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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Method comparison

Classification: Chemometrics -> Method comparison

Citations 1234

"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 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

"A Robust Multi-syringe System For Process Flow Analysis. Part 3. Time Based Injection Applied To The Spectrophotometric Determination Of Nickel(II) And Iron Speciation"
Analyst 2001 Volume 126, Issue 6 Pages 903-910
Fernando Albertús, Andreu Cladera, Eduardo Becerra and Victor Cerdà

Abstract: A new software-controlled time-based system for sample or reagent introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one multi-port selection valve, the time-based injection of precise known volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Two multi-syringe time-based injection (MS-TBI) systems were implemented: first, the injection of a sample in a multiple-channel manifold where the sample would sequentially merge and react with different reagents, and second, the sequential injection of several solutions (sample and reagents) into a particular flowing stream. The first system was applied to the spectrophotometric determination of nickel(ii) in diluted samples from the acidic nickel ore leaching process, by using ammonium citrate as carrier, a saturated solution of iodine as oxidizing agent and alkaline dimethylglyoxime as chromogenic reagent. The sampling frequency attained was 57 h-1. Determinations on process samples compared well at the 95% confidence level with the reference values obtained by ICP-OES. The second time-based injection system was applied to the speciation of iron. Total iron and iron(ii) concentrations were separately and sequentially determined using 1,10-phenanthroline in acetic buffer medium as reagent. The developed manifold allowed the optional use of two different carrier solutions, containing or not containing ascorbic acid, for performing the separate determinations. Also, in the sequential procedure, plugs of reducing carrier were alternatively intercalated before the sample injections used for total iron determinations. Sampling frequencies of 68 injections per hour were routinely used. Accuracy was assessed by analyzing synthetic known mixtures of Fe(iii) and Fe(ii) standard solutions. Recoveries of 98-100.5% with a maximum relative standard deviation of 3.6% were found. Results obtained for various samples of fertilizers agreed well with those attained by the standard batch procedure.
Nickel(II) Commercial product Leachate 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

"Determination Of Sulfur Dioxide In Wines By Gas-diffusion Flow Injection Analysis Utilizing Modified Electrodes With Electrostatically Assembled Films Of Tetraruthenated Porphyrin"
Anal. Chim. Acta 1999 Volume 387, Issue 2 Pages 175-180
Carla M. N. Azevedo, Koiti Araki, Henrique E. Toma and Lúcio Angnes

Abstract: Reported is a new method for the determination of both Gee and total SO2 in wine, specially designed for FIA. The method involves separation of the analyte using a flow-through gas diffusion unit, in line with an amperometric detector consisting of a glassy carbon electrode modified with electrostatically assembled films of a tetraruthenated porphyrin. The results demonstrate a good accuracy, comparable with those obtained using the conventional iodometric method. In addition, the method can be readily applied to red, white and rose wines; it is free from interference of the other compounds of wine, consumes small amounts of sample and is faster than the iodometric method.
Sulfur dioxide Wine Red Wine White Wine Rose Electrode

"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

"Metals Determination In Wines By Sequential Injection Analysis With Flame Atomic Absorption Spectrometry"
Am. J. Enol. Vitic. 2000 Volume 51, Issue 2 Pages 131-136
Rui Cerdeira C. Costa, M. Isabel Cardoso, and Alberto N. Ara&uacute;jo

Abstract: This paper describes the application of sequential injection analysis with flame atomic absorption spectrophotometric detection (SIA/FAAS) for the determination of Zn, Mn, Fe, and Cu in Portuguese Verde, Maduro, and Porto wines. The basic configuration of the system allowed the determination of Zn, Mn, Fe, and Cu, the latter in concentrations higher than 0.20 mg/L. Selecting a sample volume of 340 µL allowed the determination of Zn and Mn up to 1.50 and 3.00 mg/L, respectively. The Fe determination was accomplished using 85, 120, and 340 µL sample volumes for Fe contents in the range of 1.50 to 15.00 mg/L, 0.50 - 10.00 mg/L, and 0.25 - 5.00 mg/L, respectively. Wine samples with Cu contents in the 0.20 to 2.00 mg/L range were analyzed with a sample volume of 750 µL. The determination of Cu trace levels was carried out using an heterogeneous-phase pre-concentration unit composed of a commercial cartridge packed with silica C18 coupled to the system. Cu was retained as diethylammonium-N,N-diethyldithiocarbamate chelate. Using about 2 mL of sample allowed determination of Cu between 0.05 and 0.50 mg/L. A comparison of the results obtained by the proposed methodologies and the reference procedures presented relative deviations less than 5%. Repeatability of determinations was always better than 3% (RSD).
Zinc Manganese Iron Copper Wine Spectrophotometry

"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

"Preparation And Preliminary Evaluation Of Anhydrous Tris(2,2 -bipyridyl)ruthenium(III) Perchlorate As A Temporally Stable Reagent For Analytical Chemiluminescence"
Anal. Chim. Acta 2000 Volume 421, Issue 1 Pages 1-6
Neil W. Barnett, Ben J. Hindson, Simon W. Lewis, Stuart D. Purcell and Philip Jones

Abstract: A new method for producing solutions of tris(2,2-bipyridyl)ruthenium(III) ([Ru(bipy)(3)](3+)) which have significantly improved stability over other methods is presented and preliminary analytical evaluation of the reagent for chemiluminescence is reported. The synthesis of anhydrous tris(2,2-bipyridyl)ruthenium(III) perchlorate ([Ru(bipy)(3)](ClO4)(3)) salt is described and the use of acetonitrile as solvent to minimise the presence of water which can be oxidized by [Ru(bipy)(3)](3+), which causes the inherent instability. The stability of the new reagent in acetonitrile was monitored spectrophotometrically (lambda(max) similar to 674 nm) and a decrease of <6% was observed. A flow injection analysis experiment was conducted using codeine to generate chemiluminescence to quantify the stability of the new reagent over 50 h. The results show a decrease in the chemiluminescence signal of <8%, which is a considerable improvement over previous methods.
Codeine Chemiluminescence

"New Ways Of Enzymatic Two-substrate Determinations In Flow Injection Systems"
Anal. Chim. Acta 2000 Volume 421, Issue 1 Pages 7-18
Thomas Matthias Becker and Hanns-Ludwig Schmidt

Abstract: This contribution presents two new conceptional strategies for the simultaneous determination of two substrates in flow injection systems. In most biotechnological processes, the substrate consumed as well as the product produced are of special interest for supervision and control. In most cases, substrate and product are interrelated via a redox reaction chain or the law of mass action, respectively. Their enzymatic analysis using dehydrogenases needs often in most cases the use of the cosubstrate in opposite redox states (NAD(+) or NADH). The consequence in a simultaneous two-substrate analysis is a more complex experimental setup. This paper describes two principal new concepts, using only one cosubstrate solution and in situ generation of the cosubstrate in the opposite redox state or a procedure using equilibrium constants, respectively. So opposite configuration requirements, or two substrates which are interrelated as substrate and product of the enzymatic analysis can be determined simultaneously, keeping the analysis system minimised. The determination of ethanol/acetate and the analysis of glucose/fructose serve as models for the proposed methods. A comparison of the results with established standard analysis kits is given.
Ethanol Acetate ion Glucose Fructose Fermentation broth Sensor

"Use Of Flow Injection Sample-to-standard Addition Methods For Quantification Of Metals Leached By Selective Chemical Extraction From Sewage Sludge"
Anal. Chim. Acta 1999 Volume 381, Issue 2-3 Pages 297-305
I. Lavilla, B. Perez-Cid and C. Bendicho

Abstract: The flow injection sample-to-standard addition method (FI-SAM) proposed by Israel and Barnes and a modification of it was employed for determination of the extractable contents of chromium, lead, nickel and zinc in a sewage sludge sample obtained from an urban wastewater processing plant. The new calibration method was a modification of the one established by Israel and Barnes in which the sample was injected into a blank solution and two different standard solutions. The advantages of this modified calibration method were: (i) sample consumption was minimized in comparison with the reverse flow injection method since the sample was not used as carrier; (ii) a blank that was matrix matched to the sample was not required; (iii) a similar precision was observed in comparison with the original procedure. For studying FI-SAM calibration strategies, extractable metals obtained by using two known sequential extraction schemes (Tessier and BCR) were determined. Only fractions that required calibration with the standard addition method for metal determination were considered. FI-SAMs compensate for interference effects caused by concomitants co-extracted at each stage of the sequential extraction scheme from sewage sludge, for all metals studied except for chromium.
Chromium Lead Nickel Zinc Sludge Spectrophotometry

"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

"Flow Injection Chemiluminometric Determination Of Albumin"
Anal. Chim. Acta 2000 Volume 403, Issue 1-2 Pages 137-143
N. T. Deftereos, N. Grekas and A. C. Calokerinos

Abstract: A new, simple analytical procedure for the determination of 5.00-300 µg mL-1 of albumin is presented, based on the chemiluminogenic reaction of the analyte with potassium permanganate in the presence of polyphosphoric acid (PPA). Serum globulins are also chemiluminescent, but their interference was eliminated by precipitation with saturated ammonium sulfate solution. The low limit of detection (4 µg ml-1) allows extensive dilution of the samples after globulin precipitation so that no other interferences are observed. Relative standard deviations were in the range 0.4-3.8% and the method was applied to the determination of albumin in human sera with good agreement with the bromcresol green (BCG) spectrophotometric method.
Albumin Serum Human Chemiluminescence

"Determination Of Sulfur Dioxide And Ascorbic Acid In Beverages Using A Dual Channel Flow Injection Electrochemical Detection System"
Anal. Chim. Acta 2000 Volume 416, Issue 1 Pages 105-110
Terence J. Cardwell and Melinda J. Christophersen

Abstract: A new flow injection method is described for the simultaneous determination of ascorbic acid (AA) and sulfur dioxide in red and white wines and various fruit juices. The flow injection manifold consists of a dual channel amperometric detection system, where AA is detected at a glassy carbon electrode set at +0.42 V (versus Ag/AgCl) and sulfur dioxide is detected at a platinum electrode at +0.90 V (versus Ag/AgCl) after separation by a gas diffusion unit. In the application of this method to the analysis of both analytes in wines and fruit juices, the results for white wines, fruit juices and juice concentrates agree well with data obtained by ion-exclusion chromatography. However, in the case of red wines and a sweet white wine, it is necessary to extract the analytes using solid phase extraction on a quaternary amine SAX cartridge before acceptable results are achieved by the new flow injection method. The linear dynamic range for AA is 3-50 mg/l with a detection limit of 1.5 mg/l and for sulfur dioxide the linear range is 0.25-15 mg/l with a detection limit of 0.05 mg/l. The sampling frequency for both analytes is 30/h.
Ascorbic acid Sulfur dioxide Wine Red Wine White Amperometry Electrode Electrode

"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

"Determination Of Chloride By Multisyringe Flow Injection Analysis And Sequential Injection Analysis With Potentiometric Detection"
Anal. Chim. Acta 2002 Volume 467, Issue 1-2 Pages 25-33
A. Andrade-Eiroa, J. A. Erustes, R. Forteza, V. Cerd&aacute; and J. L. F. C. Lima

Abstract: This paper reports for the first time a multisyringe flow injection analysis (MSFIA) method with potentiometric detection for the automated determination of chloride in waters. The methodology developed was applied to the determination of chloride in mineral, tap and waste waters and the results achieved were compared with those obtained by a potentiometric sequential injection analysis (SIA) method reported in the literature. When Mohr titration was carried out for validating the results offered by both techniques, no significant differences were found. The linear ranges were between 6 and 3500 µg L-1 for MSFIA and 10 and 3500 mg L-1 for SIA; the UPAC limits of detection were 2.7 mg L-1 for MSFIA and 1.6 mg L-1 for SIA; reproducibility was ~0.8% for MSFIA and 0.4% for SIA and, sampling rates were of 30 and 15 injections h-1 for MSFIA and SIA, respectively. These results provide evidence of superior performance of MSFIA over SIA for the determination of chloride. (C) 2002 Elsevier Science B.V. All rights reserved.
Chloride Water Mineral Farm Potentiometry Electrode

"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

"Temporal And Organ-specific Variability Of Selenium In Marine Organisms From The Eastern Coast Of India"
Adv. Environ. Res. 2001 Volume 5, Issue 2 Pages 167-174
Amit Chatterjee, Badal Bhattacharya and Rajdulal Das

Abstract: Temporal and organ-specific variations of selenium concentration in selected coastal organisms (seagrass, bivalves and fish) were investigated in different biotopes of the deltaic Sundarbans, in the eastern coastal region of India. The bivalves and fish were obtained from local fishermen and were destined for human consumption. The samples were digested with HNO3-H2O2 and selenium was extracted from the aqueous solution with triisooctylamine and stripped with dilute hydrochloric acid. The concentration of selenium was measured by hydride generation-atomic absorption spectrometry. The results obtained were verified using inductively coupled plasma-mass spectrometric and fluorometric methods. The mean selenium concentration found in the various species ranged from 0.05 to 3.94 µg g-1 (dry wt.). It was observed that bivalves accumulated more selenium compared to fish and seagrass. The sequence of selenium levels found was, bivalves > fish > seagrass. In seagrass, the selenium concentration was higher in the roots (0.21±0.03 µg g-1; dry wt.) than the stems (0.17±0.02 µg g-1; dry wt.) and the leaves (0.11±0.01 µg g-1; dry wt.). But, in bivalves, the maximum concentration of selenium was found in the gill (3.94±0.11 µg g-1; dry wt.). The results of the analysis of variance indicated that significant differences in Se concentration were evident between seasons and organs in these species. The variations in uptake of selenium may be due to different metabolic requirements for selenium among the three species, variations in food and differences in interspecies retention and elimination mechanisms.
Selenium NIST 1566 NIST 1571 NRCC DORM-2 Spectrophotometry

"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

"Development Of Isotope Dilution Cold Vapor Inductively Coupled Plasma Mass Spectrometry And Its Application To The Certification Of Mercury In NIST Standard Reference Materials"
Anal. Chem. 2001 Volume 73, Issue 10 Pages 2190-2199
S. J. Christopher, S. E. Long, M. S. Rearick, and J. D. Fassett

Abstract: An isotope dilution cold vapor inductively coupled plasma mass spectrometry (ID-CV-ICPMS) method featuring gaseous introduction of mercury via tin chloride reduction has been developed and applied to the quantification and certification of mercury in various NIST standard reference materials: SRM 966 Toxic Metals in Bovine Blood (30 ng mL-1); SRM 1641d Mercury in Water (1.6 µg mL-1); and SRM 1946 Lake Superior Fish Tissue (436 ng g-1). Complementary mercury data were generated for SRMs and NIST quality control standards using cold vapor atomic absorption spectroscopy (CVAAS). Certification results for the determination of mercury in SRM 1641d using two independent methods (ID-CV-ICPMS and CVAAS) showed a degree of agreement of 0.3% between the methods. Gaseous introduction of mercury into the ICPMS resulted in a single isotope sensitivity of 2 x 10(6) counts s-1 ng-1 g for Hg-201 and significantly reduced the memory and washout effects traditionally encountered in solution nebulization ICPMS. Figures of merit for isotope ratio accuracy and precision were evaluated at dwell times of 10, 20, 40, 80, and 160 ms using SRM 3133 Mercury Spectrometric Solution. The optimum dwell time of 80 ms yielded a measured Hg-201/Hg-202 isotope ratio within 0.13% of the theoretical natural value and a measurement precision of 0.34%, on the basis of three replicate injections of SRM 3133.
Mercury NIST 3133 NIST 1641d NIST 966 NIST 1946 Mass spectrometry Mass spectrometry Spectrophotometry

"Determination Of Acid Phosphatase Activity In A Double Injection Flow System With Electrochemical Detection"
Anal. Chim. Acta 2000 Volume 406, Issue 2 Pages 225-232
J. Casta&ntilde;&oacute;n-Fern&aacute;ndez, M. T. Fern&aacute;ndez-Abedul and A. Costa-Garc&iacute;a

Abstract: An enzyme assay for the measurement of total and prostatic acid phosphatase activity by flow injection analysis with electrochemical detection has been developed. The substrate (α-naphthyl phosphate) and enzyme are simultaneously injected to the system by means of a double injection valve. The α-naphtol produced after stopping the flow is amperometrically quantified. The calibration curve is linear from 0.01 to 1.3 u/L with a limit of detection of 0.006 u/L. Results were compared with that obtained spectrophotometrically.
Acid phosphatase Blood Serum Amperometry Electrode

"Kinetic Determination Of Acid Phosphatase Activity By Double Injection Flow Analysis With Electrochemical Detection"
Anal. Chim. Acta 2000 Volume 413, Issue 1-2 Pages 103-108
J. Casta&ntilde;&oacute;n-Fern&aacute;ndez, M. T. Fern&aacute;ndez-Abedul and A. Costa-Garc&iacute;a

Abstract: A two-points kinetic procedure has led to an enzyme assay for the measurement of total and prostatic acid phosphatase (PAP) activity by flow injection analysis with electrochemical detection. A double injection valve is employed for the simultaneous injection of the substrate (α-naphthyl phosphate) and enzyme. Successive injections are directed into different reaction coils for amperometric measurement of the α-naphthol produced at different times. Total and prostatic activity is determined in control sera and results were compared with those obtained spectrophotometrically.
Acid phosphatase Blood Serum Amperometry Electrode

"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

"Analytical Options For Control Of Acids And Bases In Hydrometallurgical Processes"
Process Control Qual. 1999 Volume 11, Issue 4 Pages 289-300
Fernando Albert&uacute;s, Isel Cort&eacute;s, L.-G. Danielsson and Folke Ingman

Abstract: The most common procedures for the determination of acids and bases in hydrometallurgical process liquors are reviewed and compared. Automated batch titrations, performed by stepwise addition of titrant and using Gran plots for evaluation are reliable but slow compared to flow techniques. Continuous flow titrations are grouped into three classes: Flow Injection Titration, Single Point Flow Injection Titration, and Triangle-programmed Flow Titrations. Furthermore, Sequential Injection Analysis is also considered for process applications. Each one of these methods has advantages and drawbacks. An overview of the most common application problems, and the way they are solved with each methodology, is given. The analytical characteristics of the described procedures are given as well as a guide for the choice of technique for a given application.
Industrial

"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

"Flow Injection Analysis Of Kjeldahl Nitrogen In Milk And Dairy Products By Potentiometric Detection"
Anal. Chim. Acta 1999 Volume 385, Issue 1-3 Pages 437-441
Jos&eacute; F. C. C. Lima, Cristina Delerue-Matos and M. Carmo Vaz

Abstract: A flow injection analysis (FIA) system with a potentiometric tubular detector and a gas diffusion unit was developed for the determination of Kjeldahl nitrogen in milk and dairy products. The samples were digested by the Kjeldahl method and afterwards injected into the RA system without prior treatment. NaOH solution was introduced into the system to promote the conversion of ammonium ions to ammonia gas. The gas produced diffused through a gas-permeable membrane towards an acceptor channel (Tris-HCl, pH=7.5). When in contact with this solution, ammonia gas was reconverted to ammonium cation and carried to a tubular electrode sensitive to this species. Therefore, a PVC tubular ammonium ion-selective electrode was prepared without inner reference solution and with the sensor system based on nonactine and monactine dissolved in Tris-(2-ethylhexyl) phosphate. The results obtained with the developed FIA system were in good agreement with those of the reference method the relative deviations being less than 4%. Reproducibility of the method was assessed by the relative standard deviation, which was always less than 0.5% for 12 consecutive injections of sample digests. A sampling rate of 100 samples h-1 was obtained.
Ammonia Dairy Products Potentiometry Electrode

"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

"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

"Development Of Analytical Systems For The Simultaneous Determination Of The Speciation Of Arsenic [As(III), Methylarsonic Acid, Dimethylarsinic Acid, As(V)] And Selenium [Se(IV), Se(VI)]"
Anal. Chim. Acta 2000 Volume 413, Issue 1-2 Pages 13-23
Ildik&oacute; Ipolyi and P&eacute;ter Fodor

Abstract: The simultaneous determination of arsenic (As(III), MMAs, DMAs, As(V)) and selenium (Se(IV), Se(VI)) species has been carried out by three instrument combinations. High performance liquid chromatography (HPLC) is coupled with two independent atomic fluorescence spectrometers (AFS) supplied with boosted discharge hollow cathode lamp (BD HCL) by high efficiency sample introduction systems. The efficiency of ultrasonic nebulisation (USN), hydraulic high pressure nebulisation (HHPN) and hydride generation (HG) was compared. The separation of the six species in one system is achieved by gradient elution programs. The HPLC-HG-AFS system provides the best detection limits, but it is not suitable for the direct determination of Se(VI). The HPLC-HG-AFS system was applied for the measurement of arsenic contaminated natural ground water samples. Absolute detection limits of 1.0, 0.5, 1.0, 0.3 and 0.7 pg for Se(IV), As(III), DMAs, MMAs and As(V), respectively, were obtained for a 100 µl injection volume using the HPLC-HG-AFS system.
Arsenic(3+) Monomethylarsine Dimethylarsenic Arsenic(5+) Selenium(IV) Selenium(VI) Ground Fluorescence HPLC

"Comparison Of Spectrophotometric And Potentiometric Detection For The Determination Of Water Using Karl Fischer Method Under Flow Injection Analysis Conditions"
Anal. Chim. Acta 2000 Volume 420, Issue 1 Pages 133-142
Nathalie Dantan, Steffen Kr&ouml;ning, Wolfgang Frenzel and Stephan K&uuml;ppers

Abstract: Flow injection procedures for the determination of water in methanol using Karl Fischer method are presented. Both spectrophotometric and potentiometric detection systems were investigated and critically compared with respect to their performance characteristics. A novel tubular differential potentiometric flow through cell has been developed. Using spectrophotometric detection the determination of water at a sampling frequency of about 120 h-1 is possible in the concentration range 0.01-1%. Precision is better than 3% RSD over the entire concentration range. The detectability of the method is severely affected by the presence of water traces in the carrier solvent but with appropriate preventive measures, concentrations as low as 0.002% are accessible. The specifications of the potentiometric variant compare well with the spectrophotometric detection method, yet the former offers slightly better precision but suffers from reduced linear range, Automation of the two methods has been realised and the applicability for on-line monitoring purposes are outlined. Particular emphasis is paid to the calibration problematic. Modified reverse FIA has also been applied and shown to be a simple and reliable way of detecting deviations from nominal values as required in several process control situations.
Water Organic compound Spectrophotometry Potentiometry Karl Fischer analysis

"Use Of The Anion-exchange Resin Amberlite IRA-93 For The Separation Of Arsenite And Arsenate In Aqueous Samples"
Acta Hydrochim. Hydrobiol. 2000 Volume 28, Issue 1 Pages 41-46
M. Bissen, T. Gremm, &Uuml;. K&ouml;kl&uuml;, F. H. Frimmel

Abstract: The method described uses the separation of As(III) and As(V) species in aqueous samples by means of the anion-exchange resin Amberlite IRA-93. The samples were acidified using acetic acid and passed through a glass column filled with pre-treated Amberlite IRA-93 resin. As(III) was poorly adsorbed on the anionic exchanger material, whereas As(V) was retained. The arsenic concentration was measured in the column effluent by graphite furnace AAS (GF-AAS). The retained As(V) was eluted from the column using 1 M NaOH. Prior to the determination of the As(V) concentration in the NaOH eluate, the eluate was passed through a glass column filled with a cation-exchange resin (Amberlite 200) to remove sodium ions and minimize the Na+ interference with the AAS determination. After calibration the method was applied to the separation of As(III) and As(V) species in two aqueous extracts of arsenic contaminated soils. The results were compared with those obtained from an on-line separation and determination of As(III) and As(V) in the aqueous soil extracts using a state of the art HPLC-ICP-MS system.
Arsenate ion Arsenite Leachates Spectrophotometry Spectrophotometry Ion exchange

"Direct Parallel Flow Injection Multichannel Spectrophotometric Determination Of Olive Oil Iodine Value"
Anal. Chim. Acta 2000 Volume 405, Issue 1-2 Pages 239-245
Nikolaos S. Thomaidis and Constantinos A. Georgiou

Abstract: An automated parallel flow injection (PA-FI) spectrophotometric method for the determination of olive oil iodine value (IV, g I-2/100 g of oil) is presented. A home made PA-FI analyzer, incorporating 10 incubation coils and using flow reversals, achieves a sampling rate of 60 samples per hour, while each sample is incubated for 10 min. Olive oil samples are diluted 1 : 50 in n-propanol and a 60 µl aliquot is injected into a 6.0 x 10^-3 M IBr carrier solution prepared in acetic acid. The injected sample is mixed with the reagent while flowing through the detector and then diverted to the incubation coil, where it is incubated for 10 min. The sample is then aspirated for measurement by flow reversal. The IBr absorbance in the carrier stream is monitored continuously at 392 nm. Injected samples consume IBr, resulting in negative absorbance peaks. The linear range was 9-125 IV, that is suitable for the analysis of edible oils. The method was applied to the determination of TV of 25 olive oil samples. Results obtained by the proposed method compare well (0.1-1.7% relative difference, mean 0.7%) with those obtained by the official AOAC method, which is time consuming and uses large amounts of organic solvents. The relative standard deviation ranged from 0.4 to 1.1% (n = 6). The new PA-FI technique minimizes reagent and solvent consumption (3.1 mi of acetic acid per sample) and allows automation of methods that require long incubation times without loss of sampling rate. The method is environmental friendly since it eliminates the use of chlorinated solvents.
Iodine Food 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

"A Collaborative Study For The Determination Of Mercury In Glass Packaging By Cold Vapor Atomic Absorption Spectrometry - A Report Of ICG/TC2, Chemical Durability And Analysis"
Glass Technol. 2001 Volume 42, Issue 1 Pages 24-29
E.Guadagnino, P.Sundberg and H.J.Heinrich

Abstract: Within the frame of the requirements set out by the Packaging Directive 62/94, this paper recommends a method for the determination of mercury by cold vapor atomic absorption spectrometry (CVAAS). The study consisted of two ports: (i) a recovery study.; (ii) a collaborative intercomparison carried out on an experimental glass incorporating Hg in traces. During the recovery study the decomposition solution of a Hg free container glass was spiked with known amounts of Hg which were fully recovered by CVAAS. No significant interferences were found from other hydride forming elements. An intercomparison among ten laboratories carried out on a glass incorporating Hg traces showed an acceptable reproducibility (CV 8.9%) at a mean concentration level of 1.10 mg/kg. The determination limit was estimated as 0.1 mg Hg/kg of glass. Inductively coupled plasma optical emission spectrometry (ICP-OES), used as an alternative to CVAAS, showed a limit of determination of 7.2 mg/kg, which was considered quite inadequate, with respect to the average mean value of Hg possibly present in packaging.
Mercury Commercial product Spectrophotometry

"Determination Of Metformin In Pharmaceutical Preparations Using Potentiometry, Spectrofluorimetry And UV-visible Spectrophotometry"
Anal. Chim. Acta 1999 Volume 378, Issue 1-3 Pages 299-311
Saad S. M. Hassan, Wagiha H. Mahmoud, Mohamed A. F. Elmosallamy and Abdel Hammeed M. Othman

Abstract: New, simple and convenient potentiometric, spectrofluorimetric and spectrophotometric methods are described for the determination of metformin in pharmaceutical preparations. The potentiometric technique is based on preparation of PVC membrane sensors incorporating metformin-reineckate, and metformin-tungstosilicate ion-pairs as electroactive species with dioctylphthalate and o-nitrophenyloctylether as plasticizers, respectively. A membrane consisting of carboxylated PVC plasticized with dibutylsebacate is also prepared and tested. These sensors give rapid Nernstian response for 10^-1 - 10^-5 M metformin at pH range 5-11. The metformin-tungstosilicate based sensor is used in a flow-through sandwich cell for flow injection potentiometric determination of metformin. Graphite sensors coated or doped with metformin-tungstosilicate-PVC, Cu-diethyldithiocarbamate and Ni-diethyldithiocarbamate are also prepared and used for monitoring the titration of the drug with tetraphenyl berate (TPB-), Cu2+ and Ni2+ ions, respectively. The spectrofluorimetric method depends on the reaction of metformin with chrysenequinone in alkaline medium to give a Schiffs base, which upon hydrolysis gives the free base. The latter in the presence of l-naphthol gives a fluorescent product with excitation and emission maxima at 450 and 520 nm, respectively. The fluorescence-concentration relationship is linear over the range 20-200 µg mL-1 metformin. The proposed spectrophotometric technique involves reaction of metformin with Cu2+ in basic medium to form a Cu-metformin complex. The complex is dissolved in cyclohexylamine and its maximum absorption at 540 nm is measured. Beers law is obeyed over the range 0.5-2 mg mL-1 metformin. Various cations, some nitrogenous compounds or drug excipients cause no interferences. Results obtained by these techniques are comparable and compare favorably with data obtained using the British Pharmacopoeia method.
Metformin Pharmaceutical Potentiometry Electrode Fluorescence Spectrophotometry

"Flow Injection And Stopped-flow Completely Continuous Flow Spectrophotometric Determinations Of Aniline And Cyclohexylamine"
Anal. Chim. Acta 1999 Volume 396, Issue 2-3 Pages 151-159
Javier Saurina and Santiago Hern&aacute;ndez-Cassou

Abstract: The sequential determination of aniline and cyclohexylamine using flow injection analysis and their simultaneous kinetic determination with a stopped-flow completely continuous flow (stopped-flow CCF) system are proposed. Both methods are based on the reaction of these amines with 1,2-naphthoquinone-4-sulfonate (NQS) for two measurement conditions: (i) under selectivity conditions for one of the analytes (aniline) and (ii) under non-selective reaction conditions in which both amines react simultaneously with NQS. The pH enabled both amines to be distinguished in the flow injection method, while the difference in reaction rates of the two derivatives was exploited advantageously in the stopped-flow method. Therefore, aniline was directly quantified under selective conditions, whereas the determination of cyclohexylamine involved the calculation of its net analyte response. The figures of merit (sensitivity, linear range, detection limit and precision) of both methods were established. Several mixtures of aniline and cyclohexylamine were quantified using both flow injection and kinetic methods. The overall prediction errors of the flow injection method were 1.6% and 4.9% for aniline and cyclohexylamine, respectively. The accuracy of the kinetic procedure in the analysis of synthetic samples was 2.1% and 5.4% for aniline and cyclohexylamine, respectively. The method was applied to the determination of aniline and:cyclohexylamine in commercial sweeteners. A good agreement between the proposed and the standard methods was found.
Aniline Cyclohexylamine Commercial product Spectrophotometry

"Flow Injection And Stopped-flow Completely Continuous Flow Spectrophotometric Determinations Of Aniline And Cyclohexylamine"
Anal. Chim. Acta 1999 Volume 396, Issue 2-3 Pages 151-159
Javier Saurina and Santiago Hern&aacute;ndez-Cassou

Abstract: The sequential determination of aniline and cyclohexylamine using flow injection analysis and their simultaneous kinetic determination with a stopped-flow completely continuous flow (stopped-flow CCF) system are proposed. Both methods are based on the reaction of these amines with 1,2-naphthoquinone-4-sulfonate (NQS) for two measurement conditions: (i) under selectivity conditions for one of the analytes (aniline) and (ii) under non-selective reaction conditions in which both amines react simultaneously with NQS. The pH enabled both amines to be distinguished in the flow injection method, while the difference in reaction rates of the two derivatives was exploited advantageously in the stopped-flow method. Therefore, aniline was directly quantified under selective conditions, whereas the determination of cyclohexylamine involved the calculation of its net analyte response. The figures of merit (sensitivity, linear range, detection limit and precision) of both methods were established. Several mixtures of aniline and cyclohexylamine were quantified using both flow injection and kinetic methods. The overall prediction errors of the flow injection method were 1.6% and 4.9% for aniline and cyclohexylamine, respectively. The accuracy of the kinetic procedure in the analysis of synthetic samples was 2.1% and 5.4% for aniline and cyclohexylamine, respectively. The method was applied to the determination of aniline and:cyclohexylamine in commercial sweeteners. A good agreement between the proposed and the standard methods was found.
Aniline Cyclohexylamine Commercial product Spectrophotometry

"Flow Electrochemical Determination Of Ascorbic Acid In Real Samples Using A Glassy Carbon Electrode Modified With A Cellulose Acetate Film Bearing 2,6-dichlorophenolindophenol"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 113-121
Ageliki B. Florou, Mamas I. Prodromidis, Miltiades I. Karayannis and Stella M. Tzouwara-Karayanni

Abstract: An ascorbate sensor based on a glassy carbon electrode modified with a cellulose acetate polymeric film bearing 2,6-dichlorophenolindophenol (CA/DCPI-CME) was constructed. The overall reaction obeys a catalytic regeneration mechanism (EC mechanism) and the electrochemical rate constant kf for the electrocatalytic oxidation of ascorbic acid was evaluated. The modified electrodes were mounted in a flow injection (FI) manifold, poised at +100 mV versus Ag/AgCl/3 M KCl at pH 6.5 and utilized for the determination of ascorbic acid in beverages and pharmaceuticals. Good correlation with a reference method was attained. Interferents of various molecular sizes were tested. Calibration graphs were linear over the range 0.02-1 and 0.1-6 mM ascorbic acid for CA/DCPI sensors hydrolyzed in KOH and ZnCl2 solution, respectively. The throughput was 25 samples per hour and the CV was for a 0.4 mM ascorbic acid solution 0.75 (n=14) and 1.2% (n=10) for CA/DCPI sensors hydrolyzed in KOH and ZnCl2 solution, respectively. The recovery was 92-110%. The sensors showed very good repeatability and operational stability.
Ascorbic acid Beverage Pharmaceutical Electrode Electrode

"Simultaneous Kinetic Determination Of Cobalt, Nickel And Iron By Coupling Stopped-flow Techniques And Charge Coupled Device Detection"
Anal. Chim. Acta 2000 Volume 423, Issue 2 Pages 277-286
M. I. Karayannis and I. A. Pettas

Abstract: Two kinetic approaches were applied for the simultaneous determination of cobalt, nickel, and iron with multiple linear regression (MLR) method, using the entire kinetic curves or the initial rates of the reaction. The predictive ability of MLR method is based on the slight kinetic differences of these metals which occur at a great number of wavelengths when they react with xylenol orange as a common ligand. The reactions were monitored using a charge coupled device (CCD) UV-VIS spectrophotometer attached to a stopped-flow system. This instrumentation allowed to obtain kinetic data at a maximum of 2048 wavelengths simultaneously. The method was successfully applied to the simultaneous determination of these metals in alloys and the results obtained from the two kinetic approaches were compared.
Cobalt Nickel Iron Alloy Spectrophotometry

"Determination Of Phenol In Water By Pervaporation-flow Injection Analysis"
Anal. Chim. Acta 2000 Volume 419, Issue 1 Pages 9-16
Sami Y. Sheikheldin, Terence J. Cardwell, Robert W. Cattrall, Maria D. Luque de Castro and Spas D. Kolev

Abstract: A pervaporation-flow injection method for the determination of phenol in aqueous samples is described. The method involves sample injection into a concentrated sodium chloride (25 wt.%) donor stream at pH 2 and stopping the flow of the acceptor stream containing 0.1 M KNO3 and 0.01 M NaOH in the acceptor chamber of the pervaporation unit for 12 min. This period allows the completion of phenol transfer from the headspace of the donor chamber of the pervaporation unit through the membrane into the static solution in the acceptor chamber. After restarting the flow through the acceptor chamber the phenol concentration is detected amperometrically at a glassy carbon electrode set at +0.6 V. At 20°C the linear detection range was found to be 1-50 mg L-1 with RSD varying between 1 and 4% for n=3. The detection Limit and sample throughput were determined as 0.9 mg L-1 and 5 hr-1, respectively. Excellent agreement with the standard 4-aminoantipyrine (4-AAP) method was observed when validating the method with lake samples containing suspension and spiked with phenol.
Phenol Lake Amperometry Electrode

"HPLC-HG-AAS And HPLC-ICP-MS For Speciation Of Arsenic And Antimony In Biomonitoring"
Am. Lab. News 2002 Volume 34, Issue 6 Pages 10-14
Krachler, M., Falk, K., and Emons, H.

