3.6%. No interference was found from the excipients usually used in solid pharmaceutical formulations. © 2005 Elsevier B.V. All rights reserved.

"On-line Electrochemical Preconcentration And Flame Atomic Absorption Spectrometric Determination Of Manganese In Urine Samples"
Talanta 2005 Volume 68, Issue 2 Pages 219-225
Marcela Burguera, Jos&eacute; Luis Burguera, Darveris Rivas, Carlos Rond&oacute;n, Pablo Carrero, Oscar M. Alarc&oacute;n, Yaneira Petit de Pe&ntilde;a, Maria R. Brunetto, M&aacute;ximo Gallignani, Olga P. M&aacute;rquez, et al.

Abstract: A sensitive and selective method was developed for the determination of traces of manganese in urine using on-line electrochemical pre-concentration followed by flame atomic absorption spectrometry detection. A home made flow-through polypropylene cell (4.5 cm long x 0.8 cm diameter filled with glass marbles) with an effective inner volume of 0.5 mL containing a working and a counter electrode, both of glassy carbon and a Pt pseudo reference electrode was located in a flow injection manifold specially designed for the purpose of this work. The manganese was deposited from buffer solution of NH3/NH4Cl at pH 9.00 through an oxidizing process at a current of 400 mA during 7 min. A flow of HCl 0.1 mol L-1 at 4 mL min-1 through the cell, chemically dissolved the deposit. A small portion (15 µL) of the concentrate was introduced in a continuously flowing system by means of a timing device and was then carried to the detector for the manganese quantification. All electrochemical and spectroscopic variables as well as possible interferences in both systems were systematically studied. The relative standard deviations for ten consecutive measurements of manganese solutions of 2.0 and 20 ?g L-1 were of 2.3 and 1.5%, respectively, while for a sample processed five times was less then 5%. The accuracy of the developed procedure was evaluated by adding known amounts of manganese standard to urine samples and following the whole procedure. Recoveries within the range 97.2-102.8% were obtained. To further prove the accuracy, a Seronorm Trace Elements in Urine, Batch 403125 sample with a reported concentration of 13 ?g Mn L-1 was also analyzed. The experimental value obtained was of 12.7 ± 0.1 ?g l-1, which does not differ significantly from the reported amount (p < 0.05). A pre-concentration factor of 40, a linear range between 0.015 and 60 ?g L-1 and a limit of detection of 15 ng L-1 permitted the determination of manganese in real urine samples from non-exposed subjects in the range 0.5-2.8 ?g l-1. © 2005 Elsevier B.V. All rights reserved.

"Sequential Injection Chromatographic Determination Of Ambroxol Hydrochloride And Doxycycline In Pharmaceutical Preparations"
Talanta 2005 Volume 68, Issue 2 Pages 214-218
Dalibor &Scaron;at&iacute;nsk&yacute;, Lucia M. L. Dos Santos, Hana Sklen&aacute;&#345;ov&aacute;, Petr Solich, M.Concei&ccedil;&atilde;o B.S.M. Montenegro and Alberto N. Ara&uacute;jo

Abstract: A new separation method based on a novel reversed-phase sequential injection chromatography (SIC) technique was used for simultaneous determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations in this contribution. The coupling of short monolith with SIA system results in an implementation of separation step to until no-separation low-pressure method. A Chromolith® Flash RP-18e, 25-4.6 mm column (Merck, Germany) and a FIAlab® 3000 system (USA) with a six-port selection valve and 5 mL syringe were used for sequential injection chromatographic separations in our study. The mobile phase used was acetonitrile-water (20:90, v/v), pH 2.5 adjusted with 98% phosphoric acid, flow rate 0.48 mL min-1, UV detection was at 213 nm. The validation parameters have shown good results: linearity of determination for both compounds including internal standard (ethylparaben) >0.999; repeatability of determination (RSD) in the range 0.5-5.4% at three different concentration levels, detection limits in the range 0.5-2.0 ?g mL -1, and recovery from the pharmaceutical preparation in the range 99.3-99.9%. The chromatographic resolution between peak compounds was >5.0 and analysis time was <9 min under the optimal conditions. The method was found to be applicable for routine analysis of the active compounds ambroxol hydrochloride and doxycycline in various pharmaceutical preparations. © 2005 Elsevier B.V. All rights reserved.

"A New Approach For The Sequential Injection Spectrophotometric Determination Of The Total Antioxidant Activity"
Talanta 2005 Volume 68, Issue 2 Pages 207-213
M.J. Reis Lima1, Ildik&oacute; V. T&oacute;th and Ant&oacute;nio O.S.S. Rangel

Abstract: A sequential injection system based on the ABTS (2,2?-azino-bis-(3-ethylbenzothiazoline-6-sulphonic-acid) methodology was developed. The proposed method, incorporating a mixing chamber in the side port of the selection valve, was evaluated to measure the total antioxidant activity of several beverages and foods. The ABTS+ is generated by oxidation of ABTS with potassium persulfate and is reduced in presence of hydrogen-donating antioxidants converting into a colorless product. The applicability of the developed method was tested by measurement of the antioxidant activity of pure compounds as well as by analyzing complex food and beverage samples. The antioxidant activity was presented as l(+) ascorbic acid equivalence. The values obtained by this methodology were not significantly different from the results obtained by the original spectrophotometric ABTS assay. For most of the studied antioxidants, antioxidant activity varied with pH and dilution. The proposed SIA system is suitable for screening direct or diluted total antioxidant activity of pure compounds or food samples. © 2005 Elsevier B.V. All rights reserved.

"Sequential Injection Analysis System For On-line Monitoring Of L-cysteine Concentration In Biological Processes"
Talanta 2005 Volume 68, Issue 2 Pages 187-192
Seung-Hyun Lee, Ok-Jae Sohn, Yong-Sik Yim, Kyung-Ah Han, Gi Woo Hyung, Sung Hyo Chough and Jong Il Rhee

Abstract: A sequential injection analysis (SIA) system was developed to monitor the concentration of l-cysteine in biological processes on-line. It is based on the redox reaction of l-cysteine with iron(III) in the presence of 1,10-phenanthroline (phen) and the detection of the red-iron(II)-phen complex with a spectrophotometry. The system was fully automated using software written in the LabVIEW? development environment. A number of system variables such as the flow rate of the carrier buffer solution, the volume ratio of the sample to the reagents, and the reaction coil length, etc., were evaluated to increase the sensitivity and performance of the SIA system. Under partially optimized operating conditions the performance of the SIA system was linear up to a concentration of l-cysteine of 1 mM (R2 = 0.998) with a detection limit of 0.005 mM and a sample frequency of 15 hr-1. The SIA system was employed to monitor the concentration of l-cysteine on-line in a continuously stirred reactor and a fermentation process of Saccharomyces cerevisiae. The on-line monitored data were in good agreement with the off-line data measured by a HPLC with a fluorescence detector (n = 15, R2 = 09899). © 2005 Elsevier B.V. All rights reserved.

"Application Of Sequential Injection-square Wave Voltammetry (SI-SWV) To Study The Adsorption Of Atrazine Onto A Tropical Soil Sample"
Talanta 2005 Volume 68, Issue 2 Pages 165-170
Luciana B.O. dos Santos, Gilberto Abate and Jorge C. Masini

Abstract: Square wave voltammetry automated by sequential injection analysis was applied to determine the Freundlich adsorption coefficients for the adsorption of atrazine onto a clay rich soil. The detection limit in soil extracts was between 0.18 and 0.48 ?mol L-1, depending on the medium used to prepare the extracts (0.010 mol L-1 KCl, CaCl2 or HNO 3 and 0.0050 mol L-1 H2SO4), all of them conditioned in 40 mmol L-1 Britton-Robinson buffer at pH 2.0 in presence of 0.25 mol L-1 NaNO3. Also in soil extracts the linear dynamic range was between 1.16 and 18.5 ?mol L-1 (0.25-4.0 ?g mL-1), with a sampling frequency of 190 h-1. The Kf Freundlich adsorption coefficient was 3.8 ± 0.2 ?mol1-1/n Ln kg-1 in medium of 0.010 mol L-1 KCl or CaCl2, but increased to 7.7 ± 0.1 and 9.0 ± 0.3 ?mol1-1/n Ln kg-1 in 0.010 mol L-1 HNO3 and 0.0050 mol L-1 H 2SO4, respectively. The increase of Kf was related to the decrease of pH from 6.4-6.7 in KCl and CaCl2 to 3.7-4.0 in presence of HNO3 or H2SO4, which favors protonation of atrazine, facilitating electrostatic attractions with negative charges of the clay components of the soil. The 1/n parameters were between 0.76 and 0.86, indicating that the isotherms are not linear, suggesting the occurrence of chemisorption at specific adsorption sites. No statistically significant differences were observed in comparison to the adsorption coefficients obtained by HPLC. The advantage of the proposed SI-SWV method is the great saving of reagent because it does not use organic solvent as in the case of HPLC (50% (v/v) acetonitrile in the mobile phase). Additionally the start up of SI-SWV is immediate (no column conditioning necessary) and the analysis time is only 19 s. © 2005 Elsevier B.V. All rights reserved.

"Speciation And Preconcentration Of Inorganic Antimony In Waters By Duolite GT-73 Microcolumn And Determination By Segmented Flow Injection-hydride Generation Atomic Absorption Spectrometry (SFI-HGAAS)"
Talanta 2005 Volume 68, Issue 1 Pages 86-92
Asl&#305; Erdem and Ahmet E. Ero&#287;lu

Abstract: A selective matrix removal/separation/enrichment method, utilizing a microcolumn of a chelating resin with SH functional groups (Duolite GT-73), was proposed for the determination of Sb(III) in waters by segmented flow injection-hydride generation atomic absorption spectrometry (SFI-HGAAS). The resin was selective to Sb(III) at almost all pH and acidity values employed, whereas Sb(V) was not retained at all and could be determined after a pre-reduction step with l-cysteine. Spike recoveries were tested at various concentration levels in different water types and were found to vary between 85 and 118%. Accuracy of the proposed methodology was checked by analyzing a standard reference material and a good correlation was found between the determined (13.3 ± 1.1 ?g l-1) and the certified value (13.79 ± 0.42 ?g l-1). The method was applied to several bottled drinking water samples for antimony determination with and without pre-concentration and none of the samples were found to contain antimony above the permissible level (5 ?g l-1). The characteristic concentration (the concentration of the analyte corresponding to an absorbance of 0.0044) was 0.55 ?g L-1 and the 3 s limit of detection (LOD) based on five times pre-concentration was 0.06 ?g l-1. The applicability of the microcolumn separation/pre-concentration/matrix removal method for flow injection systems was also demonstrated. © 2005 Elsevier B.V. All rights reserved.

"Nanometer Titanium Dioxide Immobilized On Silica Gel As Sorbent For Preconcentration Of Metal Ions Prior To Their Determination By Inductively Coupled Plasma Atomic Emission Spectrometry"
Talanta 2005 Volume 68, Issue 1 Pages 25-30
Yan Liu, Pei LiangCorresponding Author Contact Information, E-mail The Corresponding Author and Li Guo

Abstract: Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer TiO2) was prepared by sol-gel method and characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The adsorptive potential of immobilized nanometer TiO2 for the pre-concentration of trace Cd, Cr, Cu and Mn was assessed in this work. The metal ions studied can be quantitative retained at a pH range of 8-9, and 0.5 mol L-1 HNO 3 was sufficient for complete elution. The adsorption capacity of immobilized nanometer TiO2 for Cd, Cr, Cu and Mn was found to be 2.93, 2.11, 6.69 and 2.47 mg g-1, respectively. A new method using a microcolumn packed with immobilized nanometer TiO2 as sorbent has been developed for the pre-concentration of trace amounts of Cd, Cr, Cu and Mn prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The method has been successfully applied for the determination of trace elements in some environmental samples with satisfactory results. © 2005 Elsevier B.V. All rights reserved.

"On-line Collection/concentration Of Trace Amounts Of Formaldehyde In Air With Chromatomembrane Cell And Its Sensitive Determination By Flow Injection Technique Coupled With Spectrophotometric And Fluorometric Detection"
Talanta 2005 Volume 67, Issue 5 Pages 1014-1022
Piyanete Sritharathikhun, Mitsuko Oshima and Shoji Motomizu

Abstract: A simple, rapid and highly sensitive method for the determination of trace amounts of formaldehyde in air by using flow injection analysis (FIA) system coupled with a three-hole chromatomembrane cell (CMC) was investigated by using a spectrophotometer and a fluorometer. The CMC was applied to on-line collection/concentration of trace amounts of formaldehyde in air into water as an absorbing solution; formaldehyde in the air was found to be quantitatively transferred into the absorbing solution in CMC. The solution, containing absorbed formaldehyde, was introduced into the carrier stream of the FIA system. The amount of formaldehyde in an absorbing solution was measured spectrophotometrically and fluorometrically after the reaction with a mixed reagent of acetylacetone and ammonium acetate at pH 5.6-5.8. The amount of formaldehyde in the absorbing solution, measured by the proposed system, could be converted to the concentration of formaldehyde in the air sample. A calibration graph prepared by a series of standard formaldehyde aqueous solutions was adopted. The formaldehyde in indoor air, determined as exampled by the proposed spectrophotometric FIA, was found to be 5.14 ± 0.08 ppbv for 20 mL of the air sample at the air flow rate of 6 mL min-1, and the relative standard deviation (RSD) was 1.56%. The limit of detections (LODs) of HCHO in an absorbing solution was 2 x 10^-8 M (0.6 ppb) and 8 x 10^-9 M (0.2 ppb), respectively, by the spectrophotometric and the fluorometric FIA, and the LODs of HCHO in air sample of 40 mL were 0.05 and 0.03 ppbv, respectively. The interferences from foreign species were examined; tolerable concentrations of other aldehydes were more than 50-fold of formaldehyde (1 x 10^-6 M). © 2005 Elsevier B.V. All rights reserved.

"Preliminary Results On The Determination Of Ultratrace Amounts Of Cadmium In Tea Samples Using A Flow Injection On-line Solid Phase Extraction Separation And Preconcentration Technique To Couple With A Sequential Injection Hydride Generation Atomic Fluore"
Talanta 2005 Volume 67, Issue 5 Pages 968-974
Taicheng Duan, Xuejie Song, Dan Jin, Hongfei Li, Jingwei Xu and Hangting Chen

Abstract: In this work, a method was developed for determination of ultra-trace levels of Cd in tea samples by atomic fluorescence spectrometry (AFS). A flow injection solid phase extraction (FI-SPE) separation and pre-concentration technique, to on-line couple with a sequential injection hydride generation (SI-HG) technique is employed in this study. Cd was pre-concentrated on the SPE column, which was made from a neutral extractant named Cyanex 923, while other matrix ions or interfering ions were completely or mostly separated off. Conditions for the SPE separation and pre-concentration, as well as conditions for the HG technique, were studied. Due to the separation of interfering elements, Cd hydride generation efficiency could be greatly enhanced with the sole presence of Co2+ with a concentration of 200 ?g L -1, which is much lower than those in other works previously reported. Interferences on both the Cd separation and pre-concentration, and Cd hydride generation (HG) were investigated; it showed that both the separation and pre-concentration system, and the HG system had a strong anti-interference ability. The SPE column could be repeatedly used at least 400 times, a RSD of 0.97% was obtained for 6 measurements of Cd with 0.2 µg L-1 and a correlation coefficiency of 1.0000 was obtained for the measurement of a series of solutions with Cd concentrations from 0.1 to 2 µg L-1. The method has a low detection limit of 10.8 ng L-1 for a 25 mL solution and was successfully validated by using two tea standard reference materials (GBW08513 and GBW07605).

"Speciation Of Vanadium In Water With Quinine Modified Resin Micro-column Separation/preconcentration And Their Determination By Fluorination Assisted Electrothermal Vaporization (FETV)-inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)"
Talanta 2005 Volume 67, Issue 4 Pages 854-861
Yiwei Wu, Zucheng Jiang and Bin Hu

Abstract: A simple and selective method of flow injection (FI) using a micro-column packed with quinine modified resin as solid phase extractant has been developed for pre-concentration and separation of trace amount of vanadium(V) and vanadium(IV) in water samples, followed by determination with fluorination assisted electrothermal vaporization (FETV)-inductively coupled plasma optical emission spectrometry (ICP-OES). At pH 3 ? 3.8, the modified resin is selective towards V(V) and almost not towards V(IV), while, V(IV) could be quantitatively adsorbed by the modified resin at pH 5 ? 7. The two vanadium species adsorbed by modified resin could be readily desorbed quantitatively with 0.3 mL of 0.5 mol L-1 HCl. Both vanadium species in elution were then determined by ETV-ICP-OES with the use of polytetrafluoroethylene (PTFE) as chemical modifier. Effects of acidity, sample flow rate, concentration of elution solution and interfering ions on the recovery of the analytes have been systematically investigated. Under the optimal conditions, the adsorption capacities of the quinine modified resin for V(V) and V(IV) are 7.6 and 8.0 mg g-1, respectively. The detection limit (3?) of V is 0.072 ng mL-1 for FETV-ICP-OES and 0.56 pg mL-1 for FETV-ICP-MS with enrichment factor of 62.5, and the relative standard deviation (RSD) is 4.9% (n = 9, C = 0.2 ?g mL-1) and 3.8% (n = 9, C = 1.0 ng mL -1), respectively. The proposed method has been applied to the determination of trace V(V) and V(IV) in different water samples, and the recoveries of V(V) and V(IV) are 100 ± 10%. In order to further verify the accuracy of the developed method, FETV-ICP-MS was employed to analyze the vanadium species in water samples after separation/pre-concentration, and analytical results are in good agreement with that obtained by the proposed method. The developed method was also applied to the analysis of the total V in GBW07401 soil certified reference material and in GBW07605 tea leaves certified reference material, and the determined values coincided with the certified values very well. © 2005 Elsevier B.V. All rights reserved.

"Flow Injection Fluorimetric Determination Of Chromium(VI) In Electroplating Baths By Luminescence Quenching Of Tris(2,2-bipyridyl) Ruthenium(II)"
Talanta 2005 Volume 67, Issue 4 Pages 696-702
Saad S.M. HassanCorresponding Author Contact Information, E-mail The Corresponding Author, Ayman A. Abdel-Shafi and Ayman H.K. Mohammed

Abstract: A sensitive and selective luminescence quenching method is developed and used for manual and flow injection analysis (FIA) of chromium(VI) by reaction with [Ru(bpy)3]2+. The emission peak of ruthenium(II) at 595 nm is linearly decreased as a function of Cr(VI) concentration. This permits determination of chromium(VI) ion over the concentration range 0.1-20 ?g mL-1 with a detection limit of 33 ng mL-1. The quenching process is due to an electron transfer from the luminescent [Ru(bpy) 3]2+ complex ion to Cr(VI) resulting in the formation of the non-luminescent [Ru(bpy)3]3+ complex ion. Selectivity for Cr(VI) over many anions and transition, alkali and alkaline earth metal cations is demonstrated. High concentration levels of sulphate, chloride, borate, acetate, phosphate, nitrate, cyanide, Pb2+, Zn2+, Hg2+, Cu2+, Cd2+, Ni2+ and Mn 2+ ions are tolerated. The effects of solution pH and [Ru(bpy) 3]2+ reagent concentration are examined and the reaction conditions are optimized. Validation of the method according to the quality assurance standards show suitability of the proposed method for use in the quality control assessment of Cr(VI) in complex matrices without prior treatment. The method is successfully applied to determine chromium(VI) in electroplating baths using flow injection analysis. Results with a mean standard deviation of ±0.6% are obtained which compare fairly well with data obtained using atomic absorption spectrometry. © 2005 Elsevier B.V. All rights reserved.

"A Portable And Low Cost Equipment For Flow Injection Chemiluminescence Measurements"
Talanta 2005 Volume 67, Issue 4 Pages 673-677
F&aacute;bio R.P. Rocha, Eva R&oacute;denas-Torralba, Boaventura F. Reis, &Aacute;ngel Morales-Rubio and Miguel de la Guardia

Abstract: A compact, reliable and low cost flow injection chemiluminescence system is described. The flow system consists of a set of solenoid micro-pumps that can dispense reproductive micro-volumes of solutions. The luminometer was based on a coiled cell constructed from polyethylene tubing that was sandwiched between two large area photodiodes. The whole equipment costs about US$ 750 and weights ~3 kg. Equipment performance was evaluated by measuring low concentrations of hydrogen peroxide by oxidation of luminol and for the determination of ammonium, based on its inhibition of the luminescence provided by the reaction of luminol and sodium hypochlorite. Linear responses were achieved within 1.0-80 ?mol L-1 H2O2 and 0.6-60 ?mol L-1 NH4+ with detection limits estimated as 400 nmol L-1 H2O2 and 60 nmol L-1 NH4+ at the 99.7% confidence level. Coefficients of variation were 1.0 and 1.8%, estimated for 20 ?mol L -1 H2O2 and 15 ?mol L-1 NH 4+ (n = 20), respectively. Reagent consumption of 55 ?g luminol, effluent volume of 950 µL per determination and sampling rate of 120 samples per hour were also achieved. © 2005 Elsevier B.V. All rights reserved.

"FIA-potentiometry In The Sub-Nernstian Response Region For Rapid And Direct Chloride Assays In Milk And In Coconut Water"
Talanta 2005 Volume 67, Issue 3 Pages 651-657
Iranaldo Santos da Silva, Eduardo Mathias Richter, Claudimir L&uacute;cio do Lago, Ivano G.R. Gutz, Auro Atsushi Tanaka and L&uacute;cio Angnes

Abstract: A simple and reliable FIA-potentiometric system for rapid assays of chloride in certain food samples is described and evaluated. The system is constituted by an aquarium air pump to propel the carrier solution, a manually operated injector, a homemade dialysis flow cell, a solid-state chloride detector (Ag/AgCl), a reference electrode and a multimeter connected to a microcomputer for data acquisition. The dialysis unit enables direct analysis of liquid food samples without any other previous treatment. The principal novelties are the precision (RSD of 1.2% for whole milk) and rapidity (90 determinations/h) of FIA measurements near and below the lower end of the linear (Nernstian) response region of the chloride ion-selective electrode (ISE), with an estimated detection limit (3 s) of 0.4 mg L-1 Cl- in the sample injected in donor stream. Data of peak potential versus sample chloride concentration (donor stream) was accurately fitted with a quadratic polynomial over the range between 4 and 1000 mg L-1 (r2 = 0.9999) and used as a calibration curve. The method was applied to the determination of chloride in milk and in coconut water samples. The validation of the results was done by comparison with a NIST reference material (milk) or by capillary electrophoresis (coconut water). For all analysis, no significant difference at a 95% confidence level was observed. © 2005 Elsevier B.V. All rights reserved.

"Optimization Of A Portable Microanalytical System To Reduce Electrode Fouling From Proteins Associated With Biomonitoring Of Lead (Pb) In Saliva"
Talanta 2005 Volume 67, Issue 3 Pages 617-624
Wassana Yantasee, Charles Timchalk, Karl K. Weitz, Dean A. Moore and Yuehe Lin

Abstract: There is a need to develop reliable portable analytical systems for on-site and real-time biomonitoring of lead (Pb) from both occupational and environmental exposures. Saliva is an appealing matrix since it is easily obtainable, and therefore a potential substitute for blood due to existing reasonably good correlation between Pb levels in blood and saliva. The microanalytical system is based on flow-injection/stripping voltammetry with a wall-jet (flow-onto) microelectrochemical cell. Samples that contain as little as 1% saliva can cause electrode fouling, resulting in significantly reduced responsiveness and irreproducible quantitations. In addition, incomplete Pb release from salivary protein can also yield a lower Pb response than expected. This paper evaluates the extent of in vitro Pb-protein binding and the optimal pretreatment for releasing Pb from the saliva samples. Even in 50% by volume of rat saliva, the electrode fouling was not observed, due to the appropriate sample pretreatment and the constant flow of the sample and acidic carrier that prevented passivation by the protein. The system offered a linear response over a low Pb range of 1-10 ppb, low detection limit of 1 ppb, excellent reproducibility, and reliability. It also yielded the same Pb concentrations in unknown samples as did the ICP-MS. These encouraging results suggest that the microanalytical system represents an important analytical advancement for real-time non-invasive biomonitoring of Pb. © 2005 Elsevier B.V. All rights reserved.

"Rapid Enzymatic Chemiluminescent Assay Of Glucose By Means Of A Hybrid Flow-injection/sequential-injection Method"
Talanta 2005 Volume 67, Issue 3 Pages 603-609
Polyxeni Panoutsou and Anastasios Economou

Abstract: This work reports a hybrid flow-injection analysis (FIA)/sequential- injection analysis (SIA) method for the rapid enzymatic assay of glucose with soluble glucose oxidase (GOD). The method relies on the sequential injection of segments of the sample and of a solution of enzyme by means of a multi-port selection valve in a flowing water stream. As the two zones are swept downstream, they overlap and merge so that the glucose in the sample is enzymatically oxidized. The generated hydrogen peroxide is merged with an alkaline luminol solution and the chemiluminescence (CL) intensity is monitored and related to the glucose concentration in the sample. The linear range of the method for glucose determination is 0.01-1 mmol L-1, the relative standard deviation is 3.9% at the 0.08 mmol L-1 level (n = 8), the limit of detection at the 2? level is 4 ?mol L-1 glucose and the injection rate is 80 h-1. The method was applied to the analysis of energy drinks and honey with relative errors in glucose determination in the range 100 ± 4.3%. The advantages of the proposed method are the wide linear range, the simple instrumentation used, the low consumption of sample and reagents, the elimination of catalysts and immobilized enzymes and the high sample throughput. © 2005 Elsevier B.V. All rights reserved.

"Determination Of Selected Neurotransmitter Metabolites Using Monolithic Column Chromatography Coupled With Chemiluminescence Detection"
Talanta 2005 Volume 67, Issue 3 Pages 585-589
Jacqui L. Adcock, Neil W. Barnett, Jason W. Costin, Paul S. FrancisCorresponding Author Contact Information, E-mail The Corresponding Author and Simon W. Lewis

Abstract: The oxidation of selected clinically important neurotransmitter metabolites with acidic potassium permanganate in the presence of polyphosphates evokes chemiluminescence of sufficient intensity to enable the sensitive determination of these species. Limits of detection for 5-hydroxyindole-3-acetic acid (5-HIAA), vanilmandelic acid (VMA; ?,4-dihydroxy-3-methoxybenzeneacetic acid), 4-hydroxy-3-methoxyphenylglycol (MHPG), homovanillic acid (HVA, 4-hydroxy-3-methoxyphenylacetic acid) and 3,4-dihydroxyphenylacetic acid (DOPAC) were between 5 x 10^-9 and 4 x 10^-8 M, using flow-injection analysis methodology. In addition, we demonstrate the rapid determination of homovanillic acid and 5-hydroxyindole-3-acetic acid in human urine - without the need for extraction procedures - using monolithic column chromatography with chemiluminescence detection. © 2005 Elsevier B.V. All rights reserved.

"Sensitized Extraction Spectrophotometric Determination Of Hg(II) With Dithizone After Its Flotation As Ion-associate Using Iodide And Ferroin"
Talanta 2005 Volume 67, Issue 3 Pages 555-559
Mohammad Saeid HosseiniCorresponding Author Contact Information, E-mail The Corresponding Author and Hamid Hashemi-Moghaddam

Abstract: This paper describes a simple and highly selective method for the separation, pre-concentration and spectrophotometric determination of extremely low concentration of mercury. The method is based on the flotation of an ion-associate of HgI42- and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and treated with ammonia and dithizone solutions to extract only the mercury chelate with CH2Cl2. The measurement is feasible when the volume of the water sample containing Hg(II) was varied over 50-800 mL. Beer's law was obeyed over the concentration range of 8 x 10^-9 to 1.6 x 10^-7 mol L-1 with an apparent molar absorptivity of 6.53 x 106 l mol-1 cm-1 for a 500 mL aliquot of the water sample. The detection limit (n = 7) was 5.0 x 10 -10 mol L-1 and the RSD (n = 5) for 8.0 x 10 -7 mol L-1 of Hg(II) was 3.7%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic sea water and human hair samples was carried out by the present method and cold vapor atomic absorption spectrometry (CV-AAS). The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples. © 2005 Elsevier B.V. All rights reserved.

"Determination Of Psilocin And Psilocybin Using Flow Injection Analysis With Acidic Potassium Permanganate And Tris(2,2-bipyridyl)ruthenium(II) Chemiluminescence Detection Respectively"
Talanta 2005 Volume 67, Issue 2 Pages 354-359
Nicole Anastos, Neil W. Barnett, Simon W. Lewis, Nicholas Gathergood, Peter J. Scammells and D. Noel Sims

Abstract: A simple, rapid and sensitive method for the determination of psilocin and psilocybin is described. This is the first report on the determination of psilocin and psilocybin using flow injection analysis with acidic potassium permanganate and tris(2,2?-bipyridyl)ruthenium(II) chemiluminescence. The limits of detection (signal-to-noise ratio = 3) are 9 x 10^-10 M and 3 x 10^-10 M for psilocin and psilocybin, respectively. A concise synthetic route for psilocin in three steps from readily available starting materials is also described. The structures were elucidated on the basis of spectroscopic data. © 2005 Elsevier B.V. All rights reserved.

"Flow-injection Spectrophotometric Determination Of Methyldopa In Pharmaceutical Formulations"
Talanta 2005 Volume 67, Issue 1 Pages 240-244
P.R.S. Ribeiro, J.A. Gomes Neto, L. Pezza and H.R. Pezza

Abstract: A flow-injection spectrophotometric procedure is proposed for methyldopa determination in pharmaceutical preparations. The determination is based on formation of a yellow product (measured at 410 nm) after complexation of methyldopa with molybdate. Under optimal conditions, Beer's law is obeyed in a concentration range of 50-200 mg L-1 methyldopa. Typical correlation between absorbance and analyte concentration was 0.9999. Usual excipients used as additives in pharmaceuticals do not interfere with the proposed method. The analytical frequency was 210 h-1 and the relative standard deviation (RSD) was ?2% for sample solution containing 150 mg L-1 methyldopa (n = 11). The analytical results obtained in commercial formulations by applying the proposed FIA method were in good agreement with labeled values and those obtained by the Brazilian Pharmacopoeia procedure at 95% confidence level. © 2005 Elsevier B.V. All rights reserved.

"A Spectrophotometric Procedure For DNA Assay With A Micro-sequential Injection Lab-on-valve Meso-fluidic System"
Talanta 2005 Volume 67, Issue 1 Pages 227-232
Xuwei Chen, Jianhua WangCorresponding Author Contact Information, E-mail The Corresponding Author and Zhaolun Fang

Abstract: A micro-sequential injection spectrophotometric procedure for DNA assay was developed based on the employment of a lab-on-valve (LOV) meso-fluidic analytical system. A small amount of crystal violet solution (10 µL) was de-colored inside the flow cell of the LOV at the presence of 5 µL λ-DNA/HindIII within a certain pH range, and the absorbance decrease of crystal violet solution at 591 nm was measured via optical fibers and was employed as the basis of quantification. A univariant approach was adopted for the optimization of experimental parameters, including buffer pH, concentration and volume of crystal violet solution, reaction time and sample/reagent loading flow rates. A linear calibration graph was obtained within 0.2-6.0 µg mL-1, along with a detection limit of 0.07 µg mL-1. The procedure was applied for the determination of λ-DNA/HindIII in synthetic samples in comparison with a documented procedure.

"Synthesis And Application Of A Functionalized Resin For Flow Injection/F AAS Copper Determination In Waters"
Talanta 2005 Volume 67, Issue 1 Pages 121-128
Ricardo J. Cassella, Otto I.B. Magalh&atilde;es, Marcos Tadeu Couto, Edson Luiz S. Lima, Marcia Ang&eacute;lica F.S. Neves and Fernanda Margarida B. Coutinho

Abstract: This paper reports the development of a new strategy for low-level determination of copper in water samples by using a flow-injection system coupled to solid-phase extraction (SPE) using flame atomic absorption spectrometry (F AAS) as detector. In order to pre-concentrate copper from samples, a minicolumn packed with a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis-(4-vinyl-phenyl)-methyl]-pyrrolidine-1-carboxylic acid ethyl ester was used and the synthesis procedure is described. System operation is based on the on-line retention of Cu(II) ions at pH 9.0 ± 0.2 in a such minicolumn with posterior analyte elution with 2 mol L-1 HCl directly to the F AAS nebulizer. The influence of several chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and pre-concentration time) variables that could affect the performance of this system were investigated as well as the possible interferents. At optimized conditions, for 2 min of pre-concentration time (13.2 mL of sample volume), the system achieved a detection limit of 1.1 ?g l-1, a RSD 1% at 20 ?g g l -1 and an analytical throughput of 25 h-1, whereas for 4 min of pre-concentration time (26.4 mL of sample volume), a detection limit of 0.93 ?g l-1, a RSD 5.3% at 5 ?g L-1 and a sampling frequency of 13 h-1 were reported. © 2005 Elsevier B.V. All rights reserved.

"Photometric Detection In Flow Analysis Systems Using Integrated PEDDs"
Talanta 2005 Volume 66, Issue 5 Pages 1340-1344
Martina O' Toole, King Tong Lau and Dermot Diamond

Abstract: A novel inexpensive optical-sensing technique has been developed for colorimetric flow analysis. This sensing system employs two LEDs whereby one is used as the light source and the other as a light detector. The LED used as light detector is reverse biased with a 5-V supply so that the photocurrent generated by the incident light discharges the capacitance. Direct digital output is provided by a simple timer circuit that measures the time taken for this discharge process from 5 V (logic 1) to 1.7 V (logic 0). This sensing concept has been applied in flow analysis by constructing an optical flow cell with a pair of LEDs. Calibration of the integrated optical flow cell using a dye resulted in a linear response that obeys the Beer-Lambert law. The flow rate, dynamic range, sensitivity and limits of detection were investigated. The system was also used for pH determination in the range of pH 2.5-6.8 using bromocresol green (BCG). The pKa of BCG was successfully determined by this technique. © 2005 Elsevier B.V. All rights reserved.

"A Flow-injection Renewable Surface Sensor For The Fluorimetric Determination Of Vanadium(V) With Alizarin Red S"
Talanta 2005 Volume 66, Issue 5 Pages 1333-1339
M.J. Ruedas Rama, A. Ruiz Medina and A. Molina D&iacute;az

Abstract: Vanadium(V) is determined by a simple bead injection spectroscopy-flow- injection analysis (BIS-FIA) system with spectrofluorimetric detection using a commercially available flow cell (Hellma 176-QS). The 500 µL of a homogeneous bead suspension of an anionic resin (Sephadex QAE A-25) previously loaded with the fluorogenic reagent 1,2-dihydroxyanthraquinone-3-sulfonic acid (Alizarin Red S) was injected to fill the flow cell. Next, V(V) is injected into the carrier and reacts with the immobilized reagent on the active solid support placed in the flow cell to form a fluorescent chelate in the absence of surfactant agents. The complex is so strongly retained on the beads that the regeneration of the solid support becomes extraordinarily difficult, so needing the renovation of the sensing surface which is achieved by means of bead injection. At the end of the analysis, beads are automatically discarded from the flow cell and transported out of the system by reversing the flow. The measurement of fluorescence is continuously performed at an excitation wavelength of 521 nm and an emission wavelength of 617 nm. Using a low sample volume of 800 µL, the analytical signal showed a very good linearity in the range 2-60 ng mL -1, with a detection limit of 0.45 ng mL-1 and a RSD (%) of 4.22 for 50 ng mL-1 of V(V) concentration (n = 10). The sensor showed both a good selectivity, which could also be increased by the addition of EDTA and F- as masking agents, and applicability to the determination of V(V) in waters, physiological samples (serum and urine) and mussel tissues. © 2005 Elsevier B.V. All rights reserved.

"Determination Of Trace Metal Ions Via On-line Separation And Preconcentration By Means Of Chelating Sepharose Beads In A Sequential Injection Lab-on-valve (SI-LOV) System Coupled To Electrothermal Atomic Absorption Spectrometric Detection"
Talanta 2005 Volume 66, Issue 5 Pages 1326-1332
Xiangbao Long, Elo Harald Hansen and Manuel Mir&oacute;

Abstract: The analytical performance of an on-line sequential injection lab-on-valve (SI-LOV) system using chelating Sepharose beads as sorbent material for the determination of ultra-trace levels of Cd(II), Pb(II) and Ni(II) by electrothermal atomic absorption spectrometry (ETAAS) is described and discussed. The samples are adjusted to pH 5.0 on-line in the system for optimum operation. The target ions are adsorbed by chelation on the surface of the beads, contained in a 20 µL microcolumn within the LOV, and following elution by 50 µL 2 M nitric acid, the eluate is, as sandwiched by air segments, introduced into the ETAAS. Based on the consumption of 1.8 mL sample solution, retention efficiencies of 95, 75 and 90%, enrichment factors of 34, 27 and 32, and determination limits of 0.001, 0.07 and 0.02 ?g L-1 were obtained for Cd(II), Pb(II) and Ni(II), respectively. The beads can be used repeatedly for at least 20 times without decrease of performance, yet can be replaced at will if the circumstances should so dictate. The optimized procedural parameters showed that 12 samples per hour could be prepared and successfully analyzed. The results obtained for three standard reference materials agreed very well with the certified values. © 2005 Elsevier B.V. All rights reserved.

"A Peroxidase-tetrathiafulvalene Biosensor Based On Self-assembled Monolayer Modified Au Electrodes For The Flow-injection Determination Of Hydrogen Peroxide"
Talanta 2005 Volume 66, Issue 5 Pages 1310-1319
Susana Campuzano, Mar&iacute;a Pedrero and Jos&eacute; M. Pingarr&oacute;n

Abstract: The construction and performance under flow-injection conditions of an integrated amperometric biosensor for hydrogen peroxide is reported. The design of the bioelectrode is based on a mercaptopropionic acid (MPA) self-assembled monolayer (SAM) modified gold disk electrode on which horseradish peroxidase (HRP, 24.3 U) was immobilized by cross-linking with glutaraldehyde together with the mediator tetrathiafulvalene (TTF, 1 ?mol), which was entrapped in the three-dimensional aggregate formed. The amperometric biosensor allows the obtention of reproducible flow injection amperometric responses at an applied potential of 0.00 V in 0.05 mol L-1 phosphate buffer, pH 7.0 (flow rate: 1.40 mL min-1, injection volume: 150 µL), with a range of linearity for hydrogen peroxide within the 2.0 x 10^-7-1.0 x 10^-4 mol L-1 concentration range (slope: (2.33 ± 0.02) x 10^-2 A mol-1 L, r = 0.999). A detection limit of 6.9 x 10^-8 mol L-1 was obtained together with a RSD (n = 50) of 2.7% for a hydrogen peroxide concentration level of 5.0 x 10^-5 mol L-1. The immobilization method showed a good reproducibility with a RSD of 5.3% for five different electrodes. Moreover, the useful lifetime of one single biosensor was estimated in 13 days. The SAM-based biosensor was applied for the determination of hydrogen peroxide in rainwater and in a hair dye. The results obtained were validated by comparison with those obtained with a spectrophotometric reference method. In addition, the recovery of hydrogen peroxide in sterilised milk was tested. © 2005 Elsevier B.V. All rights reserved.

