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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Optimization

Classification: Feature -> Optimization

Citations 1069

"Comparison Of The Maximum Sensitivity Of Different Flow Injection Manifold Configurations: Alternating Variable Search Optimization Of The Iron(II)/1,10-phenanthroline System"
Anal. Chem. 1994 Volume 66, Issue 5 Pages 660-666
Stuart J. Chalk and Julian F. Tyson

Abstract: Flow rate, injected volume, manifold length and reagent concentration were studied with single, double and reverse single-line flow injection manifolds (illustrated) for the spectrophotometric determination of Fe(II) complexed with 1,10-phenanthroline. The three flow injection configurations were of comparable sensitivity, although the reverse configuration sensitivity was slightly higher than the other two. All manifolds exhibited maximum sensitivity when the dispersion coefficient (measured from the product profile) was 1.1. The lowest detection limit for Fe (10 ng/l) was obtained with the double-line configuration, due to the absence of I peaks.
Iron(II) 1,10-phenanthroline Spectrophotometry

"Spectrophotometric And Spectrofluorimetric Determination Of Famotidine And Ranitidine Using 1,4-benzoquinone Reagent"
Anal. Lett. 1999 Volume 32, Issue 7 Pages 1403-1419
Abdel Kader S. Ahmad; M. Abdel Kawy; M. Nebsen

Abstract: Spectrophotometric and spectrofluorimetric methods were adopted for the analysis of Famotidine and Ranitidine depending on their reaction with 1,4 Benzoquinone reagent at pH 5.2 and 5.6, respectively. The absorbances of the resulting condensation products were measured at 502 and 508 nm for Famotidine and Ranitidine, respectively. Concentrations adhering to Beers law were from 40-160 µg mL-1 for Famotidine and from 20-100 µg mL-1 for Ranitidine. Furthermore the resulting condensation products exhibited fluorescence at 665 nm when excited at 290 nm and the calibration graphs were rectilinear from 0.4-1.4 µg mL-1 for Famotidine and from 0.21 µg mL-1 for Ranitidine. Different parameters affecting these reactions were thoroughly studied. Also these methods were applied to the pharmaceutical preparations and the results were satisfactory. The validities of the methods were ascertained by the standard addition technique revealing fine results in consideration to the mean recovery percent and standard deviation. The spectrofluorimetric method was a hundred times more sensitive then the spectrophotometric method. The proposed methods were sensitive, accurate, and precise as statistically compared with the official methods of analysis of Famotidine and Ranitidine.
Pharmaceutical Plasma Human Spectrophotometry Fluorescence

"Specific Spectrofluorometric Quantification Of D-penicillamine In Bulk And Dosage Forms After Derivatization With 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 169-175
A. A. Al-Majed

Abstract: A specific and sensitive fluorometric method is proposed for the determination of D-penicillamine in pure form and pharmaceuticals. The method is based on coupling between D-penicillamine and 4-fluoro-7-nitrobenzo-2-oxa-1,3-dizole (NBD-F) to produce the corresponding fluorescent NBD-penicillamine. The optimum conditions for the reaction were carefully investigated and incorporated into the procedure. The reaction was proceeded in berate buffer (pH 7.2) containing 20% of ethanol to give intense fluorescence having its excitation and emission wavelengths at 465 and 530 nm, respectively. The fluorescence intensity was a linear function of the drug concentration over the range of 0.6-3 µg mL-1. Regression analysis of the concentration fluorescence intensity showed good correlation (r = 0.9975) with a detection limit of 2 x 10^-3 µg mL-1 (1.3 x 10^-8 M). The mean of percentage recoveries of added authentic drug was 100.00±1.05. The method was applied successfully to the determination of this drug in pharmaceutical dosage form. The mean recovery for the commercial capsules was 98.1±0.54%. The results were sufficiently accurate, precise and comparable with those obtained from the official method. The method is specific for the intact drug, and can be adopted in the presence of possible interferences.
Penicillamine D Pharmaceutical Fluorescence

"Spectrophotometric Estimation Of D-penicillamine In Bulk And Dosage Forms Using 2,6-dichloroquinone-4-chlorimide (DCQ)"
J. Pharm. Biomed. Anal. 1999 Volume 21, Issue 4 Pages 827-833
A. A. Al-Majed

Abstract: A simple colorimetric method for the determination of D-penicillamine in pure form and pharmaceutical formulations is described. The method is based on coupling between D-penicillamine and 2,6-dichloroquinone-4-chlorimide (DCQ) in dimethylsulfoxide. The optimum conditions for the reaction were investigated and incorporated into the procedure. The reaction forms a yellow 1:1 complex with maximum absorbance at 431 nm (epsilon = 3700). Regression analysis of Beers plot showed good correlation (r = 0.9998) and the calibration graph was rectilinear over the range 4-20 µg mL-1 with a detection limit of 0.15 µg mL-1. The average recovery for the commercial capsules was 101.66% with an RSD of 1.57%. The results obtained were sufficiently accurate, reproducible and in accordance with those given by the official method. The method is specific for the intact drug, and can be adopted in the presence of some interfering substances.
Penicillamine D Pharmaceutical Spectrophotometry

"Spectrophotometric Determination Of Cefadroxil In Drug Formulations Using Flow Injection Analysis"
Anal. Lett. 1999 Volume 32, Issue 15 Pages 2977-2988
I. F. Al-Momani; I. Awni; H. S. Khalil; F. Esmadi

Abstract: A flow injection analysis method for the determination of cefadroxil is proposed. The method is based on the hydrolysis of cefadroxil in sodium hydroxide solution followed by treatment with 1,4-phenylenediamine and Fe(III) in sulfuric acid solution to produce a violet color which has a maximum absorption at 600 nn. Variables such as acidity, reagent concentrations, flowrate of reagents and other Fl parameters were optimized to produce the most sensitive and reproducible results. The calibration graph is linear between 80 -320 mg/l. The detection limit is 40 mg/l with a relative standard deviation, RSD (n=6) of 1.8%. The proposed method, combining the advantages of speed and accuracy was applied to the determination of cefadroxil in pharmaceutical preparations. The results have been compared with those obtained using HPLC method (USP-procedure). Excellent agreement between the results of the proposed method and the HPLC method was observed.
Cefadroxil Pharmaceutical Spectrophotometry

"Selective Preconcentration Of Phenyl-mercury By Living Escherichia Coli And Its Determination By Cold Vapor Atomic Absorption Spectrometry"
Anal. Chim. Acta 2000 Volume 423, Issue 2 Pages 255-263
L. C. Robles, J. C. Feo and A. J. Aller

Abstract: A method is proposed for speciation of phenyl-mercury (Ph-Hg) in waters based on the retention of analyte by a living Escherichia coli strain (K-15) grown in the aqueous sample solution containing glucose as a nutrient. In the general procedure, equilibrium between the analyte in the sample and the living bacterial cells is allowed to be established. However, a theoretical model of the retention process, based on a rate-determining step in reaching the adsorption equilibrium, illustrates the feasibility of quantifying the analyte before equilibrium is reached. The Ph-Hg-biomass is separated from the solution by centrifugation and the amount of organo-mercury retained is determined directly in the biomass slurry by cold vapor atomic absorption spectrometry (CVAAS). Speciation of Ph-Hg from matrices containing other mercury species (ethyl-mercury, methyl-mercury, Hg2+, Hg(I)) and the CVAAS determination of Ph-Hg can be carried out with relative standard deviations of 2.2-5.3%. The detection limit for Ph-Hg under optimum conditions is 0.05 ng ml-1.
Phenylmercury Environmental Spectrophotometry

"Flow Injection Analysis Of Meloxicam Using UV-detection"
Pharmazie 2001 Volume 56, Issue 2 Pages 186-187
Sener, E.; Altiokka, G.; Atkosar, Z.; Tuncel, M.

Abstract: A method for the direct determination of meloxicam by flow injection analysis without colorizing the solutions and its application to the pharmaceutical preparations The optimum concentration. of MeOH, in view of peak morphol., was 10% to 50%. The best flow rate was 1 mL/min. Significant differences were observed in peak areas due to the low solubility of meloxicam below pH 7.
Meloxicam Pharmaceutical Spectrophotometry

"Sensitive Assay For Clavulanic Acid And Sulbactam In Pharmaceuticals And Blood Serum Using A Flow Injection Chemiluminometric Method"
Anal. Chim. Acta 2000 Volume 414, Issue 1-2 Pages 15-23
Fatma A. Aly, Nawal A. Alarfaj and Abdulrahman A. Alwarthan

Abstract: A sensitive, simple and inexpensive chemiluminescence (CL) method using flow injection is described for the determination of two β-lactamase inhibitors sulbactam sodium and clavulanic acid (potassium salt) in their pure form, in pharmaceutical preparations and added to blood serum. The method is based on the enhancing effect of these compounds on the CL generated by the oxidation of luminol with hydrogen peroxide in alkaline medium. The CL intensity is a linear function of sulbactam sodium concentration over the range 0.1-150 µg mL-1 with a detection limit (2 x noise) of 0.05 µg mL-1, and for clavulanic acid over the range 0.01-12 µg mL-1 with a detection limit of 0.01 µg mL-1. The method is applied successfully to the determination of the drugs in their dosage forms without interference from co-formulated drugs. The method is specific for the intact drugs in the presence of their degradation products.
Clavulanic acid Sulbactam Serum Human Pharmaceutical Pharmaceutical Chemiluminescence

"Determination Of Flufenamic Acid And Mefenamic Acid In Pharmaceutical Preparations And Biological Fluids Using Flow Injection Analysis With Tris(2,2 -bipyridyl)ruthenium(II) Chemiluminescence Detection"
Anal. Chim. Acta 2000 Volume 416, Issue 1 Pages 87-96
Fatma A. Aly, Salma A. Al-Tamimi and Abdulrahman A. Alwarthan

Abstract: A novel chemiluminescent method using flow injection has been investigated for the rapid and sensitive determination of flufenamic and mefenamic acids. The method is based on a tris(2,2-bipyridyl)ruthenium(III) chemiluminescence reaction. Ru(bipy)(3)(3+) is chemically generated by mixing two streams containing solutions of tris(2,2-bipyridyl)ruthenium(II) and acidic cerium(IV) sulfate. After selecting the best operating parameters calibration graphs were obtained over the concentration ranges 0.07-6.0 and 0.05-6.0 µg mL-1 for flufenamic acid and mefenamic acid, respectively. The Limits of detection (s/n = 3) were 3.6 x 10^-9 M flufenamic acid and 2.1 x 10^-7 M mefenamic acid. The method was successfully applied to the determination of these compounds in pharmaceutical formulations and biological fluids. A proposal for the reaction pathway was given.
Flufenamic acid Mefenamic acid Plasma Human Urine Pharmaceutical Chemiluminescence

"A Flow Injection-fluorometric Method For The Determination Of Ammonium In Fresh And Saline Waters With A View To In Situ Analyses"
Water Res. 2001 Volume 35, Issue 7 Pages 1777-1785
Alain Aminot, Roger Kérouel and Dominique Birot

Abstract: A version of the orthophthaldialdehyde-fluorescence ammonium determination for flow injection analysis (FIA) is presented here, with a view to its use for in situ, low-power consumption systems, Thus, the reaction temperature was limited to 30°C and FIA was used in stop-Bow mode (3 min stop). The calibration is linear up to 50 µmol L-1, but concentrations up to 100 µmol L-1 can be measured. Repeatability is around 1% in the range of 0.5-4 µmol L-1 and the detection limit is about 0.03 µmol L-1 Over the salinity range of 5-35 (seawater practical salinity scale) the salt effect is almost negligible (within±2%); and below salinity of 5 it increases to a maximum of -9% in fresh water compared to seawater. Hydrogen carbonate, dissolved oxygen and turbidity (either suspended sediments or phytoplankton cells) have almost no adverse effect in a wide range of concentrations, covering most natural water conditions. Relative interference of primary amines is negligible and mercury (a common sample preservative) does not depress the signal up to 20 mg L-1 Hg II. Sulfide, that may be present in areas with anoxic waters, depresses the signal only slightly and linearly (-9% at 100 µmol L-1 S2-). The method appears to be convenient for the determination of ammonium in most coastal, estuarine and fresh waters. Sample throughput is 9 h-1. The performance of the method can be improved, either by increasing the reaction time (low throughput) or, if enough energy is available, by increasing the reaction temperature (non-stop-flow mode, high throughput). Combining FIA and fluorometry appears to be interesting for in situ determination (submersible devices) of dissolved compounds in environments with variable salinity and turbidity (especially coastal and estuarine waters). (C) 2001 Elsevier Science Ltd. All rights reserved.
Ammonium Sea Estuarine Fluorescence

"Flow Injection Analysis-amperometric Determination Of Ascorbic And Uric Acids In Urine Using Arrays Of Gold Microelectrodes Modified By Electrodeposition Of Palladium"
Anal. Chim. Acta 2000 Volume 404, Issue 1 Pages 151-157
Renato C. Matos, Márcio A. Augelli, Claudimir L. Lago and Lúcio Angnes

Abstract: Uric acid (UA) and ascorbic acid (AA) present in urine were rapidly-determined by the amperometric method in association with flow injection analysis. An array of gold microelectrodes modified by electrochemical deposition of palladium was employed as the working electrode. Uric and ascorbic acids were quantified in urine using amperometric differential measurements at +0.75 and +0.55 V, respectively. This method is based on three steps involving the flow injection of: (1) the sample spiked with a standard solution, (2) the pure sample, and (3) the enzymatically treated sample. The enzymatic treatment was carried out with ascorbate oxidase, uricase, and peroxidase at pH 7. The calibration curves for freshly prepared ascorbic and uric acid standards were very linear in the concentration ranges of 0.44-2.64 mg L-1 (AA) and of 0.34-1.68 mg L-1 (UA) with a relative standard deviation (RSD) <1 %. For uric acid, the real sample analyzes where compared with the classical spectrophotometric method, showing deviations between 3.1 and 8.6% (n = 9).
Ascorbic acid Uric acid Urine Amperometry Electrode Electrode

"Field Method For The Determination Of Hexavalent Chromium By Ultrasonication And Strong Anion Exchange Solid Phase Extraction"
Anal. Chem. 1999 Volume 71, Issue 5 Pages 1027-1032
Jin Wang, Kevin Ashley, David Marlow, Ellen C. England, and Gary Carlton

Abstract: A simple, fast, sensitive, and economical held method was developed and evaluated for the determination of hexavalent chromium (Cr-VI) in environmental and workplace air samples. By means of ultrasonic extraction in combination with a strong anion-exchange solid-phase extraction (SAE-SPE) technique, the filtration, isolation, and determination of Cr-VI in the presence of trivalent chromium (Cr-III) and potential interferents was achieved. The method entails (1) ultrasonication in basic ammonium buffer solution to extract Cr-VI from environmental matrixes; (2) SAE-SPE to separate Cr-VI from Cr-III and interferences; (3) elution/acidification of the eluate; (4) complexation of chromium with 1,5-diphenylcarbazide; and (5) spectrophotometric determination of the colored chromium-diphenylcarbazone complex. Several critical parameters were optimized in order to effect the extraction of both soluble (K2CrO4) and insoluble (PbCrO4) forms of Cr-VI without inducing Cr-III oxidation or Cr-VI reduction. The method allowed for the dissolution and purification of Cr-VI from environmental and workplace air sample matrixes for up to 24 samples simultaneously in less than 90 min (including ultrasonication). The results demonstrated that the method was simple, fast, quantitative, and sufficiently sensitive for the determination of occupational exposures of Cr-VI. The method is applicable for on-site monitoring of Cr-VI in environmental and industrial hygiene samples.

"Synthesis, Characterisation And Preliminary Analytical Evaluation Of Three Oxamide Reagents For Peroxyoxalate Chemiluminescence"
Anal. Chim. Acta 2000 Volume 403, Issue 1-2 Pages 145-154
Neil W. Barnett, Richard Bos, Raelene N. Evans and Richard A. Russell

Abstract: The synthesis, characterisation and preliminary analytical evaluation of three oxamide reagents, for peroxyoxalate chemiluminescence, are described. The analytical figures of merit for the three oxamides were assessed using flow injection analysis and the fluorophores rhodamine B and fluoroescein in a solvent mixture consisting of tetrahydrofuran, acetonitrile and aqueous buffer (1 + 1 + 2 by volume). The calibration functions approached linearity and the best detection limit (for both analytes) was 2 x 10^-9 M when using the oxamide 2,2-oxalyl-bis [(trifluoromethanesulfonyl)imino] ethylene-bis(N-methylpyridinium) trifluoromethanesulfonate. These results were found to compare favourably with those obtained for, the popular peroxyoxalate chemiluminescence reagent, bis(2,4,6-trichlorophenyl) oxalate (TCPO), using an identical solvent system. However, the detection limits achieved with TCPO were degraded at pH 10 due to a significant increase in the background emission. The addition of the base catalyst, imidazole, to these chemiluminescent reactions resulted in the deterioration of analytical performance for both TCPO and the oxamide reagents.
Rhodamine B Fluorescein Chemiluminescence

"Ultrasonic Extraction Followed By Sonolysis-ozonolysis As A Sample Pretreatment Method For Determination Of Reactive Arsenic Toward Sodium Tetrahydroborate By Flow Injection-hydride Generation AAS"
Anal. Chem. 2001 Volume 73, Issue 15 Pages 3732-3736
J. L. Capelo, I. Lavilla, and C. Bendicho

Abstract: A new sample pretreatment method based on ultrasonic extraction in HCl medium and subsequent oxidation of the extracts by sonozone (i.e., sonolysis-ozonolysis) has been developed for determination of reactive arsenic toward sodium tetrahydroborate [mainly As(III) + As(V)] by flow injection-hydride generation atomic absorption spectrometry. This method avoids the use of intensive treatments with concentrated and corrosive acids, high pressures, and temperatures that are inherent with traditional wet or dry ashing procedures and entails reduced waste production and reagent consumption. A sonozone process at room temperature was optimized to break the bond of As to proteins and macromolecular constituents which was an essential requirement for effective reduction by L-cysteine prior to arsine generation. Spiking experiments showed that As(III), As(V), MMA, and DMA were fully recovered from several matrixes on applying the above treatment. On the other hand, a nonreducible As species such as arsenobetaine that is predominant in some biological samples remained unchanged. Application of the method to sediment, soil, fly ash, and plant CRMs demonstrated that, in general, a good agreement existed between certified and found As contents, thereby indicating the absence of nonreducible As forms. Low As recoveries were observed for fish CRMs, as a result of the nondegradability of arsenobetaine by sonozone. The detection limit of As in the samples investigated was in the range 0.19-2.8 µg g-1.

"A Sensitive And Rapid Assay For 4-aminophenol In Paracetamol Drug And Tablet Formulation, By Flow Injection Analysis With Spectrophotometric Detection"
Talanta 2002 Volume 58, Issue 6 Pages 1301-1310
M. S. Bloomfield

Abstract: 4-Aminophenol (4AP) is the primary degradation product of paracetamol which is limited at a low level (50 ppm or 0.005% w/w) in the drug substance by the European, United States, British and German Pharmacopoeias, employing a manual colorimetric limit test. The 4AP limit is widened to 1000 ppm or 0.1% w/w for the tablet product monographs, which quote the use of a less sensitive automated HPLC method. The lower drug substance specification limit is applied to our products, (50 ppm, equivalent to 25 µg 4AP in a tablet containing 500 mg paracetamol) and the pharmacopoeial HPLC assay was not suitable at this low level due to matrix interference. For routine analysis a rapid, automated assay was required. This paper presents a highly sensitive, precise and automated method employing the technique of Flow Injection (FI) analysis to quantitatively assay low levels of this degradant. A solution of the drug substance, or an extract of the tablets, containing 4AP and paracetamol is injected into a solvent carrier stream and merged on-line with alkaline sodium nitroprusside reagent, to form a specific blue derivative which is detected spectrophotometrically at 710 nm. Standard HPLC equipment is used throughout. The procedure is fully quantitative and has been optimized for sensitivity and robustness using a multivariate experimental design (multi-level Central Composite response surface) model. The method has been fully validated and is linear down to 0.01 µg mL-1. The approach should be applicable to a range of paracetamol products. (C) 2002 Elsevier Science B.V. All rights reserved.

"Luminol Electrochemiluminescence-based Fibre Optic Biosensors For Flow Injection Analysis Of Glucose And Lactate In Natural Samples"
Anal. Chim. Acta 1999 Volume 381, Issue 1 Pages 1-10
Christophe A. Marquette and Lo&iuml;c J. Blum

Abstract: A fiber optic biosensor based on the electrochemiluminescence of luminol has been developed for glucose and lactate flow injection analysis, The electrochemiluminescence of luminol was generated using a glassy carbon electrode polarised at +425 mV vs. a platinum pseudo-reference electrode. After optimization of the reaction conditions and physicochemical parameters influencing the sensor response, the measurement of hydrogen peroxide could be performed in the range 1.5 pmol-30 nmol. Glucose oxidase or lactate oxidase, were immobilized on polyamide and collagen membranes. With collagen as the enzymatic support, the detection limits for glucose and lactate were 60 pmol and 30 pmol, respectively, whereas with the enzymatic polyamide membranes, the corresponding values were 150 pmol and 60 pmol. In each case, glucose and lactate measurements could be performed over four decades. The luminol electrochemiluminescence-based biosensors were used for glucose and lactate measurements in sera and also for lactate measurements in whey solutions. Good agreements were obtained between the present method and reference methods. For glucose analysis in serum, the coefficient of variation for 53 repeated measurements performed over a 10 h period was 4.8% while for lactate analysis, 80 assays performed over a 15 h period gave a coefficient of variation of 6.7%.
Glucose Lactate Blood Serum Sensor Chemiluminescence Electrode

"Optimization Of Flame Atomic Absorption Spectrometry With Preconcentration By Flow Injection Online Sorbent Extraction Of Cadmium And Lead In Biological Materials"
Bol. Soc. Chilena Quim. 1999 Volume 44, Issue 3 Pages 321-335
BRUHN, CARLOS G., VILCHES, CAROLINA and CID, HERNAN J.

Abstract: A flow injection (FI) system with a minicolumn of bonded silica with octadecyl groups (C-18) to collect diethyldithiocarbamate complexes of Cd and Pb in reference solutions and in acid-digested hair and blood solutions was developed and evaluated by flame atomic absorption spectrometry (FAAS). The system was optimized by multivariate method, based on a factorial experimental design in two levels, selecting eight parameters that mostly affected the expected analytical signal. The detection limits (3s(BL)/slope, 60 s pre-concentration) were 0.7 and 5 µg/L for Cd and Pb, respectively and the sampling frequency was 40 samples/h. Effects of interfering ions are discussed. The methodology was validated by analysis of certified reference materials of hair and blood for Pb, and by recoveries of Cd and Pb spikes performed in hair and blood samples. Results for Pb agreed well with certified values and recoveries were satisfactory (103% in blood and 100% in hair). Also, the recovery of Cd in hair was fair (107%); however, in blood it was not quantitative (22%).
Cadmium Lead Hair Blood Spectrophotometry

"Colorimetric Flow Injection Analysis Of Dissolved Iron In High DOC Waters"
Water Res. 2001 Volume 35, Issue 2 Pages 363-372
Michael J. Pullin and Stephen E. Cabaniss

Abstract: An iron flow-injection analysis system has been optimized for the analysis of iron in waters high in dissolved organic carbon. The method detects either dissolved iron(II) or total dissolved iron with a detection limit of 10 nM, precision of 0.65% at 1 µM, and a dynamic range of four orders of magnitude. There are minimal interferences (<1%) from other metals at environmental concentrations. The iron(II) method measures iron(II) in the presence of excess iron(III) with less than 1% interference. When used with pre-acidified samples, the total dissolved iron method agrees well with electrothermal atomic absorption spectrometry for a variety of natural waters with a range of dissolved organic carbon (3-36 mg C/L) and iron (1-28 µM) concentrations. When used with samples at their ambient pH, the total dissolved iron method detects dissolved iron, but not colloidal iron (size fraction 0.05-0.45 µm).
Iron(2+) Lake River Spectrophotometry

"Determination Of Arsenic Species In Seawater By Flow Injection Hydride Generation In Situ Collection Followed By Graphite Furnace Atomic Absorption Spectrometry - Stability Of As(III)"
Anal. Chim. Acta 2000 Volume 418, Issue 1 Pages 19-31
Jean Yves Cabon and Nolwenn Cabon

Abstract: Dissolved arsenic is present in seawater at the 1 µg L-1 level in various chemical forms: mainly, As(III) and As(V) inorganic arsenic, MMA, DMA, and eventually, unknown organic compounds. The concentrations of the minor arsenic species are well below the detection limit of graphite furnace atomic absorption spectrometry (GFAAS). Therefore, a pre-concentration/separation step is generally required before their determination. In this study, arsenic species were determined in seawater by flow injection hydride generation (FI-HG), collection within the graphite furnace, followed by atomic absorption spectrometry. This protocol permitted a pre-concentration factor of about 1000 lowering the detection limit of arsenic in seawater to about 1.5 ng L-1 for a 10 mi sample volume under optimized experimental conditions. Based on the different responses of arsenic species towards hydride generation, an experimental protocol for arsenic speciation was proposed. Total arsenic could be determined after a thermal or a UV irradiation treatment in an alkaline persulfate medium after the conversion of all arsenic species to inorganic As(V). Total hydride-reactive species (As(III), As(V), monomethylarsenic (MMA) and dimethylarsenic (DMA)) could be determined for high NaBH4 and HCl concentrations because a similar analytical response was obtained for these individual species. As(III) could be determined alone by performing hydride generation in seawater at a pH of about 7-8. Non-hydride-reactive arsenic species were determined by the difference between total arsenic and hydride-reactive species. According to this analytical protocol, arsenic species were determined in reference estuarine and coastal seawaters. Hydride-reactive arsenic species were the major compounds, probably mainly As(V); this study tended also to confirm the presence of non-hydride-reactive organic species in seawater (15%). We also showed that As(III) was not stable in acidified seawater and was also slowly converted to As(V) in a coastal surface seawater at its natural pH. These results indicated that time and preservation conditions could severely modify the speciation of arsenic in seawater, particularly for the preservation of As(III).
Arsenic(3+) Arsenic(5+) Dimethylarsenic Monomethylarsine Sea Estuarine Spectrophotometry

"Determination Of Hemoglobin Based On Its Enzymatic Activity For The Oxidation Of O-phenylenediamine With Hydrogen Peroxide"
Anal. Chim. Acta 2000 Volume 413, Issue 1-2 Pages 109-113
Ke Zhang, Ruxiu Cai, Danhua Chen and Luyuan Mao

Abstract: A new method has been developed for the determination of hemoglobin (Hb) based on its enzymatic activity for the oxidation of o-phenylenediamine with hydrogen peroxide. Stopped-flow spectrophotometry was used to study the kinetic behavior of the oxidation reaction. The absorbance of the reaction product, 2,3-diaminophenazine, at the wavelength of 425 nm was recorded every millisecond during the first 0.2 min of the reaction. The initial reaction rate obtained at 48°C was proportional to the concentration of Hb in the range of 8.5 x 10^-56.5 x 10^-11 mol/l. Excess of bovine serum albumin, Ca(II), Mg(II), Cu(II) and glucose did not interfere. The relative standard deviations were within 5% for the determination of different concentrations of Hb. The detection limit was found to be 3.2 x 10^-12 mol/l.
Hemoglobin Urine Spectrophotometry

"Stopped-flow Spectrophotometric Determination Of Hydrogen Peroxide With Hemoglobin As Catalyst"
Talanta 2000 Volume 51, Issue 1 Pages 179-186
Ke Zhang, Luyuan Mao and Ruxiu Cai

Abstract: A rapid and sensitive method was proposed for the determination of hydrogen peroxide based on the catalytic effect of hemoglobin using o-phenylenediamine as the substrate. Stopped-flow spectrophotometric method was used to study the kinetic behavior of the oxidation reaction. The catalytic effectiveness of hemoglobin was compared with other four kinds of catalysts. The initial rate of the formation of the reaction product 2,3-diaminophenazine at the wavelength of 425 nm was monitored, permitting a detection limit of 9.2 x 10^-9 mol/l H2O2. A linear calibration graph was obtained over the H2O2 concentration range 5.0 x 10^-8-3.5 x 10^-6 mol/l, and the relative standard deviation at a H2O2 concentration of 5.0 x 10^-7 mol/l was 2.08%. Satisfied results were obtained in the determination of H2O2 in real samples by this method.
Hydrogen peroxide Rain Spectrophotometry

"Flow Injection Biamperometric Determination Of Chloramphenicol And Related Nitro Compounds By On-line Chemical Photodegradation"
Anal. Chim. Acta 2000 Volume 404, Issue 1 Pages 141-150
J. A. Garc&iacute;a Bautista, J. V. Garc&iacute;a Mateo and J. Mart&iacute;nez Calatayud

Abstract: An unsegmented continuous-flow assembly for the determination of chloramphenicol is proposed. The determination is based on the on-line photodegradation of the drug in an NH4+/NH3 buffer at pH 10.4 by using a photoreactor consisting of a 697 cm long x 0.8 mm ID piece of PTFE tubing coiled around an 8 W low-pressure mercury lamp. Photodegraded chloramphenicol is detected by photolytic cleavage of nitrite from the:parent compound as well as by organic oxidizing photofragments, and their subsequent reaction with iodide ion, which is monitored biamperometrically. Triiodide thus formed is detected in excess iodide solution by polarizing two platinum electrodes at 100 mV. The calibration graph is linear up to 8 mg L-1 chloramphenicol; the Limit of detection is 0.05 mg L-1, the relative standard deviation is 0.4% (for 25 replicates of 10 mg L-1 drug) and the throughput 68 samples h-1. The proposed method was used to determine chloramphenicol in commercially available pharmaceutical formulations and human urine.
Chloramphenicol Pharmaceutical Urine Biamperometry Electrode Clinical analysis

"Determination Of Various Arsenic Species By Flow Injection Hydride Generation Atomic Absorption Spectrometry: Investigation Of The Effects Of The Acid Concentration Of Different Reaction Media On The Generation Of Arsines"
Anal. Chim. Acta 2001 Volume 438, Issue 1-2 Pages 195-204
Pablo Carrero, Auristela Malav&eacute;, Jos&eacute; Luis Burguera, Marcela Burguera and Carlos Rond&oacute;n

Abstract: An on-line how injection hydride generation atomic absorption spectrometry (FI-HG-AAS) system was developed to study the effect of acid concentration on the arsine generation from arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) pretreated in different reaction media. The signals for the arsines generated from MMAA and DMAA prepared in aqueous pure medium substantially decreased at hydrochloric acid concentrations higher than 2 mol L-1. Neutralization of the acid in the reaction mixture after the HG process did not produce any appreciable effect on the arsine signals. When the arsenic species were prereduced with L-cysteine or mercaptoacetic acid to yield thiolate complex of As(III), the arsines generated produced different response profiles compared to those obtained in pure aqueous medium. In this case, similar maximum signals were obtained within a narrow range at low acid concentrations (from 0.06 to 0.12 mol l-1); thereafter a sharp decrease of the signals at hydrochloric acid concentrations around 1 mol L-1, followed by a sharp increase to reach a constant value at higher and different acid concentrations. These results might suggest two mechanisms for the arsine generation: (i) at low acid concentrations, the thiolate complexes of As(m) are rapidly converted into the respective arsines by BH4- and (ii) at high acid concentrations, the arsines are generated by the action of nascent hydrogen produced by the decomposition of BH4-.

"Investigation Of Problems Associated With The Determination Of Iodine In Glacial Acetic Acid Samples Using Flow Injection Analysis-inductively Coupled Plasma-mass Spectrometry"
Anal. Commun. 1999 Volume 36, Issue 8 Pages 295-298
Kathryn L. Ackley, Jason A. Day, Karen L. Sutton and Joseph A. Caruso

Abstract: Determination of iodine in glacial acetic acid is a major concern of acetic acid manufacturers and consumers. The use of ICP-MS for iodine determinations in acetic acid is hindered by memory effects that produce an elevated background signal necessitating long rinse times between samples. In this work, different analysis methods are employed in an attempt to minimize memory and matrix effects allowing for the accurate determination of iodine in glacial acetic acid using ICP-MS. Ammonium hydroxide solutions (3.7 and 7.4 M) were better at reducing the elevated iodine signal present after the introduction of an acetic acid sample than water or 0.3 M nitric acid. Memory effects were decreased when the sample was introduced by flow injection rather than constant sample aspiration. Peak areas generated by flow injection decreased significantly with increasing ammonium hydroxide concentration in the carrier solution. Iodine determinations made with 1.7 M ammonium hydroxide as the carrier solution were higher than determinations made with 3.7 M ammonium hydroxide as the carrier solution for the same samples, however, the percentage difference between the two determinations varied widely from sample to sample. All samples were analyzed by the method of standard additions in an attempt to compensate for matrix effects. This work illustrates the importance of the carrier solution in the determination of iodine in glacial acetic acid samples.
Iodine Organic compound

"Sequential Injection Analysis For The Determination Of Fuberidazole And Thiabendazole By Variable-angle Scanning Fluorescence Spectrometry"
Anal. Chim. Acta 2001 Volume 427, Issue 1 Pages 83-92
G. de Armas, E. Becerra, A. Cladera, J. M. Estela and V. Cerd&agrave;

Abstract: A study of the behavior of fuberidazole (FBZ) (2-(2-furyl)benzimidazole), and thiabendazole (TBZ) (2-(thiazol-4-yl)benzimidazoie) in a sequential injection system with a fluorimetric detector has been performed. Several variables such as pH, composition of buffers, volumes of sample and reagents, addition order, geometry of mixing coil and spectrofluorimetric parameters have been optimized. A pH 2 buffer solution was found to be optimal for both FBZ and TBZ. The calibration graphs are linear between 0.04 and 10 µg L-1 for FBZ and between 0.08 and 20 µg L-1 for TBZ with 3s detection limits of 0.012 and 0.02 µg L-1, respectively. The relative standard deviation (n = 10) was 0.3% for 1 µg L-1 of FBZ and 0.5% for 2 µg L-1 of TBZ. Resolution of the system was carried out by applying a multiple linear regression (MLR) calibration model. The method was applied to the determination of both fungicides added to natural waters. Recoveries between 96 and 106% were achieved.
Fuberidazole Thiabendazole Water Mineral Fluorescence

"Time-based Multisyringe Flow Injection System For The Spectrofluorimetric Determination Of Aluminum"
Anal. Chim. Acta 2002 Volume 455, Issue 1 Pages 149-157
Graciela de Armas, Manuel Mir&oacute;, Andreu Cladera, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: A time-based multisyringe flow injection procedure with spectrofluorimetric detection is proposed in this paper for the determination of aluminum in drinking water. The flow methodology is based on the simultaneous or sequential injection of sample and chelating reagent (viz. 8-hydroxyquinoline-5-sulphonic acid) plugs using a multicommutation approach so that three successive injections may be performed with a sole displacement of the piston driver bar of the burette. Thus, an injection throughput as high as 154 h-1 is achieved by sampling a 182 µL sample zone. In order to enhance the luminescence, the reaction is carried out in micellar medium using hexadecyltrimethylammonium chloride as surfactant. The influence of geometric and hydrodynamic variables as well as several parameters such as multicommutation timing, ligand and surfactant concentration and reagent pH was assessed. Under the selected working conditions, a linear dynamic range from 10 to 500 µg L-1 Al(III). a 3s detection limit of 0.5 µg L-1 and a coefficient of variation of 0.6% at the 30 µg L-1 level were obtained. The analytical features were compared with those reported in previous flow injection and sequential injection methods. The multisyringe technique was successfully applied to the determination of aluminum in drinking water at low mineralisation levels, validating the results by inductively coupled plasma atomic emission spectrometry.
Aluminum(III) Water Fluorescence

"Multisyringe Flow Injection System For Total Inorganic Arsenic Determination By Hydride Generation-atomic Fluorescence Spectrometry"
Anal. Chim. Acta 2002 Volume 455, Issue 2 Pages 277-285
N. V. Semenova, L. O. Leal, R. Forteza and V. Cerd&agrave;

Abstract: A software-controlled time-based multisyringe flow injection system for total inorganic arsenic determination by hydride generation atomic fluorescence spectrometry (HGAFS) has been developed. By using a multisyringe burette coupled with one multiport selection valve, the time-based injection provides precise known volumes of sample, a reducing sodium tetrahydroborate solution and a pre-reducing solution which 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. Linear calibration graphs for arsenic concentrations between 0.25 and 12 µg L-1 were obtained. The detection limit of the proposed technique (3s(b)/S) was 0.07 µg L-1. A sample throughput of 36 samples/h (108 injections) has been achieved. The proposed technique has been validated by means of reference solid and water materials with good agreement with the certified values. This method was compared with those reported in previous sequential injection analysis (SIA) and flow injection analysis (FIA) systems. The proposed method offers a number of advantages in front the usual AFS applications, which are mainly a higher sampling frequency and a significant reduction in reagent consumption.
Selenium, inorganic NRCC DORM-1 NRCC DOLT-1 BCR 713 BCR 714 Fluorescence

"Implementation Of Chemiluminescence Detection In The Multisyringe Flow Injection Technique"
Anal. Chim. Acta 2002 Volume 467, Issue 1-2 Pages 155-166
Nicolau Piz&agrave;, Manuel Mir&oacute;, Graciela de Armas, Eduardo Becerra, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: The feasibility of multisyringe flow injection analysis (MSFIA) to perform liquid phase chemiluminescence (CL) analysis of trace metals using a newly developed laboratory-made luminometer is demonstrated. The noteworthy features of both the flow detector and the automated set-up are their robustness, operational simplicity and ease of construction and design. The CL reaction between 3-aminophthalhydrazide (luminol) and an oxidant species catalyzed by traces of metals in alkaline medium was chosen as a model to assess the potentialities and applicability of MSFIA with multicommutation for CL reactions. The methodology is based on merging the sample segment with plugs of an oxidant (hydrogen peroxide) and the luminol solution in alkaline medium at a total flow rate as high as 25 mL min-1 through a four-way junction point placed as close as possible to the photosensor module. Under the optimum conditions, a linear log-log regression between light emission intensity and catalyst concentration was found over the range from 15 ng L-1 to 5 µg L-1 for Co(II), although all experimental data better fitted a quadratic calibration graph. An injection throughput as high as 180 h-1 for 200 µL samples, a repeatability of 1.0% (n = 8) at the 1 ng mL-1 level and a 3s detection limit of 15 ng L-1 were the analytical features of the developed analyzer for determination of ultratrace levels of cobalt. The developed CL-MSFIA method was successfully applied to degradation studies of Vitamin B-12 (cyanocobalamin) at low acid concentrations based upon the release of cobalt from the tetrapyrrole complex. (C) 2002 Elsevier Science B.V. All rights reserved.
Cobalt(II) Chemiluminescence

"Fluorimetric Sequential Injection Analysis Of Aluminum In A Micellar Medium"
Quim. Anal. 2002 Volume 20, Issue 4 Pages 211-215
de Armas, G.;Torres, J.R.;Cladera, A.;Estela, J.M.;Cerda, V.

Abstract: This work presents a sequential-injection system for the determination of aluminum in water. The system is based on the spectrofluorimetric detection of the complex formed between 8-hydroxyquinoline-5-sulphonic acid (HQS) and aluminum. The reaction is carried out in a micellar medium using cetyltrimethylammonium chloride as surfactant. The influence of several variables, such as reagent and surfactant concentration and pH, has been investigated. A detection limit of 6 µg L-1 of aluminum was obtained. The method has been applied to a drinking water sample.
Aluminum Water Fluorescence

"Fluorimetric Sequential Injection Determination Of Magnesium Using 8-hydroxiquinoline-5-sulfonic Acid In A Micellar Medium"
Talanta 2000 Volume 52, Issue 1 Pages 77-82
G. de Armas, A. Cladera, E. Becerra, J. M. Estela and V. Cerd&agrave;

Abstract: A fluorimetric sequential injection method for the determination of magnesium is proposed. The system is based on the complex formation between Mg(II) and 8-hydroxyquinoline-5-sulfonic acid (HQS). The reaction was carried out in the presence of ethylene glycol-bis(β-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA) as a masking agent. Cetyltrimethylammonium chloride (HTAC) was employed as a fluorescence enhancer. The influence of several variables, such as reagent concentration, volumes and pH has been investigated. The reagent was prepared in a 0.1 M Tris-HCl buffer solution (pH 9). A detection limit of 12 µg L-1 magnesium was obtained. The proposed method was applied to the determination of magnesium in natural waters.
Magnesium Environmental Fluorescence

"Studies Of Micelle And Trace Non-polar Organic Solvent On A New Chemiluminescence System And Its Application To Flow Injection Analysis"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 75-81
Guo-Fang Zhang and Hong-Yuan Chen

Abstract: A sensitive and stable IO4--H2O2 chemiluminescence (CL) system for flow injection determination of sodium dodecylbenzene sulfonate (SDBS) is described. Weak CL is emitted when H2O2 is oxidized by sodium periodate. In this system, various surfactants enhance CL intensity, especially SDBS. The effects of non-polar organic solvents on CL are also reported. The 3s detection limit for SDBS is 3.2 x 10^-8 g mL-1 in a system using a trace of cyclohexane and the relative standard deviation of this method is 1.6% at 1.0 x 10^-6 g mL-1 for 11 determinations; SDBS in detergents is determined.
Sodium dodecylbenzyl sulfonate Chemiluminescence

"A New Flow Injection System For Spectrophotometric Determination Of Phosphate Ions"
Rev. Roum. Chim. 1999 Volume 44, Issue 8 Pages 771-777
Cheregi, M.C.;Danet, A.F.

Abstract: A flow injection system for determining the phosphate ions in natural, drinking, and residual waters was assembled. It contained an injection device with several mono-channel valves which can be either opened or shut simultaneously. Determination of PO43- ion with this FIA system is done by using the method based on the formation of phosphomolybdenum blue and spectrophotometric detection at 660 nm of the reaction product. The influence of different operational parameters was investigated. The calibration curve was linear over the 1-30 µg PO43- mL-1 domain, the relative standard deviation was 1.8% (n = 10) and the number of samples that could be analyzed was 30 h-1. A study on possibly interfering ions was also carried out. (SFS)
Phosphate Environmental Water Runoff Spectrophotometry

"Pt/Nafion/Pt Electrode Applied To Ammonium Ion Sensor"
Proc. Electrochem. Soc. 1999 Volume 13, Issue 1 Pages 398-408
T. C. Chou, K. W. Chiou, H. S. Twu, and T. R. Ling

Abstract: Pt/Nafion/Pt electrode prepared by impregnation reduction method was carried out to monitor ammonium ion concentration. in a flow injection system. The current response of the electrode was examined by step change of ammonium ion solution The best sensing condition was determined The preparation conditions of the Pt/Nafion/Pt electrode including impregnation time, temp., and concentration of Pt-solution were optimized, meanwhile, the reducing agent concentration. and its pH value were changed to obtain the max. response current. Different electrolytes were employed to the electrode to compare their performance of sensitivity. The interference of chloride, nitrate, and acetate anions were studied for evaluating their selectivity coefficients to NH3 ion. The sensing mechanism of the electrode on detecting ammonium ion is also discussed.
Ammonium Electrode

"Minireview: A Critical Review Of The Transition Metal Ions Influence On Peroxyoxalate Chemiluminescence"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 391-404
Margareth Mie Nakamura; Sergio Adriano Saraiva; Nina Coichev

Abstract: A detailed study and evaluation of the presence of Cr(III), Zn(II) and Pb(II) and various parameters affecting the intensity of the chemiluminescent reaction of TCPO and 2-NPO with hydrogen peroxide in the presence of 3-aminofluoranthene, as the fluorophore, and imidazole (IMI) as catalyst, is presented. Depending on the unprotonated imidazole and fluorophore concentrations, these metal ions enhance the intensity of the fluorophore at pHs higher than 8.0. At pH = 7.0, in the presence of IMI/HIMI+ (IMI = 1 x 10^-2 mol.L-1), tris(hydroxymethyl)aminomethane or HPO42-/H2PO4- buffers, no effect of these metal ions was observed. A critical comparison with the data reported in the literature is presented.

"Spectrofluorimetric Determination Of Aluminum In Drinking Waters By Sequential Injection Analysis"
Anal. Chim. Acta 2002 Volume 457, Issue 2 Pages 311-318
C. Brach-Papa, B. Coulomb, J. -L. Boudenne, V. Cerda and F. Theraulaz

Abstract: A selective procedure for the determination of Al3+ in drinking and natural waters is proposed, The analytical procedure is based both on the complex formation between Al3+ and 8-hydroxyquinoline-5-sulfonic acid (HQS) and on a fluorimetric detection of the complex. The reaction was carried out in presence of thioglycolic acid as a masking agent. This procedure has been adapted to a sequential injection analysis (SIA) system. Operative conditions both for batch and SIA procedures were investigated including reagent concentration, volumes, pH and wavelengths used for the fluorimetric detection. Batch procedure allows determination of Al3+ at ppb level (LOQ: 2.8 µg L-1) within a working range of 2.2-300 µg L-1. The SIA procedure was successfully employed for the determination of Al3+ in several commercial drinking and tap waters.
Aluminum(III) Water Fluorescence

"Detection Of Tannic Acid At Trace Level In Industrial Wastewaters Using A Highly Sensitive Chemiluminescence Method"
Water Res. 2003 Volume 37, Issue 1 Pages 233-237
Chenggen Xie and Hua Cui

Abstract: A novel flow injection procedure was developed for the determination of tannic acid in industrial wastewaters based on the enhancement by tannic acid of the chemiluminescence from luminol similar to K3Fe(CN)(6)-OH- system. The method has the merits of higher sensitivity, higher selectivity, wider linear range, simpler instrumentation. It is applicable for the determination of tannic acid in the range of 3.0 x 10^-10-1.0 x 10^-7 mol/L with a detection limit of 1.0 x 10^-10 mol/L. The relative standard deviation is 2.7% for the determination of 1.0 x 10^-8 mol/L tannic acid (n = 11). The method has been successfully used to determine tannic acid at trace level in industrial wastewaters from brewery and tannery. (C) 2002 Elsevier Science Ltd. All rights reserved.
Tannic acid Industrial Chemiluminescence

"Introduction Of Alcohols In Inductively Coupled Plasma Mass Spectrometry By A Flow Injection System"
Anal. Chim. Acta 1999 Volume 379, Issue 1-2 Pages 175-183
Valderi L. Dressler, Dirce Pozebon and Adilson J. Curtius

Abstract: A flow injection system for the introduction of organic solvents in an instrument of inductively coupled plasma mass spectrometry, using the conventional pneumatic nebulization, is proposed. The instrumental parameters, such as radiofrequency power, nebulization gas flow rate, solution flow rate and time interval between consecutive injections, were optimized for injecting analytical solutions in methanol, ethanol, l-propanol and 1% (v/v) nitric acid in water. In comparison to the conditions for the aqueous solution, a higher power and lower nebulization gas flow rates were adopted for the alcohol solutions. The Ba2+/Ba+ signals ratios are lower in the alcohol solutions, while the CeO+/Ce+ signals ratios are similar in all solvents. The signal intensities for the studied isotopes are enhanced in the organic media, partially due to a criterium used in the optimization, that is, CeO+/Ce+ signal ratio below 3%. The enhancement is specially high for Se, As and Hg. The proposed FIA system, with an injection of a small volume, typically 100 µl, of the organic solvent, on Line diluted 1+1 with water, and the continuous washing with an aqueous solution containing 1% (v/v) nitric acid, between the injections, allows the use of the instrument for more than 200 readings, without reoptimization of the plasma conditions and without visible carbon deposits on the cones. The addition of oxygen to the nebulization gas does not bring a real advantage.
Selenium Arsenic Mercury Mass spectrometry

"Application Of Natural Computation Techniques To Optimal Design Of Flow Injection Systems"
Anal. Chim. Acta 1999 Volume 402, Issue 1-2 Pages 275-283
J. de Gracia, A. Araujo, J. L. F. C. Lima, I. Villaescusa and M. Poch

Abstract: Row injection (FI) systems are widely used for online monitoring of chemical processes. Several approaches have been made in order to achieve the optimal design of the FI system, mainly based on the approach of deterministic models that describe the process using the mass balances around the system and the corresponding kinetic relations. Although, good results have been obtained with this approach, the complexity of the system and the effort necessary to calculate the parameters that characterize the FI system using a deterministic model, have led to the consideration of more empirical approaches to obtain a model of the process. In this paper, the authors present the results obtained in the application of two techniques, known as natural intelligence techniques, in the optimal design of a flow injection sandwich system for glucose and glycerol analysis. The optimization is performed using a genetic algorithm, in which a population evolves combining the genetic code of the most capable individuals of the previous generation. To evaluate the performance of each individual an artificial neural network is used. The results obtained with this approach are comparable with the one previously developed using a deterministic description of the FT system.