Abstract: This article presents a comparison of the extractability of As and Sb species from biological matrices as well as two different detection principles that have been coupled on-line with HPLC separation of As and Sb species for the purpose of determining speciation patterns in specimens arising from environmental and human biomonitoring.
Arsenic Antimony Biological HPLC

"Sequential Injection Fourier Transform Infrared Spectroscopy For The Simultaneous Determination Of Organic Acids And Sugars In Soft Drinks Employing Automated Solid Phase Extraction"
Anal. Chim. Acta 2000 Volume 422, Issue 1 Pages 63-69
Hai LeThanh and Bernhard Lendl

Abstract: A fully automated method for the rapid determination of organic acids (citric-, malic- and tartaric acid) and sugars (glucose, fructose, and sucrose) in soft drinks by sequential injection Fourier transform infrared (FTIR) spectroscopy is presented. A convective interaction media (CIM) disc carrying quaternary amino moieties was added as a solid phase extraction column to the flow system. Upon injection of a sample the organic acids were completely retained on the CIM disc whereas sugars passed to the flow cell. The organic acids were subsequently eluted by injection of an alkaline (pH 8.5) 1 M sodium chloride solution and recorded in their fully deprotonated form as a second flow injection peak. In both cases, the FTIR spectra corresponding to the peak maxima were selected for data evaluation. Two partial least squares models, one for sugars and the other for organic acids, were constructed based on the analysis of standards containing all six analytes. The developed method was applied to natural samples yielding results which were in good agreement with those obtained by an external reference method (enzymatic test kits). Deviations in the results were 3.4. and 4.1% for citric and malic acid and ranged from 4.7-5.1% for the sugars. The developed method is characterized by its short analysis time, experimental simplicity and its potential applications in routine analysis and process control.
Citric acid l-Malic acid Tartaric acid Glucose Fructose Sucrose Soft drink Spectrophotometry

"Sequential Determination Of Total And Volatile Acidity In Wines Based On A Flow Injection-pervaporation Approach"
Anal. Chim. Acta 1999 Volume 381, Issue 1 Pages 23-28
E. Mataix and M. D. Luque de Castro

Abstract: A method for the sequential determination of the total and volatile acidity in wines based on the use of a pervaporator inserted in a continuous manifold is reported. The chemical principle is the color change of bromothymol blue in the presence of the analytes and monitoring of the absorbance at 616 nm. The simultaneous injection of two sample aliquots into two channels allows one of the plugs to be driven to the pervaporator and the other directly to the photometric detector after merging with an indicator stream. After pervaporation, the acceptor stream, also containing the indicator, is led to the photometric detector for monitoring. The detection limits and relative standard deviation are 10 meg L-1, 1.0%, and 0.02 g L-1, 5.0%, for total and volatile acidity, respectively. The method has been applied to white and red wines from different origins and the results obtained an in good agreement with those of the standard method used in Spanish wine industries.
Acidity Wine Red Wine White Spectrophotometry

"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

"Kinetic-turbidimetric Determination Of Phytic Acid By Sequential Injection Analysis"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 9-16
J. G. March, B. M. Simonet and F. Grases

Abstract: A sequential injection analysis method with kinetic-turbidimetric detection for the determination of phytic acid is described. The method is based on the diminution of the calcium oxalate crystallisation reaction rate in the presence of phytic acid. Such a crystallisation rate has been evaluated from the increase of turbidity with time. A linear calibration graph was obtained from 0.05 to 0.6 mg L-1 phytic acid and the relative standard deviation (n=5) was 2.0% for a standard of 0.25 mg L-1 phytic acid. The method was applied to the determination of phytic acid in food samples (after purification by anion exchange chromatography) and compared with an indirect extraction-spectrophotometric determination based on the hydrolysis of phytic acid and determination of released phosphate.
Phytic acid Food Turbidimetry

"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

"Molecularly Imprinted Ion Exchange Resin For Purification, Preconcentration And Determination Of UO22+ By Spectrophotometry And Plasma Spectrometry"
Anal. Chim. Acta 1999 Volume 397, Issue 1-3 Pages 173-181
Sue Y. Bae, Glen L. Southard and George M. Murray

Abstract: A new ion exchange resin based on a UO22+ imprinted polymer was used for the removal and concentration of UO22+ from aqueous solution prior to spectroscopic determination. The imprinted resin performance is compared with results obtained using Chelex-100 ion exchange resin. The UO22+ ion imprinted resin, being more selective towards UO22+ ion, provides a fast and virtually interference-free pre-concentration procedure. The separation provides for the elimination of interferences in photometry and plasma spectroscopy, improves accuracy and lowers limits of detection. The performance of the imprinted resin allows for the development of a field test kit for the determination of UO22+ in environmental samples based on colorimetric analysis. A mini-column permitted large enrichment factors to be attained, provided rapid processing of large volumes and quantitative recovery of UO22+ With an eluent suitable for photometric analysis.
Uranyl ion Water Spectrophotometry Spectrophotometry Ion exchange

"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 Salicylate In Blood Serum Using An Amperometric Biosensor Based On Salicylate Hydroxylase Immobilized In A Polypyrrole-glutaraldehyde Matrix"
Talanta 2000 Volume 51, Issue 3 Pages 547-557
La&eacute;rcio Rover J&uacute;nior, Graciliano de Oliveira Neto, Jo&atilde;o Roberto Fernandes and Lauro Tatsuo Kubota

Abstract: The use of an amperometric biosensor for the salicylate determination in blood serum is described. The biosensor is based on salicylate hydroxylase (EC 1.14.13.1) electropolymerized onto a glassy carbon-working electrode with polypyrrole and glutaraldehyde, to improve the biosensor lifetime. The hexacyanoferrate: (II) was also incorporated to work as a redox mediator to minimize possible interferences. The salicylate is enzymatically converted to catechol, which is monitored amperometrically by its electrooxidation at + 0.170 V versus SCE (saturated calomel electrode). Salicylate determination was carried out maintaining the ratio between β-NADH and salicylate at 4:1 (30°C). The amperometric response of the biosensor was linearly proportional to the salicylate concentration between 2.3 x 10^-6 and 1.4 x 10^-5 mol L-1, in 0.1 mol L-1 phosphate buffer (pH 7.8), containing 0.1 mol L-1 KCl and 5.0 x 10^-4 mol L-1 Na(2)H(2)EDTA, as supporting electrolyte. The recovery studies, in the presence of several interfering compounds, showed recoveries between 96.4 and 104.8%. The useful lifetime of the biosensor in the concentration range evaluated was at least 40 days, in continuous use. Blood serum samples analyzed by this biosensor showed a good correlation compared to the spectrophotometric method (Trinder) used as reference, presenting relative deviations lower than 7.0%.
Salicylate Blood Serum Amperometry Sensor Electrode

"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

"Flow Injection Speciation Of Aluminum"
Water Res. 2000 Volume 34, Issue 2 Pages 359-365
Krystyna Pyrzynska, Seref Gu&ccedil;er and Ewa Bulska

Abstract: This review discusses recent trends in chemical speciation of aluminum in natural waters. Several difficulties which arise from the complexity of aluminum species present in natural samples as well as its participation in dynamic equilibrium are highlights. Taking this into account various approaches for speciation of Al described in the literature are critically evaluated. The strategy of fractionation procedures based on the rate of reaction, sorption efficiency, chromatographic behavior of the aluminum compounds or size of the molecules are described in the paper. Besides conventional procedures involving various measuring and separation techniques, a special emphasis is focused on mechanised flow injection methodologies. This was found to be very important in order to ensure precise control of the reaction time. which is essential in aluminum species equilibrium system. The analytical performance of several separation procedures based on flow injection approaches as well as the detection methods are discussed and compared.
Aluminum, labile Aluminum, reactive Aluminum, bound Environmental HPLC 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

"Determination Of Ethanol In Wines By Flow Injection Spectrophotometry Using Gas-diffusion And An Immobilized Enzyme Reactor"
Am. J. Enol. Vitic. 1999 Volume 50, Issue 3 Pages 259-263
Ant&oacute;nio O. S. S. Rangel and Ildik&oacute; V. T&oacute;th

Abstract: A flow injection analysis (FIA) system for the spectrophotometric determination of ethanol in wines using an immobilized alcohol dehydrogenase reactor was developed. A gas diffusion unit was used to achieve a large dilution and to separate ethanol from the matrix. This way, the contact of the sample with the reactor was avoided and possible interferences in the spectrophotometric measurements were significantly reduced. The alcohol dehydrogenase enzyme was immobilized on alkylaminated controlled pore glass, and the consumption of the NAD cofactor was minimized (0.6 µmol per assay) by using the merging zone technique. The detection limit was 0.4% (v/v). Good precision was achieved, with relative standard deviations less than 2.2% (n = 9). For 20 samples of different types of table and Port wines, the results showed good agreement with the OIV usual procedure, the relative deviation being less than 4.4%. Thirty determinations per hour can be carried out within the ethanol concentration range of 5% to 25% (v/v), without any sample pretreatment.
Ethanol Port Spectrophotometry

"Multisyringe Flow System: Determination Of Sulfur Dioxide In Wines"
Analyst 2000 Volume 125, Issue 8 Pages 1501-1505
Marcela A. Segundo, Ant&oacute;nio O. S. S. Rangel, Andreu Cladera and V&iacute;ctor Cerd&agrave;

Abstract: A multisyringe flow system for the spectrophotometric determination of sulfur dioxide in wines is described. The methodology is based on the well-known reaction among SO2, formaldehyde and pararosaniline. The proposed manifold also includes a gas diffusion unit in order to prevent the color interference of red wines in the spectrophotometric measurement. The proposed method was successfully applied to the determination of free SO2 (2-75 mg l-1) and total SO2 (10-250 mg l-1) in wines, just by changing a few operating parameters in the controlling software. A sampling-rate of 25-30 samples per hour was achieved with good repeatability for 10 consecutive injections of wine samples (RSD < 3.2%). The results obtained from 10 wine samples for each determination were statistically comparable to those obtained by the recommended procedure.
Sulfur dioxide Wine Red Spectrophotometry

"Enzymatic Determination Of Ethanol And Glycerol By Flow Injection Parallel Multi-site Detection"
Anal. Chim. Acta 2000 Volume 416, Issue 2 Pages 205-210
Ant&oacute;nio O. S. S. Rangel and Ildik&oacute; V. T&oacute;th

Abstract: A flow injection method was developed for the sequential enzymatic determination of ethanol and glycerol in wines, using immobilized ethanol dehydrogenase and glycerol dehydrogenase, respectively. The enzymes were immobilized separately on alkylaminated controlled pore glass. A multi-site spectrophotometric detection system was used in parallel configuration to monitor the absorbance change in the two independent analytical channels. A 50-fold dilution of the samples was necessary before injection. The working range was between 0.05 and 0.5% (v/v) for the ethanol and between 0.03 and 0.3 g L-1 for the glycerol determination, with corresponding detection limits of 2 x 10^-3% (v/v) and 2 x 10^-3 g L-1. Relative standard deviations (RSD) (n=9) lower than 2.3% for the ethanol and 2.1% for the glycerol determination were found. For 13 samples of different types of table and Port wines, the results showed good agreement with the corresponding reference procedures; a two level recovery study also showed good accuracy for the developed methods. The sampling rate was 10 hr-1, corresponding to 20 determinations per hour.
Ethanol Glycerol Port Wine Spectrophotometry

"A Sequential Injection System For The In-line Digestion And Colorimetric Determination Of Phosphorus In Milk"
J. Food Sci. 2002 Volume 67, Issue 9 Pages 3280-3283
M.J. Reis Lima, S.M.V. Fernandes, A.O.S.S. Rangel

Abstract: A sequential injection analysis (SIA) system involving in-line digestion for the determination of total phosphorus in milk is presented. The developed manifold consists mainly of 2 phases: conversion of all forms of phosphorus into orthophosphates by hydrolysis and oxidation catalyzed by UV radiation (necessary for the efficient oxidation of organic phosphates) and spectrophotometric determination of the phosphomolybdenum blue formed. The proposed method was applied to several cow milk samples and the results were in good agreement with those provided by the reference method, with a maximum relative deviation of 5.2%. The detection limit of the method was around 2 mg P/L with a sampling rate of approximately 17 h-1.
Phosphorus Cow Spectrophotometry

"Flow Injection Solid-phase Spectrophotometry For The Determination Of Zinc In Pharmaceutical Preparations"
Anal. Chim. Acta 1999 Volume 383, Issue 3 Pages 309-315
Leonardo S. G. Teixeira, F&aacute;bio R. P. Rocha, Mauro Korn, Boaventura F. Reis, S&eacute;rgio L. C. Ferreira and Antonio C. S. Costa

Abstract: A flow system exploiting solid-phase spectrophotometry is proposed for the determination of zinc in pharmaceutical preparations. The chromogenic reagent 1-(2-tiazolylazo)-2-naphthol (TAN) was immobilized on C-18 bonded silica loaded into a homemade flow cell with 1 mm optical path and 78 mm(2) cross section. The flow cell was designed in such a way that the sensitivity is enhanced and the attenuation of the radiation beam due to scattering and absorption by the solid material is minimized. The flow cell was placed in the spectrophotometer so that the radiation beam was focused on the overall surface containing the adsorbing material. Reagent immobilization was performed online and allowed to work for at least one month. Analyte reaction, retention and detection were performed simultaneously, followed by elution with hydrochloric acid, The apparent molar absorptivity was estimated as 2.02 x 10(5) 1 mol-1 cm-1 and the procedure allowed the determination of zinc in the 0.04-4.0 mg L-1 range with a coefficient of variation of 3.3% (n=10). A sample throughput of 45 determinations per hour and a detection limit of 10 µg L-1 (99.7% confidence level) were achieved. The results agreed at a 95% confidence level with those found by inductively coupled plasma atomic emission spectrometry.
Zinc Pharmaceutical Spectrophotometry

"Monosegmented Flow System Exploiting Multicommutation Applied To Spectrophotometric Determination Of Manganese In Soybean Digests"
Anal. Chim. Acta 1999 Volume 386, Issue 1-2 Pages 129-135
Marisa Smiderle, Boaventura F. Reis and F&aacute;bio R. P. Rocha

Abstract: A flow system combining binary sampling and monosegmented flow implemented by multicommutation was developed to improve sensitivity and sampling rate of spectrophotometric methods based on slow chemical reactions. The flow network was assembled from a set of computer controlled three-way solenoid valves. The spectrophotometric method was based on manganese (II) oxidation by periodate in phosphoric acid medium to form the permanganate anion. The reaction is relatively slow and at 47degC a sample residence time of ~5 min is necessary to attain equilibrium conditions. However, by exploiting binary sampling and monosegmented flow analysis, quantitative conversion with a sampling rate of 50 determinations per hour was achieved. The procedure was applied to Mn determination in soybean digests, showing as profitable features a linear response for sample concentrations ranging from 2.50 to 40.00 mg L-1 Mn2+, a relative standard deviation of 0.27% (n=9) for a sample solution containing 17.1 mg L-1 Mn2+, a low reagent consumption (30 mg NaIO4 per determination) and a detection limit of 1.2 mg L-1 (99.7% confidence level). Results agreed with those obtained by inductively coupled argon plasma atomic emission spectrometry at 95% confidence level.
Manganese Vegetable Sample preparation Spectrophotometry

"A Flow System Exploiting Multicommutation For Speciation Of Inorganic Nitrogen In Waters"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 227-235
F&aacute;bio R. P. Rocha and Boaventura F. Reis

Abstract: A flow system for the speciation of inorganic nitrogen in waters is described. Multicommutation and binary sampling approaches are exploited to perform the sequential determination of nitrate, nitrite and ammonium without changing the manifold. Gravitational flow of solutions is employed in the sampling steps in order to avoid the effect of pulsation of the peristaltic pump on precision. A homemade photometer based on a dual-color (red/green) LED and a photodiode is employed to detect the reaction products. The repeatability was estimated as 0.32, 0.42 and 0.72% for nitrite, nitrate, and ammonium, respectively. A sampling rate of 60 determinations per hour was attained and the reagent consumption was reduced to 25% (ammonium) and 45% (nitrate and nitrite) relatively to conventional flow injection analysis (FIA) procedures. Detection limits of 5 µg L-1 NO2-, 15 µg L-1 NO3-, and 25 µg L-1 NH4+ were estimated at the 99.7% confidence level. Results for river water samples agreed with those obtained by conventional FIA or ion chromatography at the 95% confidence level.
Nitrate Nitrite Ammonia River Spectrophotometry

"Development Of A Sequential Injection System In The Capillary Format For Determinations Of The IpaC Protein"
Anal. Chim. Acta 2000 Volume 409, Issue 1-2 Pages 3-8
D. M. Spence, E. D. Knoll, B. T. Ruotolo and J. Bjerregaard

Abstract: A sequential injection (SI) system in the capillary format is reported for protein concentration determinations employing sample volumes in the microliter to nanoliter range. By incorporating a programmable syringe pump and computer control over the selection valve and data acquisition system, the invasion plasmid antigen C (IpaC) protein concentration in a purified sample was determined. Results of flow rate, temperature, and injection studies are presented. Replicate measurements of a bovine serum albumin (BSA) standard resulted in a relative standard deviation in peak area of 3.1%. In addition, protein concentrations as low as 5 x 10^-6 M were determined in less than 3 min. This system was subsequently applied to the determination of a real IpaC sample using multiple standard additions. The error in the determination, relative to a spectrophotometric method of determination, was 7.1%. The total sample consumption for the calibration and unknown concentration determination was 60 µl.
Protein, IpaC Blood Serum

"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

"Determination Of Lead By Hydride Generation Inductively Coupled Plasma Mass Spectrometry"
Anal. Chim. Acta 2000 Volume 419, Issue 1 Pages 65-72
Jinxiang Li, Fang Lu, Tomonari Umemura and Kin-ichi Tsunoda

Abstract: A method for the determination of lead by hydride generation inductively coupled plasma mass spectrometry was explored using oxalic acid-ammonium cerium(IV) nitrate-sodium tetrahydroborate as the reaction matrix and a homemade hydride generator. The sensitivity achieved was ~7.5 times higher than that obtained using an ultrasonic nebulizer. The detection limit (3s) and the signal precision (RSD, n=13) were 0.007 µg L-1 and 0.21% for 1 µg L-1 Pb, respectively, Fe(III) or Ni(II) up to 10 mg L-1 did not affect the hydride generation of 1 µg L-1 Pb. Additionally, the present system equipped with an injector valve and a 500 µl sample loop was also operated in the flow injection mode. Because of the short memory effect (typically 25-30 s), six replicate injections of a solution containing 4 µg L-1 Pb were performed within 5 min. The RSD values (n=13) were 0.33 and 1.41% for peak height and area measurements, respectively. The method was applied to the determination of lead in three environmental reference materials involving natural water, plant tissue and pond sediment. Good agreement was obtained between the certified values and the experimental results with the precisions (RSD, n=5) less than 1.0% for both continuous and flow injection modes.
Lead Environmental Pond Plant Mass spectrometry

"Comparison Of Digestion Methods For The Determination Of Selenium In Fish Tissue By Cathodic Stripping Voltammetry"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 97-102
David F. Lambert and Nicholas J. Turoczy

Abstract: A certified reference material (NIST-RM-50 Albacore Tuna) was analyzed for selenium by cathodic stripping voltammetry (CSV), after digestion of the material by a number of methods that avoid the use of perchloric acid. The digestion techniques tested included wet and dry ashing methods, oxygen bomb digestion, ultraviolet (UV) digestion, and methods involving elevated pressure. The only method that reliably produced results that agreed with the certified value for selenium in the reference material was the combination wet/dry ashing method incorporating elevated pressure recommended by the Association of Official Analytical Chemists (AOAC) for determination using hydride generation atomic absorption spectrometry (AAS). Recoveries using the other methods were low and variable, apparently because of incomplete destruction of organic matter and losses caused by volatilisation of selenium.
Selenium Fish Tissue NIST 50 Voltammetry Sample preparation Sample preparation Sample preparation Sample preparation Sample preparation Spectrophotometry

"Determination Of Antimony Species With Fluoride As Modifier And Flow Injection Hydride Generation Inductively-coupled Plasma Emission Spectrometry"
Anal. Chim. Acta 2000 Volume 417, Issue 2 Pages 201-209
Nina Ulrich

Abstract: A new method for the determination of species of antimony(III) [Sb(III)], antimony(v) [Sb(V)] and trimethylstiboxide [TMeSbO] with fluoride as modifier is introduced. A flow injection (FI) system for hydride generation was used in combination with an inductively-coupled plasma atomic emission spectrometer as detector. The pre-reduction was accomplished with potassium iodide dissolved in hydrochloric acid and the reduction with sodium borohydride. The influence of fluoride on the reduction and pre-reduction step was investigated by adding different amounts of sodium fluoride to the solvent stream. At a concentration of 100 mg/l fluoride and 1.2% potassium iodide, the hydride formation of Sb(V) and Sb(III) was suppressed below the detection limit, while TMeSbO showed no signal depression. The use of 100 mg/l fluoride without potassium iodide led to complete signal suppression for Sb(V) with apparently no influence on the signal intensity of Sb(III) and TMeSbO. The concentration of TMeSbO was measured directly, the concentrations of Sb(III) and Sb(V) were calculated on the basis of the three analyzing steps, giving detection limits and relative standard deviations of 1.1 (2.6%), 1.2 (5.3%) and 1.4 µg/l (8.1%), respectively. The method was applied to orange juice samples.
Antimony(3+) Antimony(5+) Trimethylstibine oxide Juice Leachates Spectrophotometry

"Automatic Determination Of Fat In Milk By Use Of A Flow Injection System With A Piezoelectric Detector"
Anal. Chim. Acta 2000 Volume 406, Issue 2 Pages 309-315
Lisbeth Manganiello, Angel R&iacute;os, Miguel Valc&aacute;rcel, Angel Ligero and Teresa Tena

Abstract: A new method for the direct determination of total fat in milk by use of a quartz crystal microbalance was developed. The method is based on a (micro) extraction procedure that is carried out in a flow injection system. Samples are diluted with an ethanol-water mixture and injected into the flow system, where they are mixed with n-hexane in an extraction coil. The analyte is determined in the organic phase. The calibration thus achieved is linear in the range 0.20-0.45% w/v, and the relative standard deviation is ± 3.2% (n = 11; P = 0.05). The throughput is 12 samples per hour. The proposed method was used to determine fat matter in milk samples; the results were found to be competitive with those of official methods for the same purpose.
Fatty acids Cow Microbalance

"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

"On-line Assay Of S-captopril Using An Amperometric Biosensor/sequential Injection System"
Anal. Chim. Acta 2000 Volume 411, Issue 1-2 Pages 51-56
Raluca-Ioana Stefan, Jacobus (Koos) F. van Staden and Hassan Y. Aboul-Enein

Abstract: An automated system for the enantiopurity test of S-captopril based on the concept of sequential injection analysis (SIA) with an amperometric biosensor (based on L-amino acid oxidase (L-AAOD)) as detector is described. The proposed system is fully computerised and is suitable for the on-line monitoring of S-captopril at a sampling rate of 80 samples per hour with an RSD <0.22% in the linear range between 0.05 and 1.50 µmol/l. The detection limit is 16 nmol/l.
Captopril Pharmaceutical Amperometry Sensor

"Flow Injection Spectrophotometric Assay Of α-amylase Activity"
Anal. Chim. Acta 2000 Volume 421, Issue 1 Pages 19-25
J. F. van Staden and L. V. Mulaudzi

Abstract: A spectrophotometric flow injection method for the determination of α-amylase activity is proposed. The method is based on the analysis of the maltose obtained during the hydrolysis of amylose in the presence of α-amylase and relies on the reaction of 3,5 dinitrosalicylic-acid and maltose at boiling temperatures to form a brick red colored complex, monitored spectrophotometrically at 540 nm. The method has proved to be highly sensitive and rapid to allow analysis of 60 samples per hour. The % RSD of this method was found to be <0.5% with the working activity range of 0.005-0.06 FAU. The detection limit was found to be 0.0048 FAU. (FAU: fungal amylase unit; 1 FAU is the amount of the enzyme that hydrolyses 5.26 g of starch per hour. 1 FAU=249.85 SIGMA).
α-Amylase Sorghum Malt Wheat Malt Energy drink Spectrophotometry

"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

"Microwave-assisted Sample Preparation In Sequential Injection: Spectrophotometric Determination Of Magnesium, Calcium And Iron In Food"
Anal. Chim. Acta 2000 Volume 413, Issue 1-2 Pages 41-48
Cl&aacute;udio C. Oliveira, Raquel P. Sartini and Elias Ayres Guidetti Zagatto

Abstract: A sequential injection system for spectrophotometric analysis of foods and similar involving direct sample introduction as a natural suspension or as slurry is proposed. Sample and concentrated nitric acid are sequentially aspirated and directed towards a digestion bomb located inside a microwave oven where sample decomposition takes place. After digestion, aliquots of the processed sample and randomly selected reagents are sequentially aspirated towards the holding coil and pumped towards the detector. As application, magnesium, calcium and iron were determined in milli, soft drinks and similar by using o-cresolphthalein (with or without EGTA addition) and o-phenanthroline as color forming reagents. The system is versatile, and yields reproducible results (RSD <0.04 for 5.0-50.0 mg L-1 Mg, 15.0-150 mg L-1 Ca and 2.0-20.0 mg L-1 Fe) in agreement with flame atomic absorption spectrometry involving the manual sample digestion procedure.
Magnesium Calcium Iron Food Spectrophotometry Sample preparation

"Spectrophotometric Determination Of Total Nitrogen In Plant Materials Using A Flow Injection System With An AgCl(s) Reactor"
Anal. Chim. Acta 2000 Volume 416, Issue 2 Pages 185-190
Josiane M. T. Carneiro, Raquel P. Sartini and Elias A. G. Zagatto

Abstract: An improved flow injection system with an AgCl(s) reactor is proposed for the spectrophotometric determination of total nitrogen in Kjeldahl digests of plant materials. After sample injection, the established sample plug is alkalinised and allowed to flow through the mini-column where Ag+ ions are displaced as the soluble [Ag(NH3)(2)](+) complex. Bromopyrogallol red and o-phenanthroline are then added and a colored ternary complex is formed under neutral conditions. The system is very stable, and baseline drift is usually <0.01 absorbance after 4 h operation periods. Precise results (RSD<2%) are obtained at a rate of 100 h-1. The analytical curve is linear up to 6.00% (w/w) N (dry basis), regression coefficient has been estimated as >0.999 (n=6) and detection limit is 0.2% (w/w) N. Accuracy was confirmed by running standard reference materials and typical samples already assayed by conductimetry.
Nitrogen, total Plant Spectrophotometry

"Fluorimetric Determination Of Dissolved Aluminum In Natural Waters After Liquid-liquid Extraction Into N-hexanol"
Anal. Chim. Acta 2000 Volume 405, Issue 1-2 Pages 31-42
J. Zhang, H. Xu and J. L. Ren

Abstract: A sensitive and selective extraction-fluorimetric method for the determination of trace amount of dissolved aluminum in natural waters is developed in this study. Aluminum-lumogallion complex (Al-LMG) is extracted into n-hexanol, and the fluorescence can be enhanced substantially up to 20-fold. Compared to other publications in the literature, the method reported here is free from matrix effects, and the interference from iron and fluoride has been minimised successfully by Be2+ and o-phenanthroline, respectively. The detection Limit of dissolved Al is 0.25 nM, which is one order of magnitude lower than the traditional fluorescence techniques, with a precision of 5% at an Al level of 40 nM and 6.7% at an Al level of 1.0 nM in routine analyzes. The inter-calibration with electro-thermal atomic absorption spectrometry (ETAAS) technique for a variety of natural water samples shows a difference of 5-10%. The analysis of international SRM 1643C reference material by the method developed here provides a result consistent with the certified value. The successful inter-laboratory calibration practice demonstrates again the merit of present analytical procedure for the determination of Al in environmental and marine sciences.
Aluminum, soluble NIST 1643 Sea Fluorescence

"Determination Of Ofloxacin Using A Chemiluminescence Flow Injection Method"
Anal. Chim. Acta 2000 Volume 416, Issue 2 Pages 227-230
Yi Rao, Yan Tong, Xinrong Zhang, Guoan Luo and Willy R. G. Baeyens

Abstract: A new chemiluminescence (CL) flow injection method was proposed for the determination of ofloxacin in pharmaceuticals in the range 0.04-4 µg mL-1 with a detection limit of 0.016 µg mL-1 and a relative standard derivation (RSD) of 2.2% at 0.4 µg mL-1 (n=10). The method is based on the CL reaction of cerium(IV) with sulfite sensitized by ofloxacin. The established procedure could be applied to the determination of ofloxacin in tablet, capsule and injection in agreement with the results obtained by using reported methods.
Ofloxacin Pharmaceutical Pharmaceutical Pharmaceutical Chemiluminescence

"Flow Injection Chemiluminescence Determination Of Quinine Using On-line Electrogenerated Cobalt(III) As Oxidant"
Talanta 2000 Volume 51, Issue 3 Pages 515-521
Baoxin Li, Zhujun Zhang and Manli Wu

Abstract: A novel chemiluminescence (CL) flow system for the determination of quinine is described. It is based on the direct chemiluminescence reaction of quinine and cobalt(III) in sulfuric acid medium. The unstable Co(III) was on-line electrogenerated by constant-current electrolysis. The chemiluminescence intensity was linear with a quinine concentration in the range of 0.1-100 µg mL-1. The determination limit was 3.3 x 10^-8 g mL-1. The whole process could be completed in 1 min. The proposed method is suitable for automatic and continuous analysis, and has been applied successfully to the analysis of quinine in pharmaceutical preparation.
Quinine Pharmaceutical Chemiluminescence

"Sequential-injection Procedure For Determination Of Iodide In Pharmaceutical And Drinking Water Samples By Catalytic Reaction With Spectrophotometric Detection"
J. AOAC Int. 2001 Volume 84, Issue 2 Pages 337-341
Jos&eacute; Antonio Erustes, Rafel Forteza, and Victor Cerd&agrave;

Abstract: A novel sequential-injection system was developed for determination of iodide at very low concentrations by using a kinetic method. The method is based on the catalytic effect of iodide on the redox reaction between Ce4+ and As3+ first described by Sandell and Kolthoff. The calibration curve is constructed by measuring the decrease of Ce4+ absorbance versus iodide concentration with a delay time of 30 s. The detection limit is 1.5 µg/L, the working temperature is 45°C, and the working range is 0.002-0.5 mg/L. Reasonable agreement was obtained when the method was applied to pharmaceutical and drinking water samples. The method has a sample throughput of approximately 15/h. [Journal Article; In English; United States]
Iodide Pharmaceutical Water 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

"Rapid Determination Of Protein In Plant Material By Flow Injection Spectrophotometry With Trinitrobenzenesulfonic Acid"
Anal. Chim. Acta 1978 Volume 97, Issue 2 Pages 327-333
L. Sodek*, J. Rika and J. W. B. Stewart

Abstract: The rapid determination of protein in plant material based on spectrometric determination of amino acids in protein hydrolyzates with trinitrobenzenesulfonic acid was adapted to flow injection analysis With the manifold described, a routine sampling rate of 120 samples/h is possible, although this, as well as the sensitivity, can easily be varied. The method was calibrated against the Kjeldahl method and a good correlation was obtained between the 2 methods over a wide range of protein values for beans.
Amino Acids Protein Vegetable Spectrophotometry

"Flow Injection Analysis Of Calcium In Serum, Water And Waste Water By Spectrophotometry And By Ion-selective Electrode"
Anal. Chim. Acta 1978 Volume 100, Issue 1 Pages 151-165
E. H. Hansen, J. Rika and Animesh K. Ghose

Abstract: The flow injection technique is a fast, reliable, and sensitive method for the determination of Ca in various aqueous as well as serum samples; spectrophotometric or potentiometric detection can be used. At sampling rates of 100-10 samples/h, with 30 µL sample injections, high reproducibility of measurement and low reagent consumption are achieved in both methods. In the spectrophotometric method (with o-cresolphthalein complexon), the anal. readout is available within 12 s after sample injection at a total reagent consumption of 0.75 mL/anal. The potentiometric measurement of the Ca activity in serum is placed on a reliable basis by alternating measurements of serum samples and aqueous standards without incurring any nonreproducible changes in potential between aqueous and serum solutions This permits the simultaneous determination of pH and pCa, the anal. readout being available within 3 s of sample injection. The good agreement between the results obtained with the flow injection method and those attained by atomic absorption and EDTA titrns. as well as pCa stat-measurements show that the new methods are potentially suitable for routine anal.
Calcium pH Blood Serum Environmental Geological Water Waste Spectrophotometry Electrode Potentiometry

"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

"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

"Comparison Of Atomic Absorption Spectrometric, Spectrophotometric And Fluorimetric Methods For Determination Of Aluminum In Water"
Anal. Chim. Acta 1982 Volume 134, Issue 1 Pages 369-373
R. Playle, J. Gleed, R. Jonasson and J. R. Kramer

Abstract: A standard method involving chelation of lead with ammonium pyrrolidinedithiocarbamate and extraction into methyl isobutyl ketone was investigated as to the effect of the pH of chelation on the absorbance and stability of the extracted lead. The maximum sensitivity to lead occurs at low pH values, but rapid degradation of the absorption also occurs at low pH values. Higher pH values give lower sensitivity, but provide better stability with time.
Aluminum Water Fluorescence Spectrophotometry Spectrophotometry

"Repetitive Enzymatic Determination Of Glucose With Regeneration And Recycling Of Coenzyme And Enzymes"
Anal. Chim. Acta 1983 Volume 153, Issue 1 Pages 181-190
P. Roehrig, C. -M. Wolff and J. P. Schwing

Abstract: A closed-loop flow injection system is described. The carrier stream consisted of 40 mL of 0.1 M phosphate buffer of pH 7.4 that was 2.25 mM in 2-oxoglutarate (I), 25 mM in ammonium acetate and 3.9 mM in NAD+ and contained 10 iu mL-1 of glucose dehydrogenase (II) and 0.2 unit of glutamate dehydrogenase (III) (i.e., the activity that transforms 0.2 µmol min-1 of I into glutamate in the presence of 0.1 mM NADH), and was circulated at 0.14 mL s-1 from a reservoir through two identical spectrored because of the low stability of NO2- in H2SO4. When the electrode was pre-treated anodically at +1.75 V for 5 min with phosphate buffer and the electrode was operated at +1.0 V vs. a SCE, response was rectilinear over several orders of magnitude and the detection limit was 3 ppb.
Glucose Blood Serum Clinical analysis Spectrophotometry

"Determination Of Cadmium In Human Urine By Extraction With Dithizone In A Flow Injection System"
Anal. Chim. Acta 1983 Volume 153, Issue 1 Pages 207-212
J. L. Burguera and M. Burguera

Abstract: Urine (90 µL) is injected into a flowing stream (0.8 mL min-1) of 3 mM hydroxylamine - 5 mM K Na tartrate - 10 mM K4Fe(CN)6 - 10 mM tartaric acid (pH 10.5) that is subsequently mixed with 39 µM-dithizone in CHCl3 (0.8 mL min-1). The mixture is passed to a phase separator (described, with a diagram), and the absorbance of the organic phase is measured at 518 nm. Calibration graphs are rectilinear for up to 12 ng mL-1 of Cd and the limit of detection is ~0.2 ng mL-1. Recoveries of 91 to 113% were obtained and the coefficient of variation (n = 5) for 0.5 to 5 ng mL-1 was 2 or 3%. For 0.7 ng mL-1 of Cd there is no interference from 1 ng mL-1 of Co, Fe, Ni, Pb or Zn. Results agree well with those obtained by AAS
Cadmium Urine Clinical analysis Spectrophotometry Sample preparation

"Determination Of Hydrogen Peroxide For Application In Aerobic Cell Systems Oxygenated Via Hydrogen Peroxide"
Anal. Chim. Acta 1983 Volume 155, Issue 1 Pages 47-56
Hans Lundb&auml;ck and Gillis Johansson, Olle Holst

Abstract: A flow injection method has been developed for monitoring H2O2 during the production of dihydroxyacetone from glycerol with use of immobilized Gluconobacter oxydans. The sample (5 µL) is injected into 0.2 M Na acetate (pH 5) and diluted 100-fold in a dispersion coil, and the H2O2 is determined amperometrically by oxidation at +1.2V (vs. the s.c.e) at a flow-through vitreous-carbon electrode. Calibration graphs were rectilinear for 0.1 to 100 mM H2O2. Potential interference by other sample components (e.g., dihydroxyacetone, glycerol, pyruvaldehyde, glyceraldehyde and succinate) are shown to be negligible under normal process conditions. Results on various samples agreed well with those obtained by flow injection methods based on enzymatic spectrometry (Olsson et al., Anal. Chim. Acta, 1983, 145, 101) or catalytic calorimetry (Danielsson et al., Appl. Biochem. Bioeng., 1981, 3, 97).
Glycerol Hydrogen peroxide Amperometry Electrode Calorimetry

"Determination Of Fungal α-amylase By Flow Injection Analysis"
Anal. Chim. Acta 1984 Volume 158, Issue 2 Pages 375-377
Preben W. Hansen

Abstract: A manual iodine - starch method has been adapted for use in the analysis of broths from Aspergillus oryzae fermentations. The absorbance of the residual starch - iodine complex was measured at 570 nm following degradation of starch by the enzyme at 37°C and pH 4.7. Rectilinear calibrations were obtained over the range 0.01 to 0.1 amylase units mL-1. Results agreed well for the determination of α-amylase in diluted culture broth by flow injection analysis and by the manual method, but the flow injection method affords a sampling rate of 80 h-1, ~5 times that possible by the manual method.
α-Amylase Fermentation broth Biochemical analysis 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

"Synthesis Of O,o'-dihydroxyazo Compounds And Their Application To The Determination Of Magnesium And Calcium By Flow Injection Analysis"
Anal. Chim. Acta 1984 Volume 159, Issue 1 Pages 289-298
H. Wada and G. Nakagawa, K. Ohshita

Abstract: Seven such compounds were synthesized, and were found to be highly sensitive reagents for Mg (e = 47,000) and Ca (e = 39,000). Because of its ease of preparation and purification and its stability in alkaline solution, 4-(4-diethylamino-2-hydroxyphenylazo)-3-hydroxynaphthalene-2,7-disulfonic acid was the preferred reagent. By masking Fe(III), Al, Cu(II), Zn, Mn(II) and Cd with 2,3-dimercaptopropanol(I) and triethanolamine(II), the sum of Mg and Ca was determined. Magnesium was determined alone by masking Ca and the other metals with a ligand buffer containing Ba, 3,6-dioxaoctane-1,8-diamine-NNN'N'-tetra-acetic acid, I and II, and Ca could then be determined by difference. Calibration graphs were rectilinear over the ranges 0.1 to 1.2 mg L-1 (Mg) and 0.4 to 4 mg L-1 (Ca). The method was used to determine Mg and Ca in tap-water and a standard serum; the results compared well with those for the waters obtained by AAS or EDTA titration and with the certified value for the serum. A diagram of the flow injection manifold is given; the PTFE tubing was 0.5 mm in i.d. except for the back-pressure coil (0.25 mm i.d., 50 cm long). The chromogenic reagent and buffer solution were each delivered at 0.81 mL min-1 with a peristaltic pump, and the sample was injected into the buffer stream via a rotary valve. Sample and reagent solution were mixed in a 300-cm coil and passed to a flow cell (10 mm light path; 20 µL volume) for measurement of absorbance.
Calcium Magnesium Blood Serum Water Spectrophotometry