"Application Of A Potentiometric Electronic Tongue As A Classification Tool In Food Analysis"
Talanta 2005 Volume 66, Issue 5 Pages 1303-1309
Jordi Gallardo, Salvador Alegret and Manuel del Valle

Abstract: This paper reports on the application of a potentiometric sensor array to the food analysis field, in order to distinguish simple tastes and to classify food samples. This array is formed by a set of non-specific all-solid-state potentiometric sensors and has been used in combination with principal component analysis (PCA) for the classification of food samples in batch and in flow injection mode. First attempt was to classify synthetic samples prepared with controlled variability. Once this ability is proven, satisfactory classification results are presented for commercial waters, orange-based drinks and tea samples. An interesting correlation is achieved between the natural juice content and its first calculated component, which allows for a very simple tool for screening purposes. © 2005 Elsevier B.V. All rights reserved.

"Automated Determination Of Glucose In Soluble Coffee Using Prussian Blue-glucose Oxidase-NafionÆ Modified Electrode"
Talanta 2005 Volume 66, Issue 5 Pages 1281-1286
Ivanildo Luiz de MattosCorresponding Author Contact Information, E-mail The Corresponding Author and Madalena Carneiro da Cunha Areias

Abstract: A highly selective, fast and stable biosensor for determination of glucose in soluble coffee has been developed. The biosensor electrode consist of a thin film of ferric hexacyanoferrate (Prussian Blue or PB) electrodeposited on the glassy carbon electrode (GCE) (to provide a catalytic surface for the detection of hydrogen peroxide) glucose oxidase immobilized on top of the electrode and a Nafion® polymer layer. The stability of the PB film and the biosensor was evaluated by injecting standard-solution (50 ?M H 2O2 and 0.5 mM glucose) during 4 h in a flow-injection system with the electrodes polarized at -50 mV versus Ag/AgCl. The system is able to handle about 60 samples per hour and is very stable and suitable for industrial control. Determination of glucose in the range 2.5 and 15% (w/v) in phosphate buffer with precision (RSD < 1.5%) has been achieved and is in agreement with the conventional procedures. Linear calibration in the range of 0.15 and 2.50 mM with detection limits of ~0.03 mM has been obtained. The morphology of the enzyme glucose oxidase on the modified electrode has been analyzed by scanning electron microscopy (SEM) measurements. © 2005 Elsevier B.V. All rights reserved.

"Fourier Transform Cyclic Voltammetric Technique For Monitoring Ultratrace Amounts Of Salbutamol At Gold Ultra Microelectrode In Flowing Solutions"
Talanta 2005 Volume 66, Issue 5 Pages 1225-1233
Mohammad Reza GanjaliCorresponding Author Contact Information, E-mail The Corresponding Author, Parviz Norouzi, Maryam Ghorbani and Ali Sepehri

Abstract: This work introduce an easy and fast continuous cyclic voltammetric technique for the propose monitoring of ultra trace amounts of salbutamol in a flow-injection system. The potential waveform, which consisted of the potential steps for cleaning, stripping and potential ramp, was continuously applied on an Au disk microelectrode (with a radius of 12.5 ?m). The detection method we propose has some advantages, the greatest of which are: (1) removing oxygen from the analyte solution is no longer necessary, and (2) it is a very fast and appropriate technique for the determination of the drug compound in a wide variety of chromatographic analysis methods. The detection limit for salbutamol was 2.0 x 10^-9 M. The relative standard deviation (RSD) of the proposed technique at 10 ng/mL was 3.5% for 10 runs. The effects of pH of eluent, accumulation potential, sweep rate, and accumulation time on the sensitivity of the method for the determination of the salbutamol were investigated. The proposed method was applied to the determination of salbutamol in pharmaceutical preparation and biological samples. © 2005 Elsevier B.V. All rights reserved.

"Amperometric Detection Of Mono- And Diphenols At Cerrena Unicolor Laccase-modified Graphite Electrode: Correlation Between Sensitivity And Substrate Structure"
Talanta 2005 Volume 66, Issue 5 Pages 1219-1224
Anna Jarosz-Wilko&#322;azka, Tautgirdas Ruzgas and Lo Gorton

Abstract: Graphite electrode modified with laccase from Cerrena unicolor served as a biosensor for detection of 30 phenolic compounds with different structures. Some correlations of the sensor response to the structures of substrates are discussed. This biosensor responded to: (i) nanomolar concentrations of some of the selected phenolic compounds, e.g., 2,6-dimethoxyphenol, coniferyl alcohol, caffeic acid, DOPAC and hydroquinone, (ii) micromolar concentrations, e.g., ferulic acid, syringic acid, dopamine, 3,4-dihydroxybenzoic acid and dl-noradrenaline, and (iii) millimolar concentrations in the case of phenol and 4-hydroxybenzaldehyde. Among the ortho- or para-substituted phenols, the sensitivity of the C. unicolor laccase-modified electrode increased in the following order H, CH3, OH, OCH3 and NH3+ but in the case of para-substituted phenols, the Kmapp values were lower. The sensitivity of the laccase electrode increased with an additional OH group in para-substituted phenols. In the case of the selected compounds, kinetic data from electrochemical flow injection system were compared with those obtained from experiments in solution. © 2005 Elsevier B.V. All rights reserved.

"Sequential Injection System With Higher Dimensional Electrochemical Sensor Signals: Part 2. Potentiometric E-tongue For The Determination Of Alkaline Ions"
Talanta 2005 Volume 66, Issue 5 Pages 1197-1206
M. Cortina, A. Gut&eacute;s, S. Alegret and Manuel del Valle

Abstract: An intelligent, automatic system based on an array of non-specific-response chemical sensors was developed. As a great amount of information is required for its correct modelling, we propose a system generating it itself. The sequential injection analysis (SIA) technique was chosen as it enables the processes of training, calibration, validation and operation to be automated simply. Detection was carried out using an array of potentiometric sensors based on PVC membranes of different selectivity. The diluted standard solutions needed for system learning and response modelling are automatically prepared from more concentrated standards. The electrodes used were characterized with respect to one and two analytes, by means of high-dimensionality calibrations, and the response surface of each was represented; this characterisation enabled an interference study of great practical utility. The combined response was modelled by means of artificial neural networks (ANNs), and thus it was possible to obtain an automated electronic tongue based on SIA. In order to identify the ANN which provided the best model of the electrode responses, some of the network's parameters were optimized and its usefulness in determining NH 4+, K+ and Na+ ions in synthetic samples was then tested. Finally, it was used to determine these ions in commercial fertilisers, the obtained results being compared with reference methods. © 2005 Elsevier B.V. All rights reserved.

"Sequential Injection System With Higher Dimensional Electrochemical Sensor Signals: Part 1. Voltammetric E-tongue For The Determination Of Oxidizable Compounds"
Talanta 2005 Volume 66, Issue 5 Pages 1187-1196
A. Gut&eacute;s, F. C&eacute;spedes, S. Alegret and M. del Valle

Abstract: A sequential injection analysis (SIA) system was developed with the aim of obtaining an automatic and versatile way to prepare standards needed in the study of systems with higher dimensional sensor signals. To illustrate this, different analytical techniques were used in determinations of several analytes. Automated potentiometric calibrations of different potentiometric sensors, with and without interference, were carried out. Useful determinations of selectivity coefficients with two degrees of freedom were obtained. Simultaneous voltammetric determinations have also been done. Firstly, simultaneous determinations of lead and cadmium, using epoxy-graphite composite as the working electrode, have enabled a separate calibration for each metal to be obtained. Next, a voltammetric electronic tongue was designed and applied to the determination of oxidizable species. The use of artificial neural networks has solved the overlapped signal of ascorbic acid, 4-aminophenol and 4-acetamidophenol (paracetamol). A set of 63 data points was prepared automatically and has facilitated the training of an electronic tongue for these three analytes. Accurate predictions of test solutions, in the range of 12-410 ?M for ascorbic acid, 17-530 ?M for 4-aminophenol and 10^-420 ?M for paracetamol, have been achieved with RMSEs lower than 0.10 ?M. © 2005 Elsevier B.V. All rights reserved.

"Fe Analysis By The Ferrozine Method: Adaptation To FIA Towards In Situ Analysis In Hydrothermal Environment"
Talanta 2005 Volume 66, Issue 5 Pages 1131-1138
Pierre-Marie SarradinCorresponding Author Contact Information, E-mail The Corresponding Author, E-mail The Corresponding Author, Nadine Le Bris, Christian Le Gall and Philippe Rodier

Abstract: The target of this study is the adaptation of the ferrozine method to flow injection analysis (FIA) to perform iron analysis in situ using an in situ chemical analyzer. in hydrothermal environments. The adaptation of the method to FIA was followed by its optimization using an experimental design screening method. The goals of the optimization steps were to decrease the detection limit and to increase the measuring range to cope with the constraints of in situ analysis. The method allows the determination of iron in the mixing zone of hydrothermal fluid, enriched in iron, and seawater. A single manifold gives the possibility to analyze either Fe(II) or ?Fe [Fe(II) + Fe(III)] in situ, or ?Fe in the lab on hydrothermal seawater samples. The measuring range of the method was increased to up to 2000 ?M, which is coherent with the study of the chemical environment of communities associated with deep-sea hydrothermal activity. Finally, the method was applied in situ using the chemical analyzer. Alchimist during the ATOS cruise on hydrothermal vent fields on the Mid Atlantic Ridge. © 2005 Elsevier B.V. All rights reserved.

"Flow Injection Kinetic Spectrophotometric Determination Of Trace Amounts Of Se(IV) In Seawater"
Talanta 2005 Volume 66, Issue 4 Pages 1012-1017
Gong Zhengjun, Zhang Xinshen, Chen Guohe and Xiao Xinfeng

Abstract: A simple, accurate, sensitive and selective flow injection catalytic kinetic spectrophotometric method for rapid determination of trace amounts of selenium is proposed in this paper. The proposed method is based on the accelerating effect of Se(IV) on the reaction of ethexlenediamine tetrecetic acid disodium salt (EDTA) and sodium nitrate with ammonium iron(II) sulfate hexahydrate in acidic media. The absorbance intensity was registered in this reaction solution at 440 nm. The calibration graph is linear in the range of 5 x 10^-9-2 x 10^-7 and 2 x 10 -7-2 x 10^-6 g mL-1. The detection limit is 2 x 10^-9 g mL-1. The relative standard deviation was 3.4% for 5 x 10^-8 g mL-1 Se(IV) (n = 11), 2.7% for 5 x 10^-7 g mL-1 Se(IV) (n = 11). This method is very simple, rapid and suitable for automatic and continuous analysis. The presented system has been applied successfully to determination of Se(IV) of seawater samples. © 2005 Elsevier B.V. All rights reserved.

"Response Surface Methodology For The Optimisation Of Flow-injection Analysis With In Situ Solvent Extraction And Fluorimetric Assay Of Tricyclic Antidepressants"
Talanta 2005 Volume 66, Issue 4 Pages 952-960
Mar&iacute;a-Isabel Acedo-Valenzuela, Teresa Galeano-D&iacute;az, Nielene Mora-D&iacute;ez and Antonio Silva-Rodr&iacute;guez

Abstract: A semiautomatic extraction-fluorimetric method for the determination of tricyclic antidepressant drugs (TCAs) based in the formation of ion pairs with 9,10-dimethoxyanthracene-2-sulphonate (DMAS) has been developed. The aqueous solutions of the TCAs (imipramine, desipramine, amitriptyline, nortriptyline, clomipramine or doxepine) are injected into a carrier composed by DMAS in an acid medium and the ion pair formed is extracted into dichloromethane where the fluorescence is measured. An experimental design (Central Composite Design) together with the Response Surface Methodology has been used to find the optimal instrumental FIA and chemical variables. We have considered as the response function the product of the peak height by the sampling frequency. The calibration curves were linear over the working range (0.25-3.00 mg L -1). The limits of detection were lower than 0.30 mg L-1. The method has been satisfactorily applied to the determination of imipramine, amitriptyline, clomipramine and doxepin in pharmaceutical preparations. © 2004 Elsevier B.V. All rights reserved.

"A Chemiluminescence-based Continuous Flow Aqueous Ozone Analyzer Using Photoactivated Chromotropic Acid"
Talanta 2005 Volume 66, Issue 4 Pages 823-830
Toshio Takayanagi and Purnendu K. Dasgupta

Abstract: Ozone has become the oxidant of choice for water disinfection, especially in large water treatment facilities. This paper describes a fast and sensitive method for the determination of ozone content by reaction with photoactivated chromotropic acid (CA, 4,5-dihydroxynaphthalene-2,7-disulfonic acid), which results in intense chemiluminescence (CL). Freshly ozonated water from a recirculating ozonizer/reservoir is injected into a carrier stream of deionized water in the flow-injection mode. This flow mixes with a stream of photoactivated CA solution in a spiral cell placed directly on top of an inexpensive miniature (8 mm diameter active area) photomultiplier tube (PMT). Alkaline CA is photoactivated by passing it through a FEP-Teflon® coil (residence time ? 50 s) wrapped around a 1 W UV lamp emitting at 254 nm; without photoactivation, the signal is ~70-fold lower. The S/N = 3 limit of detection for aqueous ozone is 3 µg L-1 and good response slope is obtained up to an ozone concentration of 1.4 mg l-1, the highest that could be made in this study. The response obeyed a quadratic equation with r2 = 0.9984. No interference from permanganate ion is observed. The proposed system was applied to the monitoring of ozonation status of a playa lake water that exhibited significant ozone demand. © 2004 Elsevier B.V. All rights reserved.

"Flow Injection-hydride Generation-infrared Spectrophotometric Determination Of Pb"
Talanta 2005 Volume 66, Issue 3 Pages 789-793
Oktay Cankur, Deniz Korkmaz and O. Yavuz Ataman

Abstract: A novel analytical technique has been suggested for determination of Pb using formation of PbH4(g) by chemical reduction and its subsequent spectrophotometric measurement in IR region, using the peak at 1821.4 cm -1. The range of measurements is 1.0-30.0 mg L-1 using a sample of 1.0 mL in flow injection mode. The 3? limit of detection is 0.28 mg l-1. The method has been applied to standard reference materials of Waste Water, EU-L-1, lead-base bearing metal 53e and Soil/Sediment #4 as well as soil samples collected from heavy traffic areas in Ankara. © 2004 Elsevier B.V. All rights reserved.

"Mercury Speciation By Liquid Chromatography Coupled With On-line Chemical Vapour Generation And Atomic Fluorescence Spectrometric Detection (LC-CVGAFS)"
Talanta 2005 Volume 66, Issue 3 Pages 762-768
Emilia Bramanti, Cristina Lomonte, Massimo Onor, Roberto Zamboni, Alessandro D'Ulivo and Giorgio Raspi

Abstract: Reverse phase chromatography (RPC) coupled on-line with UV-vis diode array detector (DAD) and cold vapor generation atomic fluorescence spectrometry (CVGAFS) is proposed for the speciation and determination of inorganic and organic mercury (methylmercury, ethylmercury and phenylmercury) in the form of cysteine, penicillamine and glutathione complexes. The mercury-thiol complexes are separated on a C18 Reverse Phase column and oxidized on-line with bromine, generated in situ by KBr/KBrO3 in HCl medium, in order to fast convert organic mercury species to inorganic mercury in less than 2.5 s, at room temperature, in a 30 cm knitted coil. Hg(II) is selectively detected by AFS in a Ar/H2 miniaturized flame after sodium borohydride reduction to Hg(0). Under optimized conditions, on-line bromine treatment gives recoveries of thiol-complexed methylmercury, ethylmercury and phenylmercury with respect to inorganic mercury ranging between 79 and 85%, 80 and 85%, 63 and 76%, respectively, depending on the complexing thiol employed. Optimized elution conditions were provided in the three complexing agents. The detection limits (LODc) for inorganic mercury, methylmercury, ethylmercury and phenylmercury, in the optimized conditions complexed with thiols were about 16, 18, 18 and 20 pg (as mercury), respectively, a relative standard deviation (R.S.D) ranging between 1.5 and 2.0%, and a linear dynamic range between 0.1 and 100 ng injected. LC-DAD-CVGAFS method has been validated by analyzing two certificate reference material, DORM-2 and NIES CRM 13, obtaining 98 ± 6 and 97 ± 5% of methylmercury recovered, respectively.

"Spectrophotometric Determination Of Iron And Boron In Soil Extracts Using A Multi-syringe Flow Injection System"
Talanta 2005 Volume 66, Issue 3 Pages 703-711
D.M.C. Gomes, M.A. Segundo, J.L.F.C. Lima and A.O.S.S. Rangel

Abstract: In the last decade, significant advances in flow analysis have been reported, namely the extensive use of computer-controlled devices to enhance the autonomy and performance of analyzer.s. In the present work, computer-controlled multi-syringe flow injection systems are proposed to perform the spectrophotometric determination of available iron and boron in soil extracts. The methodologies were based on the formation of ferroin complex (determination of iron) and azomethine-H reaction (determination of boron). Both determinations were performed in manifolds with similar configurations by changing the reagents present in the different syringes. In the determination of iron, elimination of Schlieren effect in the detection system was achieved through the binary sampling approach, where a three-way valve was actuated to intercalate small slugs of sample and reagent, promoting better mixing conditions for solutions with different values of refractive index. In the determination of boron, in-line sample blank measurement was attained by omitting the introduction of reagent through software control, without manifold reconfiguration. Linear calibration curves were established between 0.50 and 10.0 mg Fe L-1 and between 0.20 and 4.0 mg B l-1. No systematic difference was found when soil extracts were analyzed by the proposed methodologies and compared to the respective reference procedures. © 2004 Elsevier B.V. All rights reserved.

"Flow-through Optosensing Of 1-naphthaleneacetic Acid In Water And Apples By Heavy Atom Induced-room Temperature Phosphorescence Measurements"
Talanta 2005 Volume 66, Issue 3 Pages 696-702
Mar&iacute;a Teresa Fern&aacute;ndez-Arg&uuml;elles, Beatriz Ca&ntilde;abate, Antonio Segura, Jos&eacute; Manuel Costa, Rosario Pereiro, Alfredo Sanz-Medel and Alberto Fern&aacute;ndez

Abstract: A sensitive and selective phosphorimetric method for the determination of 1-naphthaleneacetic acid (1-NAA) based on a flow-injection system connected to a flow cell packed with a solid support and placed in the sample compartment of a conventional luminescence spectrometer is described. A non-ionic solid polymeric resin Amberlite XAD-7 is used for the packing. After injection of the sample, 1-NAA is on-line retained in the packed resin and measurements of the heavy atom induced (HAI)-room temperature phosphorescence (RTP) emission (?ex/?em = 292/490 nm) from this native luminescent compound are taken. The optimum experimental conditions were investigated by injecting 2 mL samples of an aqueous solution of 1-NAA in the flow system. A concentration 0.15 mol L-1 of thallium(I) ions, as heavy atom, both in the samples and the carrier flow, was finally selected. Also, a concentration of 6 mmol L-1 of sulphite was optimal for ensuring the necessary deoxygenation of the system at the selected flow rate of 0.8 mL min-1. After measurement, the solid support was efficiently regenerated by injecting 1 mL of a mixture water:acetone in a ratio 1:1 (v/v) into the flow. The detection limit (3? criterion) was 1.2 ng mL -1 of 1-NAA. The repeatability (RSD) for five replicates of a sample containing 50 ng mL-1 of analyte turned out to be ±3% and the calibration graphs proved to be linear up to 500 ng mL-1 of 1-NAA (maximum concentration assayed). The effect of potential interferences from other organic species which can be also used as plant growth regulators, as well as from various inorganic cations and anions, has been investigated as well. The method was successfully applied to the determination of low levels of this plant growth regulator in natural waters (river and fountain waters) and apples. © 2004 Elsevier B.V. All rights reserved.

"Fast On-line Ultrasound-assisted Extraction Coupled To A Flow Injection-atomic Absorption Spectrometric System For Zinc Determination In Meat Samples"
Talanta 2005 Volume 66, Issue 3 Pages 691-695
M.C. Yebra-BiurrunCorresponding Author Contact Information, E-mail The Corresponding Author, A. Moreno-Cid and S. Cancela-P&eacute;rez

Abstract: A continuous ultrasound-assisted extraction system connected to a flow injection manifold has been used for the on-line determination of zinc in meat samples by flame atomic absorption spectrometry. An experimental design was used for the optimization of the continuous manifold. This flow injection methodology allowed a sampling frequency of ~80 samples per hour with a relative standard deviation for the whole procedure of 0.3% (for a sample containing 163.6 ?g g-1 Zn). The detection limit was 0.6 ?g g-1 for a sample amount of 5 mg. Accurate results were obtained by measuring certified reference materials (BCR-186 (pig kidney) and BCR-184 (bovine muscle)). The analytical procedure was applied to different real meat samples with satisfactory results. © 2004 Elsevier B.V. All rights reserved.

"Sequential Injection-ELISA Based System For Online Determination Of Hyaluronan"
Talanta 2005 Volume 66, Issue 2 Pages 521-527
Supaporn Kradtap Hartwell, Boonraksa Srisawang, Prachya Kongtawelert, Jaroon Jakmunee and Kate Grudpan

Abstract: Sequential injection-bead-based immunoassay system has been developed. The main purpose is to make immunoassay process more automated by manipulating the precise delivery of micro-volumes of reagents and the precise timing of incubation and washing steps with a computer program that controls the bi-directional syringe pump. The manifold was designed with the aims of reducing back pressure from beads that act as solid surfaces for immobilization of the target substance, reducing dispersion and dilution of the reagent during incubation, and maximizing signal while minimizing incubation time. This was done by introducing air segment to separate the reagent zone from the carrier stream and by using a suitable sensitive detector which, in this case, was an amperometer. In this study, hyaluronan (HA) was used as a target analyte because of its clinical significance as a potential biomarker for liver, bone and cancer diseases. Amount of hyaluronan was determined using competitive enzyme linked immuno sorbent assay (ELISA) based technique where immobilized HA and HA in solution compete to bind with a fixed amount of biotinylated HA-binding proteins (b-HABPs). Upon separation of the two phases, anti-biotin conjugated with enzyme and a suitable substrate were introduced to follow the binding reaction of the immobilized HA and b-HABPs whose degree of binding is indirectly proportional to the amount of HA in solution. A calibration curve was constructed from a series of concentrations of HA standards. Lowest detectable concentration was found to be 1 ng/mL with the dynamic working range of 1-5000 ng/mL and RSD of intra-assay (n = 7) and inter-assay (n = 3) of various HA concentrations were 4-10% and 9-12%, respectively. Used beads could be reused by washing with 2 M guanidine. Total analysis time for this automatic assay was about 30 min as compared to the 5-8 h used in conventional batch well ELISA. The system could be applied to assay HA in human serum. © 2004 Elsevier B.V. All rights reserved.

"Evaluation Of On-line Preconcentration And Flow-injection Amperometry For Phosphate Determination In Fresh And Marine Waters"
Talanta 2005 Volume 66, Issue 2 Pages 461-466
Y. Udnan, I.D. McKelvie, M.R. Grace, J. Jakmunee and K. Grudpan

Abstract: Dissolved reactive phosphorus (DRP) was determined as orthophosphate (PO4-P) in fresh and saline water samples by flow-injection (FI) amperometry, without and with in-valve column pre-concentration. Detection is based on reduction of the product formed from the reaction of DRP with acidic molybdate at a glassy carbon working electrode (GCE) at 220 mV versus the Ag/AgCl reference electrode. A 0.1 M potassium chloride solution was used as both supporting electrolyte and eluent in the pre-concentration system. For the FI configuration without pre-concentration, a detection limit of 3.4 ?g P L-1 and sample throughput of 70 samples h-1 were achieved. The relative standard deviations for 50 and 500 ?g P L-1 orthophosphate standards were 5.2 and 5.9%, respectively. By incorporating an ion exchange pre-concentration column, a detection limit of 0.18 ?g P l -1 was obtained for a 2-min pre-concentration time (RSDs for 0.1 and 1 ?g P L-1 standards were 22 and 1.0%, respectively). Potential interference from silicate, sulfide, organic phosphates and sodium chloride were investigated. Both the systems were applied to the analysis of certified reference materials and water samples. © 2005 Elsevier B.V. All rights reserved.

"Determination Of Dissolved Reactive Phosphorus (DRP) And Dissolved Organic Phosphorus (DOP) In Natural Waters By The Use Of Rapid Sequenced Reagent Injection Flow Analysis"
Talanta 2005 Volume 66, Issue 2 Pages 453-460
Orawan Tue-Ngeun, Peter Ellis, Ian D. McKelvie, Paul Worsfold, Jaroon Jakmunee and Kate Grudpan

Abstract: A FI system for rapid sequential determination of dissolved reactive and organic phosphate is described. It utilizes on-line UV photo-oxidation for digestion of dissolved organic phosphate (DOP) with detection of the phosphate produced as phosphomolybdenum blue at 690 nm after reduction of phosphomolybdate with tin(II) chloride. Two injections are performed in the analysis of each sample: the first of sample solution alone enables DRP determination, while the second is of sample plus alkaline peroxydisulfate solutions, which under the photo-oxidation conditions used converts DOP to DRP. The DOP content is evaluated from the difference of the two injections. The digestion efficiency for DOP, evaluated using a range of model organic P compounds of varying stability was greater than 97%. Calibrations were linear over the range of 0.01-6.00 mg P L-1 for both DRP and DRP + DOP graphs, with a detection limit (3 s) of 0.01 mg P L-1 for both species. Relative standard deviations were 0.3% (n = 11, 0.50 mg P l -1) for the DRP determination and 1.0% (n = 11, 0.50 mg P l -1) for the DRP + DOP determination. Injection throughput of 22 h-1 was achieved. The proposed system was validated by analysis of the certified reference materials and comparison with the previous flow injection system. Additional advantage of this system is that it requires the use of only small amounts of the oxidant, with the result that nuisance gas bubble formation is correspondingly minimized. © 2004 Elsevier B.V. All rights reserved.

"An Enzymatic Flow Analysis Method For The Determination Of Phosphatidylcholine In Sediment Pore Waters And Extracts"
Talanta 2005 Volume 66, Issue 2 Pages 445-452
Nahid Amini and Ian McKelvie

Abstract: A sensitive and selective flow injection method for the determination of phosphatidylcholine (PC) in sediment pore waters and extracts is described. It involves the use of phospholipase C, alkaline phosphatase and choline oxidase co-immobilized on controlled pore glass in a packed column reactor. The final product of the enzymatic reaction of phosphatidylcholine is hydrogen peroxide, and this is detected by measuring the chemiluminescence emission resulting from cobalt(II) catalyzed reaction with luminol. The flow injection method is rapid (30 injections/h), reproducible (1.4% RSD at 3 µM PC, n = 10) with a detection limit of 0.14 µM (estimated from 3sn-1 of the measured blank). A linear calibration response was obtained over a concentration range of 0.5-9 µM (r = 0.999). The method has been applied to the determination of phosphatidylcholine in sediment extracts and sediment pore waters.

"An Overview On Flow Methods For The Chemiluminescence Determination Of Phosphorus"
Talanta 2005 Volume 66, Issue 2 Pages 341-347
In&ecirc;s P.A. Morais, Ildik&oacute; V. T&oacute;th and Ant&oacute;nio O.S.S. Rangel

Abstract: A review on the flow analysis of phosphorus with chemiluminescence detection is presented. A brief discussion of the chemiluminescence principles and applications is given. Particular emphasis is devoted to coupling different flow techniques (flow injection, sequential injection, multicommutation, multisyringe flow injection, multi-pumping) to chemiluminescence detection. Enzymatic and non-enzymatic methods, mostly applied to environmental samples, are summarized and compared in terms of application range, detection limits, flow configuration, repeatability and sampling rate.

"Trace And Ultratrace Analysis Methods For The Determination Of Phosphorus By Flow-injection Techniques"
Talanta 2005 Volume 66, Issue 2 Pages 332-340
Shoji MotomizuCorresponding Author Contact Information, E-mail The Corresponding Author and Zhen-Hai Li

Abstract: Trace (?1 mg/l or 30 ?M) and ultratrace (?1 ?g/l or 30 nM) analysis methods for phosphorus determination by flow-injection analysis are reviewed. Most of the methods cited in this review are fundamentally based on the reaction of orthophosphate with molybdate to form heteropoly acids, such as molybdenum yellow and molybdenum blue, and some of the methods are based on the formation of such secondary reactions as ion associates and their aggregates with bulky cations, such as cationic dyes and quaternary ammonium ions. The heteropoly acids themselves can be measured by spectrophotometry, and the ion associate formed with a cationic dye, Malachite Green (MG), can be measured based on the coloration of MG. Light scattering detection methods can be used for measuring the aggregates of ion associates formed with bulky cations. Highly sensitive detection of phosphorus can be accomplished by fluorophotometry; Rhodamine B (RB) and its analogues react with molybdophosphate to form ion associates, which shows fluorescence quenching of RB: LOD is about 5 nM. The detection method based on the chemiluminescence of luminal oxidized with molybdophosphoric acids is probably the most sensitive of all the detection methods reported so far: LOD of the method is as low as 1 nM. The LOD of the molybdenum blue method can be improved by using a liquid core waveguide: LOD is 0.5 nM. © 2005 Elsevier B.V. All rights reserved.

"Flow Analysis Techniques For Phosphorus: An Overview"
Talanta 2005 Volume 66, Issue 2 Pages 307-331
Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: A bibliographical review on the implementation and the results obtained in the use of different flow analytical techniques for the determination of phosphorus is carried out. The sources, occurrence and importance of phosphorus together with several aspects regarding the analysis and terminology used in the determination of this element are briefly described. A classification as well as a brief description of the basis, advantages and disadvantages of the different existing flow techniques, namely; segmented flow analysis (SFA), flow injection analysis (FIA), sequential injection analysis (SIA), all injection analysis (AIA), batch injection analysis (BIA), multicommutated FIA (MCFIA), multisyringe FIA (MSFIA) and multipumped FIA (MPFIA) is also carried out. The most relevant manuscripts regarding the analysis of phosphorus by means of flow techniques are herein classified according to the detection instrumental technique used with the aim to facilitate their study and obtain an overall scope. Finally, the analytical characteristics of numerous flow-methods reported in the literature are provided in the form of a table and their applicability to samples with different matrixes, namely water samples (marine, river, estuarine, waste, industrial, drinking, etc.), soils leachates, plant leaves, toothpaste, detergents, foodstuffs (wine, orange juice, milk), biological samples, sugars, fertilizer, hydroponic solutions, soils extracts and cyanobacterial biofilms are tabulated.
Phosphorus Review

"Non-equilibrium Determination Of Metoclopramide And Tetracaine Hydrochloride By Sequential Injection Spectrophotometry"
Talanta 2005 Volume 66, Issue 1 Pages 236-243
Jing FanCorresponding Author Contact Information, E-mail The Corresponding Author, Aijun Wang, Suling Feng and Jianji Wang

Abstract: A new sequential injection spectrophotometric method was proposed for the determination of metoclopramide and tetracaine hydrochloride. The method was based on the detection of an unstable red intermediate compound resulting from the reaction of metoclopramide or tetracaine hydrochloride with potassium dichromate, in the presence of sodium oxalate, in sulfuric acid solution. The related reaction mechanisms of this new method have been studied. The experimental conditions were optimized for the stopped-flow and continuous-flow sequential injection models. For continuous flow, the linear range for determination of metoclopramide, the detection limit and the sampling frequency were 13-130 ?g mL-1, 9.4 ?g mL-1 and 40 samples per hour, respectively. For stopped flow, they were 3-42 ?g mL-1, 1.0 ?g mL-1 and 18 h-1, respectively. Adopting the continuous-flow model for tetracaine hydrochloride, the linear range was 25-300 ?g mL-1, and the detection limit was 18.0 ?g mL-1 with sampling frequency of 40 h-1. This method has been used to determine metoclopramide and tetracaine hydrochloride in pharmaceutical preparations, and the results are compared with those determined by the pharmacopoeia method. Statistical analysis reveals that there was no evidence of significant difference between the methods. © 2004 Elsevier B.V. All rights reserved.

"The Use Of Anion-exchange Disks In An Optrode Coupled To A Multi-syringe Flow-injection System For The Determination And Speciation Analysis Of Iron In Natural Water Samples"
Talanta 2005 Volume 66, Issue 1 Pages 210-217
Carmen Pons, Rafael Forteza and V&iacute;ctor Cerd&agrave;

Abstract: A combination of multi-syringe flow-injection analysis (MSFIA) technique with an optical fiber reflectance sensor for the determination of iron in water samples has been developed in this work. Anion-exchange solid phase extraction (SPE) disks have been used as solid phase. Ammonium thiocyanate has been chosen as chromogenic reagent for Fe(III). The complex Fe[SCN]63-; is retained onto the SPE disk and spectrophotometrically detected at 480 nm. The complex is eluted with 0.25 mol l-;1 hydrochloric acid in 75% ethanol. Total iron can be determined by oxidising Fe(II) to Fe(III) with hydrogen peroxide. A mass calibration was run within the range of 0.4-37.5 ng. The detection limit (3sb/S) was 0.4 ng. The repeatability (RSD), calculated from 9 replicates using 0.5 mL injections of a 25 µg l-;1 concentration, was 3.6%. The repeatability between five anion-exchange disks was 5.4%. An injection throughput of 7 injections per hour for a sampling volume of 1 mL has been achieved. The applicability of the proposed methodology in natural water samples has been proved. The properties of anion-exchange and chelating SPE disks have been studied and compared.
Iron(2+) Iron(III) NWRI TMDA-54.3 Sensor Spectrophotometry Solid phase extraction Multisyringe Anion exchange disk Complexation

"Electrochemical Determination Of Iodide On A Vanadium Oxide-polypropylene Carbonate Coated Glassy Carbon Electrode"
Talanta 2005 Volume 66, Issue 1 Pages 130-135
Li Tian, Li Liu, Li Chen, Nan Lu and Hongding Xu

Abstract: A vanadium oxide-modified glassy carbon electrode was simply and conveniently fabricated by casting vanadium tri(isoproxide) oxide (VO(OC 3H7)3) and poly(propylene carbonate) (PPC) onto the glassy carbon electrode surface. The electrochemical properties of iodide at the VO(OC3H7)3-PPC film-modified glassy carbon electrode were investigated by cyclic voltammetry, and an anodic peak was observed at approximately +0.71 V (vs. SCE). Based on this, a sensitive and convenient electrochemical method was proposed for the determination of iodide. Flow injection amperometry (FIA) exhibited a good linear relationship with the concentration of iodide in the range of 5 x 10^-7 mol L -1 and 1 x 10^-3 mol L-1, and the detection limit was 1 x 10^-7 mol L-1. Quantitative recovery of iodide in synthetic samples has been obtained and the interferences from different cations and anions have been studied. The method has been successfully applied to the determination of iodide in dry edible seaweed. The concentrations of iodide measured by this method are in good agreement with those obtained by spectrophotometric method. © 2004 Elsevier B.V. All rights reserved.

"Continuous-flow System For Horseradish Peroxidase Enzyme Assay Comprising A Packed-column, An Amperometric Detector And A Rotating Bioreactor"
Talanta 2005 Volume 66, Issue 1 Pages 92-102
Eloy Salinas, Angel A.J. Torriero, Mar&iacute;a I. Sanz, Fernando Battaglini and Julio Raba

Abstract: The roles of chemical kinetics and mass transfer in three types of bioreactors (packed-column reactors, rotating disk bioreactors and amperometric detector), used with continuous-flow sample/reagent(s) processing, are discussed in detail. A normalized quantitative comparison between these types of reactors clearly shows that rotating disk reactors afford a significantly more efficient utilization of active sites and permit the effective utilization of very small amounts of biocatalysts. Horseradish peroxidase (EC 1.11.1.7), in presence of hydrogen peroxide catalyses the oxidation of [Os(bpy)2Cl(pyCOOH)]Cl. The electrochemical reduction back of this cosubstrate is detected on glassy carbon electrode surface at 0.00 V. Furthermore, the critical effect of substrate and cosubstrate concentration on amperometric immunosensors construction in which HRP is used as an enzymatic label was studied. © 2004 Elsevier B.V. All rights reserved.

"Automatic Microdistillation Flow-injection System For The Spectrophotometric Determination Of Fluoride"
Talanta 2005 Volume 66, Issue 1 Pages 80-85
Katsuhisa Shimada, Tetsuro Shimoda, Hisao Kokusen and Shigenori Nakano

Abstract: An automatic flow-injection (FI) system including on-line separation by microdistillation and spectrophotometric detection has been developed for the determination of trace amounts of fluoride. This ion was separated from sample matrix by distillation in the presence of sulfuric and phosphoric acids, and was subsequently determined with spectrophotometry based on the mixed-ligand complex of lanthanum(III)-fluoride-alizarin complexone. The proposed FI system has high sampling frequency (20 samples h-1), small sample size (600 µL) and the dynamic range of 0.05-15 mg L-1 with relative standard deviations of below 1.2%. Interfering ions such as aluminum(III) and iron(III) was effectively eliminated. The method was successfully applied to the determination of fluoride in industrial drainage after water treatment. © 2004 Elsevier B.V. All rights reserved.