"On-line Bidirectional Electrostacking Of Chromium(III) And Chromium(VI) For Flame Atomic Absorption Spectrometry Determination"
Anal. Chim. Acta 2000 Volume 421, Issue 1 Pages 57-65
Youzhao He, M. Luisa Cervera, M. Isabel Garrido-Ecija and Miguel de la Guardia

Abstract: An on-line bidirectional electrostacking-flow injection-flame atomic absorption spectrometry method has been developed for the simultaneous separation, pre-concentration and determination of Cr(III) and Cr(VI). The electrostacking-flow injection unit was established, the pH and components of the support buffer and sample medium were investigated. Results indicated that the ionic mobility, electric field strength and sample area cross-section are the main influence factors on the electrostacking. The calibration range for both, Cr(III) and Cr(VI), was from 20 to 400 µg L-1. The limit of detection was 7 µg L-1 for three-times the standard deviation of blank values using a electrostacking time of 350 s. The recovery percentages of 100 µg L-1 Cr(III) and 25 µg L-1 Cr(VI) added to samples were 100 and 94% with variation coefficients of 7 and 10%, respectively.
Chromium(III) Chromium(VI) Electrophoresis Spectrophotometry

"Flow Injection Fourier Transform Infrared Determination Of Caffeine In Coffee"
Vib. Spectrosc. 1999 Volume 21, Issue 1-2 Pages 143-150
Zouhair Bouhsain, Jose M. Garrigues, Salvador Garrigues and Miguel de la Guardia

Abstract: A fully automatized procedure has been developed for the Fourier transform infrared (FT-IR) spectroscopic determination of caffeine in coffee samples. The method involves the online extraction of caffeine with CHCl3. Samples, weighed inside empty PTFE cartridges of 0.5 cm internal diameter (i.d.) and 1.5 mL volume, were humidified with four drops of 0.25 M NH3. The cartridge was installed in a flow manifold, in which samples were extracted in a closed-flow system with 1 mL CHCl3, during 6 min. Four hundred microliters of the extract were introduced in a microflow cell and absorbance measured as a function of time at 1659 cm-1, with a baseline established between 1900 and 830 cm-1, thus providing a fiagram. Peak height values of the Fl recordings, obtained for samples, were interpolated in an external calibration line established from standard solutions of caffeine in CHCl3,. The method provided a limit of detection (LOD) of 9 mg L-1 caffeine, a relative standard deviation of 0.6% for five independent measurements of a solution containing 1 mg mL-1 and a sampling frequency of the whole procedure of 6 h-1. Results obtained for market samples agree well with those found by the official chromatographic-spectrometric method, but involving a drastic reduction of solvents, from the 200 mL ether and 50 mL CHCl3, required for each sample preparation by the reference procedure to less than 30 mL CHCl3, necessaries for the whole determination of caffeine in a sample, also including standards and carrier solution.
Caffeine Coffee Spectrophotometry

"Potentiometric Flow Injection Determination Of Vitamin C And Glutathione With A Chemically Prepared Tubular Silver Electrode"
Pharmazie 2000 Volume 55, Issue 12 Pages 913-916
Kolar, M., Dobcnik, D.; Radic, N.J.

Abstract: This paper describes the preparation and use of a tubular electrode by means of chemical pretreatment of a silver tube with mercuric (II) chloride solution and iodide solution in flow injection analysis (FIA). The electrode was used as a potentiometric sensor for the indirect determination of vitamin C and glutathione in a carrier stream containing iodine. A simple FIA system that consists of a peristaltic pump, an injection T valve, a tubular silver electrode and a saturated calomel reference electrode (SCE) was used. Some typical FIA parameters such as flow rate, tube length, sample volume and composition of the carrier stream were varied. After optimization of these parameters, the electrode was further characterized by a constant linear response within the concentration range for the vitamin C between 5 x 10^-5 and 5 x 10^-3 M at the slope of 60.5±1.0 mV/p (vitamin C). Glutathione has a linear concentration range between 5 x 10^-5 and 10^-2 M at a slope of 55.2±1.0 mV/p (glutathione). The experimental slope was in good agreement with the theoretical values. Some pharmaceutical products containing vitamin C were also tested. These results can be compared to the results obtained by the standard volumetric method for the determination of vitamin C and are also in good agreement with values declared by pharmaceutical manufacturers.
Ascorbic acid Glutathione Pharmaceutical Electrode Potentiometry

"Amperometric Enzyme Electrode For The Determination Of Hydrogen Peroxide Based On Sol-gel/hydrogel Composite Film"
Anal. Chim. Acta 2000 Volume 407, Issue 1-2 Pages 111-118
Bingquan Wang, Jingzhong Zhang, Guangjin Cheng and Shaojun Dong

Abstract: A new type of organic-inorganic composite material was prepared by sol-gel method, and a peroxidase biosensor was fabricated by simply dropping sol-gel-peroxidase mixture onto glassy carbon electrode surface. The sol-gel composite film and enzyme membrane were characterized by Fourier-transform infrared (FT-IR) spectroscopy and EQCM, the electrochemical behavior of the biosensor was studied with potassium hexacyanoferrate(II) as a mediator, and the effects of pH and operating potential were explored for optimum analytical performance by using amperometric method. The response time of the biosensor was about 10 s; the linear range was up to 3.4 mM with a detection limit of 5 x 10^-7 M. The sensor also exhibited high sensitivity (15 µA mM-1) and good long-term stability. In addition, the performance of the biosensor was investigated using flow injection analysis (FIA), and the determination of hydrogen peroxide in real samples was discussed.
Hydrogen peroxide Amperometry Electrode Electrode

"The Speciation Of Arsenic Compounds"
Chem. Anal. 2002 Volume 47, Issue 2 Pages 179-188
L. Ebdon, S. Fitzpatrick and M.E. Foulkes

Abstract: It is known that arsenic demonstrates species-dependent toxicity. Quantification of elemental species in a sample, rather than determining total element levels alone, provides information that can be utilised in assessing toxicity, bioavailability and potential effects on the environment. High performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) has proved an extremely efficient tool for identification and determination of arsenic species providing limits of detection at µg L-1 levels. Low-pressure ion exchange chromatograph using mini-columns can provide a simple. yet effective, method for rapid screening of samples. Inorganic forms of arsenic can be separated from organic forms within 3 in in with limits of detection at 1.6 and 1.8 mug kg-1, respectively. The increasing use of electrospray techniques to provide structural information has enhanced the ability to distinguish with confidence previously unidentified species.

"Simultaneous Determination Of Nitrite And Nitrate In Various Samples Using Flow Injection With Spectrophotometric Detection"
Anal. Chim. Acta 1999 Volume 382, Issue 1-2 Pages 15-21
Ali A. Ensafi and A. Kazemzadeh

Abstract: A direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow injection analysis has been developed. The method is based on catalytic effect of nitrite on the oxidation of gallocyanine by bromate in acidic media and the decrease in absorbance of the system at 530 nm. The injected sample is split into two segments. One of the streams was directly treated with the above reagents and passed to the sample how cell of the spectrophotometer. The decrease in absorbance at 530 nm is due to the nitrite. The other stream was passed through a reductor minicolumn containing copperized-cadmium, where reduction of nitrate to nitrite occurs, and then the sample was treated with the mixed reagents and was passed through the same cell of the spectrophotometer. The total nitrite concentration initially plus that produced was determined. The influences of reagent concentration and manifold parameters were studied. The effect of potential interfering ions was examined. Nitrite and nitrate can be determined for the range of 0.010-2.500 µg mL-1 and 0.020-3.500 µg mL-1, respectively. The sampling rate of analysis was 20±3 hr-1, with 3s detection limits of 0.001 and 0.002 µg mL-1 for nitrite and nitrate, respectively. Nitrite and nitrate were determined in food and water samples by the proposed method with satisfactory results.
Nitrate Nitrite Food Environmental Spectrophotometry

"Application Of Chromaticity Characteristics For Direct Determination Of Trace Aluminum With Eriochrome Cyanine R By Diffuse Reflection Spectroscopy"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 145-151
Natalija I. Ershova and Vadim M. Ivanov

Abstract: Eriochrome cyanine R (ECR) has been applied as immobilized reagent for the direct determination of aluminum by diffuse reflection spectroscopy. Sorption ability of aluminum species depends on the kind of solid support and increases in the following sequence: anionite AV-17 < silica gel < chromaton-N- super < cellulose. Chromaticity characteristics of the aluminum sorbates, namely, color Lightness (L), chromaticity coordinates (A, B), saturation (S), hue (T), brightness (Y), whiteness (W), yellowness (G), and the total color difference (Delta E), indicate better sensitivity and precision than the diffuse reflection coefficient. The experimental parameters (optical characteristics, acidity of aqueous solution, shaking time, volume of aqueous solution, etc.) affecting the sorption of aluminum species have been optimized. The detection limit is 0.004 mg/l for the aluminum complex immobilized on cellulose. The precision and accuracy of the proposed method was evaluated with real samples, e.g. surface water, salt CH3COONa.
Aluminum Surface Inorganic compound Spectroscopy

"On-line Detection Of Nitric Oxide Generated By The Enzymatic Action Of Nitric Oxide Synthase On L-arginine Using A Flow Injection Manifold And Chemiluminescence Detection"
Anal. Chim. Acta 2000 Volume 410, Issue 1-2 Pages 167-175
Nicholaos P. Evmiridis and Dachun Yao

Abstract: A study of the catalytic activity of nitric oxide synthase (NOS) on the conversion of arginine to NO and citrulline is made. The target of this report is to establish a method for on-line monitoring the reaction process using the chemiluminescence (CL) generated from NO in the luminol-H2O2 system. The NOS-catalytic activity is found to decrease with time on stream in a flow enzymatic reactor but the activity is recovered by proper treatment with restoring solution. For on-line detection of NO formed in-situ, using how injection with CL detection, the response is found more sensitive if a pulsed sampling procedure is employed rather than a continuous one; the sample in the former is small and is injected periodically between regeneration cycles. The optimal pH, temperature and flow rate were determined. The calibration graph under optimal conditions is linear for arginine concentration; the relative standard deviation is <1% and the effect of interferents present in biological fluids is found to be much different to those for the native enzyme in solution. The immobilized NOS-reactor was long lived.
Nitric oxide l-arginine Biological fluid Chemiluminescence

"Amperometric Flow-through Biosensor For The Determination Of Cholinesterase Inhibitors"
Anal. Chim. Acta 1999 Volume 385, Issue 1-3 Pages 13-21
G. A. Evtugyn, A. N. Ivanov, E. V. Gogol, J. -L. Marty and H. C. Budnikov

Abstract: An amperometric flow-through biosensor based on epoxy-carbon electrode and butyrylcholinesterase immobilized on nylon, cellulose nitrate or white tracing paper has been developed and examined for the determination of reversible and irreversible inhibitors. The analytical characteristics of inhibitor determination depend on the hydrophobicity of the membrane material. Flow-through biosensor with various enzymatic membranes makes it possible to determine fluoride in the concentration range 1 x 10^-4-25 x 10^-4 mol L-1 and 3.5 x 10^-5-1 x 10^-2 mol L-1 when cholinesterase solution is used. The analytical characteristics of fluoride determination do not differ significantly from those obtained in batch conditions. For diazinon the immobilization of cholinesterase results in the decrease of detection limits from 5 x 10^-9 mol L-1 (native enzyme) to 4 x 10^-9 mol L-1 (nylon membrane) and 1.5 x 10^-9 mol L-1 (cellulose nitrate membrane). The influence of membrane material on analytical characteristics of FIA determination of inhibitors is due to the non-stationary distribution of reagents (fluoride) or sorptional pre-concentration of the inhibitor (diazinon) in membrane.
Enzyme, cholinesterase Fluoride Sensor Amperometry Electrode Electrode

"A New Simple And Accurate Turbidimetric Method For Determination Of Ascorbic Acid In Pharmaceuticals And Fruits"
J. Chin. Chem. Soc. 2002 Volume 49, Issue 5 Pages 949-956
Mir Ali Farajzadeh and Sepideh Nagizadeh

Abstract: An accurate, simple, solvent free and inexpensive turbidimetric method is presented for the determination of ascorbic acid in pharmaceutical preparations and fruits. It needs no special reagents or precautions. In this method HgCl2 oxidizes ascorbic acid in citrate buffer at a pH of about 4 and produced Hg2Cl2 precipitate as monitored by turbidance measurements. The procedure is very simple and the experimental conditions such as temperature, ionic strength, stirring and time are not critical. High sensitivity and selectivity are two other advantages of this method. Linear dynamic range of the calibration curve is between 3-120 µg/mL with limit of detection (LOD) 1 µg/mL, which allows the ascorbic acid contents of most fruits and vegetables to be analyzed. On the other hand, the interference studies show that common compounds in real samples and colored substances have no considerable effect on the determination. Only filtration of some samples is necessary and other treatments, which are performed prior to determination of ascorbic acid by other analytical methods, are eliminated. Finally, ascorbic acid concentration in different samples is determined by the proposed method and obtained results are compared with the results of the official 2,6-dichlorophenolindophenol or iodimetric methods and a good agreement is obtained. This method is very sensitive in comparison with iodimetry and is very fast relative to the 2,6-dichlorophenolindophenol method.
Ascorbic acid Pharmaceutical Pharmaceutical Pharmaceutical Fruit Fruit Juice Turbidimetry

"Flow Injection Spectrophotometric Analysis Of Lead In Human Saliva For Monitoring Environmental Pollution"
Talanta 2001 Volume 54, Issue 1 Pages 45-52
Marta Luconi, M. Fernanda Silva, Roberto A. Olsina and Liliana Fernandez

Abstract: A new highly sensitive, simple and low-cost methodology for the direct determination of Pb (II) with 2-(5-bromo-2- pyridylazo)-5-dimethylaminophenol in ethanolic medium has been developed. The absorption spectroscopy of the complex has been examined in detail, and the chemical variables affecting the sensitivity of procedure studied. optimized and applied to the determination of trace amounts of lead in human saliva. Under the optimal experimental conditions, a precision of 1.61 x 10^-4 µg cm was achieved, the molar absorptivity being (i:) 5.6 x 10^-4 l mol-1 cm-1. An FI technique is proposed, and it is possible to determine trace levels of lead by injection into a steam buffered at pH 7.15, containing 70%, ethanol: 30% Tris buffer 3.5 x 10^-3 mol L-1 (pH = 7.2), 1 x 10^-4 mol-1 5-BrDMPAP. The FIA configuration allows the analysis of 45 samples per hour. The lower limit of detection (LOD) was 1 x 10^-7 mol L-1. The calibration plot was linear at least within two orders of magnitude of lead concentration. The use of an HPLC pump for the FI analysis led to a substantial improvement in the analytical performance of the method, which clearly satisfies the typical requirements for control processes. (C) 2001 Elsevier Science B.V. All rights reserved.

"Electrochemical Control Of Solid Phase Micro-extraction Using Unique Conducting Polymer Coated Fibers"
Anal. Commun. 1999 Volume 36, Issue 5 Pages 203-205
Thompson P. Gbatu, Ozcan Ceylan, Karen L. Sutton, Judith F. Rubinson, Ahmed Galal, Joseph A. Caruso and Harry B. Mark Jr

Abstract: The use of a solid phase micro-extraction (SPME) method with poly(3-methylthiophene) coated platinum micro-fiber electrodes to extract arsenate ions from aqueous solutions without derivatization is described. The fibers were fabricated by cycling the working electrode between -0.20 and +1.7 V (vs. Ag/AgCl) in an acetonitrile solution containing 50 mM 3-methylthiophene monomer and 75 mM tetrabutylammonium tetrafluoroborate (TBATFB) electrolyte. All electrochemical procedures (extraction and expulsion) were conducted in a three-electrode system. After fabrication, the conducting polymer film was immersed in the sample solution and converted to its oxidized, positively charged form by applying a constant potential of +1.2 V with respect to Ag/AgCl reference electrode. Arsenate ions migrated into the film to maintain electroneutrality. Upon subsequent reversal of the potential to -0.60 V vs. Ag/AgCl, the polymer film was converted to its reduced, neutral form and the arsenate ions were expelled into a smaller volume (200 µL) Of de-ionized water for analysis using flow injection with inductively coupled plasma mass spectrometric (ICP-MS) detection.

"Silica Gel-immobilized-dithioacetal Derivatives As Potential Solid Phase Extractors For Mercury(II)"
Talanta 2000 Volume 51, Issue 1 Pages 77-87
Mohamed E. Mahmoud and Gamal A. Gohar

Abstract: Dithioacetal derivatives with different para-substituents, X=H, CH3, OCH3, Cl and NO2 were synthesized and chemically immobilized on the surface of silica gel for the formation of five newly synthesized silica gel phases (I-V). Characterization of the silica gel surface modification by the organic compounds was accomplished by both the surface coverage determination as well as the infrared spectroscopic analysis. The metal sorption properties of the silica gel phases were studied to evaluate their performance toward metal-uptake, extraction and selective extraction processes of different metal ions from aqueous solutions based on examination of the various controlling factors. The studied and evaluated factors are the pH effect of metal ion solution on the metal capacity values (mmol g-1), equilibration shaking time on the percent extraction as well as the structure and substituent (X) effects on the determined mmol g-1 values. The results of these studies revealed a general rule of excellent affinity of these silica gel phases-immobilized-dithioacetal derivatives for selective extraction of mercury(II) in presence of other interfering metal ions giving rise to a range of 94-100% extraction of the spiked mercury(II) in the metal ions mixture. The potential application of the newly synthesized silica gel phases (I-V) for selective extraction of mercury(II) from two different natural water samples, namely sea and drinking tap water, spiked with 1.0 and 10.0 ng mL-1 mercury(II) were also studied by column technique followed by cold vapor atomic absorption analysis of the unretained mercury(II). The results indicated a good percent extraction and removal (90-100±3%) of the spiked mercury(II) by all the five silica gel phases. In addition, insignificant contribution by the matrix effect on the processes of selective solid phase extraction of mercury(II) from natural water samples was also evident.
Mercury(II) Sea Water Spectrophotometry

"A Comparison Between ICP-MS And AFS Detection For Arsenic Speciation In Environmental Samples"
Talanta 2000 Volume 51, Issue 2 Pages 257-268
Jose Luis G&oacute;mez-Ariza, Daniel S&aacute;nchez-Rodas, Inmaculada Gir&aacute;ldez and Emilio Morales

Abstract: Performances of two atomic detectors, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) arid Atomic Fluorescence Spectrometry (AFS) have been compared for arsenic speciation in environmental samples. Instrumental couplings, based on the use of high performance liquid chromatography (HPLIC), hydride generation (HG), and the two atomic detectors were used for the speciation of arsenite, arsenate, dimethylarsinic acid and monomethylarsonic acid. Optionally, arsenobetaine was also determined using on-line ultraviolet (UV) photooxidation. The detection limits ranging from 0.1 to 0.3 µg L-1 (as As) and the precision > 10% RSD obtained with HPLC-(UV)-HG-AFS were comparable with those obtained with HPLC-(UV)-HG-ICP-MS. Both instrumental coupling were applied to the NRCC-TORT-1 and several environmental samples, such as seawater, freshwater, sediments, bivalves and bird eggs, taken from two areas with different degrees of pollution. No influence of the sample matrix was observed on the results using external calibration and standard additions met:hods, for both coupled techniques.
Arsenate ion Arsenite Arsenoβine Dimethylarsinic acid monomethylarsonic acid NRCC TORT-1 Lobster Sea Environmental River Oyster Spoonbill Fluorescence Mass spectrometry Sample preparation HPLC

"Rapid Sr-90/Y-90 Determination In Water Samples Using A Sequential Injection Method"
Appl. Radiat. Isot. 2000 Volume 53, Issue 1-2 Pages 139-144
J. J. Mateos, E. G&oacute;mez, F. Garcias, M. Casas and V. Cerd&agrave;

Abstract: We have developed a semiautomatic procedure based on a sequential injection method for Sr-90/Y-90 determination that allows their radiochemical separation in about 30 min. The method has been tested using 90Sr/90Y solutions with activities lower than 12 Bq. The source is eluted in a pH = 6.5 medium through a MnO2-impregnated cotton filter, where Y-90 is pre-concentrated in preference by adsorption. 90Y is extracted from the column with hydroxylamine, some Sr-90 in the leached solution has also been found. After the radiochemical separation, the total β-activity of the leached solution has been determined using a low background α-β proportional counter and. assuming the presence of Sr-90 and Y-90 at t = 0, the solution of the Bateman equations allows the initial concentration of both isotopes to be obtained. We have verified that the addition of some ions usually found in water samples (Cl-, HCO3-, NO3-, SO42-, Ca2+, Mg2+) does not interfere with the yield of the radiochemical process, (90±10)%. The method has been applied to Sr-90/Y-90 determination in mineral waters, and even in thermal waters, where the salt concentration can be about 3500 mg/L, the radiochemical yield remains greater than 80%.
Strontium-90 Yttrium Mineral Waste

"Coupling On-line Preconcentration By Ion-exchange With ETAAS. A Novel Flow Injection Approach Based On The Use Of A Renewable Microcolumn As Demonstrated For The Determination Of Nickel In Environmental And Biological Samples"
Anal. Chim. Acta 2000 Volume 424, Issue 2 Pages 223-232
Jianhua Wang and Elo Harald Hansen

Abstract: A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange pre-concentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable microcolumn incorporated within an integrated µFI-system, the column is loaded with a defined volume of small beads of an SP Sephadex C-25 cation-exchange resin and subsequently exposed to a metered amount of sample solution. However, instead of eluting the retained analyte from the organic ion-exchange resin, the beads are along with 30 µL of carrier (buffer) solution transported via air segmentation directly into the graphite tube, where they are ashed during the pyrolysis and atomization process. The ETAAS determination is performed in parallel with the pre-concentration process of the ensuing sample. An enrichment factor of 72.1, a detection limit of 9 ng L-1, along with a sampling frequency of 12 h-1 were obtained with 150 s of sample loading time at a sample flow rate of 12 µL s-1 (corresponding to 0.72 mL min-1). The relative standard deviations were 3.4%. The procedure was validated by determination of the nickel contents in two certified reference materials and in a human urine sample.
Nickel Urine BCR 176 BCR 320 Ash River Spectrophotometry

"Further Studies Into The Development Of A Micro-FIA (µFIA) System Based On Electroosmotic Flow For The Determination Of Phosphate As Orthophosphate"
Anal. Chim. Acta 1999 Volume 382, Issue 1-2 Pages 1-13
G. N. Doku and S. J. Haswell

Abstract: Photolithographic and wet etching techniques were used to fabricate a µFIA manifold in a borosilicate glass substrate for the spectrophotometric determination of orthophosphate based on the molybdenum blue reaction, employing electroosmotic flow for both the mobilization of reagents and sample injection. The manifold channel dimensions were 200 µm wide and 50 µm deep. An evaluation of the electroosmotic flow characteristics (i.e. voltage, solution concentration/pH ranges and current-voltage relationships) for ascorbic acid, ammonium molybdate and orthophosphate standards, with and without berate buffer present, has been carried out. In addition, the effect that reaction precursors may have on the in situ spectrophotometric detection system is also discussed. Using the optimized operating conditions of 1.75% ascorbic acid and 0.6% ammonium molybdate in 10 mM berate buffer, the calibration model for phosphate standards was found to be linear (y = 0.0036x + 0.0155; correlation coefficient, r2 = 0.9952) over the working range 1-10 µg mL-1. A sampling rate of ~60 samples/h was achieved, with a detection limit of 0.1 µg mL-1 for orthophosphate, with RSDs <5%. The reagent consumption was very low with the total reactant volume in the system estimated to be 0.6 µL and a sample volume of 0.1 µL being required.
Phosphate Spectrophotometry Electrophoresis

"Flow Injection Spectrophotometric Determination Of Cyclamate In Sweetener Products With Sodium 1,2-naphthoquinone-4-sulfonate"
Anal. Chim. Acta 1999 Volume 381, Issue 2-3 Pages 307-313
Carolina Cabero, Javier Saurina and Santiago Hern&aacute;ndez-Cassou

Abstract: A method for the determination of cyclamate in sweetener tablets is proposed. The method is based on the conversion of cyclamate to cyclohexylamine and the subsequent reaction with 1,2-naphthoquinone-4-sulfonate, yielding a spectrophotometrically active derivative which is detected at 480 nm. The hydrolysis step is performed batch wise by treatment of cyclamate with hydrogen peroxide and hydrochloric acid, while the cyclohexylamine derivatization is carried out in a flow injection system. Conditions for both hydrolysis and derivatization have been optimized. The Linear range is up to 10^-3 M cyclamate, the overall repeatability 3.1% and the detection limit is 7.7 x 10^-6 M. The accuracy of the method proposed in the analysis of commercial sweetener tablets is about 3.5%.
Cyclamate Commercial product Spectrophotometry

"Determination Of Arsenic By Hydride Generation Coupled To Time-of-flight Mass Spectrometry With A Gas Sampling Glow Discharge"
Spectrochim. Acta B 2002 Volume 57, Issue 6 Pages 1009-1023
William C. Wetzel, Jos&eacute; A. C. Broekaert and Gary M. Hieftje

Abstract: Hydride generation has been used with a gas-sampling glow discharge (GSGD) and time-of-flight mass spectrometry (TOFMS) for the determination of arsenic in solution. Helium, neon, hydrogen, and argon glow discharges have been successfully generated and characterized. Current-pressure-voltage curves were generated for each discharge in the presence and absence of hydride generation. The arsenic detection limit for each of the discharges was found to be 0.60 (HeGSGD), 3.8 (NeGSGD) and 6.4 ppb (H(2)GSGD). The HeGSGD was found to be the most attractive source for arsenic determination due to the lower detection limit, higher sensitivity and greater stability. The figures of merit for these discharges were also compared to those obtained with hydride generation-inductively coupled plasma TOFMS. Noise power spectra obtained for the neon GSGD indicated that no discernible discrete-frequency (whistle-noise) components were present in the analyte signal. (C) 2002 Elsevier Science B.V. All rights reserved.

"Optimization Of On-line Microwave Flow Injection Analysis System By Artificial Neural Networks For The Determination Of Ruthenium"
Anal. Chim. Acta 2001 Volume 429, Issue 2 Pages 207-213
Huaiwen Wang, Yongyao Zhou, Yunkun Zhao, Qianfeng Li, Xingguo Chen and Zhide Hu

Abstract: A methodology based on the coupling of experimental design and artificial neural networks (ANNs) was proposed in the optimization of a new on-line microwave flow injection system (FIA) for the determination of ruthenium, grounded on its catalytic effect on the oxidation of dibromocarboxyarsenazo (DBM-AsA) by potassium periodide under the microwave irradiation. The response function (RF) used was a weighted linear combination of two variables related to sensitivity and sampling rate. A neural network with extended δ-bar-δ (EDBD) learning algorithm was applied to predict the maximal RE according to which the optimized conditions were obtained. The optimized new on-line microwave FIA system is able to determine ruthenium in 5-200 ng mL-1 range with a detection limit of 2.1 ng mL-1 and a recovery of 94.6%. A sampling rate of 58 h-1 was obtained. In contrast to traditional methods, the use of this methodology has advantages in terms of a reduction in analysis time and an improvement in the ability of optimization.

"Arsenic Speciation Based On Ion Exchange High-performance Liquid Chromatography Hyphenated With Hydride Generation Atomic Fluorescence And On-line UV Photo Oxidation"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 8 Pages 803-808
He Bin, Jiang Gui-bin, Xu Xiao-bai

Abstract: An on-line method capable of the separation of arsenic species was developed for the speciation of arsenite As(III), arsenate As(V), monomethylarsenic (MMA) and dimethylarsenic acid (DMA) in biological samples. The method is based on the combination of high-performance liquid chromatograph (HPLC) for separation, UV photo oxidation for sample digestion and hydride generation atomic fluorescence spectrometry (HGAFS) for sensitive detection. The best separation results were, obtained with an anion-exchange AS11 column protected by an AG11 guard column, and gradient elution with NaH2PO4 and water as mobile phase. The on-line UV photo oxidation with 1.5% K2S2O8 in 0.2 mol L-1 NaOH in an 8 m PTFE coil for 40 s ensures the digestion of organoarsenic compounds. Detection limits for the four species were in the range of 0.11-0.15 ng (20 µL injected). Procedures were validated by analysis of the certified reference materials GBW09103 freeze-dried human urine and the results were in good agreement with the certified values of total arsenic concentration. The method has been successfully applied to speciation studies of blood arsenic species with no need of sample pretreatment. Speciation of arsenic in blood samples collected from two patients after the ingestion of realgar-containing drug reveals slight increase of arsenite and DMA, resulting from the digestion of realgar.

"Online Ion-exchange Preconcentration In A Flow Injection System Coupled To Capillary Electrophoresis For The Direct Determination Of UV Absorbing Anions"
Anal. Chim. Acta 1999 Volume 390, Issue 1-3 Pages 39-44
Lourdes Arce, Petr Kuban, Angel R&iacute;os, Miguel Valc&aacute;rcel and Bo Karlberg

Abstract: Online ion-exchange pre-concentration, performed in a flow injection analysis system, has been integrated with capillary electrophoresis via a specially designed interface, and a sensitive and selective method for the determination of nitrite, nitrate, bromide and iodide using direct UV absorbance detection has been developed. Fivefold enrichment of these aforementioned anions can be realised. Separation conditions such as carrier electrolyte and concentration of electroosmotic modifier were investigated. Limits of detection were ~10 ng mL-1 for nitrite and nitrate in aqueous samples, and the overall relative standard deviation was about 5%.

"On-line Flow Sample Stacking In A Flow Injection Analysis-capillary Electrophoresis System: 2000-fold Enhancement Of Detection Sensitivity For Priority Phenol Pollutants"
J. Chromatogr. A 2001 Volume 912, Issue 1 Pages 163-170
Petr Kuban, Maria Berg, Carlos Garc&iacute;a and Bo Karlberg

Abstract: A flow injection analysis-capillary electrophoresis system has been used for on-line flow stacking of 11 US Environmental Protection Agency priority phenol pollutants. Samples containing low concentrations of phenols dissolved in deionised water are continuously delivered to the capillary opening by means of a peristaltic pump. The sample components stack at the boundary between the highly conductive separation electrolyte and the introduced sample. By selecting an appropriate electrolyte and stacking conditions the movement of the electrolyte solution inside the capillary can be reduced, thereby improving the stacking efficiency. The electrolyte used here contained 20 mM phosphate, 8% 2-butanol, and 0.001% hexamethonium bromide at pH 11.95, and the stacking was carried out at 2 kV for 240 s. These conditions allowed up to 2000-fold pre-concentration of the selected phenols. No matrix removal was necessary. (C) 2001 Elsevier Science B.V. All rights reserved.

"The Miniaturisation Of The Standard Method Based On The N,N -diethyl-p-phenylenediamine (DPD) Reagent For The Determination Of Free Or Combined Chlorine"
Water Res. 1999 Volume 33, Issue 2 Pages 375-380
Karin Carlsson, Ludvig Moberg and Bo Karlberg

Abstract: A miniaturised continuous flow method for the determination of free or combined chlorine in purification plant water has been developed. The method is based on the standard batch procedure which uses a phosphate buffer for pH adjustment and N,N-diethyl-p-phenylenediamine (DPD) as a colorimetric reagent. The sample, the reagent and the buffer Solutions are continuously pumped into a miniaturised flow system. The mixing, the thermostating and the chemical reaction take place in a manifold with an engraved zigzag flow channel. A flow through detector is positioned at the flow channel outlet. The flow channel volume is about 25 µl and the detector volume is 0.25 µl. An experimental design was performed revealing that the significant variables were the total flow rate and the length of the mixing channel. Based on the results from this experimental design a total flow rate of 90 µl/min and a channel length of 60 mm were selected. The total consumption of sample and reagent is less than 3.91 per month when the system is operated continuously. The response time is less than 2 min. When combined chlorine, in essence chloramine, is determined, potassium iodide is added to the buffer solution. The limit of detection is 3.2 µM for free chlorine and 1.9 µM for monochloramine.
Chloride Industrial Spectrophotometry

"Bioanalytical Flow Injection System For Control Of Hemodialysis Adequacy"
Anal. Chim. Acta 2000 Volume 418, Issue 2 Pages 213-224
Robert Koncki, Anna Radomska and Stanis&#322;aw G&#322;&#261;b

Abstract: Potentiometric urea biosensor based on ammonium-ion selective electrode has been used in simple flow injection bioanalytical system for the determination of removed urea in effluent Liquid during hemodialysis treatment. The interferences from other components of the spent dialysate (mainly potassium ions) were eliminated using reference cell detector with non-sensitized ammonium-ion electrode. The methods of signal correction were discussed. The presented flow injection analysis (FIA) system allowing monitoring of urea content in the range of concentrations correspond well with the amount of the analyte in real samples (1-20 mmol/l). Around 25 samples per hour can be analyzed. Due to long operational Life-time of the applied biosensor the FIA system can be useful over 3 weeks. The presented biosensor/FIA system has been successfully applied for the biomedical control of real clinical processes. The results of analysis are useful for the evaluation of the clinical parameters of urea kinetic modeling: parameters KT/V, urea reduction ratio (URR), percentage removal of urea (PRU) and total urea removal (TUR) for intradialytic intervals and urea generation rate (G) and protein catabolic rate (PCRn) for interdialytic intervals. These biomedical parameters are used for describing the adequacy of hemodialysis therapy.
Urea Dialysis Fluid Potentiometry Electrode Sensor

"Potentiometric Determination Of Dialysate Urea Nitrogen"
Talanta 2000 Volume 52, Issue 1 Pages 13-17
Robert Koncki, Anna Radomska and Stanislaw Glab

Abstract: An enzymatically modified ammonium ion-selective electrode has been applied for the determination of urea in spent dialysate. The biosensor has been used in a simple flow injection analysis (FIA) system. The system enables one to perform over 25 dialysate urea nitrogen (DUN) determinations per hour. The interferences from other components of posthemodialysis fluid were eliminated by simultaneous measurements with non-modified enzymatically ion-selective electrode. It is possible to use both the sensors in a simplified differential potentiometric system. The results of DUN determination using the biosensor/FIA system and a conventional method of urea determination were comparable. The presented analytical system can potentially find wider biomedical application in the monitoring of hemodialysis progress.

"Dissolved Organic Carbon Determination Using FIA And Photo-Fenton Reaction"
Braz. Arch. Biol. Technol. 2002 Volume 45, Issue 1 Pages 81-87
KONDO, M&aacute;rcia M., ARCOS, Maria A. S. V. and GRASSI, Marco T.

Abstract: The FIA-photo-Fenton system is based on the flow oxidation of the organic matter. A small amount of the sample containing H2O2 is injected into the acidic flow solution of Fe 21, which passes through a tubular PTFE reactor irradiated with UV light. The generated CO2 is quantified by a conductometric detector and is directly proportional to the dissolved organic carbon concentration in the sample. The optimization studies were performed using EDTA solutions. The average recovery of organic carbon was 83% with a relative standard deviation of 3.7% using a 1:5 molar ratio of Fe2+ :H2O2, pH 2.0, 100 µL of sample injection and a liquid flow of 1 mL min-1. After optimization, the DOC concentration was quantified using 13 different organic compounds, where the average recovery was 90%. The rate of the analysis was in average 50 samples hour-1.

"Xanthine And Hypoxanthine Sensors Based On Xanthine Oxidase Immobilized On A CuPtCl6 Chemically Modified Electrode And Liquid Chromatography Electrochemical Detection"
Anal. Chim. Acta 2000 Volume 414, Issue 1-2 Pages 205-213
Jianhong Pei and Xiao-yuan Li

Abstract: Xanthine oxidase has been immobilized on the surface of a CuPtCl6/glassy carbon chemically modified electrode. The enzyme electrode displays a quick and sensitive response to xanthine and hypoxanthine. The observed steady-state current is due to the oxidation of hydrogen peroxide Liberated during the enzyme reaction on the surface of the enzyme electrode. The effects of enzyme loading, pH, temperature, and applied potential have been discussed. The enzyme electrode was characterized as an amperometric sensor for xanthine (6 x 10^-7-2 x 10^-4 M) and hypoxanthine (5 x 10^-7-2 x 10^-4 M) with the detection limit of 1 x 10^-7 M. Liquid chromatographic separation coupled with the enzyme electrode as an electrochemical detector was used to analyze the mixtures of xanthine and hypoxanthine.
Xanthine Hypoxanthine Electrode Electrode Potentiometry HPLC

"Tissue Distribution Of Different Mercurial Compounds Analyzed By The Improved FI-CVAAS"
J. Anal. Toxicol. 2002 Volume 26, Issue 5 Pages 286-295
Cheng-Chieh Yen, Shing-Hwa Liu, Wen-Kang-Chen, Ruey-Hseng Lin, and Shoei-Yn Lin-Shiau

Abstract: Mercury contents in biological samples can be measured by cold vapor atomic absorption spectroscopy combined with the flow-injection analysis system. However, water vapor in the absorption cell attenuated and distorted the signals. This study described the strategy to overcome this problem by adding an additional gas-liquid separator after the mixing/separator assembly. This modification can efficiently minimize the moisture in the transfer line and in the absorption cell. This improved technique was adopted to study the differential tissue distribution of methylmercury and HgS after oral administration to mice for five consecutive days. The present study suggests that the insoluble HgS (the main constituent of a Chinese mineral drug, cinnabar, used as a sedative) can still be absorbed from gastrointestinal tract and distributed to various tissues including the brain. As compared with methylmercury, the total amount of HgS accumulated in the tissues ranging about one five-thousandth of methylmercury, which is well correlated with the biological activity of HgS reported previously.

"Flow Injection Analysis Of Pyrogallol With Enhanced Electrochemiluminescent Detection"
Anal. Chim. Acta 2000 Volume 423, Issue 2 Pages 247-253
Yu-Gang Sun, Hua Cui, Xiang-Qin Lin, Ying-Hui Li and Hua-Zhang Zhao

Abstract: Potential dependent inhibition and enhancement effects of pyrogallol on the electrochemiluminescence of luminol in alkaline solutions were found. On the basis of enhancement effect, a flow injection method was developed for the determination of pyrogallol. The method was simple, rapid and sensitive with a detection limit of 1.6 x 10^-8 mol/l, linear range of 7.0 x 10^-8-1.0 x 10^-4 mol/l, relative standard deviation of 2.2% for eleven measurements of 5.0 x 10^-6 mol/l pyrogallol. This method was successfully applied to determine the content of pyrogallol in a pyrolysis mixture of gallic acid. The mechanism of the inhibition and enhancement was proposed. Pyrogallol mostly reacted with the di-oxygen species electrogenerated at potentials more positive than 0.50V versus Ag/AgCl and generate superoxide radicals adsorbed on the electrode surface, which led to the enhancement of the electrochemiluminescence of luminol.
Pyrogallol Organic compound Chemiluminescence

"Development Of A Cellobiose Dehydrogenase Modified Electrode For Amperometric Detection Of Diphenols"
Analyst 1999 Volume 124, Issue 4 Pages 527-532
Annika Lindgren, Leonard Stoica, Tautgirdas Ruzgas, Anton Ciucu and Lo Gorton

Abstract: A new amperometric biosensor based on cellobiose dehydrogenase (CDH) was created for the detection of ortho-and para-diphenolic compounds. The developed electrode efficiently discriminates between diphenolic and monophenolic compounds. The analyte, a diphenolic compound, is oxidized on the surface of a graphite electrode at an applied potential of +300 mV vs. Ag/AgCl. The diphenol is then regenerated by the adsorbed CDH in the presence of cellobiose, thus allowing an amplified response signal. Different parameters of the CDH-electrode system were optimized, e.g., applied potential, immobilization time, flow rate, substrate concentration and storage conditions. Using the optimized parameters the sensitivity and detection limits for various diphenolic compounds were evaluated, resulting in detection limits below 5 nM for most of the compounds tested. The highest sensitivity recorded was obtained for dopamine, 3.6 A l mol-1 cm-2. The operational stability of the electrodes was high: during 2 h of continuous operation only a 1-2% decrease in response signal was observed.

"Application Of Artificial Neural Networks In Multifactor Optimization Of An On-line Microwave FIA System For Catalytic Kinetic Determination Of Ruthenium (III)"
Talanta 2001 Volume 54, Issue 4 Pages 603-609
Yi-Bo Zeng, Hong-Ping Xu, Hui-Tao Liu, Ke-Tai Wang, Xing-Guo Chen, Zhi-De Hu and Bo-tao Fan

Abstract: A methodology based on the coupling of experimental design and artificial neural networks (ANNs) is proposed in the optimization of a flow injection system for the spectrophotometric determination of Ru (III) with m-acetylchlorophosphonazo (CPA-mA), which has been for the first time used for the optimization of high-performance capillary zone electrophoresis (J. Chromatogr. A 793 (1998) 317). And since it has been applied in many other regions like micellar electrokinetic chromatography, ion-interaction chromatography, HPLC, etc. (J. Chromatogr. A 850 (1999) 345; J. Chromatogr. A 799 (1998) 35; J. Chromatogr. A 799 (1998) 47). An orthogonal design is utilized to design the experimental protocol, in which five variables are varied simultaneously (Anal. Chim. Acta 360 (1998) 227). Feedforward-type neural networks with extended δ-bar-δ (EDBD) algorithm are applied to model the system, and the optimization of the experimental conditions is carried out in the neural network with 5-5-1 structure, which have been confirmed to be able to provide the maximum performance. In contrast to traditional methods, the use of this methodology has advantages in terms of a reduction in analysis time and an improvement in the ability of optimization. Under the optimum experimental conditions, Ru (III) can be determined in the range 0.040 0.60 µg mL-1 with detection limit of 0.03 µg mL-1 and the sampling frequency of 34 h-1. The method has been applied to the determination of Ru (III) in refined ore as well as in secondary alloy and provided satisfactory results. (C) 2001 Elsevier Science B.V. All rights reserved.
Ruthenium(III) Refined Alloy Spectrophotometry

"Determination Of Pd(II) By Application Of An On-line Microwave Oven And Artificial Neural Networks In Flow Injection Analysis"
Anal. Chim. Acta 2000 Volume 420, Issue 1 Pages 123-131
Sun Gang, Chen Xingguo, Zhao Yunkun, Liu Mancang and Hu Zhide

Abstract: A new methodology based on the coupling of an on-line microwave oven, employed to accelerate low-rate reactions, and artificial neural networks (ANNs), applied to the modeling and optimization of a new flow injection system, is proposed. In comparison with traditional heating, a microwave can accelerate low-rate reactions more remarkably and consume less energy. ANNs with a faster back-propagation (BP) algorithm are applied to model the system. Optimum experimental conditions are generated automatically by using jointly ANNs and optimization algorithms in terms of sensitivity, sampling rate and the energy consumed by a microwave oven. The methodology is tested on a new flow injection system for the spectrophotometric determination of Pd(II) with chlorophosphonazo-p-Cl (CPA-pC) in H2SO4 media, which has first been used as chromogenic reagent in the quantitative analysis of palladium. It is shown that the methodology can improve the ability of optimization, reduce analytical time, enhance sensitivity and consume less energy in comparison with traditional methods.
Palladium(II) Geological Industrial Spectrophotometry

"A Factorial Design For Optimizing A Flow Injection Analysis System"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 2 Pages 201-203
J. R. Luna, J. F. Ovalles, A. Le&oacute;n, M. Buchheister

Abstract: The use of a factorial design for the response exploration of a flow injection (FI) system is described and illustrated by Fl spectrophotometric determination of paraquat. Variable response (absorbance) is explored as a function of the factors flow rate and length of the reaction coil. The present study was found to be useful to detect and estimate any interaction among the factors that may affect the optimal conditions for the maximal response in the optimization of the FI system, which is not possible with a univariate design. Ln addition, this study showed that factorial experiments enable economy of experimentation and yield results of high precision due to the use of the whole data for calculating the effects.

"A Flow Injection (FI) Biosensor System For Pentachlorophenol (PCP) Using A Substrate Recycling Scheme"
Environ. Sci. Technol. 2000 Volume 34, Issue 15 Pages 3291-3295
Marietta Labra-Espina, Keith B. Male, and John H. T. Luong

Abstract: A flow injection (FI) biosensor system has been designed for the analysis of pentachlorophenol (PCP) using a substrate recycling scheme comprising immobilized bilirubin oxidase (BOX) in the presence of excess of NADH. PCP was efficiently converted to tetrachloro-p-benzoquinone (1,4-TCHQ) and then tetrachloro-p-hydroquinone (1,4-TCHQ) by bis(trifluoroacetoxy)iodobenzene (BTFAIB) and zinc powder, respectively. BOX immobilized on aminopropyl glass beads rapidly oxidized 1,4-TCHQ to 1,4-TCBQ, which in turn was readily reduced back to 1,4-TCHQ in the presence of excess NADH. This recycling scheme enabled one molecule of PCP to consume several NADH molecules leading to enhanced sensitivity. tinder optimized conditions the rate of NADH uptake measured as the absorbance decrease at 340 nm yielded a detection limit for 1,4-TCHQ or oxidized PCP of 250 nM. The detection limit was improved to 25 nM for both analytes using a fluorescence detector with excitation and emission wavelengths of 345 and 450 nm, respectively. The PCP level in contaminated soil samples was measured using the Fl biosensor system, and the results obtained compared well with capillary zone electrophoresis (CZE) analysis.

"Amperometric Determination Of Se(IV) With On Line Preconcentration By Flow Injection Anlysis"
Bol. Soc. Chilena Quim. 2000 Volume 45, Issue 1 Pages 99-107
M.A. Machuca, I. De Gregori and H. Pinochet

Abstract: The experimental conditions for the indirect amperometric detection of Se(IV) by flow injection analysis have been optimized. The method is based on the Se(IV) reduction to Se(0) in acid medium in presence of an excess of iodide, being generated yotrion species which is electroactive and amperometrically detected at vitreous carbon electrode. The signal depends on the quantity of Se(IV) in the samples. Under optimized conditions, analytical conditions of the method were determined. The detection and quantification limits were 4.8 µg L-1 and 15.9 µg L-1, respectively. Because of the method proposed for its application to the determination of Se(IV) in natural water samples, it became necessary to increase the detection sensitivity and an on-line concentration stage was coupled. This stage is carried out on an anionic resin exchange (Dowex 1-X8). The detection and the quantification limits were in this case 0.06 µg L-1 and 0.2 µg L-1, respectively. The online pre-concentration stage increases the sensibility of the amperometric detection which allows the Se(IV) determination at µg L-1 levels.
Selenium(IV) Environmental Amperometry Electrode

"New Electrochemical Assay Of Alkaline Phosphatase Using Ascorbic Acid 2-phosphate And Its Application To Enzyme Immunoassay"
Anal. Chim. Acta 2000 Volume 407, Issue 1-2 Pages 119-125
Amane Kokado, Hidetoshi Arakawa and Masako Maeda

Abstract: An alternative substrate is described for an enzyme immunoassay with electrochemical detection, Alkaline phosphatase (ALP) activity is determined by using ascorbic acid 2-phosphate (AsA-P) as substrate. ALP-generated-AsA is detected amperometrically at a glassy carbon electrode in a flow injection system at +400 mV. The optimum assay conditions (pH, incubation time and concentration of reagent) are examined for the ALP assay. The detection limit of ALP was 160 amol per assay (7 amol per injection). On electrochemical detection, many ALP assays using p-aminophenyl phosphate or phenyl phosphate as substrate have been reported. The sensitivity for ALP by the proposed method is almost the same as those of the methods for ALP using p-aminophenyl phosphate or phenyl phosphate. The proposed method was applied to the enzyme immunoassay of human chorionic gonadotropin (hCG) using ALP as a label enzyme. The detection limit of hCG was 2 mIU mL-1. Comparison of the results obtained by the proposed electrochemical EIA and time-resolved fluoroimmunoassay showed excellent agreement (r = 0.997, n = 50). The proposed electrochemical EIA could be performed within 4 h. and could be useful for routine assay in clinical diagnosis.
Enzyme, alkaline phosphatase Immunoassay Amperometry Electrode Clinical analysis

"Quantitation Of Intracellular Recombinant Human Superoxide Dismutase Using Surface Plasmon Resonance"
Anal. Chim. Acta 2002 Volume 456, Issue 2 Pages 193-200
Daniel Ivansson, Karl Bayer and Carl-Fredrik Mandenius

Abstract: An immunosensor assay for the quantitation of intracellular recombinant human superoxide dismutase (rhSOD) in Escherichia coli cultivations based on detection with surface plasmon resoance (SPR) is described. A monoclonal antibody for rhSOD was immobilized on a SPR dextran gold chip. Bacterial samples were sonicated and centrifugated prior to injection over the antibody chip for SPR detection. The assay time was 7 min and allowed quantitation in the range of 1-64 nM SOD in lysate samples with a precision of 1.1-3.4%. The assay was applied to monitor the concentration of rhSOD during E. coli bioreactor cultivations where the rhSOD production was induced by iso-propyl-b-D-thiogalactoside (IPTG). The assay allowed accurate monitoring of the production of rhSOD where the important phases in the product formation were possible to see. The report also discusses influence from sample preparation, SPR selectivity and sensitivity and quantitation limits. The assay proved to be fast, sensitive and accurate with low background effects from the dextran matrix of the SPR chip.