"Spectrofluorimetric Flow Injection Determination Of Cyanide"
Anal. Chim. Acta 1984 Volume 161, Issue 1 Pages 257-263
P. Linares, M. D. Luque de Castro and M. Valcarcel

Abstract: Cyanide (0.1 to 20 ppm) was determined, with a coefficient of variation of <2%, by fluorogenic reaction with pyridoxal or pyridoxal 5-phosphate under normal flow injection or stopped-flow conditions. In either mode, with use of pyroxidal, K+, Na+, Sr(II), SO42-, NO3-, Br-, Cl-, ClO4-, S2O82-, oxalate, EDTA, citrate and tartrate did not interfere at a ratio to CN- of 100. With pyroxidal 5-phosphate, K+, Na+, Ca(II), SO42-, NO3-, Cl-, F-, ClO4-, S2O82-, oxalate, EDTA, CO32-, acetate, S2O32- and MoO42- did not interfere in 100-fold amount. Tolerances for interfering ions (e.g., Pb(II) and Fe(II)) were generally higher in the stopped-flow method. Diagrams are given of the manifolds, together with optimum values of the variable parameters for the determination; a weakly alkaline or a slightly acidic final solution was required with use of pyridoxal or its 5-phosphate, respectively.
Cyanide Fluorescence

"Determination Of Molybdenum In Steels By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1984 Volume 161, Issue 1 Pages 245-255
F. J. Krug, O. Bahia and E. A. G. Zagatto

Abstract: The SCN- method was used with detection at 480 nm. The effects of Fe(III), acidity, reagent concentration. and interfering species were investigated by using the merging-zones approaching for flow injection analysis; this reduced drastically the number of standard and reagent solution required. The routine procedure developed (details given) was applied to 12 standard steels; the results obtained agreed well with those of ICP-AES and of AAS by the method of standard additions, and with the certified values. Possible interference by V, Cu, W, Co(II) and Ni(II) and means of overcoming it are discussed. Steel samples were dissolved in aqua regia; 270 solution could be analyzed in 1 h for 0.1 to 4% of Mo, with coefficient of variation <2%.
Molybdenum Alloy Spectrophotometry

"Comparison Of Titrimetric, Spectrophotometric And Ion-chromatographic Methods For Determination Of Hydrogen Carbonate In Drinking And Mineral Waters"
Anal. Chim. Acta 1984 Volume 162, Issue 1 Pages 451-455
Da-renk Yan, B. R&ouml;ssner and G. Schwedt

Abstract: In the titrimetric method the sample was titrated with 0.02 M HCl in the presence of an indicator or by use of a pH meter (end-point at pH 4.4). In the spectrophotometric method, a series of standard solution of NaHCO3, containing KH2PO4 and methyl red, and each one diluted to 25 mL with CO2-free water, was prepared for absorbance measurements at 520 or 570 nm. Analysis of the samples was effected similarly, but 20 mL of natural water (<100 mg L-1 of HCO3-) or 0.5 to 5 mL of mineral water (100 to 1000 mg L-1 of HCO3-) was used in place of NaHCO3. A continuous-flow procedure based on the spectrophotometric method was also investigated, in which the detection limit was 0.75 mg l-1, and >60 samples per hour could be analyzed. For the ion-chromatographic method, a HPLC system was used, but only for a few analyzes of tap-water. Results for tap-water, river water and mineral water samples were in good agreement for each method.
Bicarbonate River Mineral Water Spectrophotometry

"Spectrophotometric Determination Of Lithium Ion With The Chromogenic Crown Ether, 2'',4''-dinitro-6''-trifluoromethylphenyl-4'-aminobenzo-14-crown-4"
Anal. Chim. Acta 1984 Volume 162, Issue 1 Pages 285-291
Y. P. Wu and G. E. Pacey

Abstract: The named reagent {16-(ααα-trifluoro-4,6-dinitro-o-tolylamino)-2,6,9,13-tetraoxabicyclo[12.14.0]octadeca-1(14),15,17-triene} reacts with alkali-metal ions, e.g., Li+, in aqueous solution to form complexes that can be extracted into CH2Cl2 for spectrophotometry at 464 nm. The calibration graph was rectilinear for 14 to 560 mg L-1 of Li, and, in the determination of 280 mg L-1 of Li, 3 g L-1 of Na could be tolerated. The method was applied to the determination of Li in serum (doped with LiCO3) by batch or flow injection analysis, and the results obtained agreed with those of AAS The method was more selective and sensitive than an ion-pairing method based on use of benzo-14-crown-4.
Lithium Metals, alkali Blood Serum Clinical analysis Spectrophotometry Sample preparation

"Determination Of Urea With An Ammonia Gas-sensitive Semiconductor Device In Combination With Urease"
Anal. Chim. Acta 1984 Volume 163, Issue 1 Pages 143-149
F. Winquist, A. Spetz and I. Lundstr&ouml;m, B. Danielsson

Abstract: An Ir - Pd metal oxide semiconductor capacitor and urease were used in two systems. One comprised essentially a column of immobilized urease in a flow injection system. Urea was determined in whole blood and serum (after 500-fold dilution) by this method; the serum values were in reasonably good agreement with those obtained by a spectrophotometric method, the coefficient of variation (n = 10) for 4.5 mM urea in whole blood was 4.6%, and recoveries of additions of 0.5 to 2 mM urea to whole blood ranged from 85 to 106%. The second system was an enzyme probe based on urease enclosed between a dialysis membrane and a gas-permeable membrane. The dialysis membrane formed part of a flow-cell through which the buffered sample was pumped, and the capacitor was mounted 0.1 mm from the other membrane. Up to 5 mM urea could be determined. For the first method, the limit of detection was 0.2 µM-urea, and the calibration graph was rectilinear up to 50 µM, for 150 µL portions of the diluted samples. For the second method, the calibration graph was non-rectilinear, and the limit of detection was 0.01 mM.
Urea Blood Serum Whole Electrode

"Determination Of The Substrates Of Dehydrogenases In Biological Material In Flow Injection Systems With Electrocatalytic NADH Oxidation"
Anal. Chim. Acta 1984 Volume 163, Issue 1 Pages 299-303
A. Schelter-Graf, H. -L. Schmidt and H. Huck

Abstract: Applications are described of the NADH-sensitive system described previously (Huck et al., Anal. Abstr., 1984, 46, 8J126) that incorporated epoxyacrylic resin-bound dehydrogenases and a modified graphite electrode. The determination of D- and L-lactate in butter, L-glutamate in beef cubes, and ethanol in beer, and the control of the enzymatic hydrolysis of N-acetyl-DL-leucine by aminoacylase are discussed. The results obtained agreed well with those by spectrophotometric methods.
Ethanol l-Glutamate d-Lactate l-Lactate N-Acetyl-DL-leucine Biological material Beer Food Cube Electrode Potentiometry

"Determination Of Penicillin-V In Fermentation Samples By Flow Injection Analysis"
Anal. Chim. Acta 1984 Volume 166, Issue 1 Pages 293-295
Ib Schneider

Abstract: The flow injection procedure involves three reagent streams, each at 0.92 mL min-1 and maintained at 45°C. Sample solution (3 µL) is injected into a penicillinase solution stream (in citrate - phosphate buffer solution of pH 6.2) and pumped through a 20-cm mixing coil to allow enzymatic hydrolysis of the penicillin to penicilloic acid. The stream is then mixed with aqueous HgCl2 and aqueous molybdoarsenic acid and passed through a 50-cm mixing coil. The 'molybdenum blue' formed is measured at 670 nm. The calibration graph was rectilinear for 100 to 1000 iu mL-1 of phenoxymethylpenicillin and sample throughput was 90 h-1. Results obtained by this procedure were compared with those obtained with an AutoAnalyzer (r = 0.954).
Phenoxymethylpenicillin Penicillin V Fermentation broth Spectrophotometry

"Evaluation Of Critical Parameters For Measurement Of PH By Flow Injection Analysis. Determination Of PH In Soil Extracts"
Anal. Chim. Acta 1985 Volume 169, Issue 1 Pages 209-220
Cui Hongbo, E. H. Hansen and J. Rka

Abstract: The parameters affecting pH measurements in a flow injection system incorporating a tubular PVC-based pH-sensitive membrane electrode have been evaluated. A dispersion coefficient, Dmax, of 1.008 at peak maximum is required and the buffering capacity of the carrier stream must be less than that of the sample solution. Suitable system designs are discussed. Examples are presented of the determination of pH in 16 soil extracts; the results agreed with those obtained by conventional glass electrode measurements.
pH Environmental Electrode Electrode Potentiometry Sample preparation

"Determination Of Cholesterol By Flow Injection Analysis With Immobilized Cholesterol Oxidase"
Anal. Chim. Acta 1985 Volume 174, Issue 1 Pages 293-297
M. Masoom and Alan Townshend

Abstract: The injected sample passes at pH 7 through a column of cholesterol oxidase, immobilized on controlled-porosity glass by cross-linking with glutaraldehyde, and the H2O2 produced is detected with an amperometric flow-cell detector. The calibration graph of peak height vs. concentration. is rectilinear for up to 80 mg dl-1 with a coefficient of variation of 1 to 3%, the detection limit is 0.2 µg, and the achievable sample throughput is 80 h-1. The method was applied to the determination of cholesterol in blood serum, wax-wool alcohol and a butter extract and gave results in good agreement with those obtained by established procedures.
Cholesterol Wax wool Blood Serum Food Amperometry

"Experimental Comparison Of Flow Injection Analysis And Air-segmented Continuous-flow Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 189-201
C. J. Patton and S. R. Crouch

Abstract: A miniature continuous-flow analyzer. was used that could be configured to either technique to enable comparison to be made with minimal bias. In the determination of Cl- by its reaction with Hg(SCN)2 in the presence of Fe(III) up to 350 determinations h-1 could be made by either technique. The coefficient of variation were generally <1% at the 15 mg L-1 level (n = 5). The techniques were complementary. The performances of open-tubular, single-bead-string and helical-coil reactors were compared.
Chloride Water Spectrophotometry

"Use Of Holding Coils To Facilitate Long Incubation Times In Unsegmented Flow Analysis. Determination Of Serum Prostatic Acid Phosphatase"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 225-231
B. F. Rocks and R. A. Sherwood, M. M. Hosseinmardi and C. Riley

Abstract: An automated distribution valve is described that directs samples into one of four holding coils where they remain for a pre-determined time. The device is applied to the determination of acid phosphatase activity by a method similar to that described by Fabiny-Byrd and Ertingshausen [Clin. Chem. (Winston-Salem, N.C.), 1972, 18, 841] in which 1-naphthyl phosphate is hydrolyzed and the liberated 1-naphthol is coupled with a diazonium salt for absorbance measurement at 405 nm. The within-batch coefficient of variation (n = 10) at 4.2 and 23.5 iu L-1 are 8.0 and 2.0%, respectively. The results compared well with those obtained by a manual method (r = 0.98).
Acid phosphatase Serum Human Spectrophotometry

"Potentiometric Detection In Flow Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 359-370
K. T&oacute;th, J. Fucsk&oacute;, E. Lindner, Zs. Feh&eacute;r and E. Pungor

Abstract: Flow-through potentiometric detection in flow injection analysis is discussed and the performance characteristics of ion-selective electrodes with respect to rectilinear response, detection limit, selectivity and stability are studied. A method for the determination of F- with a selective electrode in rain-water is described, and a K+-selective electrode described by Tarcali et al. (Anal. Abstr., 1986, 48, 11J139) was applied to the analysis of blood serum. The results were in good agreement with those obtained by ion-chromatographic methods (for F-) and flame-photometric methods (for K).
Potassium Fluoride Blood Serum Rain Electrode Electrode Potentiometry

"Coated Tubular Solid-state Chloride-selective Electrode In Flow Injection Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 407-417
J. F. Van Staden

Abstract: The construction of the electrode is described and illustrated. Response times are 3 to 4 s and the range is 5 to 5000 mg L-1 for 30 µL samples. Mean recoveries of 67 and 114 mg L-1 are 97.8 and 98.9%, respectively, with coefficient of variation in the analysis of 16 water samples being <1.7% (n = 15). The results agree well with those obtained spectrophotometrically.
Chloride Environmental Electrode Electrode

"Determination Of Lead In Gasoline By A Flow Injection Technique With Atomic Absorption Spectrometric Detection"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 491-496
Colin G. Taylor and John M. Trevaskis

Abstract: The organic lead compound is oxidized with iodine (3% in toluene) and the product is diluted with a solution of 1% of Aliquat 336 (methyltrioctylammonium chloride) in isobutyl methyl ketone. This solution is injected into a carrier stream of acetone for aspiration into the air - acetylene flame for measurement at 283.3 nm. The response is rectilinear for up to 16 mg L-1 with a limit of detection of 0.1 mg l-1. The standard deviation is between 2 and 5 mg L-1 for gasoline containing between 328 and 384 mg L-1 (n = 4). The results agree closely with those obtained by AAS and titrimetry.
tetraalkyllead Oil Industrial Spectrophotometry

"Rapid Determination Of Chemical Oxygen Demand In Waste Waters And Effluents By Flow Injections Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1-3 Pages 267-278
J. M. H. Appleton and J. F. Tyson, R. P. Mounce

Abstract: The reagent stream containing K2Cr2O7 - H2SO4 is merged with a stream of water into which the sample is injected. After reagent and sample are mixed the K2Cr2O7 is reduced in a reactor and the absorbance of the Cr(III) produced is measured at 445 nm. Bivalent Hg is added to prevent interference by Cl-, and Ag2SO4 to catalyse the oxidation of n-alcohols and acids. The results for 11 samples agree well with those obtained by a standard method; a high-pressure system and 50-m manifold are not needed.
Chemical oxygen demand Waste Spectrophotometry

"Flow Injection And Microwave-oven Sample Decomposition For Determination Of Copper, Zinc And Iron In Whole Blood By Atomic Absorption Spectrometry"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 351-357
M. Burguera and J. L. Burguera, O. M. Alarc&oacute;n

Abstract: The sample and 0.3 M HCl - 0.4 M HNO3 reagent are injected in parallel into the flow injection system and mixed, and the sample is mineralized on passage through a microwave oven (2.45 MHz) to the nebulizer of an AAS detection system. The mean recoveries are 103.0 and 103.2% with coefficient of variation of 2.0% for added amounts of 0.5 and 1.0 mg L-1 of Cu, respectively; 101.5 and 101.1%, and 4.0 and 3.2% for 8 and 16 mg L-1 of Zn, respectively, and 102.8 and 101.8%, and 2.0 and 2.2% for 0.2 and 0.6 g L-1 of Fe, respectively. There is good agreement with the results obtained by conventional spectrophotometry.
Copper Zinc Iron Whole Clinical analysis Spectrophotometry

"Simple Procedure For Hydrodynamic Injection In Flow Injection Analysis Applied To The Atomic Absorption Spectrometry Of Chromium In Steel"
Anal. Chim. Acta 1986 Volume 181, Issue 1 Pages 265-270
E. A. G. Zagatto, O. Bahia Fo, M. F. Gin&eacute; and H. Bergamin o

Abstract: The technique is based on use of an electrically operated commutator to keep constant the dead volume arising from hydrodynamic pressure gradients and diffusion and requires only a simple flow injection system with one peristaltic pump operating continuously. A flow diagram and description of the proposed commutator system are given. Differences between effective sample size and the dimensions of the injection duct are emphasized, particularly for small volumes. The coefficient of variation are usually <1% for injections of 1 to 10 µL. The injection technique was assessed in a spectrophotometric model system with bromocresol green and its accuracy was measured for the determination of Cr (2.8 to 31.1% w/w) in 10 standard steels. The results agreed well with those obtained by ICP-AES and conventional AAS. With a sample rate of 120 h-1, coefficient of variation (n = 3) ranged from 0.26 to 2.69%.
Chromium Alloy Spectrophotometry Spectrophotometry

"Spectrophotometric Flow Injection Determination Of Ascorbic Acid By Generation Of Triiodide"
Anal. Chim. Acta 1986 Volume 184, Issue 1 Pages 243-250
J. Hern&aacute;ndez-M&eacute;ndez, A. Alonso Mateos, M. J. Almendral Parra and C. Garc&iacute;a De Mar&iacute;a

Abstract: Tri-iodide and its starch complex were generated in a flow injection system of three channels containing (a) 0.08 M KI plus 1.20 g L-1 of starch, (b) 46 µM-KIO3 in 1 mM H2SO4, and (c) carrier solution (pH 1.5 to 11.0), at flow rates of 1.5, 1.5 and 3.0 mL min-1, respectively; I3- and the starch complex were detected at 350 and 580 nm, respectively, and ascorbic acid(I) was measured as a negative peak. The range of rectilinearity depended on the concentration. of KIO3 and I was determined at concentration. of 0.1 to 40 µg L-1 with coefficient of variation of 1.5 to 8.0%. Results for different samples compared well with those obtained by titrimetry. The method has been applied to pharmaceutical preparations and fruit juice and jam containing vitamin C.
Ascorbic acid Fruit Food Pharmaceutical Spectrophotometry

"Determination Of Lead In The Urine Of Exposed And Unexposed Adults By Extraction And Flow Injection/atomic Absorption Spectrometry"
Anal. Chim. Acta 1986 Volume 186, Issue 1 Pages 273-277
Jos&eacute; Luis Burguera and Marcela Burguera, Luis La Cruz O and Olga Raquel Naranjo

Abstract: Lead is extracted from urine with ammonium pyrrolidine-1-carbodithioate into isobutyl methyl ketone, and the extract is analyzed by flow injection AAS, by injection into the water carrier stream (flow rate 3.8 mL min-1). The calibration graphs are rectilinear over the range 15 to 200 µg l-1. The detection limit is 10 µg l-1, recoveries are 96 to 105%, and coefficient of variation are 5% (within- and between-day; n = 10 and n = 30, respectively). Results agree well with those obtained by spectrophotometry.
Lead Urine Clinical analysis Spectrophotometry Sample preparation

"Automated Flow Injection Extraction Method For Determination Of Bittering Compounds In Beer"
Anal. Chim. Acta 1986 Volume 187, Issue 1 Pages 339-342
Ylva Sahlestr&ouml;m, Sigrid Twengstr&ouml;m and Bo Karlberg

Abstract: The flow injection procedure described is an adaptation of a standard manual method. A 100 µL portion of degassed beer is injected into a 0.1 M HCl carrier stream (1 mL min-1), which, after passing through a 50-cm mixing coil, is mixed with 2,2,4-trimethylpentane (0.5 mL min-1). The resulting stream is passed through a 200-cm mixing coil and thence into a phase-separation unit equipped with a PTFE membrane (cf. Ibid., 1986, 179, 315), and the absorbance of the separated organic phase is measured at 275 nm in a flow-through spectrophotometer. Results for 22 products agreed well with those obtained by the manual procedure. The sampling rate is 60 h-1.
Acids, bitter Isohumulone Isocohumulone Isoadhumulone Beer Malt Spectrophotometry Sample preparation

"Spectrophotometric Flow Injection Determination Of Cellobiose Dehydrogenase Activity In Fermentation Samples With 2, 6-dichlorophenolindophenol"
Anal. Chim. Acta 1986 Volume 188, Issue 1 Pages 285-288
Kaj Andr&eacute; Holm

Abstract: Cellobiose dehydrogenase activity (range 0.25 to 1 iu mL-1) is monitored by oxidation of cellobiose to cellobionolactone. The cellobiose substrate, the 2,6-dichlorophenolindophenol(I) reagent solution in Tris buffer (pH 7.5) and the gluconolactone(II) solution in acetate buffer are mixed before addition of the enzyme. After incubation at 50°C for 20 s the absorbance is measured at 605 nm. The decrease in absorbance is a measure of enzyme activity, because I is reduced to a colorless compound. The presence of II prevents reaction of any β-glucosidase. With a sample throughput of 120 h-1, the correlation coefficient between the flow and manual procedures is 0.96 (n = 40).
Enzyme, cellobiose dehydrogenase Spectrophotometry

"Flow Injection Determination Of Ammonia In Kjeldahl Digests By Gas Diffusion And Conductometry"
Anal. Chim. Acta 1987 Volume 193, Issue 1 Pages 19-27
Celio Pasquini and Lourival Cardoso de Faria

Abstract: The digest (100 µL) was injected into a stream of water (1.6 mL min-1) and mixed with a stream of 2 M or 3 M NaOH containing 1% of EDTA (1.6 mL min-1) at ambient temperature The resulting stream was passed (3.2 mL min-1) to a diffusion cell and the NH3 was allowed to diffuse through a PTFE membrane into a second water stream, which was passed into a flow cell for conductometric determination of NH3. The manifold was constructed from polyethylene tubing (0.8 mm i.d.). There was no interference from 1.25 M H2SO4, 7 to 30 g L-1 of K2SO4, 6 mM Ca(II), Fe(III), Al(III), Mg, Zn(II), Cu(II) or Se(IV) or 3 mM Hg(II) in the determination of 2 mM or 3 mM NH3. The method was applied to samples of vegetables, animal feeds and fertilizers, and results agreed with those by a distillation - titration method. In the determination of 1 to 4% of N the coefficient of variation (n = 5) was 1%. The sampling rate was ~100 h-1.
Ammonia Feed Commercial product Vegetable Conductometry

"Flow Injection Determination Of Nitrite And Nitrate With Biamperometric Detection At Two Platinum Wire Electrodes"
Anal. Chim. Acta 1987 Volume 194, Issue 1 Pages 119-127
A. Hulanicki, W. Matuszewski and M. Trojanowicz

Abstract: Nitrite and NO3- were determined in a flow injection system with a carrier solution (2.4 mL min-1) of 0.1 M H2SO4 and 0.2 M KI. The amperometric detector consisted of a flow cell containing two platinum or PTFE-coated graphite electrodes (8 mm x 0.3 mm) maintained at a constant polarizing voltage of 100 mV. Rectilinear calibrations were achieved over the range 2 to 30 µM with a detection limit of 0.4 µM for each analyte. Nitrate was determined by the inclusion in the flow system of an 8-cm glass column packed with cadmium granules which had been activated by treatment with 0.1 M CuSO4. A carrier solution containing 1% of NH4Cl or (NH4)2SO4 was used through the reductor and EDTA was added to the other carrier to suppress cation interferences. Determination of NO3- in aqueous soil extracts gave similar results to those obtained by potentiometric determination with a NO3--selective electrode.
Nitrate Nitrite Environmental Amperometry Electrode Electrode Electrode Electrode Sample preparation Potentiometry

"Flow Injection Determination Of Phosphate Species In Detergents With A Calcium Ion-selective Electrodes"
Anal. Chim. Acta 1987 Volume 197, Issue 1 Pages 353-359
Peter W. Alexander and Javapa Koopetngarm

Abstract: The flow injection manifolds were made of polyethylene tubing (i.d. 1.14 mm) and an Omnifit T-connector in a two-channel system. The sample solution (0.25 ml), containing citrate, EDTA, pyrophosphate or tripolyphosphate(I), was injected into a carrier stream (4.75 mL min-1) of 50 mM Na2B4O7 buffer and then mixed with a buffered stream of 0.1 mM Ca at the T-junction before reaching the Ca(II)-selective electrode. The calibration graph was rectilinear for 0.1 to 10 mM I and results agreed with those obtained by HPLC. Results are presented for the other ligands.
Citrate EDTA Pyrophosphate Tripolyphosphate Commercial product Electrode Potentiometry

"Determination Of Acetaldehyde By Flow Injection Analysis With Soluble Or Immobilized Aldehyde Dehydrogenase"
Anal. Chim. Acta 1987 Volume 198, Issue 1 Pages 37-44
Ala'ddin M. Almuaibed and Alan Townshend

Abstract: Acetaldehyde(I) in aqueous solution was determined by a double-injection valve technique with the soluble cited enzyme or by use of a glass mini-column (2.5 cm x 2 mm) of the enzyme immobilized on CNBr-activated Sepharose 4B. The carrier stream was 0.15 M KCl - 0.9 mM NAD+ - 0.04 M Na4P2O7, with the addition of 6 mM 2-mercaptoethanol in the column method. Flow rates of 1.0 and 0.8 mL min-1 and pH values of 9.0 and 9.5 were selected for the free and immobilized enzyme methods, respectively. The NADH produced was monitored at 340 nm. The calibration graphs were rectilinear for 6 to 31 and 6 to 37 µg mL-1 of I with the soluble and immobilized enzyme, respectively; the corresponding detection limits were 30 and 20 ng in 30 µL and the sample throughput was 40 to 45 h-1. Ethanol up to 5% did not interfere. The immobilized enzyme system was preferred.
Acetaldehyde Spectrophotometry

"A Simple Stopped-flow Method With Continuous Pumping For The Spectrophotometric Flow Injection Determination Of Boron In Plants"
Anal. Chim. Acta 1987 Volume 199, Issue 1 Pages 137-145
M. A. Z. Arruda and E. A. G. Zagatto

Abstract: A flow injection system in which a commutating device permits the peristaltic pump to operate continuously is proposed as an alternative way of stopping a processed sample inside a flow-through detector. The method is shown to improve the spectrophotometric determination of B in plants (Krug et al., Anal. Abstr., 1981, 41, 5D50), which is based on a relatively slow reaction. Effects of commutating times, flow rates, manifold dimensions and reagent concentration. are studied. With the same analytical frequency and azomethine H consumption as the original procedure, the proposed system is more sensitive owing to a threefold increase in the sample processing time and the absence of significant sample dispersion. Results are reproducible (coefficient of variation <1%) and agree with those obtained originally.
Boron Plant Spectrophotometry

"Multidetection Flow Injection Techniques For Manipulation Of Sensitivity Amplification And Dilution Methods"
Anal. Chim. Acta 1987 Volume 199, Issue 1 Pages 15-27
A. R&iacute;os, F. L&aacute;zaro, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: Different multi-detection flow injection methods available for use with a single diode-array spectrophotometric detector were compared for the determination of formaldehyde in water by reaction with pararosaniline - SO32-. The sample was directly inserted into the system without prior dilution or concentration. and the detector data was treated by amplification or dilution methods as indicated by conventional calibration graphs. Three manipulation methods were compared in terms of accuracy and precision. The linear systems, monitoring at single and several wavelengths, and the cyclic systems had the same lower determination limit but detection at several wavelengths showed the widest determination range, cyclic systems the narrowest. All three techniques allowed extensive manipulation of the analysis signal in unsegmented flow systems.
Formaldehyde Environmental Spectrophotometry

"Automated Spectrophotometric Field Monitor For Water Quality Parameters. Determination Of Nitrate"
Anal. Chim. Acta 1987 Volume 200, Issue 1 Pages 523-531
J. Richard Clinch and Paul J. Worsfold, Harry Casey

Abstract: The design and operation are described of an automated spectrophotometric field monitor based on flow injection analysis for the determination of NO3- in river water. The sample (30 µL) is injected into aqueous 1% NH4Cl as carrier stream (0.7 mL min-1); the solution then passes through a 40-mm reductor column of copperized Cd, and is mixed with N-1-naphthylethylenediamine dihydrochloride (0.25 g l-1) - sulfanilamide (12.5 g l-1) solution in 10% H3PO4. The absorbance of the resulting solution is monitored by a photometric detector with a green light-emitting diode. Response was rectilinear up to 12 mg L-1 of nitrate-N and the detection limit was 24 µg l-1. The coefficient of variation ranged from 0.0 to 0.7%. Results agreed well with those from two other spectrophotometric methods.
Nitrate River Spectrophotometry

"Continuous-flow Enzymatic Determination Of Creatinine With Improved Online Removal Of Endogeneous Ammonia"
Anal. Chim. Acta 1987 Volume 200, Issue 1 Pages 61-72
M. E. Collison and M. E. Meyerhoff

Abstract: The endogenous NH3 (1 mM) in a physiological sample (diluted with buffer of pH 9.5) is removed by an online gas pre-dialysis unit at 45°C, comprising a PTFE coil and an acid reservoir trap. The sample is passed to a flow-through enzyme reactor coil containing immobilized creatinine deiminase which converts creatinine(I) into NH3 and N-methylhydantoin. The liberated NH3 is detected with a membrane electrode. The peak potentials are directly proportional to I concentration. The method is precise and selective and I can be determined in serum and urine samples containing abnormally high levels of NH3. Determination of I in serum samples (n = 30) correlated with an existing Technicon AutoAnalyser colorimetric method (r = 0.996).
Creatinine Blood Serum Urine Electrode Electrode

"Automated Flow Injection Determination Of Sulfonamides By The Bratton-Marshall Reaction For Clinical Analysis, Assays And Dissolution Studies Of Formulation"
Anal. Chim. Acta 1988 Volume 204, Issue 1-2 Pages 271-283
M. A. Koupparis and P. I. Anagnostopoulou

Abstract: Two flow injection manifolds are described based on the Bratton - Marshall reaction, one for 2 to 20 mg L-1 of sulfonamide and the other for 0.5 to 5 mM. N-(1-Naphthyl)ethylenediammonium chloride is used as chromogenic reagent with detection at 545 nm. The method was used in the determination of sulfonamides in serum, urine, feeds and formulations, and for automated dissolution studies of tablets. The detection limit was 0.6 to 1.1 mg l-1, and the coefficient of variation was <0.5% (n = 10). The analysis rate was 72 samples h-1. The pseudo-titrimetric method gave a 1.3% mean difference from the HPLC technique.
Sulfonamides Blood Serum Feed Pharmaceutical Urine Clinical analysis Spectrophotometry

"Bioluminescence Flow System For Determination Of Branched Chain L-amino Acids In Serum And Urine"
Anal. Chim. Acta 1988 Volume 205, Issue 1-2 Pages 229-237
S. Girotti, A. Roda, M. A. Angellotti and S. Ghini, G. Carrea and R. Bovara, S. Piazzi and R. Merighi

Abstract: Deproteinized urine was centrifuged at 1000 g, the supernatant liquid was filtered (0.45 µm), and the filtrate was diluted 10 to 100-fold with 0.11 M Na4P2O7 buffer of pH 9.0. Serum samples were filtered and diluted with the same buffer. A 10 µL portion of the test sample was injected into an air stream which was mixed with a reagent stream containing NAD+ in the buffer solution and fed through a 1-m reaction coil containing immobilized leucine dehydrogenase, whereupon branched-chain L-amino-acids (L-leucine, L-valine and L-isoleucine) were oxidized to the corresponding 2-oxo-acids, with the formation of NADH. The product was mixed with 10 µM-flavine mononucleotide - 27 µM-decanol - 0.5 mM dithiothreitol in 0.1 M potassium phosphate buffer (pH 6.9) and fed into a second reaction coil where NADH was oxidized in the presence of immobilized NADH oxidoreductase (FMN) and alkanal mono-oxygenase (FMN-linked) and the luminescence was measured. Calibration graphs were rectilinear for 20 to 2000 pmol of acid; the limit of detection was 5 pmol. Within- and between-assay coefficient of variation (n = 10) were 7% and 9.7%, respectively, and recovery was 85 to 116%. Other amino-acids and branched-chain 2-oxo-acids did not interfere. Results for 41 serum samples correlated well with those obtained by ion-exchange chromatography.
Amino acids, L l-Isoleucine l-Leucine l-Valine Blood Serum Urine Bioluminescence

"Improved Monosegmented Continuous-flow System For Sample Introduction In Flame Atomic Spectrometry"
Anal. Chim. Acta 1988 Volume 206, Issue 1-2 Pages 253-262
J. S. Brodbelt and R. G. Cooks

Abstract: An improved monosegmented system with only one air plug placed in the tailed portion of the sample, which is intercalated into an unsegmented carrier stream, is proposed for AAS. Air removal is not required, allowing a simpler system to be designed; flame instability is not a problem with the larger samples. The system is compared with the original approach in which the sample was introduced between two air bubbles. The effects of sample volume (25 to 1000 µL) and air-plug length (5 to 200 cm) on the recorded peak and measurement reproducibility are discussed. The single-line system proposed for determining Zn in plant digests is very stable, and the precise results agreed with those obtained by conventional AAS. The determination of Ca in natural waters demonstrates the feasibility of monosegmentation when a reagent solution (La) must be added. The accuracy, precision, sample consumption and system stability attained are good.
Calcium Zinc Plant Environmental Spectrophotometry

"Amperometric Assay Of Glucose And Lactic Acid By Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 209, Issue 1-2 Pages 231-237
Bo A. Petersson

Abstract: Plasma was injected into a carrier stream of aqueous phosphate buffer (containing Na2EDTA, Na benzoate, NaH2PO4, Na2HPO4 and NaCl) at 1 mL min-1. Immobilized glucose or lactate oxidase membrane electrodes were coupled to an amperometric detector and polarized at +600 mV for detection of H2O2. The response was rectilinear for up to 40 mM glucose(I) and up to 10 mM lactic acid(II), with coefficient of variation of 1.5%. Results for determination of I and II agreed well with those obtained by established methods.
Glucose Lactic acid Blood Plasma Amperometry Clinical analysis Electrode

"Flow Injection Cyclic Voltammetry"
Anal. Chim. Acta 1988 Volume 211, Issue 1-2 Pages 287-292
F. Ca&ntilde;ete, A. R&iacute;os, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: A flow injection cyclic voltammetric assembly is described, which allows fast current vs. potential scans in normal or derivative mode. The recordings are similar to those obtained with photodiode-array detectors. At flow rates up to 2 to 3 mL min-1 and with an injected volume up to 150 to 200 µL, the system could be used for qualitative and quantitative analysis, theoretical studies and multi-component analysis.
Voltammetry

"Simultaneous Spectrophotometric Determination Of Calcium And Magnesium With Chlorphosphonazo-III By Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 212, Issue 1-2 Pages 291-295
Yuan Youxian

Abstract: To determine the total Ca plus Mg the sample (50 µL) was injected into a mixed stream of triethanolamine - HCl buffer solution (pH 7.0; 2.0 mL min-1) and aqueous 0.016% chlorphosphonazo III (I; 1.5 mL min-1). After reaction in a PTFE coil (80 cm x 0.8 mm), the absorbance of the solution was measured at 668 nm (e = 64,000 for Ca complex, 48,000 for Mg complex). Calibration graphs were rectilinear for up to 2 mg L-1 of Ca and Mg; the detection limit for each was 0.02 mg l-1. In determination of 2.0 mg L-1 each of Ca and Mg, the coefficient of variation were 3.7 and 3.2%, respectively (n = 12). To determine Ca alone the procedure was repeated at pH 2.2, adjusted with 1.6 mM HCl (e = 14,600 for Ca complex, 66 for Mg complex). The Mg was determined by subtraction. At both pH values Ba and Sr interfered. The method was applied to samples of tap- and seawater; results agreed with those obtained by AAS.
Calcium Magnesium Sea Water Spectrophotometry

"Flow Injection Determination Of Sodium And Potassium By Separation On A Silica Column And Extraction-spectrophotometry With Benzo-18-crown-6 And Tetrabromophenolphtalein Ethyl Ester"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 289-298
Shoji Motomizu and Minoru Onoda

Abstract: A sample was injected into the carrier stream (H2O) and mixed with the reagent stream containing crown ether and Li acetate before passing to a column (30 cm x 1 mm) of C-200 silica gel (100 to 200 mesh). The percolate was mixed with reagent solution (EDTA - LiOH) and then extractant (K salt of tetrabromophenolphthalein ethyl ester) in a segmentor before passing through an extraction coil (2 m x 0.5 mm) to a phase separator containing a porous membrane. The absorbance of the organic phase was measured at 620 nm. The flow rate of each of the streams was 0.8 mL min-1. Of the three crown ethers studied, the best results were achieved with benzo-18-crown-6. Calibration graphs were rectilinear up to 2 and 0.2 mM for Na and K, respectively. Results for determination of Na and K in river water agreed with those obtained by AAS. The method was also applied to the analysis of tap-water.
Sodium Potassium River Water HPLC Spectrophotometry Sample preparation

"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

"Determination Of Sulfur Dioxide In Young White Wines By Flow Injection With Chemiluminescence Detection"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 429-432
J. L. Burguera and M. Burguera

Abstract: Sample (100 µL) and 30 mM Ce(IV) in 20 mM H2SO4 (200 µL) were injected into streams of 0.2 µM-riboflavin phosphate (sensitizer) and water, respectively, each flowing at 1.2 mL min-1. The sample and reagent were mixed in a flow cell and the chemiluminescent emission was recorded. The calibration graph was rectilinear for 5 to 300 mg L-1 of SO2 in wine and the coefficient of variation (n = 6) for 10 and 100 mg L-1 of SO2 were 3.2 and 2.5%, respectively. Results for five wine samples agreed with those from the pararosaniline method.
Sulfur dioxide Wine White Chemiluminescence

"Flow Injection Spectrophotometric Determination Of Palladium In Catalysts And Dental Alloys With 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 271-277
Tadao Sakai and Norko Ohno

Abstract: Sample solution (100 µL, containing 10 µg L-1 of Pd) was injected into the carrier stream (0.1 M HCl; 0.85 mL min-1) which was then mixed with 0.15 mM 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline in acetate buffer (pH 3.7; 0.85 mL min-1) in a 2-m reaction coil. The absorbance was measured at 612 nm (e = 98,400). The calibration graph was rectilinear for 10 to 100 µg L-1 of Pd and the detection limit was 2 µg l-1. The coefficient of variation (n = 10) for 100 µg L-1 of Pd was 0.6%. The sample throughput was 50 h-1. Interference from Cu could be masked by adding 1 mM EDTA solution to the carrier stream. The method was applied in the determination of Pd in catalysts and dental alloys and results agreed well with those obtained by ICP-AES.
Palladium Industrial Alloy Spectrophotometry

"Potentiometric Flow Injection Determination Of Trace Chlorine Based On Its Redox Reaction With An Iron(III)/iron(II) Buffer"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 349-357
Nobuhiko Ishibashi and Toshihiko Imato, Hiroki Ohura and Sumio Yamasaki