"Simultaneous Determination Of Trace Arsenic, Antimony, Bismuth And Selenium In Biological Samples By Hydride Generation-four-channel Atomic Fluorescence Spectrometry"
Talanta 2005 Volume 65, Issue 5 Pages 1318-1325
Zhong-xi LiCorresponding Author Contact Information, E-mail The Corresponding Author and Yue-an Guo

Abstract: A new and sample technique for the simultaneous determination of trace arsenic, antimony, bismuth and selenium in biologic samples by hydride generation-four-channel nondispersive atomic fluorescence spectrometry was development. The conditions of instrumentation and hydride generation of arsenic, antimony, bismuth and selenium were optimized. For reducing hexavalent Se to the tetravalent state was to heat the sample with 6 mol L-1 HCl, and then pre-reducing pentavalent As and Sb to the trivalent state was achieved by the addition of 0.05 mol L-1 thiourea. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for As, Sb, Bi and Se were determined to be 0.03, 0.04, 0.04 and 0.03 ng mL-1, respectively. The precision for seven replicate determinations at the 5 ng mL-1 of As, Sb, Bi and Se were 0.9, 1.2, 1.3 and 1.5% (RSD), respectively. The proposed method was successfully applied to the simultaneous determination of As, Sb, Bi and Se in a series of Chinese certified biological reference materials using simple aqueous standard calibration technique, the results obtained are in good agreement with the certified values. © 2004 Elsevier B.V. All rights reserved.

"Spectrophotometric Flow-injection Determination Of Sulphate In Soil Solutions"
Talanta 2005 Volume 65, Issue 5 Pages 1313-1317
Silvia R.P. Meneses, Nelson Maniasso and Elias A.G. Zagatto

Abstract: A flow-injection procedure for spectrophotometric determination of sulphate in soil solutions is proposed. Samples are directly soaked from the soils under field conditions, in-line filtered through ceramic plates, and preserved with thymol. The method involves reaction with barium dimethylsulphonazo(III) (DMSA) in the presence of dimethylsulphoxide (DMSO) with further measuring the decrease in absorbance at 668 nm. A linear response is observed up to about 5 mgl -1 SO4, and detection limit (3? criterion) is 0.1 mg L-1 SO4. Only 4.5 ?g DMSA is consumed per determination. The system is rugged and baseline drift is not observed during extended operation periods. About 60 samples are injected per hour, and the results are precise (RSD <2%) and in agreement with ion chromatography. © 2004 Elsevier B.V. All rights reserved.

"Optimisation Of Flow-injection-hydride Generation Inductively Coupled Plasma Spectrometric Determination Of Selenium In Electrolytic Manganese"
Talanta 2005 Volume 65, Issue 5 Pages 1209-1214
N. Etxebarria, R. Antol&iacute;n, G. Borge, T. Posada and J.C. Raposo

Abstract: Flow-injection-hydride generation procedure for Se in electrolytic manganese was optimized by means of the experimental design approach. Instrumental variables like power supplied (P), sample (F) and argon (G) flow rates together with chemical variables like NaBH4 and HCl concentrations were studied. In case of the chemical variables, it was concluded that sodium tetrahydridoborate concentrations higher than 1.0% extinguished the plasma while HCl concentration should always be higher than 0.6 mol dm -3. The analysis of effects suggested that all the instrumental variables are significant factors, and the optimum conditions were P = 1550 W, F = 4.75 mL min-1 and G = 0.6 mL min-1. The influence of Mn was specially studied and it was concluded that the interferences were negligible if Mn is below 2.0 g L-1. In the same sense, the interferences of antimony(III), arsenic(V) and mercury(II) were also considered negligible. Finally, a detection limit of 0.0005% (w/w) was obtained (a repeatability RSD <2.0% for all Se concentrations tried). Some manganese samples were also spiked with different concentrations of Se(IV) and the results demonstrated to be in good statistical agreement with expected values. © 2004 Elsevier B.V. All rights reserved.

"Development Of A Solid Surface Fluorescence-based Sensing System For Aluminium Monitoring In Drinking Water"
Talanta 2005 Volume 65, Issue 5 Pages 1203-1208
J.F. Garc&iacute;a Reyes, P. Ortega Barrales and A. Molina D&iacute;az

Abstract: A novel, single and robust solid surface fluorescence-based sensing device assembled in a continuous flow system has been developed for the determination of trace amounts of aluminium in water samples. The proposed method is based on the transient immobilization of the target species on an appropriate active solid sensing zone (C18 silica gel). The target species was the fluorogenic chelate, formed as a result of the on-line complexation of Al(III) with chromotropic acid (CA) at pH 4.1. The fluorescence of the complex is continuously monitored at an emission wavelength of 390 nm upon excitation at 361 nm. The instrumental, chemical and flow-injection variables affecting the fluorescence signal were carefully investigated and optimized. After selecting the most suitable conditions, the sensing system was calibrated in the range 10^-500 ?g l-1, obtaining a detection limit of 2.6 ?g l -1, and a RSD of 2.2%, with a sampling frequency of 24 h -1. In addition, the selectivity of the proposed methodology was evaluated by performing interference studies with different cations and anions which could affect the analytical response. Finally, the proposed method, which meets the EU regulations regarding the aluminium content in drinking waters, was satisfactorily applied to different water samples, with recoveries between 97 and 105%. The simplicity, low cost and easy operation are the main advantages of the present procedure. © 2004 Elsevier B.V. All rights reserved.

"Flow-injection Potentiometric Determination Of Triiodide By Plasticized Poly(vinyl Chloride) Membrane Electrodes And Its Application To The Determination Of Chlorine-containing Disinfectants"
Talanta 2005 Volume 65, Issue 5 Pages 1190-1195
Joaqu&iacute;n A. Ortu&ntilde;oCorresponding Author Contact Information, E-mail The Corresponding Author, Concepci&oacute;n S&aacute;nchez-Pedre&ntilde;o, Jorge Hern&aacute;ndez and Domingo J. Oliva

Abstract: Plasticized poly(vinyl chloride) (PVC) membranes of different compositions were tested for use in the construction of potentiometric flow detectors for triiodide. A membrane with a 2:1 (w/w) 2-nitrophenyl octyl ether to PVC ratio was selected. The influence of thiosulphate in the carrier solution composition and of the flow-injection variables on the determination of triiodide was studied. In the selected conditions, a linear relationship between peak height and log[I3-] was obtained between 5 x 10 -6 and 1 x 10^-4 mol L-1 triiodide. Peak height relative standard deviations for 2 x 10^-5 and 1 x 10^-4 mol L-1 triiodide were ±0.4 and ±1.8%, respectively, and sampling frequency was 80 samples per hour. The method proposed was applied satisfactorily to the iodometric determination of different chlorine-containing disinfectants, among them trichloroisocyanuric acid and dichloroisocyanurate in several types of commercial sample. © 2004 Elsevier B.V. All rights reserved.

"Chemiluminescence Determination Of Carbofuran At Trace Levels In Lettuce And Waters By Flow-injection Analysis"
Talanta 2005 Volume 65, Issue 4 Pages 980-985
Jos&eacute; Fernando Huertas-P&eacute;rez, Laura G&aacute;miz-Gracia, Ana M. Garc&iacute;a-Campa&ntilde;a, Antonio Gonz&aacute;lez-Casado and Jos&eacute; L. Mart&iacute;nez Vidal

Abstract: A simple, fast chemiluminescence (CL) flow-injection (FI) method based on the reaction of luminol with KMnO4 in alkaline medium has been described for the direct determination of carbofuran. The method is based on the enhancing effect in the emission light from the oxidation of luminol produced in presence of carbofuran. The optimization of instrumental and chemical variables influencing the CL response of the method has been carried out by applying experimental design, using the proposed flow-injection manifold. Under the optimal conditions, the CL intensity was linear for a carbofuran concentration over the range of 0.06-0.5 ?g mL-1, with a detection limit of 0.02 ?g mL-1. The method has been successfully applied to the determination of carbofuran residues in spiked water and lettuce samples. © 2004 Elsevier B.V. All rights reserved.

"Flow Injection Spectrophotometric Method For Chloride Determination In Natural Waters Using Hg(SCN)2 Immobilized In Epoxy Resin"
Talanta 2005 Volume 65, Issue 4 Pages 965-970
Claudineia R. Silva, Heberth J. Vieira, Larissa S. Canaes, Joaquim A. N&oacute;brega and Orlando Fatibello-Filho

Abstract: A flow injection (FI) spectrophotometric method was proposed for the determination of chloride ion in natural waters. The determination of chloride was carried out by reaction with Hg(SCN)2 immobilized in an epoxy resin bead in a solid-phase reactor (SPR) and the thiocyanate ions released were determined spectrophotometrically at 480 nm after complexing reaction with Fe(III). The analytical curve for chloride was linear in the concentration range from 5.6 x 10^-5 to 2.2 x 10^-4 mol l -1 with a detection limit of 1.4 x 10^-5 mol l -1. The relative standard deviation (RSD) was 2.2% for a solution containing 2.2 x 10^-4 mol L-1 (n = 10). The simple manifold allows a routine analytical frequency of 100 determinations per hour. The main advantage of the developed method is the 400% reduction of the Hg waste solution generated when compared to conventional methods for chloride determination based on the same spectrophotometric reaction. © 2004 Elsevier B.V. All rights reserved.

"Automatic Flow Procedure Based On Multicommutation Exploiting Liquid-liquid Extraction For Spectrophotometric Lead Determination In Plant Material"
Talanta 2005 Volume 65, Issue 4 Pages 846-852
Ana L&uacute;cia D. Comitre and Boaventura F. Reis

Abstract: A not expensive automatic flow system based on multicommutation and exploiting the liquid-liquid extraction methodology for the determination of lead in plant material is described. The spectrophotometric procedure for lead determination was based on the reaction with dithizone followed by extraction using an organic solvent. The facilities afforded by the multicommutation approach allowed the use of an air stream as carrier, thus contributing to reduce the overall waste generation. The results obtained analyzing plant materials compare very well with those obtained employing inductive coupled plasma optical emission spectrometry (ICP OES) at 90% confidence level. Others profitable features such as a linear response range between 50 and 200 ?g L-1 Pb (r = 0.999); a sampling rate of 15 determination per hour; a relative standard deviation of 1.8% (n = 12) for a typical sample containing 163 ?g L-1 Pb; a detection limit of 12 ?g l-1; a reagent consumption of 4.5 mg dithizone; and a waste generation of 225 µL organic solvent per determination were also achieved. © 2004 Elsevier B.V. All rights reserved.

"Determination Of The Antioxidant Capacity Of Different Food Natural Products With A New Developed Flow Injection Spectrofluorimetry Detecting Hydroxyl Radicals"
Talanta 2005 Volume 65, Issue 3 Pages 769-775
Bo Tang, Li Zhang and Yue Geng

Abstract: This paper presents an automatic spectrofluorimetric method (flow injection analysis spectrofluorimetry) for detecting hydroxyl radicals. Based on H 2O2 catalyzed by Co2+ yielding HO, the method utilized sodium terephthalate to trap hydroxyl radicals and obtained sodium 2-hydroxyterephthalate by aromatic hydroxylation, which resulted in an increase in the fluorescence intensity. The relative fluorescence intensity was proportional to the concentration of hydroxyl radicals. Hydroxyl radicals could be determined indirectly, based on the increase of fluorescence. It was a simple, rapid, precise, sensitive and automatic technique for the determination of HO. The relative standard deviation of 11 determinations was 0.57%. The method can be used to sieve antioxidant medicines and will have theoretical and practical guidance on the mechanism of hydroxyl radicals-damaging biology. © 2004 Elsevier B.V. All rights reserved.

"Determination Of Iodide By Detection Of Iodine Using Gas-diffusion Flow Injection And Chemiluminescence"
Talanta 2005 Volume 65, Issue 3 Pages 756-761
N. Ratanawimarnwong, N. Amornthammarong, N. Choengchan, P. Chaisuwan, M. Amatatongchai, P. Wilairat, I.D. McKelvie and D. Nacapricha

Abstract: This work describes development of a flow injection (FI) system for determination of iodide, based on the chemiluminescence (CL) reaction between iodine and luminol. Iodide in the sample zone is oxidized to iodine. Employment of a gas-diffusion (GD) unit allows for selective detection of the generated CL (425 nm). Preliminary results showed for concentrations of less than 2 mg L -1, that signals were irreproducible and that the calibration was not linear. In order to solve these problems, a method of 'membrane conditioning' was investigated, in which iodide stream was continuously merged with oxidant to generate I2 that conditioned the GD membrane and tubing. This minimized surface interaction between the active surface and the I2 generated from the samples, thus improving both precision and sensitivity. By employing membrane conditioning, it has been possible to reliably detect concentrations down to 0.1 mg L-1. At the optimized condition, an excellent linear calibration (r2 = 0.999) was obtained from 0.1 to 1.0 mg L-1. The method was successfully applied to determine iodide in some pharmaceutical products such as potassium iodide tablets and a liquid patent medicine. However, for vitamin tablets, ascorbic acid was found to interfere seriously by causing a negative signal. © 2004 Elsevier B.V. All rights reserved.

"A Dynamic Liquid-liquid Interfacial Pressure Detector For The Rapid Analysis Of Surfactants In A Flowing Organic Liquid"
Talanta 2005 Volume 65, Issue 3 Pages 722-729
Narong Lenghor, Bethany A. Staggemeier, Mazen L. Hamad, Yuthapong Udnan, Sumalee Tanikkul, Jaroon Jakmunee, Kate Grudpan, Bryan J. Prazen and Robert E. Synovec

Abstract: Design and development of a dynamic interfacial pressure detector (DIPD) is reported. The DIPD measures the differential pressure as a function of time across the liquid-liquid interface of organic liquid drops (i.e., n-hexane) that repeatedly grow in water at the end of a capillary tip. Using a calibration technique based on the Young-Laplace equation, the differential pressure signal is converted, in real-time, to a relative interfacial pressure. This allows the DIPD to monitor the interfacial tension of surface active species at liquid-liquid interfaces in flow-based analytical techniques, such as flow injection analysis (FIA), sequential injection analysis (SIA) and high performance liquid chromatography (HPLC). The DIPD is similar in principle to the dynamic surface tension detector (DSTD), which monitors the surface tension at the air-liquid interface. In this report, the interfacial pressure at the hexane-water interface was monitored as analytes in the hexane phase diffused to and arranged at the hexane-water interface. The DIPD was combined with FIA to analytically measure the interfacial properties of cholesterol and Brij®30 at the hexane-water interface. Results show that both cholesterol and Brij®30 exhibit a dynamic interfacial pressure signal during hexane drop growth. A calibration curve demonstrates that the relative interfacial pressure of cholesterol in hexane increases as the cholesterol concentration increases from 100 to 10,000 µg mL-1. An example of the utility of the DIPD as a selective detector for a chromatographic separation of interface-active species is also presented in the analysis of cholesterol in egg yolk by normal-phase HPLC-DIPD. © 2004 Elsevier B.V. All rights reserved.

"FIA Titrations Of Phenothiazine Derivatives In Aqueous Micellar And Non-aqueous Media"
Talanta 2005 Volume 65, Issue 3 Pages 632-637
Irena N&#283;mcov&aacute;Corresponding Author Contact Information, E-mail The Corresponding Author, Karel Nesm&#283;r&aacute;k, Petr Rychlovsk&yacute; and Jitka Koutn&iacute;kov&aacute;

Abstract: New methods of flow injection analysis (FIA) neutralization titrations of phenothiazine derivatives in aqueous micellar medium of a cationic surfactant using potentiometric and spectrophotometric detection were proposed; titrations with a mixing gradient chamber and high-speed titrations were compared. The FIA titration method in non-aqueous media based on an official method of determination (titration with perchloric acid in anhydrous acetic acid) was also developed. Under optimized reaction conditions and flow-through parameters, the calibration range and equations, the sensitivity, and the repeatability of all methods were found and discussed. All titrations were assayed for medicinal forms. © 2004 Elsevier B.V. All rights reserved.

"On-line Coupling Of Flow Injection Sequential Extraction To Hydride Generation Atomic Fluorescence Spectrometry For Fractionation Of Arsenic In Soils"
Talanta 2005 Volume 65, Issue 3 Pages 627-631
Li-Ming Dong and Xiu-Ping Yan

Abstract: A new flow injection on-line sequential extraction procedure coupled with hydride generation atomic fluorescence spectrometry (HG-AFS) was developed for rapid and automatic fractionation of arsenic in soils. The developed methodology involved a three-step sequential extraction procedure with deionized water, KOH solution, and HCl solution. 25 mg of the soil sample packed into a microcolumn (4 mm i.d. x 3 cm long) was dynamically extracted by continuously pumping each individual extractant through the column. The extracted arsenic solution was merged with 4% (m/v) K2S2O8 solution for on-line oxidation of all arsenic species into As(V). The total extracted arsenic was on-line detected by HG-AFS, and quantitated using an on-line standard addition calibration strategy. The total time for the three-step sequential extraction and on-line detection lasted only 10 min. The developed methodology offers several advantages over conventional batch sequential extraction protocols, including minimization of readsorption/ redistribution problem, improvement of accuracy, high speed, less amounts of sample/reagents required, less risk of contamination and analyte loss. The developed methodology was successfully applied to the fractionation of arsenic in certified soil reference materials. © 2004 Elsevier B.V. All rights reserved.

"Amperometric Determination Of Bonded Glucose With An MnO2 And Glucose Oxidase Bulk-modified Screen-printed Electrode Using Flow-injection Analysis"
Talanta 2005 Volume 65, Issue 2 Pages 559-564
Emir Turkusic, Josef Kalcher, Emira Kahrovic, Negussie W. Beyene, Helmut Moderegger, Emin Sofic, Sabina Begic and Kurt Kalcher

Abstract: A screen-printed amperometric biosensor based on carbon ink double bulk-modified with MnO2 as a mediator and glucose oxidase as a biocomponent was investigated for its ability to serve as a detector for bonded glucose in different compounds, such as cellobiose, saccharose, (-)-4-nitrophenyl-?-d-glucopyranoside, as well as in beer samples by flow-injection analysis (FIA). The biosensor could be operated under physiological conditions (0.1 M phosphate buffer, pH 7.5) and exhibited good reproducibility and stability. Bonded glucose was released with glucosidase in solution, and the free glucose was detected with the modified screen-printed electrode (SPE). The release of glucose by the aid of glucosidase from cellobiose, saccharose and (-)-4-nitrophenyl-?-d-glucopyranoside in solution showed that stoichiometric quantities of free glucose could be monitored in all three cases. The linear range of the amperometric response of the biosensor in the FIA-mode flow rate 0.2 mL min-1, injection volume 0.25 mL, operation potential 0.48 V versus Ag/AgCl) extends from 11 to 13,900 ?mol L-1 glucose in free form. The limit of detection (3?) is 1 ?mol L-1 glucose. A concentration of 100 ?mol L-1 yields a relative standard deviation of approximately 7% with five injections. These values correspond to the same concentrations of bonded glucose supposed that it is liberated quantitatively (incubation for 2 h with glucosidase). Bonded glucose could be determined in beer samples using the same assay. The results corresponded very well with the reference procedure. © 2004 Elsevier B.V. All rights reserved.

"Chromium Speciation And Preconcentration Using Zirconium(IV) And Zirconium(IV) Phosphate Chemically Immobilized Onto Silica Gel Surface Using A Flow System And F AAS"
Talanta 2005 Volume 65, Issue 2 Pages 537-542
Heloisa Fran&ccedil;a Maltez and Eduardo Carasek

Abstract: A procedure for chromium speciation by F AAS using a flow system has been proposed. In this system, Cr(III) and Cr(VI) ions were adsorbed sequentially onto a mini-column packed with silica gel modified with zirconium phosphate and a mini-column packed with silica gel modified with zirconium oxide, respectively. The elution of Cr(III) and Cr(VI) was made with, respectively, nitric acid solution and tris(hydroxymethyl)methylamine (THAM) solution in reverse mode and determination by flame atomic absorption spectrometry without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for Cr(III) and Cr(VI) was 20.8 and 24.9, respectively, using a pre-concentration time of 3.75 min. The limit of detection for Cr(III) and Cr(VI) was 1.9, and 2.3 ?g l-1, respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 100 ?g L-1 of chromium species, by analyzing a series of seven replicates, was lower than 3.0%. The accuracy was assessed through recovery experiments of water samples and using another methodology. © 2004 Elsevier B.V. All rights reserved.

"A Green Analytical Procedure For Flow-injection Determination Of Nitrate In Natural Waters"
Talanta 2005 Volume 65, Issue 2 Pages 461-465
Wanessa Roberto Melchert and F&aacute;bio R.P. Rocha

Abstract: Nitrate determination in waters is generally carried out with cadmium filings and carcinogenic reagents or by reaction with phenolic compounds in highly concentrated sulfuric acid medium. In this work, it was developed a green analytical procedure for nitrate determination in natural waters based on direct spectrophotometric measurements in ultraviolet, using a flow-injection system with an anion-exchange column for separation of nitrate from interfering species. The proposed method employs only one reagent (HClO4) in a minimum amount (equivalent to 18 µL concentrated acid per determination), and allowed nitrate determination within 0.50-25.0 mg L-1, without interference of up to 200.0 mg L-1 humic acid; 1.0 mg L-1 NO2-; 200.0 mg L-1 PO43-; 75.0 mg L-1 Cl-; 50.0 mg L-1 SO 42- and 15.0 mg L-1 Fe3+. The detection limit (99.7% confidence level) and the coefficient of variation (n = 20) were estimated as 0.1 mg L-1 and 0.7%, respectively. The results obtained for natural water samples were in agreement with those achieved by the reference method based on nitrate reduction with copperized cadmium at the 95% confidence level. © 2004 Elsevier B.V. All rights reserved.

"Sequential Fluorometric Quantification Of Malic Acid Enantiomers By A Single Line Flow-injection System Using Immobilized-enzyme Reactors"
Talanta 2005 Volume 65, Issue 2 Pages 396-401
Tadayuki Tsukatani and Kiyoshi Matsumoto

Abstract: A method for the sequential enantiomeric quantification of d-malate and l-malate by a single line flow-injection analysis was developed using immobilized-enzyme reactors and fluorescence detection. An immobilized d-malate dehydrogenase (d-MDH) reactor and an immobilized l-malate dehydrogenase (l-MDH) reactor were introduced into the flow line in series. Sample and coenzyme (NAD+ or NADP+) were injected into the flow line by an open sandwich method. d-Malate was selectively oxidized by d-MDH when NAD + was injected with a sample. When NADP+ was injected with a sample, l-malate was oxidized only by l-MDH. NADH or NADPH produced by the immobilized-enzyme reactors was monitored fluorometrically at 455 nm (excitation at 340 nm). Linear relationships between the responses and concentrations of d-malate and l-malate were observed in the ranges of 1 x 10^-6-1 x 10^-4 M and 1 x 10^-6-2 x 10 -4 M, respectively. The relative standard deviations for ten successive injections were less than 2% at the 0.1 mM level. This analytical method was applied to the sequential quantification of d-malate and l-malate in fruit juices and soft drinks, and the results showed good agreement with those obtained using conventional method (F-kit method). © 2004 Elsevier B.V. All rights reserved.

"Multienzyme Electrochemical Array Sensor For Determination Of Phenols And Pesticides"
Talanta 2005 Volume 65, Issue 2 Pages 349-357
R. Soln&aacute;, S. Sapelnikova, P. Skl&aacute;dal, M. Winther-Nielsen, C. Carlsson, J. Emn&eacute;us and T. Ruzgas

Abstract: The screen-printed four-electrode system was used as the amperometric transducer for determination of phenols and pesticides using immobilized tyrosinase, peroxidase, acetylcholinesterase and butyrylcholinesterase. Acetylthiocholine chloride was chosen as substrate for cholinesterases to measure inhibition by pesticides, hydrogen peroxide served as co-substrate for peroxidase to measure phenols. The compatibility of hydrolases and oxidoreductases working in the same array was studied. The detection of p-cresol, catechol and phenol as well as of pesticides including carbaryl, heptenophos and fenitrothion was carried out in flow-through and steady state arrangements. In addition, the effects of heavy metals (Cu2+, Cd 2+, Fe3+), fluoride (NaF), benzene and dimethylsulphoxide on cholinesterase activities were evaluated. It was demonstrated that electrodes modified with hydrolases and oxidoreductases can function in the same array. The achieved RSD values obtained for the flow system were below 4% for the same sensor and less than 10% within a group of five sensors. For the steady state system, RSDs were approximately twice higher. One assay was completed in less than 6 min. The limit of detection for catechol using tyrosinase was equal to 0.35 and 1.7 ?M in the flow and steady state systems, respectively. On the contrary, lower limits of detection for pesticides were achieved in the steady state system - carbaryl 26 nM, heptenophos 14 nM and fenitrothion 0.58 ?M. © 2004 Elsevier B.V. All rights reserved.

"Comparison Of Two Express Immunotechniques With Polyelectrolyte Carriers, ELISA And FIIAA, For The Analysis Of Atrazine"
Talanta 2005 Volume 65, Issue 2 Pages 324-330
Petra M. Kr&auml;mer, Annette Franke, Anatoly V. Zherdev, Elena V. Yazynina and Boris B. Dzantiev

Abstract: Conventional immunoassays on microtiterplates are very useful analytical tools in environmental analysis, but the long assay times, usually in the range of hours, are a drawback. To overcome this disadvantage, the development of fast (express) assay formats is described, which use polyelectrolytes as carriers. Two semi-homogeneous immunochemical methods, namely the polyelectrolyte-ELISA (enzyme-linked immunosorbent assay) and the express-FIIAA (flow injection immunoaffinity analysis) for the analysis of the herbicide atrazine were set-up. Using polyclonal antisera for atrazine, the following results were obtained. Standard curves for atrazine showed a linear range from 3 to 100 ?g l -1 in polyelectrolyte-ELISA and 0.3-100 ?g L-1 in express-FIIAA. The test midpoints in polyelectrolyte-ELISA and express-FIIAA were 12 and 5 ?g l-1, respectively. The duration time of the immunochemical reaction was in both assays 15 min, but the total assay time differed (30 min (polyelectrolyte-ELISA) and 18 min (express-FIIAA)). A significant difference between the formats could be observed in the number of samples that can be determined per day. The polyelectrolyte-ELISA can handle samples in parallel on a microtiterplate (usually 20/plate), whereas in the express-FIIAA the samples are automatically analyzed one after another. This first demonstration of these techniques shows the potential of these methods, but also their limitations. © 2004 Elsevier B.V. All rights reserved.

"Multivariate Data Analysis Of Dynamic Amperometric Biosensor Responses From Binary Analyte Mixtures - Application Of Sensitivity Correction Algorithms"
Talanta 2005 Volume 65, Issue 2 Pages 298-305
Eva Dock, Jakob Christensen, Mattias Olsson, Erik T&oslash;nning, Tautgirdas Ruzgas and Jenny Emn&eacute;us

Abstract: In this paper, it is demonstrated that a single-receptor biosensor can be used to quantitatively determine each analyte in binary mixtures using multivariate data analysis tools based on the dynamic responses received from flow injection peaks. Mixtures with different concentrations of two phenolic compounds, catechol and 4-chlorophenol, were measured with a graphite electrode modified with tyrosinase enzyme at an applied potential of -50 mV versus Ag/AgCl. A correction algorithm based on measurements of references in-between samples was applied to compensate for biosensor ageing as well as differences caused by deviations between biosensor preparations. After correction, the relative prediction errors with partial least squares regression (PLS-R) for catechol and 4-chlorophenol were 7.4 and 5.5%, respectively, using an analysis sequence measured on one biosensor. Additional validation mixtures of the two phenols were measured with a new biosensor, prepared with the same procedure but with a different batch of tyrosinase enzyme. Using the mixture responses for the first sensor as a calibration set in PLS-R, the relative prediction errors of the validation mixtures, after applying correction procedures, were 7.0% for catechol and 16.0% for 4-chlorophenol. These preliminary results indicate that by applying correction algorithms it could be possible to use less stable biosensors in continuous on-line measurements together with multivariate data analysis without time-consuming calibration procedures. © 2004 Elsevier B.V. All rights reserved.

"Flow Injection Analysis System For Monitoring Of Succinic Acid In Biotechnological Processes"
Talanta 2005 Volume 65, Issue 1 Pages 185-191
Ok-Jae Sohn, Kyung-Ah Han and Jong Il Rhee

Abstract: In this study, a flow injection analysis (FIA) system using a cartridge of immobilized isocitrate lyase (ICL) and isocitrate dehydrogenase (ICDH) was developed to monitor the concentrations of succinic acid in biotechnological processes. The ICL and ICDH immobilized on VA-Epoxy Biosynth E3-carrier had a good operational lifetime (up to 24 h) and storage stability (up to 30 days). The FIA system with the immobilized ICL/ICDH cartridge was characterized with respect to the factors affecting the activity of the immobilized enzymes, such as pH of carrier solution, temperature, sample matrix, etc. Optimal pH value of the immobilized enzymes was slightly shifted in the alkaline range, i.e. 9.0. Some components such as 10 g L-1 lactose, 3 g L-1 malate and 3 g L-1 oxaloacetate in sample solution had significant activating effects (more than 10%) on the response of the FIA system. But the activity of the immobilized ICL and ICDH was not largely influenced by some components like imidazole (1 mM), sodium azide (10 mM) and semicarbazide (2 g l-1) added to carrier buffer solution. The FIA system with an enzyme cartridge was applied to on-line monitor the concentrations of succinic acid in a continuously stirred reactor and a fermentation process of immobilized Escherichia coli, and showed good sensitivity and reliability of the FIA system developed in this work. © 2004 Elsevier B.V. All rights reserved.

"Speciation Of Cr(III) And Cr(VI) In Waters Using Immobilized Moss And Determination By ICP-MS And FAAS"
Talanta 2005 Volume 65, Issue 1 Pages 135-143
M. V. Balarama KrishnaE-mail The Corresponding Author, K. Chandrasekaran, Sarva V. Rao, D. Karunasagar and J. Arunachalam

Abstract: The possibility of using moss (Funaria hygrometrica), immobilized in a polysilicate matrix as substrate for speciation of Cr(III) and Cr(VI) in various water samples has been investigated. Experiments were performed to optimize conditions such as pH, amount of sorbent and flow rate, to achieve the quantitative separation of Cr(III) and Cr(VI). During all the steps of the separation process, Cr(III) was selectively sorbed on the column of immobilized moss in the pH range of 4-8 while, Cr(VI) was found to remain in solution. The retained Cr(III) was subsequently eluted with 10 mL of 2 mol L-1 HNO3. A pre-concentration factor of about 20 was achieved for Cr(III) when, 200 mL of water was passed. The immobilized moss was packed in a home made mini-column and incorporated in flow injection system for obtaining calibration plots for both Cr(III) and Cr(VI) at low ppb levels that were compared with the plots obtained without column. After separation, the chromium (Cr) species were determined by inductively coupled plasma mass spectrometry (ICP-MS) and flame atomic absorption spectrometry (FAAS). The sorption capacity of the immobilized moss was found to be ?11.5 mg g-1 for Cr(III). The effect of various interfering ions has also been studied. The proposed method was applied successfully for the determination of Cr(III) and Cr(VI) in spiked and real wastewater samples and recoveries were found to be >95%. © 2004 Published by Elsevier B.V.

"Direct Determination Of Total Carbonate Salts In Soil Samples By Continuous-flow Piezoelectric Detection"
Talanta 2005 Volume 65, Issue 1 Pages 29-35
Mohammed Zougagh, Angel R&iacute;os and Miguel Valc&aacute;rcel

Abstract: Two new methods for the determination of total carbonate salts, as CaCO3, in soil by continuous-flow piezoelectric (PZ) detection are proposed. Both use a piezoelectric flow cell and a manifold including a dynamic gas extraction device to purge gaseous CO2 released by the sample solution upon acidification. One of the methods involves monitoring the pressure generated by the CO2 produced upon addition of hydrochloric acid; in the other, the CO2 is quantified by using a quartz crystal coated with tetramethylammonium fluoride tetrahydrate (TMAF). The precision of both methods is compared with that of the officially endorsed method. The proposed methods allow calcium carbonate amounts over the ranges 10^-100 mg and 2-15 mg, respectively, to be determined. Both were applied to the determination of CaCO3 in soil samples. The standard deviation and throughput achieved were 2.7% and 30 samples per hour, respectively, with the pressure-based method; and 6.0% and six samples per hour, respectively, with the mass-based method. © 2004 Elsevier B.V. All rights reserved.

"HPLC Determination Of Vitamin D3 And Its Metabolite In Human Plasma With On-line Sample Cleanup"
Talanta 2004 Volume 64, Issue 5 Pages 1364-1370
M. R. Brunetto, M. A. Obando, M. Gallignani, O. M. Alarc&oacute;n, E. Nieto, R. Salinas, J. L. Burguera and M. Burguera

Abstract: A HPLC method with automated column switching and UV-diode array detection is described for the simultaneous determination of Vitamin D3 and 25-hydroxyvitamin D3 (25-OH-D3) in a sample of human plasma. The system uses a BioTrap precolumn for the on-line sample cleanup. A sample of 1 mL of human plasma was treated with 2 mL of a mixture of ethanol-acetonitrile (2:1 (v/v)). Following centrifugation, the supernatant was evaporated to dryness under a stream of dry and pure nitrogen. The residue was reconstituted in 250 µL of a solution of methanol 5 mmol L-1 phosphate buffer, pH 6.5 (4:1 (v/v)), and a 200 µl aliquot of this solution was injected onto the BioTrap precolumn. After washing during 5 min with a mobile phase constituted by a solution of 6% acetonitrile in 5 mmol L-1 phosphate buffer, pH 6.5 (extraction mobile phase), the retained analytes were then transferred to the analytical column in the backflush mode. The analytical separation was then performed by reverse-phase chromatography in the gradient elution mode with the solvents A and B (Solvent A: acetonitrile-phosphate buffer 5 mmol l-1, pH 6.5; 20:80 (v/v); solvent B: methanol-acetonitrile-tetrahydrofuran, 65:20:15 (v/v)). The compounds of interest were detected at 265 nm. The method was linear in the range 3.0-32.0 ng mL-1 with a limit of quantification of 3.0 ng mL-1. Quantitative recoveries from spiked plasma samples were between 91.0 and 98.0%. In all cases, the coefficient of variation (CV) of the intra-day and inter-day-assay precision was 3 and 25-OH-D3 in 16 min, with an adequate precision and sensitivity. However, the overlap of the sample cleanup step with the analysis increases the sampling frequency to five samples h-1. The method was successfully applied for the determination of Vitamin D3 and 25-OH-D3 in plasma from 46 female volunteers, ranging from 50 to 94 years old. Vitamin D3 and 25-OH-D3 concentrations in plasma were found from 4.30-40.70 ng mL-1 (19.74±9.48 ng mL-1) and 3.1-36.52 ng mL-1 (7.13±7.80 ng mL-1), respectively. These results were in good agreement with data published by other authors.

"Determination Of Insolubles In Diesel Lubricating Oil By FIA-visible Spectrometry"
Talanta 2004 Volume 64, Issue 5 Pages 1359-1363
M. Knochen, A. Sixto, G. Pignalosa, S. Domenech, S. Garrigues and M. de la Guardia

Abstract: Insolubles determination is one of the parameters usually recommended to evaluate the residual life of oil because their presence at elevated levels in diesel lubricating oil changes the viscosity, prematurely clogs filters and is one of the major factors in causing abrasive engine wear. The proposed method employs visible spectrophotometric detection in association with flow injection analysis. The results obtained by this method were compared with the ones obtained by Fourier transform infrared spectrometry (FT-IR) since this is the most employed method for insolubles determination. The proposed method presented a linear response from 0 to 3% (w/w) of insolubles in pentane (ASTM D-893). The sampling frequency was about 30 samples h-1, with a relative standard deviation (n=5) of 2.4% or better.Accuracy was evaluated analyzing 98 real samples and the results obtained with the FIA-spectrophotometric method were plotted against those obtained by the FT-IR method by means of linear regression. Slope and intercept of the straight line obtained were compared with the theoretical values of 1 and 0 by means of the joint-confidence ellipse F-test. At the confidence level of 95% no evidence of a difference was found between both methods.

"Continuous Flow System For Lead Determination By Faas In Spirituous Beverages With Solid Phase Extraction And On-line Copper Removal"
Talanta 2004 Volume 64, Issue 5 Pages 1351-1358
Yaneira Petit de Pe&ntilde;a, Boris Paredes, Wendy Rond&oacute;n, Marcela Burguera, Jos&eacute; Luis Burguera, Carlos Rond&oacute;n, Pablo Carrero and Tarcisio Capote

Abstract: A continuous flow system for the determination of lead in home made spirituous beverages was developed. The determination was based on the formation of a neutral chelate of the element with ammonium pyrrolidine dithiocarbamate, its adsorption onto a minicolumn packed with sodium faujasite type Y synthetic zeolite, followed by elution with methyl isobutyl ketone and determination by flame atomic absorption spectrometry. Ethanol and copper interfere strongly in the determination and therefore, must be separated prior to the analysis. Copper is removed by precipitation with rubeanic acid, while ethanol is eliminated by rotaevaporation. Sample solutions containing Pb2+ in the concentration range from 5 to 120 µg L-1 at pH 2.5 could be analyzed, by using a pre-concentration time of 3 min. Preconcentration factors from 80 to 140 were achieved for a sample volume of 6 mL and the detection limit varied from 1.4 to 3.5 µg l-1, depending on the matrix composition. The relative standard deviations for 60 µg L-1 Pb was 3.2% (n = 10) and the recovery of spikes (20, 40, 60 and 80 µg l-1) added to the samples was estimated within 92-105% range, suggesting that lead can be quantitatively determined in such samples. Determining lead in several samples by an alternative technique further checked the accuracy. Finally, the concentrations of Pb2+ determined in 28 samples of Venezuelan spirituous beverages were in 12.6-370.0 µg L-1 range, depending on the fermenting material based on different mixtures of agave, raw sugar cane and white sugar.

"A Sequential Injection Method For The Determination Of Piroxicam In Pharmaceutical Formulations Using Europium Sensitized Fluorescence"
Talanta 2004 Volume 64, Issue 5 Pages 1343-1350
Salma M. Z. Al-Kindy, Aisha Al-Wishahi and Fakhr Eldin O. Suliman

Abstract: A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu3+) by complexation with PX. The signal for PX-EU is monitored at λex=358 nm and λem=615 nm. Optimum conditions for the formation of the complex in methanol were 0.01 M TRIS buffer and 0.2 mM of Eu3+ which allows the determination of 100-2000 ppb of pX in batch method and 100-1000 ppb with limit of detection (LOD) = 23.0 ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0±0.3 and 98.8±2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.