"Amperometric On-line Sensor For Continuous Measurement Of Hypoxanthine Based On Osmium-polyvinylpyridine Gel Polymer And Xanthine Oxidase Bienzyme Modified Glassy Carbon Electrode"
Anal. Chim. Acta 2000 Volume 415, Issue 1-2 Pages 143-150
Lanqun Mao and Katsunobu Yamamoto

Abstract: Osmium-polyvinylpyridine gel polymer (Os-gel-horseradish peroxide (HRP)) and xanthine oxidase (XOD) bienzyme-based amperometric biosensor was developed for use in a thin-layer radial flow cell for on-line measurement of hypoxanthine. Glassy carbon electrodes (GCEs) were initially cast-coated with Os-gel-HRP with a surface coverage of 7.1 µl/cm(2) to sense hydrogen peroxide produced from XOD catalytic enzyme reaction based on HRP catalytic reduction mediated by osmium, Then, bovine serum albumin (BSA)/XOD was cross-linked to the Os-gel-HRP-coated glassy carbon electrodes (GCEs) with glutaraldehyde vapor for the measurement of hypoxanthine at 0.0 mV (versus Ag/AgCl). The resultant HRP and XOD bienzyme-based sensors (Os-gel-HRP/XOD/GCEs) were tested with techniques of cyclic voltammetry (CV), on-line amperometry in a flow system and flow injection analysis (FIA). In continuous-flow amperometric experiments, the Os-gel-HRP/XOD/GCEs were quick to stabilize background current and show linear and sensitive response towards hypoxanthine in a concentration range from 0.5 to 80 µM with a detection limit of 0.2 µM (S/N=3). The specificity against ascorbic acid was enhanced by negatively shifting the operating potential to -200 mV versus Ag/AgCl and was demonstrated to be acceptable for on-line performance. The interference from higher than physiological levels of dopamine (DA), norepinephrine (NE), serotonin, their principal metabolites and uric acid was minimal. The dependency of sensor response on pH value of the buffer and operating potential was also tested and optimized.
Hypoxanthine Amperometry Electrode Electrode

"On-line Preconcentration System For Vanadium Determination In Drinking Water Using Flow Injection-inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Chim. Acta 2000 Volume 420, Issue 1 Pages 73-79
R. G. Wuilloud, J. A. Salonia, J. A. G&aacute;squez, R. A. Olsina and L. D. Martinez

Abstract: An on-line vanadium a pre-concentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated to low flow injection (FI) was studied. For the retention of vanadium, 2- (5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br- PADAP) and Amberlite XAD-7 were used, at pH 3.7. The vanadium was removed from the mcirocolumn in countercurrent with nitric acid. An enrichment factor (EF) of 75 was obtained. The detection limit value for the pre-concentration of 50 mL of aqueous solution of vanadium was 0.04 µgl-1. The precision for 10 replicate determinations at the 5 µg L-1 vanadium levels was 2.5% relative standard deviation (R.S.D), calculated with the peak heights obtained. The calibration graph using the pre-concentration system for vanadium was linear with a correlation coefficient of 0.9996 at levels near the detection limited up to at least 50 µgl-1. The method was successfully applied to the determination of vanadium in drinking water samples.
Vanadium Water NIST 1640 Spectrophotometry

"Spectrophotometric Determination Of Ozone In Ozonized Air Currents With Chemical Gas-liquid Transfer Using A Microreactor"
Anal. Chim. Acta 1999 Volume 380, Issue 1 Pages 93-99
&Ecirc;nio L. Machado, Marcelo B. da Rosa, &Eacute;rico M. M. Flores, Jos&eacute; N. G. Paniz and Ayrton F. Martins

Abstract: The spectrophotometric determination of ozone by measurement of its corresponding iodine-starch complex at 580 nm was realized using a flow injection system with chemical gas-liquid transfer microreactor. The flow injection system with a gas-liquid transfer microreactor (Vigreux type microcolumn, 500 µl) was designed to use a reagent solution (1% (m/v) potassium iodide, 0.1 mol L-1 boric acid, and 1% (m/v) starch) for ozonization at low residence time. Ozonizated air currents were constantly passed through a sampling loop at various flow rates, and then injected by countercurrent in the microreactor to ozonizate the reagent solution. The volume of the ozonizated air sampling loop was 32 mi, and 500 µl for the reagent solution. The best results were: ozone chemical/physical transference of 95%, an output rate of 120 samples per hour, a detection limit of (3 s)=0.4 mg O-3 L-1, a work range from 0.4 to 10.6 mg O(3)l-1, and a relative standard deviation of 1.7 (n=5, 1.2 mg O-3 l-1). Ozone production rate (mg O-3 h-1) was determined from a homemade ozonizator (3 kV, air as feed gas), and ozone off-gas from ozonization of agrochemical factory wastewater. Using this procedure, several problems of gas phase ozone determination were surpassed: low output rate, excessive handling, and high consumption of the reagent solution. Additionally, direct ozone sampling by flow injection system was made possible.
Ozone Water Spectrophotometry

"Development And Optimisation Of A Flow Injection Assay For Fluticasone Propionate Using An Asymmetrical Design And The Variable-size Simplex Algorithm"
J. Pharm. Biomed. Anal. 2000 Volume 23, Issue 2-3 Pages 291-306
C. Vannecke, A. Nguyen Minh Nguyet, M. S. Bloomfield, A. J. Staple, Y. Vander Heyden and D. L. Massart

Abstract: A flow injection analysis method is described to determine fluticasone propionate, based upon a novel adaptation of the reaction of o-phthalaldehyde with a thiol and a primary amine. The method, which allows both UV and fluorescence detection, has been optimized using experimental design. First a screening is executed to select the significant factors acid in a second step these factors are optimized with the variable-size simplex algorithm. In the screening step, a two-level fractional factorial design is compared with an asymmetrical design containing the same number of experiments, but in which one factor is at three levels. It was found that in both designs the same significant variables are detected for the two-level factors, but that for the three-level factor the asymmetrical design confirms an expectation of having a (local) optimum in the examined domain, whilst from the two-level design this is not at all apparent. Complete optimization was carried out for both UV and fluorescence detection. The two detection methods did not have the same significant variables. For the UV detection, the temperature and the pH adjustment on-line (concentration of sodium hydroxide and amount of boric acid) were the most critical parameters. For the fluorimetric detection the temperature and the fraction of methanol were critical. Moreover the conditions found to be optimal are different for both detection methods.

"Sensitive Determination Of Antimony In Steels By High Power Nitrogen Microwave Induced Plasma Atomic Emission Spectrometry Coupled With Hydride Generation Technique"
J. Iron Steel Inst. Jpn. 2001 Volume 87, Issue 6 Pages 449-453
Akihiro Matsumoto, Atsuyoshi Oheda, Taketoshi Nakahara

Abstract: The feasibility of an annular-shaped high power nitrogen microwave induced plasma (N-2-MIP) atomic emission spectrometry (AES) has been studied for the determination of antimony in combination with hydride evolution method. Under the optimized experimental conditions, the best attainable detection limits at Sb I 231.147 nm line by use of N-2-MIP-AES coupled with hydride generation technique was 1.87 ng Sb/ml with a linear dynamic range of 5 to 10,000 ng Sb/ml. The presence of several diverse elements was found to cause more or less a depressing interference with the determination of antimony by the present technique. Of the several pre-reductants examined L-cysteine was found to be the most preferable to reduce Sb5- to Sb3+ prior to hydride generation. Therefore, L-cysteine was utilized as a pre-reductant for the determination of total antimony, i.e., Sb3+ + Sb5+. When antimony in steels was determined a large amount of Fe3+ in the solution caused a severe depressing interference with the antimony determination, while the presence of Fe2+ showed little or no significant interference. Of the several interference-releasing agents examined L-cysteine was found to be the most preferable to reduce Fe3+ to Fe2+. The proposed method using L-cysteine not only as a pre-reductant but also as an interference-releasing agent was applied to the determination of low concentrations of antimony in carbon steels. The results obtained by this method were in good agreement with the certified values.

"Flow Injection Fluorometric Quantification Of Succinate In Foodstuffs Based On The Use Of An Immobilized Enzyme Reactor"
Anal. Chim. Acta 2000 Volume 416, Issue 2 Pages 197-203
Tadayuki Tsukatani and Kiyoshi Matsumoto

Abstract: A method for the quantification of succinate by flow injection analysis was developed using an immobilized-enzyme reactor and a fluorescence detection. Succinate was quantified using a co-immobilized isocitrate lyase (ICL) and isocitrate dehydrogenase (ICDH) reactor. Succinate was converted to isocitrate by ICL in the presence of glyoxylate, and then the produced isocitrate was oxidized with NADP(+) by ICDH. The NADPH produced by the ICL-ICDH reactor was monitored fluorometrically at 455 nm (excitation at 340 nm). A linear relationship between sensor responses and concentration of succinate was obtained in the range of 5-200 µM. The relative standard deviation for 10 successive injections was 1.01% at the 200 µM level. This analytical method was applied to the quantification of succinate in shellfishes and Japanese sakes, and the results showed good agreement with those obtained using conventional method (F-kit method).
Succinate Clam Arkshell Corb shell Clam Shortneck Sake Fluorescence

"Preconcentration And Speciation Of Chromium In Waters Using Solid-phase Extraction And Atomic Absorption Spectrometry"
Talanta 2000 Volume 51, Issue 3 Pages 531-536
D. M. Adri&aacute;-Cerezo, M. Llobat-Estell&eacute;s and A. R. Maur&iacute;-Aucejo

Abstract: A method for the pre-concentration and speciation of chromium was developed. After formation of an anionic compound with ethylenediaminetetraacetic acid (CrY-), Cr (VI) and Cr (III) are retained on a strong anionic phase (SAX) and controlled elution with 0.5 M NaCl permits their speciation. The retention and elution conditions were optimized, and interferences due to the presence of other ions such as Mg(II), Mn(lI), Sn(II), Fe(III), Ba(II), Al(III), Ca(II), chloride, iodine, bromide, fluoride, sulfate, phosphate, bicarbonate and nitrate were studied. The detection limits were 0.4 µg L-1 and 1.1 µg L-1 for Cr(III) and Cr(VI), respectively, and reproducibility was 9%. The results obtained for speciation of chromium by the proposed method in wastewaters are in agreement with the values obtained by a reference method for a 95% confidence level.
Chromium(III) Chromium(VI) Waste Spectrophotometry

"A Novel Flow-through Disk-based Solid-phase Extraction Diffuse Reflectance Optrode. Application To Preconcentration And Determination Of Trace Levels Of Nitrite"
Analyst 2001 Volume 126, Issue 10 Pages 1740-1746
Manuel Mir&oacute;, Wolfgang Frenzel, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: A novel, versatile and sensitive flow-through optical fiber diffuse reflectance sensor to implement disk-based solid-phase extraction in a flow injection analysis (FIA) system is presented. Nitrite optosensing at trace levels is chosen as a model of chemistry to demonstrate its applicability. The methodology is based on on-line nitrite derivatization with Shinn reagent to form a moderately polar azo dye, whose pre-concentration oil to octadecyl covalently bonded silica gel particles tightly bound to an inert matrix (C-18 disk) is continuously monitored using a plug-in diode-array spectrophotometer. After the analytical signal has been recorded, fast sensor regeneration is achieved with a methanolic eluent, rendering the system ready for the next extraction. Selection of the solid disk support and the suitable flow-through cell configuration to reduce back-pressure effects are discussed in detail. By matching the illumination and retention zones, concentrations of nitrite as low as 1 ng mL-1 are easily determined using 2.5 mL of sample. A detection limit (3s (blank)) of 0.1 ng mL-1 of nitrite, repeatability and reproducibility better than 3.2%, an analytical throughput of 11 h-1 and an enrichment factor of 140 are the figures of merit of the proposed optrode. The utility of the flow-through optosensing system, wherein minimization of additive matrix interferences is feasible, was testified by the satisfactory results obtained in its application to tap, ground, harbor and aquarium water samples.
Nitro compounds Ground Estuarine Water Water Sensor Spectrophotometry Optrode

"Determination Of Chromium In Human Lung Fibroblast Cells Using A Large Bore-direct Injection High-efficiency Nebulizer With Inductively Coupled Plasma Mass Spectrometry"
Appl. Spectrosc. 2000 Volume 54, Issue 5 Pages 659-663
John A. McLean, Billy W. Acon, Akbar Montaser, Jatinder Singh, Daryl E. Pritchard, and Steven R. Patierno

Abstract: A novel method for the determination of chromium in suspensions of human lung fibroblast cells is described by using a large bore-direct injection high efficiency nebulizer (LB-DIHEN) with microscale how injection analysis and inductively coupled plasma mass spectrometric detection, Chromium(VI)-treated cells were first counted and then suspended in a phosphate buffer saline solution, With the use of the method of standard additions, the relative concentration of Cr in similar to 100 HLF cells/peak was determined at m/z = 50. Because the cells tend to clump and can yield inhomogeneities in the total number analyzed, Mg was used as an internal standard to compensate for the total cell mass. The level of Cr in HLF cells grown in a medium of 100 µM Na2CrO4 for two hours Is on the order of 180 fg Cr/cell after correction for the number of cells in each injection.

"Multivariate Optimisation Of Hydride Generation Procedures For Single Element Determinations Of As, Cd, Sb And Se In Natural Waters By Electrothermal Atomic Absorption Spectrometry"
Talanta 2001 Volume 53, Issue 4 Pages 871-883
Jorge Moreda-Pi&ntilde;eiro, Carmen Moscoso-P&eacute;rez, 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: Continuous flow hydride generation procedures for As(III), total inorganic As, Cd, total inorganic Sb, Se(IV) and total inorganic Se from sea and hot-spring water samples were optimized by experimental designs. Ir-coated graphite tubes were used as pre-concentration and atomisation medium of the hydrides generated. Several factors affecting the hydride generation efficiency were studied. Results obtained from Plackett-Burman designs suggest that sodium borohydride flow rate and reduction coil length, are significant factors for total inorganic arsenic hydride generation. For cadmium hydride generation the significant factors are hydrochloric acid concentration, hydrochloric acid and sodium borohydride flow rates and reduction coil length. For total inorganic antimony hydride generation the factors affecting the hydride generation procedure are hydrochloric acid and potassium iodide concentrations and reduction coil length; finally, pre-reduction coil length and oven temperature for the pre-reduction step are statistically significant factors for total inorganic selenium hydride generation. In addition, the factors studied for the arsenic and selenium hydride generation from As(III) and Se(IV) are not significant. From these studies, the sinificant variables were optimized by central composite designs. Validation carried out analysis on three reference materials: SLRS-4 (Riverie water), CASS-3 (seawater) and NIST-1643d. (C) 2001 Elsevier Science B.V. All rights reserved.

"A Simple Procedure To Improve The Analytical Performance Of Flow Injection Systems"
Spectrosc. Lett. 2002 Volume 35, Issue 5 Pages 715-728
Antonio Tovar, Carlos Moreno, Manuel P. M&aacute;nuel-Vez, Manuel Garc&iacute;a-Vargas

Abstract: The optimization of flow injection analysis (FIA) manifolds is usually performed with the univariate procedure, although in many cases they do not allow to find optimum conditions due to the interaction errors caused by the interdependence between variables. However, many authors prefer the univariate methodology instead of the more correct multivariate methods, probably due to the higher theoretical difficulty of the latter. In this work we demonstrate that by applying a very simple multivariate procedure, the results obtained are better than those obtained by using the univariate optimization. To illustrate this, the conditions for a FIA manifold used for the determination of phosphates 4 in natural water has been studied by using two different procedures: the classical univariate method and a second one based on experimental design. Experimental design procedures take into account the interactions between the variables optimized, which are ignored by univariate procedures. The classical univariate procedure found experimental conditions that produced less precise and accurate results (RSD = 13.6%; epsilon(r) = 11.1 %) than those obtained when the performance of FIA system was studied with the simpler method based on 2(n) experimental design (RSD = 4.2%; epsilon(r) = 6.3%). Sensitivity was also improved and lower limits of detection were obtained with experimental design (river water: 5.6 µg L-1; seawater: 5.9 µg L-1) than with the univariate methodology (river water: 87.1 µg L-1; seawater: 88.9 µg L-1). Besides, the use of experimental design allowed reducing both waste production and cost of analysis.

"Sensitive Flow Injection Colorimetry Of Nitrite By Catalytic Coupling Of N-phenyl-p-phenylenediamine With N,N-dimethylaniline"
Talanta 1999 Volume 48, Issue 1 Pages 103-107
Ryoichi Kadowaki, Shigenori Nakano and Takuji Kawashima

Abstract: A rapid, sensitive and selective flow injection colorimetry method is proposed for the determination of trace amounts of nitrite. It is based on the nitrites catalytic effect on the oxidative coupling of N-phenyl-p-phenylenediamine with N,N-dimethylaniline to produce a green dye (lambda(max) = 735 nm) in the presence of bromate. The change in absorbances of the dye were monitored in continuous flow mode. Linear calibration curves were obtained for the nitrite concentration range 2.0-100 ng mL-1. The proposed method had a low detection limit (0.6 ng ml-1) and high sample throughput (approximately 30 samples h-1). The RSD for 10 and 50 ng mL-1 nitrite were 2.4 and 1.3% (n = 10). respectively. The method has been successfully applied to the determination of nitrite in river water samples.
Nitrite River Spectrophotometry

"Determination Of Arsenite, Arsenate, And Monomethylarsonic Acid In Seawater By Ion-exclusion Chromatography Combined With Inductively Coupled Plasma Mass Spectrometry Using Reaction Cell And Hydride Generation Techniques"
Talanta 2002 Volume 58, Issue 1 Pages 121-132
Tetsuya Nakazato, Hiroaki Tao, Tadashi Taniguchi and Kenji Isshiki

Abstract: This paper describes a robust and sensitive method for the determination of arsenic species in seawater by ion-exclusion liquid chromatography (LC) combined with inductively coupled plasma mass spectrometry (ICP-MS) using reaction cell and hydride generation (HG) techniques. A good separation of arsenite, arsenate, and monomethylarsonic acid was achieved using an ion-exclusion column packed with a sulfonated polystyrene resin and a dilute nitric acid at pH 2.0 as the eluent, even when a large volume, i.e. 200 µL, of seawater samples containing a large amount of matrix was repeatedly injected. Separations of the chloride ion due to the matrix and arsenic species were partially performed; however, the extensive peak of ArCl due to high content of Cl- in a sample overlapped peaks of the three arsenic species on As-75 measurement by ICP-MS. This ArCl polyatomic interference was efficiently eliminated by collision of ArCl molecules with helium in an octopole reaction cell which was introduced prior to a mass spectrometer. Detection limits of the three arsenic species in a sample containing 2% Cl-, the concentration of which is comparable to that in a seawater sample, by LC-ICP-MS with the octopole reaction system (ORS), ranged from 21 to 25 pg As ml-1; these values were three-six times lower than those by LC-ICP-MS without ORS. As another technique for ArCl interference elimination, HG prior to ICP-MS was also successfully used not only to reduce the interference but also to improve the detection limits to 3.4-4.5 pg As mL-1. The developed LC-ICP-ORS-MS and LC-HG-ICP-MS were validated by analyzing a certified reference material (CRM) of seawater. In addition, no serious decrease in analytical performance of present methods was observed in the experimental periods of half a year for LC-ICP-ORS-MS and 1 year for LC-HG-ICP-MS, respectively. The latter method was successfully applied to characterize seasonal variations of three arsenic species in deep seawater and surface seawater. (C) 2002 Elsevier Science B.V. All rights reserved.

"Vanillin-condensed Tannin Study Using Flow Injection Spectrophotometry"
Talanta 2000 Volume 51, Issue 1 Pages 1-6
Edilene C. Ferreira and Ana Rita A. Nogueira

Abstract: Studies involving the kinetic reaction between vanillin and condensed tannins were developed using a flow injection system with spectrophotometric determination. A solution of the monomeric compound (-)-epicatechin was used as the analytical standard. This compound was chosen due to its structure, which is similar to a polymeric unit of the condensed tannin present in plants. The results indicated that the vanillin-condensed tannin reaction is time dependent and affected by the degree of polymerization of the condensed tannin. The flow system allowed (-)-epicatechin to be used without overestimating the content of the tannin present in the forage legume, guandu (Cajanus cajan (L.) Millsp.), studied. A relative standard deviation (RSD) of <1% was found for a 4 h period work and allowed the determination of about 60 samples h-1 with a detection limit of 1.05 mg L-1 for condensed tannin. When compared to the manual vanillin procedure, the proposed approach can be used with various advantages.
Vanillin Guandu Seed Spectrophotometry

"Determination Of Optimal Conditions To Achieve Maximal Response At Maximal Repeatability In FIA-AMZ Experiment Through A Mathematical Modelling Approach"
Croat. Chem. Acta 2002 Volume 75, Issue 2 Pages 531-543
Milko Novic and Marjana Novic

Abstract: The determination of optimal experimental conditions in flow injection analysis asynchronous merging zone technique (FIA-AMZ) on the basis of a mathematical model is proposed. An improved commutator enabling reagent addition with minimal frontal dispersion is used for the simultaneous determination of two species, Fe2+ and Fe3+ ions. The mathematical model used to simulate the detector response is based on a bell-shaped function. The model is well suited for the fitting of symmetrical as well as for very asymmetrical detector responses, reflecting different dispersion of the sample plugs. The influence of the frontal dispersion of the reagent, asymmetrically added to the sample plug, is studied using the proposed model. A measure for an optimal ratio between the sensitivity and repeatability is described on the basis of the parameters obtained from the simulations of the experimental curves obtained for different dispersions.

"An Electrochemical Flow-cell For Permanent Modification Of Graphite Tube With Palladium For Mercury Determination By Electrothermal Atomic Absorption Spectrometry"
Spectrochim. Acta B 2002 Volume 57, Issue 4 Pages 769-778
Ruben G. M. Moreno, Elisabeth de Oliveira, Jairo J. Pedrotti and Pedro V. Oliveira

Abstract: An electrochemical procedure for palladium deposition on the inner surface of pyrolytic graphite-coated tubes for permanent chemical modification and a cold vapor generation system for the pre-concentration and determination of mercury trace levels in rain, potable, and non-potable water and lake sediment by electrothermal atomic absorption spectrometry is proposed. A tubular electrochemical flow-cell was assembled on the original geometry of the graphite tube, which operated as the working electrode. A stainless steel tube, positioned downstream from the working electrode. was used as the auxiliary electrode. The applied potential was measured against a µAg/AgCl(sat) reference electrode inserted in the auxiliary electrode. Palladium solution in acetate buffer (100 mmol L-1, pH=4.8)9 flowing at 0.5 mL min-1 for 60 min was used to perform the electrodeposition. A homemade cold vapor generation system composed of a peristaltic pump, an injector-commutator, a flow meter and a disposable polyethylene gas-liquid separator flask (~4.0 mL volume) were used. Volumes of 1.0 mL of reagent (2.0% (w/v) NaBH4 in 0.10 mol L-1 of NaOH) and 1.0 mL of reference or sample solution in 0.25 mol L-1 of HNO3 were carried to the gas/liquid separator using the peristaltic pump. The mercury vapor was carried out to the modified graphite tube by argon flow (200 mL min-1), and pre-concentrated for 120 s. The characteristic mass for 1.0 mL of reference solution was 26 pg (RSD=0.12%, n=5). The detection limit obtained was 93 pg (n=20, 38). The reliability of the entire procedure was confirmed by addition and recovery tests and cold vapor atomic absorption spectrometry.

"Determination Of Trace Levels Of Dissolved Vanadium In Seawater By Use Of Synthetic Complexing Agents And Inductively Coupled Plasma-atomic Emission Spectroscopy (ICP-AES)"
Anal. Bioanal. Chem. 2002 Volume 374, Issue 5 Pages 873-878
Ghiasse Abbasse, Baghdad Ouddane, Jean Claude Fischer

Abstract: In the determination of traces of dissolved vanadium in complex matrices such as seawater, separation and enrichment from the matrix is of special importance. A wide variety of methods has been proposed for pre-concentration, depending to the nature of samples and the methods to be used for measurement. Among these methods separation techniques based on sorption on to chelating resins seem convenient, rapid and capable of achieving a high concentration factor. The methods proposed in this paper are based on the transformation of all dissolved vanadium species in seawater into organic complexes by use of synthetic complexing agents such as dithizone, luminol, or 8-hydroxyquinoline; the resulting vanadium-organic complexes were sorbed on to a C-18 column at a flow rate of 5 mL min^-1. The vanadium sorbed on the C-18 columns was then stripped by use of nitric acid (2 mol L^-1) and analyzed by inductively coupled plasma-atomic emission spectroscopy, ICP-AES. This method was optimized and use of other chelating resins, such as chelamine, chelex-100, and immobilized 8-hydroxyquinoline and was compared by passing seawater samples directly over the resins. The experimental conditions (pH, acid used for elution, and contact time between the liquid sample and the resin) were optimized. The results were compared for all the resins used and were indicative of excellent and coherent reproducibility.
Vanadium Sea Spectrophotometry

"Lead Determination With On-line Enrichment System"
Water Res. 2000 Volume 34, Issue 17 Pages 4215-4219
Krystyna Pyrzynska and Mihaela Cheregi

Abstract: The flow injection pre-concentration system with a cellulose sorbent was developed to determine trace; mounts of lead. The metal was pre-concentrated on a microcolumn packed with Cellex P, cellulose sorbent with phosphonic acid groups, and eluted with nitric acid into the nebuliser-burner system of atomic absorption spectrometer. An enrichment factor of 47-197, equivalent of 5.1-25.5 mL of sample, was achieved by using time-based system. The detection limit (3 delta) for 1 min pre-concentration time was 1.8 µg L-1 and precision (at 10 µg L-1 level) was 7.8% (RSD). The method was applied to the determination of lead in natural water samples.
Lead River Spectrophotometry

"The Analytical Characterisation Of Sub-minute Measurement Duty Cycles In Flow Injection Analysis Mass Spectrometry, By Their Carry-over"
Anal. Chim. Acta 2000 Volume 403, Issue 1-2 Pages 287-294
Ramsay Richmond

Abstract: A high-throughput flow injection analysis mass spectrometry system was developed in-house for the purity estimation of multiple parallel combinatorial chemistry syntheses. A Visual Basic application called RackViewer allows a fast and easy on-screen inspection of these estimates at dispersed laboratory workbenches via the corporate computer network. Due to the increasing numbers of samples to be measured, there is an constant incentive to reduce the measurement duty cycle in order to develop faster throughput rates. Consequently, one threat to the accuracy of these purity estimates is surreptitious inter-sample carry-over. By analogy with the computer screen color rendering of the purity estimates, carry-over was automatically calculated, then color depicted within RackViewer. In an earlier report, this carry-over visualisation tool facilitated a stepwise reduction in the measurement duty cycle to 70 s, while maintaining median inter-sample carry-over at levels well below 1%. However, a limiting factor in further optimization was the physical speed of the autosamplers sampling head. A recent increase in this speed by the autosamplers manufacturer allowed a second attempt at achieving well characterized sub-minute measurement duty cycles. Six injection variations involving different syringe and loop wash combinations were examined for their characteristic inter-sample carry-over, using over four hundred samples drawn equally from five diverse combinatorial chemistries. One emerged as the best, with a median inter-sample carry-over of 0.01% and a measurement duty cycle of 44 s.
Mass spectrometry

"Continuous Liquid-liquid Extraction System With A Sandwich Type Phase Separator For The Determination Of Copper As The Copper(I)-bathocuproine Complex"
Bol. Soc. Chilena Quim. 1999 Volume 44, Issue 4 Pages 451-458
RICHTER, PABLO, TORAL, M. INES and MANRIQUEZ, ROBERTO

Abstract: In this work a method for determination of copper at low concentration levels is proposed by using a continuous flow manifold in which the liquid-liquid extraction step for extracting the copper from the aqueous matrix is automated. The analyte is transferred into 1,2 dichloroethane as the colored complex Cu(I)-bathocuproine-counter ion. The manifold also contains a sandwich type membrane separator which is used after the extraction process. This phase separator provides the channel of the outlet organic stream free of aqueous phase, thus avoiding the interference with the transiently detection process at 478 nm. By keeping the chemical and hydrodynamic variables of the method in the optimal condition, it was found that copper can be determined from 64.5 ng/mL to 4000 ng/mL, with a detection limit of 19.3 ng/mL. The repeatability of the method for concentrations of 200 and 1000 ng/mL, expressed as variation coefficient, were of 3.77% and 1.08%, respectively The sampling rate was 22 h-1. The accuracy of the method was tested by using the certified reference material for elements in waters GBW 08607. The relative error between the found and the certified value was + 2.9%.
Copper NRC GBW 08607 Spectrophotometry

"Determination Of Arsenic Species In Oyster Tissue By Microwave-assisted Extraction And Liquid Chromatography-atomic Fluorescence Detection"
Appl. Organomet. Chem. 2001 Volume 15, Issue 8 Pages 658-666
Marc Vilan&oacute;, Roser Rubio

Abstract: A method for the determination of arsenic species in oyster tissue is established. The extraction of arsenic species is carried out by using low-power microwaves. Quantitative extraction is obtained at a power of 40 W, and in 5 min, using the extracting agent methanol/water (I + 1). The measurements are carried out using liquid chromatography-UV irradiation-hydride generation-atomic fluorescence detection (LC-UV-HG-AFS). Three arsenic species were detected in oyster tissue: arsenobetaine (AsBet) (87%), a probable arsenosugar (AsS) (4.9%), and dimethylarsinate (DMA) (4.7%). No influence of the clean-up, the microwave field or the IR drying system on the stability of the arsenic compounds was observed. The extracts can be kept stable up to 3 days at 4°C. The performance of the method is proved on fresh samples, as they are usually analyzed in routine laboratories.

"Spectrofluorimetric Kinetic Determination Of Selenium (IV) By Flow Injection Analysis In Cationic Micellar Medium"
Talanta 2000 Volume 51, Issue 2 Pages 225-230
Afsaneh Safavi and Mohammad Mirzaee

Abstract: A sensitive catalytic kinetic spectrofluorimetric method for determining ng mL-1 of selenium by flow injection analysis has been developed. The method, based on the catalytic effect of Se (IV) on the reduction of resorufin by sulfide, in the presence of cetylpyridinium chloride, is monitored spectrofluorimetrically (lambda(ex) = 480 nm; lambda(em) = 583 nm). The linearity range of the calibration graph is dependent on the concentration of sulfide. The variables affecting the rate of the reaction were investigated.:The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 1 ng mL-1 Se (IV), and the calibration range is 5-1000 ng mL-1. Sampling rate is 60 samples hr-1, and the relative standard deviation of 12 determinations of 100 ng mL-1 Se was 0.76%. The determination of Se (IV) in the presence of Se (VI) and total selenium is described. The method was applied to the determination of Se in selenium tablets, and several synthetic samples.
Selenium(IV) Selenium, total Pharmaceutical Fluorescence

"An Online Solid Phase Extraction System Using Polyurethane Foam For The Spectrophotometric Determination Of Nickel In Silicates And Alloys"
Anal. Chim. Acta 1999 Volume 378, Issue 1-3 Pages 287-292
S&eacute;rgio Luis Costa Ferreira, Djane Santiago de Jesus, Ricardo Jorgensen Cassella, Antonio Celso Spinola Costa, Marcelo Souza de Carvalho and Ricardo Erthal Santelli

Abstract: The present paper describes the use of a solid phase extraction system using a polyurethane foam (PUF) minicolumn, in order to separate nickel from interferences due to other elements and determine it by flow injection analysis with spectrophotometric detection. Separation is based on the retention of thiocyanate complexes of interferent ions in the PUF minicolumn. Nickel does not form complex with thiocyanate and pass through the minicolumn and then it can be determined by using 4-(2-pyridylazo)-resorcinol (PAR) as chromogenic reagent. So, parameters such as thiocyanate concentration and pH effects on the separation efficiency, sorption capacity of the polyurethane foam minicolumn, influence of the flow rates, PAR concentration, pH effect on the chromogenic reaction, minicolumn regeneration, analytical features and others were investigated. The results demonstrated that nickel (at concentration of 0.5 mg/ml) can be quantitatively separated from iron and copper (200 mg/ml), zinc and cobalt (100 mg/ml) by using a minicolumn containing 0.125 g of polyurethane foam. Nickel can be determined with great selectivity and sensitivity and the procedure was applied for nickel determination in brass, bronze, steel and rock certified reference materials. The results showed satisfactory accuracy and precision. The limit of detection was 77 ng/ml and the RSD was 2.63%. A dynamic range from 0.25 up to 5.00 µg/ml and a sample throughput of 24 samples per hour were achieved.
Nickel Alloy Alloy Alloy Alloy Geological Spectrophotometry

"Simultaneous Determination Of Organotin Compounds By Hydride Generation-gas Phase Molecular Absorption Spectrometry"
Talanta 2001 Volume 54, Issue 5 Pages 953-962
J. Sanz-Asensio, M. T. Mart&iacute;nez-Soria, M. Plaza-Medina and M. P&eacute;rez Clavijo

Abstract: This study describes the determination of ternary mixtures of dimethyltin chloride (DMT), trimethyltin chloride (TMT) and monobutyltin chloride (BT) by hydride generation-gas phase molecular absorption spectrometry and the application of different chemometric methods: principal components regression (PCR) and partial least squares (PLS). The two methods are applied to the absorption spectra of mixtures of DMT, TMT and BT. Two different experimental designs are tested for the mixtures, a triangular design and a central composite design. The models obtained from the triangular design offer the best prediction results. The effects of the number of working wavelengths and the number of factors included in the calibration model is studied and a different behavior is seen for each compound and calibration model. The methods are applied to the analysis of artificial aqueous samples containing different concentrations of DMT, TMT and BT species. No significant differences are observed between the calibration models investigated. (C) 2001 Elsevier Science B.V. All rights reserved.

"Solid Phase Microextraction Gas Chromatography-glow Discharge-optical Emission Detection For Tin And Lead Speciation"
J. Anal. At. Spectrom. 2001 Volume 16, Issue 4 Pages 376-381
N&eacute;stor Guillermo Orellana-Velado, Rosario Pereiro and Alfredo Sanz-Medel

Abstract: A modified interface between a gas chromatograph (GC) and a hollow cathode (HC) radiofrequency (rf) glow discharge (GD) with detection by optical emission spectrometry (OES) has been investigated for elemental speciation studies. Solid phase microextraction (SPME), used for extraction and pre-concentration of organic compounds, is here used for the introduction of the metal species under investigation into the injector of the GC, after pre-concentration of metal species ethylated in situ with sodium tetraethylborate. Tin [monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT)] and lead species [trimethyllead (TML) and triethyllead (TEL)] were used as models and separated using a capillary column. Detection by rf-(HC)GD-OES was accomplished at 283.9 nm for tin and 283.3 nm for lead. After optimization of the parameters affecting the rf-(HC)GD signals (pressure, radiofrequency power and He flow rate used as plasma gas) and also the parameters affecting the SPME technique (adsorption time, desorption time, injector temperature and position of the fiber into the injector of the GC), the analytical characteristics were calculated. Good detection limits for the tin and lead species under study (0.021 µg L-1 for MBT, 0.026 µg L-1 for DBT, 0.075 µg L-1 for TBT, 0.03 µg L-1 for TEL and 0.15 µg L-1 for TML) were achieved. Finally, the accuracy of the proposed speciation methodology was tested by analyzing a certified reference material (sediment PACS-2) from the National Research Council of Canada.

"Arsenic And Antimony Determination By On-line Flow Hydride Generation-glow Discharge-optical Emission Detection"
Spectrochim. Acta B 2001 Volume 56, Issue 1 Pages 113-122
N&eacute;stor Guillermo Orellana-Velado, Matilde Fern&aacute;ndez, Rosario Pereiro and Alfredo Sanz-Medel

Abstract: Hollow cathode (HC) and conventional Aat cathode (FC) glow discharge (GD) optical emission spectrometry (OES) were used as detectors for the determination of arsenic and antimony by on-line hydride generation (HG) in a flow system. Both radiofrequency (rf) and direct current (dc) sources were investigated to produce the discharge. The design of the HC and FC and also the parameters governing the discharge (pressure, He flow rate, voltage, current and delivered power) and the HG (sodium borohydride concentration and reagent flow rates) were investigated using both cathodes. The analytical performance characteristics of HG-GD-OES with HC and FC were evaluated for some emission lines of arsenic (193.7, 200.3, 228.8 and 234.9 nm). The best detection limit (0.2 µg l-1)was obtained when the emission line of 228.8 nm was used with FC. Under the same arsenic optimized experimental conditions, the system was evaluated to determine antimony at 259.7, 252.7 and 231.1 nm, 252.7 nm being the emission line which produced the best detection limit (0.7 µg l-1). The rf-HC-GD-OES system was applied successfully to the determination of arsenic in freeze-dried urine in the standard reference material 2670 from NIST. Finally, a Row injection system was assayed to determine arsenic at 228.8 nm, using a dc-GD with both FC and HC. The results indicated that for low volumes of sample, the HC discharge allows better analytical signals than the FC, (C) 2001 Elsevier Science B.V. All rights reserved.

"Precision Attainable In The Determination Of Silver By Flame Atomic Absorption Spectrometry - Analysis Of Thermoelectric Silver-doped Tellurides"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 183-190
Jitka &Scaron;r&aacute;mkov&aacute;, Stanislav Kotrl&yacute; and Pavla Jakoubkov&aacute;

Abstract: Effects of the presence of mineral acids and varied matrix composition were investigated to assess the reliability of flame atomic absorption spectrometric determination of Ag in milligram samples of bismuth antimony telluride monocrystals with thermoelectric properties. For optimum conditions, i.e. hydrogen ion concentration of about 1 mol l(-l) in a mixture of HNO3, HCl and tartaric acid, a linear calibration between 0.1 and 3 µg mL-1 of Ag was obtained. In order to achieve a high precision of absorbance readings, it was necessary to minimize the time delay (about 2 h for 1 mol L-1 of H+) between the preparation of solutions and the measurements. Under such conditions, a long-run reproducibility of the slope values and reliable determinations of 100-900 µg g-1 of Ag in 10^-25 mg samples were achieved with relative standard deviation of 1-3%. The 3s detection limit was estimated to be about 0.050 µg mL-1. A modified version of the standard additions technique with three steps was applied to confirm the results close to the limit of determination.
Silver Inorganic compound Spectrophotometry

"Characterization Of Two Polyphosphazene Materials As Membranes In Membrane Induction Mass Spectrometry"
Anal. Chim. Acta 2000 Volume 407, Issue 1-2 Pages 311-317
Mark L. Stone, Garold L. Gresham and Linda A. Polson

Abstract: Membrane introduction mass spectrometry (MIMS) has made large strides in capability improvement since its introduction. The main progress has been in systematic design changes that has allowed this technique to measure analytes in the parts-per-trillion range, samples that have had no special handling or pre-treatment. In spite of these improvements, however, the most important component of MIMS--the membrane--has not been optimized. In this paper, the results of testing two polyphosphazene polymers is reported and compared with those of silicone rubber. The results show that the rich chemical diversity possible with the phosphazene materials and their tailorability, make them good candidates for MIMS applications.
Toluene 2-Propanol Trichloroethylene Tetrahydrofuran Methyl ethyl ketone Mass spectrometry

"Dual Electrode Signal-subtracted Biosensor For Simultaneous Flow Injection Determination Of Sucrose And Glucose"
Anal. Chim. Acta 1999 Volume 380, Issue 1 Pages 7-15
Werasak Surareungchai, Supinda Worasing, Pornpimol Sritongkum, Morakot Tanticharoen and Krissanapong Kirtikara

Abstract: A multi-enzyme electrode obtained by a two-step immobilization of the enzymes glucose oxidase, mutarotase and invertase was developed for the determination of sucrose. Glucose oxidase was entrapped in a poly-1,3-diaminobenzene film on a platinum electrode by electrochemical polymerization and a combination of mutarotase and invertase was cross-linked over the electrode via bovine serum albumin and glutaraldehyde. The sucrose concentration was determined from hydrogen peroxide oxidation at +0.7 V vs. Ag/AgCl. This immobilization method minimized interference from ascorbic acid. A second electrode, for glucose only, was constructed containing inactive invertase. This gave an almost identical glucose response to the sucrose sensor and hence could be used for signal subtraction. In this manner, sucrose could be determined in the presence of glucose at higher concentrations. The influence of enzyme content, pH, temperature, and optimum operational conditions for use in a flow injection analysis (FIA) system were determined. When used in FIA, the sensor responded to sucrose in the range 1-300 mmol l-1. The sensor was stable for 15 h of continuous use (150 assays) and retained 70% activity after 30 days. When used to analyze the sucrose and glucose contents in a number of different soft drinks, the sensor showed good agreement with the standard liquid chromatography (LC) method.
Sucrose Glucose Soft drink Amperometry

"Selective Stopped-flow Injection Spectrophotometric Determination Of Palladium(II) In Hydrogenation And Automobile Exhaust Gas Converter Catalysts"
Anal. Chim. Acta 2000 Volume 412, Issue 1-2 Pages 161-167
Aristidis N. Anthemidis, Demetrius G. Themelis and John A. Stratis

Abstract: A stopped-flow injection spectrophotometric method is reported for the determination of palladium(II), using 2,2-dipyridy-2-pyridylhydrazone (DPPH) as a color forming reagent. The absorbance of the Pd(II)-DPPH complex was monitored at 540 nm, at pH approximate to 0.3. The various chemical and physical parameters were optimized and a study of interfering ions was also carried out. The calibration graph has two linear parts, first in the range 0-25 mg L-1 (s(r)=0.44%, r=0.9999) with a detection limit of c(L)=0.084 mg L-1 and the second in the range 25-60 mg L-1 (s(r)=1.6%, r=0.9996). In both cases the sampling rate was 30 injections per hour. The method is very selective because the strongly acidic medium used prevented the formation of complexes of the reagent with other ions. The method was successfully applied to the determination of palladium in hydrogenation and automobile exhaust gas converters catalysts. The relative standard deviation of the mean values and the recovery ranged between 0.6 and 1.6% and 97.0-102.6%, respectively.
Palladium(II) Industrial Spectrophotometry

"Inorganic Arsenic Speciation Using BAL In Natural Waters"
Quim. Anal. 2002 Volume 20, Issue 4 Pages 181-186
Brana, L.F.;Sanchez, F.;Palacios, M.A.;Bonilla, M.M.;Torralba, R.

Abstract: A new method was developed for the selective determination of As(V) and As(III) in water samples by HG-AAS. The method is based oil the retention of inorganic arsenic in alumina microcolumn and selective elution of As(III) with BAL (British Anti Lewisite or 2,3-dimercapto-1-propanol), and of As(V) with 6 M HCl. The detection limit after retention is 6 µg L-1 for As(III) and 4 µg L-1 for As(V). After pre-concentration the L.D. can be drastically reduced by a factor of 100. The RSD was always lower than 5%. The analysis of mineral water and sea water revealed than only As(V) was present.

"Determination Of Bismuth, Selenium And Tellurium In Nickel-based Alloys And Pure Copper By Flow Injection Hydride Generation Atomic Absorption Spectrometry-with Ascorbic Acid Prereduction And Cupferron Chelation-extraction"
Anal. Chim. Acta 2002 Volume 459, Issue 1 Pages 161-168
Hui-Ming Liu, Shi-Yang Chen, Pin-Hsuan Chang and Suh-Jen Jane Tsai

Abstract: Diverse matrix effects on the determination of bismuth, selenium and tellurium (mug g-1) in nickel-based alloys and pure copper by flow injection hydride generation atomic absorption spectrometry (FIAS-HGAAS) were investigated. Sodium tetrahydroborate was used as the reductant. The separation of analytes from copper matrix was mandatory while the analytes were successfully determined without being separated from the alloy matrix. Hydrochloric acid was effective in the prereduction of bismuth and selenium, however, it did not give any satisfactory result for tellurium in nickel-based alloys. In this work, 5% (w/v) ascorbic acid was proved effective for the prereduction of tellurium. Successful determination of tellurium in copper was achieved when N-nitroso-N-phenylhydroxylamine (cupferron) chelation-extraction was employed for the separation of tellurium from copper matrix. Cupferron chelation-extraction was performed in phosphate buffer (a mixture of 0.2 mol L-1 sodium phosphate and 0.1 mol L-1 citric acid). Lanthanum hydroxide coprecipitation at pH 10.0±0.5 was effective for bismuth and selenium, Standard reference materials of nickel-based alloys and pure copper were analyzed using the proposed methods. The linear range for the calibration curves were 0.30-15 and 0.20-10 ng mL-1 for BiH3 and H2Se, respectively, with a correlation coefficient of 0.9995. For H2Te, the linear range for the calibration curves was 0.50-12 ng mL-1 with the correlation coefficient of 0.9994. Good agreement was obtained between experimental values and certified values. Satisfactory recovery ranged from 91±1 to 106±2% was obtained from five replicate determinations.

"The Use Of ETV-ICP-MS For The Determination Of Selenium In Serum"
J. Anal. At. Spectrom. 1999 Volume 14, Issue 2 Pages 121-126
Justine Turner, Steve J. Hill, E. Hywel Evans and Ben Fairman

Abstract: The development of a novel procedure for the accurate determination of selenium in serum using electrothermal vaporisation inductively coupled plasma mass spectrometry (ETV-ICP-MS) is described. The proposed method eliminates the need for a lengthy sample digestion procedure (a requirement with many methods for the analysis of biological samples), utilising a simple 1 + 19 dilution of the serum with 1% nitric acid. Many of the interferences normally associated with the determination of selenium by ICP-MS are successfully eliminated with careful optimization of the ETV temperature program and modifier system. Analytical characteristics for Se-74, Se-77, Se-78 and Se-82 are reported, including detection limits (3s blank) of approximately 0.1 ng g-1 for Se-77 and Se-82. Short-and long-term reproducibility data between 4.7 and 4.9% and 3.2 and 3.8% (RSD) for Se-77 and Se-82, respectively, are shown. The accuracy of the method, which included Te as an internal standard, was demonstrated with the analysis of three internal quality control samples and the certified reference material NIST SRM 1598 (bovine serum). Results within 10% of the target value were achieved for three of the four isotopes studied, with slightly worse results for Se-78 owing to the large interference from argon adduct ions on this isotope. Preliminary work involving the addition of nitrogen to the argon aerosol carrier gas was successful in reducing the ArAr interference at m/z 78.

"Determination Of Chlorophenols In Human Urine Based On The Integration Of On-line Automated Clean-up And Preconcentration Unit With Micellar Electrokinetic Chromatography"
Electrophoresis 1999 Volume 20, Issue 14 Pages 2922-2929
Claudia Mardones, Angel R&iacute;os, Miguel Valc&aacute;rcel

Abstract: A new method was developed and validated for the determination of chlorophenols in human urine by using micellar electrokinetic chromatography (MEKC) coupled via a mechanic arm to an on-line automatic clean-up and pre-concentration unit for urine samples. Separation is accomplished by using a selective buffer consisting of 15 mM berate, 25 mM phosphate and 100 mM sodium dodecyl sulfate (SDS) at pH 9.1 in addition to a positive power supply of 25 kV at 18°C. The proposed capillary electrophoresis (CE) method allows the separation of 11 chlorophenols within 7 min with a reproducibility as relative standard deviation (RSD) between 2.6% and 7.2%, and limits of detection (LODs) between 0.08 and 0.46 µg/mL for all chlorophenols. Urine samples were previously hydrolyzed with 37% HCl at 80°C for 60 min and then cleaned on a C-18 mini-column. Recoveries ranged from 58% to 103%. The pre-concentration treatment affords limits of determination between 4 and 12 ng/mL for all chlorophenols except pentachlorophenol and 4-chlorophenol, which could not be determined. The overall analysis time, including on-line clean-up, pre-concentration and electrophoretic separation is 20 min per sample.

"Flow Injection Analysis Of Mercury(II) In Pharmaceuticals Based On Enzyme Inhibition And Biosensor Detection"
J. Pharm. Biomed. Anal. 1999 Volume 20, Issue 1-2 Pages 263-269
P. Bertocchi, E. Ciranni, D. Compagnone, V. Magearu, G. Palleschi, S. Pirvutoiu and L. Valvo

Abstract: An enzymatic amperometric procedure for measurement of mercury(II) in pharmaceuticals, based on the inhibition of invertase and on a glucose electrode was studied. Analytical parameters for measurements in batch and flow injection analysis (FIA) have been optimized. Mercury(II) was detected in the 10^-60 ppb range with RSD less than or equal to 2%. A sample throughput of 6 h-1 for batch and 15 h-1 for FIA was obtained. The total mercury(II) from thimerosal (thiomersal, sodium ethylmercurithiosalicylate) in eye-drop samples was measured with the amperometric procedure after oxidative cleavage treatment. Results for both batch and FIA procedures correlated well with atomic absorbtion spectroscopy (AAS) data.
Mercury(II) Pharmaceutical Sensor

"Spectrophotometric Determination Of Thiocyanate By Sequential Injection Analysis"
Anal. Chim. Acta 2000 Volume 403, Issue 1-2 Pages 279-286
J. F. van Staden and A. Botha

Abstract: A sequential injection analysis (SIA) system was developed for the spectrophotometric determination of thiocyanate as Fe(SCN)(2+). The physical parameters (flow rate, sample and reagent volumes, holding coil and reaction coil internal diameter and length) which influence dispersion in a SIA system were optimized. The effect of the reagent concentration and nitric acid concentration tin the reagent solution and carrier stream, respectively), were also studied. Reagent consumption was effectively reduced by introducing the reagent as a zone into the nitric acid carrier stream, compared to flow injection analysis where the reagent itself is the carrier stream. The system is fully computerized and able to monitor thiocyanate in samples at 24 samples per hour with a relative standard deviation of <1.20% for samples and standards with thiocyanate concentrations above 10.0 mg L-1. The calibration graph is linear from 2.0 to 150.0 mg L-1 with a 3s detection limit of 1.1 mg L-1. The system has been applied to the determination of thiocyanate in process solutions and waste waters.
Thiocyanate ion Waste Industrial Spectrophotometry

"Simultaneous Determination Of Copper, Lead, Cadmium And Zinc Using Differential Pulse Anodic Stripping Voltammetry In A Flow System"
Anal. Chim. Acta 2000 Volume 411, Issue 1-2 Pages 201-207
J. F. van Staden and M. C. Matoetoe

Abstract: The use of differential pulse anodic stripping voltammetry (DPASV) in a how system for the simultaneous determination of Cu, Cd, Fe, Pb and Zn was evaluated for applicability with a glassy carbon electrode. Simultaneous quantitative analysis for these elements is possible at low concentrations of Fe when using pyrophosphate as a supporting electrolyte (pH 4.0). An application of the proposed method is reported for the determination of these elements in water samples. The working ranges are 50-500 µg L-1 for Cu, Cd and Pb and 100-400 µg L-1 for Zn. The Fe content was negligible in these samples. Recovery studies and metallic interferences are reported. Detection limits of 39, 9.6, 16.6 and 14.7 µg L-1 for Cu, Cd, Pb and Zn, respectively, were obtained.
Copper Lead Cadmium Zinc Industrial Voltammetry Electrode

"Influence Of Single Bead String Reactors On Zone Penetration And The Isodispersion Point In Sequential Injection Analysis"
Instrum. Sci. Technol. 1999 Volume 27, Issue 3 Pages 167-180
J. F. Van Staden; T. McCormack

Abstract: A non-reactive dye was used to investigate the effect, that a single bead string reactor (SBSR) has upon the isodispersion point and the degree of zone penetration of the sample and reagent zones in a simple sequential injection system. The length of SBSR, the pump speed (flow rate) and the volume ratios of both the sample and reagent zones in a total constant volume were parameters that were studied with the SBSR at one of two positions, either before the detector or between the selection valve, and the holding coil.