Abstract: Sample solution (140 µL) is injected into the water carrier stream (0.71 mL min-1) which then merges with the potential buffer solution (0.71 mL min-1) consisting of 0.01 M Fe(III) - 0.01 M Fe(II) containing 0.3 M KCl and 0.5 M H2SO4. The sample passes through a 90-cm reaction coil, and the change in potential of the flow-through electrode is recorded. The detector comprises a gold-plated oxidation - reduction potential electrode and a Ag - AgCl reference electrode. Calibration graphs are rectilinear for 0.1 to 10 µM-Cl and the detection limit is 50 nM. The coefficient of variation at the 2.5 and 8 or 10 µM levels are 2.5 and 1.1%, respectively. Tolerance limits for co-existing ions are tabulated. Results for two water samples agreed with those obtained by the o-tolidine method.
Chlorine Environmental Electrode Electrode Potentiometry

"Spectrophotometric Determination Of Aromatic Primary Amines And Nitrite By Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 207-216
Krishna K. Verma and Kent K. Stewart

Abstract: Samples of aromatic primary amines (including sulfa drugs) were injected into the carrier stream (0.1 M HCl) which subsequently merged with 4-(methylamino)phenol(I) in a 10-cm coil and then with oxidizing reagent (K2Cr2O7) in a 400-cm coil. The purple - red color developed by oxidative coupling of amine with I was measured at 530 nm. Calibration graphs were rectilinear for 0.05 to 20 µg mL-1 of amino-N. Selectivity for some amines in the presence of sterically hindered amines or those having an electron-deficient aromatic nucleus was improved compared with that by the manual procedure. A slightly modified version (illustrated) of this flow injection system was used for the determination of NO2- by diazotization of sulfanilamide(II) and determination of residual II as above. The calibration graph was rectilinear for 1 to 10 µg mL-1 of NO2- and the sampling rate was 120 h-1. The coefficient of variation (n = 10) for 1 and 8 µg mL-1 of NO2- were 1.8 and 0.7%, respectively.
Amines, primary Nitrite Spectrophotometry

"Spectrophotometric Flow Injection Determination Of Sucrose And Total Reducing Sugar In Sugar-cane Juice And Molasses"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 247-257
I. L. Mattos, E. A. G. Zagatto and A. O. Jacintho

Abstract: Samples of sugar-cane juice or molasses were injected into the carrier stream (H2O at 1 mL min-1) which was then mixed with 1 M HCl in a 250-cm PTFE coil for hydrolysis of sucrose. This solution then merged with 3 M NaOH - 1%K3Fe(CN)6 reagent solution in a 580-cm PTFE coil, the solution was debubbled and 0.1% 1,10-phenanthroline - 0.5 M acetic acid - 0.1 M citric acid - 30 mg L-1 of Fe(III) was added. The solution passed through a 200-cm polyethylene coil and the absorbance was measured at 512 nm. The sampling rate for determination of sucrose and total reducing sugar was 40 h-1. The sampling rate was almost doubled when only reducing sugar was determined and a simplified flow system (illustrated) could be used. The coefficient of variation for determination of sucrose and total reducing sugar in sugar-cane juice were 0.47 and 0.38, respectively; those for molasses were 0.54 and 0.44%. Results generally agreed well with those from classical methods.
Sucrose Sugars, reducing, total Carbohydrates Vegetable Juice Spectrophotometry

"Multi-ion Sensor Cell And Data-acquisition System For Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 359-366
T. J. Cardwell, R. W. Cattrall and P. C. Hauser, I. C. Hamilton

Abstract: The flow injection system comprised a miniature flow cell (illustrated) with several solid-contact electrodes, a differential amplifier and a computer-controlled data-acquisition unit. Ion-selective membrane electrodes containing valinomycin, neutral carrier ETH 1001 and tetradodecylammonium nitrate were used for determination of K, Ca and NO3-, respectively, and a Ag - AgCl electrode was used for determining Cl-. The data-acquisition system is described in detail. The system was tested for the analysis of soil solution by using 0.1 M Na acetate containing 10 µM-KNO3 and 10 µM-CaCl2 as carrier stream (1 mL min-1). Calibration graphs were rectilinear over the range 0.1 mM to ~0.1 M for all four ions. Results agreed with those obtained by automated flow injection AAS and ion chromatography.
Potassium Calcium Nitrate Chloride Environmental Electrode Electrode Electrode Electrode Sample preparation Sensor

"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 Determination Of Proteins Based On The Lowry Spectrophotometric Method"
Anal. Chim. Acta 1989 Volume 217, Issue 2 Pages 359-362
Hans L&uuml;di and Anita B&auml;rtschi

Abstract: The flow injection system was based on the use of Folin - Ciocalteu reagent, with 1,4-dithio-DL-threitol to accelerate the formation of the colored complex, which was detected at 700 nm. The calibration graph for bovine serum albumin was rectilinear between 0.01 and 0.1 mg mL-1. The detection limit was 5 µg mL-1 and up to 0.5 mg mL-1 could be determined. The injection frequency was 20 h-1. Results obtained by the flow injection method and by the manual Lowry procedure correlated well. Egg lysozyme, alkaline phosphatase and β-lactoglobulin were also determined.
Albumin Lysozyme Enzyme, alkaline phosphatase β-Lactoglobulin Egg Cow Serum Spectrophotometry

"Sandwich Techniques In Flow Injection Analysis. 2. Simultaneous Determination Of Iron(II) And Total Iron"
Anal. Chim. Acta 1989 Volume 219, Issue 2 Pages 345-350
J. Alonso, J. Bartrol&iacute;, M. del Valle and R. Barber

Abstract: Water samples (1500 µL) are inserted in one of the channels of the manifold described previously (Ibid., 1987, 199, 191) between zones of water and 1% ascorbic acid solution, with subsequent addition of 1,10-phenanthroline at pH 5.0. Absorbance is measured at 520 nm. The signal exhibits a plateau region corresponding to Fe(II) followed by a peak corresponding to total Fe. The system allows up to 90 injections h-1. The rectilinear working ranges are 0.1 to 9 and 0.3 to 12 mg L-1 for Fe(II) and total Fe, respectively. The coefficient of variation (n = 22) were 0.6 and 1.2% for Fe(II) and total Fe in the analysis of a solution containing 2 mg L-1 each of Fe(II) and Fe(III). Results obtained for various ground waters agreed with those obtained by a standard spectrophotometric method.
Iron(2+) Iron(III) Iron Ground Spectrophotometry

"Indirect Potentiometric Flow Injection Determination Of Silver In Photographic Fixing Solutions"
Anal. Chim. Acta 1989 Volume 220, Issue 1 Pages 287-291
Frazier Nyasulu

Abstract: Sample (0.4 ml) is injected into a stream of water that merges with a stream of 2 M H2SO4 at 70°C, and the SO2 produced is removed by diffusion through a 75-cm coil of Gore-Tex microporous PTFE tubing (pore size 3.5 µm). An excess of S2- in 6 M NaOH is added downstream of the coil, and the decrease in S2- concentration. is measured with a Ag - Ag2S electrode. The calibration graph is rectilinear from 1 mg L-1 to 10 g L-1 of Ag, and the detection limit is 0.04 mg l-1. Results for five fixing solution agreed well with those obtained by AAS.
Silver Fixing solution Potentiometry Electrode

"Determination Of Cyanide And Thiocyanate By A Spectrophotometric Flow Injection Method"
Anal. Chim. Acta 1989 Volume 220, Issue 1 Pages 65-74
Jamal A. Sweileh

Abstract: The described two-step flow injection method involved the complexation of CN- with Ni(II) in citric acid solution followed by the determination of SCN- by oxidation with chloramine-T buffer solution (pH 5.5±0.05) to ClCN, and reaction with Na isonicotinate - Na barbiturate reagent at 65°C to form a blue complex, the absorbance of which was measured at 600 nm. To determine CN- plus SCN-, the above procedure was repeated with a Ni-free citric acid solution and the CN- concentration. was calculated by difference. The pH, temperature and Ni(II) concentration. were optimized. Calibration graphs were rectilinear up to 2.5 and 5 µg mL-1 of CN- and SCN-, respectively, and the corresponding detection limits were 0.05 and 0.08 µg mL-1. Chloride, S-, AgI, Co(II) and Ni(II) ions interfered. The procedure was applied to synthetic solution; results were in good agreement with those obtained by the ASTM method. The throughput was 10 h-1.
Thiocyanate ion Cyanide Spectrophotometry

"Determination Of Total 3α-hydroxy-bile Acids In Serum By A Bioluminescent Flow Injection System Using A Hollow-fibre Reactor"
Anal. Chim. Acta 1989 Volume 225, Issue 2 Pages 273-282
Kayoko Oda, Shigeru Yoshida and Shingo Hirose, Tatsumori Takeda

Abstract: A bacterial luciferase and NADH-flavin mononucleotide oxidoreductase were covalently co-immobilized on CNBr-activated Sepharose 4B. A permeable membrane reactor was used to introduce NAD+ and the bioluminescent reagent [comprising flavin mononucleotide, dithiothreitol and decanal in phosphate buffer (pH 6.8)]. The column, filled with the immobilized bioluminescent enzyme, was placed in front of a photomultiplier tube inside a photon counter to give a continuous-flow light-emitting system which was versatile and simple. The membrane reactor flow injection system allowed >20 samples h-1 to be analyzed. The detection limit was 10 fmol of NADH for a 1 µL injection. The calibration graphs for Na cholate were rectilinear up to 10 µM and 5 to100 µM. Excellent reproducibility, precision and sensitivity were achieved. Results agreed with those obtained by fluorimetry.
Bile acids, 3-α hydroxy Cholate Blood Serum Bioluminescence

"Determination Of Glucose In Wine And Fruit Juice Based On A Fibre-optic Glucose Biosensor And Flow Injection Analysis"
Anal. Chim. Acta 1989 Volume 225, Issue 2 Pages 293-301
Bernd A. A. Dremel, Bernhard P. H. Schaffar and Rolf D. Schmid

Abstract: A glucose biosensor based on an oxygen optrode with immobilized glucose oxidase was used in a flow injection system to determine glucose in wine and fruit juice. The consumption of 0 was determined by dynamic quenching of the fluorescence of decacyclene by molecular 0. Glucose oxidase was adsorbed on a sheet of carbon black and cross-linked with glutaraldehyde. Carbon black was used as an optical isolation to protect the optrode from interference from ambient light and sample fluorescence. The calibration graph was rectilinear for 0.1 to 500 mM glucose, with a coefficient of variation of 2% for 100 mM (n = 5). The optrode was stable for >400 h in continuous use. No interference at 500 mg L-1 of SO32- for 5 mM glucose was observed. Up to 60 samples h-1 could be analyzed with a precision similar that of standard methods. The method was simple, economical, could be computer-controlled and required minimal sample prep.
Glucose Fruit Wine Sensor Fluorescence Optrode

"Direct Automatic Determination Of Free Acidity In Oils By Flow Injection Analysis"
Anal. Chim. Acta 1989 Volume 225, Issue 2 Pages 431-436
P. Linares, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: The sample is mixed with ethyl ether - ethanol (1:1) flowing at 1.5 mL min-1, and this is mixed with ethanolic 50 mM KOH - 0.01% phenolphthalein (0.9 mL min-1) and then with a second similar reagent stream. After passage through a 250-cm reaction coil, the decrease in absorbance of the mixture is measured at 562 nm. Peak heights are measured for low concentration. (0.15 to 0.81%) and peak widths or flow injection titration is used for higher concentration. (4.04%). The sampling rate is 60 h-1. Results agreed with those of the standard method.
Acidity Oil Spectrophotometry

"Rapid Flow Injection Sandwich-type Immunoassays Of Proteins Using An Immobilized Antibody Reactor And Adenosine Deaminase-antibody Conjugates"
Anal. Chim. Acta 1990 Volume 229, Issue 1 Pages 47-55
I. H. Lee and M. E. Meyerhoff

Abstract: Human IgG (I) and α1-acid glycoprotein (II) were determined in biological samples in a flow injection assay cycle involving sequential injection of sample and adenosine deaminase - antibody conjugate (goat anti-I or rabbit anti-II antibodies for I and II, respectively) into a 0.025 M Tris - HCl (pH 7.5) carrier buffer. Bound antibody - analyte was retained on a column (2.5 cm x 1.54 mm) of goat anti-I or rabbit anti-II antibodies immobilized on controlled-pore glass beads. Substrate (0.25 mM adenosine in 0.5 M Tris - HCl of pH 7.5) was then fed into the reactor and the eluate was monitored by NH4+-selective potentiometry. Between steps a wash stream of 0.1 M glycine - HCl (pH 2.2) was used. Working ranges were from 5 to 400 ng mL-1 of I and 3 to 15 µg mL-1 of II. Results for I agreed well with those by several commercially available methods and recoveries were 102 to 107%. Analysis time was ~12 min.
Protein Biological Immunoassay Potentiometry

"Conducting Organic Salt Amperometric Glucose Sensor In Continuous-flow Monitoring Using A Wall-jet Cell"
Anal. Chim. Acta 1990 Volume 229, Issue 1 Pages 83-91
Hari Gunasingham and Chin-Huat Tan

Abstract: A paste was prepared by mixing tetrathiafulvalene - 7,7,8,8-tetracyanoquinodimethane complex salt with 10% of Nujol (with or without added graphite) and packed into the well of an electrode consisting of a PTFE holder and a graphite disc. The paste was successively covered with glucose oxidase, bovine serum albumin - glutaraldehyde (4:1) and a 0.03 µm-pore polycarbonate membrane. The electrode was used with a large-volume wall-jet cell, a graphite counter-electrode and Ag - AgCl reference electrode in an automated system for (i) flow injection or (ii) steady-state analysis. At 0.2 V a rectilinear response was observed for up to 60 mM glucose (I) by method (i) or 30 mM by method (ii). Results obtained by method (ii) were more consistent than those by method (i). For determination of 5.5 to 11 mM I in whole blood at 0.15 V and 0.5 mL min-1, results by method (ii) were lower than those by method (i) and were in better agreement with results obtained with use of a Haemo-glutotest 20-800R (Boehringer Mannheim) test strip.
Glucose Whole Amperometry Electrode Electrode Sensor

"Spectrophotometric Determination Of Ethanol In Blood Using A Flow Injection System With An Immobilized Enzyme (alcohol Dehydrogenase) Reactor Coupled To An Online Dialyser"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 115-119
Gabrielle Maeder, Jean-Luc Veuthey, Michel Pelletier and Werner Haerdi

Abstract: Whole blood (110 µL) which was not pre-treated was introduced into the carrier stream of sodium pyrophosphate decahydrate - semicarbazide hydrochloride - glycine - NaCl - NAD+ - water (pH 9.0) by means of a rotary valve. The mixture was passed at 650 µL min-1 to a dialyser comprising a Cuprophan membrane between two Plexiglas plates, then to a controlled-pore glass enzyme reactor with a nylon filter fabric (mesh size 100 µm) at each end, kept at 25°C. The absorbance of NADH was measured at 340 nm. The calibration graph was rectilinear from 3 to 40 µg mL-1 of ethanol, corresponding to 0.3 to 4.0 g of ethanol per 1000 g of whole blood prior to dilution. The results agreed with those from direct-injection GC.
Ethanol Whole Spectrophotometry

"Fluorimetric Sensor For The Determination Of Fluoride At The Nanograms Per Millilitre Level"
Anal. Chim. Acta 1990 Volume 234, Issue 2 Pages 345-352
Danhua Chen, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: Fluoride solution and 2 µM binary complex of Zr and Calcein Blue were injected simultaneously from double valves with a sample loop of 500 µL into a reactor (60 cm x 0.5 mm i.d.). The ternary complex formed was retained in the fluorescence flow cell (1.1 mm i.d.) of DEAE-Sephadex resin (40 to 120 µm) and the fluorescence was measured at 405 nm (excitation at 335 nm). After the maximum fluorescence had been obtained 0.4 M HCl was injected from a third valve to elute the complex and restore the baseline. The calibration graph was rectilinear from 1 to 40 ng mL-1 of F-; coefficient of variation was 1% (n = 7). The sample throughput was 30h-1. A comparison of the cited flow-through sensor with a probe sensor for the same chemical system showed the former to be superior. The method was applied in the analysis of potable water.
Fluoride Water Fluorescence Sensor

"Determination Of Magnesium In Blood Serum Using A Flow Injection System With A Potential-scanning Electrochemical Detector Equipped With A Thin-film Deaerator"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 161-166
Rivka Goldik, Chaim Yarnitzky and Magda Ariel

Abstract: A flow injection analysis system is described involving formation of the eriochrome black T (I) - Mg complex and its detection via its adsorptive reduction current peak at a potential-scanning electrochemical detector, equipped with a static-Hg-drop electrode vs. Ag - AgCl and a novel thin-film deaerator (illustrated). The method is basically an adaptation of a previous batch method (cf. An et al., Talanta, 1985, 32, 479). Diluted serum (100 µL) is injected into a carrier stream (0.6 mL min-1) of 2% ethylenediamine solution which is merged with the reagent stream (0.4 mL min-1) containing 0.003 to 0.004% of I, and the solution is passed through a 12-cm reaction coil to the deaerator - detector device. The calibration graph is rectilinear for 0.14 µg mL-1 of Mg. Results showed good agreement with those obtained by AAS. Sampling rate is 35 h-1.
Magnesium Blood Serum Electrochemical analysis Electrode

"5,5-Diethylbarbiturate Tubular Electrode For Use In Flow Injection Detection Systems"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 221-225
Jos&eacute; L. F. C. Lima and M. Concei&ccedil;&atilde;o B. S. M. Montenegro, J. Alonso, J. Bartroli and J. G. Raurich

Abstract: A tubular electrode was prepared, sensitive to barbitone (I), based on tetraoctylammonium I in 2-nitrophenyl octyl ether as liquid ion-exchanger on PVC membranes. The characteristics of the electrode were examined and compared with those of a conventional electrode. The use of the electrode to determine I in pharmaceutical preparations was evaluated with use of a double-channel flow injection manifold. Results showed reasonable agreement with those of the official B.P. method. The detection limit was ~1 mM I, and response was rectilinear to ~0.3 mM I. The electrode was unaffected by pH in the range 9 to 11.5.
Barbitone Pharmaceutical Electrode Electrode Ion exchange

"Automated Method For The Determination Of Boron In Water By Flow Injection Analysis With Inline Preconcentration And Spectrophotometric Detection"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 199-206
I. Sekerka and J. F. Lechner

Abstract: The system (schematically presented) involved pre-concentration. of B from a sample by ion-exchange on a column of Amberlite IRA-743, elution with a stream of azomethine-H in 2 M ammonium phosphate buffer (pH 6.6) containing EDTA, and detection of the B complex at 420 nm. Full operating details are given. Online pre-concentration. was carried out for 3 or 6 min for 10 or 10 µg L-1 of B, respectively. Recoveries were 96 to 101%. The coefficient of variation were 10% for 10 µg L-1 and 5% for 10 to 200 µg l-1. The detection limit was 1 µg l-1, with a sampling rate of 10 h-1. The method was applied to natural- and tap-water. Results show good agreement with those of ICP-AES. There was no interference, even for colored samples.
Boron Environmental Water Ion exchange Spectrophotometry

"Chemiluminescence Determination Of Vitamin B12 By A Flow Injection Method"
Anal. Chim. Acta 1991 Volume 243, Issue 1 Pages 127-130
Y. K. Zhou, H. Li, Y. Liu and G. Y. Liang

Abstract: In the cited method, the sample stream was mixed with a reagent stream containing 30 mM luminol and 40 mM H2O2 (total flow rate 7 mL min-1; optimum pH ~10.9) before passage through a cell for chemiluminescence measurement. The signal was unaffected by acidification of the sample solution with HCl. The calibration graph [constructed for Co(NO3)2] was rectilinear from 5 µg to 50 ng; the detection limit was 1.0 ng for 50 µL injections. The method was applied to the analysis of three vitamin preparations; coefficient of variation (n = 3) were 0.9 to 1.2%. Results agreed with those obtained by spectrophotometry.
Vitamin B12 Pharmaceutical Chemiluminescence

"Extraction Flow Injection Spectrophotometric Determination Of Bismuth With Lead Tetramethylenedithiocarbamate"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 275-280
Joanna Szpunar-Lobinska

Abstract: Powdered silicate rock (0.5 g) was mixed with concentrated HNO3 (2 ml) and the mixture was evaporated to dryness. The residue was dissolved in concentrated HF (5 ml) and concentrated HClO4 (1 ml), the solution was evaporated to dryness and the process was repeated. The final residue was dissolved in 1 M HCl (3 ml) and diluted to 10 mL with water. A 500 µL portion was injected into 0.4 M NH3 buffer solution (pH 9.0; carrier solution) in the flow system described (with diagram). The carrier stream was mixed with a masking stream containing 1.5% KCN and 0.1% EDTA in a mixing coil. The resulting stream was merged with 0.05% Pb tetramethylenedithiocarbamate in CHCl3 (extraction reagent stream) and the color forming reaction was allowed to take place in an extraction coil. Phases were separated with a PTFE membrane separator and the absorbance of the organic phase was measured at 380 nm. The calibration graph was rectilinear up to 5 ppm of Bi. The detection limit was 0.1 mg L-1 of Bi. At 3 mg L-1 of Bi, the coefficient of variation was 1.4%. The sampling rate was 72 h-1. Results compared well with those by ICP-AES.
Bismuth Silicate Spectrophotometry Sample preparation

"Flow Injection Spectrophotometric Determination Of Phosphate Using Crystal Violet"
Anal. Chim. Acta 1991 Volume 254, Issue 1-2 Pages 197-200
D. Thorburn Burns, D. Chimpalee, N. Chimpalee and S. Ittipornkul

Abstract: Aqueous fertilizer solution, and waste water after boiling with HNO3, were filtered and the pH was adjusted to between 5 and 8. The solution were injected into a carrier stream of 0.5% poly(vinyl alcohol) at 1.5 mL min-1 and were mixed with reagent streams of 0.1 M NaMoO4, 0.5 mM crystal violet [C. I. Basic Violet 3] and 12.5% HNO3, all at 1.5 mL min-1. The absorbances were measured at 560 nm. The calibration graph was rectilinear up to 5.0 µg mL-1 of phosphate with a limit of detection of 0.02 µg mL-1. The coefficient of variation for 1.0 µg mL-1 (n = 10) was 0.69%. The results were in good agreement with those obtained by a standard method.
Phosphate Commercial product Spectrophotometry

"Membrane-type Immobilized-enzyme Reactors For Use In Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 256, Issue 1 Pages 53-57
S. Cliffe*, C. Filippini, M. Schneider and M. Fawer

Abstract: A simple membrane reactor housing with negligible dead volume was constructed to take commercially available membranes. Three immobilized-enzyme systems were investigated: glucose oxidase, glutaminase and laccase for the determination of glucose, glutamine and phenolics, respectively. The response of reactors with Zetaffinity AM membranes was comparable to that of packed bed reactors containing controlled-pore glass or Biosynth VA Epoxy, but the membrane reactors had less pressure build-up and thus increased lifetime compared with the packed beds (which were prone to clogging) in continuous monitoring. Their lifetime was determined by the loss of enzyme activity. Membrane-type reactors were prepared using a commercially available support. In three test systems, involving glucose oxidase, glutaminase and laccase, they compared favorably with packed-bed reactors in a flow injection set-up. Although similar responses were observed for all reactor types, the membranes are easier to handle than microparticles. When making continuous inline measurements of bioprocesses at high sampling frequencies, the lifetimes of packed beds of controlled pore glass were determined by pressure build-up within the reactor. When replaced with membrane reactors, no clogging was observed, the lifetimes being determined by loss of enzyme activity.
Glucose

"Trace Enrichment Of Aluminum Ions On Immobilized Desferrioxamine"
Anal. Chim. Acta 1992 Volume 256, Issue 1 Pages 75-80
Lennart Ljunggren, Ina Altrell, Lars Risinger and Gillis Johansson*

Abstract: Desferrioxamine immobilized on porous glass was packed into a column (100 µL x 2.0 mm i.d.) and placed in the flow manifold of a flow injection system. Samples containing Al3+ were acidified with 1 mM HNO3, injected into the system and merged with NaOH to effect neutralization prior to entry into the column. The carrier was 0.1 M Na acetate buffer with 5 or 20 mM Ca lactate. The metal ions were eluted with 2 M HNO3 and the eluent was analyzed by flame or graphite-furnace AAS. There was quantitative uptake of the Al3+ at pH 5.5 to 6.0. The column temperature was kept at 50°C to allow for ligand-exchange kinetic effects. In the analysis of continuous ambulatory peritoneal dialysis solution, use of the immobilized desferrioxamine column gave improved Al detection limits, down to sub ng L-1 levels, compared with standard AAS. The column showed good stability over a 2 month period.
Aluminum Spectrophotometry 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

"Determination Of Mitozantrone Using Phase-selective A.c. Adsorptive Stripping Voltammetry In A Flow System With Selectivity Enhancement"
Anal. Chim. Acta 1992 Volume 256, Issue 2 Pages 231-236
Juan Carlos Cortina Villar, Agustin Costa Garc&iacute;a and Paulino Tu&ntilde;on Blanco*

Abstract: Urine was diluted 1:20 to contain standard additions of 25 nM-, 50 nM- and 75 nM-mitozantrone (final concentration.), and 0.1 mL portions of these solution were injected into a carrier stream of 0.1 M HClO4 (pH 1.12; 1.5 mL min-1). The mitozantrone became adsorbed on a carbon-paste electrode (prep. described), from which it was stripped by a.c. voltammetry. For 1 µM-mitozantrone in urine, the value obtained was 0.985 µM with a coefficient of variation (n = 5) of 3.7%. A flow cell incorporating a stationary carbon paste electrode coupled with a.c. voltammetry was used. Preconcentration. and determination of the cancer chemotherapy drug mitoxanthrone (I) were achieved via a flow injection approach utilizing adsorption of the drug on the electrode, followed by medium exchange and a.c. voltammetry on the adsorbed surface. A linear response was obtained in the concentration. range 5 x 10^-9-1.5 x 10^-7 M with aqueous samples. The method was used for the determination of I in urine without any sample pretreatment; the relative standard deviation obtained was 1.1% (n = 5) with a concentration. of 1 x 10^-6M. The proposed method is more selective than other methods suggested for the determination of I in urine and plasma samples, which usually require some kind of sample pretreatment.
Mitozantrone Urine Blood Plasma Voltammetry

"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

"Simultaneous Flow Injection Determination Of 2- And 4-nitrophenol Using A Photodiode-array Detector"
Anal. Chim. Acta 1992 Volume 258, Issue 2 Pages 269-273
M. E. Le&oacute;n-Gonz&aacute;lez*, L. V. P&eacute;rez-Arribas, M. J. Santos-Delgado and L. M. Polo-D&iacute;ez

Abstract: The sample, e.g., fruit juice, was injected into a carrier stream of 0.5 M phosphate buffer of pH 7.4 (2 mL min-1) and mixed with 0.13% tetrabutylammonium nitrate solution (1.2 mL min-1). The ion pairs were extracted into 1,2-dichloroethane and the absorbances at 260 and 410 were measured for 2- and 4-nitrophenol, respectively. The calibration graphs were rectilinear from 0.1 to 12 mg l-1, with detection limits of 0.03 mg l-1. The coefficient of variation (n = 8) at 6 mg L-1 of either compound was 0.15%. Recoveries of 1 to 10 mg L-1 from fruit juice were between 90 and 105%. A batch method was also examined, but gave a coefficient of variation of 2.1%. A flow injection method for the simultaneous determination of o- and p-nitrophenol in apple and orange juices is based on formation and extraction of ion pairs by using Bu4N+ as counter ion at pH 7.4 and diode-array spectrophotometric detection at 260 and 410 nm for o- and p-nitrophenol, respectively. The calibration graphs were linear for 0.1-12 mg/L. The relative standard deviation at 6 mg/L was 0.15% for both o- and p-nitrophenol and the detection limits were 0.03 mg/L.
2-Nitrophenol 4-Nitrophenol Juice Juice Spectrophotometry Sample preparation

"Determination Of Chemical Oxygen Demand In Aqueous Environmental Samples By Segmented Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 301-305
Li-Ching Tian* and Sao-Ming Wu

Abstract: A method is described for the determination of chemical oxygen demand (C.O.D) in aqueous environmental samples by segmented flow injection analysis. KMnO4 solution used as both an oxidant and a spectrophotometric reagent and D-glucose as a standard. When the reaction temperature is 95°C, the residence time is about 8 min and a sample throughput of 80/h can be achieved. The detection limit and relative standard deviation are 2 mg/litre and 0.7%, respectively, and the recovery is 85-95%. Chloride ion up to levels of 1500 mg/litre does not interfere with the results. C.O.D compared with those obtained using the Japanese Industrial Standard method and agreed within an error range of ±10%.
Chemical oxygen demand Environmental Spectrophotometry

"Application Of Square-wave Voltammetry For The Determination Of Ascorbic Acid In Soft Drinks And Fruit Juices Using A Flow Injection System"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 375-380
Ying-Sing Fung* and Song-Ying Mo

Abstract: A portion (100 µL) of test solution was injected into a stream of the supporting electrolyte (Britton - Robinson buffer) for transfer to a thin-layer electrochemical cell (volume 16 µL) equipped with vitreous-carbon working, stainless-steel counter and Ag - AgCl reference electrodes. The normal flow rate was 0.5 mL min-1, and the potential of the working electrode was scanned from +0.2 to +0.7 V in 1 s, with application of a computer-generated square waveform and measurement of the oxidation peak current at +0.46 V. The buffer pH was 2.87 to stabilize the ascorbic acid. The peak signal was rectilinearly related to ascorbic acid concentration. from 2 µM to 6 mM; food additives at normal concentration. levels did not interfere. Results obtained on blackcurrant juice, lemon tea, sugar-cane juice and apple juice were satisfactory. The application of square-wave voltammetry for detection in the flow injection determination of ascorbic acid in soft drinks and fruit juices was investigated. The pH of the solution was buffered at 2.87 to stabilize the ascorbic acid prior to anal. Parameters such as scan rate, square-wave amplitude, step height and flow-rate of electrolyte were found to have little effect on the potential, but a significant effect on the current. The anal. current is only slightly affected by the flow-rate of the electrolyte and a max. scan rate of 0.5 V/s can be used. As a compromise between sensitivity and selectivity, 40 mV was chosen as the amplitude of the square wave and 10 mV as the potential step height. Similarly, a flow-rate of 0.5 mL/min and an injection volume of 100 µL were chosen as a compromise between the sensitivity and resolution of the FIA method. With these procedures, the max. number of samples that could be analyzed was 120/h. The linear calibration range was from 2 x 10^-6 to 6 x 10^-3 M and the determination limit (10s) was 2 x 10^-7M. No significant interference was found from additives commonly found in juice and drink samples within their normal concentration. ranges. Four juice samples were analyzed using the developed method and the results were compared with those given by the established AOAC method. No significant difference was observed between the two methods used for the four samples studied.
Ascorbic acid Blackcurrent Tea Juice Juice Voltammetry Electrode

"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

"Direct Automatic Determination Of Bitterness In Virgin Olive Oil By Use Of A Flow Injection - Sorbent Extraction System"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 367-374
J. A. Gar&iacute;a-Mesa, M. D. Luque de Castro* and M. Valc&aacute;rcel*

Abstract: In the manifold shown, 20 µL of the oil was injected into a hexane carrier stream and passed through a column of C18-bonded silica to remove the sample matrix. With use of methanol as intermediate solvent, the bitter substances were carried by aqueous 50% methanol to a flow cell for spectrophotometry at 225 nm. The column was washed in the reverse direction with methanol, hexane and methanol and then reconditioned with aqueous methanol between samples. Results, expressed as absorbance at 255 nm divided by the oil concentration. (g dl-1), agreed with those obtained by a manual batch method; analysis times by the respective methods were 5 and 50 min. An automated version of an existing batch method for the determination of bitterness in virgin olive oil was developed. The automatic method is based on flow injection analysis (FIA) principles and is implemented by coupling an FIA manifold to a solid-liq. retention unit in which the sample matrix is retained on a C18-bonded silica-packed minicolumn, the analytes being monitored by UV spectrophotometry and the retained matrix being eluted in the opposite direction to detection, so it never reaches the detector. The automatic method clearly surpasses its manual counterpart in terms of solvent savings, anal. time (5 vs. 50 min) and labor requirements (none of the tedious preliminary steps of the manual method need be implemented). The relative standard deviation was 1.26% for K225 (absorbance at 225 nm/oil concentration. in g/100 mL) = 0.55.
Bittering compounds Oil Spectrophotometry Sample preparation

"Continuous-flow Method For The Determination Of Total Trihalomethane Formation Potential In Waters"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 335-338
Toyoaki Aoki*, Kouji Kawakami

Abstract: In the system described and illustrated, the sample stream is mixed with 10 mM NaClO in a 3-m PTFE reaction coil heated at 98°C, and the resulting solution is merged with 10% Na2SO3 solution (to remove surplus NaClO) before passage into a unit equipped with a microporous PTFE membrane and maintained at 50°C, where the trihalomethanes formed diffuse into a stream of 0.2 M NaOH. The alkaline stream is mixed with 30% nicotinamide solution in a 3-m PTFE coil at 98°C and cooled in ice before fluorescence measurement at 467 nm (excitation at 372 nm). For calibration with humic acid, the trihalomethane production was rectilinearly related to C concentration. from 1 to 5 mg l-1. The detection limit was 2.2 µg L-1 of trihalomethanes. The coefficient of variation was 4.3% for 5 mg L-1 of C as humic acid and 2.6% for 5 mg L-1 of C as albumin (n = 5). An analysis took 20 min, as compared with >26 h for the conventional Japanese method. The method was successfully applied to lake and river waters. A double-tube separation system with an inner tube of microporous poly(tetrafluoroethylene) (PTFE) and an outer tube of PTFE is proposed for the continuous determination of trihalomethane (THM) formation potential in waters. The THMs in the sample, after reaction with NaClO solution at 98°C and reduction of the residual ClO- with Na2SO3, are separated with the double-tube system at 50°C. They are then mixed with alkaline nicotinamide solution and heated at 98°C. After being cooled in an ice-bath, the reaction product is fed to a spectrofluorimeter, and the emission of fluorescence excited at 372 nm is measured at 467 nm. The response was obtained within 20 min. The detection limit (signal-to-noise ratio = 3) was 2.2 µg/L. The total THM formation potentials obtained by the present method for lake and river waters were in good agreement with those obtained by the Japanese standard batch method.
Methanes, trihalo Lake River Fluorescence

"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

"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

"Flow Injection Atomic Spectrometric Determination Of Inorganic Arsenic(III) And Arsenic(V) Species By Use Of An Aluminum-column Arsine Generator And Cold-trapping Arsine Collection"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 105-113
M. Burguera, J. L. Burguera and M. R. Brunetto, M. de la Guardia and A. Salvador

Abstract: The sample is injected into water as carrier and the solution (with or without introduction of 10% KI solution to reduce As(V)) is mixed with 5 M NaOH before passage through an electrically heated Pyrex column containing a rolled foil of metallic Al (~1 g) to reduce As(III) to AsH3. The AsH3 passes to a gas - liquid separator and is collected for 3 min in a liquid-N-cooled trap. The trap is then placed in hot water, and He is used to sweep the AsH3 into a fused-silica cell above an air - acetylene flame for AAS measurement at 193.7 nm. Analysis for As(III) and total As takes ~10 min. Optimized operating conditions are given. Interference in the determination of 1 ng of As(III) was caused by >10 ng of Ni, Be, Cr(III), Ag, Pb, Cu(II), Sn, Zr, or Fe(III). The detection limit was 0.25 µg L-1 of As(III) or As(V). The method was successfully applied to water samples from a trout fishery. A flow injection system is described for the selective determination of arsenic(III) and arsenic(V) (0.05-20 ng) in a 100 µL sample volume by hydride generation and atomic absorption spectrometry. An elec. heated aluminum column was used to generate the arsine in an alkaline medium. Recoveries averaged 97-99% for arsenic(III) and 95-98% for arsenic(V) with relative standard deviations of less than 4.3% in each instance. The detection limit was 0.25 µg L-1 (25 pg) of arsenic in both instances. This method was relatively free from interferences and was applied successfully to the determination of arsenic(III) and arsenic(V) in trout fishery water samples. The data obtained were compared with those produced by a hydride generation-cold trapping atomic absorption spectrometric detection method, using sodium tetrahydroborate(III) in hydrochloric acid. The results obtained by both methods were in close agreement, within 96-102%.
Arsenic(3+) Arsenic(5+) Arsenic, inorganic Water Spectrophotometry Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Acetaminophen In Drug Formulations"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 261-267
Krishna K. Verma, Archana Jain and Kent K. Stewart*

Abstract: The sample solution in 0.1 M HCl (50 µL) is injected into a carrier stream of 0.1 M HCl, and the resulting solution is merged with an oxidizing reagent comprising aqueous 0.2% Na 2-iodylbenzoate. The stream passes through a knitted reaction coil (25 cm x 0.5 mm) before detection of the quinonimine reaction product at 445 nm in an 8 µL flow-through cell. The rectilinear calibration range is 0.8 to 100 mg L-1 of paracetamol and the detection limit is 0.8 mg l-1. Sample throughput is 360 h-1. Slight interference is caused by dipyrone, ascorbic acid, isoniazid and SO32-, but excipients and numerous other drugs do not interfere. The method has been applied to 0.1 M HCl extracts of paracetamol tablets. Results agreed well with those obtained by LC. A flow injection method is described for the determination of acetaminophen (paracetamol) (linear range 0.8-100 µg mL-1) based on its oxidation with 2-iodylbenzoate in acid medium to produce a yellow-orange compound, believed to be N-acetyl-1,4- benzoquinoneimine, which is monitored at 445 nm. The sample throughput is 360 h-1. The precision (RSD) of determination was 0.5-2%. The method was applied to the determination of acetaminophen in drug formulations, and evaluated by analyzing spiked sample solutions, a mean recovery of 100.6% (range 96.3-105.2%) being obtained. No interference was observed from the common excipients of drugs and other active substances, e.g., dipyrone, acetylsalicylic acid, salicylamide and oxyphenbutazone. The possible application of the proposed method in content uniformity test and drug dissolution studies is indicated. Comparison of the present method with a liquid chromatography method for acetaminophen determination gave a mean difference of 1.2% (range 0.4-2.4%).
Acetaminophen Pharmaceutical Spectrophotometry