"Preconcentration And Determination Of Inorganic Arsenic Using A Multisyringe Flow Injection System And Hydride Generation-atomic Fluorescence Spectrometry"
Talanta 2004 Volume 64, Issue 5 Pages 1335-1342
L. O. Leal, N. V. Semenova, R. Forteza and V. Cerd&agrave;

Abstract: A new multisyringe flow injection system for inorganic arsenic determination at trace levels by hydride generation-atomic fluorescence spectrometry (HGAFS) is presented. Preconcentration on a solid-phase was carried out using a column packed with an anion-exchange resin (Amberlite IRA-410). The reagents are dispensed to the system using a multisyringe burette coupled with two multi-port selection valves. Different parameters were changing in order to make the system as effective as possible. An analytical curve was obtained for arsenic determination between 50 and 2000 ng l-1. This new approach improved five times the sensitivity over a MSFIA-HGAFS technique developed previously by the authors. Detection limit of the proposed technique was (3sb/S) of 30 ng l-1. The relative standard deviation (RSD) of As at 1 µg L-1 was 4.8% (n=7). A sample throughput of 10 h-1 has been achieved. The proposed method has been applied to different reference solid and water materials with satisfactory results.
Arsenic, inorganic NRCC DOLT-1 NRCC DORM-1 LGC 6010 Fluorescence Preconcentration Solid phase extraction Amberlite Multisyringe Sensitivity Optimization

"Developing An On-line Derivatization Of FAs By Microwave Irradiation Coupled To HPLC Separation With UV Detection"
Talanta 2004 Volume 64, Issue 5 Pages 1329-1334
B&eacute;lgica Bravo, Gerson Ch&aacute;vez, Nolberto Pi&ntilde;a, Fredy Ysambertt, Nelson M&aacute;rquez and Ana C&aacute;ceres

Abstract: The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water-microemulsion-oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet-violet (UV-Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV-Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450 W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW-HPLC-UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water-microemulsion-oil systems, to quantify the total acid fraction in each phase.

"Determination Of Aliphatic Alcohols After On-line Microwave-assisted Derivatization By Liquid Chromatography-photodiode Array Detection"
Talanta 2004 Volume 64, Issue 5 Pages 1323-1328
Gerson Ch&aacute;vez, B&eacute;lgica Bravo, Nolberto Pi&ntilde;a, M&oacute;nica Arias, Eliseo Vivas, Fredy Ysambertt, Nelson M&aacute;rquez and Ana C&aacute;ceres

Abstract: In this study, high-performance liquid chromatography (HPLC) in conjunction with continuous derivatization for the determination of aliphatic and polyethoxylated alcohol is reported. Reaction of alcohol group with phenyl isocyanate or benzyl chloride reagents assisted with microwaves (MW) irradiation is carried out in an on-line system coupled to HPLC with photodiode array detection (PDA). Reactor was placed into a microwave oven at 450 W. The flow rate, reagent amounts, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the system MW-HPLC-PDA provided high sensitivity, reduce the amount of reagents and analysis time. This proposed method can be used for the analysis of commercial alcohol polyethoxylated mixture.

"Nafion-based Optical Sensor For The Determination Of Selenium In Water Samples"
Talanta 2004 Volume 64, Issue 5 Pages 1317-1322
Lilibeth dlC. Coo and Imee Su Martinez

Abstract: An optical chemical sensor responsive to selenium (SeO32-) in water samples was developed. Its matrix was nafion membrane suffused with an organic ligand p-amino-p'-methoxydiphenylamine or variamine blue (VB). The method of analysis was flow injection (FI) where in the membrane was fixed in a flow-through demountable measuring cell and connected to a computer-controlled simple spectrophotometer.Variamine blue was previously established to determine amounts of selenium in water and other media by means of a spectrophotometer. The method involved reacting selenite with potassium iodide to generate iodine gas, which reacts with variamine blue to form a colored species.Experimental results showed the optrode to be an effective tool in analyzing the selenium content of water samples particularly for remote or in situ applications. Interference studies proved that the method is free of intervention from tested ions.

"Flow Injection Determination Of Bismuth In Urine By Successive Retention Of Bi(III) And Tetrahydroborate(III) On An Anion-exchange Resin And Hydride Generation Atomic Absorption Spectrometry"
Talanta 2004 Volume 64, Issue 5 Pages 1309-1316
Pablo Carrero, Luis Guti&eacute;rrez, Carlos Rondon, Jos&eacute; Luis Burguera, Marcela Burguera and Yaneira Petit de Pea

Abstract: Bismuth as BiCl4- and BH4- ware successively retained in a column (150 mm X 4 mm, length X i.d.) packed with Amberlite IRA-410 (strong anion-exchange resin). This was followed by passage of an injected slug of hydrochloric acid resulting in bismuthine generation (BiH3). BiH3 was stripped from the eluent solution by the addition of a nitrogen flow and the bulk phases were separated in a gas-liquid separator. Finally, bismutine was atomized in a quartz tube for the subsequent detection of bismuth by atomic absorption spectrometry. Different halide complexes of bismuth (namely, BiBr4-, BiI4- and BiCl4-) were tested for its pre-concentration, being the chloride complexes which produced the best results. Therefore, a concentration of 0.3 mol L-1 of HCl was added to the samples and calibration solutions. A linear response was obtained between the detection limit (3s) of 0.225 and 80 µg l-1. The RSD% (n = 10) for a solution containing 50 µg L-1 of Bi was 0.85%. The tolerance of the system to interferences was evaluated by investigating the effect of the following ions: Cu2+, Co2+, Ni2+, Fe3+, Cd2+, Pb2+, Hg2+, Zn2+, and Mg2+. The most severe depression was caused by Hg2+, which at 60 mg L-1 caused a 5% depression on the signal. For the other cations, concentrations between 1000 and 10,000 mg L-1 could be tolerated. The system was applied to the determination of Bi in urine of patients under therapy with bismuth subcitrate. The recovery of spikes of 5 and 50 µg L-1 of Bi added to the samples prior to digestion with HNO3 and H2O2 was in satisfactory ranges from 95.0 to 101.0%. The concentrations of bismuth found in six selected samples using this procedure were in good agreement with those obtained by an alternative technique (ETAAS). Finally, the concentration of Bi determined in urine before and after 3 days of treatment were 1.94 [plus-or-minus sign] 1.26 and 9.02 [plus-or-minus sign] 5.82 µg l-1, respectively.

"Design Of A Flow Injection Method For Chlorophyll Determination In In Vitro Plants"
Talanta 2004 Volume 64, Issue 5 Pages 1304-1308
Juan Manuel L&oacute;pez, Rosa Elena Lucena, Lu&eacute; Mer&uacute; Marc&oacute; P., Norca Mogoll&oacute;n, Ricardo Rivas and Alvaro Anzalone G.

Abstract: A flow injection (FIA) method was designed for the determination of chlorophylls a and b in small in vitro Dieffenbachia maculata 'Sublime' plants. In the first step, the pigments from spinach leaves were separated, purified by solvent extraction and freeze-dried, to obtain standards for the FIA optimization. The sample extraction procedure was optimized. Four solvents were tested: diethyl ether, methanol, acetone and ethanol. The ethanol 96% was the optimal solvent for FIA purposes. It allows to the efficient extraction of the pigments and water can be used as carrier. The best FIA conditions found for the quasi-simultaneous quantification of chlorophylls a and b were a flow rate of 10.84 mL min-1, a sample injection volume of 1.45 mL and a reactor length of 63 cm. The detection was performed with the automatic wavelength scanning Cintra 10e spectrometer, at 649 and 665 nm. The results obtained by the FIA method were compared to those obtained by the Arnon method. A deviation less than 5% was found between results for both methods. The concentration (mg g-1) of chlorophylls a and b during three periods of the plants (in vitro, acclimatization, and adult) was determined to evaluate the whole in vitro procedure. It was found an increment of both pigment concentrations since the in vitro step till the adult stage, while the chlorophylls a to b ratio decreases. The designed method is suitable especially for the determination of the pigments at low concentrations in small samples with appropriate analytical quality.

"Pungency Evaluation Of Onion Cultivars From The Venezuelan West-Center Region By Flow Injection Analysis-UV-visible Spectroscopy Pyruvate Determination"
Talanta 2004 Volume 64, Issue 5 Pages 1299-1303
Pineda Marcos, Marc&oacute; P. Lu&eacute;-Mer&uacute;, Rivas Ricardo, Gallignani M&aacute;ximo, Valero Maribel, Burguera Jos&eacute; Luis and Burguera Marcela

Abstract: A flow injection analysis (FIA) method was developed for the determination of pyruvate in onion cultivars (Allium cepa L.) from the West-Center region of Venezuela. The reference Schwimmer and Weston (1961) (J. Agric. Food Chem. 9 (1961) 301) Batch method was modified and adapted to FIA conditions. The formation kinetic of the 2,4-dinitrophenylhydrazine (DNPH)-pyruvate complex was evaluated at room temperature and at 37°C. It was demonstrated the suitability of the chromopher formation at room temperature. The optimal values for the FIA parameters were: sample injection volume 3 mL, flow rate 6 mL min-1, reactor length 1.5 m, sodium hydroxide concentration 1.0 mol L-1 and hydrochloric acid concentration 0.5 mol L-1. The working calibration range was extended from 80 mg L-1 (Batch method) to 700 mg L-1 with the FIA set up. The sample dilution step is thus avoided, simplifying the whole analysis process. The pungency in representative samples of the cultivars Yellow granex 438, Ultra Hybrid and Red onion 'Sangre de Toro' was evaluated by the flow injection analysis (FIA)-pyruvate method and the results were compared to the reference Batch pyruvate method and to the taste panel test. Non-significant differences were found at the 95% of confidence level between the FIA method and the Batch reference method. Correlation coefficient when comparing the FIA results to the taste panel test was r2 = 0.8353. Significant differences (P < 0.05) were found in the pungency of the cultivars, the Ultra Hybrid having the highest pungency. The pungency order from minor to major was: Red onion, Texas Grano 438 and Ultra Hybrid.

"Flow Analysis-vapor Phase Generation-Fourier Transform Infrared (FA-VPG-FTIR) Spectrometric Determination Of Nitrite"
Talanta 2004 Volume 64, Issue 5 Pages 1290-1298
M&aacute;ximo Gallignani, Maribel Valero, Carlos Ayala, Maria del Rosario Brunetto, Argenis S&aacute;nchez, Jose Luis Burguera and Marcela Burguera

Abstract: In this work, the coupling between flow analysis (FA)-vapor phase generation (VPG) and Fourier transform infrared spectrometry (FTIR) has been proposed as a novel and alternative strategy for the determination of nitrite. The analyte was transformed into the gaseous nitric oxide (NO) by on-line reaction with potassium iodide (KI) or ascorbic acid in acidic medium. The gaseous NO generated was transported by means of a N2 gas carrier stream inside the IR gas cell and the corresponding FTIR spectrum was acquired in a continuous mode. The absorbance at 1876 cm-1, corrected by a baseline established between 1879 and 1872 cm-1 at a nominal resolution of 2 cm-1, was selected as a measurement criterion. The effect of different spectroscopic and flow analysis experimental parameters, such as nominal resolution, number of scans, reducing agent and its concentration, acidic medium, reagents and sample flow rates, and the carrier gas flow rate on the analytical signal, and then in the figures of merit were initially evaluated by using a standard short path length (10 cm) IR gas cell. The optimization of the system was carried out by the univariate method. The main aims of this study were: (i) to investigate the on-line generation of gaseous nitric oxide in a continuous flow system, and (ii) the use of Fourier transform infrared spectrometry as an alternative and selective detector for the determination of nitrite. The proposed method was initially tested and applied for the determination of nitrite in samples with very high concentration of nitrite, such as frankfurters.

"Multi-syringe Flow Injection System With In-line Microwave Digestion For The Determination Of Phosphorus"
Talanta 2004 Volume 64, Issue 5 Pages 1283-1289
M. In&ecirc;s G. S. Almeida, Marcela A. Segundo, Jos&eacute; L. F. C. Lima and Ant&oacute;nio O. S. S. Rangel

Abstract: A multi-syringe system for spectrophotometric determination of total phosphorus involving in-line digestion is proposed. Sample and digestion solution were dispensed and directed towards a digestion vessel located inside a domestic microwave oven (MWO) where sample digestion took place. Afterwards, the digested sample was merged with the necessary reagents for the colorimetric determination based on the molybdenum blue method. Several digestion conditions were studied regarding composition of digestion solution, digestion time and power set on the MWO. The system was applied to waste water samples and results shown a good agreement with the reference method. Repeatable results (RSD-1 were obtained.

"Fluorometric Determination Of Urea In Alcoholic Beverages By Using An Acid Urease Column-FIA System"
Talanta 2004 Volume 64, Issue 5 Pages 1278-1282
Y. Iida, M. Ikeda, M. Aoto and I. Satoh

Abstract: An acid urease column was applied to a fluorometric flow-injection analysis (FIA) system as a recognition element for determination of urea in rice wines. The acid urease has specific properties of showing its catalytic activity in low pH range and tolerance to ethanol in comparison to those of a urease from jack-beans. The enzymes were covalently immobilized onto porous glass beads with controlled pore size and then, packed into a small polymer column. The flow-type of the biosensing system was assembled with a sample injection valve, the immobilized enzyme column, and a flow-through quartz cell attached to a fluorescent spectrophotometer. Citrate buffer (50 mM, pH 5.0) as the carrier solution was continuously pumped through the system. Sample solutions were introduced into the system via a rotary injection valve. A standard urea solution was measured through monitoring variations in fluorescent intensity attributable to fluorescent isoindole derivatives formed by coupling with ammonia molecules released in the enzymatic hydrolysis of urea and orthophthalaldehyde reagents. The fluorescent intensity was measured under the conditions of λex = 415 nm and λem = 485 nm. A wide, linear relationship was obtained between the concentration of urea (1.0-100 µM) and the variation in fluorescent intensity. The monitoring did not suffer from ethanol and various amino acids contained in rice wines. Real samples pretreated with ion exchange resins for removal of endogenous ammonia were introduced into the FIA system and urea in the samples was determined. These results were compared with those obtained with use of an F-kit method. The proposed FIA system should present sensitive, selective and convenient analysis of urea in alcoholic beverages.

"Repetitive Determination Of Ascorbic Acid Using Iron(III)-1.10-phenanthroline-peroxodisulfate System In A Circulatory Flow Injection Method"
Talanta 2004 Volume 64, Issue 5 Pages 1273-1277
Michio Zenki, Akihiro Tanishita and Takashi Yokoyama

Abstract: Ascorbic acid (AA) could be determined in large quantities of a co-existing oxidant. The incorporation of an on-line reagent regeneration step based on redox reaction eliminates the baseline drift in the procedure. This makes it possible to adopt a circulatory flow injection method (cyclic FIA) and to determine AA repetitively. The method is based on the reduction of iron(III) to iron(II) by the analyte, the reaction of the produced iron(II) with 1,10-phenanthroline (phen) in a weak acidic medium to form a colored complex, and the subsequent oxidation reaction of iron(II) to iron(III) by the co-existing peroxodisulfate. A solution (50 ml) of 3.0 x 10^-4 mol L-1 ferric chloride, 9.0 x 10^-4 mol L-1 phen and 5.0 x 10^-2 mol L-1 ammonium peroxodisulfate in acetate buffer (0.2 mol l-1, pH 4.5) is continuously circulated at a constant flow rate of 1.0 mL min-1. Into this stream, an aliquot (20 µl) of the sample solution containing AA is quickly injected by means of a six-way valve. The complex formed is monitored spectrophotometrically (at 510 nm) in the flow system. The stream then returns to the reservoir after passing through a time-delay coil (50 m). The iron(II)-(phen)3 complex is oxidized to iron(III)-(phen)3 complex by peroxodisulfate which exists excessively in the circulating reagent solution. The proposed method allows as many as 300 repetitive determinations of 15 mg L-1 AA with only 50 mL reservoir solution. The contents of AA in commercial pharmaceutical products were analyzed to demonstrate the capability of the developed system.

"Flow-injection Simultaneous Determination Of Selenium(IV) And Selenium(IV + VI) Using Photooxidative Coupling Of P-hydrazinobensenesulfonic Acid With N-(1-naphthyl)ethylenediamine"
Talanta 2004 Volume 64, Issue 5 Pages 1266-1272
Shigenori Nakano, Masahiro Yoshii and Takuji Kawashima

Abstract: A flow-injection spectrophotometric method has been developed for the simultaneous determination of selenium(IV) and (IV + VI) at nanogram per milliliter levels. It is based on the catalytic effect of selenium(IV) on the photooxidative coupling of p-hydrazinobenzenesulfonic acid (HBS) with N-(1-naphthyl)ethylenediamine (NED) to form an azo dye (λmax = 538 nm). In this reaction, bromide acted as an activator for the catalysis of selenium(IV) and an reducer for selenium(VI) to selenium(IV) in an acidic medium which allowed the determination of selenium(IV + VI). A sample solution, being split by Y-piece into two portions, passed through the low-temperature coil (4 m, 25°C) and the high-temperature coil (20 m, 100°C). By monitoring the absorbance of the dye produced in the two portions, selenium(IV) and (IV + VI) in the range of 0.2-6 ng mL-1 were determined simultaneously. The relative standard deviations for 3 ng mL-1 selenium(IV) and (VI) (n = 10) were 1.2 and 1.3%, respectively. There were few interfering ions in the selenium determination. The proposed method was applied to the determination of selenium(IV) and (VI) in natural water samples.

"Simple Flow-injection System For The Simultaneous Determination Of Nitrite And Nitrate In Water Samples"
Talanta 2004 Volume 64, Issue 5 Pages 1259-1265
Rodjana Burakham, Mitsuko Oshima, Kate Grudpan and Shoji Motomizu

Abstract: A novel spectrophotometric reaction system was developed for the determination of nitrite as well as nitrate in water samples, and was applied to a flow-injection analysis (FIA). The spectrophotometric flow-injection system coupled with a copperised cadmium reductor column was proposed. The detection was based on the nitrosation reaction between nitrite ion and phloroglucinol (1,3,5-trihydroxybenzene), a commercially available phenolic compound. Sample injected into a carrier stream was split into two streams at the Y-shaped connector. One of the streams merged directly and reacted with the reagent stream: nitrite ion in the samples was detected. The other stream was passed through the copperised cadmium reductor column, where the reduction of nitrate to nitrite occurred, and the sample zone was then mixed with the reagent stream and passed through the detector: the sum of nitrate and nitrite was detected. The optimized conditions allow a linear calibration range of 0.03-0.30 µg NO2--N mL-1 and 0.10-1.00 µg NO3--N mL-1. The detection limits for nitrite and nitrate, defined as three times the standard deviation of measured blanks are 2.9 ng NO2--N mL-1 and 2.3 ng NO3--N mL-1, respectively. Up to 20 samples can be analyzed per hour with a relative standard deviation of less than 1.5%. The proposed method could be applied successfully to the simultaneous determination of nitrite and nitrate in water samples.

"Flow-injection Determination Of Iodide Ion In Nuclear Emergency Tablets, Using Boron-doped Diamond Thin Film Electrode"
Talanta 2004 Volume 64, Issue 5 Pages 1253-1258
O. Chailapakul, M. Amatatongchai, P. Wilairat, K. Grudpan and D. Nacapricha

Abstract: The electrochemical determination of iodide was studied at boron-doped diamond thin film electrodes (BDD) using cyclic voltammetry (CV) and flow-injection (FI) analysis, with amperometric detection. Cyclic voltammetry of iodide was conducted in a phosphate buffer pH 5. Experiments were performed using glassy carbon (GC) electrode as a comparison. Well-defined oxidation waves of the quasi-reversible cyclic voltammograms were observed at both electrodes. Voltammetric signal-to-background ratios (S/B) were comparable. However, the GC electrode gives much greater in the background current as usual. The potential sweep rate dependence exhibited that the peak current of iodide oxidation at 1 mM varied linearly (r2 = 0.998) with the square root of the scan rate, from 0.01 to 0.30 V s-1. This result indicates that the reaction is a diffusion-controlled process with negligible adsorption on BDD surface, at this iodide concentration. Results of the flow-injection analysis show a highly reproducible amperometric response. The linear working range was observed up to 200 µM (r2 = 0.999). The detection limit, as low as 0.01 µM (3s of blank), was obtained. This method was successfully applied for quantification of iodide contents in nuclear emergency tablets.

"Flow Injection Analysis Of Doxycycline Or Chlortetracycline In Pharmaceutical Formulations With Pulsed Amperometric Detection"
Talanta 2004 Volume 64, Issue 5 Pages 1247-1252
Thiraporn Charoenraks, Sanit Palaharn, Kate Grudpan, Weena Siangproh and Orawon Chailapakul

Abstract: A flow injection with pulsed amperometric detection for determination of doxycycline or chlortetracycline in pharmaceutical formulations is described. Doxycycline or chlortetracycline were studied at a gold rotating disk electrode with cyclic voltammetry as a function of pH of supporting electrolyte solution. The optimized PAD waveform parameters were obtained with a flow injection system. The optimized pulsed conditions of doxycycline were 1150 mV (versus Ag/AgCl reference electrode) detection potential (Edet) for 220 ms (150 ms delay time and 70 ms integration time), 1500 mV (versus Ag/AgCl reference electrode) oxidation potential (Eoxd) for 70 ms oxidation time (toxd) and 250 mV (versus Ag/AgCl reference electrode) reduction potentail (Ered) for 400 ms reactivation time (tred). The optimized pulsed conditions of chlortetracycline were 1050 mV (versus Ag/AgCl reference electrode) detection potential (Edet) for 300 ms (200 ms delay time and 100 ms integration time), 1300 mV (versus Ag/AgCl reference electrode) oxidation potential (Eoxd) for 70 ms oxidation time (toxd) and 250 mV (versus Ag/AgCl reference electrode) reduction potentail (Ered) for 400 ms reactivation time (tred). The optimized PAD waveform was applied to the determination of doxycycline hydrochloride and chlortetracycline hydrochloride standard solution and in pharmaceutical formulations. The linear dynamic ranges of doxycycline hydrochloride and chlortetracycline hydrochloride were 1 µM-0.1 mM. The sensitivity of this method was found to be 23 µA/mM for doxycycline hydrochloride and 33.76 µA/mM for chlortetracycline hydrochloride. The detection limit for both compounds is 1 µM. The doxycycline hydrochloride and chlortetracycline hydrochloride content in commercially available tablet dosage forms by the proposed method was comparable to those specified by the manufacturer.

"Flow Injection In-valve-mini-column Pretreatment Combined With Ion Chromatography For Cadmium, Lead And Zinc Determination"
Talanta 2004 Volume 64, Issue 5 Pages 1241-1246
Sumalee Tanikkul, Jaroon Jakmunee, Somchai Lapanantnoppakhun, Mongkon Rayanakorn, Ponlayuth Sooksamiti, Robert E. Synovec, Gary D. Christian and Kate Grudpan

Abstract: A flow injection (FI) in-valve-mini-column packed with Chelex-100 resin is proposed for on-line sample pretreatment for some metal ions, namely, Cd(II), Pb(II) and Zn(II), prior to simultaneous determination using ion chromatography (IC). A solution containing a mixture of the cations was first passed through the in-valve-mini-column, followed by on-line elution. The eluate was then flowed further to an injection valve and was injected into an ion chromatograph. Conditions of the system were optimized. A single standard calibration was possible. The recoveries of cations were found to be in the range of 95-105%. The developed method was applied to the accurate analysis of zinc ore samples.

"Cost-effective Flow Injection Spectrophotometric Assay Of Iron Content In Pharmaceutical Preparations Using Salicylate Reagent"
Talanta 2004 Volume 64, Issue 5 Pages 1237-1240
Y. Udnan, J. Jakmunee, S. Jayasavati, G. D. Christian, R. E. Synovec and K. Grudpan

Abstract: A new flow injection procedure for an assay of Fe(III) by using salicylate obtained from antipyretic powder, which is a cheap and easily available reagent, is proposed. A red complex was continuously monitored by a laboratory-made green LED colorimeter. A linear calibration was obtained in the range of 1-20 mg Fe L-1 with a detection limit of 0.5 mg Fe L-1 and RSDs of 1.4-5.4% (n=3, for 1-20 mg Fe l-1). The new procedure was applied to assay iron contents in pharmaceutical preparations. The results were in good agreement with those of the USP standard method.

"Flow-injection Spectrophotometric Determination Of Salbutamol With 4-aminoantipyrine"
Talanta 2004 Volume 64, Issue 5 Pages 1233-1236
Isabel Dol and Mois&eacute;s Knochen

Abstract: A flow-injection method is proposed for the determination of salbutamol. The method involves the condensation of salbutamol with 4-aminoantipyrine in the presence of hexacyanoferrate (III) in alkaline medium, producing a colored quinoneimide that was detected absorptiometrically at 500 nm. The values of four variables (two reactor lengths and two reagent concentrations) were optimized by means of the sequential simplex method and their influence studied in univariant way. The method was validated and compared with the HPLC method established in the United States Pharmacopeia (USP). Linearity was demonstrated in the range 0-74.1 mg/L of salbutamol sulfate (r2 = 0.9999). Commercial samples of pharmaceuticals containing salbutamol sulfate (tablets and oral solutions) were analyzed and the results obtained with the proposed method agreed with the USP method in less than 1.6%, with precision similar to the HPLC method (1%-2% RSD). The sampling frequency was 75 samples/hour.

"Flow-injection Determination Of Phenylephrine Hydrochloride In Pharmaceutical Dosage Forms With On-line Solid-phase Extraction And Spectrophotometric Detection"
Talanta 2004 Volume 64, Issue 5 Pages 1226-1232
Mois&eacute;s Knochen and Javier Giglio

Abstract: A flow injection method is proposed for the determination of phenylephrine hydrochloride in pharmaceutical dosage forms. The method involves the use of on-line solid-phase extraction by means of a microcolumn containing Dowex 50W X8 ion-exchange resin for the separation of the analyte prior to color development and spectrophotometric detection in the visible region.The influence of pre-concentration flow, pre-concentration pH and elution volume was studied.The method exhibits appropriate linearity (r2 = 0.9999) which was proved statistically by means of the 'F'-test. When applied to commercial samples containing several active ingredients and excipients, a significant reduction of interferences was found. Accuracy, evaluated by means of the spike recovery method was in the range 99.7-100.8%, with precision (RSD, %) better than 1%.In order to achieve the automation the system was controlled from a notebook computer by means of a program written in QuickBASIC language. Under these conditions, a sampling frequency of 40 samples per hour could be attained.

"A Multicommuted Flow System For The Determination Of Copper, Chromium, Iron And Lead In Lubricating Oils With Detection By Flame AAS"
Talanta 2004 Volume 64, Issue 5 Pages 1220-1225
B. F. Reis, M. Knochen, G. Pignalosa, N. Cabrera and J. Giglio

Abstract: In this work, a flow analysis procedure for the determination of copper, chromium, iron and lead in lubricating oils using flame AAS as detection technique is described. The flow manifold was designed to implement the multicommutation approach and it comprised three 3-way solenoid valves controlled by a personal computer. The flow system presented allowed to process the oil samples to determine wear metals without any prior preparation. Aiming to assess accuracy the results were compared with those obtained by manual procedure using flame AAS. Applying the joint-confidence ellipse test, no significant difference at the 95% confidence level was observed. Other profitable features such as a sample throughput of 50 determinations per hour; relative standard deviations (n = 5) below 2% for Cu, and below 8% for Cr, Fe and Pb; and linear responses in the range 0-40 ppm (w/w) (Cu, Fe) and 0-15 ppm (w/w) (Cr, Pb) were also achieved.

"Sequential Injection Spectrophotometric Determination Of Trace Amounts Of Iodide By Its Catalytic Effect On The 4,4'-methylenebis(N,N-dimethylaniline)-chloramine-T Reaction"
Talanta 2004 Volume 64, Issue 5 Pages 1213-1219
Zeriet O. Tesfaldet, Jacobus F. van Staden and Raluca I. Stefan

Abstract: A simple and sensitive sequential injection spectrophotometric procedure is proposed for the determination of trace amounts of iodide in pharmaceutical preparations. The method is based on the catalytic effect of iodide on the (tetra base) 4,4'-methylenebis(N,N-dimethylaniline)-chloramine-T reaction in acidic solution. The method involves a sequential aspiration of 255 µl sample/standard followed by 170 µl tetra base and then 128 µl chloramine-T solutions into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil towards a detector. The resulting colored compound is measured at 600 nm using an UV/Vis-spectrophotometer. All the parameters that affect the reaction were evaluated and the calibration curve is linear over a range of 0.1-6.0 µg L-1 of iodide concentration with detection limit of 0.05 µg l-1. A sample throughput of 80 samples per hour and relative standard deviation of less than 2.0% was achieved. The method is successfully applied for the determination of iodide in three different samples (tablets).

"Determination Of Lead(II), Copper(II), Zinc(II), Cobalt(II), Cadmium(II), Iron(III), Mercury(II) Using Sequential Injection Extractions"
Talanta 2004 Volume 64, Issue 5 Pages 1203-1212
J.F. van Staden and R.E. Taljaard

Abstract: Sequential injection analysis is still dominated by single component analysis. In this proposed robust, economical simple instrumental system seven different metal ions are determined simultaneously using thin-film sequential injection extraction (SIE) with multivariate calibration and multiwavelength detection. Dithizone, in ethanol, is used as extractant and the metal dithizonates' spectra are generated by a diode array spectrophotometer between 300 and 700 nm. The SI thin-film extraction using water miscible with ethanol works due to the hydrophobic interaction of ethanol with the Teflon wall to create a thin film. A sample frequency of 27 samples per hour was obtained with a sample carry-over of less than 1%. The results of the proposed sequential injection extraction system compare favourably with the results obtained by using standard atomic absorption spectrometry (AAS) methods on conventional extraction samples.

"Spectrophotometric Determination Of Bromate By Sequential Injection Analysis"
Talanta 2004 Volume 64, Issue 5 Pages 1196-1202
J. F. van Staden, L. V. Mulaudzi and R. I. Stefan

Abstract: A simple and rapid on-line spectrophotometric method for the determination of bromate is proposed. The method is based on the reaction of bromate and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-bromo-PADAP) with SCN-, a red complex is formed and monitored at 550 nm. The linear range found is between 0.18 and 3.00 mg L-1 with a detection limit of 0.15 mg l-1. The sampling rate was calculated to be 45 samples per hour. The proposed method has a precision of less than 0.8%.

"Sequential Injection Spectrophotometric Determination Of Iron As Fe(II) In Multi-vitamin Preparations Using 1,10-phenanthroline As Complexing Agent"
Talanta 2004 Volume 64, Issue 5 Pages 1189-1195
Zeriet O. Tesfaldet, Jacobus F. van Staden and Raluca I. Stefan

Abstract: A sequential injection analysis (SIA) system is proposed for the determination of iron (II). Fe(II) was determined by SIA based on the reaction between 1,10-phenanthroline and iron (II), yielding an orange-red color complex with absorption maximum at 512 nm. The method involved aspiration of 187 µl sample/standard zone followed by a zone of a reagent solution containing 140 µl of 7.8 x 10^-4 mol L-1 1,10-phenanthroline into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil to a detector. The optimum condition was evaluated and the calibration curve is linear over a range of 0.25 to 5.0 mg L-1 of Fe(II) with detection limit of 18 µg l-1. A sample throughput of 40 h-1 was established. This technique is found to be simple, accurate, reproducible and sensitive. The proposed method was successfully applied for the determination of total iron as Fe(II) in pharmaceutical products (multi-vitamin tablets) and is especially useful for the determination of iron (II) in tablets with lower iron (II) contents. The results were found to be in good agreement with the results obtained by manual UV/Vis spectrophotometry and flame atomic absorption spectrometry (FAAS) and with claimed values by the manufacturers.

"A Flow Injection Method For The Analysis Of Tetracycline Antibiotics In Pharmaceutical Formulations Using Electrochemical Detection At Anodized Boron-doped Diamond Thin Film Electrode"
Talanta 2004 Volume 64, Issue 5 Pages 1183-1188
N. Wangfuengkanagul, W. Siangproh and O. Chailapakul

Abstract: A method using flow injection (FI) with amperometric detection at anodized boron-doped diamond (BDD) thin films has been developed and applied for the determination of tetracycline antibiotics (tetracycline, chlortetracycline, oxytetracycline and doxycycline). The electrochemical oxidation of the tetracycline antibiotics was studied at various carbon electrodes including glassy carbon (GC), as-deposited BDD and anodized BDD electrodes using cyclic voltammetry. The anodized BDD electrode exhibited well-defined irreversible cyclic voltammograms for the oxidation of tetracycline antibiotics with the highest current signals compared to the as-deposited BDD and glassy carbon electrodes. Low detection limit of 10 nM (signal-to-noise RATIO = 3) was achieved for each drug when using flow injection analysis with amperometric detection at anodized BDD electrodes. Linear calibrations were obtained from 0.1 to 50 mM for tetracycline and 0.5-50 mM for chlortetracycline, oxytetracycline and doxycycline. The proposed method has been successfully applied to determine the tetracycline antibiotics in some drug formulations. The results obtained in percent found (99.50-103.01%) were comparable to dose labeled.

"A Rapid And Precise Assay For Peroxide As 'active Oxygen' In Products, By Flow Injection Analysis In A High Pressure System With Spectrophotometric Detection"
Talanta 2004 Volume 64, Issue 5 Pages 1175-1182
M. S. Bloomfield

Abstract: A simple, rapid and automated assay for 'active oxygen' originating from hydrogen peroxide, or other organic peroxides, in products is presented employing flow injection (FI) analysis. The product is dispersed and peroxide dissolved in a solvent of 5% (v/v) acetic acid, which constitutes the carrier stream. Ammonium molybdate can be added to this carrier stream to increase sensitivity as required. The sample solution is injected into the acid carrier stream, which is then merged with iodide ion in situ in a two-stream manifold. The 'active oxygen' in the product oxidises acidified iodide to iodine, which is detected spectrophotometrically at 350 nm. The closed conditions prevent interference from atmospheric oxygen and the short reaction time minimises the potential for interference from side reactions. Standard HPLC equipment is used throughout, employing a back-pressure to improve precision (high pressure flow injection). Conditions have been investigated using screening multivariate experimental design (two-level quarter fractional factorial design incorporating centre points) to identify and optimise the critical variables. The method has been fully validated (with sample solution RSDs typically -1 as 'active oxygen' for acid or acid/molybdate carriers respectively) and is quicker and simpler than the currently employed manual titration approach. It should be applicable to a range of 'active oxygen' products.

"Determination Of Acid Dissociation Constants Based On Continuous Titration By Feedback-based Flow Ratiometry"
Talanta 2004 Volume 64, Issue 5 Pages 1169-1174
Hideji Tanaka,,, Takahiro Tachibana, Risa Oda and Purnendu K. Dasgupta

Abstract: We propose a method for the determination of acid dissociation constants based on the rapid detection of the equivalence point (EP) by feedback-based flow ratiometry and the subsequent estimation of the half equivalence point (EP1/2). The titrant (e.g., NaOH) flow rate FB was varied in response to a control voltage Vc from a controller, while the titrand (e.g., CH3COOH) flow rate FA was held constant. The pH of the mixed solution was monitored downstream from the confluence point of the solutions following a knotted tubular mixer. Initially, Vc was increased linearly. At the instance the detector sensed EP, the ramp direction of Vc changed downward. The pH increased further because of the lag time between the mixing of solutions and the sensing of pH. Following the pH maximum, the pH decreased. The EP was sensed again in this downward scan. The Vc that gives EP1/2 was computed from the Vc just at the time of the EP detection. The Vc was held constant at this level for 18 s, and the plateau pH value thus obtained was taken to be the pKa of the analyte subject to activity corrections. Studies on the dependence of the pKa on the ionic strength or dielectric constant of the solution were conducted in an automated fashion by delivering NaCl solution or acetonitrile through an additional channel. Satisfactory results were obtained with good throughput (53 s per determination) and precision (RSD[ap]0.3%) for various acids.

"Chemiluminescence Sequential Injection Immunoassay For Vitellogenin Using Magnetic Microbeads"
Talanta 2004 Volume 64, Issue 5 Pages 1160-1168
Nobuaki Soh, Hideshi Nishiyama, Yasukazu Asano, Toshihiko Imato, Takashi Masadome and Youichi Kurokawa

Abstract: A rapid and sensitive immunoassay for the determination of carp vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a samarium-cobalt magnet. An anti-Vg monoclonal antibody, immobilized on magnetic beads, was used as a solid support for the immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by a samarium-cobalt magnet and the flow of the carrier solution. The immunoassay was based on a sandwich immunoreaction of anti-Vg monoclonal antibody (primary antibody) on the magnetic beads, Vg, and the anti-Vg antibody labeled with horseradish peroxidase (HRP) (secondary antibody), and was based on a subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The magnetic beads to which the primary antibody was immobilized were prepared by coupling the primary antibody with the magnetic beads after an agarose-layer on the surface of the magnetic beads was epoxidized. The primary antibody-immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the samarium-cobalt magnet, a Vg sample solution, an HRP-labeled secondary antibody solution and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photomultiplier located at the upper side of the flow cell. The optimal incubation times both for the first and second immunoreactions were determined to be 20 min. A concave calibration curve was obtained between Vg concentration and chemiluminescence intensity when various concentrations of standard Vg samples (2-100 ng mL-1) were applied to the SIA system under optimal conditions. In spite of a narrow working range, the lower detection limit of the immunoassay was about 2 ng mL-1.

"Flow Injection Spectrophotometry Coupled With A Crushed Barium Sulfate Reactor Column For The Determination Of Sulfate Ion In Water Samples"
Talanta 2004 Volume 64, Issue 5 Pages 1147-1150
Rodjana Burakham, Keiro Higuchi, Mitsuko Oshima, Kate Grudpan and Shoji Motomizu

Abstract: A new type of a reactor column, a crushed BaSO4 reactor column used for the flow injection spectrophotometric determination of sulfate ion using the exchange reaction of sulfate ion and barium-dimethylsulfonazo III is proposed. The column is very simple and economical. It can be continuously used for 8 h before washing with water for repeated usage of at least 1 month. The procedure is sensitive. Application to various water samples was demonstrated.