"Experimental Design Modeling Of Carryover To Optimize Air-segmented Continuous Flow Analysis"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 21-31
Guihua Liu, Bernard J. Van Wie, Dan Leatzow, Bruce Weyrauch and Tom Tiffany

Abstract: Multiple blood chemistry assays were performed in an air-segmented continuous flow analysis system with plasma/reagent pairs separated from each other by air bubbles and water segments. Carryover of one reaction pair to subsequent ones was investigated in this study where red dye simulates the original. reaction pair and water segments simulate the target reaction pair. Several factors were tested for their effects on the carryover coefficient by using two three-factorial experimental designs. The carryover coefficient in each design was regressed as a function of three parameters by fitting to a second-order model. The significance probabilities for individual parameters revealed that the size of air bubbles and of the initial slug do not have significant effects, so these were excluded from the two designs and two-parameter models re-fit to the data. The statistical analysis for each case confirms that the two-parameter model for the second design gives the best fit with an F-value of 147.44 and R-2 of 0.955. The average absolute difference between the model and data is 2.3%. An objective function, that balances carryover with total processing time, shows optimal loading when six bubbles and five 5.3 µl (2s) water segments are inserted. Under this condition, carryover is essentially zero and total loading time is 22s. This scheme will allow processing of three chemistries in 3 min. Larger numbers of chemistries can be processed in the same time by re-configuring the system to allow smaller sub-second samples.
Blood

"A UV Spectroscopic Method For Monitoring Aromatic Hydrocarbons Dissolved In Water"
Anal. Chim. Acta 2000 Volume 422, Issue 2 Pages 187-198
F. Vogt, M. Tacke, M. Jakusch and B. Mizaikoff

Abstract: An enhanced UV spectrometric method is applied to trace measurements of aromatic hydrocarbons dissolved in water. This approach gains selectivity and sensitivity by the use of optically generated first and second derivatives of transmission spectra. The augmented spectroscopic technique is combined with chemometric algorithms like principal component regression or partial least squares which are used for calibration of the spectrometer and quantitative evaluation of spectra. Laboratory measurements were performed on mixtures containing up to five substances, i.e. benzene, toluene, ethylbenzene, the three xylene isomers, chlorobenzene, and gasoline. Due to the difficulty of preparing precisely defined calibration and test samples of these very volatile compounds, a novel mixing device was developed and is presented. From these first investigations it can be estimated that the detection limits are down to ~10 µg analyte per liter of water by using a 10 cm absorption pathlength and a few minutes measurement time.
Hydrocarbons, aromatic Benzene Chlorobenzene Ethylbenzene Toluene 4-Xylene 2-Xylene 3-Xylene Waste Spectrophotometry Spectroscopy

"Factors Affecting The Analytical Applications Of Zeolite Modified Electrodes: Indirect Detection Of Nonelectroactive Cations"
Anal. Chim. Acta 1999 Volume 388, Issue 1-2 Pages 79-91
A. Walcarius

Abstract: Carbon paste electrodes modified with several types of copper-doped zeolites were evaluated as sensors for nonelectroactive cations in a flow injection system. After having described the amperometric detection mechanism and proposed an efficient procedure to achieve good reproducibility in successive measurements, it was shown how various experimental parameters influenced the quantitative determination of potassium ions (chosen as reference cationic species), such as the applied potential, mobile phase composition and flow rate, the ionic strength of the sample solution, or the injection volume. The analysis was then extended to other mono-and divalent cations and selectivity series were established in relation to wherever zeolites A, X, Y, or clinoptilolite was used. It was concluded that the sensors response was mainly governed by the diffusion of both the electron transfer co-factor (Cu2+ species) and the cationic analytes, rather than by the thermodynamic predictions related to ion exchange equilibrium despite the fact that the amperometric detection was allowed to occur only after the exchange of Cu2+ species for the cationic analyte. Detection limits around 10^-6 M were obtained for the analysis of alkali metal, ammonium, calcium and magnesium ions using the copper-doped zeolite Y modified electrode in a 0.01 M tetrabutylammonium bromide mobile phase.
Potassium Metals, alkali Ammonium Calcium Magnesium Electrode Amperometry

"Determination Of Arsenic And Vanadium In Airborne Related Reference Materials By Inductively Coupled Plasma-mass Spectrometry"
Anal. Chim. Acta 1999 Volume 392, Issue 2-3 Pages 299-306
Chu-Fang Wang, C. Y. Chang, C. J. Chin and L. C. Men

Abstract: This study investigated sample digestion techniques and instrumental interference in determining As and V in airborne related reference materials using inductively coupled plasma mass spectrometry (ICP-MS). Four reference materials, NIST SRM 1648 urban particulate matter, BCR Reference Material No. 176 city waste incineration ash, NIST SRM 2709 San Joaquin soil, and NIST SRM 1633b coal fly ash were dissolved by acid mixture high-pressure bomb digestion. A HNO3+H2O2+HF mixed acid digestion with a low temperature evaporation procedure is proposed as an effective sample pretreatment method for the determination of As in all samples. The addition of HF is required especially for dissolving geologically originated samples such as soil or dust. It was found that, with the proposed digestion procedure, the determinations of V are still unacceptable for highly chlorinated samples when using quadrupole ICP-MS. It was also proved that sector-field ICP-MS is sufficiently sensitive for the determination of V, and can be utilized as a valid tool to investigate the amount and direction of biased results obtained from ICP-MS.
Arsenic Vanadium NIST 1648 BCR 176 NIST 1633 NIST 2709 Mass spectrometry

"Hot-wire Amperometric Monitoring Of Flowing Streams"
Talanta 2000 Volume 50, Issue 6 Pages 1205-1210
Joseph Wang, Markus Jasinski, Gerd-Uwe Flechsig, Peter Grundler and Baomin Tian

Abstract: This paper describes the design of a hot-wire electrochemical flow detector, and the advantages accrued from the effects of locally increased temperature, mainly thermally induced convection, upon the amperometric monitoring of flowing streams. A new hydrodynamic modulation voltammetric approach is presented, in which the solution flow rate remains constant while the temperature of the working electrode is modulated. Factors influencing the response, including the flow rate, temperature pulse, or applied potential, have been investigated. The hot-wire operation results also in a significant enhancement of the flow injection amperometric response. The minimal flow rate dependence observed with the heated electrode should benefit the on-line monitoring of streams with fluctuated natural convection, as well as various in-situ remote sensing applications.
Ferricyanide Amperometry Electrode Electrode Electrode

"Highly Sensitive Flow Injection Immunoassay System For Rapid Detection Of Bacteria"
Anal. Chim. Acta 1999 Volume 399, Issue 1-2 Pages 99-108
Ihab Abdel-Hamid, Dmitri Ivnitski, Plamen Atanasov and Ebtisam Wilkins

Abstract: A flow injection amperometric immunofiltration assay system for the rapid detection of total Escherichia coli and Salmonella was developed. The system is based on the use of disposable porous nylon membranes which act as a support for the immobilization of anti-E. coli or anti-Salmonella antibodies. The assay system consists of a flow injection system, a disposable filter-membrane and an amperometric sensor. Parameters affecting the performance of the immunofiltration assay system such as membrane pore size, non-specific binding, conjugate concentration and sample volume were studied and optimized. A sandwich scheme of immunoassay was employed and the immunofiltration system was able to specifically and directly detect 50 cells/ml of total E. coli or 50 cells/ml of Salmonella with an overall analysis time of 35 min. This immunosensor can be easily adapted for the assay of other microorganisms and may be a basis for a new class of highly sensitive and automated bioanalytical devices for the rapid quantitative detection of bacteria.
Bacteria, salmonella Bacteria, echerichia coli Amperometry Sensor

"Preparation And Characterization Of Immobilized Acid Phosphatase Used For An Enzyme Reactor: Evaluation In Flow Injection Analysis And Pre-column Liquid Chromatography"
Anal. Chim. Acta 2000 Volume 406, Issue 2 Pages 191-199
Susumu Yamato, Nozomi Kawakami, Kenji Shimada, Masaki Ono, Naoko Idei and Yuji Itoh

Abstract: Acid phosphatase from various sources (plant and animals) was immobilized by attachment with glutaraldehyde to aminoalkylsilyl glass. An amino function of the enzyme was covalently coupled to the aldehyde derivative in the presence of phosphate as an enzyme inhibitor. The highest retention of enzyme activity was obtained by the immobilization of acid phosphatase from sweet potato. The double bond of Schiff base was reduced with sodium tetrahydroborate. The immobilized sweet potato acid phosphatase was active toward three substrates, p-nitrophenyl phosphate, β-glycerophosphate and riboflavin phosphate. The immobilized acid phosphatase retained almost complete activity over 4 months in a refrigerator. The immobilized acid phosphatase was packed into a stainless-steel column (10 x 4 mm i.d.) and used on-line as an immobilized enzyme reactor (IMER). The stability, reusability and utility of the IMER were verified by a flow injection system and a liquid chromatographic pre-column reaction system. The IMER was extremely stable and reusable at room temperature. and was fully active even in 50% methanol solution.
4-Nitrophenol 4-Nitrophenylphosphate HPLC

"Alkaline Fusion-alkaline Mode HG-ICP Spectrometry For Selenium Determination"
J. Anal. At. Spectrom. 2002 Volume 17, Issue 5 Pages 534-536
Fang Xu, Zheming Ni, Deren Qiu, Junfu You, Wang Hu and Pengyuan Yang

Abstract: A fully alkaline procedure, including alkaline fusion, pre-reduction of Se(VI) to Se(IV) in alkaline medium and an alkaline mode of H2Se generation, together with ICP-AES for the determination of total Se in biological and environmental samples, is described. Alkaline fusion coupled with alkaline mode hydride generation could effectively avoid volatile losses of selenium by changing it into soluble salts such as selenate or selenite and greatly eliminate the chemical interference from the co-existing transition metals Fe, Cu, and Mn. The method was verified with a certified reference material and was successfully applied to several real samples such as selenium-enriched plasma, egg, animal feeds and soils with satisfactory results.

"Determination Of Ultra-trace Amounts Of Cobalt In Seawater By Graphite Furnace Atomic Absorption Spectrometry After Pre-concentration With Ni/8-quinolinol/1-nitroso-2-naphthol Complex"
Anal. Chim. Acta 2000 Volume 407, Issue 1-2 Pages 147-153
Qiangbin Zhang, Hirotsugu Minami, Sadanobu Inoue and Ikuo Atsuya

Abstract: A sensitive and accurate method for the determination of ultra-trace amounts of cobalt in seawater is described. Ultra-trace amounts of cobalt were pre-concentrated by co-precipitation with a combination of 8-quinolinol and nickel as a carrier element and 1-nitroso-2-naphtol as an auxiliary complexing agent. The co-precipitates obtained were directly measured by graphite furnace atomic absorption spectrometry using the solid-sampling technique. The co-precipitation conditions for ultra-trace amounts of cobalt with Ni/8-quinolinol/1-nitroso-2-naphtol complex were investigated in detail. It was found that ultra-trace amounts of cobalt are co-precipitated quantitatively with Ni/8-quinolinol/1-nitroso-2-naphtol complex in the pH range of 5.5-8.5. The concentration factor by the co-precipitation reached about 33,000-fold for 1000 mL of the aqueous sample. The proposed method has been successfully applied to the determination of ultra-trace amounts of cobalt in seawater, and the detection limit for cobalt which was defined as the concentration calculated from three times of the standard deviation of the procedural blanks, is 1 ng/l for 1000 mi portions of seawater samples.
Cobalt Sea Spectrophotometry

"Preliminary Studies Of Iron Speciation (Fe2+ And Fe3+) In Peat Samples Using Polarography"
Anal. Sci. 2000 Volume 16, Issue 7 Pages 751-756
Paavo Per&auml;m&auml;ki, Mia Kumpum&auml;ki, Ilkka V&auml;lim&auml;ki, Ritva Heikknen

Abstract: Current-sampled (tast) polarography was used in the determination of the two iron oxidation states Fe2+ and Fe3+ in peat samples. The iron couple was reversible in the 0.1 mol L-1 citrate-supporting electrolyte used. The total iron concentration in the samples was determined by differential pulse polarography. Sample decomposition was done in a nitrogen atmosphere by hydrofluoric acid and sulfuric acid. The accuracy of the determinations was verified by spiking experiments and analyzing in-house standards (Geological Survey of Finland) RS 31 (Rapakivi granite), RS 71 (Diabase) and certified reference material PCC-1 (Peridotite, U.S. Geological Survey). The method, developed for this purpose, proved to be reasonably accurate.
Iron(2+) Iron(III) USGS PCC-1 Polarography

"Packed Column Supercritical Fluid Chromatography/mass Spectrometry For High-throughput Analysis. Part 2"
Anal. Chem. 1999 Volume 71, Issue 19 Pages 4223-4231
Manuel C. Ventura, William P. Farrell, Christine M. Aurigemma, and Michael J. Greig

Abstract: A supercritical fluid chromatograph was previously interfaced to a mass spectrometer (SFC/MS) and the system evaluated for applications requiring high sample throughput using negative-mode atmospheric-pressure chemical ionization (APCI) (Ventura et al. Anal. Chem. 1999, 71, 2410-2416). This report extends the previous work demonstrating the effectiveness of SFC/MS, using positive ion APCI for the analysis of compounds with a wide range of polarities. Substituting SFC/MS for LC/MS results in substantial time saving, increased chromatography efficiency, and more precise quantitation of sample mixtures Flow injection analysis (FIA) also benefits from our SFC/MS system. A broader range of solvents is compatible with the SFC mobile phase compared with LC/MS, and solutes elute more rapidly from the SFC/MS system, reducing sample carryover and cycle time. Our instrumental setup also allows for facile conversion between LC/MS and SFC/MS modes of operation.

"Reverse Polarity Capillary Zone Electrophoretic Analysis Of Nitrate And Nitrite In Natural Water Samples"
Anal. Chem. 1999 Volume 71, Issue 14 Pages 2725-2731
Asopuru A. Okemgbo, Herbert H. Hill, William F. Siems, and Steven G. Metcalf

Abstract: This paper describes the application of reverse polarity capillary zone electrophoresis (CZE) for rapid and accurate determination of nitrate and nitrite in natural water samples. Using hexamethonium bromide (HMB) as an electroosmotic flow modifier in a borate buffer at pH 9.2, the resoln. of nitrate and nitrite was accomplished in less than 3 min. CZE was compared with ion chromatography (IC) and cadmium reduction flow injection analysis (Cd-FIA) methods which are the two most commonly used standard methods for the anal. of natural water samples for nitrate and nitrite. When compared with the IC method for the determination of nitrate and nitrite, CZE reduced anal. time, decreased detection limits by a factor of 10, cut lab. wastes by more than 2 orders of magnitude, and eliminated interferences commonly associated with IC. When compared with the cadmium reduction method, CZE had the advantage of simultaneous determination of nitrate and nitrite, of being able to be used in the presence of various metallic ions that normally interfere in cadmium redn., and of decreased detection limits by a factor of 10.

"Analysis Of Aluminum Content In Aluminum Alloy Using Electrography And Flow Injection Analysis"
Am. Lab. 1999 Volume 31, Issue 21 Pages 26-28
Zhang X., Jiang, X., Liu, M., and Kuang, K.

Abstract: Electrography, first developed by Glazuaov and Fritz,1 is an analytical method used to identify and determine solid substances. It has been used for more than 60 years and was frequently used in the 1950s. However, with the development of modern analysis techniques such as laser technology, electron fault detection, and atomic absorption spectrophotometry, electrography is now rarely used because it depends on the color that develops directly on the filter paper after the ions have been transferred onto it. This method is used mainly for qualitative analysis rather than exact quantitative analysis. Particularly in multicomponent specimens, the large number of interferents always have an effect on the exact quantity of the trace components. Therefore, use of electrography has been severely limited up to now.
Aluminum Alloy Electrochemical analysis

"Optimization Of A Sodium Ion-selective Electrode For Use In Serum Measurements"
Anal. Chim. Acta 1977 Volume 89, Issue 1 Pages 101-109
Ulla Fiedler

Abstract: A Na+-selective polymeric membrane electrode was optimized, especially with reference to serum measurements. For a given combination of polymer and ligand, the choice of membrane solvent is critical. Potentiometric measurements and electrodialysis experiments showed that the dielectric constant and solubility parameter of the solvent influence the electrode selectivities, stability, slope, and limit of detection. For use in serum measurements, it is essential to use an appropriate analytical technique, such as flow injection analysis, which permits exposures to serum for only short periods of time.
Sodium Blood Serum Electrode Potentiometry

"Flow Injection Analysis. 8. Determination Of Glucose In Blood Serum With Glucose Dehydrogenase"
Anal. Chim. Acta 1977 Volume 89, Issue 2 Pages 241-254
E. H. Hansen, J. Rika and B. Rietz

Abstract: The flow injection principle is used for enzymatic determination of glucose in blood serum with glucose dehydrogenase. Methods based on single-point determination on deproteinized serum samples, single-point determination comprising continuous-flow dialysis, and 2-point kinetic assay, are described and discussed. Special consideration was given to optimizing the flow parameters in order to minimize reagent consumption, yet to maintain a high sampling rate. Thus, for the single-point determination, a sampling rate of 120 samples/h was achieved at an expenditure of 3.12 g-units of glucose dehydrogenase/sample.
Glucose Blood Serum Clinical analysis Spectrophotometry Sample preparation

"Flow Injection Analysis. 2. Ultra Fast Determination Of Phosphorus In Plant Material By Continuous-flow Spectrophotometry"
Anal. Chim. Acta 1975 Volume 79, Issue 1 Pages 79-91
J. Rika and J. W. B. Stewart

Abstract: The effect of sample volume, tube length, tube diameter, peak height and sampling rate on the determination of P in acidic plant digests was investigated, and optimal conditions for the flow injection method were described. Sampling rates of 420 samples/hr were achieved without incurring problems from carryover of samples, and evidence was obtained that rates ≤700 samples/hr were possible. The flow injection method was proved to be suitable for routine analyzes.
Phosphorus Plant Kidney Sample preparation Spectrophotometry

"Flow Injection Analysis. 3. Comparison Of Continuous-flow Spectrophotometry And Potentiometry For Rapid Determination Of The Total Nitrogen Content In Plant Digests"
Anal. Chim. Acta 1976 Volume 81, Issue 2 Pages 371-386
J. W. B. Stewart, J. Rika, H. Bergamin Filho and E. A. Zagatto

Abstract: The Berthelot reaction for the determination of NH3 by formation of indophenol blue was adapted to continuous-flow spectrometry, and the effects of acidity, temperature, EtOH content, and sampling rate were investigated; optimal conditions are described for the determination of N in Kjeldahl digests. Comparison of results obtained by this method, the air-gap electrode, and classical distillation shows no statistical difference at the 1% level, but the flow injection technique can be run at a much higher sampling rate (110-180 samples per hr) than any other method and uses ≥0.3 mL of digest/anal.
Nitrogen Nitrogen, total Plant Electrode Potentiometry Sample preparation Spectrophotometry

"Flow Injection Analysis. 5. Simultaneous Determination Of Nitrogen And Phosphorus In Acid Digests Of Plant Material With A Single Spectrophotometer"
Anal. Chim. Acta 1976 Volume 82, Issue 1 Pages 137-144
J. W. B. Stewart and J. Rika

Abstract: The rapid simultaneous determination of N and P in a single acid digest of plant material based on the Berthelot and phosphomolybdate colorimetric methods, respectively, was adapted to flow injection analysis with a dual-channel manifold. A routine sampling rate of 200 determinations/hr can be achieved with a single spectrometer; evidence is presented that 400 determinations/hr are possible with two spectrophotometers. The effect of sample volume on absorbance, and the methods of obtaining different proportions of sample split are discussed.
Nitrogen Nitrogen, total Phosphate Plant Sample preparation Spectrophotometry

"Solvent Extraction In Continuous-flow Analysis. Determination Of Molybdenum In Plant Material"
Anal. Chim. Acta 1978 Volume 101, Issue 1 Pages 9-16
H. Bergamin F&deg;, J. X. Medeiros, B. F. Reis and E. A. G. Zagatto

Abstract: A method is proposed for solvent extraction in continuous-flow injection analysis. Optimal tube lengths, pumping extraction efficiency, sample volumes, etc. are discussed. The thiocyanate method for the determination of molybdenum in plant material is used to demonstrate the feasibility of the method. A phase-separation chamber and a proportional injector are described. The proposed method can be used to determine molybdenum in plant ash solutions down to 0.05 ppm with good reproducibility and accuracy, at a rate of ~30 samples/h.
Molybdenum Molybdate Plant Environmental Spectrophotometry Sample preparation Sample preparation

"Merging Zones In Flow Injection Analysis. 2. Determination Of Calcium, Magnesium And Potassium In Plant Material By Continuous-flow Injection Atomic Absorption And Flame Emission Spectrometry"
Anal. Chim. Acta 1979 Volume 104, Issue 2 Pages 279-284
E. A. G. Zagatto, F. J. Krug, H. Bergamin F, S. S. J&oslash;rgensen and B. F. Reis

Abstract: A flow injection analysis system is described for the automatic determination of Ca, Mg, and K in plant material by atomic absorption and flame emission spectrometry. Flow rates and damping factors were studied; the sample undergoes a dispersion of ~40-fold with automatic incorporation of La when necessary. The proposed method allows 300 determinations/h with a typical relative standard deviation of 0.5% and a reagent consumption of only 500 µg La/determination, which is ~1% the usual amt. The results for plant digests agree with those obtained by the standard atomic absorption spectrometric procedure.
Calcium Magnesium Potassium Plant Spectrophotometry Spectrophotometry Sample preparation

"Differential Kinetic Analysis And Flow Injection Analysis. 1. The Trans-1,2-diaminocyclohexane-tetraacetate Complexes Of Magnesium And Strontium"
Anal. Chim. Acta 1979 Volume 105, Issue 1 Pages 327-333
J. H. Dahl, D. Espersen and A. Jensen

Abstract: The flow injection principle was used in simultaneous differential kinetic analysis for Mg and Sr ions in solution. The method is based on the acid dissociation of the trans-1,2-diaminocyclohexanetetraacetate complexes of Mg and Sr and on the use of Cu(II) as a scavenger. A 200 µL sample was used for a 2-point kinetic assay; special consideration was given to optimizing the flow parameters. At sampling rates of 60 samples/h, high reproducibility of measurement and relatively low reagent consumption can be achieved. The limiting factor of the method is that a rather pronounced difference must exist between the rates of reaction of the metal complexes.
Magnesium Strontium Spectrophotometry

"Flow Injection Analysis With A Fluorimetric Detector For Determinations Of Glycine And Albumin"
Anal. Chim. Acta 1979 Volume 106, Issue 2 Pages 395-399
Joy I. Braithwaite and J. N. Miller

Abstract: Flow injection analysis with fluorometric detection was used in the determination of glycine and albumin, with o-phthalaldehyde being used in determination of the latter. Preliminary variables and applications of flow injection analysis were examined, using quinine sulfate and m-hydroxybenzoic acid which are intrinsically fluorescent. System response was linear in the range of 0-8 µg/mL for glycine and concentrations as low as 2 pg/mL were detectable. The level of glycine in orange juice and dietetic cola was 0.33-0.41 and 0.17 g/dL, respectively. Serum albumin determinations flow injection analysis had a relative standard deviation of 1.8%. The method allowed sampling rates of 180/h for both glycine and albumin.
Glycine Albumin Food Blood Serum Juice Soft drink Coca cola Clinical analysis Fluorescence

"Stopped-flow And Merging Zones - A New Approach To Enzymatic Assays By Flow Injection Analysis. Determination Of Glucose In Serum"
Anal. Chim. Acta 1979 Volume 106, Issue 2 Pages 207-224
J. Rika and E. H. Hansen

Abstract: Four alternative flow injection methods based on the concept of merging zones were developed for the assay of glucose in serum with glucose dehydrogenase. Special attention was paid to the dispersion and synchronization of the merging zones and to methods of measuring the blank value of serum. The optimal procedure, based on rate measurements, allowed the assay of glucose at a rate of 100 determinations/h, with the anal. readout available 30 s after sample injection. The assay requires <1 unit of enzyme/sample.
Glucose Blood Serum Clinical analysis Spectrophotometry

"Isothermal Distillation In Flow Injection Analysis. Determination Of Total Nitrogen In Plant Material"
Anal. Chim. Acta 1979 Volume 109, Issue 1 Pages 45-54
E. A. G. Zagatto, B. F. Reis, H. Bergamin F and F. J. Krug

Abstract: An isothermal distilaltion unit is incorporated in flow injection systems. The influence of surfactant, flow rates, alkalinity, ionic strength, collector stream pH, reagent concentration, and sample volume in NH3 distillation are discussed. A method for the determination of total N in plant digests employing Nessler reagent is proposed. This method, based on merging zones approach, is characterized by a sampling rate of 100 samples/h, a precision >3%, a reagent consumption of only 100 µL/sample, and virtually no base-line drift. The results agree with those obtained with the indophenol blue colorimetric method. The incorporation of isothermal distillation in flow systems with potentiometric measurement is also described.
Nitrogen, total Plant Potentiometry Spectrophotometry

"Determination Of Iron(II) And Iron(III) By Flow Injection And Amperometric Detection With A Glassy Carbon Electrodes"
Anal. Chim. Acta 1980 Volume 114, Issue 1 Pages 267-274
J. W. Dieker and W. E. Van Der Linden

Abstract: Flow injection analysis can be used for the determination of both Fe(II) and Fe(III) with an amperometric detector. The flow-through cell contains a glassy C electrode. Selection of the appropriate voltammetric technique choice of the indication potentials, sample size, composition of the carrier stream, etc., are discussed. The limit of determination is ~10-6M; the calibration curves are linear in the concentration. ranges 10^-3-10-5 M for Fe(III) and 5 x 10^-4-10-5 M for Fe(II). To illustrate the potentialities of the proposed method, standard rocks have been analyzed.
Iron(2+) Iron(III) Geological Environmental Amperometry Electrode

"A Possible Approach To The Optimization Of Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 59-70
J. M. Reijn and H. Poppe, W. E. Van Der Linden

Abstract: The theory of sample zone dispersion is well known for most cases of practical interest in flow injection analysis. This paper offers a theoretical analysis which allows for the optimal design of single-line flow systems. For various reactor types, a detailed analysis is provided in terms of physical constants, design parameters and constraints.

It is shown that, within practical constraints and using a pressure drop of less than 1 bar, it is possible to operate flow systems at 100 samples per hour, with a residence time of 100 s and a reagent consumption of 8 µL for each determination. Further miniaturization of flow systems must rely on smaller detector volumes than those currently available, a situation not unlike that in liquid chromatography.

"Optimization Of Peroxidase Immobilization And Of The Design Of Packed-bed Enzyme Reactors For Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 87-99
Bo Olsson and Lars &Ouml;gren

Abstract: Packed-bed reactors containing horse radish peroxidase were optimized for use in flow injection systems. The most active and stable immobilizations were produced by azo linkage to porous glass. The influence of pore and particle diameter as well as pH of immobilization, number of coupling sites, and enzyme purity were studied. The reactor behavior could be accurately described by a theory derived on the assumptions of first-order kinetics. The effects of internal and external mass transfer resistances were studied and the rate constants were evaluated. Design criteria for analytical reactors are discussed. A small particle diameter is shown to be of utmost importance in order to achieve low dispersion with fixed levels of back-pressure and conversion.
Glucose Hydrogen peroxide Oxygen Biochemical analysis

"The Spectrophotometric Determination Of Hydroxylamine Alone And In The Presence Of Hydrazine By Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 153, Issue 1 Pages 277-280
G. C. M. Bourke, G. Stedman and A. P. Wade

Abstract: The method is based on the manual procedure of Dias et al. (Anal. Abstr., 1979, 37, 2B143). The sample solution was mixed with a three fold volume of 10 mM ferrozine [3-(2-pyridyl)-5,6-bis-(4-sulfophenyl)-1,2,4-triazine (monosodium salt)], a 0.41 mL portion was injected into a carrier stream (1.19 mL min-1) of 0.3 M chloroacetic acid - 0.273 M NaOH - 3.1 mM Fe(III), and the absorbance was measured with use of the flow-through photo-transducer of Sly et al. (J. Autom. Chem., 1982, 4, 186), which incorporated a light-emitting diode (giving max. emission at 565 nm) and a phototransistor. Calibration graphs were rectilinear for 10 µM to 0.1 mM hydroxylamine in the sample solution, the limit of detection was 1 µM, and the repeatability of peak heights was 0.7%. A 20-fold excess of hydrazine can be tolerated; when larger amounts are known to be present, hydrazine can be determined separately and a correction applied.
Hydroxylamine Water Spectrophotometry

"Experimental Optimization Procedures In The Determination Of Phosphate By Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 155, Issue 1 Pages 89-102
T. A. H. M. Janse, P. F. A. van der Wiel and G. Kateman

Abstract: Factorial design experiments are used initially to optimize discretely adjustable parameters, viz, injection volume, tube diameter (and hence max. pumping rates), coil lengths and reagent concentration. Then the continuously adjustable parameters, such as pumping rates, are refined by use of the super-modified Simplex procedure. As an example, the determination of PO43- by the molybdenum blue method is optimized and assessed in terms of peak height, peak width, baseline noise and rectilinearity of calibration graphs.
Phosphate Water Spectrophotometry

"Spectrophotometric Determination Of Sulfate In Sodium Hydroxide Solutions By Flow Injection Analysis"
Anal. Chim. Acta 1984 Volume 156, Issue 1 Pages 313-317
E. A. Jones

Abstract: The method is based on the catalytic effect of SO42- on the reaction between Zr and methylthymol blue(I). Under optimum conditions, the test solution (100 µL) is injected into a stream of 80 µM-I in 0.6 M HCl (1.2 mL min-1), which is then mixed with 800 µM-ZrOCl2 in 50 mM HCl (1.2 mL min-1). The mixture is passed through a 4-m reaction coil and the absorbance of the resulting complex is monitored at 586 nm (e = 20,000). The calibration graph is rectilinear for 0.05 to 0.5 g L-1 of SO42-, with a coefficient of variation of ~2%. Results for 10 batches of 1 M sodium hydroxide agreed well with those obtained by ion chromatography and by gravimetry. Twenty samples can be analyzed per h.
Sulfate Industrial Inorganic compound Spectrophotometry

"Determination Of Iodine Value Of Fatty Acids By A Flow Injection Method"
Anal. Chim. Acta 1984 Volume 158, Issue 2 Pages 157-167
Cheng-chih Lee and Bruce D. Pollard

Abstract: A modification of the standard Wij solution method was used in an automated system controlled by an AIM-65 microcomputer. Iodine values of various industrial fatty acids were determined. Optimum operating conditions were established for the system, and a comparison was made between detection by u.v. absorbance and potentiometry. The coefficient of variation between observed and expected values were 9% for u.v. absorbance detection and 0.9% with potentiometric detection. Results obtained were similar to those of the conventional method. The max. continuous-run sample through-put was 12 h-1.
Iodine value Industrial Organic compound Potentiometry Spectrophotometry

"Flow Rate Dependence Of Post-column Reaction Chromatographic Detectors And Optimization Of Reactor Length For Slow Chemical Reactions"
Anal. Chim. Acta 1985 Volume 167, Issue 1 Pages 137-144
Y. T. Shih and Peter W. Carr

Abstract: In high-performance liquid chromatography, use of any post-column reactor invariably involves a compromise between the conditions needed to obtain complete reaction and avoidance of excessive dispersion by band broadening in the reactor. Flow rate and the reactor geometry interact to establish the final chromatographic performance. Based on the flow-rate dependence of the peak area and peak height, post-column detectors constitute a distinct class of detectors which differ from mass-flow and concentrations-sensitive detectors such as the flame ionization and absorbance detector, respectively. The concept of reactor length optimization is developed for first-order chemical reactions in a post-column detector. The findings are applicable to both chromatographic and flow-injection systems.
HPLC

"Sequential And Differential Catalytic-fluorimetric Determination Of Manganese And Iron By Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 169, Issue 1 Pages 141-148
F. Lazaro, M. D. Luque De Castro and M. Valcarcel

Abstract: Two methods for the determination of Mn and Fe in mixtures by flow injection analysis are described, which are based on the catalytic action of Mn or Fe on the oxidation of salicylaldehyde thiosemicarbazone by H2O2. For method(I) a diverting valve is used to select the most appropriate carrier for the determination of one cation in the presence of the other. For method(II) a system with splitting and confluence points is used to obtain two different residence times for the two portions into which the sample is sub-divided. Simplex optimization was used to determine optimum conditions. The calibration graphs were rectilinear for 48 to 200 and 40 to 600 ng mL-1 for methods(I) and(II), respectively.
Manganese Iron Water Fluorescence

"Determination Of Some Phosphorus-containing Compounds By Flow Injection With A Molecular Emission Cavity Detector"
Anal. Chim. Acta 1985 Volume 170, Issue 2 Pages 331-336
J. L. Burguera, M. Burguera and Daniel Flores

Abstract: Optimum conditions (e.g., flow rate, sample volume, dimensions of the tubing and flame composition) have been established for the determination of P-containing inorganic and organic compounds by the cited technique. The ranges of rectilinear response, detection limits and coefficient of variation (typical values being 10 to 200 ng, 2.5 and 3%, respectively) are tabulated for H3PO4, H3PO3, H3PO2, trimethyl phosphite, triethyl phosphite and tributylphosphine; sensitivity improved with decreasing O content of the compounds. The sample throughput was 20 h-1. As peaks were well separated, components of ternary mixtures could be determined.
Phosphorus Phosphoric acid Phosphorus acid Hypophosphorus acid Trimethylphosphite Triethylphosphite Tributylphosphine Spectrophotometry Spectrophotometry

"A Kalman Filter For Calibration, Evaluation Of Unknown Samples And Quality Control In Drifting Systems. 4. Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 174, Issue 1 Pages 27-40
P. C. Thijssen, L. T. M. Prop and G. Kateman, H. C. Smit

Abstract: The application of state estimation in flow injection analysis is described. This method allows the online correction of drift on the calibration graph. The entire calibration system, which is tabulated and summarized, furnishes a set of algorithms for prediction, filtering, evaluation, control, optimization and smoothing. The selection and verification of the calibration model and noise co-variances used were investigated. To demonstrate the applicability of the calculations, an automated flow injection system was used to determine Cl- in aqueous samples, based on the metathesis of SCN- in Hg(SCN)2 by Cl- in the presence of Fe(III) , with measurement of the complex at 470 nm.
Chloride Water Spectrophotometry

"Solid-state Chemiluminescence Detector For Hydrogen Peroxide Based On An Immobilized Luminophore. Application To Rain-water"
Anal. Chim. Acta 1985 Volume 174, Issue 1 Pages 151-161
P. van Zoonen, D. A. Kamminga, C. Gooijer, N. H. Velthorst and R. W. Frei, G. G&uuml;bitz

Abstract: The construction and use of a H2O2 detector, based on peroxyoxalate chemiluminescence, is described. The detector consists of a two-bed reactor packed with solid bis-(2,4,6-trichlorophenyl) oxalate(I) and 3-aminofluoranthene as luminophore, immobilized on controlled-pore glass beads. Optimum conditions for pH, solvent and purity of I for flow-independent operation, and four detector configurations are discussed. Samples can be injected into a moving stream or directly into the monitor to provide a manually operated field monitor. The peak height is directly proportional to the concentration. of H2O2 and the log. - log. calibration graph is rectilinear with a slope of 1 from the detection limit (15 nM, signal-to-noise ratio of 3) up to 10 mM. The coefficient of variation (n = 10) for manual injections of samples was 3% at the 0.5 µM level, with a limit of detection of 40 nM. Sample throughputs are 100 h-1 in the flow injection mode and 40 h-1 for manual injection. Results are presented for determination of H2O2 in rain-water.
Hydrogen peroxide Rain Chemiluminescence

"Anodic Stripping Voltammetry With Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 175, Issue 1 Pages 45-53
Carolyn Wechter, Neal Sleszynski, John J. O'Dea and Jane Osteryoung

Abstract: A Plexiglas flow cell of wall-jet design has been used to determine ~0.1 µM-Pb at a mercury film plated on a vitreous-carbon disc electrode. Sample injection into the carrier stream (1.0 M acetic acid - Na acetate buffer of pH 4.7) was followed by a reductive pre-concentration period (at -0.9 V vs. the SCE) for analyte deposition. The pump was then turned off while the potential was scanned to 0.0 V vs. the SCE by differential pulse or square-wave voltammetry. Rectilinear calibration plots were obtained for almost 4 decades of change in concentration, up to 0.1 mM; coefficient of variation ranged from 0.5% (50 µM-Pb(II)) up to 10% (0.5 µM-Pb(II)) (n = 7). Maximum peak heights were obtained for narrow nozzle diameter and short nozzle-to-electrode distances. An increase in sample throughput rates by increasing the solution flow rate decreased the analytical signal. Square-wave voltammetry provided shorter analysis times and better sensitivity than differential pulse voltammetry.
Lead Electrode Voltammetry Voltammetry

"Measurements Of Kinetic Parameters Of Inorganic Pyrophosphatase By Flow Injection Procedures"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 209-216
Hisanobu Hirano, Yoshinobu Baba, Norimasa Yoza and Shigeru Ohashi

Abstract: A flow system with two alternative parallel lines is used. The product of the enzymatic hydrolysis of pyrophosphate, viz, phosphate, is determined by using a reagent comprising 5.3 g of (NH4)6Mo7O24.4H2O(I) in 1 l of 0.3 M H2SO4. The reaction is monitored at 380 nm. An anion-exchange column (5 cm x 4 mm) of TSK-gel SAX (10 µm) is used for determination of both the substrate and the product. The mobile phase contains 0.21 M KCl, 1 mM Na2EDTA and 10 mM NH3 with a MoV - Mo(VI) reagent, prepared by dissolving I in 1.8 M H2SO4 in the presence of zinc dust. The effect of Mg concentration. and temperature on the enzyme activity and the Michaelis constant and max. velocity at 25°C were determined. For evaluation of kinetic parameters, the system was designed to enable instant termination of the enzymatic hydrolysis and detection of phosphate in presence of pyrophosphate without the production of a negative peak.
Phosphate Enzyme, pyrophosphatase Spectrophotometry

"Fluoride Ion-selective Electrode In Flow Injection Analysis. 1. General Methodology"
Anal. Chim. Acta 1986 Volume 185, Issue 1 Pages 127-136
Wolfgang Frenzel and Peter Br&auml;tter

Abstract: Variations of cell geometry, injection volume, electrode polishing procedure, carrier composition and flow rate on the response time of an Orion 96-09 combination F- electrode were studied in order to find the optimum operating conditions for determining F-. A wall-jet flow cell was optimal for flow injection potentiometric analyzes of 10- to 250 µL samples with different concentration. ranges under slightly varied experimental conditions at 60 to 180 h-1. Calibration graphs based on the electrode potential under steady-state conditions were rectilinear for 1 mg L-1 to 1 g L-1 of F-, and curvilinear in the range 1 µg L-1 to 1 mg l-1, but with good reproducibility, e.g., the coefficient of variation was 1% for >100 µg L-1 of F and 2 to 5% for lower concentration. (n = 3).
Fluoride Electrode Potentiometry

"Online Electrolytic Dissolution Of Alloys In Flow Injection Analysis. 1. Principles And Application In The Determination Of Soluble Aluminum In Steels"
Anal. Chim. Acta 1986 Volume 190, Issue 1 Pages 177-184
H. Bergamin F&deg;, F. J. Krug and E. A. G. Zagatto, E. C. Arruda and C. A. Coutinho

Abstract: Polished steel samples were dissolved by electrolysis in a special cell (details given) and the solution was passed directly to a flow injection manifold as described by Krug et al. (Ibid., 1986, 179, 103). Dissolved Al was determined spectrophotometrically at 535 nm afte reduction with Eriochrome cyanine R (C. I. Mordant Blue 3) solution containing HCl, ascorbic acid and hexamine for pH adjustment. Beer's law was not obeyed and a second-derivative equation was used. The effects of electrolysis time, c.d. and electrolyte composition and flow rate were studied.
Aluminum, soluble Industrial Alloy Spectrophotometry

"Development Of A Selective Post-column Detector For Phenols Separated By High Performance Liquid Chromatography"
Anal. Chim. Acta 1987 Volume 192, Issue 2 Pages 277-287
S. K. Ratanathanawongs and S. R. Crouch

Abstract: Samples are injected into the HPLC system for separation followed by UV detection at 254 nm. The column eluate is passed to an air-segmented continuous-flow system and mixed with diazotized sulfanilic acid, and the azo-derivatives are detected at 450 nm. The aqueous reaction system was compatible with reversed-phase mobile phases. Band-broadening (caused by the post-column reactor) was observed, following optimization, to be between 5 and 20%. A rectilinear response from 0.071 to 14 µg mL-1 of phenol was obtained. The system was demonstrated by the analysis of river water containing phenol, aniline, o-cresol and 3,5-xylenol and of residual fuel oil fractions containing phenol and o-cresol.
Phenol Aniline 2-Cresol Xylenol Oil River HPLC Spectrophotometry

"Pulsed Colorimetric Detection Of Carbohydrates At A Constant Detection Potential At Gold Electrodes In Alkaline Media"
Anal. Chim. Acta 1987 Volume 192, Issue 2 Pages 205-213
Glen G. Neuburger and Dennis C. Johnson

Abstract: The transient amperometric response at gold electrodes of a polarograph is integrated and divided by the integration time of up to 1000 ms in order to extend the linear dynamic range compared with pulsed amperometric detection. A flow injection system was used, incorporating a flow-through detector containing a gold rotating-disc indicator electrode, a vitreous-carbon counter-electrode and a reference SCE. Charge - potential plots were obtained by application of a three-step waveform with a computer to undertake amplification, current integration and sampling operations of the analogue signal. Evaluation of the system by determination of glucose and sucrose gave detection limits of 1.0 and 2.5 µM with linear dynamic ranges of 2.2 and 1.7 decades, respectively.
Carbohydrates Glucose Amperometry Coulometry Electrode Electrode

"Computer-assisted Optimization Of An Immobilized-enzyme Flow Injection System For The Determination Of Glucose"
Anal. Chim. Acta 1987 Volume 192, Issue 2 Pages 155-163
C. L. M. Stults, A. P. Wade and S. R. Crouch

Abstract: The Trinder reaction was employed, in which samples (30 µL) were injected into a carrier stream, passed through a single-bead string reactor composed of immobilized glucose oxidase on glass beads (0.6 mm diameter) and mixed, in a second reactor, with the reagent solution of peroxidase solution, 10 mM 4-aminoantipyrine and 10 mM 3,5-dichloro-2-hydroxybenzenesulfonic acid diluted with a universal buffer (pH 10). After reaction in the second plain single-bead string reactor the absorbance was measured at 510 nm. A simplex optimization procedure (Betteridge et al., Talanta, 1985, 32, 709) was applied to the variables of flow rate, temperature and the pH and concentration. of the carrier and reagent. The starting conditions were defined and modified during 50 experiments. The performance of the system was improved by a factor of 22.5 to yield a rectilinear response from 0 to 3.3 mM glucose.
Glucose Spectrophotometry

"Fundamental And Practical Considerations In The Design Of Online Column Preconcentration For Flow Injection Atomic Spectrometric Systems"
Anal. Chim. Acta 1987 Volume 200, Issue 1 Pages 35-49
Zhaolun Fang, Shukun Xu and Suchun Zhang

Abstract: The terms concentration. efficiency (expressed as the enrichment factor per min), retention efficiency, recovery data and elution efficiency are recommended as criteria for the critical evaluation of an online column pre-concentration. system. Efficiency is improved with time-based sampling and double-column systems without intermediate column washing. Columns (4.5 cm x 3 mm) with sample loading rates of 9.5 mL min-1 are proposed for achieving high efficiency and accuracy with AAS detection. More careful optimization of column dimensions is needed for detection by ICP-AES. A procedure for the online pre-concentration. of Co in water, involving columns of CPG-8Q exchanger (Pierce Chemicals) and a mobile phase of 25 mM ammonium acetate (pH 8), is presented. An enrichment factor of 48 was achieved at a sampling rate of 60 h-1. The coefficient of variation was 1.7% at the 40 µg L-1 level (n = 11) and the detection limit was 0.2 µg l-1.
Cobalt Environmental Spectrophotometry

"Online Electrochemical Derivatization Combined With Diode Array Detection In Flow Injection Analysis. Rapid Determination Of Etoposide And Teniposide In Blood Plasma"
Anal. Chim. Acta 1987 Volume 202, Issue 1 Pages 35-47
M. A. J. Van Opstal, J. S. Blauw, J. J. M. Holthuis, W. P. Van Bennekom and A. Bult

Abstract: The cited antineoplastic agents (I and II, respectively) are oxidized electrochemically in a flow-through cell equipped with two porous-graphite working electrodes, followed by spectrophotometric detection of the respective o-quinone compounds at 365 nm. Plasma (1 ml) is extracted with 2 mL of 1,2-dichloroethane and, after centrifuging for 2 min at 2500 g, 1 mL of the organic layer is evaporated to dryness. The residue is dissolved in 100 to 200 µL of carrier solution [Britton - Robinson buffer solution (pH 4) - methanol (1:1)] and a 25 µL portion of this solution is injected into the carrier stream (0.2 mL min-1). The optimum oxidation potentials for I and II were +500 and +450 mV (vs. a proprietary reference electrode), respectively. Calibration graphs were rectilinear in the range 1 to 50 µg mL-1 of I or II, and the limit of detection was 6 ng for each compound. For 2.5 and 25 µg mL-1 of I or II, the coefficient of variation were 6.5 and 3.2%, respectively. Recovery of 10 µg mL-1 of I or II was 95.7 ± 2.7% (n = 6) and the max. injection frequency was 40 h-1. Potential interference from catecholamines and metabolites is discussed.
Etoposide Teniposide Blood Plasma Clinical analysis Spectrophotometry Electrode

"Optimization Criteria For A Single Bead-string Reactor In Flow Injection Analysis Based On Consecutive Kinetic Reactions"
Anal. Chim. Acta 1988 Volume 204, Issue 12 Pages 29-41
J. J. F. van Veen, M. A. J. van Opstal, J. M. Reijn, W. P. van Bennekom and A. Bult

Abstract: In flow-injection methods based on chemical reactions, simple one-step reactions are desirable, but more complex kinetics cannot always be avoided. The consecutive reaction considered here is A + reagent (s)→B→C. The response signal depends on the dispersion of the sample zone in the system and on the kinetics of the chemical reaction. The dispersion in a single-bead-string vector is described by the tanks-in-series model. The reaction of paracetamol with hexacyanoferrate (III) and phenol is used for experimental verification. Rules for optimum reactor design are given, the reactor length being used as the optimization parameter. Comparison of the experimental and calculated peak heights at different reactor lengths confirms the optimization rules.
Spectrophotometry

"Determination Of Sucrose In Sugar-cane Juice And Molasses By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1988 Volume 204, Issue 1-2 Pages 259-270
E. A. G. Zagatto, I. L. Mattos and A. O. Jacintho

Abstract: The diluted and filtered sugar cane juice or molasses is introduced into a flow injection analyzer. with two merging streams, producing two sample zones. One zone is fed directly to the confluence of the streams but the other first flows through a heated coil where partial and reproducible sucrose (I) inversion is achieved at controlled pH and temperature At the confluence point a buffered IO4- reagent is added to oxidize I. The consumption of IO4- is measured spectrophotometrically as a transient lowering of the iodine concentration, produced by reaction of IO4- with I-. The two zones are fed sequentially to a flow cell where two peaks are recorded. The I concentration. is proportional to the difference in peak heights. About 30 samples h-1 of sugar-cane juice can be analyzed. The coefficient of variation was 0.51% for a I concentration. of 13.66% in cane juice (n = 7). Similar precision was obtained with the modified system for molasses (20 samples h-1).
Sucrose Juice Vegetable Spectrophotometry

"Flow Injection Determination Of Creatine In Animal Tissues"
Anal. Chim. Acta 1988 Volume 208, Issue 1-2 Pages 307-312
Zdenk Dvo&aacute;k

Abstract: Animal muscle (~250 g) was homogenized in a Moulinex mill and 10 g of the resulting paste was treated with 200 mL of trichloroacetic acid solution (30 g l-1) in a Waring blender. After filtration, a 1 mL aliquot of the clear extract was diluted to 14 ml, and 4 mL of 2% 1-naphthol in alkaline solution (NaOH - Na2CO3) and 2 mL of biacetyl solution were added. After 20 min, the absorbance at 520 nm was measured. Flow injection analysis in stopped-flow mode, with an optimum stopped-flow time of 22 s, yielded a rectilinear calibration graph for up to 250 mg L-1 of creatine.
Creatine Muscle Sample preparation Spectrophotometry

"Determination Of Ammonium Ion In A Flow Injection System With A Gas Diffusion Membrane. Selection Of Optimal Conditions For The PH Indicator"
Anal. Chim. Acta 1988 Volume 208, Issue 1-2 Pages 81-90
Ryuji Nakata, Takayoshi Kawamura, Hiroyuki Sakashita and Akihiko Nitta