"Determination Of L-glutamate By Amperometric Flow Injection Analysis Using Immobilized Glutamate Oxidase: Manifold For Simultaneous Detection Of Component Signal And Blank Signal"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 155-159
Kiyoshi Matsumoto*, Koji Sakoda and Yutaka Osajima

Abstract: The system described (with diagrams) allows simultaneous detection of the L-glutamate (I) signal and the blank value. A microtube pump propels the carrier solution (0.1 M phosphate buffer of pH 7) and the sample solution to a 16-position switching valve; the carrier line includes an air damper, and two 180 µL sample loops are linked to the valve for injection. The stream of solution then passes through a glass tube (10 cm x 2 mm i.d.) containing glutamate oxidase immobilized on Amino-Cellulofine by means of glutaraldehyde (method described) or (for blank measurement) an enzyme-free Amino-Cellulofine column to a potentiostat (Anal. Chem., 1988, 60, 147) maintained at +0.65 V vs. Ag - AgCl for amperometry of the H2O2 produced. The blank signal is obtained from a sample that has passed through the blank reactor; the carrier solution is used to set the baseline. Response to L-aspartate and L-glutamine was only 0.48 and 0.25%, respectively, relative to that for I; complete selectivity for I over L-aspartate is attainable at pH 6.0. Sensor response is maintained for 15 days. Peak current is rectilinearly related to I concentration. from 0.01 to 0.3 mM; the coefficient of variation at 0.3 mM was 1.7% (n = 10). The method was applied to a range of foods. L-Glutamate oxidase was immobilized on Amino-Cellulofine and used as an enzyme reactor in a flow injection system. The hydrogen peroxide produced was monitored amperometrically. A new configuration is described for the determination of L-glutamate in food samples for which the matrix provides varying blank values. The peak current was linearly related to L-glutamate concentration. in the range 0.01-.03 mM, and the relative standard deviation was 1.7% in ten successive assays at the 0.3 mM level. The proposed method was used for seasoning anal. and compared well with results obtained with an L-glutamate kit (enzymatic, spectrophotometric) method.
l-Glutamate Food Amperometry

"Simultaneous Spectrophotometric Determination Of Iron And Copper In Serum With 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline By Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 197-203
Sam Woo Kang, Tadao Saki* and Noriko Ohno, Kazunori Ida

Abstract: The system described and illustrated incorporates a double-beam spectrophotometer with two flow cells. The sample is injected into 0.1 M HCl - 0.1 mM KIO4 as carrier and mixed with a 0.1 mM solution of the cited reagent in acetate buffer of pH 4.5 in a 15-cm reaction coil. The solution is passed through the first flow cell for measurement of the absorbance due to Cu(II) at 558 nm. A 10 mM solution of Na ascorbate in the buffer is introduced into the stream, which passes through a 700-cm reaction coil heated at 60°C before measurement of the absorbance at 558 nm in the second flow cell; in this instance an inverted peak for Fe(II) and a positive peak for Cu(II) are obtained. The Fe(III) present after adding the sample to the carrier does not interfere. The calibration graphs are rectilinear for 50 to 200 µg L-1 of Cu(II) or Fe(II) and the limit of detection is 2.4 µg l-1. Nickel and Co interfere at concentration. >10 µg L-1 which, however, are not encountered in serum samples. Serum is deproteinized with trichloroacetic acid at 90°C before analysis. Results on human, horse, bovine, chicken and goat serum agreed with those obtained by ICP-AES. A method for the simultaneous spectrophotometric determination of iron and copper by flow injection analysis was developed using 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N- sulfopropylamino)aniline. The flow system utilizes a double-beam spectrophotometric detector with two flow cells. The reagent forms water-sol. chelates with Cu(II) and Fe(II) in an acetate-buffered medium at pH 4.5. The molar absorptivities of the complexes are 65,000 L mol-1 cm-1 at 578 nm for Cu(II) and 87,000 L mol-1 cm-1 at 558 nm for Fe(II). In one reaction coil Fe(II) is oxidized to Fe(III) by KIO4, so the Fe(II) chelate is not formed and only the colored complexes with Cu(II) are monitored in the first flow cell. In a second reaction coil, the solution merges with sodium ascorbate solution to reduce Cu(II) and Fe(III) to Cu(I) and Fe(II). Thus only the Fe(II) complex is measured in the second flow cell. Cu(II) and Fe(II) in the range 50-200 µg L-1 are determined at 558 nm. The sample throughput is 30 h-1 with a precision of 1.2%.
Iron Copper Chicken Serum Serum Horse Serum Goat Cow Serum Serum Human Spectrophotometry

"Flow Injection Analysis Of Trace Elements By Use Of Catalytic Reactions"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 167-182
Takuji Kawashima*, Shigenori Nakano

Abstract: This review covers the mechanism of catalytic reactions involving trace elements, together with catalytic flow injection methods for the determination of Fe, Mn, Cu, Co, V, Cr, Mo and Se, as well as halides and other anions. Representative examples are given of organic compounds used in the indicator reactions. Comparison with batch methods shows that flow injection methods are sometimes less sensitive than their manual counterparts, but afford satisfactory accuracy and precision and have certain advantages (94 references). A review with 94 references. Catalytic reactions have importance in trace analyzes for elements, and kinetic-catalytic methods of anal. based on catalytic reactions have progressed recently. The change in a phys. property such as absorbance, fluorescence, chemiluminescence or electrode potential of a system with time is usually monitored in kinetic-catalytic methods, as these methods include time as a measured variable. Flow injection analysis (FIA) is considered to be a suitable technique for catalytic methods of analysis, i.e., the reaction can easily be controlled by fixing the flow rate of solutions and the length of the reaction coil, yielding reproducible mixing. The adaptation of FIA to catalytic methods can lead to many advantages such as higher precision, better detection limits and rapid sample throughput. After a brief review of the catalytic action of elements in redox reactions, the use of the catalytic reactions in FIA methods is discussed through representative examples.
Iron Manganese Copper Cobalt Vanadium Chromium Molybdenum Selenium Fluorescence Chemiluminescence Spectrophotometry Electrochemical analysis

"Spectrophotometric Determination Of Silicon In Bismuth Borosilicate Glass By Flow Injection"
Anal. Chim. Acta 1992 Volume 262, Issue 2 Pages 243-251
Frances A. Archer, Kenneth W. Street, Jr.*

Abstract: The cited method is based on the formation of heteropoly blue by the reduction of the yellow heteropoly complex β-molybdosilicic acid. Modifications made include removal of Bi interferent in sample preparation and removal of the HF matrix in flow injection. The cited method compared well with standard spectrophotometric and ICAP methods but results were not in agreement with calculated compositions. A spectrophotometric flow injection method for the determination of silicate based on heteropoly blue formation is presented. The proposed reagent gives a wider dynamic range than previously reported flow injection procedures. The Bi interference reported for the spectrophotometric method is eliminated in sample preparation, and the method is applied to the determination of Si in Bi borosilicate glass. Results are compared with spectrophotometric and inductively coupled Ar plasma emission spectrometric determinations
Silicon Bismuth Sample preparation Spectrophotometry

"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

"Amperometric Techniques In Flow Injection Analysis: Determination Of Magnesium In Sera And Natural Waters"
Anal. Chim. Acta 1992 Volume 269, Issue 1 Pages 41-48
Alison J. Downard, Joanne B. Hart, H. Kipton J. Powell* and Shuanghua Xu

Abstract: For water analysis, the flow injection analysis system (described) was based on the complexation of Mg by 0.15 mM Eriochrome Black T at pH 11.5 in 15% 1,2-diaminoethane - 0.3 M KCl during flow-through a reaction coil (100 cm x 0.51 mm); water was used as the carrier (0.6 mL min-1) with amperometric detection in a wall-jet microflow cell with a glassy carbon electrode (cf., Downard et al., ibid., 1992, 256, 117) and 0.45 mM EGTA and 0.04 M triethanolamine as masking agents. Rectilinear calibrations from 0.027 to 1.8 mg kg-1 of Mg were achieved with a detection limit of 5.5 µg kg-1 and coefficient of variation of 0.7% for water. Similarly conditions for serum were described (details given). Results were compared with those obtained by AAS. Magnesium was determined in a flow injection system by formation of the magnesium-Eriochrome Black T (EBT) complex at pH 11.5 (5% 1,2-diaminoethane in 0.1 M KCl) and amperometric measurement of the excess of EBT at +0.175 V on a glassy carbon electrode. From modeling calculations, pH and concentrations of EBT (3.75 x 10^-5M) and masking agent EGTA (1.12 x 10^-4M) were chosen so as to minimize interference from calcium. Electrode fouling from EBT oxidation products was countered by use of 0.2% surfactant (Hostapur SA 93) in the carrier stream. Iron(III) was masked with triethanolamine. For anal. of natural waters the linear working range was 0.027-1.8 mg kg-1 Mg and the relative standard deviation was 0.7% at 1.6 mg kg-1 Mg (n=11); the detection limit was 5.5 µg kg-1. Anal. of human blood serum samples was effected by two methods: direct injection of serum after a 20-fold dilution (Hostapur SA 93 countered the association of EBT with serum albumin) and after dialysis (2.5 min) to sep. Mg from acidified serum in the flow system. The linear working range for direct injection was as above and the relative standard deviation was 0.4% (n=9) at 1.0 mg kg-1 Mg. For each method the results were compared with those from flame atomic absorption spectrometry.
Magnesium Serum Human Environmental Amperometry Electrode

"Determination Of Chloride Ion Concentration In Natural And Waste Waters By Flow Injection Analysis With A Silver Chloranilate Reaction Column"
Anal. Chim. Acta 1992 Volume 270, Issue 1 Pages 217-221
Fumio Sagara*, Tetsuya Tsuji, Isao Yoshida, Daido Ishii and Keihei Ueno

Abstract: A carrier solution comprising ethanol - water - 0.1 M Na acetate buffer of pH 5.57, (5:4:1) was pumped into the flow system at 2.0 mL min-1. A 100 µL portion of sample water - ethanol - buffer (4:5:1) was injected and the mixture was passed through a cation-exchange column (5 cm x 4.61 mm) of Muromac 50W-X 4 (100 to 200 mesh; NH4+ form). The eluate was treated in a reaction column (same size) packed with Ag chloranilate powder connected to a spectrophotometric detector set at 530 nm. The calibration graph was rectilinear from 2 to 20 µg mL-1 of Cl-. Interferences from anions were negligible. When applied to the analysis of natural and waste waters, the Cl- could be determined in 2 min. The results agreed well with results obtained by a standard manual method. Cl- in natural water and wastewater was determined by flow injection analysis using a column packed with Ag chloranilate powder. EtOH-water-0.1 M Na acetate buffer (pH 5.57) (5+4+1, v/v/v) was used as the carrier at a flow rate of 2 mL/min. The chloranilate ion concentration, which corresponds to the Cl- concentration, in the carrier from the reaction column was monitored by a spectrophotometric detector at 530 nm. Interferences from multi charged cations were eliminated with the combined use of a cation-exchange column inserted in the upper stream of the reaction column. Interferences from anions were negligible. Cl- in natural water and wastewaters (1-20 µg/mL) could be determined rapidly (1 sample/2 min) with high reproducibility. The results agreed well with those obtained by the standard manual method.
Chloride Environmental Waste Spectrophotometry

"Determination Of Ultratrace Concentrations Of Tin By Adsorptive Cathodic Stripping Voltammetry On A Glassy Carbon Mercury Film Electrode"
Anal. Chim. Acta 1992 Volume 270, Issue 1 Pages 143-152
Samuel B. O. Adeloju* and Fleurdelis Pablo

Abstract: A sensitive and selective method is described for the determination of ultratrace concentrations. of tin by adsorptive cathodic stripping voltammetry on a glassy carbon mercury film electrode. The method involves a controlled pre-concentration. by accumulation of tin-catechol complexes on the electrode followed by stripping voltammetric measurement in the cathodic direction. The optimum conditions for the determination of tin by this method include the use of a rotating electrode at 1920 rpm, 0.10 M acetate buffer electrolyte (pH 4.2-4.7), 5 x 10^-4 M catechol, and an accumulation potential of -0.20 V vs. Ag/AgCl. A linear concentration. range is obtained from 0 to 35 µg/L and the limit of detection is 0.5 µg/L for an accumulation period of 300 s. An interference study with various metal ions indicated that these substances generally do not interfere with the tin determination, except for Cu, Cd, and Cr. The interference of Cu and Cd is eliminated by the addition of 1 x 10^-6 M EDTA into the solution The interference of surface-active organic substances, e.g., Triton X-100, is overcome by UV irradn. of the sample for 2 h. The method was successfully employed for the determination of tin in fruit juices. Comparison of the results obtained for the juices demonstrated reasonable agreement with those obtained by atomic absorption spectrometry.
Tin Fruit Voltammetry Electrode Electrode Electrode

"Flow Injection Analysis For The Measurement Of Penicillin V In Fermentation Media"
Anal. Chim. Acta 1993 Volume 274, Issue 1 Pages 117-123
Morten Carlsen, Lars H. Christensen and Jens Nielsen*

Abstract: Iodimetric, potentiometric and molybdenum blue flow injection analysis systems for the determination of penicillin (I) in fermentation media were evaluated. All three methods were based on the enzymatic hydrolysis of I to penicilloic acid (II) using β-lactamase, followed by the detection of II. β-Lactamase was immobilized on aminopropyl controlled-pore glass beads (120 to 200 mesh) and the beads were packed in a column and used as a packed-bed reactor. Conversion of I to II was 100%, therefore total I and II present in the sample was determined. The iodometric method was the best for measurements in fermentation media. By replacing the enzyme reactor with an enzyme-free dummy reactor, II alone was determined, and hence the concentration. of I was calculated. The limit of detection was 2.5 mg L-1 and calibration graphs were rectilinear from 2.5 to 150 mg l-1. There was no interference from other components in the fermentation medium. The iodometric analyzer. was applied to the monitoring of a fed-batch I fermentation; results correlated well with those obtained by LC.
Penicillin V Fermentation broth Potentiometry Spectrophotometry

"Simultaneous Determination Of Trace Metals In Human Hair By Dynamic Ion-exchange Chromatography"
Anal. Chim. Acta 1993 Volume 274, Issue 1 Pages 163-170
A. Sturaro*, G. Parvoli and L. Doretti, S. Zanchetta and G. Allegri, G. Battiston

Abstract: Sample was washed with non-ionic detergent solution, followed by Soxhlet extraction with ethyl ether. After drying at 105°C for 12 h, the sample was pulverized and digested with HNO3 - HClO4. The digest was evaporated to dryness and the residue was dissolved in mobile phase and mixed with Co solution (200 mg l-1; internal standard). Analysis was on a column (15 cm x 3.9 mm) of Waters Delta Pak RP-18 (5 µm) with aqueous 5% acetontrile containing 0.0433% sodium octanesulfonate and 0.6063% sodium hydrogen tartrate (adjusted to pH 3.65) as mobile phase (0.75 mL min-1) and UV and photodiode array detection at 546 and 492 nm, respectively. Online post-column derivatization with monosodium 4-(2-pyridylazo)resorcinol resulted in improved absorbance in the UV region. The simultaneous determination of Cu, Zn, Ni, Mn, Pb and Co was achieved with detection limits of ~1 µg g-1. Calibration graphs were rectilinear in the ranges 50 to 600 µg g-1, 2 to 80 µg g-1, 1 to 25 µg g-1, 5 to 200 µg g-1 and 0.1 to 2 µg g-1 for Zn, Cu, Ni, Pb and Mn, respectively. Results were confirmed by AAS and XRF.
Metals, trace Zinc Copper Nickel Lead Manganese Hair HPIC Spectrophotometry

"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

"Direct Determination Of Benzene In Gasoline By Flow Injection Fourier Transform Infrared Spectrometry"
Anal. Chim. Acta 1993 Volume 274, Issue 2 Pages 267-274
M&aacute;ximo Gallignani, Salvador Garrigues and Miguel de la Guardia

Abstract: Gasoline samples (300 µL), diluted 1:9 in hexane, were directly injected into hexane carrier (flow rate 0.28 mL min-1). Peak-height FTIR absorbance measurements were performed at 675 cm-1 and the baseline was established between 712 and 650 cm-1. The calibration graph was rectilinear from 0.02% (detection limit) to 0.8% benzene and the coefficient of variation (n = 5; 0.4% level) was ~1%. The results agreed with those obtained by offline and online standard additions methods. A rapid quality control method was developed which involved the online injection of gasoline samples (diluted 1:9 in hexane) into a carrier stream of 0.5% benzene in hexane; in this case the baseline corresponded to the max. benzene level in gasoline allowed by EC legislation. Samples with a benzene content higher than this upper limit gave positive peaks. The procedure was used to analyze a series of commercial gasoline samples and the results compared well with those of GC.
Benzene Oil Spectrophotometry

"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

"Multi-site Detection In Flow Analysis. 2. Monosegmented Systems With Relocating Detectors For The Spectrophotometric Determination Of Boron In Plants"
Anal. Chim. Acta 1993 Volume 276, Issue 1 Pages 121-125
Ana Rita A. Nogueira, Sandra M. B. Brienza and Elias A. G. Zagatto*, Jos&eacute; Luis F. Costa Lima and Alberto N. Ara&uacute;jo

Abstract: The feasibility of combining a relocating flow cell with a monosegmented continuous-flow system is presented and the limitations and advantages of detector relocation are outlined. The sample is injected with an air plug positioned at its tailing portion to minimize dispersion. After the peak maximum the detector is displaced allowing the air phase to be discarded. The system was used in the spectrophotometric determination of B in plants. Four samples were simultaneously processed at a sampling frequency of 120 h-1. The coefficient of variation were 3% and the results compared well with those from ICP-AES
Boron Plant Spectrophotometry

"Stopped-flow Kinetic Spectrophotometric Method For The Simultaneous Determination Of Iron, Titanium And Vanadium"
Anal. Chim. Acta 1993 Volume 276, Issue 2 Pages 419-424
Jianhuan Wang* and Ronghuan He

Abstract: The carrier solution was water (adjusted to pH 2.1 with HCl) containing 0.1% of starch; after injection of the sample it was mixed with 36 mM KI and then with 4.2 mM Cr(VI) and the rate of formation of the colored product was measured at 590 nm by taking measurements at 5, 10 and 20 s after injection. The calibration graphs were rectilinear up to 2.2, 3.1 and 1.8 µg mL-1 for Fe(II), Ti(III) and V(IV), respectively, and the corresponding detection limits were 12, 20 and 18 ng mL-1. Results for the determination of Fe, Ti and V in an aluminum alloy agreed well with those obtained by AAS; the coefficient of variation for each metal was ~4%. The effects of diverse ions on the determination are also reported.
Iron(2+) Titanium(III) Vanadium(IV) Alloy Spectrophotometry

"Flow Injection Spectrophotometric Enzymic And Non-enzymic Methods For The Determination Of Direct And Total Bilirubin In Serum"
Anal. Chim. Acta 1993 Volume 276, Issue 2 Pages 271-279
J. M. Fern&aacute;ndez-Romero, M. D. Luque de Castro* and M. Valc&aacute;rcel

Abstract: The first method involves an automatic flow injection system for the sequential determination of total and direct bilirubin based on catalytic oxidation (with bilirubin oxidase) of conjugated bilirubin in an acidic medium and the oxidation of unconjugated bilirubin in a basic medium. A stopped-flow system was used and the change in absorbance was measured at 460 nm. The calibration graph was rectilinear from 0.09 to 25 µM and from 0.14 to 13 µM for total and direct bilirubin, respectively. The second method is based on the differential reactivity (in an acidic medium) of conjugated and unconjugated bilirubin with Erlich reagent. Methanol was used as accelerator and the azorubin pigment formed was monitored at 560 nm. The calibration graph was rectilinear from 0.85 to 144 µM and from 3.8 to 125 µM for total and direct bilirubin, respectively. For both methods the coefficient of variation was 3%. No significant interference was found from substances commonly present in serum. Results agreed well with those obtained by an established conventional method.
Bilirubin, total Blood Serum Spectrophotometry

"Determination Of Nitrogen In Water: Comparison Of A Continuous-flow Method With Online UV Digestion With The Original Kjeldahl Method"
Anal. Chim. Acta 1993 Volume 276, Issue 2 Pages 287-293
Hennie Kroon*

Abstract: The water sample was mixed with K2S2O8 and Na2B4O7 buffer solution in a Skalar continuous-flow system and exposed to UV radiation. The NO3- formed was reduced with Cu-activated cadmium to NO2-, which was then treated with sulfanilamide and N-(1-naphthyl)ethylenediamine before absorbance measurement at 540 nm. Influents and effluents from sewage treatment plants were investigated, as well as surface waters and solution of (NH4)2SO4, glutamic acid, hexamine, urea and nicotinic acid. The coefficient of variation obtained at levels of 2 mg L-1 of N and up to 30 mg L-1 of N were 5 to 10% and 1.5 to 5%, respectively. No significant differences were found between results obtained by this method for surface and waste waters and those obtained by the conventional Kjeldahl method. Unlike the Kjeldahl method, the proposed method is suitable for waste waters of high NO3- content.
Nitrogen Waste Spectrophotometry Sample preparation

"Automated Determination Of Reducing Sugars By Atomic Absorption Spectrometry"
Anal. Chim. Acta 1993 Volume 276, Issue 2 Pages 385-391
M. C. Yebra, M. Gallego and M. Valc&aacute;rcel*

Abstract: Wine samples (0.25 to 1 ml) were diluted with water to 25 ml, the pH was adjusted to 4.6 to 8.2 with dilute KOH, and the sample was pumped into a reversed flow injection system. A portion (200 µL) of pre-mixed Fehling A and B solution was injected into the carrier stream and the sample - reagent plug was halted in a precipitation coil at 95°C for 10 min. The change in the Cu AAS signal with respect to a blank was then monitored after diluting the carrier stream with water. Reducing sugars could be determined in the range 10 to 110 µg mL-1 with a coefficient of variation (n = 11) of 2.7%; the recovery was close to 100%. Results are compared with those obtained by conventional methods.
Sugars, reducing Wine Spectrophotometry

"Comparison Of The Performance Of RP C18 On Silica And Polymeric Supports For The Liquid Chromatographic Separation Of Metal - Amino-acid Complexes With Post-column Derivatization"
Anal. Chim. Acta 1993 Volume 278, Issue 1 Pages 83-89
F. Baffi*, M. C. Ianni and E. Magi, M. Ravera

Abstract: The behavior of a complex formed between Cu and glycine was studied on Polysphere RP C18, HEMA RP C18 and Superpac-Spherisorb ODS-2 Dual Bond stationary phases. The best results were obtained using Superpac Dual Bond, as the Cu-glycine complex did not decompose as it did with the other stationary phases tested. The Cu-glycine complex was determined by a post-column derivatization procedure using o-phthalaldehyde at 50°C with eluent flow rate of 1-1.5 ml/min, derivatization reagent flow rate of 0.5 ml/min and fluorimetric detection at 530 nm (excitation 360 nm). The detection limit was 0.1 fmol. The method was applied to the determination of amino-acids.
HPLC Fluorescence

"Online Monitoring Of Penicillin V During Penicillin Fermentations: A Comparison Of Two Different Methods Based On Flow Injection Analysis"
Anal. Chim. Acta 1993 Volume 279, Issue 1 Pages 51-58
Morten Carlsen, Claus Johansen, Rong Wei Min and Jens Nielsen*, Helmut Meier and Francois Lantreibecq

Abstract: Two methods were compared for the cited analysis. In method (i), cell-free sample from the reactor (0.78 ml/min) was injected into a carrier stream of 10 mM phosphate buffer of pH 6.5 (1.1 ml/min) and mixed in the stirred 2 mL detection cell. The cell contained a rapid response glass electrode, on which β-lactamase had been immobilized, which measured the pH change caused by the hydrolysis of phenoxymethylpenicillin (I) to penicilloic acid. The β-lactamase reaction was also used in method (ii), but the penicilloic acid was detected by its bleaching of starch-iodine at pH 6. Using a second injector valve, the enzyme reactor was bypassed and the pre-existing penicilloic acid could also be measured. The first method was simpler, requiring no pre-dilution of the sample and could be used for routine determinations of 35 g/l of I. The second method required three dilution ranges to analyze 0.1-30 g/l of I, smaller samples (10 µL) and more frequent calibration. Both methods were used for continuous monitoring of 200 h production runs.
Penicillin V Fermentation broth Electrode

"Determination Of Amines By Flow Injection Analysis Based On Aryl Oxalate-sulforhodamine 101 Chemiluminescence"
Anal. Chim. Acta 1993 Volume 281, Issue 1 Pages 111-118
Masatoki Katayama*, Hideyuki Takeuchi and Hirokazu Taniguchi

Abstract: A 20 µL portion of amine was injected into a stream of aqueous 90% acetonitrile containing 0.02 M H2O2. The mixture was passed at 1.5 ml/min to a flow cell together with 0.5 mM bis-[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate and 0.1 µM-Sulforhodamine 101 in acetonitrile. The chemiluminescence was monitored by a photomultiplier tube. The detection limits of 55 amines were studied without derivatization; 28 were detected at levels of 0.1 nM to 4 µM, with linear calibration graphs up to 0.1 to 1 mM, respectively. The RSD for 1 µM-triethylamine was 4.8% (n = 6). The method was selective and sensitive for aliphatic amines and imidazoles, and the detection limits were lower than those obtained using derivatization-fluorimetry methods. The technique was applied to the determination of histamine in fish. The recovery was 94-96.2% and the results were comparable with those measured by a LC method using fluorescence detection after derivatization.
Amines, aliphatic Imidazoles Histamine Marine Chemiluminescence

"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

"Automated Determination Of Mercury At Ultratrace Level In Waters By Gold-amalgam Preconcentration And Cold Vapor Atomic-fluorescence Spectrometry"
Anal. Chim. Acta 1993 Volume 282, Issue 1 Pages 109-115
Chris C. Y. Chan and Ram S. Sadana

Abstract: Sample (25 ml) was heated with 1.2 mL of H2SO4, 0.5 mL of HNO3, 0.3 mL of 5% K2S2O8 solution and 0.3 mL of saturated K2Cr2O7 solution at 85-90°C for 2 h. The continuous-flow Hg-generation apparatus consisted of an autosampler, a peristaltic pump that propelled both the sample solution and the reducing reagent (4% SnCl2 solution in 10% HCl) at 3.9 ml/min, a gas-liquid separator that permitted the Hg vapor to be transferred to Ar carrier gas (20 ml/min), two moisture absorbers connected in series, and a six-port flow injection module that collected and transferred an portion of the gaseous Hg to a Au-wire absorber, which comprised a quartz tube (4 in. x 0.25 in. i.d.) wrapped with a Chromel wire heater and containing 0.5-1 g of Au wire (0.1-0.2 mm diameter). The Hg was desorbed by heating to ~500°C and carried to the spectrophotometer in an Ar stream (22 ml/min) for measurement at 253.7 nm. The calibration graph was linear up to 1 ng/ml and the detection limit was 2 pg/ml. The RSD (n = 10) for natural water containing 0.06 ng/ml of Hg was 3%. The procedure was applied to 11 water samples, and the results were confirmed by cold vapor AAS.
Mercury Environmental Fluorescence

"Determination Of Promethazine By Its Inhibition Of The Chemiluminescence Of The Luminol-hydrogen Peroxide-chromium(III) System"
Anal. Chim. Acta 1993 Volume 282, Issue 1 Pages 169-174
Abdulrahman A. Alwarthan, Saad A. Al-Tamrah and Akel A. Akel

Abstract: The FIA manifold is illustrated. A portion of 0.1 M Cr(III) is injected by a solenoid-activated rotary valve into a carrier stream of 1 mM luminol in 0.1 M sodium carbonate buffer of pH 10.5, and this stream merges with a stream of 0.01 M H2O2 and then with the sample solution stream (all flow rates 2.1 ml/min). The merged streams pass into a flow cell and the chemiluminescence signal is recorded with a photomultiplier tube. The log.-log. calibration graph is linear up to 0.1 mM promethazine, and the detection limit is 3 nM. The RSD (n = 10) at 10 µM-promethazine was 1.3%. Results for two pharmaceutical products agreed with those obtained by the B.P. method.
Promethazine Pharmaceutical Chemiluminescence

"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

"Determination Of Morphine In Process Streams Using Flow Injection Analysis With Chemiluminescence Detection"
Anal. Chim. Acta 1993 Volume 282, Issue 3 Pages 551-557
Neil W. Barnett and Douglas G. Rolfe, Tim A. Bowser and T. Walter Paton

Abstract: A previously described flow injection chemiluminescence method (cf., Abbott et al., Analyst, 1986, 111, 635) was modified for the cited analysis. Chemiluminescence-time profiles of morphine (I) were evaluated using a system based on the reaction of I and acidic KMnO4 in the presence of tetraphosphoric acid (details given). The method was applied to the determination of I during the full-scale process extraction of alkaloids from Papaver somniferum (opium poppies). The calibration graphs were linear from 3.5-350 µM-I, with a detection limit of 0.05 µM and a RSD of 0.4% (n = 10) at 0.14 mM. Pseudomorphine and oripavine did not interfere. Results obtained compared favourably with those obtained by HPLC.
Morphine Chemiluminescence

"Flow Injection Derivative Fourier Transform Infrared Determination Of Methyl T-butyl Ether In Gasolines"
Anal. Chim. Acta 1993 Volume 282, Issue 3 Pages 543-550
Miguel de la Guardia, M&aacute;ximo Gallignani and Salvador Garrigues

Abstract: Unleaded gasoline (10 ml) was diluted with n-hexane to 25 mL and a 320 µL portion of the solution was injected into a stream of n-hexane (0.45 ml/min). FTIR detection between 1350-800 cm-1, using a 0.117 mm path length flow cell with KBr windows, was performed and the first-order derivatives were calculated between 1209-1201 cm-1. Samples spiked with the cited compound (I) from 0.4-1.2% gave recoveries in the range 98.2-101.2%, with a RSD of 0.6% for samples containing 0.8% of I. The calibration graph was linear from 0.035% (limit of detection) to 1.5% of I in n-hexane and results (discussed) compared favourably with those obtained by GC.
Methyl-t-butylether Oil Spectrophotometry

"Kinetic Determination Of Cobalt And Nickel By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1993 Volume 283, Issue 1 Pages 476-480
M. A. Z. Arruda, E. A. G. Zagatto* and N. Maniasso

Abstract: For the simultaneous determination of Co and Ni, the slower decomplexation rate for the Ni/citrate complex as compared with the Co/citrate complex was exploited. A 500 µL plug of sample solution was transported by a carrier stream of 0.01 M HCl and merged with 0.1 M sodium tetraborate within a reactor coil. The stream was then treated with 0.01 M sodium citrate and 1 mM 4-(2-pyridylazo)resorcinol (PAR) within a 400 cm coil before the addition of 0.1 M Na2EDTA/0.01 M Na4P2O7 masking solution and passage through a further coil before spectrophotometry at 520 nm to give the sum of Co and Ni. By using a 100 µL sample plug and a 1 cm coil for the PAR reaction, the signal corresponded chiefly to the Co in the sample. For Co in tool steel, the system was simplified by increasing the flow rates and using a short reaction coil. Steel samples were decomposed by aqua regia at 160°C and the resulting solution were diluted with water and then diluted 1000-fold with 0.01 M HCl for analysis. In the determination of 2-5.24 mg/l of Co and 0.12-0.95 mg/l of Ni in solution of alloys, the RSD were 1-3.2% and 0.9-7%, respectively (n = 5). Results agreed well with those obtained by ICP-AES.
Cobalt Nickel Alloy Sample preparation Spectrophotometry

"Kinetic Flow Injection Spectrofluorimetric Method For The Determination Of Fluoride"
Anal. Chim. Acta 1993 Volume 283, Issue 1 Pages 489-493
V. Marco, F. Carrillo, C. P&eacute;rez-Conde and C. C&aacute;mara*

Abstract: The method was based on the ability of trace fluoride to increase the rate of formation of the Al/Eriochrome Red B (Mordant Red 7) complex. The sample (100 µL) containing up to 4 mg/l of fluoride was injected into a carrier stream containing 0.5 mg/l of Al (as the nitrate). This solution was mixed with a stream of 1.5 M hexamine buffer of pH 6 in a reaction coil and then with a stream of ethanolic 0.01% Eriochrome Red B in a further reaction coil maintained at 70°C. The resulting solution was passed through a cooling coil at 4°C before measurement of the fluorescence at 595 nm (excitation at 470 nm). The method showed good selectivity, but 1 mg/l of Fe(III) and 10 µM-phosphate interfered. Response was linear for 1 µM-20 mM fluoride and the detection limit was 10 ng/ml. The RSD at 50 and 100 µM was 7% and 4%, respectively (n = 10). Twenty samples could be analyzed in 1 h and the method was suitable for automation. The method was used to analyze tap and mineral waters; results were in fair agreement with those obtained by using a fluoride-selective electrode.
Fluoride Water Mineral Fluorescence

"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

"Comparative Studies Of The Determination Of Cyanide At Low Concentration Levels In Waste Waters"
Anal. Chim. Acta 1993 Volume 283, Issue 2 Pages 755-761
P. C. do Nascimento and G. Schwedt

Abstract: Off-line methods were based on the formation of a stable Ni-cyano complex in ammoniacal solution and subsequent determination by spectrophotometry, polarography or indirect AAS. The absorption spectrum of the Ni-cyano complex exhibited a maximum at 267 nm and Beer's law was obeyed over a wide range. The height of the polarographic wave at -1.35 V vs. Ag/AgCl was proportional to the cyanide (I) concentration in ammoniacal solution using a three electrode apparatus (Hg-dropping electrode, Ag/AgCl, vitreous C electrode), a drop time of 0.8 s per drop, a scan rate of 20 mV/s, a current range of 0.25 nA/mm and a pulse amplitude of 50 mV. For the indirect AAS method, the Ni-cyano complex was extracted into butanol and Ni was determined in the organic phase at 232 nm with an air-acetylene flame. The online determination of I by FIA, was performed by injecting the sample into a 0.01 M NaOH/0.01 M KNO3 of pH 11 carrier stream (1.2 ml/min) and measuring the I with an ISE. The detection limits, linear ranges, precision, recoveries and analysis times of the four methods were compared (details given). The online FIA method was the simplest and most rapid method with a detection limit of 60 µg/l of I.
Cyanide Waste Electrode Polarography Spectrophotometry

"Flow Injection Analysis - Wall-jet Electrode System For Monitoring Glucose And Lactate In Fermentation Broths"
Anal. Chim. Acta 1993 Volume 283, Issue 2 Pages 763-771
Yu Liang Huang, Soo Beng Khoo, Miranda G. S. Yap

Abstract: The flow injection manifold consisted of two peristaltic pumps, an injection valve with a 20 µL sample loop, an enzyme reactor column (10 x 1 mm i.d.) containing either glucose oxidase or lactate oxidase immobilized onto controlled-pore glass beads, and a large volume wall-jet detector cell. The detector contained a Pt disc working electrode modified with Fe(II), a Ag/AgCl reference electrode and a vitreous C counter electrode. Fermentation broth was centrifuged and the supernatant was diluted prior to analysis. The resulting solution was injected into the 0.1 M potassium phosphate buffer of pH 7 carrier stream (0.5 ml/min). The H2O2 produced by the enzymatic reaction of both glucose (I) and lactose (II) was detected at 0.65 V vs. Ag/AgCl. The calibration graphs were linear up to 0.5 and 0.04 g/l of I and II, respectively. The RSD (n = 54) was 3% over a 10 h measurement period. The procedure was used to monitor I and II concentrations in various fermentation broths and the results agreed well with those obtained using a commercial I-II analyzer..
Glucose Lactate Fermentation broth Electrode

"Off-line And Online Preconcentration Of Trace Levels Of Beryllium Using Complexing Agents With Atomic-spectrometric And Fluorimetric Detection"
Anal. Chim. Acta 1993 Volume 283, Issue 2 Pages 909-915
D. B. Do Nascimento and G. Schwedt

Abstract: Two methods were investigated. The first method used polyethylene powder as an adsorbent for the pre-concentration of the stable complex formed between Be and Chrome azural S (CAS; C. I. Mordant Blue 29) followed by analysis by graphite-furnace AAS (GF-AAS). The sample solution was adjusted to pH 3 with HCl and treated with 0.5 M succinic acid buffer solution of pH 4.5 and 6% aqueous CAS. The mixture was passed (0.5 ml/min) through the pre-concentration column containing polyethylene powder. After washing the column with water and drying in air, the Be-CAS complex was eluted with ethanol (0.4 ml/min). The eluate were analyzed by GF-AAS at 239.4 nm, with Ar purge gas (temp. programming details given). The method was used to determine Be in tap water. The detection limit was 0.8 µg/l of Be and the RSD were 2.5-4.1%. Recoveries were 92-104%. The second method (details given) used an ion-exchange micro-column in a FIA system for the pre-concentration of Be, which was reacted with morin and detected by fluorescence. The method was also used to determine Be in tap water. The detection limit was 0.2 µg/l of Be and the RSD was ~1.5%. Recoveries were 95-105%.
Beryllium Water Ion exchange Fluorescence Spectrophotometry

"Continuous-flow Method For The Determination Of Total Inorganic Carbonate In Water"
Anal. Chim. Acta 1993 Volume 284, Issue 1 Pages 167-171
Toyoaki Aoki*, Yoshiko Fujimaru, Yuko Oka and Kimiko Fujie