"Infrared Detection In Flow Analysis -- Developments And Trends (review)"
Talanta 2004 Volume 64, Issue 5 Pages 1127-1146
Maximo Gallignani and Maria del Rosario Brunetto

Abstract: Flow analysis offers an inexpensive and versatile means for the automation of analytical procedures and hence it has been incorporated in many different techniques. However, the use of infrared detection in flow analysis systems is not common. Whereas Fourier transform infrared (FTIR) spectroscopic detection has been routinely used in gas chromatography (GC), its use for liquid chromatography, and now for flow analysis, flow injection analysis, or sequential injection analysis, is not frequent. The most prominent reasons are probably: (i) the strong absorption of most of the common solvents, specially water, (ii) the relative poor sensibility compared to UV-vis, fluorescence, etc. (iii) FTIR is normally not even considered a valuable detection technique, (iv) problems arising from obtaining adequate information from transient IR signals from the injected samples, and (v) only a few analytical chemist uses routinely the FTIR technique. This practice neglects that IR spectroscopy offers some unique features that now, using modern FTIR instrumentation, can be exploited in an advantageous manner. It is important to realize that each sample (analyte/matrix) represents a special and unique analytical problem; which defines the mode of operation and implementation of the IR technique. Flow analysis-IR techniques - as well as all techniques - has a number of shortcomings to solve these problems. In this article, most of these strategies such as the use of: baseline correction, derivative spectroscopy, stopped flow systems, reverse flow systems, multiparametric calibrations, etc., will be discussed. Additionally, recent developments in on-line gas phase generation-FTIR and hydride generation-FTIR spectrometry, as well as the principles of the HPLC-FTIR and capillary electrophoresis-FTIR hyphenation are also discussed. This review aims to provide an account of the state of the art, of these relatively new techniques. Its beginning, developments, applications and new trends, basically in the MID-IR, and by using transmission cells.

"A Multisyringe Flow Injection Method For The Automated Determination Of Sulfide In Waters Using A Miniaturised Optical Fiber Spectrophotometer"
Talanta 2004 Volume 64, Issue 5 Pages 1119-1126
Laura Ferrer, Graciela de Armas, Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: In this paper, a fully software-controlled multisyringe flow injection (MSFIA) spectrophotometric system is proposed for the determination of sulfide in environmental and waste waters. The implementation of ancillary solenoid valves into the flow network allows a multitude of injection modalities to be explored, the selected modality being directly dependent on the aim of the assays. The multicommuted sandwich-type approach is introduced in this work as an efficient means to warrant high sensitivity for the particular assay with excellent repeatabilities and a considerable reagent saving. Moreover, a high injection frequency may be easily attained by carrying out a multiple injection modality during a single forward displacement of the piston driver bar. The interfacing of the robust and versatile multisyringe piston pump with an optical fiber plug-in spectrophotometer furnished with a light emitting diode enables the miniaturization of the flow analyzer, which is thus readily adaptable to in-situ and real-time monitoring schemes. The flow method is based on the coupling Fischer's reaction of sulfide with N,N-dimethyl-p-phenylenediamine in the presence of Fe(III) as oxidizing reagent in a 0.7 M HCl medium. Careful selection of the physical and chemical variables enabled coefficients of variations better than 1.5% (n = 10) at the 1 mg L-1 level for both injection modalities. Dynamic working ranges of 0.2-2.0 and 0.5-5 mg L-1 sulfide for sandwich and multiple injection techniques, and detection limits of 0.09 and 0.15 mg l-1, respectively, were obtained. Furthermore, the sandwich modality featured an average slope of 0.43±0.02 l mg-1 calculated from 10 day-to-day calibration plots. This result reveals better sensitivity than other flowing stream methods described in the literature. The multiple injection technique allowed an improvement of the injection throughput up to 80 h-1, although a decrease of sensitivity was concomitantly observed (average slope of 0.17±0.01 l mg-1).The multisyringe flow method was successfully applied to the determination of sulfide in different spiked water matrices (namely, mineral, tap, freshwater, seawater and wastewater) with recoveries ranging from 96 to 104%. Good agreement was also found in water samples between the MSFIA results and those of the batch APHA-standard method.
Sulfide Mineral Ground Sea Water Waste Spectrophotometry Automation Computer Optimization Method comparison Interferences

"Flow Systems Exploiting In-line Prior Assays"
Talanta 2004 Volume 64, Issue 5 Pages 1114-1118
Viviane Grassi, Ana Cristi B. Dias and Elias A. G. Zagatto

Abstract: An expert sequential injection system involving a prior assay is proposed for spectrophotometric determination of phosphate and eventually zinc in soil extracts. The result of phosphate determination is the basis for a concentration-oriented decision regarding to the need or not for zinc determination. Zinc was only determined if a threshold value (peak height corresponding to 5.0 mg L-1 P) was surpassed. The methods involved formation of molybdenum blue and the Rhodamine 6G/ammonium thiocyanate/Zn2+ ternary complex. Variations in the threshold value were < 2% during 4 h operating periods, false responses were not verified, and the analytical time was reduced in about 30%. Precise results (RSD <3% P and < 1% Zn) in agreement with spectrophotometry and flame atomic absorption spectrometry were obtained. The innovation permits faster information processing, as well as a reduction in the number of measurements, number of analytical steps, laboratorial time, and consumption of sample and reagents, thus waste generation.

"Chemical Speciation By Sequential Injection Analysis: An Overview"
Talanta 2004 Volume 64, Issue 5 Pages 1109-1113
J. F. van Staden and R. I. Stefan

Abstract: The simplicity of the sequential injection (SIA) manifold and its low need for maintenance makes it an ideal tool in speciation. As miniaturization and reduction of reagent consumption are also ultimate goals in chemical sensing, it is useful to review the use of combined injection and programmed flow as a central issue in designing SIA systems with chemical sensors and structurally simplified chemical analyzer.s. This overview gives an insight into the current state, analytical scope and performance characteristics of sequential injection systems as analytical tools for speciation. The suitability of SIA for speciation analysis is illustrated by the methods used in the conduits of sequential injection systems for the chemical conversion of different chemical forms into detectable chemical species. Configurations of the basic sequential injection speciation analysis systems were designed around a multi-syringe-time-based-injection system with one detector, direct and indirect speciation of different forms using a single detector including diode array detection and direct speciation of different forms using multiple detection.Examples showing the use of SIA for the simultaneous determination or speciation of metal ions, inorganic anions and organic compounds are given with some recent results from our research groups.

"Analytical Applications Of Organized Assemblies For On-line Spectrometric Determinations: Present And Future"
Talanta 2004 Volume 64, Issue 5 Pages 1099-1108
Jos&eacute; L. Burguera and Marcela Burguera

Abstract: An amphiphile (surfactant) spread on water can lead to the formation of different aggregates: vesicles, miscelles, emulsions or microemulsions; depending on its concentration; its molecular structure and/or the experimental conditions. Such aggregates, (a) may concentrate products, reactants or analytes and so improve the analytical sensitivity and (b) may solubilize such substances and so favorably change the analytical selectivity. Bilayer membrane vesicles for instance, apart from their wide applications in cosmetic and pharmaceutical industries, have a great analytical potential due to their ability to (i) reversibly sequester metal ions avoiding matrix interference and (ii) improve cold vapor (Hg and Cd) and hydride (As, Se, Pb) chemical generation. Micellar solutions have also found wide applications in different areas of analytical chemistry, showing their capacity to concentrate and separate a significant variety of analytes. Among the numerous micelle-based separation techniques, cloud point extraction offers an excellent enrichment factor for metal ions, allowing their quantification atµg/litre levels. Also agitating a mixture of water, oil and one or more surfactants under controlled experimental conditions, a cloudy mixture (emulsion) or a transparent solution (microemulsion) can be formed. Adequate formulation is necessary in order to obtain a stable organized media. To fulfill this requirement, a major effort is necessary in order to shorten the gap between the current knowledge on this topic and the promising field of applications that await development. Recent publications show that self-assembly structures from highly viscous samples can be accomplished on-line with the advantages of drastically reducing the time of analysis and assuring the absolute control over the stability of the aggregate. Flow systems allow effective mixing of samples with added surfactant and provide continuous pumping of the resulting mixture to sensitive detectors for the on-line determination of different analytes in complex samples.

"Multi-pumping Flow Systems: An Automation Tool"
Talanta 2004 Volume 64, Issue 5 Pages 1091-1098
Jos&eacute; L. F. C. Lima, Jo&atilde;o L. M. Santos, Ana C. B. Dias, Marta F. T. Ribeiro and Elias A. G. Zagatto

Abstract: Multi-pumping flow systems (MPFS) are one of the most recent developments in terms of the design, conception and implementation of continuous flow methodologies, for sample and reagent handling and for the automation of analytical procedures. Based on the utilisation of multiple solenoid micro-pumps they enable the configuring of fully automated and easily controlled and operated analytical systems since all the fundamental operations involved in carrying out a sample analysis, including sample insertion, reagent addition and signal measurement could be carried out by the same manifold component, reducing the number of system parts and minimising its control or the occurrence of mal-functions. On the other hand, micro-pumps actuation produce a pulsed flow characterized by a chaotic movement of the solutions, which contributes to a fast sample/reagent homogenisation with low axial dispersion yielding improved analytical signals. The combination of such advantageous features resulted in simple, compact, versatile, fast, low-cost analytical procedures, exhibiting low reagent and low sample consumption, reducing the production of undesirable wastes and minimising operator intervention.

"Some Recent Developments On Cost-effective Flow-based Analysis"
Talanta 2004 Volume 64, Issue 5 Pages 1084-1090
Kate Grudpan

Abstract: This paper reviews some recent developments on cost-effective flow-based analysis. They include the newly developed Lab-at-Valve (LAV), concepts in using the stopped-flow injection approach, on-line sample pretreatment systems, including bead injection-flow injection and flow injection-ion-chromatography, systems for size-based speciation, and cost-effective reagents. Applications and advantages of such techniques are discussed.

"The Impact Of Flow Injection On Modern Chemical Analysis: Has It Fulfilled Our Expectations? And Where Are We Going?"
Talanta 2004 Volume 64, Issue 5 Pages 1076-1083
Elo Harald Hansen

Abstract: Presenting a condensation of the opening lecture of the 12th ICFIA conference, this communication presents a view of the impact that flow injection analysis (FIA) has had on modern analytical chemistry, evaluated both within the academic community and outside it, i.e. in 'industry'. The ensuing developments of FIA, encompassing sequential injection analysis (SIA) and bead injection lab-on-valve (BI-LOV), are described and their individual features discussed. Finally, some recent results of the activities from the author's own research group are briefly mentioned.

"An Analytical Chemist Of Stature And Pioneer In Flow Analysis: Gary Dale Christian"
Talanta 2004 Volume 64, Issue 5 Pages 1071-1075
J.F. van Staden

Abstract: The 12th International Conference on Flow Injection Analysis including related techniques (ICFIA XII/JAFIA) was dedicated to Gary Dale Christian for an enormous contribution as a distinguished international scientist and his devotion to ICFIA through all the years. It was therefore not a surprise that he received the JAFIA Scientific Honor Award medal and certificate at this Conference for his pioneering work in FIA, an award that JAFIA and the Division of the Japan Society for Analytical Chemistry (JSAC) grant only every 5 years and an award that was particularly special as a 20th anniversary recognition. As guest editor of this special edition of Talanta on 12th ICFIA, it is therefore my privilege to follow with you the pioneering career of this leading analytical chemist and special personality in the family of flow-based systems who celebrated his 66th birthday on 25th November 2003, just before the conference. As person who worked in flow-based systems from the late 1960s and early 1970s at Sasol, I know the work of Gary Christian from the early 1970s, but I met him for the first time when as Chairman of the First National Symposium on Analytical Science, 19-23 March 1990, in South Africa, where I invited him with Sasol as sponsor to give a plenary lecture on Flow Injection Analysis in Process Analysis. With Gary's involvement in the Center for Process Analytical Chemistry (CPAC) at the University of Washington at that stage, he brought a vast expertise with him and his presentation on approaches and insights in process analysis inspired a number of changes in my personal attitude in research. With Graham Marshall at that stage at the University of Washington under Jarda Ruzicka, the informal discussions with Gary were extremely valuable; so when Graham returned from the USA the platform was set for my research in developing robust, cost-effective instrumentation for process analytical systems in collaboration with the Council for Mineral Technology (MINTEK). The visit by Gary Christian to my country, therefore, definitely generated a new trend and success on my own research. It is therefore with interest that I read recently in the May 2004 edition of Chemical and Engineering News [1] of the celebration of 20 years of service by the Center for Process Analytical Chemistry (CPAC) to industry where CPAC thrived by evolving to meet the needs of industry. Gary Dale Christian is very well known for his numerous contributions on various aspects of analytical chemistry ranging from electro-analytical chemistry, atomic spectroscopy, process analysis, flow injection analysis and electro-injection analysis, and has also been very active in the field of education. His detailed CV of almost 100 pages is very impressive and distinctive of this thorough analytical chemist.

"Editorial To ICFIA XII Conference S.I"
Talanta 2004 Volume 64, Issue 5 Pages 1067-1070
J.F. van Staden and J.L. Burguera

Abstract: No abstract

"Development Of A Sequential Injection System For Trace Mercury Determination By Cold Vapour Atomic Absorption Spectrometry Utilizing An Integrated Gas-liquid Separator/reactor"
Talanta 2004 Volume 64, Issue 4 Pages 1053-1057
Aristidis N. Anthemidis, George A. Zachariadis and John A. Stratis

Abstract: A simple and robust time-based on-line sequential injection system for trace mercury determination via cold vapor atomic absorption spectrometry (CVAAS), employing a new integrated gas-liquid separator (GLS), which in parallel operates as reactor, was developed. Sample and reductant are sequentially loaded into the GLS while an argon flow delivers the released mercury vapor through the atomic absorption cell. The proposed method is characterized by the ability of successfully managing variable sample volume up to 30 mL in order to achieve high sensitivity. For 20 mL sample volume, the sampling frequency is 25 h-1. The calibration curve is linear over the concentration range 0.05-5.0 µg L-1 of Hg(II), the detection limit is cL = 0.02 µg l-1, and the relative standard deviation is sr = 2.6% at 1.0 µg L-1 Hg(II) level. The performance of the proposed method was evaluated by analyzing certified reference material and applied to the analysis of natural waters and biological samples.

"FI Automatic Method For The Determination Of Copper(II) Based On Coproporphyrin I-Cu(II)/TCPO/H2O2 Chemiluminescence Reaction For The Screening Of Waters"
Talanta 2004 Volume 64, Issue 4 Pages 1030-1035
S. Meseguer-Lloret, P. Camp&iacute;ns-Falc&oacute;, S. C&aacute;rdenas, M. Gallego and M. Valc&aacute;rcel

Abstract: In this paper, an automatic method for the screening of water samples containing Cu(II) was proposed, based on peryoxalate chemiluminescence reaction using coproporphyrin I as fluorophor compound to provide selectivity and a simple flow injection (FI) chemiluminescence detector (CLD). FI system conditions were chosen in order to distinguish samples over or under legislation limit established (50 µg L-1) with high reliability. The detection limit found was 9 µg L-1 and the linear dynamic range was 15-125 µg L-1 of Cu(II). Repeatability and reproducibility studies gave good precision and accuracy with recovery near 100%. Under these conditions, the method resulted selective and only Fe(II), Fe(III) and Pb(II) could interfere, but at a concentration level higher than their normal concentration in waters. The proposed method was found to be highly reliable for screening purposes and it was successfully applied to the screening of a variety of real water samples.

"Integration Of A Flow-type Chemiluminescence Detector On A Glass Electrophoresis Chip"
Talanta 2004 Volume 64, Issue 4 Pages 1024-1029
Rongguo Su, Jin-Ming Lin, Katsumi Uchiyama and Masaaki Yamada

Abstract: A glass electrophoresis microchip integrated a flow-type chemiluminescence (CL) detection cell has been developed and evaluated. The chip pattern is a double-T-type electrophoretic sample injection and separation combining with a Y-type chemiluminescent detector. The double-T geometry allows for high-efficiency sample injection and geometric definition of sample plug size. The branch of Y was used as CL reagent channel, and the CL reagent was delivered by a lab-made micropump. Bis[(2,4,6-trichlorophenyl)]oxalate-H2O2 CL system was employed to detect dansyl amino acids. On this microchip, dansyl-phenylalanine and -sarcosine were successfully separated by electrophoresis and detected within 250 s. The detection limits (S/N=3) of dansyl-phenylalanine and -sarcosine could reach to 2.8 and 3.2 µM, respectively, due to the vigorous dilution of sample with CL reagent and timely removal of the waste solution from reaction area.

"Continuous-flow/stopped-flow System For Determination Of Ascorbic Acid Using An Enzymatic Rotating Bioreactor"
Talanta 2004 Volume 64, Issue 4 Pages 1009-1017
Germ&aacute;n A. Messina, Angel A. J. Torriero, Irma E. De Vito and Julio Raba

Abstract: The high sensitivity that can be attained using an enzymatic system and mediated by hydroquinone, has been verified by on-line interfacing of a rotating bioreactor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in presence of hydrogen peroxide catalyses the oxidation of hydroquinone to p-benzoquinone, whose electrochemical reduction back to hydroquinone is detected on glassy carbon electrode (GCE) surface at -0.15 V. Thus, when -ascorbic acid is added to the solution, this acid is reduced chemically (p-benzoquinone to hydroquinone) and acts as mediator of HRP, decreasing the peak current obtained proportionally to the increase of its concentration. The recovery of -ascorbic acid from four samples ranged from 99.09 to 101.10%. This method could be used to determine -ascorbic acid concentration in the range 12 nM-3.5 µM (r = 0.998). The determination of -ascorbic acid was possible with a limit of detection of 6 nM in the processing of as many as 25 samples h-1. The method was successfully applied for the analysis of -ascorbic acid in pharmaceutical formulations.

"Exploiting The Bead Injection Concept For Sequential Determination Of Copper And Mercury Ions In River-water Samples"
Talanta 2004 Volume 64, Issue 4 Pages 993-999
Eliane C. Vidotti, Vitor C. Almeida and Cl&aacute;udio C. Oliveira

Abstract: A procedure involving bead-injection concept and sequential determination of copper and mercury ions in river-water samples is proposed. The method is based on the solid-phase extraction of both metal ions on the same beads surface (Chelex 100 resin) and in their subsequent reaction with the colorimetric reagents (APDC and Dithizone for copper and mercury ions, respectively). For this task, a resin mini-column is established in the optical path by the selection, introduction and trapping of a defined volume of the Chelex-100 resin beads suspension in the flow system. The passage of the sample solution through the resin mini-column promotes the sorption of Cu(II) ions and, making the APDC colorimetric reagent flows through the beads, the formation of the colored complex on the solid phase surface occurs. The absorbance of the formed APDC-Cu complex is then monitored at 436 nm and the spent beads are discarded. Packing another resin mini-column in the flow cell and repeating the concentration step it is possible to carried out the mercury determination by using Dithizone as reagent. The absorbance of the Dithizone-Hg complex is monitored at 500 nm. After each measurement, the spent beads are wasted and a new portion of fresh one is trapped in the system, letting it ready for the next measurement. The bead injection system is versatile and can be used to concentrate different sample volumes, which permits the determination of a wide range of copper and mercury ions concentrations. When the sample-selected volumes are 100 and 1000 µl the analytical ranges were 5.0 up to 500.0 µg L-1 and 2.5 up to 30.0 µg L-1 for Cu(II) and Hg(II) ions, respectively. Under these conditions, the detection limit was estimated as 0.63 and 0.25 µg L-1 for copper and mercury ions determination. The system consumes 2 mg of Chelex 100 resin beads, 0.20 mg of APDC or 1.25 mg of Dithizone per determination and the traditional organic solvent extraction methodology, normally used in connection with APDC and Dithizone reagents, is not used here which permits to classify the present method as green.

"Spectrophotometric Determination Of Magnesium In Pharmaceutical Preparations By Cost-effective Sequential Injection Analysis"
Talanta 2004 Volume 64, Issue 4 Pages 981-988
Zeriet O. Tesfaldet, Jacobus F. van Staden and Raluca I. Stefan

Abstract: A simple and rapid, inexpensive spectrophotometric method was proposed for magnesium assay in pharmaceutical preparations by sequential injection analysis (SIA). The method is based on the reaction between o-cresolphthalein complexone (CPC) and Mg(II) in alkaline media, yielding a pink colored complex with absorption maximum at 570 nm. Since the formation constant between Ca-CPC and Mg-CPC is similar, initially a sample/standard solution was aspirated into the holding coil followed by a mixture of masking-buffer solutions. This was done because masking of calcium should be accomplished before Mg-CPC complexation. Then the reagent was introduced into the reaction coil to produce a colored complex, which is measured spectrophotometrically at 570 nm. In this way the interference of calcium was reduced. Furthermore, all the parameters that affect the reaction were evaluated. The calibration curve is linear over a range of 0-20 mg L-1 of Mg(II) with a detection limit of 0.24 mg l-1. A sample throughput of 80 samples per hour and relative standard deviation t-test shows no significant difference at 95% confidence level.

"Rapid And Simultaneous Analysis Of Dichlorvos, Malathion, Carbaryl, And 2,4-dichlorophenoxy Acetic Acid In Citrus Fruit By Flow-injection Ion Spray Ionization Tandem Mass Spectrometry"
Talanta 2004 Volume 64, Issue 4 Pages 899-905
Hiroyuki Nakazawa, Nobuyuki Takahashi, Koichi Inoue, Yuko Ito, Tomomi Goto, Kayoko Kato, Yoshihiro Yoshimura and Hisao Oka

Abstract: A simple method for the rapid and simultaneous analysis of dichlorvos (DDVP), malathion, carbaryl, and 2,4-dichlorophenoxy acetic acid (2,4-D) in citrus fruit, which uses flow-injection ion spray ionization tandem mass spectrometry, has been developed for the first time. The method involves the combined use of stable isotopically labeled internal standards (DDVP-d6, malathion-d10, carbaryl-d7, and 2,4-D-d5) and a multiple reaction monitoring technique. The average recoveries for the pesticides at the same concentrations as their tolerance levels (DDVP: 0.1-0.2 µg g-1; malathion: 0.5-4.0 µg g-1; carbaryl: 1.0 µg g-1; 2,4-D: 1.0-2.0 µg g-1) ranged from 90 to 119% with the relative standard deviation (RSD) ranging from 1.0 to 13.1% (n = 5). Analysis time, including sample preparation and determination, was only 15 min. The present method is effective for screening DDVP, malathion, carbaryl, and 2,4-D in citrus fruit.

"Determination Of Proline In Wine Using Flow Injection Analysis With Tris(2,2'-bipyridyl)ruthenium(II) Chemiluminescence Detection"
Talanta 2004 Volume 64, Issue 4 Pages 894-898
Jason W. Costin, Neil W. Barnett and Simon W. Lewis

Abstract: Flow injection methodology is described for the determination of proline in red and white wines using tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection. Selective conditions were achieved for proline at pH 10, while other amino acids and wine components did not interfere. The precision of the method was less than 1.00% (RSD) for five replicates of a standard (4 x 10^-6 M) and the detection limit was 1 x 10^-8 M. The level of proline in white and sparkling wines using the developed methodology was equivalent to those achieved using HPLC-FMOC amino acid analysis. SPE removal of phenolic material was required for red wines to minimize Ru(bipy)33+ consumption and its associated effect on accuracy.

"Further Study On A Flow Injection On-line Multiplexed Sorption Preconcentration Coupled With Flame Atomic Absorption Spectrometry For Trace Element Determination"
Talanta 2004 Volume 64, Issue 3 Pages 758-765
Yan Li, Yan Jiang and Xiu-Ping Yan

Abstract: A further study on a newly developed flow injection (FI) on-line multiplexed sorption pre-concentration (MSP) using a knotted reactor coupled with flame atomic absorption spectrometry (FAAS) was carried out to demonstrate its applicability and limitation for trace element determination. For this purpose, Cr(VI), Cu(II), Ni(II) and Co(II) were selected as the analytes, and detailed comparison was made between the MSP-FAAS and conventional FI on-line sorption pre-concentration FAAS in respect to retention efficiency and linear ranges of absorbance versus sample loading flow rate and total pre-concentration time. Introduction of an air-flow for removal of the residual solution in the KR after each sub-injection in the MSP procedure played a decisive role in the improvement of retention efficiency. The linearity of absorbance versus sample loading flow rate or total pre-concentration time was extended to a more degree for the metal ions with less stability of their PDC (pyrrolidine dithiocarbamate) complexes than those with more stable PDC complexes. It seems that the MSP procedure behaves advantages beyond the inflection points in the diagrams of absorbance versus total pre-concentration time and sample loading flow rate obtained by conventional (a single continuous) pre-concentration procedure. With a sample loading flow rate of 6.0 mL min-1 and a total pre-concentration time of 180 s, the retention efficiencies were increased from 25, 46, 41 and 63% with a single continuous sorption pre-concentration to 44, 78, 65 and 75% with a six sub-injection pre-concentration procedure for Cr(VI), Co(II), Ni(II), and Cu(II), respectively. The detection limits were 0.40, 0.33, 0.31 and 0.26 µg L-1 for Cr(VI), Co(II), Ni(II), and Cu(II), respectively. The precision (RSD) for eleven replicate determination of 2 µg L-1 Cr(VI), Co(II) and Ni(II), and 1 µg L-1 Cu(II), was 2.1, 4.1, 2.6 and 1.7%, respectively.

"Multiwavelength Fluorescence Based Optosensor For Simultaneous Determination Of Fuberidazole, Carbaryl And Benomyl"
Talanta 2004 Volume 64, Issue 3 Pages 742-749
J. F. Garc&iacute;a Reyes, E. J. Llorent Mart&iacute;nez, P. Ortega Barrales and A. Molina D&iacute;az

Abstract: In the present work, a novel approach is proposed for the simultaneous determination of three widely used pesticides (namely, fuberidazole (FBZ), carbaryl (CBL) and benomyl (BNM)). The proposed method is based on a single continuous-flow solid surface fluorimetric multi-optosensor implemented with the use of a minicolumn placed just before the flow-through cell and filled with C18 silica gel. The three pesticides are determined from an only injection (simultaneous determination): the minicolumn strongly retains two of them while the third develops a transitory signal when passing through the sensing solid microzone. Then, two alternate eluting solutions appropriately selected perform the sequential elution of the two pesticides from the minicolumn, achieving the detection zone and developing their transitory signals. The proposed optosensor works under optimal sensitivity conditions for all the three analytes because of the use of multi-wavelength fluorescence detection mode, so recording three different signals corresponding at three pairs of optima excitation/emission wavelengths. Using a sample volume of 2100 µL, the system was calibrated in the range 0.5-15, 40-800 and 50-1000 ?g L-1 with detection limits of 0.09, 6 and 9 ?g L-1 for FBZ, CBL and BNM, respectively. The R.S.D values (n=10) were lower than 2% in all cases. The proposed methodology was applied satisfactorily to water samples. Recovery percentages ranging from 97.8 to 101.1%, 97.9 to 103% and from 97 to 105% for FBZ, CBL and BNM, respectively, were obtained. © 2004 Elsevier B.V. All rights reserved.

"Determination Of Formaldehyde In Brazilian Alcohol Fuels By Flow-injection Solid Phase Spectrophotometry"
Talanta 2004 Volume 64, Issue 3 Pages 711-715
Leonardo S. G. Teixeira, Elsimar S. Le&atilde;o, Ala&iacute;lson F. Dantas, Helo&iacute;sa L. C. Pinheiro, Antonio C. S. Costa and Jailson B. de Andrade

Abstract: In this work, a solid phase spectrophotometric method in association with flow injection analysis for formaldehyde determination has been developed with direct measurement of light-absorption in C18 material. The 3,5-diacetyl-1,4-dihydrolutidine produced from the reaction between formaldehyde and fluoral P was quantitatively retained on C18 support and the spectrophotometric detection was performed simultaneously at 412 nm. The retained complex was quickly eluted from C18 material with the eluent stream consisting of a 50% (v/v) ethanol solution. The results showed that the proposed method is simple, rapid and the analytical response is linear in the concentration range of 0.050-1.5 mg L-1. The limit of detection was estimated as 30 µg L-1 and the RSD 2.2% using a sample volume of 625 µL. The system presented an analytical throughput of 20 determinations per hour. The method was successfully applied in the determination of formaldehyde in ethanol fuel.

"Sequential Flow Injection Analysis Of Ammonium And Nitrate Using Gas Phase Molecular Absorption Spectrometry"
Talanta 2004 Volume 64, Issue 3 Pages 688-694
B. Haghighi and S. Farrokhi Kurd

Abstract: A flow injection method on the basis of gas phase molecular absorption is described for the sequential determination of ammonium and nitrate. Two hundred microliters of sample solution is injected into the flow line. For ammonium determination, the sample zone is directed to a line in which reacts with NaOH (13 M) and produces ammonia. But for nitrate determination, the sample zone is passed through the on-line copperized zinc (Zn/Cu) reduction column and produces ammonium ion and in the follows ammonia. The produced ammonia in both cases is purged into the stream of N2 carrier gas. The gaseous phase is separated from the liquid phase using a gas-liquid separator and then is swept into a flow through cell, which has been positioned in the cell compartment of an UV-Vis spectrophotometer. The absorbance of the gaseous phase is measured at 194 nm. Under selected conditions for sequential analysis of ammonium and nitrate, linear relations were found between the peak heights of absorption signals and concentrations of ammonium (10-650 µg mL-1) and nitrate (20-800 µg mL-1). The limit of detections for ammonium and nitrate analysis were 8 and 10 µg mL-1, respectively. The relative standard deviations of repeated measurements of 50 µg mL-1 of ammonium and nitrate were 2.0, 2.9%, respectively. Maximum sampling rate was about 40 samples/h. The method was applied to the determination of ammonium in pharmaceutical products and the sequential determination of ammonium and nitrate in spiked water samples.

"Trace Enrichment And Determination Of Silver By Immobilized DDTC Microcolumn And Flow Injection Atomic Absorption Spectrometry"
Talanta 2004 Volume 64, Issue 3 Pages 682-687
S. Dadfarnia, A. M. Haji Shabani and M. Gohari

Abstract: Flow injection (FI) system incorporating a microcolumn of immobilized diethyldithiocarbamate (DDTC) on surfactant-coated alumina was combined with atomic absorption spectrometry for on-line trace enrichment and determination of silver in different matrices. Silver was deposited on the microcolumn by processing a standard or solution of analyte at pH 3-4 on the column. Injection of 250 µl of ethanol then served to elute the retained species to atomic absorption spectrometry (AAS). A sample volume of 20 mL resulted in a pre-concentration factor of 125, and precision at the 20 µg L-1 was 4% (RSD). The procedure was applied to tap water, well water, rain water, sea water, radiology film, and lead concentrate samples. The accuracy was assessed through recovery experiments, independent analysis by furnace-AAS, and analysis of certified reference material.

"Amperometric Cholesterol Biosensors Based On The Electropolymerization Of Pyrrole And The Electrocatalytic Effect Of Prussian-Blue Layers Helped With Self-assembled Monolayers"
Talanta 2004 Volume 64, Issue 3 Pages 655-664
Juan-C. Vidal, Javier Espuelas, Esperanza Garcia-Ruiz and Juan-R. Castillo

Abstract: Three cholesterol biosensor configurations based on the formation of a layer of Prussian-Blue (PB) on a Pt electrode for the electrocatalytic detection of the H2O2 generated during the enzymatic reaction of cholesterol with cholesterol oxidase (ChOx) were constructed. The enzyme was entrapped within a polypyrrole (PPy) layer electropolymerized onto the PB film. The influence of the formation of self-assembled monolayers (SAMs) on the Pt surface on the adherence and stability of the PB layer and the formation of an outer layer of nafion (Nf) as a means of improving selectivity were both studied. A comparative study was made of the analytical properties of the biosensors corresponding to the three configurations named: Pt/PB/PPy-ChOx, Pt/SAM/PB/PPy-ChOx and Pt/SAM/PB/PPy-ChOx/Nf. The sensitivity (from 600 to 8500 nA mM 1 cm-2) and selectivity of the developed biosensors permitted the determination of the cholesterol content in reference and synthetic serum samples. The detection limit for the Pt/SAM/PB/PPy-ChOx/Nf biosensor was 8 µM. Formation of the SAM on the electrode surface and covering with a Nf film considerably improved the stability and lifetime of the biosensor based on the catalytic effect of the PB layer (as the PB layer was retained longer on the electrode), and the Nf layer protects the enzyme from the external flowing solutions. Lifetime is up to 25 days of use. The formation of the SAM also has an effect on the charge transfer and the formation of the PB layer.

"Effect Of Cathodic Electrolyte On The Performance Of Electrochemical Hydride Generation From Graphite Cathode"
Talanta 2004 Volume 64, Issue 3 Pages 644-649
M. Hashemi, M. H. Arbab-Zavar and A. Sarafraz-Yazdi

Abstract: The classic silver diethyldithiocarbamate (SDDC) spectrophotometric procedure for arsenic determination has been used for investigation of the effect of cathodic electrolyte on the performance of electrochemical hydride generation (HG) from graphite cathode. The results of this study show that the presence of a soft metal ion such as Cd(II), Sn(II) and/or Zn(II) in the acidic cathodic electrolyte can increase effectively the efficiency of electrochemical hydride generation and decrease the effect of interferences. The possible mechanisms of these effects have been discussed in detail. The parameters related to the electrochemical hydride generation were investigated. Also the characteristic data of the electrochemical hydride generation and common hydride generation by NaBH4 were compared. Under optimized conditions, the system is selective to As(III) and total inorganic analyzes can be performed after a pre-reduction stage prior to electrochemical hydride generation. This will allow the differential determination of inorganic arsenic species. The method is appropriate to the determination of 4-40 µg of each arsenic species.

"A Tandem-flow Assembly For The Chemiluminometric Determination Of Hydroquinone"
Talanta 2004 Volume 64, Issue 3 Pages 618-625
B. G&oacute;mez-Taylor Corominas, M. Catal&aacute; Icardo, L. Lahuerta Zamora, J. V. Garc&iacute;a Mateo and J. Mart&iacute;nez Calatayud

Abstract: A direct chemiluminescent procedure for determination of hydroquinone based on the emergent flow methodology known as multicommutation or tandem-flow is presented for first time. The manifold was based on a set of three channels and three solenoid valves; and, the determination was performed at 60°C and at flow-rate of 7.5 mL min-1. The complete cycle lasted 35 s, which resulted in a sample flow trough of 103 h-1. The chemical process was the hydroquinone oxidation with the system sulphuric acid-potassium permanganate; and the light emission was clearly enhanced by the presence of quinine sulphate and benzalkonium chloride reaching a detection limit of 30 µg l-1. The dynamic interval was over the range 0.1-15.0 mg L-1 and a large list of interferents were assayed; the chemical robustness was also tested. The method was applied to different type of samples: namely, pharmaceutical formulations, a photographic solution and irrigation and residual superficial waters.

"Creatinine Biosensor Based On Ammonium Ion Selective Electrode And Its Application In Flow-injection Analysis"
Talanta 2004 Volume 64, Issue 3 Pages 603-608
Anna Radomska, Ewa Bodenszac, Stanisaw Gb and Robert Koncki

Abstract: A new, highly sensitive, fast responding and stable potentiometric biosensor for creatinine determination is developed. The biosensor is based on an ammonium ion-selective electrode. Creatinine deiminase (EC 3.5.4.21) is chemically immobilized on the surface of the polymeric ion-sensitive membrane in the form of monomolecular layer using a simple, one-step carbodiimide covalent attachment method. The resulting enzyme electrodes are useful for measurement under flow injection analysis (FIA) conditions. The biosensors exhibit excellent operational and storage stability. The enzyme electrodes retain over 70% of initial sensitivity after ten weeks of work under FIA conditions. The storage stability at 4°C is longer than half a year without loss of sensitivity. Under optimized conditions near 30 samples per hour can be analyzed and the determination range (0.02-20.0 mmol l-1) fully covers creatinine concentrations important from clinical and biomedical point of view. The simple biosensor/FIA system has been successfully used for determination of creatinine in urine, serum and posthemodialysate samples.

"A Very Sensitive Flow System For The Direct Determination Of Copper In Natural Waters Based On Spectrophotometric Detection"
Talanta 2004 Volume 64, Issue 2 Pages 562-565
Juan J. Pinto, Carlos Moreno and Manuel Garc&iacute;a-Vargas

Abstract: A very sensitive flow injection method with spectrophotometric detection has been developed for the on-line determination of copper in natural waters. The method exhibits a limit of detection three times lower than the most sensitive direct spectrophotometric method previously described and then allows the direct and simple in situ determination of copper in most natural waters.The method was based on the measurement of the absorbance of the colored complex formed by copper with the chromogenic reagent di-2-pyridyl ketone benzoylhydrazone (dPKBH) in an alkaline medium. This complex presents stoichiometry 1:2 (Cu:dPKBH), and exhibits maximum absorbance at 370 nm. The manifold used was very simple, and consisted of two channels. The first one contained the sample while the second one contained the colorimetric reagent (3.3 x 10^-4 M dPKBH in 10% ethanol), in a 1.6 x 10^-2 M phosphate buffer solution at pH 8. The performance of the system was optimized by using both univariate and modified simplex methodologies. When modified simplex was used, the best signal was obtained for a sample injection volume of 529 µl, a reaction coil length of 1.29 m, and a reagent flow rate of 4.8 mL min-1. Under optimum conditions, the response was linear up to 3 mg L-1 copper, the equation of the straight line being y=0.314x+5.2 x 10^-4 (r2=0.998). The method allowed a sampling frequency of 40 samples per hour and exhibited a precision of 2.11% (as RSD, n=11). The limit of detection was 4.6 µg L-1 (calculated as 3sb/m, where sb is the standard deviation of the y-intercept and m represents the slope of the straight line), and was therefore more sensitive than all the direct continuous methods reported previously.The method was successfully applied to the analysis of real water samples, with an average relative error of 5.32%.

"Rapid Determination Of Total Mercury In Treated Waste Water By Cold Vapor Atomic Absorption Spectrometry In Alkaline Medium With Sodium Hypochlorite Solution"
Talanta 2004 Volume 64, Issue 2 Pages 554-557
Shigehiro Kagaya, Yoshiharu Kuroda, Yuka Serikawa and Kiyoshi Hasegawa

Abstract: Addition of a sodium hypochlorite solution (9.2% (w/v)) was effective to reduce a sulfide interference in determination of organic mercury, including methylmercury and phenylmercury, as well as a previously reported determination of inorganic mercury by cold vapor atomic absorption spectrometry (CVAAS) in an alkaline medium. Total mercury ranging from 0.17 to 33 µg L-1 in 15 mL of sample solutions containing up to 200 mg L-1 of sulfide can be determined without any serious interference by sulfide when 1 mL of the sodium hypochlorite solution was added after dilution of the sample solution to 25 mL. The proposed method was simple and rapid because no digestion processes were required for the determination of total mercury; the time required for the determination was only about 5 min. The proposed method was applicable to the analysis of treated waste water.