Abstract: Optimum conditions were determined for the spectrophotometric determination of NH4+ by flow injection analysis. A membrane-separation module was constructed from a PTFE membrane filter (80 µm thick; pore size 0.5 µm) tightly held between two PVC sheets acting as spacers, and contained between two clear acrylic plates. The donor solution used was 1 M NaOH. Portions of acceptor stock solution of bromocresol purple(I), bromothymol blue or cresol red, containing NH4Cl buffer if necessary and the pH being adjusted with NaOH, were deaerated to remove CO2 and then injected by using a Rheodyne PTFE rotary valve (type 50) with a loop volume of 132 µL. Maximum sensitivity was achieved by using 15 µM-I at pH 6.8 with a flow rate of 1.0 mL min-1. The effects of donor and acceptor flow rates and of ultrasonic radiation were investigated. A lowering of sensitivity allowed analysis of undiluted urine samples, with a sample rate of 60 h-1 for concentration. >10 µM, and 30 to 40 h-1 for concentration. of 0.3 to 10 µM. The method was more precise than that involving indophenol blue - thymol for the determination of NH4+ in rain and river water.
Ammonium Urine Rain River Spectrophotometry

"Optimization Of Parameters For Gas Diffusion Flow Injection Systems"
Anal. Chim. Acta 1988 Volume 209, Issue 1-2 Pages 157-163
J. S. Canham, G. Gordon and G. E. Pacey

Abstract: Solutions of ClO2 were used in the study. Slow flow rates for both acceptor and donor streams provided efficient transfer of the gas. Use of the counter-current flow mode enhanced signals and the best transport properties were achieved when pressures on both sides of the membrane were equal. Channel depths should be as shallow as possible to achieve optimum results and a spiral-shaped diffusion cell should be used. For reactive systems, stopped-flow, in which the acceptor stream is stopped but the donor stream is continuous, was the best.
Chlorine dioxide

"Determination Of The Pesticides Fenthion And Fenitrothion By Flow Injection With Amperometric Detection"
Anal. Chim. Acta 1988 Volume 209, Issue 1-2 Pages 205-212
J. Hernandez Mendez, R. Carabias Martinez, F. Becerro Dominguez and J. I. Jimenez Jimenez

Abstract: The pesticides were dissolved in carrier solution, viz, 0.06 M acetic acid - 0.04 M Na acetate in aqueous 20% methanol. Fenthion(I) and fenitrothion(II) were determined at +1.3 and -0.9 V vs. Ag - AgCl, respectively, by using a vitreous-carbon working electrode and a gold auxiliary electrode. In the determination of II, interference by O in the carrier solution was prevented with a zinc column. For I, response was rectilinear from 0.16 to 16 µM, with a detection limit of 0.15 µM and a coefficient of variation (n = 10) of 1.7% for 6.64 µM. For II, response was rectilinear from 8 to 80 µM, with a detection limit of 0.52 µM and coefficient of variation (n = 10) of 0.9% for 77.6 µM.
Fenthion Fenitrothion Pesticides Amperometry Electrode

"Flow Injection Method For The Amperometric Determination Of L-lactate With Immobilized Enzymes And A Chemically Modified Electrode"
Anal. Chim. Acta 1988 Volume 213, Issue 1-2 Pages 91-100
L. Gorton and A. Hedlund

Abstract: The flow injection system included a packed-bed enzyme reactor containing L-lactate dehydrogenase and alanine aminotransferase co-immobilized on to glutaraldehyde-activated porous silica, where the L-lactate was oxidized to pyruvate in the presence of glutamate and NAD+, the latter being converted into NADH. The NADH formed was measured with use of a graphite electrode modified with Meldola blue (C. I. Basic Blue 6) and operated at 0 mV vs. Ag - AgCl (0.1 M KCl) in presence of a Pt-wire auxiliary electrode. The calibration graph was rectilinear for 10 µM to 3 mM NADH (10 µM to 1.5 mM lactate). Operating conditions were optimized and the results are discussed; common constituents of biological fluids and food industrial liquids are not expected to interfere electrochemically.
l-Lactate Industrial Electrode Electrode Amperometry

"Integrated Reaction/spectrophotometric Detection In Unsegmented Flow Systems"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 217-227
Fernando L&aacute;zaro, M. D. Luque de Castro and Miguel Valc&aacute;rcel

Abstract: 1-(2-Pyridylazo)-2-naphthol(I) was immobilized on Dowex 50W X4 (400 mesh) and the resin was packed to a height of 5 mm in a flow cell (inner volume ~40 µL) which was placed in the spectrophotometer in the flow injection system. A sample (0.9 ml) containing 0.1 to 26 µg mL-1 of Cu(II) and 0.1 M NaCl at pH 4 to 6 was mixed with the carrier stream (1 ppm of I - 5 mM mercaptoacetic acid - 0.1 M NaCl at pH 6) and the solution was pumped at 1 mL min-1 to a reactor (20 cm x 0.3 mm). The solution then passed to the flow cell and the absorbance was measured at 546 nm. The sample solution could be either injected or pumped into the system over a period of time dependent on the concentration. of Cu. The determination limit was 1 ng mL-1 and rectilinear calibration graphs were obtained over the range 0.1 to 26 µg mL-1 under optimized conditions.
Copper(II) Spectrophotometry

"Automated Spectrophotometric Field Monitor For Water Quality Parameters. Determination Of Ammonia"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 401-407
J. Richard Clinch and Paul J. Worsfold, Frank W. Sweeting

Abstract: A manual flow injection manifold (illustrated) was incorporated into an automated field monitor as described previously (Anal. Abstr., 1988, 50, 6H74). Sample (0.7 mL min-1) and NaOH (0.7 mL min-1) were mixed online in a 50-cm reaction coil before introduction into the water carrier stream (0.7 mL min-1). The carrier stream then passed together with bromothymol blue solution into a gas diffusion cell and the acceptor stream flowed to a solid-state spectrophotometric detector for determination of total NH3 at 635 nm. The calibration graph was rectilinear obtained for up to 5000 µg L-1 of NH3 and the limit of detection was 17 µg l-1. The coefficient of variation (n = 6) were 0.7 to 2.1%. Results are presented for a three-day field trial.
Ammonia Environmental Spectrophotometry

"Flow Injection Determination Of Membrane-selected Organic Compounds"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 299-313
R. G. Melcher

Abstract: A membrane - flow injection system has been developed and optimum conditions established for separation of trace organic compounds in aqueous solution The system comprises a membrane made from Dow Corning Silastic medical-grade silicone rubber tubing, a sample loop and a spectrophotometric detector. A liquid extractant is pumped through the bore of the membrane tube directly to the detector. The membrane is incorporated into a cell (illustrated) connected directly to the extractant stream. The effects were studied of factors, such as membrane size, cell dimensions, extractant composition and carrier flow rate, on peak height and shape. Optimized conditions were evaluated for separation of phenols and neutral organic compounds.
Organic compounds Phenols Spectrophotometry Sample preparation

"Online Electrolytic Dissolution Of Alloys In Flow Injection Analysis. 2. Spectrophotometric Determination Of Molybdenum In Steels"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 397-400
H. Bergamin F&deg;, F. J. Krug, B. F. Reis, J. A. Nobrega, M. Mesquita and I. G. Souza

Abstract: A solid sample was placed on a simple electrolytic chamber and 200 mA DC was applied for 8 s; the dissolved material served as the injected sample zone. The carrier electrolyte solution was 1 M KCl - 0.1 M HCl, the reducing reagent solution was 5% SnCl2.2H2O in 5 M HCl and the reagent solution was aqueous 6% KSCN (flow rates 3.7, 1.0 and 1.0 mL min-1, respectively). The optimum length of the main reaction coil was 150 cm and an 8-cm sampling loop was used. The Mo was determined spectrophotometrically. No measurable baseline drift was observed during continuous operation for 4 h. The calibration graph was rectilinear for up to 600 mg L-1 of Mo; the coefficient of variation (n = 10) for a standard sample containing 2.21% of Mo was 2.3%. (For Part I see Anal. Abstr., 1987, 49, 8B210).
Molybdenum Alloy Spectrophotometry

"Preconcentration And Determination Of Calcium And Magnesium In Brine With Flow Injection Systems"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 439-445
Hiroko Wada, Heisuke Askura, Gogineni Venkata Rattaiah and Genkichi Nakagawa

Abstract: Calcium and Mg in brine were pre-concentrated on a column (5 cm x 2 mm) of Dowex A-1 resin (50 to 100 mesh), and eluted with 0.1 M HCl into a sample tube (20 cm x 0.5 mm) where the eluate was mixed with 1 M NH3 - NH4Cl buffer (pH 10.5) or with 1 M NH3 - NH4Cl buffer (pH 10.5) containing 1.04 mM Ba(II) and 1 mM EGTA (for determination of Mg). Either solution was then mixed with 50 µM-1-(2-hydroxy-4-diethylamino-1-phenylazo)-2-hydroxynaphthalene-3,6-disulfonic acid(I) solution before passing to a 300-cm reaction coil and thence to a flow cell for detection at 520 nm. The calibration graphs were rectilinear for up to 120 µg L-1 of Ca and 30 µg L-1 of Mg and detection limits were 5 and 0.6 µg l-1, respectively. Corresponding coefficient of variation were 1.8% (n = 7) and 1.4% (n = 9). The method was applied to determine Ca and Mg in commercial NaCl and KCl and results agreed with those from an AAS method. A simpler method that does not involve pre-concentration. is proposed for determination of Ca and Mg in brine from a diaphragm cell.
Calcium Magnesium Environmental Spectrophotometry

"Study Of Sample Dispersion In Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 97-105
Takashi Korenaga, Feng-Hua Shen, Hirofumi Yoshida and Teruo Takahashi, Kent K. Stewart

Abstract: Details are presented of an apparatus for the study of the diffusion - convection properties of a laminar capillary flow injection system and of transport phenomena in the sample zone, with use of microscopic photography and photometric detection of injected colored samples. Parameter adjustments for minimization of sample dispersion are assessed and recommended, including the use of coiled tubes and of decreased tube lengths and diameter and slower flow rates.
Spectrophotometry

"Factors Affecting The Detection Limit Of A Flow Injection Spectrophotometric Procedure"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 447-453
Julian F. Tyson and Andrew B. Marsden

Abstract: Factors affecting sensitivity and background noise in the spectrophotometric determination of Cl- are discussed. The manifold used, which was necessary to eliminate negative peaks at low concentration. and refractive index effects, increased the baseline noise because of inefficient mixing. However, noise was reduced by using packed-bed reactors and single-bead-string reactors. Refractive index effects were reduced by using a large sample volume (>500 µL). A matrix-matched carrier stream was used to avoid negative peaks arising when sample and carrier had considerably different I, provided that the level of analyte in the carrier stream was low. Detection limits were lowered to 40 ng L-1 of Cl- in aqueous solution of low I and to 1.3 mg L-1 in 5.25% K2SO4 solution.
Chloride Spectrophotometry

"Different Approaches To The Determination Of Ammonium Ions At Low Levels By Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 121-136
G. Schulze, C. Y. Liu, M. Brodowski and O. Elsholz, W. Frenzel, J. M&ouml;ller

Abstract: For determination of 1 µM-NH3 by flow injection analysis, an optimized gas diffusion system was used, with spectrophotometric or selective-electrode detection. The gas diffusion unit had channels 7.5 cm long, 2 mm wide and 0.2 mm deep. The spectrophotometric detection flow cell had 10 mm pathlength and a capacity of 8 or 18 µL. The selective electrode (0.7 mm diameter, surface area ~20 mm2) consisted of nonactin in PVC and was used with an Orion 90-02 double-junction reference electrode. Spectrophotometric detection with bromocresol purple provided a lower limit of 0.2 µM, but was subject to background interference from, e.g., CO2. The selective electrode provided Nernstian response for 1 to 100 µM, with a detection limit of ~0.1 µM.
Ammonium Potentiometry Spectrophotometry Electrode

"Spectrophotometric Determination Of Trace Uranium In Geological Samples By Flow Injection Analysis With Online Levextrel Resin Separation And Preconcentration"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 279-288
Xing Wu and Weiyi Qi

Abstract: Geological materials (0.1 to 0.2 g) were dissolved in mixed acids, the acid was evaporated and the moist residue was dissolved in 1 mL of 7 M HNO3. The solution was mixed with 100 mg of masking agents [NaF - H3BO3 - EDTA (2:8:5)] and diluted to 10 mL with water and the supernatant solution was aspirated in the flow injection system (illustrated). The U was selectively adsorbed on a micro-column (4 cm x 4.4 mm) of Levextrel CL-5209 resin (120 to 200 mesh) and subsequently eluted with aqueous 0.5% NaF - 0.4% diethylenetriaminepenta-acetic acid. The eluate was then mixed with aqueous dye solution (arsenazo III - chloroacetic acid - H3BO3) and the absorbance of the solution was measured at 649 nm. The calibration graph was rectilinear for up to 0.3 mg L-1 of U and the detection limit was 3 µg l-1. The coefficient of variation (n = 11) for 0.03 and 0.18 mg L-1 of U were 4.72 and 0.57%, respectively. Results for eight geological standards agreed with certified values.
Uranium Geological Spectrophotometry

"Flow Injection Techniques For The Removal Of Stable-compound Interferences In Flame Atomic Absorption Spectrometry Of Calcium"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 339-347
C. E. Adeeyinwo and J. F. Tyson

Abstract: Interference from PO43- in the determination of Ca was reduced by optimization of the position of the capillary tip in relation to the oxidant inlet in the nebulizer and of the instrument operating parameters. However, interference from Al had to be removed by incorporating a separation procedure and devising a merging stream manifold. The sample was injected into the water carrier stream, which then merged with the reagent stream (NH3 - ammonium oxalate). The pptd. Ca oxalate was retained in a column containing glass beads (0.5 mm diameter) and a nylon filter, and then eluted with HCl for AAS determination. Up to 200 mg L-1 of Al was tolerated with a coefficient of variation of 2% for Ca at the 10 mg L-1 level.
Calcium Water Spectrophotometry

"Enzymatic Methods For The Determination Of Ethanol Based On Linear And Cyclic Flow Injection Systems"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 161-172
A. M. Almuaibed and Alan Townshend

Abstract: Mini-columns (2.5 cm x 2.5 mm) containing(I) alcohol dehydrogenase bonded to controlled-pore glass and(II) aldehyde dehydrogenase bonded to CNBr-activated Sepharose 4B were used in a linear or a closed-loop flow injection system for ethanol oxidation with formation and fluorimetric detection of NADH at 460 nm (excitation at 360 nm) or spectrophotometric detection at 340 nm. In the linear system the carrier stream contained 1.8 mM NAD+, 0.15 M KCl, 1 mM 2-mercaptoethanol and 0.05 M Na4P2O7 adjusted to pH 9.0 with 0.1 M NaOH. The cyclic system also contained a column (5 cm x 2.5 mm) of glutamate dehydrogenase for regeneration of NAD+, and the carrier stream (adjusted to pH 8.5 instead of 9.0) contained additionally 0.02 M NH4Cl and 0.01 M 2-oxoglutarate. The linear system provided the more sensitive conditions, with a rectilinear calibration range of 0.17 to 4 mM ethanol.
Ethanol Fluorescence Spectrophotometry

"Catalytic Determination Of Molybdenum In Plants By Flow Injection Spectrophotometry With Ion-exchange Separation"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 239-245
L. C. R. Pessenda, A. O. Jacintho and E. A. G. Zagatto

Abstract: Oven-dried plant samples (1 g) were ashed for 3 to 4 h at 550°C, and the ash was moistened with 1 to 2 mL of water, mixed with 5 mL of 4 M HCl, dried on a water bath at 60°C and mixed with 10 mL of 0.1 M HCl. The solution was filtered, the procedure was repeated until 50 mL of filtrate was obtained, and the sample was set aside overnight. Sample solution was continuously aspirated through a 20-cm loop and a column (9 cm x 3 mm) of Dowex 50W-X8 resin (100 to 200 mesh; H+ form) where interferents were retained. The Mo was eluted with 2 M NH4Cl or 4 M HCl and the eluate was mixed with the carrier stream (0.15 M NH4Cl) before merging sequentially with 0.02% H2O2 in 0.15 M HCl and 4% KI solution The absorbance of the solution was measured at 350 nm. The effects of flow rate and concentration. of eluent are discussed. The calibration graph was rectilinear up to 40 µg L-1 of Mo and the coefficient of variation was 2%. Results generally agreed with those from graphite-furnace AAS.
Molybdenum Plant Spectrophotometry

"Seeking High-sensitivity Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 87-95
Takashi Korenaga and Kent K. Stewart

Abstract: The optimization of flow injection analysis systems for use in biochemical determinations of macromolecules was studied, with use of both open-tube and packed systems. A dye was used in initial hydrodynamic studies, followed by use of bromocresol green in protein determinations. Optimum parameters were short, open capillary tubes (10 cm x 0.5 mm) with slow flow (0.05 mL min-1) and small-volume detector flow cells (8 µL).
Proteins

"Indirect Atomic Absorption Spectrometric Determination Of Local Anesthetics In Pharmaceutical Preparations With A Flow Injection Precipitation Technique"
Anal. Chim. Acta 1988 Volume 215, Issue 1-2 Pages 241-248
R. Montero, M. Gallego and M. Valc&aacute;rcel

Abstract: The ppt. formed by injecting Co(II) into a sample stream containing 10 to 110 µM-lignocaine, -amethocaine or -procaine at pH 8.0 to 9.1 was retained on a stainless-steel filter and analyzed by online AAS at 240.7 nm. The amount of pptd. Co was proportional to the concentration. of local anaesthetic in the sample. Chemical variables such as sample pH, Co(II) concentration. and temperature together with flow injection variables were optimized to ensure manifold simplicity (diagram given), minimum sample pre-treatment, and max. response function. The detection limit was 1.2 µg mL-1, the coefficient of variation was 0.6% and the sampling frequency was 100 h-1.
Anaesthetics Lidocaine Amethocaine Procaine Tetracaine Pharmaceutical Spectrophotometry

"Sequential Flow Injection Determination Of Cyanide And Weak Metal Cyanide Complexes With Flow-through Heterogeneous Membrane Electrodes"
Anal. Chim. Acta 1988 Volume 215, Issue 1-2 Pages 283-288
E. Figuerola, A. Florido, M. Aguilar and J. De Pablo, S. Alegret

Abstract: Two I--selective heterogeneous epoxy-based membrane flow-through electrodes were placed before and after a gas diffusion unit in a flow injection system for determination of free and total CN-. The CN--containing sample was injected into a KNO3 carrier solution and free CN- was determined by the first flow-through electrode. The solution was then treated with the HCl stream in the reaction coil. The HCN evolved passed through the gas-permeable membrane in the diffusion unit and was collected in an alkaline solution, where the CN- was measured by the second flow-through electrode. Under optimum conditions, the response was rectilinear from 10 µM to 1 mM CN- and the coefficient of variation were ~2% with a sampling rate of 20 h-1. Total CN- could be determined in the presence of Zn, Cu(II) and Cd but results were low in the presence of Ni, Co(II) and Fe(III). Sulfide and SCN- were not tolerated. The reproducibility was worse than that of spectrophotometric detection but the method could be used over a wider concentration. range and was more suitable for an online control monitoring system.
Cyanide Cyanide, complexes, metal Electrode Electrode Potentiometry

"Flow Injection Extraction-spectrophotometric Determination Of Perchlorate With Brilliant Green"
Anal. Chim. Acta 1989 Volume 217, Issue 1 Pages 177-181
D. Thorburn Burns, N. Chimpalee and M. Harriott

Abstract: Sample solution (250 µL) was injected into buffer solution (citric acid - KH2PO4 - H3BO3 - diethylbarbituric acid - H2O; pH 6) and then mixed with 0.005% brilliant green (C. I. Basic Green 1) in a mixing coil (20 cm x 0.5 mm). The solution was then mixed with benzene in an extraction coil (2 m x 0.5 mm) and the extracts passed through a phase separator before the absorbance of the organic phase was measured at 640 nm. The best results were obtained when the sample pH was adjusted to 5 to 6. The calibration graph was rectilinear for up to 2.5 µg mL-1 of ClO4-, the detection limit was 36 ng mL-1 and the coefficient of variation (n = 10) was 1.2% at 1 µg mL-1 of ClO4-. The effect of diverse ions was studied. Chlorate interfered. The method was successfully applied to determine ClO4- in potassium chlorate, after selective removal of ClO3-.
Perchlorate Inorganic compound Spectrophotometry Sample preparation

"1,2-Bis-(4-methoxyphenyl)ethylenediamine As A Fluorigenic Reagent For Reducing Carbohydrates"
Anal. Chim. Acta 1989 Volume 217, Issue 2 Pages 263-270
Yoshihiko Umegae, Hitoshi Nohta and Yosuke Ohkura

Abstract: Of 28 1,2-diarylethylenediamines examined, meso-1,2-bis-4-(methoxyphenyl)ethylenediamine (I) gave the highest fluorescence intensity with the lowest reagent blank when heated with reducing carbohydrates in an alkaline medium. Under optimum conditions, i.e., 20 mM I in aqueous 50% ethanol, 20 mM NaOH and reaction at 140°C for 30 min, fluorimetric determination at 460 nm (excitation at 330 nm) of 2-deoxy-sugars, amino-sugars and sialic acids was achieved at concentration. as low as 0.2 to 0.9 µM. The fluorescence of the product with D-glucose was stable for 2 h in daylight at room temperature and the calibration graph was rectilinear from 0.5 to 100 µM. The coefficient of variation (n = 10) was 2.5%. Catechol compounds and L-ascorbic acid interfered. I is proposed as a reagent for post-column derivatization in the HPLC determination of reducing carbohydrates in biological samples.
Carbohydrates Fluorescence

"Kinetic Determination Of Lactate Dehydrogenase In Blood Serum By Multi-detection With A Cyclic Flow Injection System"
Anal. Chim. Acta 1989 Volume 219, Issue 2 Pages 191-199
Juan M. Fernandez-Romero, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: Cyclic flow injection allows the repeated passage of the reacting plug through the detector, resulting in multiple peak recordings. The required sensitivity can be selected by using procedures based on fixed-time measurements (peak maxima or minima) or reaction-rate measurements (signal increment between two successive maxima or minima). The method was applied in the determination of lactate dehydrogenase (I) in serum, based on its catalytic effect on the reduction of pyruvate to lactate by NADH. The reaction was monitored at 340 nm. Under optimum conditions, calibration graphs were rectilinear for 0.1 to 2.0 iu L-1 of I. The average recoveries of I were in the range 99.1 to 102.3%. The coefficient of variation (n = 11) were 0.2 to 3.5%.
Enzyme, lactate dehydrogenase Blood Serum Spectrophotometry

"Effects Of Manifold Components On Peak Profiles In Flow Injection Analysis"
Anal. Chim. Acta 1989 Volume 220, Issue 1 Pages 293-297
H. Wada, Y. Sawa, M. Morimoto, T. Ishizuki and G. Nakagawa

Abstract: The effects of the types of pumps and mixing coils, and the manner of merging the streams, on peak profiles were investigated. Four reciprocating pumps, three peristaltic pumps, single and double coils with helix diameter of 0.4 to 3 cm, and two types of mixing joint were examined on the basis of the reactions of Cu(II) and Ni(II) with 5-[(sulfomethyl)amino]-2-(2-thiazolylazo)-p-toluic acid (cf. Ibid., 1986, 179, 181). When pumps yielding small pulsations and double coils with small helix diameter were used, well-defined and reproducible peaks were obtained, and the effects of mixing joints were small.

"Trace Metal Enrichment By Automated Online Column Preconcentration For Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1989 Volume 221, Issue 1 Pages 65-76
Shizuko Hirata, Kazuto Honda, Takahiro Kumamaru

Abstract: Trace metals were pre-concentrated on a micro-column (7 mm x 4 mm) of Muromac A-1 (50 to 100 mesh) at a flow rate of 5 mL min-1. Ions were eluted with 2 M HNO3 (4.85 mL min-1), before analysis by flame AAS. Optimum pH was established for metal ion uptake from sample solution The coefficient of variation for 20 mL samples containing 5 to 100 µg L-1 of Cd, Cr, Cu, Fe, Mn, Pb or Zn were 0.7 to 1.7% (n = 3 or 4). Values for Cd and Cr in standard reference materials of plants, mussel tissue and pond sediment were within the specified range.
Cadmium Chromium Copper Iron Manganese Lead Mussel Pond Spectrophotometry

"Use Of The Hunt Filter To Optimize The Determination Of Impulse Response Functions Of Individual Component Parts Of Flow Injection Manifolds"
Anal. Chim. Acta 1989 Volume 222, Issue 1 Pages 151-157
I. C. Van Nugteren-Osinga, M. Bos and W. E. Van der Linden

Abstract: The dispersion behavior of the various individual parts making up a flow-injection manifold can be expressed by means of impulse-response functions. These functions can be determined by deconvolution of the response curves obtained with and without the part concerned. Special attention is paid to a procedure to decrease the influence of noise. It is shown that good results can be obtained with a Hunt filter which operates in the Fourier domain.

"Optimization Of Flow-through Cells Dialysis And Other Membrane Separations In Flow Injection Analysis Using A Laminar Flow Model"
Anal. Chim. Acta 1989 Volume 224, Issue 1 Pages 13-22
Lars Risinger, Gillis Johansson and Torsten Thorneman

Abstract: he mass transfer in the liquid channels of flow-through dialysers can be described fairly accurately by a laminar flow model. The mass transfer resistance in the liquid channels was of the same magnitude as that of a cellulose acetate membrane for the most effective dialysis cell. Thin channels are therefore of importance both for efficiency and for low dispersion in flow injection. A cell with a pressed membrane support provided the lowest dispersion and pressure dependence. A computer-based model provides a means for the determination of membrane permeabilities.

"Solvent Extraction In Continuous-flow Systems With Intelligent Zone Sampling"
Anal. Chim. Acta 1989 Volume 226, Issue 2 Pages 255-269
Purnendu K. Dasgupta and Wei Lei

Abstract: A portion of extractant (50 to 100 µL) is injected into a flowing reagent stream that passes through an extraction coil of residence time 1 to 3 min, and the extractant is isolated as it flows through the loop of an injection valve, which is activated by sensing by conductivity probes or by appropriate timing. The extractant can then be injected into a second stream for further chemistry before detection of the analyte. The effects of parameters, such as the coil material, configuration and diameter, or the phase ratio and flow rate, were studied. Examples include extraction of C1 to C5 alkanethiols from gasoline, extraction of a dye from aqueous fluoricarbon surfactant solution, and extraction of alkylbenzenesulfonates from water into CHCl3 as its methylene blue ion-pair. In the latter instance, the calibration graph was rectilinear up to 5 µg mL-1 of dodecylbenzenesulfonate; the coefficient of variation for 2.5 µg mL-1 was 1.3%. The detection limit was 50 ng mL-1, and a sampling rate of 60 h-1 should be attainable.
Thiols Oil Spectrophotometry Sample preparation

"Chemiluminescence Detection Of The Benzodiazepine Loprazolam"
Anal. Chim. Acta 1989 Volume 227, Issue 1 Pages 65-71
Anthony R. J. Andrews and Alan Townshend

Abstract: Of seven such compounds tested only loprazolam gave any significant emission after oxidation, e.g., by KMnO4. The optimum conditions used in a 0.5 mm i.d. PTFE tubing dual-flow injection system were: 0.2 mM KMnO4, with 0.94 M formic acid (at pH 0.9) as the carrier stream at 1.3 mL min-1 in both lines. The response was rectilinear between 10 µM and 5 mM for a 50 µL injection, and the limit of detection was 7 µM. Iron(II) and Mn(II) interfered. The method was applied in analysis of tablets, but results were rather higher than expected.
Loprazolam Benzodiazepine, derivatives Pharmaceutical Chemiluminescence

"Flow Injection Determination Of Organic Contaminants In Water Using An Ultraviolet-mediated Titanium Dioxide Film Reactor"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 13-20
Gary K. -C. Low and R. W. Matthews

Abstract: A miniature spiral reactor was constructed by immobilizing a thin film of TiO2 on the inner surface of a length of PTFE tubing, then wrapping the treated tubing around a near-UV illuminating source. The reactor was installed after the injection port of a flow injection system; a diagram is presented of a second injection port, mounted in parallel, with the first, for the introduction of CO2 for calibration. Organic solutes in aqueous solution flowing along the tube were oxidized photocatalytically to CO2 that was then detected by conductivity. The effects of temp., flow rate, reactor length, O concentration. and catalyst loading are discussed. The technique was applied to the determination of alcohols, formaldehyde, oxiran and single-cell alga in sterile water for medical use. The detection limits were 10 nM-methanol and 15 nM-formaldehyde for an injection volume of 20 µL and a flow rate of 3 mL min-1. The coefficient of variation (n = 12) for 8 µM-methanol was 1.5%.
Methanol Formaldehyde Water Conductometry

"Formation Kinetics Of The Pink Azo Dye In The Determination Of Nitrite In Natural Waters"
Anal. Chim. Acta 1990 Volume 232, Issue 2 Pages 345-350
Su-Cheng Pai and Chung-Cheng Yang, John P. Riley

Abstract: The kinetics of the reactions for the formation of the pink azo dye in the determination of nitrate in both fresh water and seawater was studied at different acidities, temperatures, and concentrations of N-1-naphthylethylenediamine (NED). It was found that the reaction is considerably faster in seawater than in fresh water, and that increase in the acidity slightly increases the molar absorptivity. A concentration of NED (4.29 times 10^-6 M) between the extremes described in the literature and 4.2 times 10^-3 M sulfanilamide are recommended for both manual determination and flow injection analysis with respect to rapid reaction and a low reagent blank.
Nitrite Sea River Spectrophotometry

"Flow Injection Technique For The Determination Of Low-levels Of Phosphorus In Natural Waters"
Anal. Chim. Acta 1990 Volume 234, Issue 2 Pages 409-416
Paul R. Freeman, Ian D. McKelvie and Barry T. Hart, Terence J. Cardwell

Abstract: A flow injection instrument for determining low concentration. of P in waters is described and illustrated. The main feature is the use of an inexpensive detector consisting of a flow cell and a photometer that incorporates a super-bright red-light emitting diode as the source and a photodiode as the detector. The procedure is a modification of the tin(II) chloride - molybdate method (cf. Tecator Application Note ASN 60-01183, Tecator AB, 1983) optimized by a modified simplex optimization method. Silicate interference (5 mg mL-1) was removed by addition of aqueous 0.1% tartaric acid. The calibration graph was rectilinear up to 100 µg L-1 of P and the detection limit was 0.6 µg l-1. The coefficient of variation were 2.9% and 0.5% for 2.0 and 50 µgl-1 of P, respectively. An inline pre-concentration anion-exchange column was used to obtain a lower detection limit of 0.1 µg l-1.
Phosphorus Environmental Spectrophotometry

"Mathematical Modeling Of Sequential Determinations By Flow Injection Sandwich Techniques"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 67-74
J. L. Montesinos, J. Bartrol&iacute;, M. Poch and M. del Valle, J. L. F. C. Lima and A. N. Araujo

Abstract: A mathematical model was developed for flow injection analysis, in which the sample is injected between two different reagent solution (sandwich technique). The model considers the system to be a tubular reactor with axially dispersed plug flow. The model was applied with the enzymatic determination of glucose as model system. The effects of varying experimental parameters were simulated, and results were compared with experimental data obtained under the same conditions. The model is useful for the description and optimization of the analytical signals obtained in such techniques.
Glucose

"Flow Injection Determination Of Paraoxon By Inhibition Of Immobilized Acetylcholinesterase"
Anal. Chim. Acta 1990 Volume 236, Issue 2 Pages 267-272
M. E. Leon-Gonzalez and Alan Townshend

Abstract: A system incorporating two injection valves and a spectrophotometric detector (operated at 500 nm) is described and illustrated. The sample solution is injected into a stream of 0.05 M phosphate buffer (pH 8.0) containing 45 mM NaCl and 12 µM-MgCl2. A solution (0.3 mM) of 1-naphthyl acetate, as substrate, is injected via the second valve into the middle of the paraoxon zone. The resulting stream is passed through a glass column, maintained at 29°C, containing acetylcholinesterase immobilized (method described) on controlled-porosity glass (80 to 120 mesh; mean pore diameter 22.6 nm) and is then merged with a solution (5 mM) of p-nitrobenzenediazonium fluoroborate to react with the liberated naphthol before reaching the detector. Continuous-flow and stopped-flow versions of the method are described; in the latter, the sample and substrate are stopped for 35 s in the column. Rectilinear ranges of the continuous- and stopped-flow procedures are 0.2 to 15 µM and 10 to 400 nM, respectively; corresponding detection limits and sample throughput are 0.4 µM and 60 h-1, and 8 nM and 30 h-1. The coefficient of variation (n = 6) for the respective procedures were 1.4% at 8 µM and 0.9% at 0.25 µM. Optimization of the method is described.
Paraoxon Spectrophotometry

"Automated Exploration And Exploitation Of Flow Injection Response Surfaces"
Anal. Chim. Acta 1990 Volume 237, Issue 2 Pages 361-379
A. P. Wade, P. M. Shiundu and P. D. Wentzell

Abstract: Three-dimensional plots of instrumental responses vs. chemical concentration. or flow parameters were obtained with a computer-controlled flow injection system. The chemical systems studied were the photometric determination of PO43-, Pd(II), Fe(II) and S2O82-. Simplex optimization and pattern search methods for collecting response surface data are compared, and the chemical and physical effects on the surface shapes are discussed. This method of automated optimization of chemical reactions in flow analysis is critically assessed.

"Comparison Of The Powell And Simplex Methods In The Optimization Of Flow Injection Systems - Simulation On Modelled Experimental Surfaces And Experimental Optimizations"
Anal. Chim. Acta 1990 Volume 241, Issue 1 Pages 31-42
M. del Valle, M. Poch, J. Alonso and J. Bartroli

Abstract: In the determination of NH3 by the indophenol reaction, both methods provided optimum conditions. However, the Powell algorithm needed fewer evaluations for the determination of maximum sensitivity and throughput and was efficient at the beginning of the process, needing the modification of only one independent variable. With the optimized system, the limit of detection was 5 ng mL-1 and the coefficient of variation (n = 32) for 3 µg mL-1 was 1.5% (throughput 70 per h). The calibration range covered 0.03 to 6 µg mL-1.
Ammonia Spectrophotometry

"Mathematical Modeling Of Single-line Flow Injection Analysis Systems With Single-layer Enzyme Electrode Detection. 2. Simulation Of The Mathematical Model"
Anal. Chim. Acta 1990 Volume 241, Issue 1 Pages 55-69
Spas D. Kolev, G&eacute;za Nagy and Erno Pungor

Abstract: Simulations based on the model (see preceding abstract) were used to study the dependence of the detector sensitivity and the sample throughput on the geometrical parameters and the thickness, enzyme activity, buffer capacity and analyte concentration. at the biocatalytic layer and on the flow rate. From the results electrodes with optimum design could be constructed.
Electrode

"Flow Injection System With Photodiode Array Detection And Multivariate Data Evaluation For Quantifying Teniposide In Blood Plasma"
Anal. Chim. Acta 1990 Volume 241, Issue 1 Pages 23-30
M. J. P. Gerritsen and G. Kateman, M. A. J. van Opstal and W. P. van Bennekom, B. G. M. Vandeginste

Abstract: The micelle-mediated method described by van Opstal (J. Chromatogr., 1989, 495, 139) was applied. For the calibration a partial least squares model was used. Although prediction is possible within 10% of the LC value, the authors admit that the present application requires further optimization with respect to calibration.
Teniposide Blood Plasma Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Arylamines And Sulfonamides By Diazotization And Coupling In A Micellar Medium"
Anal. Chim. Acta 1991 Volume 242, Issue 1 Pages 143-146
J. S. Esteve Romero and G. Ramis Ramos, R. Forteza Coll and V. Cerd&aacute; Martin

Abstract: In the flow injection system, sample solution (0.66 mL min-1) was mixed with aqueous 0.2% NaNO2 (0.17 mL min-1), and the mixture was passed through a 4-m coil and mixed with aqueous 1.5% sulfamic acid (0.17 mL min-1). After passage through a 4-m coil, a portion of the eluate was mixed with 0.01% N-(1-naphthyl)ethylenediammonium dichloride in aqueous 0.5% Na dodecyl sulfate (0.34 mL min-1), the mixture was passed through a 3-m coil, and the absorbance was measured at 550 nm. The flow rates were optimized. For aniline, ethyl 4-aminobenzoate, sulfanilamide, sulfamethizole and sulfathiazole, limits of detection were 0.11 to 0.5 µg mL-1, and coefficient of variation (n = 3) were 3.0% for 5 µg mL-1. Calibration graphs were rectilinear for up to, e.g., 11 µg mL-1. The method was applied to pharmaceutical preparations; results showed good agreement with declared values.
Amines, aromatic Sulfonamides Aniline ethyl-4-aminobenzoate Sulfanilamide Sulfamethizole Sulfathiazole Pharmaceutical Spectrophotometry

"Optimization Of The Two-phase Separation Process In Flow Injection Analysis With An Electron-capture Detection System"
Anal. Chim. Acta 1991 Volume 243, Issue 1 Pages 131-137
M. Novi L. Zupani-Kralj and B. Pihlar

Abstract: A liquid - gas-phase separator based on microporous PTFE membrane tubing was designed and its performance was compared with that of a porous PTFE tape-based separator in a flow injection system equipped with a GC - ECD. Free Cl was used as the measured species and the carrier liquid and gas were water and N, respectively. Optimum conditions for diffusion were determined, and possible interference was investigated. The detection limits of free Cl were 50 and 100 µg L-1 for the tubing and tape-based separators, respectively. A more stable baseline and better reproducibility, as well as better long-term stability of two-phase separation, were obtained with use of the tubing separator.
GC

"Flow Injection Fluorimetric Assay Of Nitrogen-containing Substrates By Online Enzymic Generation Of Ammonia"
Anal. Chim. Acta 1991 Volume 245, Issue 1 Pages 89-99
Mette Tranholm Jeppesen and Elo Harald Hansen

Abstract: In the optimization of the derivatization of NH3 with phthalaldehyde (I) and SO32- in a flow injection system, the parameters of the system were examined in a fractional factorial design at two levels and the system was then optimized with respect to significant parameters by a super-modified simplex procedure. In the optimized procedure, sample solution (30 µL), delivered at 0.5 mL min-1, was injected into the carrier stream (50 mM Na2B4O7 of pH 8.2; 0.3 mL min-1) and mixed with streams (0.3 mL min-1) of 15 mM I and 10 mM Na2SO3 in 0.1 M Na2B4O7 buffer (pH 10.5). The reaction coil (45 cm) was controlled thermostatically at 70°C, and the derivatization product was determined fluorimetrically (excitation at 365 nm; emission at 425 nm). Under these conditions the detection limit was 1 µM-NH3 and the calibration graph was rectilinear over the range 0 to 50 µM. The coefficient of variation (n = 10) was 1%. Two enzyme systems, incorporating immobilized creatinine deiminase and aspartate ammonia-lyase column reactors, were tested as model systems. The former was used to determine creatinine in serum samples.
Nitrogen Fluorescence

"Design And Properties Of A Flow Injection Analysis Cell Using Potassium-selective Ion-sensitive Field-effect Transistors As Detection Elements"
Anal. Chim. Acta 1991 Volume 245, Issue 2 Pages 159-166
Peter D. van der Wal, Ernst J. R. Sudh&ouml;lter and David N. Reinhoudt

Abstract: The combination of flow injection analysis (FIA) and chemically modified ion-sensitive field-effect transistors (CHEMFETs) is described. In a wall-jet cell, two identical potassium-selective CHEMFETs were used for a differential measurement using a platinum (pseudo-)reference electrode. Silicone-rubber membrane materials, chemically bound to the SiO-2 gate oxide, were used with valinomycin as the ionophore. The optimized FIA system showed a linear response of 56 mV per decade for potassium concentrations above 5 times 10^-5 M. Preliminary results of potassium determinations in human serum and urine samples are presented.
Potassium Serum Human Urine Field effect transistor

"Determination Of Alkanolamines By Ion-pair Chromatography With Chemiluminescence Detection"
Anal. Chim. Acta 1991 Volume 246, Issue 2 Pages 447-450
Paul J. Worsfold, Bolei Yan

Abstract: Ethanolamine, diethanolamine and triethanolamine are separated by ion-pair chromatography on an ODS column and detected by their suppressive effect on the copper(II)- or cobalt(II)-catalyzed chemiluminescence emission from the luminol reaction. Post-column reaction conditions were simplex optimized using a flow injection manifold. Limits of detection (twice the peak-to-peak noise) for ethanolamine, diethanolamine and triethanolamine was 0.8, 1.2 and 0.2 nmol, respectively.
Alkanolamines Ethanolamine Diethanolamine Triethanolamine LC Chemiluminescence

"Continuous-flow Tristimulus Colorimetry: A New Approach For Gradient Scanning Techniques"
Anal. Chim. Acta 1991 Volume 252, Issue 1-2 Pages 133-144
S. Sagrado Vives*, M. J. Medina Hern&aacute;ndez, J. L. Mart&iacute;n Herrera and G. Ramis Ramos

Abstract: A flow injection gradient scanning technique for color evaluation by means of tristimulus colorimetry is described. Equipment and data acquisition requirements are discussed. The program CHROMA.FIA for data treatment and comparative chromatic analysis is presented. The chemical and flow conditions were optimized. Comparative studies using metallochromic indicators with both the flow injection and the conventional batch process were made. The continuous-flow procedure provides good results and is more than 15 times faster than the manual titrimetric procedure.
Spectrophotometry

"Mathematical Modeling Of Single-line Flow Injection Analysis Systems With Single-layer Enzyme Electrode Detection. 3. Experimental Verification Of The Model"
Anal. Chim. Acta 1991 Volume 254, Issue 1-2 Pages 167-175
Spas D. KolevG&eacute;za Nagy and Ern&ouml; Pungor

Abstract: Electrodes were prepared by immobilization of glucose oxidase and urease, each by two techniques, and the effects of the initial substrate concentration, the enzyme concentration. in the reaction layer, its thickness and the buffer concentration. on the output signal were determined. The results agreed well with predictions by a mathematical model for such systems.
Electrode

"Design And Optimization Of A Flow Injection System For Enzymic Determination Of Galactose"
Anal. Chim. Acta 1991 Volume 254, Issue 1-2 Pages 201-208
K. S. Kurtz and S. R. Crouch

Abstract: Galactose was oxidized with immobilized galactose oxidase, the H2O2 produced was treated with leucomalachite green - peroxidase reagent and the product was monitored at 620 nm. Four reactor configurations were investigated, a packed-bed one giving the best results. The calibration was rectilinear up to 1.75 mM with a detection limit of 80 µM and a coefficient of variation (n = 3) from 0.02 to 2.45%.
Galactose Spectrophotometry

"Use Of Flow Injection In The Study Of Micellar Interactions"
Anal. Chim. Acta 1992 Volume 256, Issue 2 Pages 225-230
M. de la Guardia* and E. Peris-Cardells

Abstract: It is shown how the optimum surfactant concentration. for a particular flow injection fluorimetric determination can be established. Calibration graphs are presented for 5-amino-2-benzothiazol-2-ylphenol in water and in the presence of 1% of hexadecyltrimethylammonium bromide, 8% of Triton X-100, 8% of polyoxyethylene glycol nonylphenyl ether or 3.5% of Na dodecyl sulfate; the micellar enhancement of fluorescence (MEF) values are tabulated. The principles of flow injection and dilution, in a mixing chamber, were applied in the development of a rapid method for the study of the interaction between micelles and fluorescent molecules. A single channel manifold, with a well stirred mixing chamber, was used in different studies on the interaction of fluorescent probes with surfactants. The appropriate dilution of concentrated surfactant solutions, in the presence of a fluorescent probe, with a carrier containing the same probe provided information about the effect of the surfactant concentration in the fluorimetric determination of 2-(4-amino-2-hydroxyphenyl)benzothiazole (PAS-S). The dilution of a concentrated solution of a fluorescent molecule in a flow stream containing a surfactant allowed the corresponding fluorimetric calibration graph to be established in few minutes, and from that the micellar enhancement of fluorescence (MEF), in different media, could be easily determined These procedures were applied to the interaction between micelles of anionic, cationic, and non-ionic surfactants and PAS-S. The results obtained were compared with those found in batch analysis.
Fluorescence

"Influence Of The Main Parameters Of A Parallel-plate Dialyzer Under Laminar Flow Conditions"
Anal. Chim. Acta 1992 Volume 257, Issue 2 Pages 317-329
Spas D. Kolev* and Willem E. van der Linden

Abstract: A math. model describing the mass transfer in a parallel-plate dialyzer with cocurrent laminar flow in both channels based on the Navier-Stokes equations and Fick's 2nd law was developed. Numerical solutions are presented for pulse- and stepwise concentration. changes of the solute in one of the channels using the Laplace transform technique. By simulation the effect of the main design and operational parameters of the dialyzer and the most important phys. constants for the mass-transfer process were investigated. Conclusions with regard to optimum design and operation were drawn and some possibilities for simplifying the model were established.