Abstract: Water (5.1 ml/min) was mixed with 0.5 M H2SO4 (1.5 ml/min) and the mixture passed into a membrane separation unit (cf. Anal. Chem., 1983, 55, 1620). The CO2 liberated by acidification permeated through a microporous PTFE tubular membrane (50 cm x 1 mm i.d.) and was collected in a stream of 5 mM NaOH (1.5 ml/min) flowing through an outer PTFE tube (3 mm i.d.). The total inorganic carbonate was determined from the change in electrical conductivity of the NaOH collector stream which was measured using two conductivity detectors; one placed before the membrane separator and one located after it. The calibration graph (relative electrical conductivity vs. concentration) was linear for 0.05-5 mM total inorganic carbonate with a detection limit of 10 µM and RSD (n = 5) of 3.4 and 1.8% at 0.1 and 0.6 mM carbonate, respectively. The response time (98% of steady-state signal) was ~2 min. The effects of various foreign ions were investigated; sulfite interference was prevented by the addition of 0.1 M Cr(VI) to the acid reagent. The method was applied to lake water and the results agreed well with those obtained by nondispersive IR.
Carbonate Lake Conductometry

"Single-phase Liquid-liquid Extraction In Mono-segmented Continuous-flow Systems"
Anal. Chim. Acta 1994 Volume 285, Issue 3 Pages 287-292
Ileana Facchin, Jos&eacute; W. Martins, Patr&iacute;cio G. P. Zamora and Celio Pasquini*

Abstract: The method depends on mixing an aqueous sample solution, an immiscible reagent solution and a common solvent for the other two phases. Reaction occurs rapidly in the single phase, which is then air-segmented and carried to a confluence with an aqueous solution, causing separation of the reagent phase for subsequent spectrophotometric measurement. The method was illustrated by the extraction of Fe(III). The sample solution was mixed with 50 mM thenoyltrifluoroacetone solution in isobutyl methyl ketone and with ethanol in a mixing chamber. The single-phase solution passed through a debubbler, then through a loop, where it was segmented between two air bubbles. A water stream carried the segment to a junction with saturated NaNO3 solution and phase separation occurred in an inverted U-tube. The complex in the organic phase was detected with light from a light-emitting diode (560 nm) passing through the liquid to a light-dependent resistor, which formed one arm of a wheatstone bridge. Calibration graphs were linear for 2-30 mg/l of Fe(III). The RSD was 1.5% (n = 10) for 10 mg/l. The results were similar to those obtained by manual extraction. Up to 80 samples/h could be processed.
Iron(III) Spectrophotometry Sample preparation

"Determination Of Traces Of Calcium And Magnesium In Rare-earth Oxides By Flow Injection Analysis"
Anal. Chim. Acta 1994 Volume 295, Issue 1-2 Pages 151-157
Duong Thanh Thuy, Dini Decnop-Weever, Win Th. Kok*, Pham Luan and Tu Vong Nghi

Abstract: Rare-earth oxides were dissolved in 15% HCl, the acid was evaporated off and the residue was dissolved in 10 mM HCl. The resulting solution was injected into a 10 mM HCl carrier solution and transported to a column (8 cm x 4 mm i.d.) packed with Chelex 100 resin (50-100 mesh, H+ form). The eluate merged with 7.5 µM-calcein solution in 0.2 M KOH in a PTFE mixing coil (20 cm x 1 mm i.d.). Fluorescence was measured at 515 nm (excitation at 300 nm) and the sum of Ca(II) and Mg(II) was determined. For the determination of Ca(II) alone, the column eluate was mixed with 5 mM 8-quinolinol in 10 mM KOH and for the determination of Mg(II) alone, the masking solution was 0.5 mM EGTA in 10 mM KOH. All flow rates were 1 ml/min. Calibration graphs for both cations were sigmoid for 1-20 µM with a linear portion at 2-12 µM. The method was applied to the analysis of La2O3, Pr2O3, Nd2O3, Sm2O3 and Gd2O3. The results of four synthetic samples agreed well with those predicted for the single metals; the sum was underestimated if the Mg(II) concentration was high. Two samples of La2O3 were also analyzed, giving results in fair agreement with those obtained by ICP-AES.
Calcium(2+) Magnesium(II) Inorganic compound Inorganic compound Inorganic compound Inorganic compound Inorganic compound Sample preparation Fluorescence

"Comparison Of The Analytical Capabilities Of An Amperometric And An Optical Sensor For The Determination Of Nitrate In River And Well Water"
Anal. Chim. Acta 1994 Volume 299, Issue 1 Pages 81-90
Margaret A. Stanley, Joe Maxwell, Mairead Forrestal, Andrew P. Doherty, Brian D. MacCraith, Dermot Diamond and Johannes G. Vos

Abstract: The analysis of nitrate in water has been studied using novel amperometric and optical sensors. A flow-injection analysis system with amperometric detection has been developed in which nitrate is determined as nitrite after reduction in a cadmium column. The working electrode is glassy carbon modified with a crosslinked redox polymer. The linear range is 0.1 to 190 mg/l NO3-N (r>>0.999) and the limit of detection (LOD) is 50 µg/l NO3-N. A fiber optic sensor based on a dual wavelength absorption approach has also been developed. A signal at 210 nm where nitrate absorbs was referenced against a signal at 275 nm where nitrate does not absorb. Its linear range is from 0.4 to 30 mg/l NO3-N and its LOD is 400 µg/l NO3-N. These diverse methods have been applied to the analysis of the same river water samples and good correlations have been observed between the two measurement techniques and a standard ion chromatography method.
Nitrate River Well Amperometry Sensor

"Application Of Enzyme Field-effect Transistor Sensor Arrays As Detectors In A Flow Injection System For Simultaneous Monitoring Of Medium Components. 2. Monitoring Of Cultivation Processes"
Anal. Chim. Acta 1995 Volume 300, Issue 1-3 Pages 25-31
T. Kullicka, U. Bocka, J. Schuberta, T. Scheperb and K. Sch&uuml;gerla,*

Abstract: A biosensor array consisting of a single pH-FET and seven enzyme FET channels integrated into a single flow injection system was used for the online monitoring of pH, glucose, maltose, sucrose, lactose, ethanol and urea during the cultivation of Escherichia coli and Saccharomyces cerevisiae in synthetic media. The components were monitored using glucose dehydrogenase, maltase-glucose dehydrogenase, invertase-glucose dehydrogenase, β-galactosidase-galactose dehydrogenase, alcohol dehydrogenase-aldehyde dehydrogenase and urease (co)immobilized on the pH sensitive gates of the FET. The array was integrated in a commercial FIA system. The results agreed with those obtained by offline concentration measurements.
Ethanol Glucose Lactose Maltose Sucrose Urea Fermentation broth Field effect transistor Field effect transistor Sensor

"Online Monitoring Of D-lactic Acid During A Fermentation Process Using Immobilized D-lactate Dehydrogenase In A Sequential Injection Analysis System"
Anal. Chim. Acta 1995 Volume 300, Issue 1-3 Pages 277-285
Hun-Chi Shu, H&aring;kan H&aring;kanson and Bo Mattiasson*

Abstract: A PC-automated sequential injection analysis (SIA) system was used to monitor the production of D-lactic acid during the batch fermentation of Lactobacillus delbrueckii ATCC 9649. Sampling was carried out from the flux of a cellulose acetate membrane filtration unit through which the broth was continuously circulated. Cell-free permeate was diluted with 0.1 M phosphate buffer of pH 7 and passed through rotary and three-way valves to enzyme and blank reactors. The enzyme reactor contained D-lactate dehydrogenase co-immobilized with L-alanine aminotransferase on porous glass. The measuring conditions were: 0.1 M glycylglycine buffer including 70 mM glutamic acid as carrier buffer of pH 10, 4 mM NAD+ cofactor in glycylglycine buffer solution and an incubation time of 90 s. Detection was by spectrophotometric absorbance measurement (340 nm for NADH). The total analysis time was 182 s including the incubation time while the flow was stopped. The calibration graph was linear in the range 2-25 mM D-lactic acid and the detection limit was 1 mM. The results from SIA were comparable with those obtained by the offline Boehringer enzymatic kit method.
d-Lactic acid Fermentation broth 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

"Inductively Coupled Plasma Mass-spectrometric Determination Of Gold In Serum: Comparison With Flame And Furnace Atomic Absorption Spectrometry"
Anal. Chim. Acta 1995 Volume 304, Issue 3 Pages 317-321
Masahito Higashiura*, Hiroshi Uchida, Tetsuo Uchida and Hiroko Wada

Abstract: Three analytical methods for the determination of gold in the serum of rheumatoid patients have been compared, i.e., flame and graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) with the respective detection limits of 30, 1.0 and 0.01 ng mL-1. The stability of gold solutions was also investigated. With 0.1% Triton X-100 and 0.1 M hydrochloric acid the gold concentration at ng mL-1 levels in standards was constant for 4 days, and the levels in 2000-fold diluted serum were the same for at least 7 days. The analytical results obtained with the above three methods correlated quite well, however, ICP-MS was the best technique, because of its specificity, sensitivity, wide dynamic range, speedy and ease of measurement.
Gold Blood Serum Mass spectrometry Spectrophotometry Spectrophotometry

"Simultaneous Flow Injection Determination Of Nitrate And Nitrite In Water By Gas-phase Chemiluminescence"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 308-312
Toyoaki Aoki* and Muneki Wakabayashi

Abstract: A flow injection procedure for the determination of nitrate (I) and nitrite (II) based on their reduction to NO followed by membrane phase separation and chemiluminescence detection was developed. Reductant was injected into a 0.5 M H2SO4 carrier stream (0.5 ml/min) which was merged with streams of sample solution (0.5 ml/min) and clean air (6 ml/min). After passing through a mixing coil (2 m x 1 mm i.d.), the mixture was propelled to the phase separator. The separator comprised an outer PTFE tube (4 mm i.d.) and an inner porous PTFE tube (2 mm i.d.). Air and NO permeated through the microporous membrane into a clean air stream and were swept to the chemiluminescent analyzer. (CL) where the chemiluminescence produced by with ozone was monitored. A Nafion permeation tube removed moisture. The reductant was 20% Ti(III) for the combined determination of I and II and 5% KI for the determination of II. The calibration graphs were linear for 5 µg N/l (I) and 3 µg N/l (II) to ~e;1 mg N/l. The detection limits were 0.7 ppb I and 0.35 ppb II. RSD (n = 5) were 1.2% for 0.7 ppm I and 1.4% for 0.28 ppm II. The method was used to determine I and II in river water and sewage effluent. The results agreed with those obtained by conventional methods (details given).
Nitrate Nitrite Effluent River Chemiluminescence

"Determination Of Metal Ion Mixtures Using PH Gradient Flow Injection Analysis With Fluorescence Detection"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 313-328
N. Porter*, B. T. Hart, R. Morrison and I. C. Hamilton

Abstract: A pH gradient flow injection system with fluorimetric detection was described for the analysis of ternary and quaternary mixtures of Zn, Cd, Pb, Mg and Al. The pH gradient was formed by injecting a basic buffer solution into an acidic buffer stream. Four different buffer systems were used. For each system the pH variable buffer stream was merged with 0.1 mM 8-hydroxyquinoline-5-sulfonic acid and sample streams. The flow then passed through a knotted PTFE mixing coil (30 cm x 0.5 mm id.) and a column (18 cm x 2.5 mm i.d.) containing 0.25 mm glass beads to the detection cell (90 µL) where the metal chelates were monitored at 520 nm (excitation at 369 nm). All measurements were carried out in triplicate with each run taking 60 s. The fluorescence-time scans were analyzed by a partial least squares algorithm. The dynamic range of the method was 0.1-10 µM for Zn, Cd, Al and Mg. The method was used to analyze tap water. The results were comparable to those obtained by AAS.
Aluminum Cadmium Lead Magnesium Zinc Water Fluorescence

"Vapor Generation Fourier Transform Infrared Spectrometry. A New Analytical Technique"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 28-35
Emilio L&oacute;pez-Anreus, Salvador Garrigues and Miguel De La Guardia

Abstract: A single channel manifold for the generation of vapors for FTIR measurements is described. The liquid samples were injected into an electrically heated Pyrex glass reactor of 2.5 mL volume and evaporated at a controlled temperature. The vapors were then into the IR gas cell by a N2 carrier gas. The methodology was adapted to determine ethanol in CHCl3. A sample volume of 25 µL was injected into the reactor which was maintained at 90°C. The N2 carrier gas at 410 ml/min swept the volatiles into the detector cell where the absorbance peaks of ethanol and CHCl3 at 1066 and 931 cm-1, respectively, were monitored. A linear calibration graph was obtained (range not given) and the detection limit for ethanol in CHCl3 was 0.02% (v/v). The results obtained for the analysis of commercial samples of CHCl3 stabilized with ethanol were comparable to those produced by a reference procedure based on flow injection - NIR analysis.
Ethanol Organic compound Spectrophotometry

"Sequential Enzymic Monitoring Of Glucose, Ethanol And Glutamate In Bioreactor Fermentation Broth Containing A High Salt Concentration By A Multi-channel Flow Injection Analysis Method"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 145-151
Richie L. C. Chen and Kiyoshi Matsumoto*

Abstract: An automated glucose analyzer. was modified to form a multichannel FIA system for the sequential determination of glucose, ethanol and glutamate. The modifications consisted of inserting a computer controlled column switching valve downstream from the injector. Each channel was equipped with a mini-reactor column containing immobilized glucose oxidase, alcohol oxidase or glutamate oxidase. The product from the enzyme reactions, H2O2, was detected electrochemically. The carrier solution (3 ml/min) was 0.1 M phosphate buffer of pH 6.8 and the injection volume was 2 µL for each determination. The apparatus was evaluated by monitoring the fermentation of a fish sauce with Torulopsis versatiles immobilized beads. Due to the high salt concentration in the fermentation broth it was necessary to insert a Dowex 1-X8 anion-exchange column between the injector and the column switching valve to eliminate the interference of NaCl. Linear calibration graphs were obtained for 0.5-5% (w/v) glucose and ethanol and 0.1-2% (w/v) glutamate. The results were confirmed by analysis with assay kits.
Ethanol Glucose Glutamate Fermentation broth Electrochemical analysis

"Determination Of Iron And Zinc In Adipose Tissue By Online Microwave-assisted Mineralization And Flow Injection Graphite-furnace Atomic Absorption Spectrometry"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 349-356
J. L. Burguera, M. Burguera, P. Carrero, C. Rivas, M. Gallignani and M. R. Brunetto

Abstract: An automated procedure for the determination of Fe and Zn in adipose tissue by GFAAS was developed incorporating online microwave-assisted mineralization. A mineralization tube was filled with H2SO4/HNO3 (4:1) of acidity 1-2 M and a ~e;20 mg portion of lyophilized tissue was added. The tube was exposed to microwave radiation (40 W) for 10 x 1 s periods with alternating 5 s rest periods. After mineralization, the acid solution was propelled at 2 ml/min to a PTFE collector tube and mixed with Triton X-100 solution to give a final concentration of 0.02% and Pd/Mg matrix modifier. Portions of this mixture were deposited on the graphite platform of the AAS. Fe and Zn were determined at 248.3 and 213.9 nm, respectively, with pyrolysis/atomization temperatures of 1000/2800°C for Fe and 700/2700°C for Zn. The linear range was 5-50 µg/l for Fe and 5-20 µg/l for Zn and the detection limits were 20 and 30 pg, respectively. The results were confirmed by flame AAS following liquid-liquid extraction of the metal chelate.
Iron Zinc Adipose Spectrophotometry Sample preparation

"Routine Assay Of Creatinine In Newborn Baby Urine By Spectrophotometric Flow Injection Analysis"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 446-450
Tadao Sakai*, Hiroshi Ohta, Noriko Ohno and Junzo Imai

Abstract: An FIA method based on the Jaffe reaction was described for the determination of creatinine in urine. Urine was collected on a soft adsorbent cotton pad. The soaked pad was wrung to recover 0.5 mL urine. The urine sample was diluted with 4.5 mL 0.03 M KH2PO4 containing 0.4% EDTA (carrier solution). A 100 µL portion of this solution was injected into the carrier stream (0.82 ml/min) which was merged with the reagent stream (0.82 ml/min) containing 0.01 M sodium picrate in 1.5% NaOH. The flow passed through the reaction coil (1.5 m x 0.5 mm i.d.) at 50°C to the detector where the absorbance was measured at 515 nm using a 10 mm pathlength flow cell. The calibration graph was linear for 5-200 µg/ml of creatinine with a detection limit of 3 µg/ml. The RSD (n = 10) for the determination of 50 µg/ml creatinine was 0.6%. The results were consistent with those obtained by a batchwise experiment and LC.
Creatinine Urine Spectrophotometry

"Construction And Use Of A Tubular Picrate Ion-selective Electrode For Reducing Sugar Determination In Port Wine By Flow Injection Analysis"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 122-128
Teresa I. M. S. Lopesa, Ant&oacute;nio O. S. S. Rangela,*, Jos&eacute;L. F. C. Limab and M. Concei&ccedil;&atilde;o B. S. M. Montenegrob

Abstract: An FIA system equipped with a picrate ISE was described for the determination of reducing sugars in port wine. The determination was based on the reaction between the reducing sugars and picric acid and the measurement of the decrease in the picrate concentration by a tubular, flow-through detector. A 150 µL volume of wine was injected into a 0.045 M picric acid carrier stream (0.7 ml/min) which was merged with a 1.8 M NaOH stream (0.2 ml/min). After passing through a thermostatted water bath at 58°C, the flow was merged with a 1 M H2SO4 stream (0.2 ml/min). The flow passed through a 100 cm mixing coil to the detector. The calibration graph was linear for 25-200 g/l of reducing sugars and the RSD were 3.9%. The sampling frequency was ~e;50 samples/h. The results obtained for samples containing 98-148 g/l of reducing sugars were in agreement with those obtained by an iodometric reference method.
Sugars, reducing Port Wine Electrode Electrode

"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

"Multicommutation In Flow Analysis. 2. Binary Sampling For Spectrophotometric Determination Of Nickel, Iron And Chromium In Steel Alloys"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 397-405
Patricia B. Martellia, Boaventura F. Reisb,*, Eloisa A. M. Kronkab, Henrique Bergamin b, Mauro Kornc, Elias A. G. Zagattob, Jos&eacute;Luis F. C. Limad and Alberto N. Araujod

Abstract: FIA methods are described for the spectrophotometric determination of (i) Ni with dimethylglyoxime as chromogenic reagent and (ii) Fe and Cr with salicylic acid and diphenylcarbazide as chromogenic reagents, respectively, in acid solutions of steel alloys. Control software written in QuickBasic 4.6 controlled all steps involved in the multicommutation processes. Samples and reagents were inserted into the carrier stream as a series of slugs. For i seven slugs of sample solution of 5.6 µL each were inserted into a carrier stream (28 µL/s) of 3% triethanolamine in 0.5 M NaOH. Ten slugs of 10% potassium peroxodisulfate solution (5.6 µL) and 14 slugs of 1% dimethylglyoxime solution (98.4 µL) were added. The mixture was propelled to the detection cell where the absorbance was measured at 460 nm. For ii a carrier stream (2 ml/min) of 0.5 M HCl was used with 2.8% salicylic acid or 0.06% diphenylcarbazide. Sample slugs were inserted alternatively with reagent slugs to give sample/reagent ratios of 1:1. The consumption of reagent for each determination was 80 µL for Fe and 26 µL for Cr. The detector was operated at 540 nm for the determination of both Fe and Cr. The methods were tested by analyzing various steel alloy and comparing the results with those obtained by AAS or ICP-AES. The sampling frequency was 60 samples/h for Ni determinations and 110 samples/h for Fe and Cr determinations.
Chromium Iron Nickel Alloy Spectrophotometry

"Application Of Photoacoustic Spectrometry To Flow Injection Analysis"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 20-27
I. Carrer, P. Cusmai, E. Zanzotter, W. Martinotti,* and F. Realini

Abstract: The cited method was used to determine nitrite, nitrate, Fe, NH3 and phosphate ions in water. Excitation was performed with a Q-switched Nd:YAG laser equipped with a 2nd harmonic generator for the determination of nitrite, nitrate and Fe at 532 nm. The same laser was used to pump the dye laser for the detection of NH3 at 632 nm and phosphate at 810 nm. The generated acoustic wave was detected by an acoustic transducer. The FIA manifold allowed the sample solution to be injected into a water carrier stream which was merged sequentially with two reagent streams (R1 and R2) before passing to the detector cell. For the determination of nitrite, R1 and R2 were NH3 buffer and α-naphthylethylenediamine dihydrochloride. The same reagents were used for the determination of nitrate by incorporating a copperized Cd reduction column to reduce nitrate to nitrite. R1 and R2 were hydroxylamine hydrochloride and 1,10-phenanthroline, respectively, for the determination of Fe and ammonium molybdate and antimony potassium tartrate, respectively, for the determination of orthophosphate. The Berthelot reaction was used for the detection of NH3. The detection limits (tabulated) were comparable with those obtained by FIA with spectrophotometric detection for Fe, NH3 and phosphate. For nitrite and nitrate poorer detection limits were obtained.
Ammonia Iron Nitrate Nitrite Phosphate Environmental Spectrometry Sensor

"Determination Of Cadmium In Fertilizers By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 439-445
Jos&eacute;Anchieta Gomes Neto, H. Bergamin, Elias Ayres G. Zagatto* and Francisco J. Krug

Abstract: The flow injection procedure for the determination of Cd in fertilizers was based on the formation of the blue ternary complex between Cd, iodide and Malachite Green (MG). The fertilizer solution was injected into a 0.05 M HNO3 carrier stream (3.2 ml/min) using a 150 cm sampling loop. The stream was successively merged with reagents R1, R2 and a previously mixed stream of reagents R3 and R4. R1 was 0.01 M picolinic acid in 0.6 M sodium acetate/0.1 M acetic acid buffer at 0.4 ml/min. R2 was 200 µg/l Cd in 0.05 M HNO3 at 0.8 ml/min. R3 was 2 M KI in 5 mg/ml ascorbic acid solution at 0.4 ml/min and R4 was 0.5 M MG at 0.4 ml/min. The formed ternary complex was propelled to the detector where the absorbance was measured at 690 nm. The calibration graph for Cd was linear for up to 200 µg/l and the detection limit was 2 µg/l. The RSD (n = 10) for the determination of 93 and 35.3 µg/l of Cd were 1.3 and 4%, respectively. Interfering ions (Hg2+, Ag+, Cu2+ and Pb2+) were removed by inserting a Chelex-100 ion exchange column (5 cm x 3 mm i.d.; 50-100 mesh) into the sample stream. The sampling frequency was 60 samples/h. The results were confirmed by tungsten coil-AAS.
Cadmium Commercial product Lobster Vegetable Spectrophotometry

"Determination Of Enzyme Substrates With An Extended Range Of Linearity"
Anal. Chim. Acta 1995 Volume 309, Issue 1-3 Pages 251-258
Yun-Sheng Hsieh and S. R. Crouch*

Abstract: Portions of 1 mL of L-methionine, L-phenylalanine and L-tryptophan were mixed with 1 mL of a solution comprising 5 mL 10.7 mM 3,5-dichloro-2-hydroxyphenyl sulfonic acid, 10 mM KCl, 10 mg L-amino-acid oxidase, 16 mg horseradish peroxidase and 40 mL 100 mM phosphate buffer (pH not given). The oxidative deamination of the L-amino-acids was monitored at 510 nm and the data modelled to a one-compartment kinetic model using a commercial non-linear statistical software package. Similar reactions were performed using air-segmented continuous and stopped-flow analysis as described previously (Ibid., 1994, 296, 333). The accuracy and precision of the model were not significantly different with 95% confidence in comparison with the Michaelis-Menten model and double-reciprocal plots.
Amino acids, L l-Methionine l-Phenylalanine l-Tryptophan Spectrophotometry

"Batch Square-wave Voltammetric And Flow Injection Amperometric Determination Of Trace Amounts Of Bromofenoxim"
Anal. Chim. Acta 1995 Volume 310, Issue 1 Pages 153-160
Xiaohua Cai, Bozidar Ogorevc*, Emilio Benfenati, Kurt Kalcher, Milko Novic and Irena Grabec

Abstract: Voltammetric measurements were performed using a static Hg drop electrode, a Ag/AgCl/KCl (saturated) reference electrode and Pt-wire counter electrode. Cyclic voltammograms of bromofenoxim (I) in Britton-Robinson (BR) buffer of pH 7 were obtained at 200 mV/s. Two well defined reductive peaks were observed at -0.38 and -0.54 V. The peak at -0.38 V was used for subsequent measurements of I. For analysis by square-wave voltammetry, the calibration graph was linear for 0.0011-1.3 µM-I and the detection limit was 0.1 µg/l. The in situ formation and dynamic properties of Hg film-coated glassy C electrodes for the determination of I by FIA were investigated; 0.5 M KNO3/20 mM BR buffer of pH 7 was used as carrier and amperometric detection was at -0.7 V vs. Ag/AgCl. The response was linear for 0.11-9 µM-I with a detection limit of 10 µg/l. The RSD (n = 25) was 3.2%.
Bromofenoxim Amperometry Electrode Voltammetry

"Applications Of A Slotted Tube Atom Trap And Flame Atomic Absorption Spectrometry: Determination Of Bismuth In Copper-based Alloys With And Without Hydride Generation"
Anal. Chim. Acta 1995 Volume 311, Issue 1 Pages 93-97
D. Thorburn Burns*, Narong Chimpalee and Michael Harriott

Abstract: Improved systems are reported for the determination of bismuth (0-0.1%, w/w) in copper-based alloys by flame atomic absorption spectrometry. The use of a slotted quartz tube atom trap (STAT) with nebulised solutions or coupled with hydride generation decreases the characteristic concentrations (nebulized solution, 0.44/0.25, without/with STAT; hydride, 0.022/0.014, without/with STAT) and improved precisions by factors of two compared with those obtained without the use of the STAT. Determination of bismuth in a series of reference materials demonstrates the usefulness of STAT systems for the analysis of metallurgical samples.
Bismuth Alloy Spectrophotometry

"Evaluation Of Flow Injection Methods For Ammonium Determination In Waste Water Samples"
Anal. Chim. Acta 1995 Volume 311, Issue 2 Pages 165-173
A. Cerd&agrave;, M. T. Oms, R. Forteza and V. Cerd&agrave;*

Abstract: Five flow injection methods, namely (i) the Berthelot reaction adapted to FIA, (ii) the Berthelot reaction in combination with gas diffusion separation, (iii) the salicylate modification of the Berthelot reaction, (iv) an acid-base spectrophotometric method with gas diffusion separation and (v) gas diffusion separation with conductivity detection, were compared for the determination of ammonia in waste water. The linear range, detection limit and reproducibility of each method were measured. All methods produced a detection limit (0.03-1 mg/l) which was satisfactory for the determination of ammonia in waste water. Interferences were eliminated by using gas diffusion separation. Gas diffusion methods coupled with spectrophotometric or conductometric detection were found to have good precision and sensitivity and were reliable alternatives to the Berthelot methods. The conductivity method had the added advantage of requiring only one reagent (NaOH). Methods based on the Berthelot reaction required a reaction temperature of 60°C which made them unsuitable for in situ applications. All five method were applied to the analysis of waste water samples containing 5-60 mg/l ammonia and the results were compared.
Ammonium Waste Conductometry Spectrophotometry

"Online Flow Injection Monitoring Of Ammonia In Industrial Liquid Effluents"
Anal. Chim. Acta 1995 Volume 314, Issue 1-2 Pages 33-43
Kevin N. Andrewa, Paul J. Worsfolda,* and Michael Comberb

Abstract: A portable, automated flow injection monitor was developed for the online determination of NH3 in industrial liquid effluent streams. The monitor was based on the diffusion of gaseous NH3 from an alkaline sample stream through a PTFE membrane into a bromothymol blue indicator stream and the photometric measurement of the resulting color change using a red LED (λmax = 635 nm). The effluent stream (1.3 ml/min) was mixed with a 0.01 M NaOH stream (1.3 ml/min) and a 20 µL volume of the mixture was injected into a water carrier stream (1.2 ml/min) and passed through the gas diffusion cell. The gas diffusion cell was equipped with a PTFE membrane (thickness 8-9 µm, 24 cm x 15 mm) and had a volume of 72 µL on either side of the membrane. I diffused through the membrane into a 0.1 g/l bromothymol blue stream (1.4 ml/min) and was carried to the detection cell. Calibration was carried out using two standard solution containing 2 and 80 mg/l NH3-N. The calibration graph was linear from 1-100 mg/l NH3-N and the detection limit was 0.6 mg/l. RSD (n = 10) were 3.4 and 0.7%, respectively, for the determination of 2 and 80 mg/l NH3-N. The performance of the monitor was evaluated at two industrial sites and the results were confirmed by an indophenol blue laboratory reference method.
Ammonia Industrial Spectrophotometry

"Quantitative Analysis Of Sulfadiazine Using Photochemically Induced Fluorescence Detection In Bulk Solution And In A Flow Injection System"
Anal. Chim. Acta 1995 Volume 314, Issue 1-2 Pages 45-50
J. J. Aaron,*, M. I. Acedo Valenzuela, M. Sanchez Pena, F. Salinas and M. C. Mahedero

Abstract: Room temperature photochemically-induced fluorescence methods were described for the determination of sulfadiazine (I). For the bulk solution method, portions of a standard solutions of I in 50% aqueous methanol were transferred to a 1 cm quartz cuvette and irradiated with a high-pressure mercury lamp for 2.5 min. The fluorescence intensity was then measured at 353 nm (excitation at 295 nm). The calibration graph was linear from 0.1-4.1 µg/ml of I and the detection limit was 40 ng/ml. The RSD (n = 10) was 1.7% for 2.6 µg/ml of I. For the FIA method, 300 µL of a standard solution containing 0.2-6.5 µg/ml of I was injected into a water carrier stream (4.2 ml/min) and passed through a photoreactor (length 250 cm) to the detector cell. The fluorescence intensity was measured at 352 nm (excitation at 295 nm). A linear calibration graph was obtained and the detection limit was 27 ng. The RSD (n = 10) was 2.1% for 2.1 µg/ml of I. The methods were applied to the determination of I in pharmaceutical preparations using a standard additions calibration procedure. Results agreed well with those obtained by an HPLC method.
Sulfadiazine Pharmaceutical Fluorescence

"Determination Of Phosphorus In Turbid Waters Using Alkaline Potassium Peroxodisulphate Digestion"
Anal. Chim. Acta 1995 Volume 315, Issue 1-2 Pages 123-135
L. Woo and W. Maher*

Abstract: The evaluation of the use of alkaline peroxodisulphate digestion with autoclaving or microwave heating for the determination of total phosphorus in turbid lake and river water is described. Procedures were evaluated by the analysis of suspensions (20, 50 and 100 g P/l) of two standard reference materials, National Institute of Environmental Science, Japan No. 3 Chlorella and No. 2 Pond Sediment. Suspensions were prepared by adding these materials to distilled deionized water (pH 6) and homogenisation using shaking, sonification and stirring. Best recoveries of phosphorus were found when the final solution was 0.045 M in potassium peroxodisulphate and 0.04 M in sodium hydroxide and solutions digested in an autoclave at 120°C for 60 min. or heated in a microwave oven at 450 W for 10 min. Complete recoveries of phosphorus (99-103%) from 20, 50 and 100 g P/l Chlorella suspensions were obtained using both autoclave and microwave heating. For the Pond Sediment complete recoveries of phosphorus (99-107%) from the 20 and 50 g P/l suspensions were obtained using both heating methods. Higher recoveries from the 100 g P/l Pond Sediment suspensions were obtained using microwave heating (96 ± 1%) than autoclaving (88 ± 5%). Recoveries of phosphorus compounds (phosphates, and phosphonates) added to distilled deionized water and turbid lake water were near quantitative (91-117%) for both digestion procedures. Further analysis of Pond Sediment suspensions showed that complete recovery of phosphorus (98 ± 1%) from 60 g/l suspensions was achieved with incomplete recoveries (92.3 ± 0.7%, 91 ± 2% and 91 ± 1%) from 70 g P/l, 80 g P/l and 90 g P/l suspensions respectively. Comparison with the APHA-AWWA WPCF, nitric-sulphuric acid digestion method showed no difference in phosphorus measurements for the microwave procedure but that the autoclave procedure gave significantly lower recoveries of phosphorus (p < 0.01), however, differences were only 2-8%.
Phosphorus NIES 2 NIES 3 Pond Lake River Sample preparation Sample preparation

"Flow Injection Chemiluminescence Determination Of Ultra Low Concentrations Of Nitrite In Water"
Anal. Chim. Acta 1995 Volume 316, Issue 2 Pages 261-268
Pavel Mikuska*, Zbynk Veea and Zbynk Zdrhal

Abstract: A new flow chemiluminescence method for the determination of ultra low concentrations of nitrite in water is presented. Nitrite reacts with H-2O-2 in acid medium to form peroxynitrous acid that is subsequently detected as peroxynitrite by the chemiluminescence reaction with alkaline solution of luminol. The detection limit of nitrite is 1 times 10^-9 mol L-1 (for 50 µl samples) and the calibration graph is linear up to 1 times 10^-5 M NO-2-. The relative standard deviations for 1 times 10^-6 M and 3 times 10^-8 M NO-2- are 1.8% and 5.4%, respectively. The interferences of cations are eliminated by passing the sample through a cation-exchange column. Common anions do not interfere. Analysis time is 3 minutes. The results are in good agreement with a standard spectrophotometric method. (39 References)
Nitrite Water Chemiluminescence

"Development Of A Chemiluminescence Detector With Photodiode Detection For Flow Injection Analysis And Its Application To L-lactate Analysis"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 323-327
Akihide Hemmia, Kaoru Yagiudaa, Naomi Funazakia, Satoshi Itoa, Yasukazu Asano*, Toshihiko Imatob, Kenji Hayashic and Isao Karubed

Abstract: A low cost chemiluminescence detector with a photodiode for flow injection analysis of L-lactate in food was developed for quality control in food industry. In this system, L-lactate is oxidized by the enzymatic reaction with L-lactate oxidase immobilized on the column to produce hydrogen peroxide. Then chemiluminescence caused by mixing hydrogen peroxide with the chemiluminescence reagent was detected by the photodiode. This light intensity was proportional to L-lactate concentration. For detecting weak chemiluminescence efficiently a flow-through cell of the detector was specially designed. A photodiode was used for the purpose of reducing the costs of FIA systems instead of a photomultiplier tube. As a result, a linear working curve was obtained from 10^-7 to 10^-3 mol L-1 L-lactate concentration. We applied the present system with a photodiode detector for food samples and compared the results with those obtained by the conventional HPLC method. The data obtained by the present FIA method were fairly in good agreement with those obtained by the conventional HPLC method. The correlation factor and regression line between both methods were 0.992 and Y= 1.07X-0.15, respectively. The present FIA system with the photodiode detector is available as a simple, easy-handling instrument for quality control in food industry. (8 References)
l-Lactate Food Chemiluminescence

"Online And Off-line Monitoring Of The Production Of Alkaline Serine-protease By Bacillus-licheniformis"
Anal. Chim. Acta 1995 Volume 317, Issue 1-3 Pages 247-258
A. B. Van Puttena, F. Spitzenbergerb, G. Kretzmerb, B. Hitzmannb and K. Sch&uuml;gerlb,*

Abstract: Subtilisin Carlsberg alkaline serine protease was produced by Bacillus licheniformis on complex medium in a stirred tank reactor and the turbidity and culture fluorescence were monitored in situ, absorbance online and off-line, (dry) sediment, (dry) cell mass and DNA concentrations off-line. These data were correlated with each other. The cultivation medium composition: starch, maltose, glucose, urea, ammonia, phosphate concentrations and protease activity were monitored by a six-channel flow injection analysis system online and off-line. Protein concentration, α-amylase activity and intracellularly phosphate concentration were evaluated off-line. The online and off-line data agreed well. Differences in the online and off-line monitored protease activities are caused by the membrane fouling of the sampling system. (18 references)
Ammonia Glucose Maltose Phosphate Starch Urea Fermentation broth Turbidimetry

"An Automated Flow-reversal Injection - Liquid-liquid Extraction Approach To The Direct Determination Of Total Free Fatty Acids In Olive Oils"
Anal. Chim. Acta 1996 Volume 318, Issue 2 Pages 187-194
Zheng-liang Zhi, Angel R&iacute;os and Miguel Valc&aacute;rcel*

Abstract: The apparatus consisted of an online sample dilution subassembly which allowed dilution of olive oil with toluene (1:5) and a single-channel flow-reversal manifold equipped with a circulation loop (34 cm x 0.8 mm i.d.) and a flow-through detection cell (18 µL; 10 mm light path) for the liquid-liquid extraction; spectrophotometric detection was at 716 nm. A portion of diluted olive oil was mixed with 0.02 M copper(II) nitrate and adjusted to pH 6.3 with 50% aqueous pyridine then transferred to the loop and circulated at 1.2 ml/min in the flow-reversal mode with a 9 s cycle so that the aqueous phase did not enter the detection cell. The cycle was repeated up to 10 times to generate multipeak absorbance time signals. The calibration graph was linear from 0.01-1.5% oleic acid which corresponded to 0.06-9% FFA in olive oil. The RSD (n = 11) for the determination of 0.119-0.973% FFA was 7.8-4.9%. The frequency was 2 samples/h. The results obtained were confirmed by a manual procedure and by an acid-base titration method.
Fatty acids, free Oil Spectrophotometry Sample preparation

"Oxidative Detection Of Nitrite At An Electrocatalytic Dichloride-modified Electrochemical Sensor Applied For The Flow Injection Determination Of Nitrate Using A Copper-cadmium Reductor Column"
Anal. Chim. Acta 1996 Volume 319, Issue 1-2 Pages 111-120
Andrew P. Doherty*, Margaret A. Stanley, Donal Leech and Johannes G. Vos