"Determination Of Glyphosate Mono-isopropylamine Salt In Process Samples Using Flow Injection Analysis With Tris(2,2'-bipyridyl)ruthenium(II) Chemiluminescence Detection"
Talanta 2004 Volume 64, Issue 2 Pages 534-537
Jacqui L. Adcock, Neil W. Barnett, Richard D. Gerardi, Claire E. Lenehan and Simon W. Lewis

Abstract: The mono-isopropylamine salt of glyphosate was selectively determined directly in industrial and commercial formulations using flow injection analysis with tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection without the need for separation. Glyphosate and its mono-isopropylamine salt furnished detection limits of 7 x 10^-9 and 3.5 x 10^-10 M and relative standard deviations of 0.4% at 1 x 10^-7 M and 0.8% at 5 x 10^-8 M, respectively. The methodology is robust and reliable with samples subjected only to aqueous dilution prior to analysis.

"Flow-injection Chemiluminescence Determination Of Dihydralazine Sulfate Based On Hexacyanoferrate(III) Oxidation Sensitized By Eosin Y"
Talanta 2004 Volume 64, Issue 2 Pages 478-483
Xiao-Feng Yang and Hua Li

Abstract: A novel flow-injection chemiluminescence (CL) method for the determination of dihydralazine sulfate (DHZS) is described. The method is based on the reaction between DHZS and hexacyanoferrate(III) in alkaline solution to give weak CL signal, which is dramatically enhanced by eosin Y. The CL emission allows quantitation of DHZS concentration in the range 0.02-2.8 µg mL-1 with a detection limit (3s) of 0.012 µg mL-1. The experimental conditions for the CL reaction are optimized and the possible reaction mechanism is discussed. The method has been applied to the determination of DHZS in pharmaceutical preparations and compared well with the high performance liquid chromatography (HPLC) method.

"Determination Of Lead In Dialysis Concentrates Using Flow Injection Hydride Generation Atomic Absorption Spectrometry"
Talanta 2004 Volume 64, Issue 2 Pages 423-427
Aysel Berkkan and Nusret Ertas

Abstract: Flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) was used for determination of lead in dialysis concentrates. The parameters such as acidity, concentration of oxidising and reducing agents and argon gas flow rate were investigated to reach the best peak height sensitivity. No significant background signal was observed at high salt concentrations. The detection limit, concentration giving a signal equal to three times standard deviation of the blank signal, was 0.7 ng mL-1 for a 500 µl injection volume. Precision of the measurements at the 20 ng mL-1 level was 3.7% RSD The dialysis concentrates analyzed by FI-HGAAS were found to have 10^-70 ng mL-1 of lead. The same samples were analyzed by ETAAS after removing the matrix using solid phase extraction with Chelex 100. The results were in agreement with those obtained by FI-HGAAS.

"Direct Determination Of Ge In Hot Spring Waters And Coal Fly Ash Samples By Hydride Generation-ETAAS"
Talanta 2004 Volume 64, Issue 2 Pages 302-307
Carmen Moscoso-P&eacute;rez, Jorge Moreda-Pi&ntilde;eiro, Purificaci&oacute;n L&oacute;pez-Mah&iacute;a, Soledad Muniategui-Lorenzo, Esther Fern&aacute;ndez-Fern&aacute;ndez and Dar&iacute;o Prada-Rodr&iacute;guez

Abstract: A method for Ge determination in hot spring water and acid extracts from coal fly ash samples involving hydride generation, trapping and atomisation of the hydride generated from Ir-treated graphite tubes (GTs) has been developed. Hydride was generated from hydrochloric acid medium using sodium tetrahydroborate. Several factors affecting the hydride generation, transport, trapping and atomisation efficiency were studied by using a Plackett-Burman design. Results obtained from Plackett-Burman designs suggest that trapping and atomisation temperatures are the significant factors involved on the procedure. The accuracy was studied using NIST-1633a (coal fly ash) reference material. The detection limit of the proposed method was 2.4 µg L-1 and the characteristic mass of 233 pg was achieved. The Ge concentrations in fly ash and hot spring samples were between 6.25-132 µg g-1 and 12.84-36.2 µg l-1.

"A Critical Examination Of Sorbent Extraction Pre-concentration With Spectrophotometric Sensing In Flowing Systems"
Talanta 2004 Volume 64, Issue 2 Pages 290-301
Manuel Mir&oacute; and Wolfgang Frenzel

Abstract: In this paper, the solid-phase spectrophotometric concept is critically examined in flow systems exploiting a dedicated microcolumn-based optical sensor packed with octadecyl chemically-modified silica gel. The flow configuration integrates matrix separation with pre-concentration and on-column sensing of non-polar complexes resulting from analyte derivatization. The design criteria for optimum performance of both the sorbent-packed microcolumn and optosensing instrumentation are for the first time discussed in detail. Practical considerations required to warrant the maximum sorption efficiency of the reversed-phase material by avoiding chain collapse, and avenues to overcome the effects derived from its transparency changes upon solvation with solutions of different polarity are also addressed. The noteworthy features of the flow-through enrichment system involve the sensitivity enhancement with respect to common spectrophotometric procedures in the liquid-phase, as well as the capture of a large amount of scattered light, which is the most severe pitfall of conventional solid-phase absorptiometric approaches using commercially available flow-through cells.Several common spectrophotometric assays for monitoring key inorganic and organic parameters (viz. oxidized nitrogen, ammonium, sulfite, phosphate, iron(II)/total iron, chromium(VI), nickel(II) and phenol index) in environmental samples are taken as practical examples. Plausible sorption mechanisms together with discussions for proper performance of the different investigated reversed-phase extraction optosensing methods are presented in the bulk of the text. Special emphasis is paid to problems arising in real sample analysis due to unspecific sorption of matrix constituents and potential means to circumvent them are thoroughly explored.

"Characterisation Of A Gas-diffusion Membrane-based Optical Flow-through Sensor Exemplified By The Determination Of Nitrite"
Talanta 2004 Volume 64, Issue 2 Pages 278-282
Wolfgang Frenzel, J&uuml;rgen Schulz-Br&uuml;ssel and Betty Zinvirt

Abstract: A membrane-based optical flow-through sensor is described which can be alternatively used for absorbance and reflectance detection within the receiver channel of a sandwich-type gas-diffusion separation cell. Using the common spectrophotometric detection scheme for nitrite based on azo-dye formation, the principle features of the flow-through sensor are investigated and the performance is characterized particularly with regard to selectivity and sensitivity aspects. The determination of nitrite in waste waters and meat extracts was used to demonstrate the applicability to real sample analysis. The main advantage of the proposed flow-through sensor is the absence of interferences due to sample color and turbidity enabling direct sample admission of complex samples without tedious sample pretreatment.

"On-line Preconcentration Of Rhodium On An Anion-exchange Resin Loaded With 1,5-bis(2-pyridyl)-3-sulphophenyl Methylene Thiocarbonohydrazide And Its Determination In Environmental Samples"
Talanta 2004 Volume 64, Issue 1 Pages 230-236
F. S&aacute;nchez Rojas, C. Bosch Ojeda and J. M. Cano Pav&oacute;n

Abstract: A method for the determination of rhodium in different samples at trace levels is presented. The investigated metal is pre-concentrated on a chelating resin microcolumn (1,5-bis(2-pyridyl)-3-sulphophenyl methylene thiocarbonohydrazide (PSTH) immobilized on an anion-exchange resin (Dowex 1 x 8-200)) placed in the autosampler arm. The modification of the autosampler in the tubing line and circuit allowed either the flow of the sample through the column or the operation of the autosampler in the normal mode, where microlitres of 4 M HNO3, which acts as the elution agent, pass through the microcolumn eluting Rh(III), which is directly deposited in the graphite tube as drop of a precisely defined volume. The detection limit is 0.3 ng mL-1. Linearity is maintained in the concentration range 0-50 ng mL-1 for rhodium, with correlation factor of 0.999 and relative standard deviation of 1.8% for 10 ng mL-1 of Rh. The effects of various parameters such as pH, concentration and volume of eluent, sample loading time, sample flow rate and interference of a large number of metal ions and anions on the determination of this metal was studied in detail to optimize the conditions for their determination in various samples. The method is found to be highly selective, fairly sensitive, simple, rapid and economical and may be safely applied to their determination in different complex materials such as environmental samples and catalysts. © 2004 Elsevier B.V. All rights reserved.

"Tandem Focused Ultrasound (TFU) Combined With Fast Furnace Analysis As An Improved Methodology For Total Mercury Determination In Human Urine By Electrothermal-atomic Absorption Spectrometry"
Talanta 2004 Volume 64, Issue 1 Pages 217-223
J. L. Capelo, C. D. dos Reis, C. Maduro and A. Mota

Abstract: A new sample preparation procedure based on tandem (that is, different diameter probe sonicators used in the same sample treatment) focused ultrasound (TFU) for mercury separation, pre-concentration and back-extraction in aqueous solution from human urine has been developed. The urine is first oxidized with KMnO4/HCl/focused ultrasound (6 mm probe). Secondly, the mercury is extracted and pre-concentrated with dithizone and cyclohexane. Finally, the mercury is back-extracted and pre-concentrated again with the aid of focused ultrasound (3 mm probe). The procedure allows determining mercury by electrothermal atomic absorption spectrometry with fast furnace analysis and calibration against aqueous standards. Matrix modification is provided by the chemicals used in the sample treatment. The procedure is accomplished with low sample volume (8.5 ml). Low volume and low concentration reagents are used. The sample treatment is rapid (less than 3 min per sample) and avoids the use of organic phase in the graphite furnace. The pre-concentration factor used in this work was 14. The limit of detection and the limit of quantification in urine were, respectively, 0.27 and 0.9 µg l-1. The relative standard deviation of aqueous standards (n=10) was 4% for a concentration of 100 µg L-1 and 5% for a concentration of 400 µg l-1. Recoveries from spiked urine with inorganic mercury, methyl-mercury, phenyl-mercury and diphenyl-mercury ranged from 86 to 98%.

"Application Of Silica Gel Organofunctionalized With 3(1-imidazolyl)propyl In An On-line Preconcentration System For The Determination Of Copper By FAAS"
Talanta 2004 Volume 64, Issue 1 Pages 181-189
Edson Luiz da Silva, Amarildo Otavio Martins, Antoninho Valentini, Valfredo Tadeu de F&aacute;vere and Eduardo Carasek

Abstract: This study presents a new procedure for the determination of trace levels of copper(II) in an aqueous matrix, through flow injection (FI) on-line pre-concentration with a minicolumn packed with silica gel modified with 3(1-imidazolyl)propyl groups. After the pre-concentration stage, the analyte was eluted with a HNO3 solution and determined by flame atomic absorption spectrometry (FAAS). The measurements of the analytical signals were carried out as peak area and peak height with the objective of evaluating the most appropriate absorption measurement for the proposed method. Four procedures to calculate the experimental enrichment factor (EF) were also studied. For a pre-concentration time of 90 s the enrichment factors found in this study varied between 19.5-25.8 and 36.2-42.2 for peak area and peak height, respectively. The precision of the proposed method was calculated for a solution containing 20 ?g L-1 of Cu(II), when 11.2 mL of solution was pre-concentrated (n=7), and their respective relative standard deviation (RSD) values were 1.2 and 1.4% for peak area and peak height, respectively. The detection limits obtained were 0.4 and 0.2 ?g L-1 of Cu(II) for peak area and peak height, respectively, with a pre-concentration time of 90 s. The on-line pre-concentration system accuracy was evaluated through a recovery test on the aqueous samples and analysis of a certified material. © 2004 Elsevier B.V. All rights reserved.

"4-Amino-1-naphthylphosphate As A Substrate For The Amperometric Detection Of Alkaline Phosphatase Activity And Its Application For Immunoassay"
Talanta 2004 Volume 64, Issue 1 Pages 174-180
M&aacute;r M&aacute;sson, &Ouml;gmundur V. R&uacute;narsson, Fjalar J&oacute;hannson and Masuo Aizawa

Abstract: Immunosensors and biochemical array detection systems based on electrochemical transducers have many advantages such as low detection limit, fast response, simple design and ease of miniaturization. However, further development of such sensors will depend on the availability of suitable substrates that can be converted by a labeling enzyme to an electrochemically active product. Here, we report the synthesis of 4-amino-1-naphthylphosphate and it's application as a new substrate for alkaline phosphatase. The electrochemical and enzymatic properties of this compound were investigated and compared with the properties of other aromatic 1,4-dihydroxy and 1,4-hydroxy-amine derivatives. The product of the enzyme reaction was 4-aminonaphthol, which was rapidly converted in the presences of air to 1,4-iminonaphthoquinone. This compound could then be detected in an amperometric flow injection assay (AFIA) with -200 mV versus Ag/AgCl potential application. The analytical range for mouse IgG, in an alkaline phosphatase amplified sandwich immunoassay with amperometric detection, was 0.01-100 µg mL-1.

"Potassium Permanganate-glyoxal Chemiluminescence System For Flow Injection Analysis Of Cephalosporin Antibiotics: Cefalexin, Cefadroxil, And Cefazolin Sodium In Pharmaceutical Preparations"
Talanta 2004 Volume 64, Issue 1 Pages 156-159
Yuanyuan Sun, Yuhai Tang, Hong Yao and Xiaohui Zheng

Abstract: A sensitive flow injection chemiluminescence (FL-CL) method for the determination of cephalosporin antibiotics, was developed. The method was based on that cephalosporin antibiotics could enhance the CL reaction of glyoxal and KMnO4 in sulfuric acid. Method development included the optimization of reagent concentrations and flow-rate. Under the optimized conditions, three cephalosporin antibiotics: cefalexin, cefadroxil, and cefazolin sodium, were determined. The detection limits of the method are 10 ng mL-1 cefalexin, 2 ng mL-1 cefadroxil, and 2 ng mL-1 cefazolin sodium. The method was successfully applied to the determination of three cephalosporin antibiotics in pharmaceutical preparations.

"Simultaneous Determination Of -thyroxine (-T4), -thyroxine (-T4), And -triiodothyronine (-T3) Using A Sensors/sequential Injection Analysis System"
Talanta 2004 Volume 64, Issue 1 Pages 151-155
Raluca-Ioana Stefan, Jacobus F. van Staden and Hassan Y. Aboul-Enein

Abstract: Requirements of high purity and enantiopurity for the raw materials of active substances used for the pharmaceutical formulations involved utilization of high reliable analytical techniques for the analysis of the active compound. Sequential injection analysis system with electrochemical sensors as detectors proved to be a very good alternative for the chromatographic methods, as it is more reliable, not expensive, and faster. Drugs containing only -thyroxine (-T4) or both -T4 and -triiodothyronine (-T3) are formulated for the dysfunctions of thyroid. A sequential injection analysis system that can use two amperometric immunosensors (for the assay of -T3 and -T4) and an amperometric biosensor (for the assay of -thyroxine, -T4) as detectors is proposed for the purity and enantiopurity tests of the raw materials used for the formulation of the drugs for thyroid. The system proved to be very reliable. The three compounds can be determined on-line in synthesis process control with a frequency of 20 samples per hour.

"Comparison Of Soluble Manganese(IV) And Acidic Potassium Permanganate Chemiluminescence Detection Using Flow Injection And Sequential Injection Analysis For The Determination Of Ascorbic Acid In Vitamin C Tablets"
Talanta 2004 Volume 64, Issue 1 Pages 130-134
Nicole Anastos, Neil W. Barnett, Benjamin J. Hindson, Claire E. Lenehan and Simon W. Lewis

Abstract: The limits of detection (3s) for ascorbic acid were 5 x 10^-8 M with acidic potassium permanganate using both flow injection analysis (FIA) and sequential injection analysis (SIA) whereas the soluble manganese(IV) afforded 1 x 10^-8 M and 5 x 10^-9 M for FIA and SIA, respectively. Determinations of ascorbic acid in Vitamin C tablets were achieved with minimal sample pretreatment using a standard additions calibration and gave good agreement with those of iodimetric titration.

"Determination Of Orthophosphates Using A Macro Segmented Flow Analyzer (MSFA) Based On Colorimetric Detection"
Talanta 2004 Volume 64, Issue 1 Pages 60-68
J. R. E. Thabano, C. Tjell Jens and G. M. Sawula

Abstract: Fabrication of a macro segmented flow analysis (MSFA) system based on reconfiguration of the manifold by adjustment of the sample/reagent ratio, has been found to produce a sensitive method for orthophosphate analysis based on colorimetric detection at 880 nm. Optimization of sample tube length, reaction temperature and molybdate concentration in the carrier solutions has been carried out. The larger sample tube internal diameter led to the combined advantages of better sensitivities, wider working range and higher sample throughput over most existing methods. Using the optimized conditions of 50.0 cm sample tube length (1.6 mm i.d.), 37.0°C reaction temperature and 0.0113 M molybdate concentration in the carrier solution, the calibration model for orthophosphate standard solutions was found to be linear (y = 0.04895x + 0.003561; correlation coefficient, r2=0.9970) over the working range 0.01-2.00 mg L-1 orthophosphate. The volume of the sample injected was 1.396 mL at a flow rate of 6.0 mL min-1. The sample throughput of this MSFA method was 40 samples per an hour, with a detection limit of 4.0 µg l-1, and %RSD's below 5%. The MSFA method was successfully applied to analysis of water and wastewater samples.

"Prussian Blue Modified Glassy Carbon Electrodes--study On Operational Stability And Its Application As A Sucrose Biosensor"
Talanta 2004 Volume 64, Issue 1 Pages 3-12
B. Haghighi, S. Varma, F. M. Alizadeh Sh., Y. Yigzaw and L. Gorton

Abstract: Stabilisation of electrochemically deposited Prussian blue (PB) films on glassy carbon (GC) electrodes has been investigated and an enhancement in the stability of the PB films is reported if the electrodes are treated with tetrabutylammonium toluene-4-sulfonate (TTS) in the electrochemical activation step following the electrodeposition. A multi-enzyme PB based biosensor for sucrose detection was made in order to demonstrate that PB films can be coupled with an oxidase system. A tri-enzyme system, comprising glucose oxidase, mutarotase and invertase, was crosslinked with glutaraldehyde and bovine albumin serum on the PB modified glassy carbon electrode. The deposited PB operated as an electrocatalyst for electrochemical reduction of hydrogen peroxide, the final product of the enzyme reaction sequence. The electrochemical response was studied using flow injection analysis for the determination of sucrose, glucose and H2O2. The optimal concentrations of the immobilization mixture was standardised as 8 U of glucose oxidase, 8 U of mutarotase, 16 U of invertase, 0.5% glutaraldehyde (0.025 µl) and 0.5% BSA (0.025 mg) in a final volume of 5 µl applied at the electrode surface (0.066 cm2). The biosensor exhibited a linear response for sucrose (4-800 µM), glucose (2-800 µM) and H2O2 (1-800 µM) and the detection limit was 4.5, 1.5 and 0.5 µM for sucrose, glucose and H2O2, respectively. The sample throughput was ~60 samples h-1. An increase in the operational and storage stability of the sucrose biosensor was also noted when the PB modified electrodes were conditioned in phosphate buffer containing 0.05 M TTS during the preparation of the PB films.

"Application Of Doehlert Matrix To The Study Of Flow Injection Procedure For Selenium (IV) Determination"
Talanta 2004 Volume 63, Issue 4 Pages 1089-1094
F. Hellal and M. Dachraoui

Abstract: A method for the rapid determination of selenium is reported. It is based on the injection of selenium sample into a stream of KI and subsequent measurement of the increase of the absorption at 290 nm due to the formation of I3-. A Doehlert matrix was applied for the determination of the optimal working conditions. With the developed method, a linear calibration curve from 1 to 10 ppm was obtained. For the analysis of semiconducting thin layers of CuInSe2 (CIS), a cationic resin was added to the sample solution in order to eliminate the effect of copper and indium on the absorbance values. With the developed procedure a sample throughput of 36 samples per hour and a relative standard deviation 1.1% was achieved.

"On-line Determination Of Mercury(II) By Membrane Separation Flow Injection Analysis"
Talanta 2004 Volume 63, Issue 4 Pages 1069-1075
Nazanin Amini, Terence J. Cardwell, Robert W. Cattrall, Richard J. S. Morrison and Spas D. Kolev

Abstract: A rapid and inexpensive gas-diffusion (GD) flow injection method for the on-line determination of Hg(II) in aqueous samples is described. The analytical procedure involves the injection of a Hg(II) sample into a 1.5 M H2SO4 carrier stream which is merged with a reagent stream containing 0.6% SnCl2 and 1.5 M H2SO4. Under these conditions Hg(II) is reduced to metallic mercury which partially evaporates through a Teflon membrane into an acceptor stream containing 1.75 x 10^-4 M KMnO4 in 0.3 M H2SO4. The decrease in the absorbance of the acceptor stream at 528 nm corresponding to the absorption maximum of the permanganate anion can be related to the original concentration of Hg(II) in the sample. The method is characterized by a detection limit of 4 µg L-1 and a sampling frequency of 8 h-1. The flow system was successfully applied to the analysis of river samples spiked with Hg(II).

"On-line And Off-line Preconcentration Of Trace And Ultratrace Amounts Of Lanthanides"
Talanta 2004 Volume 63, Issue 4 Pages 949-959
T. Prasada Rao and R. Kala

Abstract: The need for pre-concentration of trace and ultratrace amounts of lanthanides from environmental, geological and biological samples is brought out in introductory part. Both on-line and off-line pre-concentration procedures developed for lanthanides since 1980 are reviewed. The pre-concentration techniques covered in this review include liquid-liquid extraction (LLE), ion-exchange, co-precipitation, and solid phase or solid-liquid extraction. Separate sections are devoted to each of the pre-concentration techniques employed for enrichment of individual or mixtures of lanthanides. Future trends in singular or multielement pre-concentration of lanthanides are also discussed.

"Flow Injection System With In-line Winkler's Procedure Using 16-way Valve And Spectrofluorimetric Determination Of Dissolved Oxygen In Environmental Waters"
Talanta 2004 Volume 63, Issue 4 Pages 893-898
Tadao Sakai, Shanji Piao, Norio Teshima, Tadafumi Kuroishi and Kate Grudpan

Abstract: Flow injection spectrofluorimetry with in-line Winklers procedure was developed for the dissolved oxygen (DO) determination. 2-Thionaphthol reacted with iodine produced by Winkler's method to form fluorescence inactive disulfide compound. To automate the process completely, a 5-channel flow system with a newly designed 16-way valve was assembled. The system consisted of a dispersion coil (DC), a precipitate formation coil (PFC), a precipitate dissolving coil (PDC), and extraction coil (EC). A calibration can be constructed by using a standard iodine solution for dissolved oxygen. The calibration graph was linear over the range 1.2 x 10^-4~6.0 x 10^-4 mol L-1 iodine (1.96~9.80 mg O l-1)). The relative standard deviation (n=6) was below 0.3% for the 4 x 10^-4 mol L-1 iodine (6.27 mg O l-1) determination. The sample throughput was 12/h.

"Development Of A Flow Manifold For Fe(III) Ion Determination With A Fluoride Ion-selective Electrode"
Talanta 2004 Volume 63, Issue 3 Pages 777-783
M. Bralic, S. Brini, E. Generali and L. Vrsalovi

Abstract: Continuous-flow (CF) and flow-injection (FI) analysis using the fluoride ion-selective electrode (FISE) as detector have been investigated. The measurements were performed in a home-made cell under appropriate flow conditions (2.86 or 3.45 mL min-1, 0.2 mL samples, 10^-6 M sodium fluoride). The calibration graph was obtained by plotting the signal height versus concentration of iron in the range of Fe(III) concentration from 10^-5 to 10^-1 M in acetate buffer (pH 2.8 or 3.4). In all described procedures, the range of linear response extends to the Fe(III) concentration from 1 x 10^-3 to 1 x 10^-1 M, with detection limit 9 x 10^-5 M. The effect of double-line, two-line flow manifold and CF was investigated and discussed.

"On-line Microdialysis Assay Of Image-lactate And Pyruvate In Vitro And In Vivo By A Flow-injection System With A Dual Enzyme Electrode"
Talanta 2004 Volume 63, Issue 3 Pages 771-775
Toshio Yao and Takayuki Yano

Abstract: A flow-injection biosensor system with an on-line microdialysis sampling is proposed for the simultaneous assay of Image-lactate and pyruvate in serum and rat brain. The dialysate collected in the sample loop by perfusing Ringer's solution through the microdialysis probe is automatically injected into the flow-injection line with a dual enzyme electrode arranged in parallel for the flow direction. The dual enzyme electrode is constructed by hybridizing a poly(1,2-diaminobenzene) film to two sensing parts, which respond selectively to Image-lactate and pyruvate, respectively, without any cross-reactivity. Both the sensing parts respond linearly to the concentrations of both analytes between 0.01 and 5 mM, without any interference from oxidizable species and low-molecular weight proteins present in the dialysate. The proposed flow-injection analysis (FIA) method can be successfully applied to the simultaneous in vitro and in vivo assays of both analytes in serum and rat brain, respectively. The system can be automatically processed at an analytical speed of 19 dialysates h-1 over a period of 5 h.

"Sequential Injection Analysis Of Chloride And Nitrate In Waters With Improved Accuracy Using Potentiometric Detection"
Talanta 2004 Volume 63, Issue 3 Pages 721-727
Em&iacute;lia Santos, M. Concei&ccedil;&atilde;o B. S. M. Montenegro, Cristina Couto, Alberto N. Ara&uacute;jo, M. Fernanda Pimentel and Valdinete Lins da Silva

Abstract: Accurate simultaneous analysis of different anionic species using ion-selective electrodes (ISEs) can be achieved even for non-specific sensors by resorting to an ordinary least squares multiple regression in the vicinity of the predicted concentrations. In this work the potentialities of this approach are evidenced by the determination of nitrate and chloride in synthetic and real water samples in which chloride concentration was significantly higher than nitrate. An AgCl/Ag2S electrode based on a homogeneous crystalline membrane together with a PVC electrode based on tert-octylammonium bromide dissolved in dibutylphthalate were used as potentiometric detectors for chloride and nitrate, respectively. For the implementation of the procedure, an automatic system based on sequential injection analysis was used. The results obtained by the standard addition method were biased for low concentrations of nitrate and were dependant on the relative proportion of NO3-/Cl-. The results obtained by the proposed methodology for chloride determination were slightly better when compared to those obtained by the standard addition method. In relation to nitrate determination, the proposed methodology yielded values with a relative root mean square error of prediction (RRMSEP) of 2.8%, while for standard addition calibration, mean error values were approximately 12.1%.

"Characterisation Of A Hydraulic High-pressure Sample Introduction Assisted Flow Injection--inductively Coupled Plasma Time-of-flight Mass Spectrometry System And Its Application To The Analysis Of Biological Samples"
Talanta 2004 Volume 63, Issue 3 Pages 705-712
Zsolt Stef&aacute;nka, L&aacute;szl&oacute; Abrank&oacute;, Mih&aacute;ly Dernovics and P&eacute;ter Fodor

Abstract: A flow injection (FI) method was developed using hydraulic high-pressure nebulization as a sample introduction system, coupled to inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) for rapid and simultaneous determination of 19 elements. The operating conditions of the system (analyte flow rate, heating and cooling temperatures of the desolvation module, carrier gas flow rate) for the simultaneous determination of 19 analytes were optimized. The optimum parameters of the sample introduction system were found to be 1.4 mL min-1 and 1.35 l min-1 for the analyte solution and nebulizer flow rates, respectively. A compromised condition for heating and cooling stage temperatures of 170 and -5°C was chosen. The detection limits were compared to those obtained by using ICP-TOFMS with alternative sample introduction techniques e.g. conventional nebulization, flow injection chemical hydride generation (FI-CHG) and the obtained results were comparable or better than those resulting from alternative sample introduction. Applying the optimized conditions the simultaneous determination of Ag, As, Ba, Cd, Co, Cu, Ga, In, Li, Mn, Mo, Pb, Sb, Se, Sn, Sr, Tl, V and Zn was carried out. Absolute detection limits (3s) in the range of 2-750 pg and precision between 0.5 and 9.6% from five replicate measurements of 10 ng mL-1 multielemental sample solutions were achieved by using a 200 µl sample loop. The developed method was applied for the analysis of certified reference materials of biological origin (TORT-2 'Lobster Hepatopancrease', BCR-422 'Cod Muscle' and IAEA MA-B-3/TM 'Fish Homogenate'), and the results showed good agreement with the certified values.

"Sequential Injection Spectrophotometric Determination Of Phenylephrine Hydrochloride In Pharmaceutical Preparations"
Talanta 2004 Volume 63, Issue 3 Pages 599-604
Negussie W. Beyene and Jacobus F. Van Staden

Abstract: A fully automated sequential injection spectrophotometric method for the determination of phenylephrine hydrochloride in pharmaceutical preparations is reported. The method is based on the condensation reaction of the analyte with 4-aminoantipyrine in the presence of potassium ferricyanide. The absorbance of the condensation product was monitored at 503 nm. A linear relationship between the relative peak height and concentration was obtained in the range 0.5-17.5 mg l-1. The detection limit (as 3s value) was 0.09 mg L-1 and repeatability was 0.8 and 0.6% at 2.5 and 5 mg l-1, respectively. Results obtained by this method agreed very well with those obtained by the AOAC official method.

"Flow Injection Determinations Of Citric Acid: A Review"
Talanta 2004 Volume 63, Issue 3 Pages 509-514
A. Moreno-Cid, M. C. Yebra and X. Santos

Abstract: A review of the flow injection (FI) analytical methods used to determine citric acid (CA) is presented. These flow determinations are described and compared according to the detection technique used. In addition to the advantages involving the use of the continuous flow systems, the analytical figures of merit and interferences are also discussed.

"Separation And Determination Of Aloperine, Sophoridine, Matrine And Oxymatrine By Combination Of Flow Injection With Microfluidic Capillary Electrophoresis"
Talanta 2004 Volume 63, Issue 2 Pages 491-496
Yuqiao Cheng, Hongli Chen, Yuqin Li, Xingguo Chen and Zhide Hu

Abstract: A novel, rapid and accurate method for the separation and determination of aloperine (ALP), sophoridine (SRI), matrine (MT) and oxymatrine (OMT) has been developed by combination of flow injection (FI) with microfluidic capillary electrophoresis (CE) for the first time. In the present paper, a continuous sample introduction interface was described. The interface with an H-channel structure was produced using a non-lithographic approach. The H-channel structure was fixed on a planar plastic base utilizing a horizontal 6.5 cm-long separation capillary with two vertical sidearm tubes on each end that served as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functioned as interface for coupling to the FI system. The buffer solution used was a 50 mmol L-1 borate solution with the pH adjusted to 8.80 with 2 mol L-1 HCl. The performance of the system was demonstrated in the separation and determination of ALP, SRI, MT and OMT with UV detection at 215 nm, achieving baseline separation within 2 min. A series of samples was injected repeatedly without current interruption and subsequent rinsing, and the contents of these four bio-alkaloids in two marketed drugs were determined with satisfactory recovery by this proposed method. © 2003 Elsevier B.V. All rights reserved.

"A Sensitive Spectrophotometric Method For Lead Determination By Flow Injection Analysis With On-line Preconcentration"
Talanta 2004 Volume 63, Issue 2 Pages 405-409
Mar&iacute;a S. Di Nezio, Miriam E. Palomeque and Beatriz S. Fern&aacute;ndez Band

Abstract: A new flow injection (FI) system for the determination of Pb(II) at trace level with a pre-concentration step and spectrophotometric detection is proposed. It is based on pre-concentration of lead ions on chitosan and dithizone-lead complex formation in aqueous medium (pH 9). The chemicals and FIA variables influencing the performance of the system were optimized and applied to the determination of lead in natural, well, and drinking water samples. It is a simple, highly sensitive, and low cost alternative methodology. The method provided a linear rage between 25 and 250 µg l-1, a detection limit of 5.0 ng mL-1 and a sample throughput of 15 h-1. The obtained results of spiked samples are in good agreement between the proposed method and ICP-AES.

"Sulphoxine Immobilized Onto Chitosan Microspheres By Spray Drying: Application For Metal Ions Preconcentration By Flow Injection Analysis"
Talanta 2004 Volume 63, Issue 2 Pages 397-403
Amarildo Otavio Martins, Edson Luiz da Silva, Eduardo Carasek, Mauro C. M. Laranjeira and Valfredo T. de F&aacute;vere

Abstract: A new chelating resin based on chitosan biopolymer modified with 5-sulphonic acid 8-hydroxyquinoline using the spray drying technique for immobilization is proposed. The chelating resin was characterized by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and surface area by nitrogen sorption. The efficiency of the chelating resin was evaluated by the pre-concentration of metal ions Cu(II) and Cd(II) present in aqueous samples in trace amounts. The metal ions were previously enriched in a minicolumn and the concentrations of the analytes were determined on-line by flame atomic absorption spectrometry (FAAS). The maximum retention for Cu(II) occurred in the pH range 8-10, and for Cd(II) at pH 7. The optimum flow rate for sorption was found to be 7.2 mL min-1 for the pre-concentration of the metal ions. The analytes gave relative standard deviations (RSD) of 0.7 and 0.6% for solutions containing 20 µg L-1 of Cu(II) and 15 µg L-1 of Cd (II), respectively (n=7). The enrichment factors for Cu(II) and Cd (II) were 19.1 and 13.9, respectively, and the limits of detection (LOD) were 0.2 µg L-1 for Cd(II) and 0.3 µg L-1 for Cu(II), using a pre-concentration time of 90 s (n=11). The accuracy of the proposed method was evaluated by the metal ion recovery technique, in the analysis of potable water and water from a lake, with recoveries being between 97.2 and 107.3%.

"Hydrophobic Interaction Chromatography Coupled With Atomic Fluorescence Spectrometric Detection: Effect Of The Denaturation On The Determination Of Thiolic Proteins"
Talanta 2004 Volume 63, Issue 2 Pages 383-389
Emilia Bramanti, Chandra Sortino, Cristina Lomonte, Massimo Onor, Roberto Zamboni, Giorgio Raspi and Alessandro D Ulivo

Abstract: Hydrophobic interaction chromatography coupled online with chemical vapor atomic fluorescence spectrometry (HIC-CVGAFS) has been optimized for the analysis of thiolic proteins in denaturing conditions. Proteins are pre-column simultaneously denatured and derivatized in phosphate buffer solution containing 8.0 mol L-1 urea and p-hydroxymercurybenzoate (PHMB) and the derivatized denatured proteins are separated on a silica HIC Eichrom Propyl column in the presence of 8.0 M urea in the mobile phase. Post-column online reaction of derivatized denatured proteins with bromine, generated in situ by KBr/KBrO3 in HCl medium, allowed the fast conversion of the uncomplexed PHMB and of the PHMB bound to proteins to inorganic mercury also in presence of urea. Hg2+, present in solution as Hg2+-urea complex, is selectively detected by AFS in a Ar/H2 miniaturized flame after sodium borohydride reduction to Hg. Under optimized conditions, online bromine treatment gives a 100±2% recovery of both free and protein-complexed PHMB. Denatured glyceraldehyde-3-phosphate dehydrogenase, aldolase, lactate dehydrogenase, trioso phosphate isomerase and β-lactoglobulin have been examined. As the sensitivity and limit of detection of proteins in the HIC-CVGAFS apparatus depends on number of ---SH groups reacting with PHMB, the denaturation process, which increases the number of PHMB-reactive thiolic groups in proteins, improves the analytical performances of the described system in protein analysis. The detection limit for the denatured proteins examined was found in the range of 10^-10-10-12 mol L-1, depending on the considered protein, with linear calibration curves spanning over four decades of concentration.

"Differentiation Of Sparkling Wines (cava And Champagne) According To Their Mineral Content"
Talanta 2004 Volume 63, Issue 2 Pages 377-382
A. Jos, I. Moreno, A. G. Gonz&aacute;lez, G. Repetto and A. M. Came&aacute;n

Abstract: The metal content of a number of sparkling wines was determined by atomic spectrometry techniques. Al, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn by using inductively coupled plasma atomic emission spectrometry (ICP-AES); Cd, Ni and Pb by graphite furnace atomic absorption spectrometry (GFAAS) and As from hydride generation AAS (HGAAS). Two kinds of sparkling wines were studied with D.O. trademark: cava and champagne. 18 samples of 'brut' cava and 17 samples of 'brut' champagne of different brands were analyzed following the procedure described in the paper. By using the metal concentrations as chemical descriptors the two classes of samples (cava and champagne) are perfectly discriminated, when applying pattern supervised learning recognition techniques such as linear discriminant analysis (LDA) and soft independent modeling of class analogie (SIMCA). The number of false positives and negatives were zero, which indicates a remarkable authentication power of the descriptors used.

"FT-Raman Spectrometry Determination Of Malathion In Pesticide Formulations"
Talanta 2004 Volume 63, Issue 2 Pages 345-350
Guillermo Quint&aacute;s, Salvador Garrigues and Miguel de la Guardia

Abstract: A fast and environmentally friendly method has been developed for Fourier transform-Raman (FT-Raman) spectrometry determination of Malathion in pesticide emulsifiable concentrate formulations. The method is based on the measurement of intensity peak height values at 1737 cm-1 Raman shift corrected using a baseline defined at 1900 cm-1. Samples were diluted with CHCl3 and the FT-Raman spectra collected in back-scattering mode over 3.3 min at a nominal resolution of 4 cm-1 accumulating 50 scans per spectra and using a laser power of 1250 mW. The developed procedure provided a limit of detection of 1.8% w/w in the original sample. Results found by FT-Raman spectrometry were statistically comparable with those obtained by flow injection Fourier transform infrared spectrometry, FIA-FTIR, and gas chromatography (GC) and were in good agreement with those reported by the manufacturer. The FT-Raman developed procedure reduces drastically the chlorinated solvent waste generation and avoids the contact of the operator with toxic products, being a fast alternative to the CIPAC recommended GC procedure.