"Improved Spectrophotometric Determination Of Lactose In Milk Using Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 258, Issue 1 Pages 141-149
Dyer Narinesingh*, Valerie A. Stoute, Gershwin Davis and Deenesh Persad, That T. Ngo

Abstract: Samples were diluted with water, treated with protein precipitating reagent (25 g of zinc acetate and 12.5 g of phosphotungstic acid dissolved in water, mixed with 20 mL of anhydrous acetic acid and diluted to 100 mL with H2O), set aside for 10 min and filtered. The filtrate was made alkaline by addition of 1 M NaOH and filtered. A 200 µL portion of the filtrate was injected into a carrier stream (0.7 mL min-1) of glycine - 0.385 M NaOH buffer of pH 12.7 (3:17) containing 0.5% methylamine hydrochloride and 0.02 M sodium sulfite and the mixture was passed through a heating coil (2.5 m long) operated at 80°C before its absorbance was measured at 540 nm. Under optimum conditions, the calibration graph was rectilinear for 1 (detection limit) to 8 mg mL-1 of lactose. Results agreed well with those obtained by LC (details given). Milk samples were analyzed spectrophotometrically for their lactose content using flow injection analysis The methodology is based on the carmine color that develops (λmax = 540 nm) when lactose reacts with alkaline methylamine (pH 12.7). Lactose concentrations as low as 0.6 mg/mL can be readily detected and up to 40 samples can be analyzed per h. Excellent correlations are obtained when the results are compared with the batch and liquid chromatography methods for lactose determination Interference from maltose, if present, should be eliminated by pretreatment with maltase.
Lactose Cow Spectrophotometry

"Rapid PK Measurements For Multibasic Weak Acids By Gradient Flow Injection Titration"
Anal. Chim. Acta 1992 Volume 258, Issue 2 Pages 259-267
David R. Turner*, Margarida M. Correia dos Santos, Paulo Coutinho and Maria de Lurdes Gon&ccedil;alves, Susan Knox

Abstract: The pK values of phthalic acid, phosphoric acid and EDTA (pK2, pK3 and pK4 only) were determined by rapid gradient flow injection titration Key factors in experimental design was investigated, viz. pH range of the titration, direction of titration, flow-rate and weak acid concentration. Under optimum conditions, the technique is well suited to the determination of pK values with a precision of 0.01-0.05 pK and in good agreement with literature values. It is less well suited than conventional batch titration to the determination of very low or high pK values at low weak acid concentrations.
Phthalic acid Phosphoric acid EDTA Acids, weak

"Continuous-flow Method For The Determination Of Aromatic Aldehydes"
Anal. Chim. Acta 1992 Volume 258, Issue 2 Pages 253-258
Mayda Lopez-Nieves, Peter D. Wentzell and S. R. Crouch*

Abstract: The reaction of o-dianisidine and aromatic aldehydes was adapted to an air-segmented continuous-flow analysis system. Stannic chloride was used as the catalyst. Figures of merit of the automated method (e.g., sensitivity, limits of detection, and accuracy) are reported for 13 aromatic aldehydes. The results of selectivity and interference studies are also reported.
Aldehydes, aromatic

"Gas Permeation And Preconcentration In The Flow Injection Determination Of Acid-available Cyanide In Waste Water"
Anal. Chim. Acta 1992 Volume 259, Issue 1 Pages 45-52
Vlastimil Kub&aacute;

Abstract: The optimization of a method involving oxidation of CN- to CNCl and chromogenic reaction with isonicotinate - 3-methyl-1-phenyl-2-pyrazoline-5-one (I) is described, and a flow injection system for application to waste water samples is illustrated. The sample is mixed with 0.1 M H3PO4, and the HCN liberated passes through a silicone rubber membrane in a gas permeation unit into a stream of 25 mM NaOH. This solution is sequentially mixed with 0.1% chloramine T solution in 0.25 M phosphate buffer of pH >8 and with 0.24 M Na isonicotinate - 1 mM I, and the absorbance of the blue final product is measured at 544 nm. Most interference, including that of SCN-, is avoided by the gas permeation technique. With pre-concentration. for 2.5 min in the permeation unit, the detection limit was 3 µg L-1 of CN-. A method for the determination of CN- is based on the reaction with Na isonicotinate-3-methyl-1-phenyl-2-pyrazolin-5-one. A reaction mechanism is proposed. The method allows a fast and sensitive determination.
Cyanide Waste Spectrophotometry

"Response Time Phenomena Of Coated Open-tubular Solid-state Silver Halide-selective Electrodes And Their Influence On Sample Dispersion In Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 381-390
Jacobus F. van Staden

Abstract: A comparative study has been made of the response times of coated open-tubular Ag membrane electrodes selective towards Cl-, Br- or I- (cf. Ibid., 1986, 179, 407) as they affect the throughput of flow injection analysis systems. The tubular indicator electrodes were used in conjunction with an Orion 90-02 double-junction reference electrode with 10% KNO3 solution in its outer chamber. The digitized signals were smoothed by applying the DS (data sets) Cat and Smooth operations of the ASYST software; typical background-corrected graphs for the flow injection measurement of halides (10 to 5000 mg l-1) are reproduced. Examination of the leading edges of the various peaks showed that their rate of response was independent of concentration. and did not significantly decrease the sampling rate, although the response of the Br- electrode at the initial peak-formation stages near the baseline was slightly slower than that of the others. The rate of response of the trailing edges was mainly responsible for the sampling rate in an optimized flow injection system, and the I- electrode showed a memory effect, which was largely responsible for the low sampling rate of this system compared with similar systems with the other two electrodes. The contribution of the memory effect or response time phenomena of coated open-tubular solid state chloride-, bromide-, and iodide-selective electrodes on the anal. output in flow injection systems are presented for concentration. ranges between 10 and 5000 mg L-1. The rate of response for the leading edges of all three electrodes due to electrode properties are independent of concentration. and do not contribute significantly to any decrease in sampling rate, although the rate of response of the bromide-selective electrode flow injection analysis (FIA) system seems to be slightly slower than the other two electrode systems at the initial peak-formation stages near the base line. The rate of response for the tailing edges of the different electrodes due to electrode properties is mainly responsible for the sampling rate obtained in an optimized FIA-ISE system. The memory effect of the iodide-selective electrode is mainly responsible for the fact that the sampling rate of this system is very much lower than the sampling rate obtained for similar systems with the other two electrodes. For the bromide-selective electrode system, the slower rate of response due to electrode properties at the tailing edges (especially with high concentrations of bromide) than that of the chloride-selective electrode, contributes mainly to a lower sampling output for the bromide-selective electrode-FIA system when compared with the chloride electrode system.
Bromide Chloride Iodide Electrode Electrode Electrode

"Sandwich Techniques In Flow Injection Analysis. 3. Simultaneous Determination Of Chromium(VI) In Two Concentration Ranges"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 219-223
J. Alonso-Chamarro*, J. Bartrol&iacute; and R. Barber

Abstract: A diagram is shown of the manifold, equipped with an eight-port switching valve, in which the sample is 'sandwiched' between two flows of 1,5-diphenylcarbazide (I) solution of different concentration. and absorbance measurements (at 540 nm) are made at the two sample - reagent interfaces; peak height is evaluated. Reagent 1 comprises 0.25 mM I and reagent 2 contains 1 mM I, each in 0.04 M H2SO4. By this means, two calibration ranges, from 0.02 to 1.0 and from 1 to 30 ppm (curvilinear) of Cr(VI), can be covered; the corresponding detection limits are 0.01 and 0.5 µg mL-1. Sample throughput is ~45 h-1 and the coefficient of variation is 1%. The method has been applied to the output from a pilot plant used to remove Cr(VI) from leather-factory waste water. A flow injection system based on the sandwich technique is proposed for the determination of Cr(VI). Two simultaneous working ranges of concentration. are achieved by appropriate selection of the reagent composition at the two reagent-sample interfaces. The optimized system allows the determination of Cr(VI) at levels up to 1 µg mL-1 with a detection limit of 0.01 µg mL-1 for one of the interfaces. For the other, determinations up to 30 µg mL-1 with a detection limit of 0.5 µg mL-1 are possible. The sample throughput achieved was about 45 h-1 with a relative standard deviation <1% in the middle of both ranges. The method was applied to determine Cr in water.
Chromium(VI) Industrial Spectrophotometry

"Flow Injection Amperometric System For Enzyme Immunoassay"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 45-52
D. M. Ivnitskii*, R. A. Sitdikov and V. E. Kurochkin

Abstract: A mathematical model has been developed for describing and thus optimizing the operation of a flow injection amperometric detector with a Pt-wire working electrode and a Ag - AgCl (saturated KCl) counter electrode, which was used with a continuously circulating carrier solution of 0.1 M acetate buffer of pH 4.2 containing 0.1 M KCl for the detection of enzymatically produced iodine (from enzyme immunoassay of IgE with a commercial kit) in the injected sample. The agreement between calculated and experimental analytical parameters was satisfactory. Simultaneous evaluation by means of a photometric ELISA reader showed that the electrochemical sensor could be used to determine 1.5 to 100 kiu L-1 of IgE in blood. The technique could be used in conjunction with appropriate immunosorbents for the immunoenzymatic determination of hormones, enzymes, drugs, antibodies and viruses. A flow injection amperometric system was developed for monitoring the results of enzyme immunoassay. The operation of the flow-through amperometric detector is described by a limiting current equation for the working wire electrode. The possibility of the optimization of the geometry and hydrodynamic properties of amperometric detectors in flow systems was demonstrated. The flow system was tested in the determination of peroxidase and IgE in blood serum. Peroxidase (marker enzyme) was determined in the concentration. range 5 x 10^-12 - 4 x 10^-10 M. The detection limit for IgE in blood serum was 3.1 ng mL-1. The sample throughput was 400 hr-1.
Immunoglobulin G Enzyme, peroxidase Blood Serum Amperometry Immunoassay Electrode

"Flow Injection Fourier Transform Infrared Spectrometric Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 53-57
M. de la Guardia*, S. Garrigues and M. Gallignani, J. L. Burguera and M. Burguera

Abstract: A µflow cell with KBr windows (Specac, Orpington, UK) and a demountable µflow-through cell (Spectra Tech, Warrington, UK) were used in a Perkin-Elmer model 1750 FTIR spectrometer with data station to detect o-xylene (as test species) injected into a stream of hexane. Programs were written to obtain and accumulate the IR spectra (820 to 670 cm-1) of the sample zone, which took only 19 s. The effects of cell thickness, injection volume and carrier flow rate on the sensitivity, limit of detection and reproducibility of measurement were assessed. A flow rate of 0.5 mL min-1 gave the best results, and a resolution of 4 cm-1 afforded good sensitivity and reproducibility. The two cells showed similar performance. A limit of detection of 0.01% (v/v) was attainable, and for 0.4% of o-xylene the coefficient of variation was ~1% (n = 5). A method has been developed for obtaining and storing the complete Fourier transform spectrum, of a sample in a flowing stream in only 19 s. A resolution of 4 cm-1 is recommended. The determination of o-xylene in xylol was employed as a test system, using hexane as a carrier and diluent in all the experiments A classical liquid flow cell and a demountable flow-through cell were compared. The best limit of detection obtained was 0.01%(v/v). The effects of flow-rate and injection volume were studied for the two cells used. The relative standard deviation (0.4% o-xylene, n = 5) was ~1%.
2-Xylene Organic compound Spectrophotometry

"Simultaneous Flow Injection Analysis For Two Components With Online Dialysis And Gas Diffusion In Series. Determination Of Chloride And Ammonia-nitrogen In Industrial Effluent Water"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 453-459
Jacobus F. van Staden

Abstract: A system is described and illustrated for the simultaneous determination of Cl- and ammonia-N. The sample plug (50 µL) from a single injection, in water as carrier, is routed first to the donor channel of a dialyser, where the Cl- diffuses into H2O; the diffusate is mixed with a reagent containing Hg(SCN)2 and Fe(NO3)3 in aqueous methanolic HNO3 before absorbance measurement at 480 nm. The sample plug is then treated with 0.1 M NaOH and passed to a diffusion unit, where the liberated NH3 passes into an indicator stream containing Tecator NH3 mixed indicator buffered at pH 5.0; the absorbance of the resulting solution is measured at 590 nm. Under optimized conditions, coefficient of variation were 0.8% for Cl- and 1.0% for NH3 in samples containing 127 to 2531 and 10 to 1000 mg L-1 of the respective analytes. The sampling rate was 100 h-1. Online dialysis and gas diffusion were combined for the simultaneous determination of >1 components in a single flow injection analysis system. A fast and reliable fully automated 2-component flow injection procedure is described in which a single sample (e.g., 50 µL of industrial effluent water) is injected into a carrier stream and sequentially dialyzed for the determination of Cl- and gas diffused for the determination of NH3. The results obtained for the Cl- and NH3 in industrial effluent water at a sampling rate of 100/h compared well with those obtained by standard methods.
Chloride Ammonia Industrial Spectrophotometry

"In-flow Speciation Of Copper, Zinc, Lead And Cadmium In Fresh Waters By Differential-pulse Anodic Stripping Voltammetry. 1. Optimization Of Filtration And Enrichment Steps"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 323-334
W. Martinotti* and G. Queirazza, F. Realini, G. Ciceri

Abstract: An automatic system for the in-situ determination of dissolved Cu, Zn, Pb, and Cd in fresh waters, composed of a filtration unit, a separation and enrichment unit, and an electrochemical unit for differential-pulse anodic stripping voltammetry, was investigated. The filtration and enrichment units were designed to establish the most effective experimental conditions for the measurement of the metal concentrations at environmental levels. The system was built for installation in a buoy equipped with a facility for radiotransmission of the data obtained.
Copper Zinc Lead Cadmium River Voltammetry

"Aspects Of Sample Dispersion For Optimizing Flow Injection Analysis Systems"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 539-548
Takashi Korenaga

Abstract: Details are given of an apparatus with a micro-scale laboratory-made flow-through photometric detector that permits measurements to be carried out without disturbance of laminar flow. This apparatus was used to study the solute dispersion of an injected sample plug in order to develop a hydrodynamic model for designing sensitive and precise flow injection analysis systems. A range of operating conditions was evaluated, and the use of a double-plunger micro-pump with a linear cam mechanism and a short reciprocation time (cf. Korenaga et al., Anal. Sci., 1991, 7, 515) is recommended to achieve smooth mixing and stable pumping with good reproducibility. Solute dispersion of an injected sample plug was studied by using an experimental app. with ideal laminar flow in order to develop a hydrodynamic model for the design of sensitive and precise flow injection analysis systems. The dispersion behavior of the sample slug under different manifold conditions was first studied in detail to evaluate the effects of various operating conditions such as tube radius, tube length, flow-rate, and mol. diffusion coefficient of sample solute. The capillary flow properties were also examined for some commercial micropumps to select the most suitable pumping method. Mixing profiles and baseline stability in short, straight tubes were investigated. A double-plunger micropump having a linear cam mechanism and a fast, short reciprocation time was proposed to obtain smoother mixing and more stable pumping with good reproducibility. Complete mixing and low flow-rate pumping are strongly desired for reliable flow injection methods for industrial process use; biosensing devices for protein and enzyme bioassays require lower consumption of valuable reagents.
Spectrophotometry

"Experimental Fluctuations Of Flow Injection Signals"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 533-538
M. F. Gin&eacute;*, R. L. Tuon, F. J. Krug and M. A. Z. Arruda

Abstract: Flow injection experiments, in a single-line system, involving (a) the dispersion of Eriochrome cyanine R (C. I. Mordant Blue 3) in a stream of 0.2 M ammonium acetate buffer (pH 4.7) and (b) the determination of NO2- with sulfanilamide and N-(1-naphthyl)ethylenediamine were used in investigating the effects of flow rate, injection volume and reaction coil length on the fluctuation of the spectrophotometric detector signal. Measurements at 530 nm made at different points along the dispersed zone were analyzed by a bi-level factorial design to obtain the main and interaction effects of the parameters. Large variations in precision were found along the profiles produced by systems with medium or limited dispersion; measurements of peak height were more precise than those of peak area. An experimental factorial design is proposed for investigating the effects of flow-rate, injection volume, and coil length on the fluctuations of flow injection signals. The precision of the spectrophotometric data at different points along the profile produced by dispersing a dye solution or by processing the modified Griess reaction for NO2-N and its dependence on the single-line flow injection parameters were evaluated. Large variations of the relative standard deviation were found along the profiles produced by medium and limited dispersed systems. The peak max. and five subsequent points in the trailing portion of the dispersed signals were characterized by the best homogeneity of variance. Anal. of the fluctuations revealed that the interaction between the studied parameters was always significant. The errors inherent in peak-height and peak-width measurements are discussed.
Eriochrome cyanine R Spectrophotometry

"Flow Injection Analysis In The Evaluation Of Supported Liquid Membranes"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 441-451
D. E. Barnes*, J. F. van Staden

Abstract: For the study of supported liquid membranes for use, e.g., in metallurgical extractions and other technological separations, a unit comprising the liquid membrane supported between two pieces of clear PVC separated by a sheet of poly(vinylidene fluoride) and provided with a milled channel was incorporated into a flow injection arrangement. The feed solution (Cu in a buffer solution of pH 1.2 to 12.6) was pumped over the supported liquid membrane [bis-(2-ethylhexyl) hydrogen phosphate in diethylbenzene as optimum solvent] and the stripping solution (e.g., 0.25 M HNO3) was pumped through the unit on the other side of the membrane. The stripping stream was then injected into a carrier reagent stream [12 mM 4-(2-pyridylazo)resorcinol in NH3 - acetic acid buffer of pH 4.5] before passage to the spectrophotometric detector. The system allowed the effects of such parameters as flow rate and composition of the various liquids to be evaluated rapidly. Supported liquid membranes (SLMs) have been used for the selective separation and pre-concentration of numerous compounds Existing optimization procedure for SLM systems is a manual and time-consuming process. The new concept is proposed of using a flow injection analysis (FIA) manifold, linked to a flow-through SLM unit, to study and optimize SLMs. FIA was used to study the characteristics of a cationic SLM and the effect of various conditions on the operation of this SLM. Parameters such as flow-rate and the chemical compositions of the feed solution, the stripping solution, and the membrane were evaluated. In addition, FIA allowed various SLMs, containing different organic diluents, to be evaluated in a short time.
Copper Spectrophotometry

"Flow Injection Determination Of Low Levels Of Ammonium Ions In Natural Waters Employing Preconcentration With A Cation-exchange Resin"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 339-343
Marina Menezes Santos Filha, Boaventura Freire dos Reis and Henrique Bergamin Fo.*, Nivaldo Baccan

Abstract: Methods used to determine the effects of sampling time and of flow rates of sample and eluent are described, results from which led to the system described and illustrated. The water sample (freed from dissolved organic matter by C18 resin) is passed through a column (9 mm x 4 mm) of Bio-Rad AG 50W-X8 resin (100 to 200 mesh; H+ form), and the adsorbed NH4+ is eluted with 0.5 M NaOH. The eluate is mixed with Nessler reagent (a solution of 14 g of KI in 50 mL of water is treated with saturated Hg2Cl2 solution until a faint reddish color persists, then 50 mL of 10 M NaOH is added and the solution is diluted to 500 ml; this solution is diluted 1:3 with 1 M NaOH before use) before passage through a 1-m reaction coil to a spectrophotometric detector at 410 nm. The flow system includes a step for regeneration of the resin with HCl. The detection limit is 3 µg L-1 and sample throughput is 40 h-1 for samples containing 50 to 500 µg L-1 of NH4+. Reagent consumption is only 50 µL per determination, and results on nine water samples agreed with those by the indophenol blue method. NH4+ in natural waters at the 50 µg/L level were determined using Nessler reagent after pre-concentration. in a cation-exchange column coupled to a flow injection analysis (FIA) system. The loading cycle, the elution cycle, and the regeneration cycle were programmed for the resin used. The zone sampling approach using a computer-controlled commutator was employed in the FIA system design. Flow rates, resin loading, elution time, loop dimensions and resampling times for the zone sampling, column and coil dimensions, sensitivity, and reproducibility were studied. The detection limit was improved 10-fold over an earlier method that did not use a concentration. step. A throughput of 45 sample analyzes/h was achieved for samples with concentrations. ranging from 50 to 500 µg/L. The results show agreement of better than 99% with those obtained by the manual procedure.
Ammonium Environmental Ion exchange Spectrophotometry

"Determination Of Free And Combined Residual Chlorine By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 233-240
Krishna K. Verma, Archana Jain and Alan Townshend*

Abstract: Optimized conditions are described for determining free and combined residual Cl. For 0.5 to 40 µg mL-1 of free Cl, 50 µL of sample solution is injected into 0.25 M HCl (1 mL min-1) as carrier and the stream is merged with 16 mM 4-nitrophenylhydrazine (I) in 60 mM HCl (0.5 mL min-1). After passage through a 75-cm coil, the stream is merged with aqueous 0.3% N-1-naphthylethylenediamine hydrochloride (1 mL min-1) coupling reagent and passed through a 70-cm coil before detection at 532 nm. To determine similar concentration. of total residual Cl, the I reagent also contains 20 g L-1 of KBr, with which both types of residual Cl react; the Br thus produced acts as the oxidizing agent. Combined residual Cl is determined by difference. A reagent-injection variant is used to determine 0.05 to 10 µg mL-1 of analyte. Response is rectilinear over both the cited ranges, and the detection limit is 0.03 µg mL-1 by the reagent-injection method. Sample throughput is 110 h-1. Chlorine dioxide interferes, but ClO3-, ClO2-, NO3-, up to 3 µg mL-1 of NO2- and a range of other ions are tolerated. The method does not distinguish between chloramine and dichloramine. The method was applied to Cl-doped model samples, and results agreed well with those obtained by flow injection spectrophotometry with NN-diethyl-p-phenylenediamine and by iodimetric titration. A new reaction scheme to determine free residual Cl in the presence of other Cl species, viz. ClO2-, ClO3-, and ClO2, was evaluated. The scheme is based on the oxidation of 4-nitrophenylhydrazine by free Cl to the 4-nitrophenyldiazo cation and its electrophilic coupling with N-(1-naphthyl)ethylenediamine dihydrochloride to give an azo dye with an absorption max. at 532 nm. Flow injection systems are proposed to determine 0.05-10 µg/mL free Cl by the reagent-injection technique, and 1-40 µg/mL free Cl by sample injection. The limits of detection of free Cl and mean relative standard deviation (range) were 0.03 µg/mL and 0.9% (0.6-1.2%), and 0.4 µg/mL and 0.6% (0.4-0.8%), respectively. Only ClO2 interferes. The results were in good agreement with those obtained by flow -injection N,N-diethyl-p-phenylenediamine spectrophotometric and classical iodometric titration methods. Since chloramines do not interfere in free Cl determination, a method was developed to determine total Cl (and hence of combined Cl by difference after determination of free Cl) utilizing a secondary reaction of both free and combined Cl with Br- to yield Br which then acts as oxidizing agent. The sample throughput was 110/h in both methods.
Chlorine, free Chlorine, residual Spectrophotometry

"High-sensitivity Flow Method For The Determination Of Proteins With Micro-flow Plunger Pumps"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 67-74
Takashi Korenaga*, Xiaojing Zhou, Miyoko Izawa, Teruo Takahashi and Tosio Moriwake, Sumio Shinoda

Abstract: Proteins were determined by the dye association method with use of Coomassie Brilliant blue G250 (C. I. Acid Blue 90; I) in conjunction with a flow device based on that of Korenaga and Stewart (Ibid., 1988, 214, 87), which incorporated a double-plunger micro-pump. The device was operated in either flow injection or continuous-monitoring mode (manifolds illustrated). For the former, the sample solution (8 µL) was injected into a stream (0.02 mL min-1) of 0.1 M K2HPO4 - KH2PO4 (pH 7.4) which was then merged with 60 µM-I in 2.8% HClO4, also at 0.02 mL min-1, in a Ti reaction tube (20 cm x 0.5 mm i.d.) before passing through a spectrophotometric flow cell for absorbance measurement at 600 nm. In the continuous mode, the aqueous sample solution and the I reagent (each at 0.02 mL min-1) were mixed in a Ti tube (10 cm x 1 mm i.d.) before entering the flow cell. The best calibration graphs were obtained at low flow rates. Titanium reaction tubes were used because of unstable baseline absorbance obtained with PTFE tubes. For bovine serum albumin determined by the flow injection method, the calibration graph was rectilinear up to 140 µg mL-1, and the standard deviation (n = 10) was 1.5 ng mL-1 at 1.0 µg mL-1. The method was successfully applied to urine samples. To determine microamounts of proteins with low mol. diffusivity, a flow method was developed by both miniaturizing the common flow-injection apparatus and using the dye association method. A very precise double-plunger micropump, which was recently developed for this purpose, was used. The optimum conditions using bovine serum albumin (BSA) as standard and some ion-association dye reagents at very low flow-rates were examined A flow-rate of <50 µL/min was acceptable when a short, small-bore reaction tube was used. Up to 15 samples/h could be analyzed with a relatively long residence time; linear calibration graphs were obtained with both 8 µL volume loop valve injection and no-injection methods. The detection limit and relative standard deviation of the injection method were 0.003 µg/mL and 0.15%, respectively, for BSA.
Albumin Proteins Urine Cow Serum Spectrophotometry

"Flow Injection Analysis Of Micromolar Concentrations Of Glucose And Lactate In Fermentation Media"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 145-153
Stig Benthin*, Jens Nielsen and John Villadsen

Abstract: Samples (8 ml) of fermentation liquor are mixed with 0.8 mL of 6.6 M HClO4 and cooled in ice for 15 min to quench metabolic activity, then adjusted to pH 6.3 with 6.6 M KOH and diluted to 12 mL. The ppt. is centrifuged off and 500 µL of supernatant solution is injected into 10 mM phosphate buffer of pH 6.3. The stream is passed through a reactor containing lactate oxidase or glucose oxidase immobilized on a nylon tube, and is then merged with luminol - Fe(III) reagent for spectrophotometric determination of the H2O2 produced. A reactor in which the nylon tube was knitted in a figure-of-eight shape around two glass spatulas (diameter 4 mm) gave better conversion than one with the tube coiled around a cylinder (diameter 10 mm). With use of the purer (USB 16135; 300 iu mg-1) of two glucose oxidase preparations, the calibration graph (based on peak heights) was rectilinear up to almost 200 mg l-1. The upper rectilinear limit for lactic acid was ~50 mg l-1. Limits of determination were 50 and 150 µg L-1 for lactic acid and glucose, respectively. The technique was used to study bacterial and yeast fermentations, especially the product formation pattern at very low glucose concentration. and the microbial preference for α- or β-glucose. Flow injection analyzers for glucose and lactate were optimized for the measurement of very low concentrations. in complex fermentation media. The analytes were enzymatically oxidized and the H2O2 formed was detected by chemiluminescence. The enzymes were immobilized on a nylon tube and, by measuring the flow-rate dependence of the conversion of H2O2 by catalase, the performance of differently combined enzyme reactors was evaluated. In the resulting glucose and lactate analyzers, the limits of determination in aqueous solutions were 50 µg lactic acid/L and 150 µg glucose/L. When measuring glucose concentrations. in the range 0.5-10 mg/L, the purity of the enzyme used in the analyzer must be high. The analyzers were used to study bacterial and yeast fermentations, in particular the product formation pattern at very low glucose concentrations. and the microbial preference for α- and β-glucose.
Glucose Lactate Fermentation broth Chemiluminescence

"Flow Injection Atomic Spectrometry: A New Analytical Technique"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 75-85
Julian F. Tyson*, S. R. Bysouth, E. A. Grzesczyk and E. Debrah

Abstract: The literature on flow injection analysis coupled with atomic spectrometry is reviewed. Several types of closed-loop recirculating manifolds for particular applications are described, viz, for calibration, dilution, acid-leaching of Ca, and Ag matrix removal in AAS. The performance of each of the manifolds was satisfactory at recirculating flow rates up to 10 mL min-1. (75 references). Much of the recent research in analytical atomic spectrometry has been concerned with problems of a practical nature. In particular, the inaccuracies arising from a variety of matrix effects and the limitations of sample introduction systems have provided a considerable driving force for recent developments in the various techniques. The philosophy of attempting to eliminate, or compensate for, interferences by procedures implemented at the atomization stage has had success for electrothermal atomization atomic absorption spectrometry but has proved of limited utility for other techniques. Despite considerable efforts, solid-sample introduction is still best done by procedures whose initial stage is dissolution There is a steady growth in the flow injection atomic spectrometric literature and a survey of the ~50 publications in 1990 shows that much of the interest is now centered on coupling pre-concentration and matrix removal procedures with atomic spectrometry, although there is still work concerned with the basic characteristics of flow injection introduction, such as the reduction in sample loading, online dilution for calibration purposes and the ability to handle small sample volumes, being published. The role of the flow injection valve as an interface between flow systems is highlighted. This interface allows independent optimization of the various flow systems coupled in this fashion. Several possible applications of recirculating closed-loop manifolds are described. These include the serial dilution of a stock standard for calibration purposes and to establish a working detection limit. This is illustrated by the dilution of a 2.45 mg L-1 solution of magnesium by a factor of 2.20 per injection. This procedure established a detection limit for the instrument involved of between 4.2 and 5.2 ng mL-1. The online acid leaching of calcium from charcoal is shown to be sufficiently precise for the basis of a rapid screening procedure and the determination of copper in matrixes containing up to 50 g L-1 silver is made possible by the online precipitation of the matrix as the chloride in a circulating loop containing a filter column of nylon fibers. The additional possibilities afforded by these designs of manifold and the great variety of manifolds described in the literature suggest that flow injection atomic spectrometry may be emerging as an analytical methodology analogs to the variety of procedures encompassed by terms such as liquid chromatography in the vocabulary of the analytical methodology for molecular species.
Copper Calcium Spectrophotometry Spectrophotometry

"Chemical Oxygen Demand Determination In Well And River Waters By Flow Injection Analysis Using A Microwave Oven During The Oxidation Step"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 295-299
M. L. Balconi, M. Borgarello and R. Ferraroli*, F. Realini

Abstract: The sample (0.25 ml) is injected into water as carrier and, after mixing, the stream is treated with oxidizing solution prepared by adding dropwise, with vigorous stirring, 10 mL of aqueous 12% K2Cr2O7 to 300 mL of concentrated H2SO4 and diluting the cooled solution to 1 l with concentrated H2SO4. The resulting solution passes through a reaction coil (10 m) enclosed by a microwave oven operated at 180 W and then through a cooling coil and a de-bubbler before absorbance measurement at 445 nm. Under optimum conditions (described), the calibration graph is rectilinear for COD up to 100 mg l-1, and the detection limit is 1.5 mg l-1. The coefficient of variation was 2.1% (n = 20) at 40 mg l-1. Results obtained on well, river and canal water, sewage and food industry waste agreed with those by a standard method. A flow injection method based on the use of a microwave oven to maximize the rate of the oxidation step is described. The flow system consists of 2 lines (water as carrier and K dichromate-H2SO4 mixture as reagent), 3 coils, of which the intermediate one (wound around a special strong microwave absorber support) acts as reaction coil, a membrane degassing unit, and a spectrophotometric detector. Optimal parameters includes the oven capacity at 180 W, application range in 0-100 mg/L COD, relative standard deviation 2.12% at 40 mg/L COD, and detection limit 1.5 mg/L COD. Preliminary applications were made to well water, river water (with low COD levels), and wastewaters. The results obtained are in good agreement with those given by the manual reference method.
Chemical oxygen demand River Well Canal Industrial Spectrophotometry

"Simultaneous Determination Of Nitrite And Nitrate In Water Using Flow Injection Biamperometry"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 391-398
Marek Trojanowicz*, Wojciech Matuszewski and Bogdan Szostek, Jacek Michaowski

Abstract: The sample is injected into a carrier stream of aqueous 0.2% NH4Cl, which is split into two streams; one passes through a 30-cm tube and is then merged with the second stream, which flows through a column (6 cm x 2 mm) of Cd powder (0.1 to 1.5 mm) as reducing agent and a delay coil. The combined stream is mixed with 0.1 M KI - 0.125 M H2SO4 before reaching a detector equipped with two Pt electrodes polarized at 100 mV, where NO2- is detected by means of the I2 - I- redox system (Hulanicki et al., Ibid., 1987, 194, 119). The first peak obtained corresponds to NO2- and the second to NO3- plus NO2-. Under optimized conditions (described), the coefficient of variation for 60 µM-NO2- was 1.4 to 2.2% and that for 60 µM-NO2- and 0.4 mM NO3- was 0.5 to 0.8%. The max. sampling rate was 15 h-1. Copper (3 mg l-1) could be masked with EDTA, >1 mg L-1 of residual Cl had to be removed initially on a charcoal column, Fe(III) could be masked by adding oxalate to the sample before injection, and Cr(VI), which interfered in the determination of NO2-, could be removed by anion exchange at pH 7.8. In the analysis of natural water, results were well correlated with those of ion-selective potentiometry. Detection with 2 polarized Pt wire electrodes is based on the oxidation of I- by NO2-. The current is proportional to the amt. of I formed. The injected sample is split in a flow injection manifold into 2 segments. One of them is transported through a reductor minicolumn containing copperized Cd, where reduction of NO3- to NO2- occurs. The effects of interfering species such as Cu(II), Fe(III), Cr(VI) and residual Cl were examined and procedures for their elimination are proposed. With a sampling rate of 15/h, detection limits of 40 and 70 µg/L were obtained for NO2- and NO3-, respectively.
Nitrate Nitrite Environmental Electrode Potentiometry

"Sensitive Flow Injection Technique For The Determination Of Dissolved Organic Carbon In Natural And Waste Waters"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 287-294
R. T. Edwards, I. D. McKelvie*, P. C. Ferrett, B. T. Hart and J. B. Bapat, K. Koshy

Abstract: The sample was injected into water as carrier and treated with 4.2% K2S2O8 solution in aqueous 3.6% NaBH4.10H2O. This mixture was passed through a PTFE coil (4 m x 0.5 mm) wound round a Gelman Clemco 9002 germicidal tube (40 W) for oxidation of the dissolved organic C, and de-bubbled before the introduction of 1 M H2SO4. The stream was then passed through a knotted PTFE coil (70 cm x 0.3 mm) at 95°C to liberate CO2, which, in a gas diffuser, was absorbed in a stream (pH 9.75) of 0.5 mL of methanolic 1% phenolphthalein and 1.5 mL of 0.25 M Na2CO3 - 0.25 M NaHCO3 buffer diluted with water to 1 L. The final solution was de-bubbled before absorbance measurement at 552 nm. Under optimized conditions the detection limit was 0.1 mg L-1 of C and the rectilinear calibration range extended up to 2 mg L-1; slight modification of the manifold extended the upper limit to 80 mg L-1. Recoveries of C from various organic compounds were essentially quantitative. The method was applied to river and estuarine water and to sewage treatment effluent. A flow injection method for the determination of dissolved organic C (DOC) in natural water and wastewater is based on inline UV photooxidation of DOC to CO2, with spectrophotometric detection. The method is rapid (~45 samples/h), has a linear response of 0.1-2.0 mg/L and a detection limit of ~0.1 mg/L. Minor modifications in the manifold can extend the linear response range to 80 mg/L with a slight increase in the detection limit, making the technique well-suited for the determination of DOC in natural water and wastewater.
Carbon, organic, dissolved Estuarine River Water Spectrophotometry

"Real-time Digital Filters For Signal Processing In Flow Injection Analysis. 2. Practical Applications"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 521-531
Marek Trojanowicz* and Bogdan Szostek

Abstract: The various real-time digital filters described in Part I (see preceding abstract) were evaluated for their effectiveness in flow injection analysis with (a) spectrophotometric, (b) AAS, (c) potentiometric and (d) amperometric detection. The applications were: (a) measurements of bromothymol blue and of the color of water, (b) determination of Cu after pre-concentration. on catechol violet-loaded Amberlite XAD-2 resin, (c) determination of Cl- by using a Ag - AgCl disc electrode in a wall-jet flow cell, and (d) determination of NO2- with an iodine - I- indicator system and two polarized Pt-wire electrodes. The most efficient filters for each system are discussed, and it is demonstrated that signal-to-noise ratios and precision are significantly improved by digital filtering, which eliminates sudden changes in signal that do not originate from the analyte. The improvement is always larger for a digital than for an analogue recording. The low-pass Chebyshev type II digital filter proved to be the most effective in many instances, because it involves the largest number of parameters in optimization of filter performance. Infinite impulse response and finite impulse response digital filters were applied to signal processing in flow injection measurements with UV-visible spectrophotometric, atomic absorption spectrometric, potentiometric, and biamperometric detection. In most cases examined it resulted in an improvement in detectability and the precision of determination Most often the low-pass Chebyshev type II digital filter was the most effective, which can be attributed to the largest number of parameters being used to optimize the filter performance.
Spectrophotometry Spectrophotometry Potentiometry Biamperometry

"Determination Of Lipid Hydroperoxides By Electrochemiluminescence"
Anal. Chim. Acta 1992 Volume 262, Issue 1 Pages 59-65
S. Sakura*, J. Terao

Abstract: Electrochemiluminescence (ECL) was used for the detection of methyl linoleate hydroperoxide (I) at a vitreous-carbon electrode in neutral aqueous acetonitrile medium. The optimum applied potential was 0.7 V, at which only luminol is oxidized. The oxidation product reacts with free I in the solution to emit light. If the applied potential is >1.0 V, then I is also oxidized, causing interference and a more complicated emission. The oxidation products of I were studied. In an optimized flow injection system with use of phosphate-buffered aqueous 30% acetonitrile (pH 7.4) as carrier (0.3 to 0.5 mL min-1) and a luminol concentration. of 10 to 20 µM, the limit of detection was 0.3 nmol. The good sensitivity is due to the short emission lifetime and the fact that photons are generated on a small surface area of the electrode. Compared with conventional chemiluminescence, ECL has the advantage of requiring only a neutral aqueous solution that is similar to biological fluids.
Hydroperoxides, lipid Methyl linoleate hydroperoxide Chemiluminescence Electrode

"Sensitive Flow Injection Spectrofluorimetric Method To Determine Aluminum(III) In Water"
Anal. Chim. Acta 1992 Volume 262, Issue 1 Pages 91-96
Francisco Carrillo, Concepci&oacute;n P&eacute;rez and C&aacute;rmen C&aacute;mara*

Abstract: The proposed method is based on the use of Eriochrome red B (C. I. Mordant Red 7; I) and does not require extraction of the fluorescent complex. The flow injection system (described) was optimized for the effects of pH (6.0), buffer (hexamine or Na acetate), I concentration. (0.025%), reactor coil parameters, flow rate (1 mL min-1) and injection volume (0.1 ml). The carrier was 0.01 M 1,10-phenanthroline - 0.5 M hydroxylammonium chloride, and fluorescence measurements were made with excitation and emission at 525 and 595 nm, respectively. Results were obtained from calibration graphs, which were rectilinear up to 1 µg mL-1 of Al(III) for both buffers; the limits of detection were 0.35 and 0.4 ng mL-1 for the acetate and hexamine buffers, respectively. Selectivity and precision were also excellent and better than obtained by graphite-furnace AAS or other methods. The method was successfully applied to the determination of Al in tap- and mineral waters. A room-temp. flow injection spectrofluorimetric method is presented to determine Al(III), based on the use of Eriochrome Red B in the presence of H2MTA+-HMTA (HMTA = hexamethylenetetramine) or HOAc-OAc- buffer. Various chemical and phys. variables affecting the reaction in the flow system were evaluated. The proposed method is very sensitive, with a detection limit of 0.3 ng/mL and a precision at the 20 ng/mL level of 2.5%. The calibration range is linear 1 µg/mL. The method was successfully applied for determination of Al(III) in tap and mineral waters.
Aluminum(III) Water Mineral Fluorescence

"Comparison Of Electrochemiluminescence And Amperometric Detection Of Lipid Hydroperoxides"
Anal. Chim. Acta 1992 Volume 262, Issue 2 Pages 217-223
S. Sakura*, J. Terao

Abstract: Serum containing uric acid, ascorbic acid and tocopherol interferents was used for comparison of the cited techniques. Cyclic voltammograms were measured, for both methods, at vitreous carbon and Pt electrodes, in a flow injection system with phosphate buffer (pH 7.4) in a 30% acetonitrile solution Optimum conditions for electrochemical oxidation (ECO) were 0.3 to 0.5 mL min-1 flow rate and pH 7 to 8. Pre-treatment to remove uric acid and ascorbic acid is necesssary. Tocopherol does not interfere. Optimum conditions for electrochemiluminescence (ECL) were 0.3 to 0.5 mL min-1 flow rate, 10 to 20 µM luminol and pH of flow solution 7 to 9. Interferents should be removed prior to measurement. Detection limit for ECO at a vitreous carbon electrode was 0.05 nmole, the coefficient of variation (n = 5) was 4.9% and the signal to noise ratio was 1.36. The detection limit for ECL at a vitreous carbon electrode was 0.3 nmole, the coefficient of variation (n = 5) was 1.3% and the signal to noise ratio was 1.5. At a Pt electrode the detection limit for ECL was 0.1 nmole, the coefficient of variation (n = 5) was 5.3% and the signal to noise ratio was 2.5.
Hydroperoxides, lipid Blood Serum Chemiluminescence Amperometry Electrode Electrode

"Co-immobilized Enzyme Columns In Determining Serum Creatinine Using Creatininase, Creatinase And Sarcosine Oxidase By Flow Injection Analysis And Chemiluminescence Detection"
Anal. Chim. Acta 1992 Volume 262, Issue 2 Pages 315-321
Masayoshi Tabata*, Masayuki Totani, Jiro Endo

Abstract: The column of co-immobilized creatininase - creatinase - sarcosine oxidase (2:5:3) was selected from six wt. ratios of the enzymes. In the cited determination, detection was based on the chemiluminometric rate assay of H2O2 produced. The flow rate for luminol, hexacyanoferrate(III) and 10 mM K phosphate buffer (pH 8.5) was 0.6 mL min-1. Total chemiluminescence emission was determined from the area under the light - time curve. The method was compared with the modified Jaffe reaction rate method. The calibration graph was rectilinear up to 1.0 mM creatinine. Within-day and day-to-day coefficient of variation (n = 10) were 2.4 and 3.7%, respectively. Creatinine recovery was 97 to 101%. The title method was based on the chemiluminometric rate assay of hydrogen peroxide produced from creatinine by consecutive reactions of three immobilized enzymes. The procedure is independent of the concentration. of endogenous creatine in serum, although creatininase catalyzes the reversible reaction. Further, because of the shifts of pH optima caused by immobilization of the three enzymes, successive reactions could be carried out under almost optimum conditions at pH 8.5. The method was found to give perfect calibration linearity, with accurate recoveries ranging from 97 to 101% for up to 1.0 mM creatinine. The within-day and day-to-day relative standard deviations (n = 10) were 2.4% and 3.7%, respectively, for 0.10 mM creatinine and 1.6% and 2.1%, respectively, for 0.96 mM creatinine. The results correlated satisfactorily with those obtained by the modified Jaffe reaction rate method.
Creatinine Blood Serum Chemiluminescence

"'Intelligent' Analytical Subsystems For On-line Control And Monitoring Of Bioprocesses"
Anal. Chim. Acta 1992 Volume 265, Issue 1 Pages 63-69
Claudio Filippini*, Bernhard Sonnleitner and Armin Fiechter

Abstract: The concepts of different methods of automated control are described and the requirements for an intelligent analytical subsystem are discussed. As an example, the hardware and software required for the optimized control of a biotechnological process flow injection system are detailed.

"Fluorimetric Determination Of Samarium(III) And Europium(III) In Neodymium Oxide By Separation With A Resin Column"
Anal. Chim. Acta 1992 Volume 266, Issue 1 Pages 67-71
Shaorong Liu* and Jian Meng, Wenhua Liu

Abstract: As only a limited amount of Nd is tolerated when the 2-thenoyltrifluoroacetone - 1,10-phenanthroline - Triton X-100 method (cf. Taketatsu and Sato, Ibid., 1979, 108, 429) is used to determine Sm or Eu, online separation of the Nd from the analytes is carried out with use of a column of P507 resin (75 mesh), which contains 2-ethylhexyl 2-ethylhexylphosphonate. The flow injection manifold used is shown diagrammatically. The optimum eluent is 0.25 M HCl - 0.5 M NaCl. By using the standard addition method, Eu can be determined without interference from Sm in up to 40-fold amount; interference by Eu in the determination of Sm is corrected for by blank subtraction and application of the standard addition method. The method was applicable in the analysis of Nd2O3 containing >0.05% of Sm and >0.005% of Eu.
Samarium Europium Inorganic compound Fluorescence

"Determination Of Total Soil And Plant Nitrogen Using A Micro-distillation Unit In A Continuous-flow Analyser"
Anal. Chim. Acta 1992 Volume 266, Issue 1 Pages 113-117
S. McLeod*

Abstract: Soil and plant samples were digested as described earlier ('Notes on Soil Techniques', Vol. 4, Division of Soils, CSIRO, 1982, p. 27) and the digests were analyzed by using a manifold incorporating the distillation unit already described (see preceding abstract). The salicylate - nitroprusside - dichloroisocyanurate reaction system (cf. Pym and Milham, Anal. Chem., 1976, 48, 1413) was used under optimized conditions of reagent concentration. and pH. For soils containing ~0.5 to 5.4 g kg-1 of N, the coefficient of variation ranged from 0.8 to 10.5%. A procedure for the automated determination of soil and plant N from Kjeldahl digests was proposed. The continuous-flow system involved the use of a unique micro-distillation unit followed by colorimetric detection of the pure NH4Cl distillate. Optimization of the indophenol reaction is shown together with a standard manual procedure for comparison. Interference-free determinations may be carried out at a min. of 30 samples h-1 and the system has proved to be most reliable for routine analysis.
Nitrogen, total Environmental Plant Sample preparation Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Propoxur With P-aminophenol"
Anal. Chim. Acta 1992 Volume 266, Issue 1 Pages 119-126
Karim D. Khalaf, J. Sancen&oacute;n and M. de la Guardia

Abstract: The sample solution was injected into a stream (2.2 mL min-1) of water, which was merged with 0.33 M NaOH (2.2 mL min-1) and mixed in a 2-m coil. The resulting stream, containing the hydrolysis product of propoxur (2-isopropoxyphenol, as the Na salt), was mixed (in a 7-m coil) with a stream containing the quinonimine produced by oxidation via mixing of 9 mM 4-aminophenol and 0.02 M KIO4 (each flowing at 2.2 mL min-1) in a 1-m coil. The optimum reaction temperature was 25°C, and the absorbance of the indo dye produced was measured at 600 nm. The calibration graph was rectilinear for up to 16 µg mL-1 of propoxur, and the detection limit was 0.1 µg mL-1. The coefficient of variation (n = 5) was 0.1% for 38 µM. Recoveries ranged from 94.0 to 98.3%. The method was applied to natural and tap-water. The spectrophotometric determination of propoxur [2-(1-methylethoxy)phenyl Me carbamate] was carried out with p-aminophenol (PAP) in a flow system. The method involves the online hydrolysis with NaOH of propoxur to 2-isopropoxyphenol and the oxidation of PAP to its reactive quinoneimine with KIO4 and the reaction between the phenolate and the quinoneimine. A 4-channel flow manifold was employed to carry out all the different steps of the reaction considered, monitoring the indo dye formed at 600 nm. The developed procedure provides a typical calibration line of A = -0.0007 + 1.8 x 103C (A = absorbance; C = concentration. in M) with a regression coefficient of 0.9998 and a limit of detection, for a probability level of 95% (for K = 3) of 0.1 µg mL-1. In the anal. of synthetic samples containing propoxur and 2-isopropoxyphenol, the total concentration. of propoxur was determined with a recovery from 94% to 98.3%. The method provides results comparable to those obtained by the batch anal. of natural water samples spiked with propoxur.
Propoxur Environmental Water Spectrophotometry

"Micro-distillation Unit For Use In Continuous-flow Analysers. Its Construction And Use In Determination Of Ammonia And Nitrate In Soils"
Anal. Chim. Acta 1992 Volume 266, Issue 1 Pages 107-112
S. McLeod*

Abstract: The unit described and illustrated is constructed from stainless steel and fits into an Al heating block; two such stills have been incorporated into parallel continuous-flow systems for the determination of NO3- plus NH4+ and of NH4+ alone in 2 M KCl extracts of soil by the indophenol reaction. In the former system, the extract is mixed with Ti2(SO4)3 as reductant before the distillation. Optimized conditions for the analyzes were established. The coefficient of variation for standards run for every 30 samples were 5%. The calibration graph for NH4+-N was rectilinear up to 10 mg l-1.
Ammonia Nitrate Environmental Sample preparation Spectrophotometry

"Dehydrogenase Activity Monitoring By Flow Injection Analysis Combined With Luminescence-based Fibre-optic Sensors"
Anal. Chim. Acta 1992 Volume 266, Issue 2 Pages 331-338
Sabine M. Gautier, Lo&iuml;c J. Blum and Pierre R. Coulet*

Abstract: Lactate dehydrogenase in a carrier stream of 33 mM diethanolamine buffer (pH 8.6), was mixed with, e.g., 1 mM NAD+ and 210 mM L-lactate in the same buffer and 0.25 M phosphate buffer (pH 6.9) containing 10 mM dithiothreitol, 0.15 mM luciferase and 0.001% decan-1-al in a flow injection manifold (diagram given). Luminescence was transmitted from the flow cell to the luminometer via an optical-fiber bundle. The calibration graphs under various reagent conditions were rectilinear up to 250 IU L-1 of lactate dehydrogenase with a detection limit of 5 iu l-1. Dehydrogenase activities can be measured using a bioluminescence-based fiber-optic sensor associated with flow injection analysis. The sensing element of the fiber-optic sensor consists of bacterial bioluminescent enzymes covalently bound on a preactivated polyamide membrane. Optimum conditions for the dehydrogenase-catalyzed reaction compatible with the activity and stability of the bioluminescent system were selected with lactate dehydrogenase as an enzyme model permitting the detection of 5 IU L-1. The operational stability of the bioluminescent enzymes was not impaired by repeated contact with the substrates and the products of the dehydrogenase reaction.
Enzyme, lactate dehydrogenase Bioluminescence Sensor

"Mathematical Modeling Of A Flow Injection System With A Membrane Separation Module"
Anal. Chim. Acta 1992 Volume 268, Issue 1 Pages 7-27
Spas D. Kolev*, and Willem E. van der Linden

Abstract: The mathematical model developed takes into account the geometrical dimensions and dispersion properties of the main section of the manifold, the mass transfer in the chambers of the separation module and the thickness and diffusion coefficient of the membrane. The model was solved analytically by the Laplace transform technique, in which the equations reduce to ordinary linear differential equations of the second order (details given). Details are given of the experimental flow scheme, which incorporates a dialysis module, and the stimulus - response technique (Levenspiel and Bischoff, Adv. Chem. Eng., 1963, 4, 95) was used to identify the unknown parameters in the model under flow injection conditions. Three experimental series were run: one with a PTFE dialysis membrane impermeable to the KCl tracer; a second series with a Cuprophan membrane which was permeable to KCl; and the third series with water as carrier solution in the acceptor line and 1.6 mM KCl in the donor line. The response curves at the inlet and outlet of each channel were monitored at different flow rates. Applications include the optimization of sensitivity and sample throughput, and characterization and improvement of the membranes. A math. model for a flow injection system with a membrane separation module based on the axially dispersed plug flow model was developed. It takes into account the geometrical dimensions and dispersion properties of the main sections of the manifold, the mass transfer in the channels of the separation module, and the characteristics of the membrane (thickness and diffusion coefficient within it). The model was solved anal. in the Laplace domain. The inverse transformation was found to give satisfactory results for reactor Peclet nos. less than 120. Otherwise a numerical solution based on the implicit alternating-direction finite difference method was preferred. The adequacy of the model was confirmed experimental on a flow injection manifold with a parallel-plate dialysis module. The unknown flow and membrane parameters were determined by curve fitting. The membrane parameters were determined also by steady-state measurements. Fairly good agreement between the dynamic and steady-state results and with results given in the literature was observed, which, together with other experimental results, supported the validity of the model and showed that it can be used successfully for the math. description and optimization of flow injection systems with membrane separation modules. In this connection, the influence of the reactor parameters and the sample volume on the performance of such a system were investigated and conclusions for improving its sensitivity and sample throughput were drawn. Other possible applications of the model are in membrane technol. for characterizing of various membranes and in process engineering for investigating the mass transfer in different dialyzers.