Abstract: A vitreous C electrode (3 mm diameter) modified with the redox polymer [Ru(bipy)2(PVP)10Cl]Cl ~bipy = 2,2'-bipyridyl and PVP = poly-(4-vinylpyridine)~ was utilized in a FIA system for the determination of nitrate (I) following reduction to nitrite at a copperized cadmium reductor column. The single channel flow injection manifold consisted of a 50 µL sample injection loop, the reductor column (12 cm x 0.2 cm i.d.) packed with copperized cadmium chips and a thin-layer detection cell equipped with the working electrode at 0.95 V vs. SCE, a Ag/AgCl reference electrode and with the stainless steel body of the cell acting as the counter electrode. The composition of the carrier stream (0.5 mL/min) was not given. The calibration graph was linear from 10 µM-10 mM I and the detection limit was 5 µM. The RSD was 2% for 0.5 mM I. The method was applied to the determination of nitrate in commercial fertilisers and the results were confirmed by potentiometry.
Nitrate Commercial product Amperometry Electrode Electrode Potentiometry Sensor

"Determination Of Formaldehyde In Frozen Fish With Formaldehyde Dehydrogenase Using A Flow Injection System With An Incorporated Gel-filtration Chromatography Column"
Anal. Chim. Acta 1996 Volume 320, Issue 2-3 Pages 155-164
Iben Ellegaard Bechmann

Abstract: Frozen fish was thawed and 10 g portions were homogenized in 10 mL 10 mM Tris buffer of pH 7.8. Homogenates were centrifuged and the supernatant was filtered. Portions of the filtrate were injected in to a Tris buffer carrier of pH 7.8 (0.75 ml/min) and passed through a Sephadex G-25 (20-80 µm) gel filtration column to remove proteins, before injection into a stream of 50 mM phosphate buffer of pH 7.8 (0.75 ml/min). This merged with a similar stream (0.35 ml/min) into which formaldehyde dehydrogenase/NAD had been injected. After reaction at 40°C in a coil (75 cm x 0.5 mm i.d.) photodiode array detection at 340 nm was performed. The method was faster than standard methods and less affected by interferences. The limit of detection was 2.5 mg/l formaldehyde. A calibration graph for up to 50 mg/l is shown. Sample throughput was 10 per hour. The results were compared with those obtained by the Nash test.
Formaldehyde Marine Spectrophotometry

"Online Monitoring Of Glucose And Penicillin By Sequential Injection Analysis"
Anal. Chim. Acta 1996 Volume 320, Issue 2-3 Pages 199-205
Rong Wei Min, Jens Nielsen* and John Villadsen

Abstract: In the sequential injection flow analysis (SFIA) system, sample was injected via a six-position valve into a bioreactor. The enzyme reactors were prepared by immobilizing glucose oxidase and penicillinase on a piece of nylon tubing. Glucose was converted to gluconolactone and the H2O2 formed was detected by a chemiluminescence reaction involving luminol. The penicillin was converted to penicilloic acid, which was detected by its quenching effect on the chemiluminescence signal obtained when luminol and iodine reacted. It was also detected spectrophotometrically by the decrease in absorbance of an iodine-starch complex. Online and offline measurements showed good agreement. The SFIA system was simpler than conventional FIA and running costs were lower. The system was used to analyze Penicillium cultivations.
Glucose Penicillin Fermentation broth Chemiluminescence Spectrophotometry

"Flow Injection Analysis With Chemiluminescent Detection Of Sulfite Using Sodium Carbonate-sodium Bicarbonate-copper Ion System"
Anal. Chim. Acta 1996 Volume 323, Issue 1-3 Pages 69-74
Jin-Ming Lin* and Toshiyuki Hobo

Abstract: An FIA system incorporating a gas diffusion cell is described for the selective determination of sulfite. A 100 µL sample was injected into a 0.1 M H2SO4 stream (0.5 ml/min) and transported to the cell, where the liberated SO2 diffused through a PTFE membrane (0.02 µm pore size, 45 µm thickness) and was collected in a 0.6 M Na2CO3 stream (0.5 ml/min). The collector stream was propelled to the chemiluminescence detector and mixed with a reagent stream formed by merging 0.4 M NaHCO3 and 0.5 mM Cu(II) (both at 1.5 ml/min). The light emitted was detected by a photomultiplier tube. The calibration graph obtained by plotting light intensity vs. log. sulfite concentration was linear for 1 µM-0.5 mM, the detection limit was 0.5 µM, and the RSD (n = 9) for 5 µM-sulfite was 4.6%. The method was applied to the determination of sulfite in wine following 100-500-fold dilution. The results were verified by a titration method with iodine.
Sulfite Wine Chemiluminescence

"Online Coupling Of A Liquid-liquid Extraction Flow-reversal System To A Spectrophotometric Flow-through Sensor For The Determination Of Polyphenols In Olive Oil"
Anal. Chim. Acta 1996 Volume 323, Issue 1-3 Pages 55-62
M. P. Ca&ntilde;izares, M. T. Tena and M. D. Luque De Castro*

Abstract: The sensor for the spectrophotometric determination of polyphenols at 750 nm consisted of a flow-through cell (18 µL volume, 1.5 mm optical pathlength) packed with DEAE-Sephadex anion exchanger (40-120 µm) impregnated with Folin-Ciocalteu reagent. The sensor was incorporated into a flow injection manifold for the liquid-liquid extraction of polyphenols from diluted olive oil. A 500 µL sample of diluted olive oil (1:5 with hexane) was injected into 0.1 M NaHCO3 and propelled (1.3 ml/min) through an extraction coil (100 cm x 0.7 mm i.d.) several times by flow reversal. Only the analyte-enriched aqueous phase reached the sensor, where the analyte was retained and detected. The calibration graph, prepared with use of caffeic acid and 10^-20 flow-reversal cycles, showed linear segments for 15-30 µg/ml and 35-90 µg/ml, and the detection limit was 10 µg/ml. The sensitivity of the method improved with the number of cycles (N), while the RSD decreased. The sampling frequency was 11 per h for N = 10 and 8 per h for N = 20. The method was applied to the analysis of eight different olive oils, and the results are compared with those obtained by a conventional method based on the same chemical reaction.
Polyphenols Oil Ion exchange Spectrophotometry Sample preparation Sensor

"Automated Determination Of Lactulose In Milk Using An Enzyme Reactor And Flow Analysis With Integrated Dialysis"
Anal. Chim. Acta 1996 Volume 324, Issue 1 Pages 37-45
Michael Mayer, Meike Genrich, Wolfgang K&uuml;nnecke and Ursula Bilitewski*

Abstract: The automated FIA method was based on the enzymatic hydrolysis of lactulose to fructose and galactose followed by the separation of fructose by dialysis and its detection by fructose dehydrogenase (FDH) catalyzed oxidation with ferricyanide as electron acceptor. The manifold allowed a sample stream (0.1 ml/min) to be merged with the reaction buffer stream (0.1 ml/min) containing 185 iu/ml β-galactosidase in phosphate buffer of pH 5. The flow was propelled through a reaction coil (1.3 m x 0.8 mm i.d.) operated at 50°C and the donor channel of the dialysis cell. The acceptor channel (64 mm x 2 mm x 0.5 mm) of the dialysis cell contained stationary 2 mM potassium ferricyanide in phosphate/citrate buffer of pH 5.5. After a dialysis period of 180 s, the acceptor solution was pumped through the FDH enzyme reactor to an amperometric detector where the ferrocyanate was re-oxidized. The amperometric detector was equipped with a screen-printed Pt electrode at +385 mV vs. Pt reference. The method was applied to the analysis of milk samples using a standard-addition calibration procedure. Lactulose concentrations of up to 12.28 mM were measured and these results were confirmed by a photometric method. The sampling frequency for the proposed method was 17 samples/h.
Lactulose Milk Amperometry Electrode

"A Liquid Drop: A Windowless Optical Cell And A Reactor Without Walls For Flow Injection Analysis"
Anal. Chim. Acta 1996 Volume 326, Issue 1-3 Pages 13-22
Hanghui Liu and Purnendu K. Dasgupta*

Abstract: A dynamically growing and falling liquid drop was proposed as a windowless optical detection cell for FIA. The drop of ~e;52 µL was formed on the end of a PTFE tube (3.7 mm o.d, 1.5 mm i.d.). Detection was performed using a blue light-emitting diode (450 nm) and the transmitted light was conducted by a 1.5 mm o.d. plastic optical fiber to a photodiode equipped with an interference filter centred at 460 nm. The system was evaluated by determining sulfate using the Ba2+ precipitation reaction by injection of ~e;70 µL of test solution into a reagent stream (0.8 ml/min) of 5% BaCl2 in 0.01 M HCl. The FIA peak was observed over several drops. Quantitative measurements were made at a single drop and calibration ranges were linear for 20-2000 mg/l at drops 3 and 5 and 20-1000 mg/l at drop 4. The detection limit was 26 mg/l and the RSD (n = 8) for 100 mg/l of sulfate was 4%. The method was used to determine sulfate in tap water and the results were confirmed by ion chromatography. The liquid drop could also serve as a reactor cell by mixing the reagent and analyte in the drop.
Sulfate Water Turbidimetry

"Flow Injection Analysis With Amperometric Detection Of Cocaine In Confiscated Samples"
Anal. Chim. Acta 1996 Volume 328, Issue 1 Pages 67-71
M. Teresa Fern&aacute;ndez-Abedul and A. Costa-Garc&iacute;a*

Abstract: Sample (10 mg) was extracted with 25 mL water, and 125 µL of the extract was diluted to 25 mL Bon-Robinson buffer of pH 9 (buffer A). A portion (200 µL) of the resulting solution was injected into the FIA system and transported to the amperometric detector cell by a carrier stream (2.5 ml/min) of buffer A. Cocaine was detected at a C paste electrode at +1 V vs. Ag/AgCl/sat. KCl (stainless-steel auxiliary electrode). The calibration graph was linear for 0.2 (detection limit) to 10 µM cocaine and the RSD (n = 12) for 6.2 µM-cocaine was 1.7%. The sampling frequency was 60/h. The method was applied to three confiscated samples of illegal drugs and the results were confirmed by LC.
Drugs Cocaine Amperometry Electrode

"Selective Determination Of Sulfuric Acid In Liquors From Acidic Nickel Ore Extraction By Flow Injection Analysis"
Anal. Chim. Acta 1996 Volume 328, Issue 1 Pages 61-65
Isel Cort&eacute;s and Fernando Albert&uacute;s*

Abstract: Sample (110 µL) was injected into a water carrier stream (2.6 ml/min) which then merged with a reagent stream (0.6 ml/min) containing 0.5 M Na2SO4 and 0.2 mM methyl orange. The flow passed through a mixing coil (60 cm x 0.5 mm i.d.) to the detector where the absorbance was measured at 520 nm. A non-linear calibration graph was obtained for up to 12.5 mM H2SO4. The RSD (n=10) was 2%. The sampling frequency was 120/h. The method was applied to three industrial process solutions; RSD (n = 3) were ≤8%. The results were confirmed by potentiometric titrimetry.
Sulfuric acid Nickel Process liquor Spectrophotometry Potentiometry

"Amperometric Flow Injection Determination Of Fructose In Honey With A Carbon Paste Sensor Based On Fructose Dehydrogenase"
Anal. Chim. Acta 1996 Volume 330, Issue 1 Pages 71-77
Josefina Parelladaa, Elena Dom&iacute;ngueza,*, and Victor M. Fern&aacute;ndezb

Abstract: A carbon paste electrode modified 1% polyethyleneimine and pyrrolo quinoline quinone-fructose dehydrogenase (300 iu enzyme/100 mg grap) was employed at 400 mV vs. Ag/AgCl (0.1 M KCl) with a Pt wire counter electrode in a FIA system for determining fructose. The carrier stream (1 ml/min) was 0.1 M acetate buffer at pH 5 and the injection volume was 20 µL. A linear calibration graph was produced for 0.5-10 mM fructose, the detection limit was 75 µM and the RSD (n = 15) for 10 mM fructose was 1.6%. The system was used to determine fructose in honey. Honey samples of 10 g were extracted with 100 mL 0.1 M acetate buffer at pH 5 for 15 min at 60°C. The filtrate was diluted 25-fold with the same buffer and 20 µL portions were analyzed. The results were confirmed by LC with refractive index detection.
Fructose Food Amperometry Electrode Electrode Sample preparation Sensor

"Determination Of Highly Concentrated Sodium, Potassium, Magnesium And Calcium In Dialysis Solution With Flow Injection Online Dilution And Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1996 Volume 331, Issue 3 Pages 263-270
T. Guo*, J. Baasner and S. McIntosh

Abstract: A cascade dilution manifold was used for the online dilution of samples for flame AAS. A 40-50 µL sample was injected into a carrier stream which was passed through a series of stream-splitting and stream-merging junctions. The spitting/merging operations were carried out using all eight channels of a peristaltic pump. The dilution factor was controlled by the flow rate of the carrier stream and by changing the manifold configuration. Dilution factors of 10^-3000 were achieved while maintaining a high rate of sample throughput. The manifold was used to dilute dialysis solution 1000-fold prior to analysis for Na (330.2 nm), K (766.5 nm), Mg (285.2 nm) and Ca (442.7 nm) by AAS with an air-acetylene flame. The RSD (n = 11) was 2% and the sampling frequency was 70/h. Results agreed with those obtained using a manual method.
Calcium Magnesium Potassium Sodium Dialysis Fluid Spectrophotometry

"Flow Injection Extraction-spectrophotometric Determination Of Copper Using Bis(acetylacetone)ethylenediimine"
Anal. Chim. Acta 1996 Volume 331, Issue 3 Pages 253-256
N. Chimpalee, D. Chimpalee, S. Lohwithee, L. Nakwatchara and D. Thorburn Burns*

Abstract: Sample (250 µL) was injected into a water carrier stream (1.4 ml/min) which was then merged sequentially with acetate buffer of pH 5 (1.4 ml/min), 0.2% bis(acetylacetone)ethylenediimine in aqueous 10% ethanol (1.4 ml/min) and CHCl3 (1 ml/min). The mixture was passed through an extraction coil (400 cm x 0.8 mm i.d.) to a phase separator. The organic phase was fed to the spectrophotometric detector where the absorbance was measured at 370 nm. The calibration graph for Cu was linear for up to 100 µg/ml, the detection liwas 0.42 µg/ml and the RSD (n = 10) for 20 µg/ml Cu was 1.95%. The method was applied to Cu-based alloys and pig feeds. The results for the alloys were in agreement with the certified values and those for pig feed were confirmed by AAS. The sampling rate was 20/h.
Copper Alloy Pig Feed Spectrophotometry Sample preparation

"Vapor Generation Fourier Transform Infrared Spectrometric Determination Of Benzene, Toluene And Methyl Tert.-butyl Ether In Gasolines"
Anal. Chim. Acta 1996 Volume 333, Issue 1-2 Pages 157-165
Emilio L&oacute;pez-Anreus, Salvador Garrigues and Miguel de la Guardia*

Abstract: A simple and fast procedure has been developed for the direct and simultaneous determination by Fourier transform infrared (FTIR) spectrometry of benzene, toluene and methyl tert.-butyl ether (MTBE) in gasoline samples. The method is based on the injection of 1 µl of gasoline into an electrically heated Pyrex glass reactor in which the sample is volatilized at 90°C. The vapor generated is transported by means of a nitrogen carrier flow of 400 mL min-1 inside an IR multiple pass gas cell and the spectrum in the mid-IR region is registered between 1600 and 500 cm-1 as a function of time. The flow injection recordings obtained for the LR bands between 671-675 cm-1, 727-731 cm-1, and 1210-1214 cm-1 were employed for the determination of benzene, toluene and MTBE respectively, using different criteria for establishing the baseline correction. Results obtained in the analysis of commercial samples of gasoline agree with those found by gas chromatography and another FTIR reference procedure.
Benzene Toluene Methyl-t-butylether Oil Spectrophotometry

"Enhancing The Performance Of Membrane Introduction Mass Spectrometry By Organic Carrier And Liquid Chromatographic Separation"
Anal. Chim. Acta 1997 Volume 337, Issue 2 Pages 165-172
Shi Ouyang, Yong Hong Chen* and Yan Xu*

Abstract: A method of membrane introduction mass spectrometry with liquid chromatographic separation (LC/MIMS) for the analysis of volatile organic compounds (VOCs) in water has been developed. The method not only inherited all the advantages of membrane introduction mass spectrometry by flow injection analysis (FIA/MIMS), but also expanded the application of MIMS to the determination of compounds with identical quantitation ions. Because the quantitation by LC/MIMS is based on two-dimensional identification (retention time (t-r) and mass-to-charge ratio (m/z)), it provides a tangible approach to the analysis of VOCs in complex aqueous samples. In this work, a C-18 column and a mobile phase (methanol/water) were used for chromatographic separation. A mixture of eighteen VOCs was determined within 28 min. The method has linear dynamic ranges of 3-4 orders of magnitude and sub-ppb-level detection limits. In comparison with the EPA method 524.2 (a purge-and-trap GC/MS method), it requires less analysis time and no sample pretreatment.
Organics, volatile Environmental Mass spectrometry

"Chemiluminescent Flow Injection Determination Of Alkaline Phosphatase And Its Applications To Enzyme Immunoassays"
Anal. Chim. Acta 1997 Volume 339, Issue 1-2 Pages 139-146
Jin-Ming Lin, Akio Tsuji and Masako Maeda*

Abstract: The flow injection chemiluminescence method for determining alkaline phosphatase (ALP) was based on the catalyzed reaction of cortisol-21-phosphate to produce cortisol which was detected by its chemiluminescence reaction with lucigenin (NN'-dimethyl-9,9'-biacridinium dinitrate). Sample (100 µL) was injected into a Tris hydrochloride buffer carrier stream (0.5 ml/min) at pH 10 which was merged with the reagent stream (1.5 ml/min) containing 0.1 mg/mL lucigenin and 0.06% cetyltrimethylammonium bromide in 0.1 M NaOH. The chemiluminescence was detected using a photomultiplier tube. The calibration graph for 4-50 pM-ALP was presented. The detection limit was 1 pM-ALP and the RSD (n = 5) was <6.1%. The method was applied to FIA for 17-α-hydroxyprogesterone and human chorionic gonadotropin in urine or serum using ALP as the enzyme label. The results correlated with those obtained by other methods.
Enzyme, alkaline phosphatase 17-Hydroxyprogesterone Gonadotropin chorionic Serum Human Urine Chemiluminescence Immunoassay

"Flow Injection Analysis Of Copper Diethyldithiocarbamate In High Resistance Toluene Media Using A Microelectrode Detector"
Anal. Chim. Acta 1997 Volume 340, Issue 1-3 Pages 169-174
T. J. Cardwell*, J. H. Santos and A. M. Bond

Abstract: Copper diethyldithiocarbamate was detected in toluene based carrier streams, at a flow rate of 1.1 ml/min, containing either 0.03 M tetrahexylammonium perchlorate or 35% acetonitrile at a Pt microelectrode detector (5-25 µm radius) maintained at 1 V vs. Au. Calibration graphs were linear from 0.5 mM; detection limits were 0.1 µM (5 µm electrode) to 50 nM (25 µm electrode) with an injection volume of 50 µL. The method was used to determine Cu in standard and potable water samples following extraction as copper diethyldithiocarbamate into toluene. The results were verified by solvent extraction cathodic stripping voltammetry.
Copper Water Amperometry Electrode Electrode Sample preparation

"Flow Injection Determination Of Aluminum(III) Ions And Al13O4(OH)24 (H2O)127+ Species Using A 1.3 S Reaction With 8-quinolinol-derivatized Fractogel"
Anal. Chim. Acta 1997 Volume 343, Issue 1-2 Pages 19-32
Stuart L. Simpson, Kipton J. Powell*, and Nils H. S. Nilsson

Abstract: A flow injection spectrophotometric method is described to determine (i) 'free Al', viz. Al3+ plus Al(OH)2+ and very labile Al complexes, (ii) Al in moderate labile complexes and (iii) Al-hydroxo polymers, viz. Al13(OH)327+. A sample volume of 650 µL was inserted into a carrier stream (1 ml/min) of 0.05 M sodium acetate/0.05 M NaCl of pH 5 and propelled through a column reactor (22 µL) containing 8-quinolinol immobilized onto Fractogel. Free Al and Al-hydroxo polymers were retained by the column while moderate labile Al complexes passed through. The column effluent was merged with a reagent stream formed online by merging 2 M acetate buffer of pH 5.3 (0.21 ml/min) and 2 mM chrome azurol S (0.04 ml/min). The flow then passed through a reactor coil (300 cm x 0.5 mm i.d.) to the detection cell (70 µL) where the absorbance was measured at 545 nm. Free Al was eluted from the column reactor with 250 µL 0.02 M NaOH and the Al-hydroxo polymers were eluted with 60 µL 0.2 M NaOH using a 2 min stopped-flow procedure. The linear range of the method was 0.3-16 µM-Al3+, the detection limit was 70 nM and the RSD for 0.5 µM was 7%. The method was applied to aqueous soil extracts and humic waters and the results for free Al were compared to those obtained by the 7 s chrome azurol S method.
Aluminum(III) Aluminum, free Environmental Environmental Spectrophotometry Sample preparation

"Flow Injection Determination Of Anionic Surfactants Based On The Solvatochromism Of P-diphenylaminoazobenzene Sulfonate"
Anal. Chim. Acta 1997 Volume 343, Issue 1-2 Pages 33-37
Jingfu Liu*

Abstract: The flow injection spectrophotometric method for determining anionic surfactants was based on the increase in absorbance of the p-diphenylaminoazobenzene sulfonate (PDABS)/Triton X-100 (T- x 100)/hexadecyltrimethylammonium bromide (CTAB) system at 530 nm in the presence of an anionic surfactant. Sample (200 µL) was injected into a water carrier stream (1.8 ml/min) which was then merged with a reagent stream formed online by merging CTAB/200 µg/ml T- x 100 (0.9 ml/min) and PDABS (0.9 ml/min). The mixture was passed through a reaction coil (100 cm x 0.5 mm i.d.) to the detector cell where the absorbance was monitored. The concentration of PDABS was 0.12-0.2 mM and was 20% greater than the concentration of CTAB. The determination was carried out at pH 1. Linear calibration graphs were obtained for five different anionic surfactants for up to 40 µM. The RSD (n = 11) for 20 µM-sodium dodecylbenzenesulfonate (DBS) was 0.9%. The detection limits for DBS and SDS were 0.2 µM. The method was applied to washing powders and the results were confirmed by the Epton titrimetric method.
Surfactants, anionic Commercial product Spectrophotometry

"Selective Determination Of Protolytes By Flow Injection Analysis. A Guide For The Rational Selection Of Reagent Composition"
Anal. Chim. Acta 1997 Volume 344, Issue 3 Pages 271-280
Fernando Albert&uacute;s*, Isel Cort&eacute;s, Lars G. Danielsson and Folke Ingman

Abstract: The measurement of the concentration of a strong acid or base in the presence of a weaker one is described. A systematic methodology for selecting a reagent mixture for the spectrophotometric determination of protolytes by FIA is proposed. A theoretical study was performed of the instantaneous equilibria obtained at the peak maximum when two protolytes injected into the carrier merge and react with a buffer/indicator stream. The strength and concentration of the buffer required to neutralize the stronger component without reacting with the weaker one were deduced. Guidelines are given for the selection of an indicator for combination with a preselected buffer. Synthetic and real samples of acid and alkaline mixtures were analyzed and the results were compared with those obtained by potentiometric titration.
Acids Bases Spectrophotometry Potentiometry

"A New Amperometric Biosensor For Salicylate Based On Salicylate Hydroxylase Immobilized On Polypyrrole Film Doped With Hexacyanoferrate"
Anal. Chim. Acta 1997 Volume 347, Issue 1-2 Pages 35-41
Benjamin G. Milagresa, Graciliano de Oliveira Netoa, Lauro T. Kubotaa,* and Hideko Yamanakab

Abstract: An amperometric biosensor for salicylate detection was developed by immobilizing salicylate hydroxylase via glutaraldehyde onto a polypyrrole film doped with hexacyanoferrate, supported on a glassy carbon electrode surface. The sensor monitors the catechol produced in the enzymatic reaction on the film surface, at an applied potential of 150 mV vs. SCE. A / ratio between 2 and 4 gave the best response. The biosensor presented the best performance in a solution with pH=7.4. The response time was about 40 s. A linear range of response was observed for salicylate concentrations between 1.0 x 10^-5 and 1.0 x 10^-4 mol L-1 and the equation adjusted for this curve was I=(-0.04±0.01)+(11.4±0.2) with a correlation coefficient of 0.999 for n=6. The biosensor retains its activity for at least 10 days despite daily use. The results obtained using the biosensor for salicylate determination, in three different samples of antithermic drugs, presented a good correlation with the standard colorimetric method. 34 References
Salicylate Pharmaceutical Amperometry Electrode Electrode Electrode Sensor

"Development Of A Highly Sensitive Enzyme-linked Immunosorbent Assay For Atrazine. Performance Evaluation By Flow Injection Immunoassay"
Anal. Chim. Acta 1997 Volume 347, Issue 1-2 Pages 149-162
Jordi Gasc&oacute;n, Anna Oubi&ntilde;a, Berta Ballesteros, Dami&agrave; Barcel&oacute;, Francisco Camps, Mar&iacute;a-Pilar Marco*, Miguel Angel Gonz&aacute;lez-Mart&iacute;nez, Sergi Morais, Rosa Puchades and Angel Maquieira

Abstract: Three polyclonal antisera obtained from immunized rabbits and nine hapten-horseradish peroxidase enzyme tracers were screened to develop a ELISA for atrazine in water. The optimized competitive ELISA was carried out on a antisera-coated microtitre plate by incubating the atrazine sample for 30 min, then adding the enzyme tracer and incubating for a further 6 min. After washing, the tetramethylbenzidine/H2O2 substrate solution was added. The reaction was stopped after 30 min with H2SO4 and the absorbance was measured at 450 nm. The detection limit for atrazine was 0.043 nM. Cross-reactivity studies showed that the assay was specific and that other triazines were only detected to a minor extent. A flow injection immunoanalysis (FIIA) method for atrazine was performed by passing a atrazine sample/enzyme tracer mixture through an immunoreactor containing immobilized antibodies. The 3-(p-hydroxyphenyl)-propanoic acid/H2O2 substrate solution was then injected onto the column and incubated for 60-240 s. The product of the enzyme reaction was detected by fluorimetry at 405 nm (excitation at 320 nm). The working range of the FIIA method was 0.075-2.5 µg/l and the detection limit was 75 ng/l (0.35 nM). The ELISA and FIIA methods were evaluated by analyzing water samples containing mixtures of atrazine and other pesticides at the ppb level.
Atrazine Water Immunoassay Fluorescence

"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

"Use Of PH Gradients In Continuous-flow Systems And Multivariate Regression Techniques Applied To The Determination Of Methionine And Cysteine In Pharmaceuticals"
Anal. Chim. Acta 1997 Volume 348, Issue 1-3 Pages 151-159
F. Blasco, M. J. Medina-Hern&aacute;ndez and S. Sagrado*

Abstract: The simultaneous spectrophotometric determination of methionine and cysteine in presence of cystine and other compounds in pharmaceuticals, using a multivariate calibration method, was studied. The method is based on the reaction between the analytes and the o-phthalaldehyde-N-acetyl-L-cysteine (OPA-NAC) reagent performed in a continuous-flow system (FI). The FI system allows the generation of a local pH gradient in order to produce spectral and/or kinetic changes in the W-Vis spectra of the amino acid-OPA-NAC derivatives. This information is used to improve the prediction ability of the Partial Least-Squares (PLS) models. The performance of two FI assemblies, the selection of variables and the pretreatment of the data were studied. A series of eighteen synthetic solutions containing different concentrations of methionine, cysteine and cystine was prepared and used as a calibration set to study the PLS models. In addition, solutions of a commercial formulation containing the three amino acids were prepared and the content of methionine and cysteine was predicted. The results obtained using the PLS models were compared with those obtained using an HPLC method. 13 References
Methionine Cysteine Pharmaceutical Spectrophotometry

"Evaluation Of Spectrophotometric Methods For Determination Of Orthophosphates By Sequential Injection Analysis"
Anal. Chim. Acta 1997 Volume 350, Issue 1-2 Pages 21-29
A. Mu&ntilde;oz, F. Mas Torres, J. M. Estela and V. Cerda*

Abstract: Three methods for the determination of orthophosphate have been studied by using the same sequential injection analysis manifold, namely the vanadomolybdate, the malachite green and the molybdenum blue methods. The calibration graphs were linear up to 18.0, 0.4 and 4.0 mg P l-1, respectively. Relative standard deviations and detection limits were 2.1%, 18% and 1.7% and 0.15, 0.01 and 0.01 mg P L-1 respectively. The three methods were applied to the determination of phosphate in several water samples, both from natural and waste origin at a frequency of about 30 determinations per hour.
Phosphate Environmental Waste Spectrophotometry

"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

"Automated Flow Injection Spectrophotometric Non-aqueous Titrimetric Determination Of The Free Fatty-acid Content Of Olive Oil"
Anal. Chim. Acta 1997 Volume 351, Issue 1-3 Pages 291-297
Panayotis G. Nouros, Constantinos A. Georgiou and Moschos G. Polissiou*

Abstract: An automated how injection titrimetric method for the determination of olive oil acidity is proposed. A 175 µl olive oil aliquot is injected in a carrier stream (the titrant) of n-propanol containing 7.5 x 10^-4 M KOH and 4.0 x 10^-5 M phenolphthalein indicator. The sample zone is dispersed in the titrant while flowing at 4.4 mi min-1 through a 1.1 mi Plexiglas mixing chamber and the absorbance of the resulting mixture is continuously monitored at 562 nm, lambda(max), for the basic form of the indicator. The resulting negative absorbance peaks indicate the transition base (red)-acid (colorless)-base (red) of the indicator. Quantitation is based on peak width measurements. Peak widths of 31.7-97 a were measured with a relative standard deviation (RSD) of < 2.1% (n = 10), and the analytical range was 0.15-8.0% (w/w) free fatty acid content calculated as oleic acid. The sampling rate is 30-100 h-1 while n-propanol consumption is only 3-7 mi per run. Recoveries of oleic acid from commercial olive oils ranged from 97.9 to 101.6% (mean 99.5%). The method was applied for the determination of free fatty acid content of thirty two samples of olive oils. Results obtained by the proposed method compare well (0.3-3.6% relative difference, mean 1.5%) with those obtained by the official European Community method that is time consuming and uses gross amounts of organic solvents. Moreover comparison with a Fourier transform infrared F-IR) method reveals that by using the proposed method the useful range can be extended to lower concentrations. 18 References
Fatty acids, free Oil Spectrophotometry

"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

"Direct Chemiluminescence Determination Of Ascorbic-acid Using Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 356, Issue 2-3 Pages 289-294
Irena B. Agater and Roger A. Jewsbury*

Abstract: A flow injection method is described for the determination of (5 x 10^-7 to 1 x 10^-3 M) ascorbic acid by measurement of the chemiluminescence from direct oxidation with permanganate in an acidic medium. The method is applied to fruit drinks and nutritional supplements and compared satisfactorily with titrimetric and spectrofluorimetric methods. 14 References
Ascorbic acid Fruit Commercial product Chemiluminescence

"Turbidimetric Flow Injection Determination Of Total Nitrogen And Potassium In Vegetables"
Anal. Chim. Acta 1997 Volume 356, Issue 2-3 Pages 259-265
Jos&eacute; L. F. C. Limaa, Ant&oacute;nio O. S. S. Rangelb,*, M. Renata S. Soutob and Elias A. G. Zagattoc

Abstract: A turbidimetric flow injection system was developed for the determination of total nitrogen and potassium in vegetable samples using a single spectrophotometer as detector. As a precipitating agent, 3.0% (w/v) sodium tetraphenylboron solution prepared in 2.0% (w/v) poly(vinyl alcohol) was used. A gas diffusion process was included in the manifold to separate ammonium ions from the rest of the sample and to allow paired analysis. Total nitrogen and potassium determinations were carried out on the solutions remaining in the acceptor and donor streams, respectively. Results obtained were precise (relative standard deviations <2.1 and 1.6% for total N (<25 mg g-1) and K (<55 mg g-1) determinations, respectively) and in agreement with those of reference methods. Analysis can be carried out at a rate of up to 35 samples per hour (corresponding to 70 determinations per hour) within concentration range 87-430 mg N-NH4+ L-1 and 78-390 mg K+ L-1 for the total nitrogen and potassium determinations, respectively. 17 References
Nitrogen, total Potassium Vegetable Turbidimetry

"Highly-dispersed Copper Microparticles On The Active Gold Substrate As An Amperometric Sensor For Glucose"
Anal. Chim. Acta 1997 Volume 357, Issue 1-2 Pages 63-71
Innocenzo G. Casella*, Maria Gatta, Maria R. Guascito and Tommaso R. I. Cataldi

Abstract: A bimetallic electrode composed of copper microparticles dispersed onto a gold surface (Au/Cu) has been investigated as an amperometric sensor using glucose as a model compound. Such a sensing electrode has been prepared by electrochemical deposition of Cu-0 from 50 mM CU2+ and subsequent potential cycling in an alkaline medium. The morphology of the copper deposit has been examined by scanning electron microscopy. The effects of copper loading, scan rate, hydroxide concentration, and applied potential on the electrocatalytic oxidation of glucose have been also investigated. Long-term electrode stability, background current, sensitivity, and linear range of the Au/Cu electrode have been assessed for constant-potential amperometric detection (DC) at +0.550 and +0.350 V, and in pulsed-potential amperometric detection (PAD). When used as an amperometric sensor in the DC mode at an applied potential of +0.350 V, the bimetallic electrode yields a detection limit of 0.8 pmol glucose (S/N=3) with a linear dynamic range of four orders of magnitude. Comparable results have been obtained when the bimetallic sensing electrode was used in the DC mode at +0.550 V and in the PAD mode. Good mechanical stability under forced flow hydrodynamic conditions was also found upon changing the detection mode from DC to PAD and vice versa, making the multifunctional amperometric sensor very attractive for analytical applications in flowing streams.
Glucose Amperometry Electrode Electrode Sensor HPIC

"Sequential Injection System In Flame Atomic Absorption Spectrometry For The Determination Of Calcium And Magnesium In Mineral Waters"
Anal. Chim. Acta 1998 Volume 358, Issue 2 Pages 111-119
Alberto N. Ara&uacute;jo,*, Rui C. C. Costa, Jos&eacute; L. F. C. Lima and Boaventura F. Reis

Abstract: A flow set-up based on sequential injection analysis is proposed to increase the versatility and robustness of routine flame atomic absorption anal. methods. Four procedures were selected to allow the determinations of Ca within 0.03-10.00 and 0.58-200.00 mg/L, and Mg within 0.03-1.5 and 0.80-50.0 mg/L in mineral waters. The sample aliquots inserted were 70.8 and 12 µL for Ca and 13 and 12 µL for Mg. The system enabled to restrict the consumption of the releasing agent to respectively. 142 and 97 µL in the determinations of Ca and to 26 and 12 µL in the determinations of Mg. The results of the analysis of 15 mineral waters were compared with those obtained by the corresponding conventional procedures. In all cases the sampling rates were >110/h, and reproducibility was better than 3.
Calcium Magnesium Mineral Spectrophotometry

"Simultaneous Biosensing Of Inosine Monophosphate And Glutamate By Use Of Immobilized Enzyme Reactors"
Anal. Chim. Acta 1998 Volume 358, Issue 2 Pages 127-136
Kiyoshi Matsumoto*, Waka Asada and Reiko Murai

Abstract: The simultaneous determination of inosine monophosphate (IMP) and l-glutamate (GL), by enzyme-supported flow injection analysis (FIA), was performed using two enzyme reactors in parallel. Inosine monophosphate dehydrogenase (IMPDH) was extracted and partially purified from Bacillus cereus (JCM 2152). The reaction of IMP with NAD+ was catalyzed by IMPDH and the NADH produced was further converted to NAD+ and hydrogen peroxide by NADH oxidase. GL was determined by using the enzyme glutamate oxidase. Thus, IMP and GL were indirectly measured by monitoring hydrogen peroxide electrochemically. The ghost response caused by the presence of interferences in real sample were reduced by covering the platinum electrode surface with a diaminobenzene polymer membrane which was generated by electropolymn. Linear relations between sensor response and each species were observed in the ranges of 0.1-1.0 mM (IMP) and 0.05-1.0 mM (GL) with correlation coefficients >0.997 for each species. The proposed method was used for seasoning analyzes and the results showed good agreement with those obtained using a liquid chromatography method (for IMP) or a conventional method (for GL with a kit), suggesting that this system may be applicable to the quality evaluation of food seasoning.
Inosine monophosphate l-Glutamate Marine Electrode Electrode

"Determination Of Monochloroacetic Acid Using A Flow Injection System Featuring A Flow Through Ion-selective Electrode And An Ion-exchange Column For The Minimization Of Interference By Chloride."
Anal. Chim. Acta 1998 Volume 359, Issue 3 Pages 311-320
C. Puig-Lleix&agrave;, J. Bartrol&iacute;a, M. del Valle*, D. Montll&oacute; and A. Tomico

Abstract: An automated flow injection system for online monitoring of monochloroacetic acid (I) in industrial processes for the prodn. of zwitterionic surfactants (betaines) was developed, which can treat samples with chloride ion concentration. up to 1 M. The system features an ion-exchange column for the separation of I from the interfering compounds in the complex sample. The sample is injected at low pH so that interfering anions, mainly Cl-, are retained in the ion-exchange column. Detection was carried out using specially constructed all-solid-state tubular flow-through ion-selective electrodes sensitive to monochloroacetate. Selectivity data of the constructed electrodes were given; their pH working range was 4.0-11.0, with a lifetime of >30 days at a concentration. of 10^-4 to 10^-1 M. Once applied to the treatment of real samples, the system developed can detect I at concentrations. 5 x 10^-3 - 10^-1 M, with a max. deviation of 5% when compared to standard photometric methods of anal. The short time used in each determination (30 s) in addition to its simplicity, leads to an improvement of available anal. techniques.
Monochloroacetic acid Ion exchange Electrode Electrode