"Reverse Flow Injection Spectrophotometric Determination Of Iodate And Iodide In Table Salt"
Talanta 2004 Volume 63, Issue 2 Pages 339-343
Zhihai Xie and Jingchan Zhao

Abstract: A very simple and sensitive reverse flow injection method is described for the determination of iodate and iodide. The iodate reacts with excess iodide in acidic medium to form tri-iodide, which can be spectrophotometrically monitored at 351 nm, and the absorbance is directly related to the concentration of iodate in the sample. The determination of iodide is based on oxidizing iodide to iodate. The calibration curve is linear in the range of 0.02-3.0 µg mL-1 I with r2=0.9998, and the limit of detection is 0.008 µg mL-1 I. The chemical and flow injection variables were studied and optimized to make the procedure suitable for quantitating iodate and iodide in table salts. It is shown that the reverse flow injection analysis could greatly improve the sensitivity and precision for determination of iodate with a relative standard deviation of 0.9%. A complete analysis, including sampling and washing, could be performed in 35 s. The procedure was applied successfully to the determination of iodate and iodide in table salts, and the results were statistically compared with results determined by standard iodometry method.

"Determination Of Total Bilirubin In Human Serum By Chemiluminescence From The Reaction Of Bilirubin And Peroxynitrite"
Talanta 2004 Volume 63, Issue 2 Pages 333-337
Chao Lu, Jin-Ming Lin and Carmen W. Huie

Abstract: Peroxynitrous acid (ONOOH) was produced by the on-line reaction of acidified hydrogen peroxide with nitrite in a flow system, and peroxynitrite (ONOO-) was generated from ONOOH in NaOH solution. A weak chemiluminescent (CL) emission was observed due to the production of singlet oxygen (1O2) during the decomposition of ONOO-. Bilirubin and its conjugate were found to enhance the CL emission of 1O2 in a suitable micellar medium. For the first time, the feasibility of employing the present CL system for the sensitive and selective determination of total bilirubin contents in human serum was demonstrated and the results were compared with certified values. The present method showed a great improvement on overcoming bis(2,4,6-trichlorophenyl)oxalate CL highly insolubility in aqueous solution and exhibiting higher tolerance towards interferences than redox reaction of bilirubin with various oxidizing agents such as sodium hypochlorite and iodine. The recoveries of bilirubin were found to fall in the range between 95 and 108%. The detection limits (S/N=3) for bilirubin and its conjugate were determined to be 10 and 8 ng mL-1, respectively. The relative standard deviations (RSD) for the consecutive CL detection of a series of bilirubin (30 µg l-1) and bilirubin ditaurite (25 µg l-1) were 3.2 and 2.9% (n=11), respectively.

"Spectrophotometric Flow-injection Determination Of Zinc In Plant Digests Based On A Spot Test"
Talanta 2004 Volume 63, Issue 2 Pages 245-250
Ana Cristi B Dias, Josiane M.T Carneiro and Elias A.G Zagatto

Abstract: A spot test was implemented in a flow-injection system for the spectrophotometric determination of zinc in digests of plant materials. It is based on the influence of Zn2+ on the oxidation rate of 1-naphthylethylenediamine (NED) by hexacyanoferrate(III) under acidic conditions. In order to control the precipitate formation and to maintain the resulting suspension, a micellar medium was established by adding Triton X-100. The proposed system handles about 65 samples per hour, meaning 72?g NED and 9.0 mg K3[Fe(CN)6] per determination. Baseline drift is usually <0.01 absorbance per hour and the analytical signals for 0.5-2.5 mgl-1 Zn range within ~0.07-0.45 absorbance. Linearity of the analytical curve is fair (r>0.999, n=6) and detection limit was estimated as 0.2 mgl-1 Zn. Results are precise (RSD<1%, n=10) and in agreement with flame atomic absorption spectrometry and with certified values of standard reference materials. © 2003 Elsevier B.V. All rights reserved.

"Application Of Flowing Stream Techniques To Water Analysis: Part III. Metal Ions: Alkaline And Alkaline-earth Metals, Elemental And Harmful Transition Metals, And Multielemental Analysis"
Talanta 2004 Volume 63, Issue 2 Pages 201-223
Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: In the earlier parts of this series of reviews [1 and 2], the most relevant flowing stream techniques (namely, segmented flow analysis, continuous flow analysis, flow injection (FI) analysis, sequential injection (SI) analysis, multicommuted flow injection analysis and multisyringe flow injection analysis) applied to the determination of several core inorganic parameters for water quality assessment, such as nutrients and anionic species including nitrogen, sulfur and halogen compounds, were described.In the present paper, flow techniques are presented as powerful analytical tools for the environmental monitoring of metal ions (alkaline and alkaline-earth metals, and elemental and harmful transition metals) as well as to perform both multielemental and speciation analysis in water samples. The potentials of flow techniques for automated sample treatment involving on-line analyte separation and/or pre-concentration are also discussed in the body of the text, and demonstrated for each individual ion with a variety of strategies successfully applied to trace analysis. In this context, the coupling of flow methodologies with atomic spectrometric techniques such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICPMS) or hydride-generation (HG)/cold-vapor (CV) approaches, launching the so-called hyphenated techniques, is specially worth mentioning.
Molybdenum Cobalt Iron Manganese Mercury Chromium Nickel Lead Copper Cadmium Zinc Aluminum Environmental Review

"Flow Injection Determination Of Nitrite By Fluorescence Quenching"
Talanta 2004 Volume 62, Issue 5 Pages 991-995
Mar&iacute;a Teresa Fern&aacute;ndez-Arg&uuml;elles, Beatriz Ca&ntilde;abate, Jos&eacute; M. Costa-Fern&aacute;ndez, Rosario Pereiro and Alfredo Sanz-Medel

Abstract: A simple, sensitive and selective fluorimetric method for the determination of nitrite ion in waters using a merging zones flow injection system is described. The fluorimetric determination is based on the measurement of the quenching effect produced by nitrite on proflavine (3,6-diaminoacridine) fluorescence (λex/λem=290/519 nm).The optimum experimental conditions were investigated by merging 0.5 mL of the sample and 0.5 mL of a solution of 5 mg L-1 of proflavine (in 0.1 M HCl) in a flow injection system, on-line connected to a flow-cell placed in the conventional sample compartment of a spectrofluorimeter. The selected carrier solution and final flow rate were 0.1 M HCl and 0.5 mL min-1, respectively. A reaction coil of 2 mL was used. As a result of the simplicity of this system, a sample throughput of about 50 samples h-1 can be achieved with the proposed methodology. The detection limit was 1.1 ng mL-1 (3s criterion) of nitrite. The repeatability for five sample injections containing 100 ng mL-1 of nitrite was±0.3% and the observed linear range extended up to 400 ng mL-1. Also, the effect of interferences from various metals and anions commonly present in waters was also studied.The method was successfully applied to the determination of low levels of nitrite in different water samples (river, fountain, tap and commercial drinking waters).

"Arsenic Speciation Patterns In Freshwater Fish"
Talanta 2004 Volume 62, Issue 5 Pages 931-936
Zdenka Slejkovec, Zlatka Bajc and Darinka Z. Doganoc

Abstract: Muscle of 16 freshwater fish (9 different species belonging to 4 different families) was analyzed for arsenic species using HPLC separation (anion and cation exchange) followed by on-line UV-decomposition, hydride generation and AFS detection. The main arsenic compounds found in the extracts were arsenobetaine (AsB), which accounted for 92-100% of extractable arsenic in species of salmonids (Salmo marmoratus, Oncorhynchus mykiss, Salmo trutta m. fario), and dimethylarsinic acid (DMAA), which accounted for 75% of extractable arsenic in burbot (Lota lota). AsB was also found in lower concentrations in almost all other fish species analyzed (Silurus glanis, L. lota, Barbus barbus, Rutilus pigus virgo, Chondrostoma nasus). Arsenite (As(III)) and trimethylarsine oxide (TMAO) were detected in low concentrations in some representatives of Cyprinidae only (R. pigus virgo, C. nasus). Except in salmonids, an unknown cationic compound was present in most of the samples in relatively low concentrations. Cluster analysis of the generated data seems to indicate that there is a correlation between fish family and the arsenic speciation pattern. This is especially clear for the salmonids which show a completely separate cluster and thus a very distinct arsenic speciation pattern.

"Preparation Of Dendrimer-like Polyamidoamine Immobilized Silica Gel And Its Application To Online Preconcentration And Separation Palladium Prior To FAAS Determination"
Talanta 2004 Volume 62, Issue 5 Pages 918-923
X. Z. Wu, P. Liu, Q. S. Pu, Q. Y. Sun and Z. X. Su

Abstract: A amino-terminated G 4.0 dendrimer-like polyamidoamine (PAMAM) immobilized silica gel (PAMAMSG) was prepared with a divergent method by repeating two processes: (1) Michael addition of methyl acrylate (MA) to surface amino groups; and (2) amidation of the resulting esters with ethylenediamine (EDA) from ?-aiminopropyl silica gel (APSG) core. It was then used for the first time as microcolumn packing for the flame atomic absorption spectrometry (FAAS) determination of trace or ultra trace Pd(II), after flow injection (FI) online pre-concentration and separation process. A limit of detection (LOD) of 3.9 ng ml-1 was achieved when 0.200 µg mL-1 Pd(II) was pre-concentrated in 0.2 mol L-1 HCl medium with a sampling flow rate of 6.0 mL min-1 for 60s and the relative standard deviation (RSD) was 1.7%. The proposed method was successfully used for the determination of Pd in two metallurgical samples.

"Flow Injection Analysis Of Zinc Pyrithione In Hair Care Products On A Cobalt Phthalocyanine Modified Screen-printed Carbon Electrode"
Talanta 2004 Volume 62, Issue 5 Pages 912-917
Ying Shih, Jyh-Myng Zen, Annamalai Senthil Kumar and Pei-Yen Chen

Abstract: Zinc pyrithione (ZPT) is an antibacterial and antifungal reagent that is often utilized for the antidandruff activity in hair-care shampoos with a composition level up to 1% in the formulation. It has some adverse effects to human and animal if consumed orally. A disposable type of cobalt phthalocyanide modified screen-printed carbon electrode (CoPc/SPE) in couple with flow injection analysis (FIA) was developed for easy and selective analysis of ZPT in commercial hair-care products. Under the optimized FIA conditions, the CoPc/SPE yielded a linear calibration plot in the window of 6-576 µM with sensitivity and detection limit of 1.65 nA µM-1 and 0.9 µM (i.e. 1.42 pg in 5 µl sample loop), respectively, in 0.1 M KOH solution at an applied potential of 0.3 V versus Ag/AgCl. Since the approach is simple, easy, selective, and inexpensive, it offers a potential application of daily ZPT analysis in hair-care products.

"An Intelligent Flow Analyser For The In-line Concentration, Speciation And Monitoring Of Metals At Trace Levels"
Talanta 2004 Volume 62, Issue 5 Pages 887-895
Carmen Pons, Manuel Mir&oacute;, Eduardo Becerra, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: An intelligent and versatile flow system is proposed for the in-line speciation and/or concentration of metal ions at a wide range of concentrations without requiring manifold reconfiguration. On one hand, sample enrichment strategies are accomplished using packed-bed reactors, on the other hand speciation procedures are readily performed exploiting the selective complexation of the different oxidation states with the appropriate chromogenic reagents.The potentials of the automated methodology were evaluated using the spectrophotometric monitoring of iron as a model of chemistry. Under the optimized physical and chemical variables, linear analytical curves over the ranges 0.025-0.5 or 2.0-40 mg L-1 Fe were attained. The 3s detection limit, the repeatability at the 0.5 mg L-1 level, the enrichment factor for a sampling volume of 10 ml, and the maximum injection throughput were 8.4 ng mL-1 Fe, 2.5%, 58.6 and 22 h-1, respectively. The flowing system was applied to the speciation analysis of iron in waters, pharmaceutical formulations and agricultural products, using ICP-OES detection as an external reference method for total iron determination. A remarkable feature of the expert system hereby presented is the ability to decide by itself if the pre-concentration and/or oxidation of the sample zone is required.
Iron Iron(III) Water Water Sea Speciation Interferences Expert system Method comparison Preconcentration

"Implementation Of Flow-through Multi-sensors With Bead Injection Spectroscopy: Fluorimetric Renewable Surface Biparameter Sensor For Determination Of Berillium And Aluminum"
Talanta 2004 Volume 62, Issue 5 Pages 879-886
M. J. Ruedas Rama, A. Ruiz Medina and A. Molina D&iacute;az

Abstract: For the first time a new, sensitive, and simple bead injection spectroscopy-flow injection analysis (BIS-FIA) system with spectrofluorimetric detection is described for the sequential determination of two metals. The sensor is based on the alternate use of two carriers and a commercially available flow cell (Hellma 176-QS). The flow cell is filled by injecting in the flow system 500 µl of a homogeneous bead suspension of an appropriate solid support (Sephadex QAE A-25) previously loaded with the fluorogenic reagent morin (2',3,4',5,7-pentahydroxyflavone). A sequential reaction of Al(III) and Be(II) with morin (immobilized on beads) to form their fluorescent complexes is performed on the bead sensing support and their respective fluorescence emission monitored, after doing two successive injections from the mixture solution. Firstly, Al(III) could be determined in the sample using 0.5 M NaCl/HCl, pH 6 as carrier. Then, the carrier solution was changed (0.3 M NaCl/NaOH, pH 12) making possible the elution of Al(III) and the restoration of the baseline, then allowing the reaction of Be(II). At the end of the analysis, beads are automatically discarded from the flow cell, by reversing the flow, and transported out of the system. The analytical signals are measured at an excitation wavelength of 440 nm and an emission wavelength of 520 nm. Using a sample volume of 600 µl, the analytical signal showed a very good linearity in the range 0.1-8 ng mL-1 and 0.1-1 µg mL-1 with detection limits of 0.024 ng mL-1 and 0.010 µg mL-1 for Be(II) and Al(III), respectively. RSDs (%) lower than 5% were obtained for both analytes and the selectivity was improved using EDTA as masking reagent. The sensor was satisfactorily applied to the determination of these metals in waters and simulated alloy samples.

"Flow-through Solid-phase Energy Transfer-room Temperature Phosphorescence For Orthophosphate Determinations At Trace Levels"
Talanta 2004 Volume 62, Issue 4 Pages 827-833
Jos&eacute; M. Traviesa-Alvarez, Jos&eacute; M. Costa-Fern&aacute;ndez, Rosario Pereiro and Alfredo Sanz-Medel

Abstract: The development of a flow-through solid-phase room temperature phosphorescence (RTP) method for the sensitive determination of orthophosphate in aqueous samples, based on the energy transfer from a phosphor molecule (acting as a donor) to an orthophosphate dye-indicator (acting as an acceptor) is described.The proposed method, to our knowledge the first RTP optosensor for orthophosphate developed so far, is based on the injection in a flow system of 1 mL sample treated to form phosphomolybdenum blue from the orthophosphate. After injection, the phosphomolybdenum blue is on-line co-immobilized onto a polymeric resin containing adsorbed erythrosine B. This selected donor molecule exhibits strong RTP in a de-oxygenated aqueous media when retained on the surface of polymeric resin beads. Absorption spectra of the phosphomolybdenum blue possess a desirable spectral overlap with the emission spectra of the RTP donor and a non-radiative energy transfer occurs from the phosphor molecule to the acceptor dye. An increase in the concentration of orthophosphate of the solution causes an absorption increase of the acceptor (phosphomolybdenum blue) and, therefore, an increase in the energy transfer, which brings about a decrease of the RTP emission. After measurement, the active sensing phase can be regenerated by passing 2 mL of 2 M sodium hydroxide plus 2 mL of methanol. After the injection of 1 mL of 2 x 10^-6 M erythrosine B the system is prepared again for a new sample injection.Potential interferences by ions present in natural waters, which could affect the optosensor response, and analytical performance characteristics of the RTP method are discussed in detail. An orthophosphate detection limit of 0.5 ng mL-1 (for 1 mL sample injection volume) was achieved. Finally, the selected RTP flow-through optical sensor has been successfully tested for the determination of orthophosphate in different water samples at a very few ng mL-1 levels.

"Rapid On-line Sample Dissolution Assisted By Focused Microwave Radiation For Silicate Analysis Employing Flame Atomic Absorption Spectrometry: Iron Determination"
Talanta 2004 Volume 62, Issue 4 Pages 807-811
Maria Cristina B. Quaresma, Ricardo J. Cassella, Miguel de la Guardia and Ricardo E. Santelli

Abstract: An on-line automated flow injection system with microwave-assisted sample digestion was used to perform silicate rock dissolution in acid medium for iron determination. For this purpose, a continuous flow system was built up by using an automatic flow injection analysis (FIA) system coupled to a flame atomic absorption spectrometer (FAAS), including a focused microwave oven unit. Inside the microwave cavity was inserted a polytetrafluoroethylene (PTFE) reactor coil (300 cm length and 0.8 mm i.d.) where the dissolution takes place. Chemical and flow variables as well as iron determination parameters were studied. In the flow system, a slurry of the rock sample (50 mg in 200 mL of acid mixture HF+HCl+HNO3) is pumped through the reaction coil and the microwaves are turned on. After elapsed the time required to complete the sample dissolution, the mixture is pumped again in order to fill the sampling loop (500 µl). Then, by changing the valve position, a water carrier stream pushes the sample solution through the flame atomic absorption spectrometer nebulizer. To achieve an accurate determination of the rock certified materials, the slurry sample was irradiated during 210 s at 90 W power. Working in that condition, a detection limit of 0.80 µg mL-1 (which corresponds to an Fe2O3 content of 0.46%) and an analytical throughput of 10 h-1 were achieved. The relative standard deviation (RSD) of the method varied between 1 and 11% when applied to the rock certified materials.

"Sequential Extraction Of Phosphorus In Soil And Sediment Using A Continuous-flow System"
Talanta 2004 Volume 62, Issue 4 Pages 765-771
W. Tiyapongpattana, P. Pongsakul, J. Shiowatana and D. Nacapricha

Abstract: Distribution and mobility of phosphorus in soil and sediment are usually studied by sequential extraction. In the extraction procedure, a sample is treated with a series of reagents to distinguish the phases to which phosphorus is associated such as carbonate and iron or manganese oxides, etc. There have been a number of extraction schemes presented for phosphorus. At present, all of the existing schemes are carried out batchwise. Phosphorus contents derived from all sequences are operationally defined and depend on experimental conditions.An extraction procedure, which is a continuous-flow-based technique, was recently proposed by our group for metals in soils and sediments. The extraction is carried out in a closed chamber through which extractants are passed sequentially. In this paper, the system was investigated using the extraction scheme of Hieltjes and Lijklema to study distribution of phosphorus in three certified reference materials (CRMs). A number of fractions were collected for each reagent for subsequent colorimetric determination. The results are compared with those obtained from a batch extraction. The summation of phosphorus contents of all phases were compared with the certified values and with the values obtained from total digestion. These results have demonstrated that the continuous extraction system developed is also applicable for fractionation of phosphorus. Advantage and disadvantage are discussed.

"Flow-injection Chemiluminescence Determination Of Chloroquine Using Peroxynitrous Acid As Oxidant"
Talanta 2004 Volume 62, Issue 4 Pages 757-763
Yao-Dong Liang, Jun-Feng Song, Xiao-Feng Yang and Wei Guo

Abstract: A new flow-injection chemiluminescence (CL) method for determination of chloroquine is proposed based on a stronger chemiluminescence of chloroquine in hydrogen peroxide-nitrite-sulfuric acid medium. The proposed method allows the measurement of chloroquine over the range of 3.0 x 10^-7 to 1.0 x 10^-5 mol L-1. The detection limit is 8.6 x 10^-8 mol L-1, and the relative standard deviation for 1.0 x 10^-6 mol L-1 chloroquine (n=11) is 1.6%. The CL mechanism is also discussed.

"Use Of Nb2O5-SiO2 In An Automated On-line Preconcentration System For Determination Of Copper And Cadmium By FAAS"
Talanta 2004 Volume 62, Issue 4 Pages 727-733
Edson Luiz da Silva, Edgard Moreira Ganzarolli and Eduardo Carasek

Abstract: A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line pre-concentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb2O5-SiO2), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a pre-concentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 µg l-1, respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 µg L-1 of copper and 10 µg L-1 of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples.

"Simultaneous Determination Of Tin, Germanium And Molybdenum By Diode Array Detection-flow Injection Analysis With Partial Least Squares Calibration Model"
Talanta 2004 Volume 62, Issue 4 Pages 719-725
Xiaoli Zou, Yuanqian Li, Menglong Li, Bo Zheng and Jingguo Yang

Abstract: Simultaneous determination of tin, germanium and molybdenum in food samples has been established by flow injection-charge coupled detector (CCD) diode array detection spectrophotometry with partial least squares (PLS) algorithm. The method was based on the chromogenic reaction of metal ions and salicylflurone in the presence of cetyltrimethyl ammonium bromide. The overlapping spectra of these complexes are collected by CCD diode array detector and the multi-wavelength absorbance data are processed using partial least squares algorithm. The reaction conditions and analytical parameters of flow injection analysis have been investigated. The method was applied to directly determine Ge, Mo and Sn in several food samples after digestion with satisfactory results. The recoveries of spiked samples were 80.0-102.0% for tin, 86.3-92.0% for germanium and 83.2-95.2% for molybdenum, and the relative standard deviations for samples were 4.4-7.8%. Molybdenum in certified reference material of cattle liver was determined by the proposed method (n=8). The differential values between determined and guarantee values were within the given uncertain value ranges (t=1.687, P>0.05 for t-test). The samples of mung bean, kelp and pork liver were analyzed by the proposed method and inductively couple plasma-atomic emission spectroscopy (ICP-AES) method. The determination results of the two methods are in good agreement. The sampling rate is 30 samples h-1.
Partial least squares

"Determination Of Carbon Dioxide In Gaseous Samples By Gas Diffusion-flow Injection"
Talanta 2004 Volume 62, Issue 3 Pages 631-636
Sakchai Satienperakul, Terence J. Cardwell, Robert W. Cattrall, Ian D. McKelvie, Douglas M. Taylor and Spas D. Kolev

Abstract: A gas diffusion-flow injection system was developed for the determination of carbon dioxide in gaseous samples. The calibration was based on the use of either gaseous carbon dioxide or aqueous sodium carbonate standards. Gaseous carbon dioxide samples and gaseous or aqueous standards were injected directly into a donor stream of 1.0 x 10^-4 M H2SO4. In the gas diffusion unit, carbon dioxide diffused through a PTFE membrane into an acceptor stream containing a mixed acid/base indicator. The absorbance of the acceptor stream was monitored spectrophotometrically at 554 nm. The calibration plot was linear over the range of 5.00 x 102 to 1.27 x 104 µl L-1 with a sample throughput of 28 h-1 and 3.2% RSD ([CO2]=2.37 x 103 µl l-1, n=12). The detection limit was determined as 2.50 x 102 µl l-1. The flow system was successfully applied to the analysis of several natural gaseous samples and the headspace of milk containers during storage. The flow injection results were found to be statistically indistinguishable at the 95% confidence level from those obtained by gas chromatography using thermal conductivity detection.

"Evaluation Of Zirconium As A Permanent Chemical Modifier Using Synchrotron Radiation And Imaging Techniques For Lithium Determination In Sediment Slurry Samples By ET AAS"
Talanta 2004 Volume 62, Issue 3 Pages 619-626
Araceli V. Flores, Carlos A. P&eacute;rez and Marco A. Z. Arruda

Abstract: In the present paper, lithium was determined in river sediment using slurry sampling and electrothermal atomic absorption spectrometry (ET AAS) after L'vov platform coating with zirconium (as a permanent chemical modifier). The performance of this modifier and its distribution on the L'vov platform after different heating cycles were evaluated using synchrotron radiation X-ray fluorescence (SRXRF) and imaging scanning electron microscopy (SEM) techniques. The analytical conditions for lithium determination in river sediment slurries were also investigated and the best conditions were obtained employing 1300 and 2300°C for pyrolysis and atomization temperatures, respectively. In addition, 100 mg of sediment samples were prepared using 4.0 mol L-1 HNO3. The Zr-coating permitted lithium determination with good precision and accuracy after 480 heating cycles using the same platform for slurry samples. The sediment samples were collected from five different points of the Cachoeira river, Sao Paulo, Brazil. The detection and quantification limits were, respectively, 0.07 and 0.23 µg L-1.

"Flow-injection Chemiluminescence Determination Of Aminomethylbenzoic Acid And Aminophylline Based On N-bromosuccinimide–luminol Reaction"
Talanta 2004 Volume 62, Issue 3 Pages 611-617
Zhouping Wang, Zhujun Zhang, Zhifeng Fu, Wanfen Luo and Xiao Zhang

Abstract: A novel and sensitive chemiluminescence (CL) method for the determination of aminomethylbenzoic acid and aminophylline coupled with flow-injection analysis (FIA) technique is developed in this paper. It is based on the inhibition effect of the studied drugs on the chemiluminescence emission of N-bromosuccinimide-luminol (NBS-luminol) system. Under the optimum conditions, the decreased CL intensity is linear with the concentration of aminomethylbenzoic acid in the range of 2 x 10^-8 to 1.0 x 10^-6 g mL-1 and with the concentration of aminophylline in the range of 1 x 10^-7 to 7.0 x 10^-6 g mL-1, respectively. The detection limit is 7.0 x 10^-9 g mL-1 for aminomethylbenzoic acid (3s) and 3.4 x 10^-8 g mL-1 for aminophylline (3s). The relative standard deviations (RSD) for 11 parallel measurements of 2.0 x 10^-7 g mL-1 aminomethylbenzoic acid and 1.0 x 10^-6 g mL-1 aminophylline are 2.6 and 3.0%, respectively. The proposed methods have been applied for the determination of the studied drugs in their pharmaceutical formulations with satisfactory results. The possible use of the proposed system for the determination of aminomethylbenzoic acid in plasma sample was also tested. The possible inhibition mechanism of aminomethylbenzoic acid and aminophylline on luminol-NBS system was discussed briefly.

"Automatic On Line Preconcentration And Determination Of Lead In Water By ICP-AES Using A TS-microcolumn"
Talanta 2004 Volume 62, Issue 3 Pages 503-510
M. Zougagh, A. Garc&iacute;a de Torres, E. Vereda Alonso and J. M. Cano Pav&oacute;n

Abstract: A simple, sensitive, low-cost and rapid, flow injection system for the on-line pre-concentration of lead by sorption on a microcolumn packed with silica gel funtionalized with methylthiosalicylate (TS-gel) was developped. The metal is directly retained on the sorbent column and subsequently then eluted from it by EDTA. Five variables (sample flow rate, eluent flow rate, eluent concentration, pH and buffer concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using two level factorial and Box-Behnken designs. The optimum conditions established were applied to the determination of lead by flow injection inductively coupled plasma atomic emission spectrometry (FI-ICP-AES). The proposed method has a linear calibration range from 10 to at least 500 ng mL-1 of lead. At a sample frequency of 24 h-1 and a 120 s pre-concentration time, the enrichment factor was 41, the detection limit was 15.3 ng mL-1 (S/N=3) and the precision, expressed as relative standard deviation, was 0.9% (at 100 ng mL-1). Validation of the developed method was carried out against electrothermal atomic absorption spectrometry analysis without statistically significant differences between the proposed method and the atomic absorption method.

"Electrooxidative Polymerization Of Phenothiazine Derivatives On Screen-printed Carbon Electrode And Its Application To Determine NADH In Flow Injection Analysis System"
Talanta 2004 Volume 62, Issue 3 Pages 477-482
Qiang Gao, Weidong Wang, Ying Ma and Xiurong Yang

Abstract: The electrooxidation polymerization of phenothiazine derivatives, including azure A and toluidine blue O, has been studied at screen-printed carbon electrodes in neutral phosphate buffer. Both compounds yield strongly adsorbed electroactive polymer with reversible behavior and formal potentials closed to 0.04 V at pH 6.9. The modified electrodes exhibited good stability and electrocatalysis for NADH oxidation in phosphate buffer (pH 6.9), with an overpotential of more than 500 mV lower than that of the bare electrodes. Further, the modified screen-printed carbon electrodes were found to be promising as an amperometric detector for the flow injection analysis (FIA) of NADH, typically with a dynamic range of 0.5-100 µM.

"Determination Of Phosphate In Natural Water Employing A Monosegmented Flow System With Simultaneous Multiple Injection"
Talanta 2004 Volume 62, Issue 3 Pages 469-475
Maria Celeste Teixeira Diniz, Orlando Fatibello Filho, Emerson Vidal de Aquino and Jarbas J. R. Rohwedder

Abstract: A monosegmented flow system was employed for the determination of low contents of phosphate in natural water. In this approach, sample and reagents are simultaneously injected to a PTFE reaction coil where the homogenization of the mixture occurs while the monosegment is pumped forwards the photometric detector. The proposed system was evaluated by determining phosphate ion, based on the reaction of association between molybdophosphate and malachite green. It was evaluated individually the best concentration of the reagent solution in relation to blank signal (absorbance of the blank) and the sensitivity of the method. A factorial design was proposed to explain the contribution of each component on the formation of the ion association complex, evaluating the individual contributions as well as the synergistic and antagonistic effects. With the established conditions, phosphorous is determined in the concentration range of 5.0-75 µg P PO43- L-1 (r=0.9992), with a detection limit of 0.70 µg P PO43- L-1 and a relative standard deviation of 2% (20 µg P PO43- l-1, n=8). The proposed method has a sampling frequency of 72 h-1.

"An Improved Flow System For Phenols Determination Exploiting Multicommutation And Long Pathlength Spectrophotometry"
Talanta 2004 Volume 62, Issue 3 Pages 463-467
Eva Curdov&aacute;, Lenka Vavruskov&aacute;, Miloslav Such&aacute;nek, Petr Baldrian and Jir&iacute; Gabriel

Abstract: A greener and sensitive procedure for spectrophotometric determination of phenols based on a multicommuted flow system with a 100 cm optical path flow cell is presented. The method exploited the oxidative coupling of phenolic compounds with 4-aminoantipyrine in alkaline medium containing potassium hexacyanoferrate(III). Sensitivity was 80-fold higher than that achieved with a 1 cm flow cell, making feasible the determination of phenols in the 10^-100?gl-1 range with a detection limit estimated as 1?gl -1 phenol. The sampling rate and the coefficient of variation were estimated as 90 determinations per hour and 0.6% (n=10), respectively. The multicommutation approach allowed a 200-fold reduction of the reagent consumption in comparison with the reference batch method. Moreover, the chloroform extraction for analyte concentration is unnecessary in view of the increase in sensitivity. Recoveries within 93.3 and 106% were achieved for determination of phenol in natural and wastewater samples. Results agreed with the obtained by a reference method at the 95% confidence level. © 2003 Elsevier B.V. All rights reserved.

"On-line Liquid-liquid Extraction System Using A New Phase Separator For Flame Atomic Absorption Spectrometric Determination Of Ultra-trace Cadmium In Natural Waters"
Talanta 2004 Volume 62, Issue 3 Pages 437-443
Aristidis N. Anthemidis, George A. Zachariadis, Charalampos G. Farastelis and John A. Stratis

Abstract: A robust flow injection (FI) on-line liquid-liquid extraction (LLE) pre-concentration/separation system associated with a newly designed gravitational phase separator, coupled to flame atomic absorption spectrometry (FAAS) was developed. The performance of the system was illustrated for cadmium determination at the ?gl-1 level. The non-charged cadmium complex with ammonium pyrrolidine dithiocarbamate (APDC) was extracted on-line into isobutyl methyl ketone (IBMK). The organic phase was effectively separated from a large volume of aqueous phase and is led into a 100?l loop of an injection valve before its introduction into the nebulizer. The system was optimized and offered good performance characteristics with unlimited life time of phase separator, greater flow rate ratios and improved flexibility, as compared with other solvent extraction pre-concentration systems. With a sampling frequency of 33h-1, the enhancement factor was 155, the detection limit was 0.02?gl-1, the relative standard deviation was 3.2% at 2.0?gl-1 Cd concentration level and the calibration curve was linear over the concentration range 0.06-6.0?gl-1. The accuracy of the proposed method was evaluated by analyzing a certified reference material of water and by recovery measurements on spiked samples. Finally, it was successfully applied to the analysis of tapwater, river and seawater samples. © 2003 Elsevier B.V. All rights reserved.

"Improvement Of Analytical Performances For Mercury Speciation By On-line Derivatization, Cryofocussing And Atomic Fluorescence Spectrometry"
Talanta 2004 Volume 62, Issue 2 Pages 433-438
T. Stoichev, R. C. Rodriguez Martin-Doimeadios, E. Tessier, D. Amouroux and O. F. X. Donard

Abstract: A modified automated on-line hyphenated system for simultaneous inorganic ionic mercury (Hg2+) and monomethylmercury (MeHg+) analysis by hydride generation (HG) or ethylation (Eth), cryofocusing, gas chromatography (GC) separation and atomic fluorescence spectrometry (AFS) detection has been improved. Both derivatization methods are investigated with respect to the chromatographic and analytical performances. They can be both affected by interferences when the AFS detection system is used. Water vapor removal using a soda lime moisture trap improves significantly the chromatographic performances, the reproducibility and the detection limits for Hg2+ and MeHg+ analyzed with both methods. For ethylation (Eth) derivatization, a scattering interference generated from low-quality ethylation reagent has also been eliminated. For HG, improved detection limits are 0.13 ng L-1 and 0.01 ng L-1 for Hg2+ and MeHg+, respectively (0.1 l water sample), and reproducibility are 5% for Hg2+ (20 ng l-1) and MeHg+ (5 ng l-1). Improved detection limits for Eth are 0.22 ng g-1 for Hg2+ and 0.02 ng g-1 for MeHg+ (1 g dry sediment sample) and the reproducibility are 5-6% for Hg2+ and MeHg+ (1-2 ng g-1).

"Preparation Of A Soluble Solid Sample By A Continuous Ultrasound Assisted Dissolution System For The Flow-injection Atomic Absorption Spectrometric Determination Of Iron In Milk Powder And Infant Formula"
Talanta 2004 Volume 62, Issue 2 Pages 403-406
M. C. Yebra, A. Moreno-Cid, R. Cesp&oacute;n and S. Cancela

Abstract: A simple and new flow-injection manifold (CUDS) for the continuous ultrasound assisted dissolution of a soluble solid sample coupled to a flow-injection flame atomic absorption spectrometric manifold for the continuous iron determination is described. An experimental design was used for the evaluation of factors involving the CUDS. The method was applied to a certified reference material (CRM-151, 151, skim milk powder) for quality assurance/validation and to real samples (milk powder and infant formulas). The total sampling frequency achieved was 80 samples per hour with a relative standard deviation for the complete procedure of 1.1%. The detection limit was 0.60 ?g g-1 for a sample amount of 30 mg. The results demonstrated that the CUDS is an innovative and efficient tool as compared to the manual-traditional sample preparation methods, but with drastic increase of both sample throughput and precision. © 2003 Elsevier B.V. All rights reserved.

"A Flow System For The Spectrophotometric Determination Of Lead In Different Types Of Waters Using Ion-exchange For Pre-concentration And Elimination Of Interferences"
Talanta 2004 Volume 62, Issue 2 Pages 395-401
Raquel B. R. Mesquita, S&iacute;lvia M. V. Fernandes and Ant&oacute;nio O. S. S. Rangel

Abstract: A flow system for the spectrophotometric determination of lead in natural and waste waters is proposed. The determination is based on the colorimetric reaction between malachite green and iodide, followed by the formation of a ternary complex between those reagents and lead cations. The developed flow system includes a lead pre-concentration step in a column packed with a cationic resin (Chelex 100) operating in a sequential injection mode. To improve the mixture of sample and reagents, a flow injection approach was adopted for the colorimetric determination. This way a hybrid flow system, involving both sequential and flow injection concepts was designed. Another feature of the proposed system is the efficient elimination of major interferent species, such as cadmium and copper. The elimination of cadmium interference is obtained by complexing Cd2+ with chloride and retaining the formed negatively charged complexes in an anionic resin, AG1 X-8. As for copper, with the presence of both ionic resins as well as the conditions for cadmium elimination, it no longer acts as an interferent. Different ranges of lead concentration (50-300 and 300-1000 µg l-1) can be determined with minor changes in the controlling software, useful for application to both natural and waste waters. Therefore, a detection limit of 25 µg L-1 was achieved. Repeatability was evaluated from 10 consecutive determinations being the results better than 4%. The recoveries of lead spikes added to the samples ranged from 93 to 102%. The sampling frequency was 17 and 24 determinations per hour, for 50-300 and 300-1000 µg L-1 ranges, respectively.

"Gas Diffusion-flow Injection Determination Of Total Inorganic Carbon In Water Using Tungsten Oxide Electrode"
Talanta 2004 Volume 62, Issue 2 Pages 389-394
L. Monser, N. Adhoum and S. Sadok

Abstract: A novel gas diffusion-flow injection method has been developed for the rapid and sensitive determination of total inorganic carbon (TIC) in water. The method is based on the diffusion of CO2 across gas permeable membrane from a donor stream containing 0.1 M HCl to an acceptor stream of sodium acetate (10-5 mol L-1 and pH 10). The CO2 trapped in the acceptor stream passes through an electrochemical flow cell contains a tungsten oxide wire and a silver/silver chloride electrode, where it was sensitively detected. The parameters affecting the sensitivity of the electrode such as buffer concentration, pH, flow rate and injected volume were studied in detail. The electrode response was linear in the concentration range from 5 to 100 µg mL-1 CO32- with a correlation coefficient (R2) of 0.998. Precision (RSD) was 1.42% for 20 µg mL-1 standard solution of CO32- (n=10). The detection limit was 0.20 µg mL-1 CO32-. The method was evaluated by the injection of real natural water samples and an average recovery of 100.1% was obtained. The sampling rate was 30 samples h-1. The method is simple, feasible with satisfactory accuracy and precision and thus could be used for monitoring TIC in water.

"Analytical Applications Of A Differential Technique In Laser-induced Fluorimetry: Accurate And Precise Determination Of Uranium In Concentrates And For Designing Microchemielectronic Devices For On-line Determination In Processing Industries"
Talanta 2004 Volume 62, Issue 2 Pages 343-349
D. P. S. Rathore and Manjeet Kumar

Abstract: A novel instrumental technique for the direct, fast, accurate, and precise determination of uranium in concentrates and other U-rich materials (as well as to mineralized rocks) is presented. The proposed technique is an absolute methodology, based on the comparison of the fluorescence of the accurately known standard with a sample of similar but unknown concentration in the low operational range of the instrument (on same sample-dilution basis), by the use of H3PO4-NH4H2PO4 as a fluorescence-enhancing reagent. The relative standard deviation of the proposed technique was 0.5-0.9% (n=9) at 18.1, 36.2, 61.2, and 99.6% U3O8. The proposed technique is suitable for the determination of uranium in samples arising from exploration projects, ores from mining operations, mill process samples, uranium ore concentrates leading to fuel fabrication as well as samples from environmental monitoring containing up to 100% uranium. The results are in good agreement with those obtained by titrimetric, gravimetric, and TBP extraction-H2O2 spectrophotometric methods. The precision of the technique is within the acceptable 'pure geochemistry' type of analysis (RSD ~ 1.0%) and is comparable even those obtained with titrimetric and gravimetric assay. The proposed differential technique coupled with flow injection may open up new advancement in instrumentation leading to design and development of microchemielectronic devices for direct on-line determination, more compatible with the tools of computer age as also to help in handling of radioactive solutions in chemical laboratories in uranium processing industries.