"Effects Of PH, Temperature And Reaction Products On Performance Of An Immobilized Creatininase - Creatinase - Sarcosine Oxidase Enzyme System For Creatinine Determination"
Anal. Chim. Acta 1992 Volume 268, Issue 2 Pages 331-345
Henning Sakslund and Ole Hammerich*

Abstract: The three cited enzymes (I, II and III, respectively) were immobilized on controlled pore glass CPG-10 (average pore size 70 nm, particle size 75 to 125 µm) by a modification of the method of Weetall (Methods in Enzymology, 1976, 44, 140). Two flow injection systems (illustrated) were used; one had the enzymes separately immobilized in series, the other comprised co-immobilized I, II and III, and II and III in parallel flow paths. After passing the sample through either system, the H2O2 resulting from the coupled reactions was detected amperometrically in an electrochemical cell of wall-jet type equipped with a Pt working electrode, a Pt wire auxiliary electrode and a SCE as reference. The working potential was +650 mV vs. the SCE and the optimal temperature was 25°C at pH 7.7. Glycine increased the activity of I and decreased that of III but had no effect on II. Formaldehyde and urea had no effect on the enzymes. Calibration data for creatinine for 400 µM, with and without the presence of creatine (5 µM), are tabulated. The unused immobilized enzymes maintained their activity for at least 6 months, but with heavy daily use the activities of I and III, but not of II, decreased by ~25% after 20 to 30 days.
Creatine Creatinine Sarcosine Amperometry Electrode Electrode

"Comparison Of Three Propulsion Systems For Application In Flow Injection Zone Penetration Dilution And Sorbent Extraction Preconcentration For Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 269, Issue 1 Pages 9-19
Zhao-Lun Fang, Michael Sperling and Bernhard Welz*

Abstract: The zone penetration technique (Zagatto, Ibid., 1985, 173, 289) was evaluated using a peristaltic pump, a reciprocating piston pump and a sinusoidal syringe pump as propulsion systems in conjunction with an online sorbent extraction system. The efficiency of the dilution and the performance of pre-concentration with flame AAS detection were examined. Performance of the peristaltic pump was equal or better than that of the others which only showed superiority in improved long-term stability. Better precision can be achieved in flow injection online dilution for flame atomic absorption spectrometry by zone penetration using knotted reactor sample loops and transport conduits than with straight conduits. About a 2% relative standard deviation (RSD) was obtained for a dilution factor of 20 using the valley between 2 peaks with a peristaltic and a reciprocating piston pump. A sinusoidal syringe pump gave an inferior precision of 8% RSD under the same conditions owing to a lack of proper interfacing between such pumps and the atomic absorption spectrometer. Online sorbent extraction column pre-concentration. is feasible using sinusoidal and reciprocating pump systems, which obviated the need for solvent-proof pump tubes. However, both systems had to be supplemented by peristaltic pumps. Air segmentation between sample and eluent is effective in preventing dispersion at the interface when sample loading and elution were performed in 1 piston stroke of the sinusoidal pump. The concentration. efficiency (15-18 min-1) and short-term precision (~2% RSD) of both pre-concentration. systems were generally comparable to those of previously reported systems for sorbent extraction pre-concentration. with time-based sampling, but the long-term precision of the piston and syringe pump systems (4-5% RSD) was better than that of the time-based peristaltic pump system (10-20% RSD).
Spectrophotometry Sample preparation

"Spectrophotometric Determination Of Cardiac Glycosides By Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 269, Issue 2 Pages 199-203
P. Solich*, V. Sedliakov&aacute; and R. Karl&iacute;ek

Abstract: An optimized flow injection analysis method was described for the determination of lanatoside A, B and C, digoxin, digitoxin, acetyldigitoxin and ouabain, based on their reaction with picric acid in alkaline media and spectrophotometric detection at 486 nm. The flow injection manifold (diagram given) consisted of a FIA 20 Analyser linked to a Zeiss Spekol 10 photometer; the flow rate was 0.6 mL min-1 through the PTFE reaction coil (200 cm) with a sample volume of 100 µL. The calibration graph was rectilinear for 0.025 to 0.5 g L-1 for the cited glycosides (except ouabain) and from 0.01 to 0.2 g L-1 for ouabain; coefficient of variation (n = 6) were 0.6 to 2.2%. Sample throughput was 60 h-1. An optimized flow injection method for the determination of various cardiac glycosides (lanatoside A, B and C, digoxin, digitoxin, acetyldigitoxin, and ouabain) was based on their reaction with picric acid in alkaline media with spectrophotometric detection at 486 nm. The calibration graph was linear for 0.025-0.5 g L-1 cardiac glycosides (except ouabain) and 0.01-0.2 g L-1 ouabain, with relative standard deviation between 0.62 and 2.16% and a sample throughput of 60 h-1. This method was utilized for the determination of digoxin in tablets and lanatoside C, and ouabain in injections.
Glycosides Lanatoside A Lanatoside B Lanatoside C Digitoxin Acetyldigitoxin Digoxin Ouabain Pharmaceutical Pharmaceutical Spectrophotometry

"Segmental Flow Injection With Ion-selective Electrodes For The Determination Of Fluoride In Water"
Anal. Chim. Acta 1993 Volume 274, Issue 1 Pages 125-128
J. A. Borzitsky and A. V. Dvinin, O. M. Petrukhin* and Yu. I. Urusov

Abstract: The design and operation of a flow analyzer. with enhanced sampling frequency, which combined the features of flow injection and continuous-flow analysis, is described. Parameters were optimized to ensure the highest rate of analysis allowed by the bubble-through flow cell, which was equipped with fluoride-selective electrodes. Fluoride was determined in drinking water samples (0.1 ml) with a sampling frequency as high as 720 h-1 and a relative standard deviation of 1%; calibration graphs were rectilinear in the range 20 to 80 µM-fluoride.
Fluoride Water Electrode

"Approaches To The Development Of Spectrophotometric Reaction-rate Methods By Use Of Immobilized Enzymes In Continuous-flow Systems"
Anal. Chim. Acta 1993 Volume 274, Issue 1 Pages 99-107
J. M. Fern&aacute;ndez-Romero, M. D. Luque de Castro* and M. Valc&aacute;rcel

Abstract: Three methods are described for spectrophotometric reaction rate determination. The first was based on an optical biosensor, which integrated reaction and detection in the flow cell; the second was based on the reversal of flow direction and passing of the sample plug iteratively through the enzyme reactor and the detector; and the third was based on a cyclic system that allowed the sample plug to be trapped in a circuit, which contained the enzyme reactor and detector. Optimization of variables specific to each method is discussed. The reaction rate of the hydrolysis of glucuronides catalyzed by β-D-glucuronidase was studied, and a critical comparison of the three techniques was made. Based on reaction-rate measurements, a parameter was defined to compare the features of the methods; no significant differences were found for the biochemical system studied.
Enzyme, β-glucuronidase Spectrophotometry Sensor

"Entrapped Copper(II) Carbonate For Indirect Determination Of Glycine By Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1993 Volume 274, Issue 2 Pages 275-281
J. V. Garcia Mateo, J. Mart&iacute;nez Calatayud*

Abstract: The immobilization of CuCO3 in AL-100-A polyester resin during polymerization is described. The resulting solid resin, with an optimum reagent concentration. of 1 g mL-1 and particle size 150 to 200 µm was packed into a column (13.5 cm x 0.8 mm) for use as a reactor in the cited determination of glycine; the analyte complexed with and dissolved immobilized Cu(II) which was then determined by AAS at 324.8 nm. Flow injection analysis and chemical parameters were optimized: the injection volume was 345 µL, and the Na2B4O7 - HCl - NaOH carrier buffer concentration. was 5 mM with a pH of 9.25 and a flow rate of 4.2 mL min-1. The calibration graph was rectilinear from 1.2 (detection limit) to 35 µg mL-1, the coefficient of variation (n = 20) was 1.1% at 20 µg mL-1 and the sample throughput was 180 h-1. Tolerance limits for potential interferents are given. The method was applied to glycine determination in tablets (Okal) and drinking phials (Actilevol). Results agreed with certified values.
Glycine Pharmaceutical Spectrophotometry

"Development And Optimization Of A Liquid Chromatographic Method For The Determination Of Gentamicin In Calf Tissues"
Anal. Chim. Acta 1993 Volume 275, Issue 1-2 Pages 285-293
Florence Sar, Pierre Leroy and Alain Nicolas*, Philippe Archimbault

Abstract: Calf muscle, liver, kidney or fat (5 g) was deproteinated with 5% trichloroacetic acid (20 ml). After centrifugation at 8000 rpm and 5°C for 15 min, the supernatant solution was adjusted to pH 7.0 ± 0.2 and diluted to a known volume with 0.1 M Na2SO4 - 0.1 M K2HPO4 (pH 7). The solution (10 ml) were applied to CM-Sephadex C-25 cartridges (prep. described) in 1 mL fractions, the cartridges were washed with 0.2 M Na2SO4 - 1 mM EDTA (2 x 1 ml), water (1 ml) and 0.05 M NaOH (250 µL). Gentamicin (I) was eluted with 0.05 M NaOH (1 ml) and the eluates were mixed with 1 M HCl (100 µL), 0.5 M camphorsulfonate (pH 2.2; 100 µL). I was determined by HPLC on a column (12.5 cm x 4 mm) of LiChrospher 100 RP-18 (5 µm) operated at 45°C and protected by a guard column (0.4 cm x 4 mm) of the same material. The mobile phase (1.2 mL min-1) was 0.05 M Na dl-camphor-10-sulfonate solution in 0.1 mM EDTA (pH 2.2) - methanol (9:11). Post-column derivatization was carried out at 45°C in a PTFE knitted open-tubular reactor (3 m x 0.5 mm i.d.) with phthalaldehyde solution containing mercaptoethanol (0.5 mL min-1). Fluorimetric detection was at 440 nm (excitation at 340 nm). Detection limits were 25 ng g-1 of I in muscle and fat and 50 ng g-1 of I in kidney and liver. Recoveries were 68 to 98%.
Gentamicin Liver Kidney Cow Fat Muscle HPLC Fluorescence

"Robust Estimation Of Selectivity Coefficients Using Multivariate Calibration Of Ion-selective Electrode Arrays"
Anal. Chim. Acta 1993 Volume 276, Issue 1 Pages 75-86
Dermot Diamond* and Robert J. Forster

Abstract: Selectivity coefficients for Na, Ca, and K ISE estimated by traditional methods, e.g., separate and mixed solution methods, are compared with values obtained by an approach using multivariate calibration using simplex optimization and non-linear modeling of the array characteristics. The method was used to predict the concentration. of Sa, Ca and K in blood plasma and mineral water samples using dip and FIA measurements. For the array FIA data, the possibility of using an enhanced kinetic-based selectivity for analytical measurements is raised. Further improvement in the three-electrode array performance by using a fourth multiple ionophore electrode is discussed. Results obtained are compared with single electrode dip and FIA measurements of Na in plasma samples.
Sodium Calcium Potassium Blood Plasma Mineral Electrode

"Comparison Between Different Inorganic Supports For The Immobilization Of Amyloglucosidase And α-amylase To Be Used In Enzyme Reactors In Flow Injection Systems. 2. Hydrolysis Of Glycogen"
Anal. Chim. Acta 1993 Volume 276, Issue 2 Pages 319-328
Jenny Emn&eacute;us* and Lo Gorton

Abstract: As a continuation of the work described in Part I, the immobilization procedure for glucan 1,4-α-glucosidase was carried out with four different inorganic supports, and heat-stable α-amylase (Termamyl) was also immobilized on three supports. The highest immobilization efficiency and optimum activity (for the entry of glycogen) were obtained with controlled-pore glass (CPG) supports of pore size 170 and 729 Å, respectively, and for Termamyl with Micropil A and a CPG support of 1489 Å, respectively.
Glycogen

"Comparison Between Different Inorganic Supports For The Immobilization Of Amyloglucosidase And α-amylase To Be Used In Enzyme Reactors In Flow Injection Systems. 1. Hydrolysis Of Maltose, Malto-oligosaccharides And Soluble Starch"
Anal. Chim. Acta 1993 Volume 276, Issue 2 Pages 303-318
Jenny Emn&eacute;us* and Lo Gorton

Abstract: Glucan 1,4-α-glucosidase was immobilized on 12 different inorganic supports by silanization with aminopropyltriethoxysilane (I) followed by glutaraldehyde activation; also, two of the alumina-based supports were treated with PEI before glutaraldehyde activation. The various packings were then packed in identical reactors (1 cm x 2 mm; 30 µL) and compared in respect of optimum pore size, surface area, immobilization efficiency and enzyme activity for the cited substrates. The highest immobilization efficiency was obtained with a controlled-pore glass with a pore size of 170 .angstrom., and the highest enzyme activity with Micropil A (pore size 300 .angstrom.; surface area 100 to 150 m2 g-1). Treatment of the alumina supports with I gave better results than did treatment with PEI.
Maltooligosaccharides Maltose Starch

"Catalytic Behaviour Of Iron(II)-oxime Complexes In The Chemiluminescence Reaction Of Luminol With Hydrogen Peroxide"
Anal. Chim. Acta 1993 Volume 277, Issue 1 Pages 67-72
Yun-Xiang Ci*, Jian-Ke Tie, Feng-Ji Yao, Zhao-Lan Liu, Sa Lin and Wei-Qing Zheng

Abstract: Chemiluminescence produced by the catalytic effect of iron(II)-oxime complexes on the oxidation of luminol by hydrogen peroxide was studied. This is a very fast chemiluminescence reaction and the emission spectrum is similar to that of peroxidase-catalyzed chemiluminescence. Different kinds of iron(II)-oxime complexes were compared and it was fund that the symmetrical dioxime complex (four nitrogen ligands) has a higher catalytic activity than the asymmetric monooxime complex (two nitrogen and two oxygen ligands). The presence of EDTA can greatly accelerate the chemiluminescence reaction, which was considered to be a result of the formation of a mixed-ligand complex. Other homologues of EDTA were tested and showed different degrees of enhancement. Optimum conditions for the chemiluminescence reactions were examined. Combined with a flow injection technique, trace amounts of hydrogen peroxide (2 times 10^-7-1 times 10^-4 M) and, using glucose oxidase, glucose (0.79-160 µg mL-1) can be determined by using the iron(II)-dimethylglyoxime complex as a typical catalyst. The detection limit of hydrogen peroxide was 1.3 times 10^-8 M. The relative standard deviation was 1% for the determination of 2 times 10^-7 M H-2O-2 (n=11). The feasibility of utilizing the proposed method for the determination of glucose in human serum was examined.
Glucose Serum Human Chemiluminescence

"Development Of A Flow-through Electrochemical Detector For Glucose Based On A Glucose Oxidase-modified Micro-electrode Incorporating Redox And Conducting Polymer Materials"
Anal. Chim. Acta 1993 Volume 278, Issue 1 Pages 5-16
Ellen Rohde, Eithne Dempsey, Malcolm R. Smyth* and Johannes G. Vos, Hendrik Emons

Abstract: An amperometric sensor based on glucose oxidase for applications in flow injection analysis was developed. The working electrode was prepared by codepositing glucose oxidase with the redox polymer [Os(bipridyl)2(poly-4-vinylpyridine)10Cl]Cl and glutaraldehyde onto the surface of a Pt wire. The deposit was covered with an electropolymerized layer of pyrrole also containing glucose oxidase, the working electrode was mounted in one arm of the 'T'-shaped flow cell, the Ag/Ag3PO4 reference electrode was mounted in the second arm and the stainless steel tube that formed the third arm acted as the counter electrode (diagram given). Calibration graphs were rectilinear for 1-50 mM glucose with a detection limit of 1 mM. The optimum values for pH and flow rate were 6-8 and 0.7 ml/min, respectively. The sensor is highly sensitive to ascorbic acid, uric acid and acetominophen.
Glucose Electrode Electrode Amperometry

"Development And Characterization Of An Automated Flow System For Voltammetric Analysis"
Anal. Chim. Acta 1993 Volume 281, Issue 1 Pages 25-33
Louise A. Mahoney, John O'Dea and Janet G. Osteryoung

Abstract: A flow system for voltammetric analysis is described and characterized. This system was designed so that sample manipulation and electrochemical experiments could be performed under automated control. The goal of this work is to expand the practical possibilities for elucidation of the electrochemical behavior of chemical systems. An auxiliary goal is to exploit the potential of flow systems combined with pulse voltammetry for chemical analysis. Once a system has been characterized systematically to establish optimal conditions, voltammograms may be subjected to kinetic analysis. The test system employed here is the reduction and anodic stripping of Pb(II). The accuracy of the sample delivery system was tested by producing calibration curves, which were linear over the range of 0-100% mixing, with correlation coefficients greater than 0.999. The introduction of the sample by means of a sample injector was evaluated along with the effect of the carrier flow-rate on anodic stripping voltammograms. The optimum conditions of 1 mL min-1 carrier flow-rate and 150% carrier sweep volume of the loop were determined. Although the flow cell detector is of the wall jet style, the effect of flow-rate on anodic stripping currents is not that of wall jet behavior. The reproducibility of the flow system, for optimum conditions, matched that of the detector for static cell experiments. Finally, the conversion efficiency of the detector was determined to be approximately 1%. [References: 22]
Lead(2+) Voltammetry Coulometry

"Flow Injection Determination Of Water In Organic Solvents By Near-infrared Spectrometry"
Anal. Chim. Acta 1993 Volume 281, Issue 2 Pages 259-264
Salvador Garrigues, M&aacute;ximo Gallignani and Miguel de la Guardia

Abstract: Dichloromethane (I) and isobutylmethylketone (II) were used as test systems for the determination of water in organic solvents by flow injection (FI) near-IR spectrometry. A systematic study was carried out of the effect of flow variables (i.e., carrier flow and sample injection volume) on the sensitivity and speed of the determination. From the results obtained optimum conditions were established for the analysis, based on the monitoring of the O-H stretch absorbance band of water in the near-IR region. For I and II, detection limits of water were 0.01 and 0.005%, respectively, and corresponding calibration graphs were linear up to 0.2 and 0.5%. The results obtained compared well with those obtained by FI-spectrophotometry, only the lead tetra-acetate method gives a better sensitivity and detection limit.
Water Organic compound Organic compound Spectrophotometry

"Flow System Based On Sequential Delivery Of Air-sandwiched Solutions Into A Micro-cell For Spectrophotometric Catalytic Analysis"
Anal. Chim. Acta 1993 Volume 282, Issue 2 Pages 389-395
Susumo Kawakubo, Masaaki Iwatsuki and Tsutomu Fukasawa

Abstract: In the cited system air-sandwiched sample solution, reagent solution and water (total volume 317 µL) were delivered sequentially by a stream (13 ml/min) of air through 1 mm i.d. PTFE tubing into an acrylic resin spectrophotometric cell (diagrams given) in which the solution were mixed and the ensuing reaction was monitored by measuring the absorbance as a function of time. The system was used to determine sulfide by monitoring its effect on the decolorization of methyl orange (C.I. Acid Orange 45) by bromate (Tamarchenko, Zh. Anal. Khim., 1978, 33, 824). The absolute sensitivity (slope of the calibration graph for determining the wt. of sulfide) was ten and threefold higher, respectively, than those of a manual batch and a stopped-flow flow injection technique (detection limits 18, 51 and 220 ng of sulfide, respectively). The method was free from dispersion and air carrier flow rate variation effects.
Sulfide Spectrophotometry

"Chemiluminescence Investigation Of The Interaction Of Metalloporphyrins With Nucleic Acids"
Anal. Chim. Acta 1993 Volume 282, Issue 2 Pages 695-701
Yun-Xiang Ci, Yuan-Gang Zheng, Jian-Ke Tie and Wen-Bao Chang

Abstract: The cited interactions were studied by examining the catalytic activity of metallated m-tetrakis-(4-N-methylpyridinyl)porphyrins on the luminol-H2O2 chemiluminescence reaction. The presence of DNA significantly enhanced the reaction and this phenomenon was used as a means of determining DNA. A previously described flow injection chemiluminescence manifold (cf. Ibid., 1992, 269, 109) was used for the determination aqueous calf thymus DNA. Optimum conditions were established for manganese tetrakis(4-aminophenyl) porphyrin (I) as catalyst. The calibration graph was linear from 20-200 ng/ml of DNA with a fixed concentration of 20 nM-I, the RSD (n = 1) was 2.6% at 10 ng/ml, and the detection limit was 0.20 ng/ml. Results are discussed.
DNA Chemiluminescence

"Determination Of Total And Free Sulfur Dioxide In Wine With A Continuous-flow Micro-distillation System"
Anal. Chim. Acta 1993 Volume 283, Issue 1 Pages 401-407
A. Maquieira*, F. Casamayor and R. Puchades, S. Sagrado

Abstract: For free SO2, flowing sample was merged with a pre-mixed stream of H2O/1.2 M H3PO4 (1:1) in the described and illustrated apparatus and a portion was transferred to a distillation unit comprising a coiled column in a glycerol bath at 100°C. The liberated SO2 was swept by N2 to an absorption module, entrained in a stream of 2,2'-dinitro-5,5'-dithiodibenzoic acid (0.32 g/l) in phosphate buffer solution of pH 6 and the resulting solution passed via a reaction coil to a detector operated at 410 nm. The procedure for total SO2 was similar but the sample was first merged with 4 M NaOH and then with 1.2 M H3PO4 before reaching the injection valve. Calibration was effected with standard sodium sulfite solution (0-30 or 0-200 µg/ml for free or total SO2, respectively); response over these ranges was linear. The optimization of the experimental parameters is described. Acetaldehyde interfered but ascorbic acid did not. The detection limit was 5 or 1 µg/ml for total or free SO2, respectively, and the RSD in the middle of the calibration range was 2.9 or 10.4%, respectively (n = 10). Results for red and white wines agreed with obtained by standard distillation and iodimetric methods.
Sulfur dioxide Wine

"Spectrophotometric Determination Of Magnesium In Serum By Using A Flow Injection System With An Immobilized Enzyme Reactor"
Anal. Chim. Acta 1993 Volume 283, Issue 1 Pages 447-452
J. M. Fern&aacute;ndez-Romero, M. D. Luque de Castro and M. Valc&aacute;rcel*, R. Quiles-Zafra

Abstract: The method was based on the activating effect of Mg(II) on the hydrolysis of 2-nitrophenyl β-D-galactopyranoside (I) by β-galactosidase with all other reactants present in excess. In a merging-zones configuration (illustrated), portions of the sample and a solution of 4.7 g/l of NaCl and 60.3 mg/l of I in reagent A (aqueous 0.1 M Tris/4 mM dithiothreitol/0.4 mM EGTA of pH 7.5) were simultaneously injected into a stream of reagent A. In a region maintained at 37°C, the solution were mixed in a single-bead string reactor and passed through a reactor containing β-galactosidase immobilized on controlled-pore glass. A flow of 1 M NaOH was introduced and merged with the stream in a reactor coil, and the absorbance was monitored at 405 nm. Optimized operating parameters were established. Forty samples could be analyzed in 1 h, and response was linear for 5-20 µM-Mg. Within-run and between-run RSD (n = 11) were 0.78-2.91% and 1.7-3.21%, respectively. The method showed good selectivity, with no interference from a 20-fold amount of calcium. Recovery of added Mg was 96-113% and results were well correlated with those of AAS.
Magnesium Blood Serum Spectrophotometry

"Ion-chromatographic Separation And Online Cold Vapor Atomic Absorption-spectrometric Determination Of Methylmercury, Ethylmercury And Inorganic Mercury"
Anal. Chim. Acta 1994 Volume 284, Issue 3 Pages 661-667
Corrado Sarzanini*, Giovanni Sacchero, Maurizio Aceto, Ornella Abollino and Edoardo Mentasti

Abstract: The ion chromatographic separation of methylmercury, ethylmercury and inorganic mercury as cysteine complexes was investigated. The chromatographic apparatus was interfaced with cold vapor atomic absorption spectrometry for detection using an on-line continuous flow cell coupled with a reduction system (sodium tetrahydroborate). The influence of the composition of the eluent (pH, ionic strength, cysteine concentration) and stripping gas flow-rate was investigated. The method was optimized by coupling an on-line pre-concentration step. The detection limits, evaluated on 100.0 mL samples, were 2, 10 and 4 ng for Hg, CH3Hg and C2H5Hg, respectively. The method was applied to synthetic mixtures and natural samples (tap water) and furnished satisfactory results.
Mercury(II) Methylmercury ion Ethylmercury Water HPIC Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Tetracycline Antibiotics"
Anal. Chim. Acta 1994 Volume 285, Issue 1 Pages 9-12
R. Karlicek and P. Solich

Abstract: Tablets were dissolved in water, sedimented and filtered. Portions of the filtrate were injected into a water carrier stream (0.67 ml/min) which mixed with a reagent comprising aqueous 4-aminophenazone, di-sodium EDTA buffer of pH 10 and 1% Brij 35 at 0.54 ml/min in a coil prior to reaction with potassium hexacyanoferrate(III) (0.54 ml/min) in a second coil at ambient temperature The absorbance of the dye formed was measured at 520 nm. A modified simplex method was employed to optimize several mutually affected variables and individual variables (tabulated), including the lengths of the coils used and the concentrations of reagents. Calibration graphs (peak height) were linear (r 0.995) for 1-20 and 20-250 mg/l of doxycycline, oxytetracycline, rolitetracycline and tetracycline with RSD of 1% for 10 and 100 mg/l and an output of 60-70 samples/h.
Doxycycline Oxytetracycline Rolitetracycline Tetracycline Pharmaceutical Spectrophotometry

"Ion Chromatography For Monitoring Biotechnological Processes. 2. Applications For Industrial Cultivation Media"
Anal. Chim. Acta 1994 Volume 286, Issue 2 Pages 179-187
Ute Scheller, Detlef Siedenberg, Uwe H&uuml;bner, Michael Siebold, Gerlinde Kretzmer and Karl Sch&uuml;gerl*

Abstract: The production of alkaline protease by Bacillus licheniformis, and the cultivation of Cephalosporium acremonium was monitored by the ion-chromatography of chloride, phosphate and sulfate anions in the broth. Sample proteins were filtered, and filtrates analyzed on a Hamilton PRP-X 100 ion-exchange column with a Hamilton PRX- x 100 pre-column and RI detection (no other details given). Lactic acid, acetic acid, citric acid and glucose, present during the production of lactic acid by Lactobacillus salivarius subsp. salivarius were also monitored by ion-exclusion chromatography (no details given). Glucose and lactic acid results compared favourably with those obtained by an enzyme FIA method using immobilized glucose oxidase and lactate oxidase amperometric detectors (no details given). The problems involved in sampling, sample pre-treatment, the optimization of the chromatographic analysis and the enrichment of the analytes after dialysis are discussed.
Lactic acid Acetic acid Citric acid Glucose Fermentation broth Industrial HPIC Biotechnology

"Permeation Denuder For Sampling And Continuous Analysis Of Gases. 1. System Configuration, Basic Studies And Application To Atmospheric Ammonia And Sulfur Dioxide"
Anal. Chim. Acta 1994 Volume 291, Issue 3 Pages 305-320
Wolfgang Frenzel*

Abstract: Recent developments of the coupling of permeation denuders with FIA are described. The principles of the method are outlined. The experimental variables that affect collection of gaseous compounds are considered and the behavior of tubular and planar denuders compared. Collection efficiency of the permeation denuders was assessed in terms of gas flow rate, type of membrane, and composition of absorber solution using NH3 and SO2 as test gases. The calibration methods are outlined.
Ammonia Sulfur dioxide Environmental

"Optimization Of The Amperometric Detection Of Nitrite By Reaction With Iodide In A Post-column Reactor For Liquid Chromatography Of Non-volatile Nitrosamines"
Anal. Chim. Acta 1994 Volume 294, Issue 3 Pages 251-260
G. A. Sacchetto*, G. Favaro, P. Pastore and M. Fiorani

Abstract: The use of iodide in acidic medium as a reagent for the liquid chromatographic amperometric determination of non-volatile nitrosamines was investigated in a two-line flow injection manifold. The method was based on the decomposition of nitrosamines in warm acidic solution to yield nitrite and the electrochemical detection of the oxidation of nitrite with iodide. The FIA system allowed 20 µL of nitrite solution to be injected into a carrier stream (0.5 ml/min, water or water/acetonitrile, 1:3) which was then merged with a KI stream in 0.5 M H2SO4 (0.5 ml/min). The merged solution was passed through a heated reactor coil, a cooling coil and the flow-through detector cell containing Au electrodes at a potential of 0.2-0.3 V vs. SCE. A linear response was obtained for 0.5-5 mM nitrite with a reaction temperature of 50-60°C and an iodide concentration of 2 mM. The detection limit for nitrite was 10 pg in a 20 µL sample (0.1 µM). Compared with the use of Ce(IV) reagent, the proposed method achieved a higher sensitivity, a lower detection limit and comparable band broadening and tailing.
Nitrite Amperometry LC

"Application Of Enzyme Field-effect Transistor Sensor Arrays As Detectors In A Flow Injection System For Simultaneous Monitoring Of Medium Components. 1. Preparation And Calibration"
Anal. Chim. Acta 1994 Volume 296, Issue 3 Pages 263-269
T. Kullick, M. Beyer, J. Henning, T. Lerch, R. Quack, A. Zeitz, B. Hitzmann, T. Scheper and K. Sch&uuml;gerl*

Abstract: Enzymes were co-immobilized on the pH-sensitive gates of an 8-channel array of field-effect transistors (FETs). Glucose was determined with a glucose dehydrogenase (GDH) FET, maltose with a co-immobilized maltase (MAL)/GDH FET, sucrose with a co-immobilized invertase (INV)/GDH FET, lactose with a β-galactosidase/galactose dehydrogenase (β-GAL/GALDH)-fusion protein FET and ethanol with a co-immobilized alcohol dehydrogenase/aldehyde dehydrogenase (ADH/ALDH) FET. These EnFETs were integrated into FIA systems, and were calibrated and characterized with respect to pH, buffer capacity, stirrer speed, NAD concentration and cross sensitivity. Because the signals of the EnFETs were sensitive to pH and buffer capacity, the pH was monitored with a pH-FET in the array, and the buffer capacity and substrate concentration were calculated from the shape of the signal of the FIA system. The EnFETs were stored at 4°C for many months without activity loss. They have satisfactory activity for performing a large number of analyzes. However, glucose reversibly inhibited the sucrose signal and added to the maltose signal. Hence the sucrose monitor can only be used when glucose is practically absent, and the maltose sensor requires simultaneous determination of glucose.
Lactose Ethanol Sucrose Glucose Maltose Fermentation broth Field effect transistor Sensor

"Determination Of Phosphorus In Aqueous Solution Via Formation Of The Phosphoantimonylmolybdenum Blue Complex Re-examination Of Optimum Conditions For The Analysis Of Phosphate"
Anal. Chim. Acta 1995 Volume 302, Issue 1 Pages 69-74
L. Drummond and W. Maher*

Abstract: This paper describes an investigation of the conditions affecting the determination of phosphate using the reduced phosphoan-timonylmolybdic acid method. The aim was to develop a determination method with faster kinetics than the original procedure of Murphy and Riley, for automation using flow-injection analysis. Optimum color formation was found to occur at [H+]/[MoO2-4] ratios between 50-80 at all pH values tested (0.36-1.06). The maximum rate of formation occurs at a [[H+]/[MoO42-]] ratio of 70 within a pH range of 0.57-0.88 when an antimony concentration greater than 0.06 mM and ascorbic acid concentration greater than 0.009 M in the final solution are used. Full color development occurs within 0.8-1 min. The ascorbic acid reagent was found to be stable for 30 days. The results of the study indicated that by suitable selection of reagent conditions, rapid chromophore development can be achieved.
Phosphorus Spectrophotometry

"Automatic Continuous-flow Determination Of Sulfite In The Presence Of A High Concentration Of Thiosulfate"
Anal. Chim. Acta 1995 Volume 302, Issue 2-3 Pages 269-274
J. S. Cosano, M. D. Luque de Castro* and M. Valc&aacute;rcel

Abstract: The sample was injected into water as carrier and merged with a mixture, prepared in situ, of (a) 20 µg/ml of p-rosaniline in aqueous 1.5% ethanol buffered by acetate at pH 4 and (b) 0.1 M K2HPO4 buffer of pH 7. The mixture passed through a 318 cm coil of i.d. 0.5 mm before measurement at 540 nm in a flow-through cell. Response was linear for 1-20 µg/ml of sulfite and the RSD at 7 µg/ml was 1.54% (n = 11). Sampling frequency was 40/h and up to 1 mg/ml of sulfate or thiosulfate did not interfere. With the introduction of a 1000-fold dilution step and of a single bed string reactor just before the reagent-merging point, the method was applied to solutions from a thiosulfate production plant. Peak width measurement was necessary to optimize sensitivity. Sampling frequency was 8/h and the RSD for 0.23% of sulfite in 60% thiosulfate solutions was 1.3-2.8% (n = 11).
Sulfite Process liquor Spectrophotometry

"Determination Of Trace Aluminum In Natural Waters By Flow Injection Analysis With Fluorescent Detection Of The Lumogallion Complex"
Anal. Chim. Acta 1995 Volume 303, Issue 2-3 Pages 211-221
Susan H. Sutheimer and Stephen E. Cabaniss*

Abstract: Samples (20-100 µL) were injected into a carrier stream (1 ml/min) of 100 mM acetate buffer of pH 5.2 reacted at 55-57°C in a mixing coil with 1.8 mM lumogallion (100 µL/min). After passing through a second mixing coil at room temperature, fluorimetric detection at 595 nm (excitation at 500 nm) was achieved. Calibration graphs were linear over the range 36 nM- to 3.6 µM-Al with a detection limit of 3.7 nM-Al. At 1.1 µM-Al an RSD (n = 6) of 0.8% was obtained. The kinetics of formation the Al-lumogallion chelate is discussed. Comparative results were obtained with the treatment of 10 mL of sample with Al(III) in 2% HNO3 and using 10 µL of 1 g/l magnesium nitrate in 2% as a matrix modifier and GFAAS.
Aluminum Environmental Fluorescence

"In-flow Speciation Of Copper, Zinc, Lead And Cadmium In Fresh Waters By Square-wave Anodic-stripping Voltammetry. 2. Optimization Of Measurement Step"
Anal. Chim. Acta 1995 Volume 305, Issue 1-3 Pages 183-191
W. Martinotti, G. Queirazza, A. Guarinoni and G. Mori*

Abstract: Square-wave anodic-stripping voltammetry measurements were performed in a wall-jet type flow cell with a glassy carbon working electrode (5 mm diameter), a Ag/AgCl/3 M KCl reference electrode and a Pt counter electrode. The five other units of the system (potentiostat, thermometer, current measurement block, ultrasound generator and pump/valve driver) were controlled by a micro-processor. A measurement cycle consisted of three rinse steps, a Hg-film renewal step and two identical measurement steps. Each measurement step had six separate phases, (i) heavy metal deposition at -1100 mV, (ii) first rest period with pump off, (iii) stripping current measurement with square wave potential ramp from -1100 to +100 mV at 2000 mV/s with square wave period of 5 ms, step height of 10 mV and square wave amplitude of 25 mV, (iv) cleaning of the Hg film by oxidizing the heavy metals at a constant potential and with the pump on, (v) rest period with pump off and (vi) background current measurement as in (iii). The flow rate through the detector cell was 0.9 ml/min and measurements were made with a supporting electrolyte of 0.2 M HNO3. A fresh Hg film was deposited on the working electrode before each measurement cycle by electrolysing a mercury nitrate solution. Calibration graphs were linear for up to 100 µg/l of Zn, 5 µg/l of Cd and 15 µg/l of Pb and Cd in water. The complete measurement cycle took ~e;30 min.
Cadmium Copper Lead Zinc Environmental Voltammetry Electrode Electrode

"Characterization And Reduction Of Interferences In Flow Injection Analysis For The In Situ Determination Of Nitrate And Nitrite In Seawater"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 413-424
Anne Daniel, a, Dominique Birot*, Michel Lehaitre and Jacques Poncin

Abstract: An FIA method for the in situ determination of nitrate and nitrite in seawater was studied in order to improve the precision and sensitivity. The method was based on the reduction of nitrate to nitrite using a Cd column and the spectrophotometric detection of nitrite following reaction with an azo dye. The Cd reduction column could be switched in and out of the line to allow the determination of nitrite and total nitrate/nitrite concentrations. The sample stream (1.4 ml/min) was merged with a 30 g/l ammonium chloride buffer stream of pH 8.5. After passing through the reduction column, the flow was split into two equal streams of 1.2 ml/min each. These streams were merged with streams (0.6 ml/min) of 10 g/l sulfanilamide in 10% HCl or 1 g/l N-(1-naphthyl)ethylenediamine. The streams were recombined before passing through the reaction coil to the detection cell where the absorbance at 540 nm was measured against a background at 630 nm. The calibration graph was linear for up to 40 µM-nitrate and the detection limit was 0.45 µM. The RSD (n = 6) for the determination of 0.5 µM-nitrate were ~e;5%. The effects of pressure, salinity and temperature on the determination were studied.
Nitrate Nitrite Sea Spectrophotometry

"Preconcentration Of An Analyte Dialysate In A Flow Injection System"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 214-221
J. F. van Staden* and C. J. Hattingh

Abstract: An FIA system with online dialysis, pre-concentration by ion-exchange and detection by AAS was evaluated and optimized. The various functions of the system were controlled by a time regulated system from a computer. The system was used to determine Cu in vitamin and mineral food supplements for dogs and cats. A 2 g portion of the food supplement was shaken with water for 30 min and the resulting slurry was diluted to 1000 mL with ammonium acetate/ammonia buffer at pH 8.7 (buffer A). After allowing insoluble material to settle, 22 µL of the supernatant was injected into the donor stream (buffer A, 2.5 ml/min) of the FIA manifold. After passing through the dialyser unit, the acceptor stream (buffer A, 1.4 ml/min) was propelled through an Dionex OnGuard-H ion-exchange column (1.2 cm x 1.4 mm i.d.). The flow-through the ion-exchange column was reversed and the retained Cu was eluted by injecting 1 mL of eluent into the buffer stream. Cu was determined by AAS at 324.6 nm with N2O/acetylene flame. The eluent contained 1 M HCl, 1 M HNO3 and 0.1 M NaCl. The results obtained using a calibration graph covering the range 0.5-5 mg/l Cu were in agreement with manufacturers` specifications and comparable to those obtained by direct AAS measurement. The detection limit in the food supplement was 0.015% with a 2 g sample and the RSD (n =15) was 5.74%.
Copper Pharmaceutical Feed Food Spectrophotometry

"Online Coated Columns For The Spectrophotometric Determination Of Metals By Continuous-flow Analysis"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 378-385
Yuri A. Zolotov, Irina M. Maksimova, Elena I. Morosanova* and Andrei A. Velikorodny

Abstract: Online coated microcolumns and capillary tubes were evaluated for the separation and pre-concentration of metal ions by continuous-flow analysis. Xylenol orange, 1-(2'-pyridylazo)-2-naphthol and (p-sulfophenylazo)-2'-sulfo-4'-nitrodiazoaminobenzene disodium salt (Cadion) were immobilized on reversed-phase silica (C16, C8, phenyl, C1) packed into microcolumns (2.5 cm x 2 mm i.d.) or on capillary tubes (10 m x 2 mm i.d.) with hydrophobic inner surfaces (C6, C-phenol, C1). The optimum conditions for the maximum retention of reagent were determined. The adsorption and acid desorption of metal ions from coated microcolumns and capillaries were studied and procedures for the determination of Cd, Co, Cu and Fe(III) in the range 0.08-30 µM were suggested using spectrophotometric detection. Preconcentration factors of up to 9 and 19 were achieved with coated microcolumns and capillaries, respectively.
Cadmium Cobalt Copper Iron(III) Spectrophotometry

"Efficiency And Response Studies On Gas Diffusion Manifolds In Flow Injection Systems"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 206-213
Robert Tryzell and Bo Karlberg*

Abstract: The gas transfer efficiency of gas diffusion units fitted with three different types of membranes were compared for the determination of ammonia nitrogen by FIA. The three membranes studied were standard PTFE tape (thickness 0.08 mm), Millipore (0.45 µm) and Celgard 2400 (an effective pore size of 0.05 µm). The FIA manifold allowed the donor stream to be merged with an alkaline reagent. The acceptor stream was 0.1 M HCl and an indicator solution containing bromocresol purple, bromothymol blue and cresol red (4:2:1) was used. Detection was carried out at 590 nm. PTFE tape exhibited transfer efficiencies of 2-17% at a sampling frequency of 60 samples/h and 2-23% at a sampling frequency of 30 samples/h. Millipore and Celgard gave about 80 and 30% of the efficiency and response, respectively, obtained with PTFE tape. The peak height response was dependent on injection volume, groove length in the gas diffusion cell, NaOH concentration and membrane type. The peak height response could be increased by placing the manifold in a ultrasonic bath. The response may be changed by as much as 19% by variations in the installation procedure used to assemble the gas diffusion cell.
Ammonia, nitrogen Spectrophotometry

"Dynamic Analysis Of The Binding Process Of Bovine Serum Albumin On Glutaraldehyde-activated Controlled Pore Glass"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 261-268
Hiroyuki Ukeda*, Tohru Ishii, Masayoshi Sawamura and Hirozo Kusunose

Abstract: Twenty microlitre volumes of BSA solution (5 mg/ml) were repeatedly injected into a column (5 cm x 1.68 mm i.d.) packed with aminopropyl-controlled pore glass activated with glutaraldehyde (GA-CPG). The elution profile of BSA was recorded using phosphate buffer eluents (0.5 ml/min) and detection at 280 nm. The results were analyzed using a model based on the assumption that two modes are involved in binding BSA to GA-CPG. Binding process parameters such as bound amounts and binding rate constants were estimated by a curve fitting method. An increase in ionic strength of the carrier solution resulted in a reduction in the total amount of BSA bound. The maximum bound amount occurred at pH 6 with low ionic strength carriers and at pH 7 for higher ionic strength carriers. The reduction of GA-CPG with sodium borohydride reduced the bound amount while blocking treatment with amine had no effect.
Albumin Cow Serum Spectrophotometry

"Comparison Of Plumbane And Tetraethyllead For The Determination Of Lead By Inductively Coupled Plasma Atomic-emission Spectrometry"
Anal. Chim. Acta 1995 Volume 309, Issue 1-3 Pages 369-378
M. C. Vald&eacute;s-Hevia y Temprano, M. R. Fern&aacute;ndez de la Campa and A. Sanz-Medel*

Abstract: Sediments and lichen (200 mg) were microwave digested in 1.5 mL concentrated HNO3, 0.5 mL 80% HClO4 and 0.5 mL concentrated HF (details given). After cooling, the excess HF was reacted with 3.5 mL 6% H3BO3, the mixture re-digested and the contents made to 100 mL with water. Citrus leaves and lyophilized vegetables (0.5 g) were digested in 5 mL 65% HNO3 and 2 mL H2O2 and the contents made to 25 mL with water. The solutions were mixed to contain 0.3% or 0.7% K2Cr2O7 for PbH4 (I) or tetraethyllead (II) analysis and merged at 1 ml/min with carrier streams (1 ml/min) of 360 mM or 600 mM lactic acid for I and II, respectively, and 5% NaBH4 in 0.1% NaOH for I or 1% sodium tetraethylboron in 1% NaOH for II. The mixed solutions were aspirated at 2.4-3 ml/min into a detuned grid-nebulizer for ICP-AES and Pb determined at 0.7 kW and 20.353 nm. Calibration graphs were linear up to 0.5 mg/ml of I and 1.5 mg/ml of Pb for II with detection limits of 2 ng/ml and 1 ng/ml of Pb, respectively. At 50 ng/ml of Pb the RSD (n = 10) were 1.3% for I and 1.2% for II. The selectivity of the two methods in the presence of chloride, nitrate and a range of cations was confirmed. The analysis of Pb via II was preferred as only Ni and Sb interfered.
Lead Plant Environmental Leaves Vegetable Sample preparation Spectrophotometry

"A Stopped-flow/continuous-flow Method For Kinetic Determinations"
Anal. Chim. Acta 1995 Volume 309, Issue 1-3 Pages 277-282
Yun-Sheng Hsieh and S. R. Crouch*

Abstract: Using the kinetics of glucose (I) oxidation in wine as a model system, wine samples were diluted in phosphate buffer as described previously (Ibid., 1993, 284, 159), injected into carrier streams (0.16-0.98 ml/min) of air and buffer and detected at 510 nm with the detector placed within the sample loop. Calibration graphs were linear for 10^-80 ppm I. At ~0.44% and 0.019% of I in wine and using air- and buffer-carriers, RSD (n = 4 and 3) of 1.2% and 3.9%, and 1.5% and 1% were obtained, respectively. Method accuracy was assessed with the determination of I in standard sera, with an error of 8% (no details given). The use of acetone, ethanol, methanol and IBMK as carrier streams resulted in no significant system improvement.
Glucose Wine Blood Serum Spectrophotometry

"Flow Injection Amperometric Determination Of Glucose And Some Other Low-molecular-weight Saccharides Based On Oligosaccharide Dehydrogenase Mediated By Benzoquinone Systems"
Anal. Chim. Acta 1995 Volume 310, Issue 1 Pages 161-171
M. Tessemaa, T. Ruzgasb, L. Gortonc,* and T. Ikedad

Abstract: Experiments were performed using a 3-electrode cell with a SCE reference electrode, a Pt wire counter electrode and a working electrode (preparation described) which consisted of either a solid graphite rod (surface area 0.073 cm2) modified with oligosaccharide dehydrogenase (ODH), C paste electrodes modified with ODH (0.053 cm2), C paste electrodes modified with benzoquinone (BQ)/ODH or C paste electrodes modified with ODH/poly(ether amine quinone) (PEAQ). A 0.1 M phosphate buffer of pH 7 was employed as carrier (0.8 ml/min). A dual channel flow system (0.4 ml/min) was used to carry 1 mM BQ dissolved in the carrier for studies with an electrode modified with ODH. Each electrode system responded to glucose (I) and equal responses were obtained for the α- and β-anomeric forms. Calibration graphs are shown. The solid C electrode modified with ODH exhibited the highest sensitivity. The responses for 16 sugars (listed) were measured with a C paste electrode impregnated with BQ which exhibited the lowest noise; the highest currents were observed for I (100%), lactose (52%), cellobiose (50%) and maltose (49%). Selectivity profiles were very similar for the four systems.
Glucose Saccharides Amperometry Electrode Electrode Electrode

"Electrocatalysis And Amperometric Detection Of Ethanol At Ruthenium-based Inorganic Films With Improved Response Stability"
Anal. Chim. Acta 1995 Volume 310, Issue 2 Pages 257-262
Tommaso R. I. Cataldi*, Diego Centonze, Elio Desimoni and Vitina Forastiero

Abstract: A glassy carbon electrode coated with a thin film of mixed-oxidation state ruthenium oxide cross-linked with ruthenium cyanide is used for the electrocatalytic oxidation of ethanol in acidic media. This inorganic redox film offers attractive features for application as an electrocatalytic amperometric sensor in batch and flowing solutions. The ruthenium-based modified glassy carbon electrode was assembled in a thin-layer electrochemical cell, and the stability of the film was evaluated. For constant-potential amperometric detection (+ 1.05 V vs. ) in flow injection analysis, substantial improvements in the response stability of the film were obtained using carrier electrolytes spiked with 5 x 10^-6 M of each of the electroplating salts, i.e., RuCl3 and K4Ru(CN)6. Under optimal experimental conditions the peak current response increases linearly with ethanol over the range 0.1-10 mM; linear least squares fit of the data (n = 7) yielded a slope of 0.601 ± 0.003 A mM 1 (95% confidence limits) with a correlation coefficient of 0.99995.
Ethanol Amperometry Electrode

"An Integrated Design Strategy For Flow Injection Analysis Based On The Coupling Of Mathematical Modeling And Optimization Algorithms"
Anal. Chim. Acta 1995 Volume 310, Issue 2 Pages 289-296
A. Ara&uacute;jo, J. L. F. C. Lima, J. Gracia, M. Poch, J. Alonso*, J. Bartrol&iacute; and M. Del Valle

Abstract: A methodology to design a flow injection system with optimized performance characteristics was presented based on coupling a descriptive mathematical model to an optimization algorithm. The method was applied to the sequential determination of glucose and glycerol in a flow injection system using the sandwich technique. The axially dispersed plug flow model was coupled with Powell's optimization algorithm to generate a complete set of flow injection configuration, each of them optimized with respect to its objective function (better sensitivity, highest sampling rate, better resolution, etc.). The user selects the configuration which suits the requirements of the particular application.
Glucose Glycerol

"Multicommutation In Flow Analysis. 3. Spectrophotometric Kinetic Determination Of Creatinine In Urine Exploiting A Novel Zone Sampling Approach"
Anal. Chim. Acta 1995 Volume 310, Issue 3 Pages 447-452
Alberto N. Ara&uacute;joa, Jos&eacute;L. F. Costa Limaa, Boaventura F. Reisb,* and Elias A. G. Zagattob

Abstract: A single channel flow manifold equipped with three microcomputer-controlled three-way solenoid valves is described for the spectrophotometric determination of creatinine in urine using Jaffe's reaction. A plug of untreated urine was inserted into a reagent stream (0.9 ml/min) of 0.012 M picric acid in 0.48 M NaOH and passed through a heated reactor coil at 37°C (100 cm x 0.8 mm i.d.) to the spectrophotometer for detection. The volume of urine sampled and the residence time in the reaction coil were determined by controlling the switching of the solenoid valves. Volumes as low as 0.5 µL of urine were sampled. The optimized system was employed for the analysis of standard solutions containing 0.5-2 g/l creatinine and six urine samples. The RSD (n = 10) for the determination of 1.26 g/l creatinine was 2.9%. The sampling frequency was ~e;24 samples/h. Calibration graphs are shown.
Creatinine Urine Spectrophotometry

"An Online Flow Injection Analysis System For The Determination Of Acetate"
Anal. Chim. Acta 1995 Volume 316, Issue 1 Pages 117-120
Markus Tservistas, Beate Weigel and Karl Sch&uuml;gerl*

Abstract: A flow injection system for the determination of acetate is described. The method is based on the oxidation of sarcosine by immobilized sarcosine oxidase. This enzymatic reaction is competitively inhibited by acetate and the extent of the inhibition serves to calculate the acetate concentration. The effect of pH, temperature and sarcosine concentration are investigated and discussed. As an example of application, a fermentation process of E. coli was monitored with the developed system. (6 references)
Acetate ion

"Self-configuration Of Sequential Injection Analytical Systems"
Anal. Chim. Acta 1995 Volume 316, Issue 1 Pages 27-37
A. Rius, M. P. Callao and F. X. Rius*

Abstract: An expert system for the self-configuration of sequential injection analysis (SIA) systems was presented. The expert system derived all the necessary parameters for the flow system and also controlled the measurement processes including optimization, calibration and quality assurance. The expert system was applied to the SIA system for the spectrophotometric determination of Ca and Mg in water using arsenazo III as the chromogenic reagent. Detection was carried out using a diode-array spectrometer with absorption measurements every 2 nm from 450-650 nm and multivariate calibration. Ca and Mg were simultaneously determined in the range 0-280 and 0-140 mg/l, respectively, and the sample throughput was 20 samples/h.
Calcium Magnesium Environmental Spectrophotometry

"Flow Injection Column Preconcentration Directly Coupled With Electrothermal Atomization Atomic Absorption Spectrometry For The Determination Of Aluminum. Comparison Of Column Packing Materials"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 313-322
Dongxing Yuan and Ian L. Shuttler*

Abstract: A method has been developed for the determination of endogenous levels of aluminum ( gt 1 µg l-1) in water samples using an automated online pre-concentration system with flow injection coupled directly to an electrothermal atomic absorption spectrometer. Two pre-concentration materials, 8-quinolinol immobilized on controlled-pore glass (8-Q-CPG) and Amberlite XAD-2, poly(styrene/divinyl benzene) copolymer (XAD-2) were investigated and compared. Both systems were found to be suitable for pre-concentration. However, the sampling flow-rate for the 8-Q-CPG system was found to be much lower than that of the XAD-2 system, relative to the same magnitude of pre-concentration. The chelating kinetics of the 8-Q-CPG system were less favourable than the adsorption kinetics of the XAD-2 system. The detection limits (3SD) varied from 15 to 40 ng l-1, depending on the pre-concentration time, with RSDs of the order of 4% for a 1 µg L-1 concentration of aluminum. The optimum concentration range for the application of the method developed was 50 ng L-1 to 3 µg l-1. Recoveries for drinking water were in the range 100-115% for the 8-Q-CPG system and 90-100% for the XAD-2 system. The method developed was applied with varying results to the analysis of potable, fresh, river and seawater samples. (23 References)
Aluminum Water River Sea Spectrophotometry

"Flow Injection Analysis And Liquid Chromatography: Surface Enhanced Raman Spectrometry Detection By Using A Windowless Flow Cell"
Anal. Chim. Acta 1996 Volume 318, Issue 2 Pages 203-210
L. M. Cabal&iacute;n, A. Rup&eacute;rez and J. J. Laserna*

Abstract: A windowless flow cell was developed for detection by surface-enhanced Raman spectrometry (SERS) in FIA and LC. The flow cell consisted of two stainless-steel tubes (0.16 mm i.d.; 1.4 mm o.d.) mounted on an Al frame so that the ends were ~e;1.6 mm apart. The liquid draining from the upper to the lower tube was supported by surface tension and formed a column (1.4 mm diameter). The mobile phase from the FIA or LC was merged with a silver hydrosol stream then propelled in to the flow cell. The Raman spectra were recorded using a focussed Ar ion laser beam (488 nm; 85 mW) as the source. The performance of the flow cell was optimized using five drugs (amiloride, amiphenazole, 2-mercaptopyridine, pemoline and triamterene) as model analytes. The maximum SERS signal was obtained with flow rates of 0.075 ml/ml and 1.5 ml/ml for the mobile phase and silver hydrosol, respectively. The reproducibility (n = 5) of the FIA-SERS system for the determination of 625 ng amiloride was 1%.
Amiloride Amiphenazole 2-Mercaptopyridine Pemoline Triamterene LC Raman

"Enhancement Of Peroxyoxalate Chemiluminescence By Copper(II) In Flow Injection Analysis; Optimization By Factorial Design Analysis"
Anal. Chim. Acta 1996 Volume 320, Issue 1 Pages 99-105
O. M. Steijgera, H. C. M. Den Nieuwenboer, H. Lingeman*, U. A. Th. Brinkman, J. J. M. Holthuis and A. K. Smilde

Abstract: Factorial design analysis was employed to optimize the performance of a FIA system with peroxyoxalate chemiluminescence detection in the presence and absence of Cu(II). The flow injection manifold allowed a carrier stream (0.5 ml/min) containing imidazole in H2O2/acetonitrile at pH 7 to be merged with a reagent stream (0.3 ml/min) containing 5 mM bis-(2-nitrophenyl)oxalate in acetonitrile/H2O2. The fluorophore solution, 12.5 mM 3-aminofluoranthene was injected via a 8.9 µL loop and detection was performed in a chemiluminescence detector equipped with a 60 µL spiral flow cell and a 420 nm cut-off filter. Copper(II) nitrate was added to the imidazole solution for those experiments carried out in the presence of Cu(II). The first factorial design was performed in the absence of Cu(II) and four parameters were selected, namely, the concentration of imidazole and H2O2, the percentage of acetonitrile and the length of the mixing coil (l). The second factorial design was carried out in the presence of Cu(II) and three parameters were selected namely, the concentration of imidazole and Cu(II) and l.
Chemiluminescence

"Flow Injection Analysis Of Paraoxon With The Use Of An Immobilized Acetylcholinesterase Reactor"
Anal. Chim. Acta 1996 Volume 324, Issue 1 Pages 21-27
Renbing Shi and Kathrin Stein*

Abstract: A flow injection procedure for the determination of paraoxon as an example of organophosphorus pesticides based on inhibition of acetylcholinesterase immobilized on the polymer carrier VA Epoxy Biosynth was studied. The detection was carried out spectrophotometrically by means of enzymatic hydrolysis of acetylthiocholine iodide and reaction of the thiocholine from the enzymatic reaction with 5,5'-dithiobis(2-nitrobenzoic acid). Under optimal conditions for an inhibition time of 30 min the calibration graph was linear from 0.05 to 0.5 µg L-1 (r = 0.998, n = 5) with a relative standard deviation of 4.1% at 0. 1 µg l-1. For an inhibition time of 3 min the calibration graph was linear from 2 to 20 µg L-1 with relative standard deviation (n = 3) of 1.2% at 5 µg l-1. The inhibited enzyme was reactivated by 0.01 mol L-1 2-pyridinealdoxime methiodide. The recoveries from the samples to which paraoxon had been added (water, soil) were 104% and 94%, respectively. The determination of paraoxon was based on the inhibition of acetylcholinesterase. The sample solution was pumped (1.32 ml/min) for 3-30 min through an enzyme reactor (45 mm x 2 mm i.d.) packed with acetylcholinesterase immobilized onto polymer carrier VA Epoxy Biosynth. The valves were switched at the end of this inhibition time and a carrier stream of 1 mM Tris/6.64 g/l NaCl/1 g/l MgCl2 of pH 8.3 was passed through the reactor at the same flow rate. To measure the inhibition of the immobilized enzyme, 100 µL of 100 mg/l acetylthiocholine iodide was injected into the carrier stream and the liberated thiocholine was detected spectrophotometrically at 417 nm following reaction with 0.1 g/l 5,5'-dithiobis(2-nitrobenzoic acid) (0.56 ml/min). The enzyme reactor was regenerated with 0.01 M 2-pyridinealdoxime methiodide at 1.32 ml/min for 1.5 min. The calibration graphs for paraoxon were linear for 0.05-0.5 µg/l and 2-20 µg/l for inhibition times of 30 and 3 min, respectively. RSD (n = 3 or 5) were 4.1% (30 min) for 0.1 µg/l paraoxon and 1.2% (3 min) for 5 µg/l paraoxon. The recoveries for 0.1 µg/l paraoxon from spiked pond water and soil were >94% with 30 min inhibition time.
Paraoxon Pesticides, organophosphorus Pond Environmental Spectrophotometry

"Characterization Of A Membrane Interface Designed For Analytical Scale Sample Introduction Into A Mass-spectrometer"
Anal. Chim. Acta 1996 Volume 327, Issue 1 Pages 1-16
Ashok R. Dongr&eacute; and Mark J. Hayward*

Abstract: A membrane interface has been constructed for analytical scale sample introduction into a mass spectrometer. The interface was designed to be easy to use while achieving the following two goals: (i) to improve the mass transport efficiency of the analyte from the sample solution to the mass spectrometer ion source and (ii) to improve performance while reducing the sample sizes utilized for routine direct analyzes with membrane introduction mass spectrometry (MI/MS). In order to systematically characterize this interface, a variety of key mass transport parameters including membrane thickness, temperature, analyte flow rate, and pneumatic assist carrier gas flow rate have been examined. Interface characterization studies have focused primarily on two analytes, benzene and ethanol. These two analytes were chosen to compare the relative importance of each of the key mass transport parameters for the two most common applications of MI/MS, environmental analyzes and fermentation monitoring. The results of these studies suggest that mass transport of the analyte from solution phase to the membrane (including the use of the thin layer approach), membrane dimensions and membrane temperature are among the more important factors affecting analyte response and limits of quantification. Other significant results suggest that, when given a warm unrestricted path from the membrane to the ion source, the permeation (flux) of water from the aqueous matrix may be a major factor affecting the mass transport of analyte from the membrane to the ion source of the mass spectrometer. The comparison of the effects of the key mass transport parameters for environmental analyzes and fermentation monitoring shows that each of these two applications depend on a markedly different set of parameters for achieving optimal performance.
Organic compounds Fermentation broth Mass spectrometry

"Potentiometric Detection Of Carboxylic Acids By Flow Injection Analysis Using A Tungsten Oxide Electrode"
Anal. Chim. Acta 1996 Volume 332, Issue 2-3 Pages 187-192
Zuliang Chen*, and Peter W. Alexander

Abstract: Carboxylic acids were determined by FIA with potentiometric detection at a tungsten oxide electrode (Ag/AgCl reference electrode). The optimum sensitivity was achieved with 0.5 mM phosphate buffer of pH 6.5 as the carrier stream (1 ml/min). Linear calibration graphs were obtained for 0.25-1.5 mM formic acid and 0.25-5 mM propionic acid and detection limits were 10 and 50 µM, respectively, with an injection volume of 20 µL. The RSD (n = 10) for the determination of 1 mM formic acid was 1.5%. The baseline potential did not exhibit any measurable drift.
Carboxylic acids Potentiometry Electrode

"Cysteine Enhancement Of The Cryogenic Trap Hydride AAS Determination Of Dissolved Arsenic Species"
Anal. Chim. Acta 1996 Volume 333, Issue 1-2 Pages 89-96
A. G. Howard*, and C. Salou

Abstract: Pre-derivatization of arsenic species with L-cysteine prior to their determination by a modified cryogenic trap hydride AAS procedure leads to more uniform sensitivities to arsenite, arsenate, methylarsonate and dimethylarsinate and improved resistance to interferences from metal ions. This pre-treatment can be carried out at room temperature, or more rapidly by microwave heating. The conditions required for the reduction of the resulting arsenic-cysteine complexes differ from those required for the generation of hydrides from the parent compounds. In particular, lower levels of acid are required, resulting in a reduction in the acid-derived blank contributions to the inorganic arsenic response. The pre-treatment procedure has been found to improve the performance of the hydride trap procedure when measurements are made in the presence of metals such as iron(II), nickel(II), cobalt(II), manganese(II) and copper(II) which interfere in the conventional cryogenic trap HG-AAS speciation procedures. The detection limits (3s) of the four species were in the range 30-99 pg with relative standard deviations of 3.1-7.9%, giving with 1 mL samples, detection limits of ca 50 ng L-1.
Arsenic Spectrophotometry

"Sequential Injection Extraction For Sample Preparation"
Anal. Chim. Acta 1997 Volume 337, Issue 1 Pages 99-106
Kristina L. Petersona,*, Barry K. Loganb, Gary D. Christiana and Jaromir Ruzickaa

Abstract: A sequential injection extraction is presented based on the different flow velocities of aqueous and organic segments through a PTFE extraction coil (6 m x 0.8 mm i.d.) due to the hydrophobic interaction between the extraction coil and the organic segment. An air segment of 5 cm was inserted into the extraction coil followed by the organic segment and the aqueous segment. Air was then pumped into the coil to propel the aqueous segment through the organic segment which formed a coating on the inner walls of the coil. The flow direction was reversed and the aqueous segment was removed from the coil. The procedure was repeated with a second aqueous segment buffered at an optimal pH for back extraction. The technique was tested by extracting mixtures of barbiturates (as acid/neutral drugs) or serotonin re-uptake inhibitors (as basic drugs) from 500 µL urine using 50 µL butyl chloride/octanol (4:1) as the organic segment. The drugs were back extracted into 100 µL 0.45 M NaOH (for acidic/neutral drugs) or 0.18 M H3PO4 (for basic drugs) for analysis by HPLC. The absolute recoveries were 11-30% for urine samples spiked at the 50 µg/ml level. The sample throughput was 20/h.
Drugs Barbiturates Urine Sample preparation

"Chemiluminescence Detection Of Porphyrins With The Peroxyoxalate Reaction By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 339, Issue 1-2 Pages 131-138
Mei Lin and Carmen W. Huie*,*

Abstract: A flow injection chemiluminescence method was developed for determining porphyrins in biological fluids based on the reaction of bis-(2,4-dinitrophenyl) oxalate (DNPO) with H2O2. The detection cell allowed the DNPO reagent to be added to the carrier stream containing H2O2 and porphyrin at a position approximately 1 cm from the detection window. The chemiluminescence emission was detected with a photomultiplier tube via a 570 nm cut-off filter. The effects of pH, flow-rate and concentration of reagents on the chemiluminescence intensity were investigated. With the optimum conditions, viz. flow rate 1.25 ml/min, 1.5 mM DNPO, 3% H2O2 and pH 6, the calibration graphs for porphyrins were linear up to 1000 µg/ml. The recoveries for coproporphyrin from spiked urine were 97-98.2%. The method was applied to determine coproporphyrin in urine samples from healthy adults.
Porphyrins Urine Chemiluminescence

"Comparative Study Of Some Synthesized And Commercial Fluorogenic Substrates For Horseradish Peroxidase And Its Mimetic Enzyme Haemin By A Flow Injection Method"
Anal. Chim. Acta 1997 Volume 340, Issue 1-3 Pages 159-168
Yuan-Zong Li and Alan Townshend*

Abstract: Four 3,4-dihydroquinoxalin-2-(1H)-one derivatives (details given) were evaluated as fluorogenic substrates for horseradish peroxidase and its mimetic enzyme haemin. The performances of these substrates were compared to those of commercially available substrates, namely, p-hydroxyphenylacetic acid (p-HPA), p-hydroxyphenylpropionic acid (p-HPPA), homovanillic acid (HVA) and tyramine. The evaluations were performed by a FIA method in which a mixture, formed by merging substrate and buffered enzyme streams, was subsequently merged with a water carrier stream containing 150 µL H2O2. The reaction was monitored by fluorimetry at the optimum wavelength for each substrate. The substrates p-HPPA, p-HPA, NN'-dicyanomethyl-o-phenylenediamine (DCM-OPA) and 3-methyl-3,4-dihydroquinoxalin-2-(1H)-one (MDHQ) exhibited comparable performances; detection limits were at the nM level for H2O2. DCM-OPA had a better stability than MDHQ but both were stable for at least one month in a refrigerator.
Enzyme, horseradish peroxidase Enzyme, haemin Fluorescence

"Amperometric Detection Of Phenols Using Peroxidase-modified Graphite Electrodes"
Anal. Chim. Acta 1997 Volume 347, Issue 1-2 Pages 51-62
Annika Lindgren*, Jenny Emn&eacute;us, Tautgirdas Ruzgas, Lo Gorton and Gy&ouml;rgy Marko-Varga

Abstract: A solid graphite electrode modified with peroxidase was incorporated into a FIA system for the amperometric determination of phenol compounds. The method was based on the oxidation of the phenolic compound at the peroxidase electrode in the presence of H2O2 to yield the phenoxy radical. The subsequent reduction of the phenoxy radical at -50 mV vs. Ag/AgCl (Pt auxiliary electrode) generated the analytical signal. A 20 µL volume of phenol test solution was injected into a 0.1 M phosphate buffer carrier steam (0.4 ml/min) which was then merged with a 58 µM-H2O2 stream (0.4 ml/min) prepared online using glucose and a glucose oxidase reactor. The effects of (i) different electrode pre-treatments and immobilization techniques, viz. heat treatment, carbodi-imide activation, adsorption, crosslinking with glutaraldehyde and (ii) peroxidases from different biological origins on the performance of the electrode were studied. The lowest detection limit achieved for p-cresol was 0.4 µM.
Phenols 4-Cresol Amperometry Sensor Electrode Electrode

"Evaluation Of Natural Computation Techniques In The Modeling And Optimization Of A Sequential Injection Flow System For Colorimetric Iron(III) Determination"
Anal. Chim. Acta 1997 Volume 348, Issue 1-3 Pages 143-150
J. de Graciaa, M. L. M. F. S. Saraviab, A. N. Ara&uacute;job, J. L. F. C. Limab, M. del Vallec and M. Pochd,*

Abstract: The present study shows and gives evidence of the applicability of natural computation techniques in the modeling and optimization of a sequential injection flow system of anal. for colorimetric iron(III) determination in water samples. The reaction with thiocyanate is used as reagent color. A neural network consisting of two hidden layers, each one formed by eight neurons, was used to model the system. Optimization of the system in terms of sensitivity, linearity and sampling rate was carried out by using jointly the neural network and genetic algorithms. The latter were used with a set of 50 crossed and mutated chromosomes over 100 generations. In the system thus developed, 140 µL of sample and 70 µL of reagent were sequentially introduced into the holding coil and propelled toward the detector at a flow of 5 mL/min. The system gave a sampling rate of 110 samples per h. A comparison of the results obtained in the anal. of six samples with those obtained using the reference method (atomic absorption spectrophotometry) showed the high quality of results provided.
Iron(III) Spectrophotometry

"A Novel Gas Diffusion/flow Injection System Coupled With A Bulk Acoustic-wave Impedance Sensor For Total Inorganic Carbonate And Its Application To Determination Of Total Inorganic And Total Organic-carbon In Waters"
Anal. Chim. Acta 1997 Volume 349, Issue 1-3 Pages 143-151
Xiao-li Su, Li-hua Nie and Shou-zhuo Yao*

Abstract: A novel flow injection analysis (FIA) system has been developed for the rapid and selective determination of total inorganic carbonate (TIC). The method is based on the diffusion of CO2 across a PTFE gas-permeable membrane from a stream of 0.5 mol L-1 H2SO4 (0.50 mL min-1) and water (0.50 mL min-1) merging into a stream of 10 mM tris(hydroxymethylamino)-methane containing 0.5 mM KCl (1.00 min min-1). The CO2 trapped in the acceptor solution is determined online by a bulk acoustic wave impedance sensor and the signal is proportional to the concentration of TIC present in the original samples. The proposed system was applied to the direct determination of TIC in natural and waste waters and the indirect determination of the total organic carbon content based on wet chemical oxidation of the samples, it exhibited a linear frequency response up to 20 mM bicarbonate with a detection limit of 10 µM, and the precision was better than 1% (RSD) at a throughput of 45 samples per hour. The effects of composition of acceptor stream, cell constant of the conductivity sensor, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail. 32 References
Carbon, organic, total Carbon, inorganic, total Environmental Waste Sensor

"Coupling Of Column Liquid-chromatography And Surface-enhanced Resonance Raman-spectroscopy Via A Thin-layer Chromatographic Plate"
Anal. Chim. Acta 1997 Volume 349, Issue 1-3 Pages 189-197
G. W. Somsen*, S. K. Coulter, C. Gooijer, N. H. Velthorst and U. A. Th. Brinkman

Abstract: Surface-enhanced resonance Raman (SERR) spectroscopy was used to characterize compounds separated by column liquid chromatography (LC). Three percent of the effluent from a conventional-size LC column were immobilized on a moving thin-layer chromatography (TLC) plate using a spray-jet solvent-elimination interface. Next, colloidal silver was applied to the analyte spots and in situ SERR spectra were recorded with a multichannel micro-Raman spectrometer. Storage of the LC effluent avoids the need to use a continuous-flow of colloidal silver and, in principle allows compounds to be detected independently of LC conditions like eluent composition and flow rate. Using dyes as test compounds, the method was optimized and aspects were studied such as type of TLC plate, LC separation of the dyes, preservation of LC integrity during immobilization, and SERR analysis of the deposited compounds. With a silica TLC plate as deposition substrate, good-quality and characteristic SERR spectra were obtained for the dyes which were separated on a cyanoproyl-modified silica LC column with methanol-water containing the volatile additives ammonium acetate and triethylamine as eluent. The minimum identifiable concentration of the dyes was about 250 ng mL-1 (750 pg applied on the plate). For some strong Raman scatterers such as nile blue and pararosaniline, the major spectral peaks could be observed down to concentrations of 25 ng mL-1. 36 References
Raman HPLC

"Application Of Factorial Design To Improve A FIA System For Penicillin Determination"
Anal. Chim. Acta 1997 Volume 350, Issue 3 Pages 353-357
Marta M. M. B. Duartea, Graciliano de O. Netob, Lauro T. Kubotab,*, Jos&eacute;L. L. Filhoc, Maria F. Pimenteld, Fernando Limaa and Valdinete Linsa

Abstract: A potentiometric FIA system for penicillin determination, employing penicillinase immobilized on silica gel, packed into a reactor, was improved by the use of statistically designed experiments. A two-level and three-factor factorial was used to find the best working conditions evaluating the influence of some parameters on the signal response of the system and the number of determinations per hour. These parameters were analyzed individually obtaining two level of the variables to be used in the factorial design: length of the reactor (1.5 and 2.0 cm), carrier flow rate (1.6 and 2.2 mi min-1) and sample volume (100 and 150 µL). The pure error on the measurements was estimated by authentic repetitions. The ideal working conditions taking into account a compromise between the best response signal and the number of determinations per hour (with the same importance) being chosen the level of factors: length of reactor 1.5 cm, carrier flow rate 2.2 mL min-1 and sample volume of 150 µL. Under these conditions the system allowed to analyze was about 45 samples per hour, during 73 days, with a standard deviation of 2.4% at concentration range between 10^-1 and 10^-3 mol L-1. 20 References
Penicillin Potentiometry

"Total Nitrogen Determination By Flow Injection Using Online Microwave-assisted Digestion"
Anal. Chim. Acta 1997 Volume 351, Issue 1-3 Pages 273-279
A. Cerd&agrave;, M. T. Oms, R. Forteza and V. Cerd&agrave;*

Abstract: A method for the determination of total nitrogen in wastewaters involving flow injection and on-line microwave-assisted digestion is described. The method is based on the oxidation of nitrogen-containing compounds to nitrate by means of peroxodisulphate using a microwave oven as a radiation source. Nitrate is determined by the Griess-Ilosvay reaction, after reduction to nitrite by hydrazine under alkaline conditions, using sulfaniliamide and N-(1-naphtyl)ethylene diamine. A thorough study of the factors affecting the digestion process has been carried out using several nitrogen-containing compounds as test substances. Under the optimized conditions, the described method allows quantitative digestion of all the model compounds for concentrations up to 20 mg L-1 N. The method enables the analysis of 10 samples in triplicate per hour, the relative standard deviation of 10 replicates being ~3%. The detection limit is 0.21 mg l- N. The system has been applied to the determination of total nitrogen in wastewaters and the results have been compared with those obtained by Kjeldahl digestion.
Nitrogen, total Waste Sample preparation

"Elimination Of The Schlieren Effect In The Determination Of Reactive Phosphorus In Estuarine Waters By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 351, Issue 1-3 Pages 265-271
Ian D. McKelvie*, Darren M. W. Peat, G. Peter Matthews and Paul J. Worsfold

Abstract: Conventional flow injection manifolds with sample injection for the determination of reactive phosphorus in estuarine waters are limited by the Schlieren or refractive index (RI) effect which can cause major errors in quantification. A simple flow injection (FI) manifold which obviates this RI error in reactive phosphorus measurement is reported. It involves the injection of acidic molybdophosphate reagent into a carrier stream of sodium chloride solution of similar refractive index, which is then sequentially merged with a sample (the salinity of which may vary widely from sample to sample) and a reductant. Despite the occurrence of sizeable blank signals, reactive phosphorus has been successfully measured in samples with salinities ranging from 0 to 34 parts per thousand using calibration standards prepared in deionised water, with a detection limit of 6 µg L-1 P. 21 References
Phosphorus Estuarine

"A Fluorescence Flow Injection Method For The Quantitation Of Cyanide: Its Application To The Quantitation Of Bound Cyanide In Cassava Using An Immobilized Linamarase Bioreactor"
Anal. Chim. Acta 1997 Volume 354, Issue 1-3 Pages 189-196
D. Narinesingha,*, S. Saroopa and T. T. Ngob

Abstract: A fluorimetric flow injection method is described for the quantitation of cyanide ions in aqueous media. The method is based on the isoindole fluorogenic adduct formed when o-phthalaldehyde reacts with taurine in the presence of CN-ions. Under optimized flow injection conditions (loop size, 130 µl; flow rate, 0.75 mL min-1; delay coil length, 0.4 m) linear calibration curves in the range 10^-5 to 10^-7 M CN- are obtained with detection limits of 1.8 x 10^-7 M. Using naphthalene dialdehyde instead of o-phthalaldehyde the detection limit is lowered to 5.8 x 10^-8 M. Recovery yields vary between 97-102%. Incorporation of a linamarase bioreactor into the flow injection manifold gives a rapid and sensitive method for the quantitation of the cyanogenic glucoside, linamarin, in cassava. Linamarin concentrations as low as 3.2 x 10^-6 M call be detected. The immobilized linamarase shows excellent storage stability at 4°C retaining about 72% of its activity after 109 days. 19 References
Cyanide Linamarin Plant Fluorescence

"Coconut-based Plant-tissue Reactor For Biosensing Of Catechol In Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 354, Issue 1-3 Pages 325-331
Antonio W. O. Lima, Valberes B. Nascimento, Jairo J. Pedrotti and L&uacute;cio Angnes*

Abstract: A novel plant tissue biosensor is proposed in this paper. Catechol is determined by the reduction of its oxidation product on glassy carbon electrode after a biocatalytic conversion to quinone in an online coconut-based reactor by flow injection analysis. The remarkably high polyphenol oxidase activity of the tissue is successfully associated to its high stability and physical feasibility to manufacture the bioreactor. The sensor retains its enzyme activity for at least one week. Catechol can be determined at micromolar range in a rate of up to 60-90 samples per hour with good precision (RSD 2%). Optimization of the experimental parameters including bioreactor and cell design is addressed. An interference study is also included showing the limitations and other possibilities of the use for this plant material. Applicability to river water analysis and waste water is illustrated. Such use of biocatalytic material apart from the electrochemical detector still holds great advantages for easy screening of new material sources for biosensing applications. 19 References
Catechol River Waste Amperometry Sensor

"Improvement On Simultaneous Determination Of Chromium Species In Aqueous-solution By Ion Chromatography And Chemiluminescence Detection"
Anal. Chim. Acta 1997 Volume 354, Issue 1-3 Pages 107-113
Bente Gammelgaarda,*, Yi-ping Liaob and Ole J&oslash;nsa

Abstract: A sensitive method for the simultaneous determination of chromium(III) and chromium(VI) was chromatography and chemiluminescence detection. Two Dionex ion-exchange guard columns in series, CG5 and AG7, were used to separate chromium(III) from chromium(VI). Chromium(VI) was reduced by potassium sulfite, whereupon both species were detected by use of the luminol-hydrogen peroxide chemiluminescence system. Parameters affecting retention times and resolution of the separator columns, such as eluent pH, eluent composition, reductant pH and concentration, and flow rates were optimized. Furthermore, the stabilities of reductant and luminol solutions were studied. The linear range of the calibration curve for chromium(III) and chromium(VI) was 1-400 µg L-1. The detection limit was 0.12 µg L-1 for chromium(III) and 0.09 µg L-1 for chromium(VI), respectively. The precision at the 20 µg L-1 level was 1.4% for chromium(III) and 2.5% for chromium(VI), respectively. The accuracy of the chromium(III) determination was determined by analysis of the NIST standard reference material 1643 c, Trace elements in water with the result 19.1±1.0 µg Cr(III) L-1 (certified value 19.0±0.6 µg Cr(III) l-1). The method was applied to analyze the stability of chromium patches for contact dermatitis testing. 19 References
Chromium(III) Chromium(VI) NIST 1643 Water Pharmaceutical Chemiluminescence HPIC

"Magnesium Ion-selective Electrode Optimization And Flow Injection Analysis Application"
Anal. Chim. Acta 1997 Volume 356, Issue 1 Pages 105-111
Nikolas A. Chaniotakisa,*, John K. Tsagatakisa, Elizabeth A. Moschoua, Steven J. Westb and Xiaowen Wenb

Abstract: The development of manual and Flow Injection Analysis (FIA) methods for the determination of magnesium in aqueous samples by means of a magnesium ion-selective electrode (ISE) is described. A sample pre-treatment solution containing pH buffering compounds and alkaline earth metal complexing agents was developed to minimize interferences and optimize the limits of detection. For the achievement of the desired potential stability of the electrode in the FIA mode, a pulseless syringe pump was employed to eliminate the possibility of a variable streaming potential. This, in conjunction with a laminar flow cell with low and well-controlled dead volume allowed for the simple, semi-automatic, direct, inexpensive, and accurate determination of magnesium in water samples. Results from both the manual and FIA method were corroborated by capillary electrophoresis (CE) and Atomic Absorption Spectroscopy (AAS). 16 References
Magnesium(II) Blood Serum Water Electrode Potentiometry

"Standard Additions In Flow Injection Analysis With Atomic Absorption Spectrometry"
Anal. Chim. Acta 1997 Volume 357, Issue 1-2 Pages 151-156
B. Haghighi, N. Maleki and A. Safavi*

Abstract: A standard additions method in flow injection atomic absorption analysis has been described. The proposed method was applied to the determination of calcium in synthetic samples with and without chemical interference and the results were compared with those obtained by the conventional standard additions method in atomic absorption spectrometry. The influence of parameters of the how injection system was studied. The results showed that the proposed method was independent of such parameters. The relative standard deviations within and between analyzes were found to be 1.61 and 1.81%, respectively, at the 1.5 µg mL-1 Ca level. The method was used for the determination of calcium in tap water.
Calcium Water Spectrophotometry

"Flow Injection Chemiluminescence Determination Of Hydrazine"
Anal. Chim. Acta 1998 Volume 358, Issue 2 Pages 121-125
A. Safavi* and M. R. Baezzat

Abstract: A sensitive and selective flow injection chemiluminescence method for the determination of hydrazine over the range 1 x 10^-6 to 5 x 10^-5 M is described. The method is based on the chemiluminescence emitted during the oxidation of hydrazine by N-bromosuccinimide in alkaline medium in the presence of dichlorofluorescein as sensitizer. The presence of citrate prevents the precipitation of some cations in the reaction medium and also causes an enhancement in chemiluminescence intensity. Development of the method includes optimization of reagent concentrations and flow conditions. The optimized method yielded a 2s detection limit of 5 x 10^-7M. The method also has good selectivity. The method is simple, fast, selective, and precise.
Hydrazine Chemiluminescence

"A Novel FIA Configuration For The Simultaneous Determination Of Nitrate And Nitrite And Its Use For Monitoring An Urban Waste Water Treatment Plant Based On N/D Criteria"
Anal. Chim. Acta 1998 Volume 359, Issue 1-2 Pages 173-183
D. Gabriel, J. Baeza, F. Valero and J. Lafuente*

Abstract: A novel FIA configuration for the simultaneous determination of nitrate and nitrite, and its automation for monitoring an urban wastewater treatment plant (WWTP) based on nitrification/denitrification criteria, are proposed. The detection range achieved is 0.25-50 mg L-1 for nitrate and 0.05-5 mg L-1 for nitrite (0.056-11.29 mg N-NO-3 L-1 and 0.015-1.52 mg N-NO-2 L-1). The max. sampling frequency is 180 samples/day and the Relative Standard Deviation (RSD, n=5) was 1.1% at 5 mg L-1 nitrite and 2.3% at 50 mg L-1 nitrate plus 1 mg L-1 nitrite. The particle size of the reductant (Cd) and the use of Cu as a catalyst influencing the stability of the reduction column were examined and an electronic calibration system was developed in order to increase the capacity of the equipment to operate unattended with a view to its use at WWTP. The max. unattended deployment time is four days. The proposed configuration was validated by analyzing real water samples at a pilot plant based on nitrification/denitrification criteria with optimal results.
Nitrate Nitrite Waste Spectrophotometry

"Evaluation Of The Adsorptive Immobilization Of Horseradish Peroxidase On PTFE Tubing In Flow Systems For Hydrogen Peroxide Determination Using Fluorescence Detection"
Anal. Chim. Acta 1998 Volume 359, Issue 1-2 Pages 149-156
Yuan-zong Li and Alan Townshend*

Abstract: A simple means of immobilization of horseradish peroxidase (HRP) on the inner wall of PTFE tubing by phys. adsorption was described. The HRP-immobilized tubing was used to form a reaction coil that was inserted into a flow system. Various conditions influencing the reaction, immobilization, desorption, and stability of the reaction coil were evaluated by a flow injection method based on HRP-catalyzed fluorescence of the reaction of H2O2 with p-hydroxyphenylpropionic acid as the fluorogenic substrate. Re-immobilization showed good reproducibility when 1% (w/v) sodium dodecyl sulfate (SDS) was used to desorb the denatured enzyme and proteins from the wall of PTFE tubing. The immobilized reaction coil was stable for at least a month if it was kept in buffered phosphate solution at pH 5.8 in a refrigerator. The immobilized coil was washed with 1.0 x 10^-4 mol/L substrate solution for 40 h at a flow rate of 1.5 mL/min without losing activity. When the substrate and 200 nmol/L H2O2 were continuously reacted and flowed through the reaction coil, the response was stable for 7 h (equivalent to ~1400 150 µL injections of 600 nmol/L H2O2) and retained 79% of its activity after 26 h of continuous reaction. The immobilized HRP was very sensitive to bubbles introduced into the flow system. Linear relationships between fluorescence intensity and H2O2 concentration. were obtained in the range 4-80 ng/mL with HRP solution and with the immobilized reaction coil system. The detection limit (S/N=3) was 2 nmol/L H2O2 in both cases. The relative standard deviations (8 replicates) for the detection of 4 and 80 nmol/L H2O2 were 5% and <1%, respectively.
Hydrogen peroxide Fluorescence

"Modeling And Optimization Studies For A Sequential Flow Based Bio-analytical System"
Anal. Chim. Acta 1998 Volume 359, Issue 1-2 Pages 157-171
Sameer Parab, Bernard J. Van Wie*, Ian Byrnes, Edgar J. Robles, Bruce Weyrauch and Thomas O. Tiffany

Abstract: The clinical applications of the sequential flow technique are emphasized in this study by considering glucose determinations in a standard blood chemical analysis. The sequential flow configuration is modeled to predict experimental behavior. A rigorous theoretical formulation of the model is presented incorporating temperature relationships for the hydrodynamic and kinetic parameters. A comparisons of model predictions with experiments show agreement satisfactory for determining optimal design strategies. To perform this analysis, factorial design results of model predictions are used to locate regions where a full set of model predictions should be made. Also, experimental results and theoretical predictions are used to determine the best temperature for glucose determinations
Glucose Blood

"Application Of Differential Electrolytic Potentiometry For Detection In Flow Injection Analysis"
Anal. Chim. Acta 1998 Volume 360, Issue 1-3 Pages 195-201
A. M. S. Abdennabi*, M. E. Koken and M. M. Khaled

Abstract: The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is studied. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as c.d., concentrations. of the solutions, and the flow rate were optimized. Chloride in water was determined by this system. The relation between chloride concentration. and the measured signal was Nernstian for concentrations. >6 µg Cl-/mL. For solutions below this concentration, the relation is linear.
Chloride Water Potentiometry Electrode

"Quartz Crystal Biosensor For Detection Of The African Swine Fever Disease"
Anal. Chim. Acta 1998 Volume 362, Issue 1 Pages 91-100
Erich Uttenthaler*, Conrad K&ouml;&szlig;linger and Stephan Drost

Abstract: An immunosensor for the detection of the African Swine Fever (ASF) disease in infected pigs is presented. A sensitive, direct immunoassay for measurements in diluted pig sera was established using the virus protein 73 (VP73) as a highly specific receptor layer for a mass sensitive piezoelec. quartz crystal. The fundamental sensor effect of this transducer is based on the linear dependence of the resonance frequency of an oscillating quartz crystal upon the binding of mass on the coated surface during the measurement. A quartz crystal which is coated with VP73 is an highly specific sensor and allows to detect the ASF-antibodies in the sample through mass accumulation on the surface of the quartz crystal. An appropriate immobilization technique for VP73 was established and a suitable carrier buffer for the flow injection analysis system was developed during this study. Regeneration of the receptor layer is possible for about ten times. With this quartz crystal microbalance, results were available within a few minutes and with a selectivity comparable to a licensed microtiterplate ELISA. Measurements with real pig serum samples have proven the suitability of the quartz crystal biosensor for the classification ofpositive and negative pig serum samples.
African swine fever virus Protein Serum Pig Microbalance Sensor Immunoassay

"Determination Of 5-hydroxytryptamine (serotonin) And Related Indoles By Flow Injection Analysis With Acidic Potassium Permanganate Chemiluminescence Detection"
Anal. Chim. Acta 1998 Volume 362, Issue 2-3 Pages 131-140
Neil W. Barnett*, Benjamin J. Hindson and Simon W. Lewis

Abstract: A simple, rapid and sensitive method for the determination of 5-hydroxytryptamine (serotonin), 5-hydroxytryptophan or 5-hydroxyindole-3-acetic acid, using flow injection analysis with acidic potassium permanganate chemiluminescence detection, is described. The log-log plots for 5-hydroxytryptamine, 5-hydroxytryptophan and 5-hydroxyindole-3-acetic acid gave equations of best fit, of y = -0.03x2+0.51x+6.15 (r2 = 0.9990), y = -0.05x2+0.35x+5.70 (r2 = 0.9995) and y = -0.04x2+0.49x+5.60 (r2 = 0.9999), respectively., where y is log (chemiluminescence emission response (mV)) and x is log (concentration. (M)). The log-log calibration functions for the three analytes approximated linearity in the concentration. range from 1 x 10^-8 to 1 x 10^-6 M, where the slopes of the log-log plots were within the range from 1.01 to 1.04. The precision (measured as relative standard deviation) for 5-hydroxytryptamine was 2.3% (n = 6 at 1 x 10^-7 M). The detection limits (signal-to-noise ratio = 3) were 2 x 10^-9 M, 3 x 10^-9 M and 1.5 x 10^-8 M for 5-hydroxytryptamine, 5-hydroxytryptophan and 5-hydroxyindole-3-acetic acid, respectively. Preliminary experiments using an extended range photomultiplier tube realized enhanced detection limits due to the wavelength of max. emission being centered around 670 nm rather than 610 nm as previously thought. (34 References)
5-Hydroxytryptamine Indoles 5-Hydroxytryptophan 5-Hydroxyindole-3-acetic acid Biological fluid Chemiluminescence

"Real-time Simplex Optimization Of Flow Injection Systems For Chemical Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 313-318
Maria Fernanda Gin&eacute;*, Robinson L. Tuon, Andr&eacute; A. Cesta, Ana Paula Packer and Boaventura F. Reis

Abstract: A computer controlled flow injection system was assembled to implement a real-time simplex algorithm. Two experimental variables, flow rate and sample:reagent ratio were controlled by a fully automated manifold. A computer interface was programmed to command the pumping speed, introduction of sample:reagent amounts by solenoid valves, on-time data acquisition, and examn. of detector responses for application of the simplex algorithm. The feasibility of the approach was assessed by optimizing the flow parameters for Cl- determination in water with different analyte concentrations Optimum experimental conditions for 5.00, 25.0, 50.0, and 100 mg/L Cl- were maintained. A precision characterized by a relative standard deviation <1% and a sample throughput of 120/h were attained.
Chloride Water Spectrophotometry

"Use Of Column With Modified Silica For Interfering Retention In A FIA Spectrophotometric Method For Direct Determination Of Vitamin C In Medicine"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 11-22
Julio Cesar B. Fernandes, Graciliano de Oliveira Neto and Lauro T. Kubota*

Abstract: A flow injection analysis (FIA) system with a column packed with silica modified with aminopropyl groups was used as a reactor in the spectrophotometric determination of L-ascorbic acid at 265 nm. The column (2.79 mm ID, 50 mm length) packed with modified silica (200 mg silica treated with 3-aminopropyltriethoxysilane) was used to eliminate interfering compounds by ion pair formation with amino groups. The interfering compounds studied included tartaric, citric, oxalic, and maleic acids, glucose, fructose, EDTA, Na benzoate, and Na salicylate. A processing rate of 30 samples/h, detection limit of 2.0 x 10^-6 M, and linearity range between 10^-5 and 10^-4 M were achieved in optimized conditions. The relative standard deviation was 1.5% (n=20) for a 5.0 x 10^-5 M ascorbic acid solution The method was applied to drug samples to determine ascorbic acid; the results were in agreement of the nominal values.
Ascorbic acid Pharmaceutical Spectrophotometry

"Determination Of Reducing Sugars By Flow Injection Gravimetry"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 119-125
Raquel P. Sartini, Cl&aacute;udio C. Oliveira, Elias A. G. Zagatto* and H. Bergamin Filho

Abstract: A flow injection procedure for gravimetric determination of reducing sugars was developed. The system was designed to permit the monitoring of an inline formed suspension. In view of the high density of the ppt., a product of oxidation of reducing sugars by Fehling reagent, the Archimedes principle was exploited, so that the ppt. was weighed inside the flowing stream. Sample and reagents were simultaneously injected into two convergent carrier streams flowing through a reaction coil immersed in boiling water under reflux. The ppt. was formed, cooled, accumulated on a sintered glass mini-filter and weighed. An acidic solution was then injected into both carrier streams to promote inline solubilization of the ppt. Characteristics of the filtering device, geometry of the debubbler, flow rates, wash solution and possibilities of weighing with the filtering unit on the plate of the anal. balance or suspended under it were studied. Also, effects of reagent concentration, temp., surfactant addition and available time for reaction were studied. The gravimetric flow injection system was very stable and required only 0.64 g Cu2+ per determination Ppt. drying was not needed. Precise results (relative standard deviation usually <0.9%), in agreement with an official titrimetric procedure, were obtained within 0.20 and 1.00%(w/v) invert sugar. A new weighing was accomplished every 6th minute.
Sugars, reducing Gravimetry

"Flow Injection Spectrophotometric Determination Of Total Phenols Using A Crude Extract Of Sweet Potato Root As Enzymic Source"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 111-118
Iolanda da Cruz Vieira and Orlando Fatibello-Filho*

Abstract: A flow injection spectrophotometric method is proposed for the determination of total phenols in industrial wastewaters. After selection of the extraction medium (e.g., buffer-to-tissue ratio, pH, buffer concentration, protective agents and/or stabilizers) and storage conditions, crude ext. of sweet potato root (Ipomoea batatas (L.) Lam.) was used as an enzymatic source of polyphenol oxidase (PPO; EC 1.14.18.1) directly in the carrier. This enzyme catalyzes the oxidation of mono-, di-, and polyhydric phenols to o-quinones which can couple to each other producing melanin-like pigments with a strong absorption at 410 nm. For the optimum extraction conditions, the enzyme activity did not vary for at least five months when stored at 4°C and decreased only 4-5% during an 8 h working period at 25°C. The results obtained for the determination of total phenols in industrial wastewaters are in good agreement with results obtained using a conventional manual method (correlation coefficient, r=0.9954). Twenty-six results were obtained per h, and the relative standard deviation (RSD) was less than 2.7% (n=6) for all samples. The detection limit (three times the signal blank/slope) was 1.0 x 10^-5 mol/L and the recovery of catechol from three samples ranged from 96.4 to 102.7% of added amt.
Phenols, total Industrial Spectrophotometry

"Flow Injection Determination Of Catechol With A New Tyrosinase/DNA Biosensor"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 137-145
Patr&iacute;cia Dantoni, S&iacute;lvia H. P. Serrano*, Ana Maria Oliveira Brett and Ivano G. R. Gutz

Abstract: Biosensors find application in flow anal. due to their high selectivity and sensitivity. Decrease in the response during extended use, originated by degrdn., inhibition or structural changes of the enzyme or leaching of active components by the flow, is the prevailing problem. As an alternative to additives and preparation techniques cited in the literature, it probably uses DNA as a matrix for improving preservation of the activity of a diphenol-sensor-based tyrosinase, Tyr, (EC 1.14.18.1). The Tyr-DNA mixture was incorporated into carbon paste, CP-DNA-Tyr, or applied on glassy carbon, GC-DNA-Tyr. The CP-DNA-Tyr, covered by a membrane of Cuprophan, presented superior performance in amperometric operation under flow conditions (electroredn. of the products of the enzymatic oxidation of diphenols in the presence of O2). In comparison with paste electrodes without DNA, CP-Tyr, a current increase of one order of magnitude was observed for catechol FIA peaks, with good repeatability during several hours of operation. The response decayed ~50% after every 3 to 4 days of use (with dry storage at 4°C overnight). Original performance was recovered by simply substituting the used paste for a new portion of stock paste, stable for 2 mo under refrigeration. Evaluation of 18 different substrates and potential interferents indicated that, at the adopted potential of -0,15 V vs. Ag/AgCl. Only p-cresol gives a response comparable to catechol. Flow injection determination of catechol samples was conducted at a frequency of 30 injections/h, with linear response from the detection limit of 1 x 10^-6 up to 5 x 10^-5 mol L-.
Catechol Amperometry Electrode Electrode Electrode Sensor

"Simultaneous Monitoring Of Glucose And L-lactic Acid During A Fermentation Process In An Aqueous Two-phase System By Online FIA With Microdialysis Sampling And Dual Biosensor Detection"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 127-135
Rong Wei Mina, Vijay Rajendrana, Niklas Larssona, Lo Gortona,*, Jordi Planasb and B&auml;rbel Hahn-H&auml;gerdalb

Abstract: The prodn. of L-lactic acid by Lactococcus lactis (ATCC 19435) during fermentation in an aqueous two-phase system (ATPS) was monitored online using microdialysis sampling coupled to a dual flow-through electrochemical cell housing glucose and lactate biosensors, which enabled the simultaneous and selective monitoring of both glucose and L-lactic acid. The amperometric biosensors were based on the co-immobilization of glucose oxidase (GOD) for the glucose sensor and L-lactate oxidase (LOD) for the lactate sensor, respectively, with horseradish peroxidase (HRP) in a carbon paste matrix. The sensors characterized regarding the sensitivities, pH optima and operational stabilities were found to be satisfactory within the required range and time of measurements. The online setup was found to be a flexible system for the monitoring of both glucose and L-lactic acid simultaneously, allowing a sampling frequency of 15 h-1 and with a delay between sampling and detection of less than 3 min. Comparison of the online measurements with a standard off-line anal. using HPLC agreed well suggesting the suitability of the system for application in very complex matrixes.
Glucose l-Lactic acid Fermentation broth Sensor Amperometry Electrode Electrode

"Potentiometric Biosensor For Control Of Biotechnological Production Of Penicillin G"
Anal. Chim. Acta 1998 Volume 368, Issue 3 Pages 205-210
Ewa Leszczyskaa, Stanis

Abstract: A pH-membrane electrode with tridodecylamine as a hydrogen ion-selective ionophore was used for the construction of a biosensor for the benzylpenicillin determination The electrode was enzymatically modified by covalent binding of penicillinase directly to the membrane surface. The high sensitivity and short response time of the biosensor allows its application in flow injection analysis (FIA). Up to 30 samples per h can be analyzed in the flow system. The FIA system with the biosensor was successfully used for the determination of penicillin G in fermentation broth. An optimized anal. procedure results in minimization of interferences from pH and buffer capacity of the real samples. No interferences from inorganic, organic and bioorganic components present in the fermentation medium were observed An important advantage of the presented anal. system is the long-term stability due to the long lifetime of the biosensor. Consequently fermentation bioprocesses can be controlled using the same biosensor for about two months. Due to the high sensitivity and selectivity, the presented method for the penicillin determination in real biotechnology samples gives analytical results comparable to those obtained using methods recommended by pharmacopoeias.
Benzylpenicillin Penicillin G Fermentation broth Electrode Electrode Electrode Potentiometry Sensor

"Flow Injection Chemiluminescence Determination Of Pyrogallol"
Anal. Chim. Acta 1998 Volume 368, Issue 1-2 Pages 113-116
A. Safavi* and M. R. Baezzat

Abstract: A sensitive and selective flow injection chemiluminescence method for the determination of pyrogallol over the range 5 x 10^-7 - 3 x 10^-5 M is described. The method is based on the chemiluminescence produced during the oxidation of pyrogallol by N-bromosuccinimide in alkaline media. The emission intensity is greatly enhanced if hydroxylammonium chloride and a cationic surfactant cetyltrimethylammonium bromide are also present in the reaction solution Method development includes optimization of reagent concentrations and the flow conditions. The optimized flow injection procedure yielded a 2s detection limit of 2 x 10^-7 M pyrogallol, and a relative standard deviation of 1.6% (n = 8) at 8 x 10^-6 M pyrogallol.
Pyrogallol Chemiluminescence

"A Time-based Flow Injection-cold Vapor-atomic Absorption Spectrometry System With Online Microwave Sample Pre-treatment For The Determination Of Inorganic And Total Mercury In Urine"
Anal. Chim. Acta 1998 Volume 369, Issue 1-2 Pages 57-67
M. Gallignani*, H. Bahsas, M. R. Brunetto, M. Burguera, J. L. Burguera and Y. Petit de Pe&ntilde;a

Abstract: A time based injection system used in conjunction with cold vapor generation atomic absorption spectrometry and microwave-aided heating oxidation with potassium persulfate has been developed for the determination of total and inorganic mercury in urine samples. Inorganic mercury is determined after reduction with SnCl2 while total mercury is determined after an online oxidation step with persulfate prior to the reduction step to elemental mercury with SnCl2. The difference between total and inorganic mercury determines the organomercury content in samples. Experimental parameters were optimized by the univariate optimization method. A linear calibration graph was obtained in the range 0.2-20 µg L-1 of Hg2+ by using injection times from 0 to 12 s of a solution of 20 µg L-1 of either inorganic or organic mercury. The detection limit based on 3s of the blank signal was 0.1 µg Hg L-1 regardless of the mercury species under evaluation. The relative standard deviations for five independent measurements were 1.5% and 1.0% for total and inorganic mercury. The recoveries of different amounts of inorganic and organic mercury added to urine samples ranged from 98.5% to 102.2% and from 97.0% to 103%, respectively. Good agreement with certified values of the total mercury containing urine reference materials were also obtained. With the proposed procedure, 20 urine samples of unexposed subjects from Merida city were measured; and the values lay in the range between 1.8 and 6.7 µg l-1. In addition, the use of a mercury standard solution as the carrier converts the flow injection manifold used in this work to an online standard addition system which permits a rapid and simple test for monitoring the mercury levels in these samples.
Mercury(II) Mercury Urine Spectrophotometry Sample preparation

"Potentiometric Enzyme Electrode In A Flow Injection System For The Determination Of Urea In Human Serum Samples"
Anal. Chim. Acta 1998 Volume 369, Issue 1-2 Pages 129-137
Izabela Wa