"Flow-injection Chemiluminescent Determination Of Metoclopramide Hydrochloride In Pharmaceutical Formulations And Biological Fluids Using The [Ru(dipy)32+]-permanganate System"
Talanta 2004 Volume 62, Issue 2 Pages 255-263
Nawal. A. Al-Arfaj

Abstract: A flow-injection (FI) methodology using (2,2?-dipyridyl) ruthenium(II) [Ru(dipy)32+] chemiluminescence (CL) was developed for the rapid and sensitive determination of metoclopramide hydrochloride. The method is based on the CL reaction of metoclopramide with Ru(dipy)32+ and KMnO4 in a sulfuric acid medium. Under the optimum conditions, a calibration graph was obtained over the concentration range 0.005-3.5 ?g mL-1 with a limit of detection (S/N = 2) of 1 ng mL-1. The correlation coefficient was 0.99993 (n = 8) with a relative standard deviation of 0.48% for 10 determinations of 1 ?g mL-1 of drug. The method was successfully applied to the determination of metoclopramide in pharmaceutical preparations and biological fluids after IP administration of 25 mg kg-1 dose to rats. The elimination half-life was 2.5 ± 0.4 h. © 2003 Published by Elsevier B.V.

"Determination Of As, Sb, Se, Te And Bi In Milk By Slurry Sampling Hydride Generation Atomic Fluorescence Spectrometry"
Talanta 2004 Volume 62, Issue 1 Pages 173-182
Patricia Cava-Montesinos, M. Luisa Cervera, Agust&iacute;n Pastor and Miguel de la Guardia

Abstract: A simple and fast analytical procedure has been developed for the determination of As, Sb, Se, Te and Bi in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS). Samples were treated with aqua regia for 10 min in an ultrasound water bath and pre-reduced with KBr for total Se and Te determination or with KI and ascorbic acid for total As and Sb, the determination of Bi being possible in all with or without pre-reduction. Slurries of samples, in the presence of antifoam A, were treated with NaBH4 in HCl medium to obtain the corresponding hydrides, and AFS measurements were processed in front of external calibrations prepared and measured in the same way as samples. Results obtained by the developed procedure compare well with those found after microwave-assisted complete digestion of samples. The proposed method is simple and fast, and only 1 mL of milk is needed. The values obtained for detection limit are 2.5, 1.6, 3, 6 and 7 ng L-1 for As, Sb, Se, Te and Bi respectively in the diluted samples, with average relative standard deviation values of 3.8, 3.1, 1.9, 6.4 and 1.2% for three independent analysis of a series of commercially available samples of different origin. Data found in Spanish market samples varied from 3.2±0.3 to 11.3±0.2 ng g-1 As, from 3.1±0.2 to 11.6±0.4 ng g-1 Sb, from 10.7±0.5 to 25.5±0.4 ng g-1 Se, from 0.9±0.2 to 9.4±0.6 ng g-1 Te and from 11.5±0.1 to 27.7±0.4 ng g-1 Bi.

"Flow Injection Catalytic Spectrophotometric Simultaneous Determination Of Nitrite And Nitrate"
Talanta 2004 Volume 62, Issue 1 Pages 97-101
Xuan-Feng Yue, Zhi-Qi Zhang and Hong-Tao Yan

Abstract: A new flow injection catalytic spectrophotometric method is proposed for the simultaneous determination of nitrite and nitrate based on the catalytic effect of nitrite on the redox reaction between crystal violet and potassium bromate in phosphoric acid medium and nitrate being on-line reduced to nitrite with a cadmium-coated zinc reduction column. The redox reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of crystal violet at the maximum absorption wavelength of 610 nm. A technique of inserting a reduction column into sampling loop is adopted and the flow injection system produces a signal with a shoulder. The height of shoulder in the ascending part of the peak corresponds to the nitrite concentration and the maximum of the peak corresponds to nitrate plus nitrite. The detection limits are 0.3 ng mL-1 for nitrite and 1.0 ng mL-1 for the nitrate. Up to 32 samples can be analyzed per hour with a relative standard deviation of less than 2%. The method has been successfully applied for the simultaneous determination of nitrite and nitrate in natural waters.

"Application Of Flowing-stream Techniques To Water Analysis: Part II. General Quality Parameters And Anionic Compounds: Halogenated, Sulphur And Metalloid Species"
Talanta 2004 Volume 62, Issue 1 Pages 1-15
Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: In the first part of this review [Talanta 60 (2000) 867], flowing-stream methods (namely, segmented flow analysis (SFA), continuous-flow analysis (CFA), flow-injection analysis (FIA), sequential-injection analysis (SIA), multicommuted flow-injection analysis (MCFIA) and multisyringe flow-injection analysis (MSFIA)) were presented as powerful analytical tools for nutrient determination in water samples when coupled to photometric/fluorimetric detection, flow-through ion-selective electrodes or amperometric sensors. In the present paper, relevant flow methods applied to the monitoring of anionic species as well as to the determination of general parameters for water quality evaluation (such as pH, alkalinity, chemical and biochemical oxygen demand, conductivity and total ionic content) are reviewed, and their background, detection technique and noteworthy analytical features are detailed. Furthermore, other techniques, such as flow systems connected to hydride-generation atomic absorption spectrometry, should be highlighted as practical approaches for metalloid determination since a series of speciation schemes are demonstrated to be readily adaptable.
Review Multisyringe Multicommutation Sequential injection

"On-line Preconcentration Of Phosphate Onto Molybdate Form Anion Exchange Column"
Talanta 2003 Volume 61, Issue 6 Pages 905-912
Tetsuyuki Taniai, Masaaki Sukegawa, Akio Sakuragawa and Atsushi Uzawa

Abstract: In this paper, we describe an automated flow injection system for measuring the concentration of phosphate based on a fluorescence quenching reaction between Rhoadamine 6G and phosphomolybdate with a pre-concentration column, which was packed with a molybdate-form ion exchange resin to collect and pre-concentrate the phosphate in the sample solution. Rhodamine 6G was chosen because the reaction with phosphomolybdate was fast and did not require heat. For the construction of a stable flow injection system, an aqueous methanol solution was used as the cleaning reagent to overcome the precipitation of ion-associated complexes between Rhodamine 6G and phosphomolybdate or Rhodamine 6G and molybdate. For the pre-concentration and collection of the phosphate ions in a water sample, a pre-concentration column, which was packed with a molybdate-form ion exchange resin, was combined with the proposed flow injection system and applied to natural water samples containing low concentrations of phosphate.

"Diffusion Layer Titration Of Dipyrone In Pharmaceuticals At A Dual-band Electrochemical Cell"
Talanta 2003 Volume 61, Issue 5 Pages 725-732
Thiago R. L. C. Paix&atilde;o, Renato Camargo Matos and Mauro Bertotti

Abstract: This paper describes the use of a thin-layered dual-band electrochemical cell operating at flow conditions to determine dipyrone (sodium salt of 1-phenil-2,3-dimethyl-4-methylaminomethanesulfonate-5-pyrazolone) by reaction with electrogenerated iodine. The electrolytic cell consisted of two closely spaced gold electrodes, the upper stream electrode serving as the generator electrode and the downstream electrode working as the collector electrode. A linear dynamic range from 2 to 15 µmol L-1 dipyrone was obtained by using a sample volume of 100 µl, with a detection limit of 1.1 µmol l-1. Standard deviation (S.D.) of 3.4% for 20 repetitive injections of a 40 µmol L-1 dipyrone solution and sampling frequency of 90 h-1 were achieved. The results obtained with the thin-layered dual-band electrochemical cell for dipyrone determination in three different pharmaceutical samples compared well with those found by iodimetry with coulometrically generated iodine.

"Reduction Of Mercury(II) By Tropical River Humic Substances (Rio Negro)--Part II. Influence Of Structural Features (molecular Size, Aromaticity, Phenolic Groups, Organically Bound Sulfur)"
Talanta 2003 Volume 61, Issue 5 Pages 699-707
Julio Cesar Rocha, &Eacute;zio Sargentini, Jr, Luiz Fabricio Zara, Andr&eacute; Henrique Rosa, Ademir dos Santos and Peter Burba

Abstract: The influence of structural features of tropical river humic substances (HS) on their capability to reduce mercury(II) in aqueous solutions was studied. The HS investigated were conventionally isolated from Rio Negro water-Amazonas State/Brazil by means of the collector XAD 8. In addition, the isolated HS were on-line fractionated by tangential-flow multistage ultrafiltration (nominal molecular-weight cut-offs: 100, 50, 30, 10, 5 kDa) and characterized by potentiometry and UV/VIS spectroscopy. The reduction of Hg(II) ions to elemental Hg by size-fractions of Rio Negro HS was assessed by cold-vapor AAS (CVAAS). UV/VIS spectrometry revealed that the fractions of high molecular-size (F1>100 kDa and F2: 50-100 kDa) have a higher aromaticity compared to the fractions of small molecular-size (F5: 5-10 kDa, F6: t1/2 of I: 160 min, t1/2 of II: 300 min) weakly influenced by the molecular-size, in contrast to the differing degree of Hg(II) reduction (F5>F2>>F1>F3>F4>>F6). Accordingly, Hg(II) ions were preferably reduced by HS molecules having a relatively high ratio of phenolic/carboxylic groups and a small concentration of sulfur. From these results a complex 'competition' between reduction and complexation of mercury(II) by aquatic HS occurring in tropical rivers such as the Rio Negro can be suggested.

"Hydride Generation Atomic Absorption Spectrometry With Different Flow Systems And In-atomizer Trapping For Determination Of Cadmium In Water And Urine--overview Of Existing Data On Cadmium Vapour Generation And Evaluation Of Critical Parameters"
Talanta 2003 Volume 61, Issue 5 Pages 683-698
Leonardo Lampugnani, Claudia Salvetti and Dimiter L. Tsalev

Abstract: An overview of literature data on vapor generation techniques for cadmium and comparison with own experiments by means of several different types of hydride generation-electrothermal atomic absorption spectrometric systems (HG-ETAAS) (batch, semi-batch (SB), continuous-flow (CF) and flow-injection (FI) as well as different gas-liquid separators (GLS) exhibits apparent variations and inconsistency. However, if data for optimal chemical conditions are re-plotted in another coordinates: CHCl (mol l-1) vs. the ratio of reductant-to-acid molar input rates (i.e. millimoles per minute), [BH4-]:[H+], much better consistency of data is revealed: more than half of data are clustered around 0.2-0.3 mol L-1 HCl which appears an optimal acidity at moderate BH4- concentrations; the tetrahydroborate molar input rates should always be in excess versus the H+ molar input rates (1.1 to tenfold); relatively high flow rates of argon purge gas are required (≥120 mL min-1); special attention to the blank control at ng L-1 levels as well as to the construction of gas-liquid separator and vapor transfer lines should be paid. 'Milder' conditions for HG could be provided with some of the examined systems and GLSs, thus minimizing reagent consumption, blanks, vigorous reactions, foaming, aerosol production and drift in measurements: e.g. 0.4 mol L-1 HCl-3% (m/v) NaBH4 with the semi-batch system and 0.25 mol L-1 HCl-2% (m/v) NaBH4 in continuous flow mode. Experimental system is based on the Transversely Heated Graphite Atomizer coupled with flow injection system FIAS 400. Integrated platforms are treated for permanent modification with Zr (110 µg) or W (240 µg) and then with Ir (8 µg). Temperatures of trapping, pyrolysis and atomization are 350, 500 and 1300°C, respectively. The best overall efficiency of HG, transportation and trapping is 41%. The characteristic mass for peak area measurements is mo=2.8 pg and the limit of detection is 0.002 µg l-1. The long-term stability of characteristic mass (within-day, 8 h) is mo=2.8±0.1 pg (RSD 4.0%, n=8), whereas the corresponding between-day figures (1 mo) are mo=2.8±0.2 pg (RSD 6.6%, n=6). The linear range is 0.002-0.12 µg L-1 with a sample loop of 1.8 ml, being strongly impaired with smaller sample volumes in FI mode. The sample throughput rate is 10 h-1 with the semi-batch system. Applications to real human and bovine urine samples and CRMs of sea water (CASS-3), river water (SLRS-1 and SLRS-3) and urine (SRM 2670) are presented.

"Synthesis And Application Of A Functionalized Resin In On-line System For Copper Preconcentration And Determination In Foods By Flame Atomic Absorption Spectrometry"
Talanta 2003 Volume 61, Issue 5 Pages 675-682
Valfredo Azevedo Lemos, Patr&iacute;cia Xavier Baliza, Regina Terumi Yamaki, Marcelo E&ccedil;a Rocha and Ana Paula Oliveira Alves

Abstract: An on-line system for pre-concentration and determination of copper at µg L-1 level by flame atomic absorption spectrometry (FAAS) is proposed. Amberlite XAD-2 functionalized with 3,4-dihydroxybenzoic acid packed in a minicolumn was used as sorbent. Copper(II) ions were sorbed in the minicolumn, from which it could be eluted by hydrochloric acid solution directly to the nebulizer-burner system of the FAAS. Eluent solution was carried by water at a flow rate of 5.00 mL min-1. Signals were measured as peak height by using an instrument software. Achieved sampling rate was 27 samples per hour. Analytical parameters were evaluated and the results demonstrated that copper can be determined, with acetate buffer to adjust the sample pH at 6.0, pre-concentration time of 120 s and a sample flow rate of 6.50 mL min-1. The desorption was carried out with 30 µl of a 1.0 mol L-1 hydrochloric acid solution. An enrichment factor of 33 in 13.00 mL of sample (120 s pre-concentration time) was achieved by using the time-based technique. The detection limit (DL) (3 s) was 0.27 µg L-1 and the precision (assessed as the relative standard deviation) reached values of 5.7-1.1% in copper solutions of 5.00 to 50.00 µg L-1 concentration, respectively. The accuracy of procedure was confirmed by copper determination in certified reference materials. Recoveries of spike additions (1.0 or 2.0 µg g-1) to food samples were quantitative (90.0-110.0%). These results proved also that the procedure is not affected by matrix interference and can be applied satisfactorily for copper determination in rice flour and starch samples.

"Miniature Flow-injection Analysis Manifold Created By Micromilling"
Talanta 2003 Volume 61, Issue 5 Pages 659-665
Andrea Rainelli, Richard Stratz, Karin Schweizer and Peter C. Hauser

Abstract: The miniature flow injection analysis (µFIA) system is based on a mechanically engraved manifold in a PMMA-substrate. The channels have a trapezoidal cross-section with a depth of 150 µm and a width between 180 and 360 µm and the reactor volume is 3.75 µl. A light-emitting diode (LED) is used as radiation source for absorbance detection and optical fibers are used for transmitting light to and from the manifold. Computer controlled valves are used for directing the liquid flows maintained with syringe pumps. A sampling rate of approximately five determinations per minute was achieved with a reagent consumption of 10 µl min-1. Four applications were implemented and tested; the performance was found to be comparable to that obtained with conventional FIA-set-ups despite the drastically reduced optical pathlength. Electrokinetic pumping was extensively evaluated but found to generally be very restricted in scope because the reagent solutions cannot usually be adapted to the requirements for generating the flow.

"Chemiluminescence System For Automatic Determination Of Chemical Oxygen Demand Using Flow Injection Analysis"
Talanta 2003 Volume 61, Issue 5 Pages 651-658
Baoxin Li, Zhujun Zhang, Juan Wang and Chunli Xu

Abstract: A novel chemiluminescence (CL) system for automatic determination of chemical oxygen demand (COD) combined with flow injection analysis is proposed in this paper. In this system, potassium permanganate is reduced to Mn2+ which is first adsorbed on a strongly acid cation-exchange resin mini-column to be concentrated during chemical oxidation of the organic compounds at room temperature, while the excessive MnO4- passes through the mini-column to be waste, then the concentrated Mn2+ is eluted reversely and measured by the luminol-H2O2 CL system. The calibration graph is linear in the range of 4-4000 mg L-1 and the detection limit is 2 mg l-1. A complete analysis could be performed in 1.5 min including washing and sampling, giving a throughout of about 40 h-1. The relative standard deviation was 4.4% for 10 mg L-1 COD (n=11), 4.8% for 100 mg L-1 COD (n=11). This CL flow system for determination of COD is very simple, rapid and suitable for automatic and continuous analysis. The presented system has been applied successfully to the determination of COD of water samples.

"Bismuth Determination In Environmental Samples By Hydride Generation-electrothermal Atomic Absorption Spectrometry"
Talanta 2003 Volume 61, Issue 5 Pages 633-642
Carmen Moscoso-P&eacute;rez, Jorge Moreda-Pi&ntilde;eiro, Purificaci&oacute;n L&oacute;pez-Mah&iacute;a, Soledad Muniategui-Lorenzo, Esther Fern&aacute;ndez-Fern&aacute;ndez and Dar&iacute;o Prada-Rodr&iacute;guez

Abstract: A hydride generation procedure, via flow injection, coupled to electrothermal atomic absorption spectrometry was optimized for Bi determination in sea water and hot-spring water and acid extracts from coal, coal fly ash and slag samples. The effects of several variables such as hydrochloric acid and sodium tetrahydroborate concentrations, hydrochloric acid and sodium tetrahydroborate flow rates, reaction coil length, trapping and atomisation temperatures, trapping time and the Ar flow rate have been investigated by using a 29*3/128 Plackett-Burman design. From these studies, certain variables (sodium tetrahydroborate concentration and trapping time) showed up as significant, and they were optimized by a 22+star central composite design. In addition, a study of the bismuthine trapping and atomisation efficiency from graphite tubes (GTs) permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide and tantalum carbide were investigated. The results obtained were compared with those achieved by iridium and zirconium-treated GTs. The best analytical performances, with characteristic mass of 35 pg and detection limit of 70 ng l-1, were achieved by using U-treated GTs. Accuracy were checked using several reference materials: 1643d (Trace Elements in Water), TM-24 (Reference Water), GBW-07401 (Soil) and 1632 c (Trace Elements in Coal).

"The Use Of 2-2-thiazolylazo-p-cresol To Minimize The Interference Of Ni And Cu For The Bismuth Determination In Alloys By Hydride Generation Atomic Absorption Spectrometry"
Talanta 2003 Volume 61, Issue 5 Pages 597-602
Iracema Takase, Aderval S. Luna and Reinaldo Calixto de Campos

Abstract: Thiazolylazo p-cresol (TAC) was studied as a masking agent for the determination of Bi in rich Ni and Cu alloys by hydride generation atomic absorption spectrometry (HGAAS). In the presence of TAC, Bi/Ni and Bi/Cu ratios up to 1:160000 and 1:16000, respectively, were found to be tolerable. No buffering was necessary once the masking agent was effective even in very acid medium. Limits of detection at the low µg g-1 range were reached and the accuracy of the procedure was confirmed by the good concordance between found and certified values in the analysis of certified reference materials (CRM).

"Characterization And Application Of Humic Acid Modified Carbon Electrodes"
Talanta 2003 Volume 61, Issue 4 Pages 547-556
Carlos D. Garc&iacute;a and Patricia I. Ortiz

Abstract: Four routes for the modification of carbon electrodes with humic acids and the determination of three divalent metallic cations were studied. The determination of bound Fe2+, Cu2+ and Ni2+ was performed by cyclic and square wave voltammetry using either a batch or flow analysis system. Using the FIA system and SWV, linear relationships between the oxidation (or reduction) current and the cations concentration were obtained with the modified electrodes, while no signals were obtained for the same conditions for bare carbon electrodes. The system can be used to study the interaction between a wide range of electroactive cations and humic substances; however, the performance as an analytical tool is limited due to the high limits of detection (µM). However, some advantages like simplicity, short analysis time, inexpensive instrumentation needs and miniaturization capabilities are remarkable.

"Ozone Treatment For Mercury Determination In White Wines"
Talanta 2003 Volume 61, Issue 4 Pages 485-491
J. L. Capelo, H. A. Pedro and A. M. Mota

Abstract: A method was developed for the generation of mercury vapor by means of cold-vapor flow-injection atomic absorption spectrometry (FI-CV-AAS) from white wine samples after ozonation as sample pre-treatment. Two different reactors designs for sample ozonation were developed and investigated. The limit of detection and the limit of quantification were, respectively, 0.5 and 1.7 µg l-1, and the relative standard deviation (n=10) was 2% for a concentration of 50 µg L-1 and 7% for a concentration of 5 µg l-1. The pre-treatment with ozone has allowed to reduce drastically the amount of chemical reagents (e.g. carrier agent and reducing agent) used in the FI-CV-AAS system. The mercury content of wine samples was also determined by FI-CV-AAS after pre-concentration in the presence of HNO3 and H2O2. In general, there was no significant difference among data obtained from both methodologies, but pre-treatment with ozone is much faster.

"Flow-injection Analysis Of Two Fluoquinolones By The Sensitizing Effect Of Terbium(III) On Chemiluminescence Of The Potassium Permanganate–sodium Sulfite System"
Talanta 2003 Volume 61, Issue 3 Pages 403-409
Lin Yi, Huichun Zhao, Shilv Chen, Linpei Jin, Dongdong Zheng and Zhenglong Wu

Abstract: A simple, rapid and sensitive method for the determination of two fluoquinolones (FQs), enoxacin (ENX) and ofloxacin (OFLX) is described by using flow injection analysis with potassium permanganate-sodium sulfite chemiluminescence detection. The calibration graphs for ENX and OFLX are linear in the range of 8.0 x 10^-10-1.0 x 10^-5 and 1.0 x 10^-9-1.0 x 10^-6 mol l-1, respectively. The 3s limits of detection are 2.4 x 10^-10 mol L-1 for ENX and 5.6 x 10^-10 mol L-1 for OFLX. The method is applied satisfactorily to the determination of the two FQs in dosage form and urine sample. The possible mechanism is also proposed.

"Optimization Of The Electrodeposition Of Copper On Poly-1-naphthylamine For The Amperometric Detection Of Carbohydrates In HPLC"
Talanta 2003 Volume 61, Issue 3 Pages 341-352
Fabiana D'Eramo, Juan M. Marioli, Alejandro H. Ar&eacute;valo and Leonides E. Sereno

Abstract: A modified electrode consisting of copper dispersed in a poly-1-naphthylamine (p-1-NAP/Cu) film on a glassy carbon electrode was used as an amperometric detector for the on-line analysis of various carbohydrates separated by high performance liquid chromatography. The results obtained with this new sensor were compared to those obtained with a modified electrode based on the same polymer but with copper ions incorporated at open circuit, as described in a previous paper. In this new modified electrode the copper microparticles were electrochemically deposited into the polymeric matrix by single potential step chronoamperometry. A nucleation and growth mechanism was proposed to explain the current transients of copper electrodeposition. The experimental results were fitted to the proposed mechanism by using a mathematical equation that considers three-dimensional growth and progressive nucleation, assuming a no overlap and no diffusion mechanism. Cyclic voltammetric experiments showed that the electrodeposited copper microparticles provided a catalytic surface suited for the oxidation of glucose and several carbohydrates. The sensitivity of the electrode was influenced by the amount of copper electrodeposited, which in turn depended on the applied overpotential used for the deposition of copper. Liquid chromatographic experiments were carried out to test the analytical performance of these electrodes for the determination of various carbohydrates.

"X-ray Fluorescence Determination Of As, Bi, Co, Cu, Fe, Ni, Pb, Se, V And Zn In Natural Water And Soil Extracts After Preconcentration Of Their Pyrrolidinedithiocarbamates On Cellulose Filters"
Talanta 2003 Volume 61, Issue 3 Pages 315-329
V. P. Gordeeva, M. A. Statkus, G. I. Tsysin and Yu. A. Zolotov

Abstract: A simple method for the elements pre-concentration on thin-layer paraffin-treated cellulose filters was proposed. It was found that pyrrolydinedithiocarbamates of As(III), Bi, Cd, Co, Cu, Fe(III), Ni, Pb, Se(IV), V(V) and Zn obtained after mixing of sample (3-5 mL min-1) and reagent (0.7-1.0 mL min-1) streams were quantitatively recovered from 100 mL sample. The sample acidity was adjusted to pH 4.8-5.2 for pre-concentration of Cd, Co, Cu, Fe(III), Ni, Pb, V(V) and Zn, and to 2 M HCl for pre-concentration of As, Bi and Se. The optimum reagent concentration was found to be 0.1%. The elements were determined on the filters by X-ray fluorescence spectrometry. The detection limits achieved were 0.1-4.0 µg of element on the filter. Relative standard deviation (RSD) was not higher than 0.08 while determining 5-50 µg of elements on filter. Accuracy and precision of the technique proposed were evaluated by the analysis of spiked natural samples.

"A Sequential Injection Spectrophotometric Method For The Determination Of Penicillamine In Pharmaceutical Products By Complexation With Iron(III) In Acidic Media"
Talanta 2003 Volume 61, Issue 2 Pages 221-231
Fakhr Eldin O. Suliman, Haider A. J. Al-Lawati, Salma M. Z. Al-Kindy, Imad Eldin M. Nour and Salama B. Salama

Abstract: A simple, robust and sensitive sequential injection spectrophotometric method for the assay of penicillamine (PA) in pharmaceutical formulations is developed. The method was based on the complex formation when PA is reacted with iron(III) solution in hydrochloric acid media. The deep blue colored PA-iron(III) complex produced is monitored at a maximum wavelength of 600 nm. A five level orthogonal array design coupled to genetic algorithm was employed to obtain the optimum experimental conditions for the determination of PA using peak absorbance as the measure of the system's performance criterion. A linear dynamic range for the determination of PA of 25-300 ppm was obtained with a sampling frequency of 50 h-1 and a relative standard deviation of less than 0.98%. The method was successfully applied to the determination of PA in pharmaceutical formulations.

"Flow-injection Spectrophotometry Of Vanadium By Catalysis Of The Bromate Oxidation Of N,N'-bis(2-hydroxyl-3-sulfopropyl)-tolidine"
Talanta 2003 Volume 61, Issue 2 Pages 203-210
Shigenori Nakano, Erina Tanaka and Yukino Mizutani

Abstract: A highly sensitive flow-injection method is proposed for the catalytic determination of vanadium(V) at sub-nanogram per milliliter levels using a new indicator reaction. The method is based on the catalytic effect of vanadium(V) on the bromate oxidation of N,N'-bis(2-hydroxyl-3-sulfopropyl)-tolidine. 1,2-Dihydroxybenzene-3,5-disulfonate was used as an activator in the vanadium(V)-catalyzed reaction and significantly enhanced the sensitivity of the method. Vanadium(V) in the range 0.01-3.0 ng mL-1 was easily determined with sampling rate of about 30 h-1. Vanadium(IV) could be also determined. The limit of detection (S/N=3) was 0.008 ng mL-1 and the relative standard deviations were 1.4 and 1.6% for ten determinations of 0.2 ng mL-1 vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the addition of ethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples.

"Solid-phase Iodine As An Oxidant In Flow Injection Analysis: Determination Of Ascorbic Acid In Pharmaceuticals And Foods By Background Correction"
Talanta 2003 Volume 61, Issue 2 Pages 173-179
Meissam Noroozifar and Mozhgan Khorasani-Motlagh

Abstract: A flow injection analysis (FIA)-background correction method comprising two solid-phase reactors and spectrophotometry for determination of ascorbic acid (AsA) is proposed. A polyethylene mini-column filled with solid iodine (30% m/m suspended on silica gel beads), reactor 1, and other column filled only with silica gel, reactor 2, which are then incorporated in a flow system so that solid iodine reagent in reactor 1 is affected as the sample passes through the column. The sample blank is produced by the oxidation of the AsA by iodine to form dehydroascorbic acid, insensitive to ultraviolet at 267 nm. AsA in samples is determined after injected in reactor 2; the difference in two analytical signal observed is related to amount of AsA. The linear range of the system is up to 50 µg mL-1 with a detection limit of 0.08 µg mL-1, RSD of better than 1.0% and sampling frequency of 110 sample h-1. The method is successfully applied to the determination of AsA in pharmaceuticals and foods.

"Novel Flow Injection-fluorometric Method For The Determination Of Trace Silicate And Its Application To Ultrapurified Water Analysis"
Talanta 2003 Volume 60, Issue 6 Pages 1277-1285
Akhmad Sabarudin, Mitsuko Oshima, Naoe Ishii and Shoji Motomizu

Abstract: A highly sensitive fluorescence quenching method for the determination of silicate based on the formation of an ion associate between molybdosilicate and Rhodamine B (RB) in nitric acid medium was developed. A flow injection system coupled with a fluorescence detector was used for the measurement of fluorescence intensity at 560 and 580 nm as excitation and emission wavelengths, respectively. The calibration graph for Si showed a linear range of 0.1-5 ng mL-1 with correlation coefficient of 0.9999, and the detection limit of 0.06 ng mL-1. The proposed method was successfully applied to the determination of silicate in ultrapurified water with satisfactory results.

"Determination Of Ammonia In Beers By Pervaporation Flow Injection Analysis And Spectrophotometric Detection"
Talanta 2003 Volume 60, Issue 6 Pages 1269-1275
Lijuan Wang, Terence J. Cardwell, Robert W. Cattrall, Maria D. Luque de Castro and Spas D. Kolev

Abstract: A pervaporation flow injection (PFI) method is described for the determination of ammonia in beers. After injecting the sample into a NaOH donor solution, ammonia and other volatiles are transferred in the pervaporation unit from the donor stream to an acceptor stream containing sodium salicylate and nitroprusside, which subsequently mixes with alkaline sodium dichloroisocyanurate to allow the classical Berthelot reaction to take place. The blue-colored complex formed is monitored spectrophotometrically at 655 nm. A linear calibration curve with a range of 0.1-40 mg L-1 was obtained. The method has a detection limit of 0.05 mg L-1 and is capable of a sampling frequency of 11 h-1 at 4 mg L-1 ammonia. It was applied successfully to the determination of ammonia in synthetic samples and unfiltered lager beers. The advantages of the present method over the ammonia ion-selective electrode method and the PFI system based on mixed indicator detection are discussed.

"Determination Of Phosphate In Hydroponic Nutrient Solutions Using Flow Injection Potentiometry And A Cobalt-wire Phosphate Ion-selective Electrode"
Talanta 2003 Volume 60, Issue 6 Pages 1215-1221
Roland De Marco and Cam Phan

Abstract: The direct flow injection potentiometric (FIP) analysis of phosphate in hydroponic nutrient solution has been carried out using a cobalt-wire ion-selective electrode (ISE). Synthetic hydroponic nutrient solution, commercial hydroponic nutrient solution and working hydroponic farm nutrient solution were analyzed for phosphate using the FIP technique. It is shown that FIP results compare favourably to standard methods of analysis such as spectrophotometry and indirect photometric ion-pair chromatography. Reproducible FIP response curves with a slope of -(47.57±0.03) mV per decade and intercept of -(169.7±0.1) mV were obtained for four separate calibrations in the concentration range 5.0 x 10^-4-1.0 x 10^-2 M H2PO4-. Anion corrections for interferences by Cl-, NO3- and SO42- were applied to all samples using the selectivity coefficients determined independently using a fixed interference method. Nevertheless, it was found that anion corrections were not necessary, as the deviations fell within the bounds of experimental error for the cobalt-wire ISE technique (i.e.±2-5% RSD). The proposed FIP method enables the direct determination of phosphate in hydroponic nutrient solutions.

"A Simple Flow Injection-reduced Volume Column System For Hemoglobin Typing"
Talanta 2003 Volume 60, Issue 6 Pages 1163-1170
Boonraksa Srisawang, Prachya Kongtawelert, Supaporn Kradtap Hartwell, Jaroon Jakmunee and Kate Grudpan

Abstract: A flow injection (FI)-reduced volume column system was developed for hemoglobin (Hb) typing to be used as an initial screening method for thalassemia. The column was packed with 140 µl diethylaminoethyl (DEAE)-Sephadex A-50 ion exchange beads. Hb can be separated using Tris-HCl buffer solution with pH gradient 8.5-6.5 and then monitored spectrophotometrically at 415 nm. The hemolysate of 40 blood samples from packed red cells were screened for thalassemia by determining the amount of HbA2 and HbE present. The proposed system was able to predict positive test results from those samples with β, E-trait and EE homozygous thalassemia, Hb types that were independently identified following the conventional method at the hospital laboratory. Advantages of the proposed system over the conventional column technique include low amount of reagents and blood sample needed, short analysis time and low cost. Each analysis required only 80 µl of 50 times diluted packed cells, which is equivalent to 1.6 µl undiluted packed cells, and it can be completed in only 35 min. This simple FI-reduced volume column system was demonstrated to be an economic alternative system for Hb typing to initially screen some types of thalassemia such as β-trait, E-trait and EE-homozygous which are commonly found in Thailand.

"The Use Of Silica-immobilized Brown Alga (Pilayella Littoralis) For Metal Preconcentration And Determination By Inductively Coupled Plasma Optical Emission Spectrometry"
Talanta 2003 Volume 60, Issue 6 Pages 1131-1140
Elma Neide V. M. Carrilho, Joaquim A. N&oacute;brega and Thomas R. Gilbert

Abstract: The brown alga Pilayella littoralis was used as a new biosorbent in an on-line metal pre-concentration procedure in a flow-injection system. Al, Co, Cu and Fe were determined in lake water samples by inductively coupled plasma optical emission spectrometry (ICP-OES) after pre-concentration in a silica-immobilized alga column. Like other algae, P. littoralis exhibited strong affinity for these metals proving to be an effective accumulation medium. Metals were bound at pH 5.5 and were displaced at pH<2 with diluted HCl. The enrichment factors for Cu(II), Fe(III), Al(III) and Co(II) were 13, 7, 16 and 11, respectively. Metal sorption efficiency ranged from 86 to 90%. The method accuracy was assessed by using drinking water certified reference material and graphite furnace atomic absorption spectrometry (GFAAS) as a comparison technique. The column procedure allowed a less time consuming, easy regeneration of the biomaterial and rigidity of the alga provided by its immobilization on silica gel.

"Selective Pre-concentration Of Selenite From Aqueous Samples Using Mercapto-silica"
Talanta 2003 Volume 60, Issue 5 Pages 1003-1009
Feyime Sahin, M&uuml;rvet Volkan, Alan G. Howard and O. Yavuz Ataman

Abstract: Silica gel modified with 3-mercaptopropyl-trimethoxysilane was used for the selective separation and pre-concentration of selenite (Se(IV)) from aqueous solutions containing Se(IV) and selenate (Se(VI)). Over a wide range of acidity, from 2 mol L-1 HCl to pH 9.00, Se(IV) was taken up by the mercaptopropyl-silica with nearly 100% efficiency; Se(VI) however was unretained. Se(IV) content was determined by hydride generation atomic absorption spectrometry (HGAAS), following batch release of the selenium from the pre-concentration medium by acidic periodate. The overall pre-concentration efficiency, including both take-up and elution, in the range of 89-106%. The method was applied to spiked seawater samples containing as low as 800 ng L-1 Se in selenite form. This solid-phase extraction system offers several major advantages over conventional solvent extraction procedures. It firstly exhibits high selectivity for Se(IV) over Se(VI). Using the solid-phase media, pre-concentration of Se(IV) in dilute water samples can be carried out in the field, stabilizing the selenite-selenium in a convenient form for transport and storage. In addition, selenium stored on silica is derived solely from Se(IV) overcoming problems of selenium redox speciation changes and loss during storage.

"Gallium Trace On-line Preconcentration/separation And Determination Using A Polyurethane Foam Mini-column And Flame Atomic Absorption Spectrometry.: Application In Aluminum Alloys, Natural Waters And Urine"
Talanta 2003 Volume 60, Issue 5 Pages 929-936
Aristidis N. Anthemidis, George A. Zachariadis and John A. Stratis

Abstract: A sensitive and selective flow injection time-based method for on-line pre-concentration/separation and determination of gallium by flame atomic absorption spectrometry at trace levels was developed. The on-line formed gallium chloride complex is sorbed onto a polyether-type polyurethane foam mini-column, followed by on-line quantitative elution with isobutyl methyl ketone and direct introduction into the flame pneumatic nebulizer of the atomic absorption spectrometer. All chemical and flow variables of the system as well as the possible interferences were studied. The manner of strong HCl solutions propulsion was investigated and established using a combination of two displacement bottles. For 90 s pre-concentration time, a sample frequency of 28 h-1, an enhancement factor of 40, a detection limit of 6 µg L-1 and a precision expressed as relative standard deviation (sr) of 3.3% (at 1.00 mg l-1) were achieved. The calibration curve is linear over the concentration range 0.02-3.00 mg l-1. The accuracy of the developed method was sufficient and evaluated by the analysis of a silicon-aluminum alloy standard reference material. Finally, it was successfully applied to gallium determination in commercial aluminum alloys, natural waters and urine.

"Application Of Flowing Stream Techniques To Water Analysis. Part I. Ionic Species: Dissolved Inorganic Carbon, Nutrients And Related Compounds"
Talanta 2003 Volume 60, Issue 5 Pages 867-886
Manuel Mir&oacute;, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: This paper summarizes the most relevant manuscripts issued from 1990 to date referred to water analysis using flowing stream techniques. Concretely, reported flow methods applied to the determination or monitoring of inorganic analytes (viz. carbon, nitrogen, phosphorous and silicon species) together with some related compounds to assess water quality in drinking, rain, underground, marine, river, estuarine, waste and industrial samples are reviewed. For the first time, the most widespread flow techniques of analysis described in the literature (viz. segmented flow analysis (SFA), continuous flow analysis (CFA), flow injection analysis (FIA), sequential injection analysis (SIA), multicommuted FIA (MCFIA), multisyringe FIA (MSFIA), along with the different exploited injection modalities are included in the same review.
Review Multicommutation Multisyringe

"A Simple And Selective Flow-injection Spectrophotometric Determination Of Copper(II) By Using Acetylsalicylhydroxamic Acid"
Talanta 2003 Volume 60, Issue 4 Pages 861-866