"Sol-gel Immobilized Room-temperature Phosphorescent Metal-chelate As Luminescent Oxygen Sensing Material"
Anal. Chim. Acta 1998 Volume 360, Issue 1-3 Pages 17-26
J. M. Costa-Fern&aacute;ndez, M. E. Diaz-Garc&iacute;a and A. Sanz-Medel*

Abstract: The chelate formed by 8-hydroxy-7-iodo-5-quinolinesulfonic acid (ferron) with aluminum exhibits strong room-temp. phosphorescence (RTP) when retained on a solid support. In a previous paper sol-gel technol. is a very useful approach for developing RTP optical sensors as a new way to immobilize lumiphors. Sol-gel active phases proved to exhibit a high phys. rigidity that enhanced relative RTP intensities and triplet lifetimes of the immobilized probe. The authors present an optical sensing phase prepared using the Al-ferron chelate which displays RTP entrapped in a sol-gel glass matrix for the determination of very low levels of oxygen both dissolved in water and organic solvents and in gaseous media. The sol-gel sensing material proved to be chemical stable for at least 6 mo under ambient storage conditions. Besides a high reproducibility in the formation of the sensing materials and no leaching or bleaching of the trapped reagent (neither in the gas phase nor in water or organic solvents) was observed Oxygen was determined by continuous-flow and flow injection methods using both intensity and triplet lifetime measurements. Both methods provided a fast response, good reproducibility and detection limits of 0.0005% (v/v) in the gas phase and <0.01 mg L-1 for dissolved oxygen. An exhaustive study of the effect of some possible interferents present in the gas phase or in solution demonstrated the high specificity of this phosphorescent probe. This highly sensitive oxygen probe was successfully applied to dissolved oxygen determinations in river and tap waters and its coupling to fiber optics for RTP in-situ monitoring or remote sensing of oxygen was evaluated.
Oxygen Water River Phosphorescence

"Introduction Of Hydrogen Peroxide As An Oxidant In Flow Injection Analysis: Speciation Of Chromium(III) And Chromium(VI)"
Anal. Chim. Acta 1998 Volume 361, Issue 1-2 Pages 125-131
Jens E. T. Andersen*

Abstract: Hydrogen peroxode was used as an oxidant in flow injection analysis (FIA). The formation of gaseous components during the analysis was suppressed by maintaining the concentration of H2O2 <0.15% in 0.1 M NaOH. By this method, Cr(III) was oxidized online to Cr(VI) which was detected spectrophotometrically at 548 nm by complexation with 1,5-diphenylcarbazide (DPC). Linear responses were found for concentrations. <20 mg/l and the sensitivities obtained of the pure species were 0.0225±0.0015 L/mg for Cr(III) and 0.0420±0.0015 L/mg for Cr(VI). For the speciation of Cr(III) and Cr(VI), the anal. of both species was performed by treating them as mutual interferences. Thus, the total amt. of Cr species was measured by FIA and the total amount of Cr was measured by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The speciation was performed at concentrations. >6 mg/L which is suitable for online monitoring of e.g. waste waters.
Chromium(III) Chromium(VI) Waste Spectrophotometry Sample preparation

"A Submersible Flow Injection-based Sensor For The Determination Of Total Oxidized Nitrogen In Coastal Waters"
Anal. Chim. Acta 1998 Volume 361, Issue 1-2 Pages 63-72
Anthony R. J. Davida, Trevor McCormacka, Alan W. Morrisb and Paul J. Worsfolda,*

Abstract: The design and construction of a remotely deployed submersible sensor for the determination of total oxidized nitrogen (nitrate plus nitrite) in seawater is described. It was based on the flow injection principle, with solid state spectrophotometric detection of the diazotization product from the reaction of nitrite with N-(1-naphthyl)ethylenediamine dihydrochloride (N1NED) and sulfanilamide. Nitrate was pre-reduced inline with a copperized cadmium powder column. The limit of detection (3 s) was 0.1 µM nitrate (1.4 µg N/L) and the linear range was 0.1-55 µM nitrate with a 20 mm path length flow cell and a 260 µL sample loop. The linear range was modified for different environmental conditions by changing the sample loop size and(or) the flow cell path length. Results are presented for preliminary lab. studies and field trials in the Tamar Estuary and for deployments in the North Sea. The sensor was successfully deployed on three sep. occasions for complete tidal cycles (13 h) at a depth of 4 m from the bow of the RRS Challenger. Field data are compared with results from a shipboard air segmented analyzer and correlated with turbidity and salinity data.
Nitrogen, total, oxidized Sea Spectrophotometry

"Determination Of Carbamate Residues In Crop Samples By Cholinesterase-based Biosensors And Chromatographic Techniques"
Anal. Chim. Acta 1998 Volume 362, Issue 1 Pages 59-68
Gilvanda Silva Nunes*, Petr Skl&aacute;dal, Hideko Yamanakacand Dami&aacute; Barcel&oacute;

Abstract: An amperometric biosensor based on cholinesterase (ChE) has been used for the determination of selected carbamate insecticides in vegetable samples. The linear range of the biosensor for the N-methylcarbamates (aldicarb, carbaryl, carbofuran, methomyl and propoxur) varied from 5 x 10^-5 to 50 mg kg-1. Limits of detection were calculated on the basis that the ChE enzymes were 10% inhibited and varied, depending of the combination ChE (as acetyl- or butyrylcholinesterase) vs. inhibitor (pesticide), from 1 x 10^-4 to 3.5 mg kg-1. The biosensor-based carbamate determination was compared to liquid chromatography/UV methods. Three vegetable samples were spiked with carbofuran and propoxur at 125 µg kg-1 followed by conventional procedures. Good correlations were observed for carbofuran in the vegetable extracts (79, 96 and 91% recoveries for potato, carrot and sweet pepper, respectively), whereas for propoxur unsatisfactory results were obtained. Potato and carrot samples were spiked with 10, 50 and 125 µg kg-1 carbofuran, followed by direct determination by the amperometric biosensor. The fortified sampler; resulted in very high inhibition values, and recoveries were: 28, 34 and 99% for potato, and 140, 90 and 101% for carrot, respectively, at these three fortification levels.
Ammonium carbamate hydrate Vegetable Vegetable Vegetable Amperometry Sensor

"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

"Online Separation And Spectrophotometric Determination Of Low Levels Of Aluminum In High-salt Content Samples: Application To Analysis Of Hemodialysis Fluids"
Anal. Chim. Acta 1998 Volume 362, Issue 2-3 Pages 163-169
Denise Bohrer*, Adriana Gioda, Regina Binotto and Paulo C&iacute;cero do Nascimento

Abstract: An online pre-concentration and matrix separation procedure for the spectrophotometric determination of low levels of aluminum in aqueous and high-salt content matrices was developed. Aluminum was pre-concentrated on polyethylene powder as a complex with Chrome azurol S and, after elution, the complex was spectrophotometrically determined, without interference of the matrix. The assayed salts were sodium, potassium, magnesium and calcium chlorides and sodium acetate, usually employed in hemodialysis fluids. A polyethylene powder column was incorporated to the flow system by using a microcolumn as the loop of a six-port valve connected to an injector and to the spectrophotometric detector. Effects of eluent composition and concentration, reactor length and influence of the presence of salts on the pre-concentration and elution steps were investigated. The proposed method was characterized by a precision of about 90% and a detection limit of 17 ng Al (6 x 10^-10 mol). Recoveries from spiked samples of the salts were between 87-110%, and results were in agreement with determinations by graphite furnace atomic absorption spectrometry. The method was applied to the analysis of saline concentrates and water for hemodialysis.
Aluminum Water Haemodialysis Fluid Spectrophotometry

"Flow Injection Conductimetric Or Spectrophotometric Analysis For Acidity In Fruit Juice"
Anal. Chim. Acta 1998 Volume 363, Issue 2-3 Pages 199-202
Kate Grudpan*, Piyanete Sritharathikhun and Jaroon Jakmunee

Abstract: Two flow injection (FI) procedures for the determination of acidity (expressed as citric acid content) in fruit juices are proposed: conductimetric involving injection into ammonia followed by gaseous diffusion into acetic acid; spectrophotometric FI titration in which the sample is mixed with sodium hydroxide in the presence of phenolphthalein. These procedures have been applied to the anal. of Thai fruit juices having acidity at a level of about 1% (wt./v) citric acid. The relative standard deviations (n=12) were within the ranges 3.6-6.2% and 0.7-2.2%, respectively, for the conductimetric and spectrophotometric procedures, the latter showing a negative bias due to the presence of colored matter in the samples. Sodium chloride and sucrose, when present in concentrations of up to 2% and 10% (wt./v) respectively, do not interfere. Results obtained by either procedures are consistent with those obtained by a standard classical titrimetric method.
Acidity, total Fruit Conductometry Spectrophotometry

"A Multicommutated Flow System With Online Compensation Of The Schlieren Effect Applied To The Spectrophotometric Determination Of Pindolol"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 209-215
Rui A. S. Lapa*, Jos&eacute; L. F. C. Lima, Boaventura F. Reis, Jo&atilde;o L. M. Santos and Elias A. G. Zagatto

Abstract: A continuous-flow methodology for the spectrophotometric determination of pindolol in pharmaceutical preparations following complexation with Fe(III) chloride is described. The reaction is carried out within a multicommutated flow network using a binary sampling approach. The Schlieren effect, associated with the pronounced concentration. gradients in FIA system, was compensated by using a carrier solution processed online with two alternating solutions The concentration. profiles of the resulting carrier solution and the sample plug were similar, a fact that prevented the formation of concentration. gradients. Absorbance was measured at 635 nm. Beer law was followed for concentrations. up to 120 µg pindolol/mL. Results were reproducible (RSD <1.1%, n=10) and in agreement with data obtained by a reference procedure. A rate of 30 samples per h was attained.
Pindolol Pharmaceutical Spectrophotometry

"Flow Injection Conductometric Determination Of Acidity In Industrial Hydrated Ethyl Alcohol"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 81-85
Orlando Fatibello-Filho* and Maria Teresa Mendes Ribeiro Borges

Abstract: A flow injection (FI) conductometric procedure is proposed for the determination of acidity in industrial 96%(v/v) hydrated ethyl alcohol. The method consists in a single-line system in which an alkaline solution (sodium hydroxide), in excess, was used as carrier. When the sample is inserted in the flow system, it mixes with and partially neutralizes the carrier solution, causing a decrease on the sample zone conductance, proportional to the sample acidity. The best conditions found were an anal. path of 100 cm, injection sample volume of 50 µL, temperature of 20°C and 1.0 x 10^-3 mol L-1 sodium hydroxide as reagent carrier. With a single-channel manifold, 96%(v/v) ethyl alcohol acidity was determined in the 0.60-15.00 mg HOAc/100 mL concentration. range (expressed as acetic acid) (calibration graph: H = -49.141-2.447C, r = 0.9989, where H is the peak height in mm and C is the acetic acid concentration in 96%(v/v) ethyl alcohol in mg HOAc/100 mL) with a detection limit (three times the signal blank/slope) of 0.51 mg HOAc/100 mL. The throughput was 120 results h-1 and potassium chloride solution up to concentration of 11.48 mg KCl/100 mL injected together 2.40 mg HOAc/100 mL 96% v/v Et alcohol solution does not cause any effect in the conductometric response. A 2.40 mg HOAc/100 mL 96%(v/v). Ethyl alcohol solution gave a relative standard deviation <1% (n = 15) and the results obtained for four industrial, hydrated Et alcohol with this procedure are in close agreement with those obtained using the titration procedure (r = 0.9991).
Acidity Organic compound Conductometry

"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

"Automatic Determination Of Iron In Geothermal Fluids Containing High Dissolved Sulfur-compounds Using Flow Injection Electrothermal Atomic Absorption Spectrometry With An Online Microwave Radiation Precipitation-dissolution System"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 295-303
J. L. Burguera*, M. Burguera and C. E. Rondon

Abstract: A flow injection sample introduction in electrothermal atomic absorption spectrometry was used to determine iron in geothermal fluids containing high concentration. of dissolved sulfate and sulfide anions. First, sulfide was pptd. as sulfur with a confluencing solution of hydrogen peroxide (10% v/v) on the walls of a knotted reactor exposed to microwave radiation, to ease the precipitation process. While the sulfate containing solution flows downstream and sequestered in a sampling arm for the sequential deposition of aliquots of sample on the graphite tube atomizer platform bypositive air displacement, sulfur was dissolved with CCl4 and diverted to waste. This sequence was timed to synchronize with the spectrometer computer, which had been pre-programmed to introduce aliquots of Lu modifier, previous to each sample deposition, to minimize the sulfate interference, to improve integrated absorbance signal and the reproducibility of measurements. By using the less sensitive iron line at 296.7 nm, the linear range was 12-280 µg L-1, with a characteristic slope of 0.00083, a characteristic mass of 104.8 pg and a detection limit of 72 pg (3.6 µg L-1). The precision of the method, obtained for 10 measurements, was studied as within-run and within-batch precision; the relative standard deviations obtained in both cases were <3%. The accuracy of geothermal fluids was checked by recovery tests and comparison with an independent anal. method. Results obtained by the here proposed method correlate closely with those obtained by a tedious photometric procedure with o-phenanthroline. The sensitivity and the simplicity of this online procedure makes it attractive for routine determination of iron in waters involving large throughput of samples.
Iron Geothermal Spectrophotometry

"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

"Enzymic Determination Of L(+) Lactic And L(-) Malic Acids In Wines By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 187-191
Jos&eacute; L. F. C. Limaa, Teresa I. M. S. Lopesb and Ant&oacute;nio O. S. S. Rangelb,*

Abstract: A flow injection system for the enzymatic determination of L(+) lactic acid and L(-) malic acid in wines with spectrophotometric detection is described. The samples are dialyzed inline, and the enzymes in solution (malate dehydrogenase and lactate dehydrogenase) are injected as a train of plugs in the acceptor stream of the dialysis unit, yielding two peaks corresponding to the NADH formed for each determination This methodology enables the determination of both acids with a single detector with a sampling rate of 20 h-1 (0.4-3 g L-1). The results are comparable to those obtained by the reference procedure, the repeatability is better than 5% (rsd), with low enzyme consumption (1.3 µL of suspension per sample).
l-Lactate l-Malic acid Wine Spectrophotometry

"Potentiometric Flow Injection Determination Of Cadmium In Waste Waters Including Inline Ion-exchange Separation/concentration"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 155-161
Cristina M. C. M. Coutoa, Jos&eacute; L. F. C. Limaa, M. Concei&ccedil;&atilde;o B. S. M. Montenegroa, Boaventura F. Reisb and Elias A. G. Zagattob,*

Abstract: A flow injection system including an ion exchange resin mini-column was proposed for potentiometric determination of Cd in wastewater. Cd was preferential and quantitatively retained as chloro-complex by a strongly basic anion exchange resin (AG 1-X8, 200-400 mesh, chloride form) mini-column (2.0 cm height, 1.85 mm inside diameter), whereas other sample metallic cations and inert components were wasted. Retained complexes were further eluted towards detection. The flow-through detector was a Cd homogeneous crystalline double membrane tubular electrode of increased sensitivity; summation of the potentials related to each membrane was performed using an external electronic device. This system was used to determine Cd in residual wastewater; Cd concentrations were 0.056-56.2 mg/L. Precise results (relative standard deviation ~7%) in agreement with those obtained by flame atomic absorption spectrometry were obtained at a rate of 15-20 determinations/h.
Cadmium Waste Potentiometry Ion exchange Electrode Electrode

"Automated Flow Injection System For Extending The Linear Range"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 271-279
Luis F. Gouveia, Jos&eacute; L. F. Costa Limab and Jos&eacute; A. G. Moraisa,*

Abstract: A flow system with built-in capability to adjust injection volume whenever sample concentration. is higher than the upper linearity limit was developed and its performance assessed. Solenoid valves were used to manage sample and carrier delivery. Whenever the peak height is higher than the calculated linearity limit an injection volume adjustment is made to a 2nd determination of the same sample in such a way that the peak height will be in the linear range. Extended linear range is therefore achieved without sacrificing detection of low concentration. samples. Calibration, calculation of the upper linearity limit and model fitting to calibration data (peak height vs. concentration. and peak height vs. injection volume) are automatically performed with no human intervention. Performance was tested upon assessing dissolution profiles of cephalexin tablets in a low dispersion manifold with direct UV determination The proposed system presents a 180 determinations h-1 throughput. Sample aspiration time was calibrated in the range 50-2000 ms, thus allowing quantification up to 1250 mg L-1 of cephalexin. Precision is ~0.95% relative standard deviation when sample is aspirated for 2000 ms. Results obtained are comparable to those obtained by using the reference procedure.
Cephalexin Pharmaceutical Spectrophotometry

"Flow Injection Spectrophotometric Determination Of L-ascorbic Acid In Pharmaceutical Formulations With Online Solid Phase Reactor Containing Copper(II) Phosphate"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 55-62
Airton Vicente Pereira and Orlando Fatibello-Filho*

Abstract: A spectrophotometric flow injection analysis (FIA) method is proposed for the determination of L-ascorbic acid in pharmaceutical formulations using the reproducibility and stability of a solid phase reactor containing copper(II) phosphate immobilized on a polyester resin matrix. The determination is accomplished by the reduction of Cu(II) ion to Cu(I), which is carried away by acetate buffer (pH 4.5) and detected by monitoring the absorbance (480 nm) of the chelate produced by the reaction between Cu(I) and bathocuproine. The calibration graph for L-ascorbic acid was linear from 5.0 x 10^-6 to 4.0 x 10^-5 M with a correlation coefficient of 0.9998. The detection limit (3-times the signal blank/slope) was 3.0 x 10^-7 M ascorbic acid. The relative standard deviation was 0.75% for 2.0 x 10^-5 M ascorbic acid (n =10) and 80 samples could be analyzed per h. The recovery of ascorbic acid from 6 samples ranged from 97.3 to 103.4% of the amt. added. The concentrations of ascorbic acid determined by the proposed FIA-spectrophotometric method were in a close agreement with data obtained with the official Pharmacopeia method.
l-Ascorbic acid Pharmaceutical Spectrophotometry

"Automatic Multicommutation Flow System For Wide Range Spectrophotometric Calcium Determination"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 45-53
F&aacute;bio R. P. Rocha, Patr&iacute;cia B. Martelli, Rejane M. Frizzarin and Boaventura F. Reis*

Abstract: An automatic flow system based on multicommutation concept is proposed to widen the linear concentration range for spectrophotometric calcium determination The flow network was build up with three way solenoid valves to permit implementation of different sample processing conditions to achieve limited, medium and large dispersion degree without modification of the manifold configuration. Dilutions were carried out by changing both sampled volume and the analysis path length or applying zone sampling approach. The software was developed to control all steps of sample processing and to allow changing the manifold configuration to obtain suitable sample dilution This condition was attained with up to 3 trials. A linear response from 0.250 to 1000 mg L-1, and a detection limit of 7 µg L-1 (99.7% confidence level) were achieved. The relative standard deviation was 0.83% (n = 10) or better. The sampling rate was ~60 h-1 and 0.27 µg of the chromogenic reagent (3,3'-bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolphthalein) was consumed per determination The procedure was applied to calcium determination in waters, plant materials, milk, antacid tablets, fertilizers and calcareous rocks. The results were in agreement with certified values or with those obtained with flame atomic absorption spectrophotometry at a 95% confidence level.
Calcium Environmental Plant Cow Pharmaceutical Commercial product Calcareous Spectrophotometry

"Sampling Strategies In Sequential Injection Analysis. Exploiting The Monosegmented-flow Approach"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 257-262
Jonas A. Vieiraa, Ivo M. Raimundo, Jr.a, Boaventura F. Reisb,*, Elias A. G. Zagattob and Jos&eacute; L. F. C. Limac

Abstract: An evaluation of different sampling techniques employing sequential injection analysis (SIA) is described. The reaction between Fe(II) and 1,10-phenanthroline, which needs a pH adjustment with acetate buffer and a prior reduction with hydroxylamine solution, was employed. As a general rule, sensitivity, compared to that of the usual SIA technique, can be enhanced with binary sampling, sandwich sampling and monosegmented flow, in that order. Under the employed conditions, signals 13, 31 and 58% higher than those provided by conventional SIA can be obtained with the binary, sandwich and monosegmented sampling, respectively. The monosegmented-flow approach was applied in determining Fe in natural waters and results do not differ significantly from those obtained by ICP/AES at the 95% confidence level. The precision was 1.1%, expressed as relative standard deviation obtained by the measurement of nine replicates of 1.0 mg L-1 Fe(III) reference solution.
Iron(2+) Environmental Spectrophotometry

"Flow Injection Spectrophotometric Catalytic Determination Of Manganese In Plants Exploiting The Aerial Oxidation Of Diphenylcarbazone"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 87-92
Nelson Maniasso and Elias A. G. Zagatto*

Abstract: The catalytic effect of Mn(II) on the aerial oxidation of diphenylcarbazone (DFC) becomes very pronounced in the presence of triethanolamine (TEA), whereas the influence of other potential interferents is strongly reduced. This feature was exploited to develop an improved flow injection procedure for Mn determination in plant digests. In view of the high variability of Mn contents in the sample batches, an approach involving two sampling loops was implemented to widen the dynamic range. The proposed system handles ~70 samples per h, requires only 0.13 mg DFC and 85.7 mg TEA per determination, and yields reproducible signals (relative standard deviation of peak heights usually<2%) within two different concentration. ranges (0.10-0.80 and 0.50-4.00 mg L-1 Mn). Detection limit is 0.03 mg L-1 Mn in the digest (3 µg g-1-dry basis). Results are in agreement with flame atomic absorption spectrometry. A noteworthy feature of this procedure is the negligible progress of the uncatalyzed reaction.
Manganese Plant Spectrophotometry

"Acetylsalicylic Acid Determination In Pharmaceutical Samples By FIA-potentiometry Using A Salicylate-sensitive Tubular Electrode With An Ethylene-vinyl Acetate Membrane"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 103-109
La&eacute;rcio Rover Jr., Carlos Alexandre Borges Garcia, Graciliano de Oliveira Neto*, Lauro Tatsuo Kubota and Fernando Galembeck

Abstract: The preparation of a salicylate-sensitive tubular potentiometric electrode for flow injection analysis (FIA) is described. An ethylene-vinyl acetate (EVA) copolymeric membrane (40% vinyl acetate) was applied directly onto a conducting support of epoxy resin/graphite mixture. The tubular salicylate ion-selective electrode was based on tricaprylyl trimethylammonium (Aliquat)/salicylate as the ion exchanger supported by the polymeric matrix without a plasticizer solvent. The tubular electrode showed a response of 58.3 mV per concentration decade within the 5.0 x 10^-3 to 5.0 x 10^-1 M salicylate range in 0.1 M Tris-HCl buffer pH 7.5. Iodide was the main anal. interferent. The electrode response time was 5 s at 25°C. Acetylsalicylic acid in tablets was hydrolyzed with NaOH before FIA determination. Determinations of acetylsalicylic acid in tablets by the proposed method showed relative errors <2%, when compared with a standard spectrophotometric method. The useful lifetime of the tubular sensor is >3 months.
Acetylsalicylic acid Pharmaceutical Electrode Electrode Potentiometry Electrode

"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

"Determination Of Vanadium(V) By A Kinetic Stopped-flow FIA Method With Spectrophotometric Detection"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 287-293
M. E. Palomeque, A. G. Lista and B. S. Fern&aacute;ndez Band*

Abstract: Two automated methods to determine V5+ in water are described. A continuous-flow system based on the classical reaction for V5+ determination with 3,3'dimethylnaphtidine in acid medium using a stopped-flow technique and spectrophotometric detection was developed (Method A). It was possible to increase reaction kinetics to obtain a higher sample throughput (34/h), lower detection limits (0.2 mg/L), and high sensitivity. To determine still a lower V5+ concentrations, a pre-concentration step was introduced in the above system (Method B). This manifold has a lower detection limits (0.032 µg/mL) and high sensitivity (4 times greater than Method A). Both methods showed a good reproducibility (relative standard deviation for Method A = 1.9% and for Method B = 2.3%).
Vanadium(V) Water Spectrophotometry

"Calibration Procedure For Flow Injection Flame Atomic Absorption Spectrometry With Interferents As Spectrochemical Buffers"
Anal. Chim. Acta 1998 Volume 367, Issue 1-3 Pages 101-110
Pawe

Abstract: The flow injection calibration procedure was developed to correct for interferences in flame atomic absorption spectrometry. For this purpose a sample and standard solutions were injected one after the other into the carrier stream containing some reagents known to usually produce strong interference effects. Affecting the analyte in both zones to the same extent they were able to act as spectrochem. buffers. As an example, calcium in synthetic samples containing aluminum, titanium and vanadium, and also in iron ore samples, was determined The procedure appeared to be quite effective in overcoming interferences even as strong as nearly 90%, providing anal. results with average accuracy equal to ~5%. Precision attained was 2-3 times inferior than that obtained using conventional FI calibration.
Calcium Iron Spectrophotometry

"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

"Simultaneous Determination Of Trace Amounts Of Nickel, Copper And Mercury By Liquid Chromatography Coupled With Flow Injection Online Derivatization And Preconcentration"
Anal. Chim. Acta 1998 Volume 369, Issue 3 Pages 215-223
Akbar Ali, Hong Shen and Xuefeng Yin*

Abstract: Reversed phase liquid chromatography (LC) combined with flow injection (FI) online derivatization and pre-concentration resulted in a sensitive technique for analyzes of multi-metals at trace levels. A new home-designed micro-pre-concentration column containing RP-C18 material as solid sorbent, accommodated in a pressure-tight housing of stainless steel, combined with an LC six port valve was used to interface the flow injection online derivatization and pre-concentration system to the LC equipment. This pre-concentration column, which can be used for online derivatization and pre-concentration using peristaltic pump, proved to be strong enough to bear the high pressure of the LC eluent. Based on this FI-LC system, a method for the determination of Ni(II), Cu(II), and Hg(II) in water samples as their diethyldithiocarbamate (DDC) complexes was developed. A MeOH/H2O mixture (80:20 v/v) as LC eluent and intelligent UV detector programmed in time for absorption measurement at the max. absorption wavelength of the respectively. metal-DDC complexes were used. The detection limits were (signal : noise = 3) 0.16, 0.41 and 1.1 µg L-1 for Ni, Cu and Hg, respectively.; and the relative standard deviations were 3.6, 4.5 and 3.9% for Ni(II) (0.10 mg L-1), Cu(II) (0.10 mg L-1) and Hg(II) (0.40 mg L-1) (n = 6), respectively. The developed method was successfully applied to wastewater samples from an elec. power station and a machine tool factory and the results agreed with values determined by atomic absorption spectrometry.
Nickel Copper Mercury Industrial HPLC Spectrophotometry

"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

Abstract: A urea biosensor with urease covalently bound directly to the membrane of the ammonium ion selective electrode was developed. The enzyme electrode was tested in single and double channel flow injection analysis (FIA) systems. Optimized measurement conditions allowed determination of urea within the linear range of 0.5-8 mM in the single channel and of 1-10 mM in the double channel FIA system. The response time of the biosensor was short enabling frequent sample injections (every 1.5-3 min). Long term stability of the enzyme electrode allows application of the same biosensor in the FIA systems for up to two months. Under optimized conditions the determination of urea is possible at physiol. and pathological levels. The results of urea determination in real, human serum samples were in good agreement with those obtained by routine clinical analytical methods.
Urea Serum Human Potentiometry Electrode Electrode

"Sample Preparation In Sequential Injection Analysis. Spectrophotometric Determination Of Total Phosphorus In Food Samples"
Anal. Chim. Acta 1998 Volume 371, Issue 1 Pages 57-62
Cl&aacute;udio Celestino Oliveiraa, Elias Ayres Guidetti Zagattoa,*, Alberto N. Ara&uacute;djob and Jos&eacute; Luis F. Costa Limab

Abstract: A sequential injection (SI) procedure involving inline sample preparation is proposed. A natural suspension or a slurry is transported together with nitric acid towards a home-made digestion bomb placed inside a microwave oven for subsequent digestion. The sample zone is stopped inside the oven and, after digestion, directed in reverse flow towards a holding coil and then towards detection. This is a good strategy because the SI system is versatile; the formed air bubbles are efficiently disposed of, thus avoiding the need for a debubbler unit, and the digestion bomb acts also as a mixing device promoting easy homogenization regardless of the number of required reagents. As application, the spectrophotometric determination of total phosphorus in foodstuffs based on the molybdenum blue method was selected. The proposed system is very robust and yields reproducible measurements, (RSD usually <3%) for 20.0-400.0 mg L-1 P-PO4. Results are in agreement with a conventional spectrophotometric procedure involving manual sample digestion.
Phosphorus Food Spectrophotometry Sample preparation

"Sequential Injection Sandwich Technique For The Simultaneous Determination Of Nitrate And Nitrite"
Anal. Chim. Acta 1998 Volume 371, Issue 1 Pages 63-71
A. Cerd&agrave;, M. T. Oms, R. Forteza and V. Cerd&agrave;*

Abstract: An automated sequential injection system for monitoring nitrate and nitrite in water samples is described. The method enables the simultaneous determination of both parameters with a single injection of sample. A sandwich arrangement, in which the sample is placed between two Griess reagent zones, is adopted. Nitrite is determined in one end of the sample zone by diazotization-coupling reactions and spectrophotometric detection of the azo dye formed. In the other end, nitrate is similarly determined after its online reduction to nitrite using a copperised cadmium column. The calibration is linear over the range 0.5-40 µmol L-1 nitrite and 2-100 µmol L-1 nitrate, the mid-range relative standard deviations being <2% in both the cases. Under optimized conditions the system has been applied to the determination of nitrate in tap, mineral and sea waters (the nitrite concentration. was below the detection limit) and the results have been compared with those obtained by ion chromatography and a flow injection system based on the same reactions.
Nitrate Nitrite Water Mineral Sea Spectrophotometry

"Microwave-assisted Saponification Of Animal Greases For Cholesterol Determination"
Anal. Chim. Acta 1998 Volume 371, Issue 2-3 Pages 297-303
Gerardo Pi&ntilde;eiro-Avila, Amparo Salvador and Miguel de la Guardia

Abstract: An alternative method for the hydrolysis of cholesterol esters in animal grease samples has been developed. The method consists of the microwave-assisted treatment of 4 g of animal fat or oil with 40 mL of an ethanolic KOH solution inside a 115 mL closed reactor in which samples were irradiated for 2.5 min at 50% power level of an exit power of 700 W. After extraction with petroleum ether and dissolution of the unsaponifiables in toluene, total cholesterol was determined spectrophotometrically by using p-anisidine as a test reagent of the enzymatic reaction of cholesterol through a bienzymic reactor in which cholesterol oxidase and horseradish peroxidase were noncovalently immobilized in controlled pore,glass beads. The method provided a quantitative recovery of spiked free cholesterol (100% recovery for an added concentration level of 36 mg g-1) and cholesteryl palmitate (98.7% recovery for an added concentration of 37 mg g-1) and results comparable to those obtained after saponification with ethanolic KOH at 90°C under reflux conditions for 1 h, saving a considerable time with a comparable figures of merit which involve a limit of detection of 1 x 10^-6 M total cholesterol an average interday relative standard deviation of 3.5% for three independent analysis of a series of different samples.
Cholesterol Fat Sample preparation Spectrophotometry

"New Fructose Biosensors Utilizing A Polypyrrole Film And D-fructose 5-dehydrogenase Immobilized By Different Processes"
Anal. Chim. Acta 1998 Volume 374, Issue 2-3 Pages 201-208
C. A. B. Garcia, G. de Oliveira Neto* and L. T. Kubota

Abstract: Two amperometric biosensors for fructose detection were developed by immobilizing D-fructose 5-dehydrogenase by two different immobilization processes. For the first biosensor, the occlusion enzymatic immobilization technique was employed, the enzyme being immobilized in a polypyrrole (PPY) film, over a platinum electrode containing sodium ferricyanide as mediator. With this sensor, about 100 analyzes were performed over a period of 1 week with daily use. The second was constructed using the crosslinked covalent bond method, the enzyme being immobilized onto a PPY film doped with hexacyanoferrate supported on a platinum electrode surface. This biosensor was used for, approximately, 200 analyzes in 2 weeks of continuous use. Analytical parameters, such as pH, ionic strength, interferences and response time of both sensors were also studied. The biosensors were utilized for fructose determinations in three different samples of dietetic products and presented a good correlation with the standard colorimetric method. A linear response range to both biosensors was 0.1-0.8 mmol L-1 fructose with a RSD of 0.68%.
Fructose Sensor Amperometry Electrode Electrode Electrode

"Combination Of Flow Injection With Capillary Electrophoresis. 4. Automated Multicomponent Monitoring Of Drug Dissolution"
Anal. Chim. Acta 1998 Volume 376, Issue 2 Pages 209-220
Heng-Wu Chen and Zhao-Lun Fang*

Abstract: The combined flow injection-capillary electrophoresis (FI-CE) system, described previously in this series, was used in connection with a drug dissolution testing system to automatically monitor the dissolution process of multicomponents. Samples from the dissolution medium were withdrawn at fixed intervals through an online membrane filter to load the sample loop of an injection valve, from which 25 µL samples were injected into a carrier buffer and transported into a split-flow interface coupling the FI and CE systems. Trimethoprim (TMP) and sulfamethoxazole (SMZ), the two active components in a sulfatrim tablet formulation dissolved in 0.1 mol L-1 HCl, were introduced into a short silica separation capillary of 14.5 cm effective length by electrokinetic means, separated at a constant voltage of 1.0 kV by capillary zone electrophoresis, using a phosphate running buffer (pH 6.5), and the separated constituents recorded continuously, using an UV detector at 224 nm. The signals were recorded within a testing period of 65 min. By partially overlapping the separation zones of neighboring samples, a high sample throughput of 60 h-1 was achieved with single-vessel dissolution and 48 (24 duplicates) h-1 with dual-vessel dissolution The reproducibility of the FI-CE system, obtained using TMP and SMZ standards within the testing period was 1.6 and 0.8% relative standard deviation (RSD) with peak height evaluation, and 2.0 and 1.1% RSD (n=72), respectively, for peak area. Good agreement of results was obtained between those using the reported method and a standard liquid chromatography method.
Trimethoprim Sulfamethoxazole Pharmaceutical Electrophoresis

"Continuous Sample Recirculation In An Opened-loop Multicommutated Flow System"
Anal. Chim. Acta 1998 Volume 377, Issue 1 Pages 103-110
Rui A. S. Lapa*, Jos&eacute; L. F. C. Lima, Boaventura F. Reis and Jo&atilde;o L. M. Santos

Abstract: A continuous circulating multicommutated flow system based on an opened-loop configuration is proposed. The sample is inserted into the flow system and continuously recirculated until a suitable dilution level is attained, which is permanently surveyed by including the detector in the circular reactor. A continuous removal of the highly dispersed front and trailing zones of the sample plug improves dilution efficiency. The chromogenic reagent used as carrier solution is permanently renewed, which contributes to a constant renewal of the reaction zone increasing the reaction rate by reducing its dependence on the dispersion at the sample/reagent interface. The developed methodology was tested in the determination of chloride in parenteral solutions by the formation of the Fe (III) thiocyanate complex with expansion of the linear range of determination up to 10,000 mg L-1. Results were reproducible (relative standard deviation <1.8%) and in agreement with those obtained by the conventional procedure.
Chloride Parenteral Fluid Spectrophotometry

"Spectrometric Rapid Sampling - Mixing System For Analytical - Clinical Methods"
Talanta 1979 Volume 26, Issue 7 Pages 549-561
D. L. Krottinger, M. S. McCracken and H. V. Malmstadt*

Abstract: A rapid sampling/mixing system has been designed which conforms to certain criteria necessary for its use as a clinical analyzer.. These include low solution volume (<100 µL) for each determination on a sample, rapid cycle time (<2 sec to take an aliquot, mix and transfer reactants to an observation cell), good precision (reproducibility better than 0.2%), and ready automation (requiring only two electronic signals to perform a complete cycle). This device has been incorporated into an automated spectrophotometer to be used for a variety of clinical methods. Equilibrium methods for the determination of calcium and albumin are presented that require measurement times of only 6 and 7 sec, respectively. A reaction-rate procedure for total protein is presented that requires only 3 sec per sample. Precisions obtained with these procedures are typically better than 1% in the normal serum range. Results on samples from hospital patients are compared with values obtained on an SMA 12/60 instrument.
Calcium Albumin Protein, total Blood Serum Clinical analysis Spectrophotometry

"Flow Injection Determination Of Ergonovine Maleate With Amperometric Detection At The Kel-F-graphite Composite Electrode"
Talanta 1986 Volume 33, Issue 5 Pages 448-450
F. Belal* and J. L. Anderson

Abstract: Tablets containing ergometrine maleate(I) were powdered and dissolved in the mobile phase [methanol - 0.01 M phosphate buffer - 2% Na acetate (pH 7) (1:4)] and subjected to flow injection analysis with amperometric detection with a Kel-F - graphite electrode at +0.85 V vs. silver - AgCl. The calibration graph was rectilinear for 1 to 20 µg mL-1 of I and the detection limit was 50 ng mL-1. The coefficient of variation were 1%, and the results agreed well with those obtained by the official USP method.
Drugs Ergometrine maleate Pharmaceutical Amperometry Electrode

"Determination Of Levamisole Hydrochloride With Tetraiodomercurate(2-) By A Turbidimetric Method And Flow Injection Analysis"
Talanta 1986 Volume 33, Issue 8 Pages 685-687
J. Martinez Calatayud* and Campins Falco

Abstract: Sample solution (200 µL) is injected into a reagent stream (3.14 mL min-1) containing 8.55 mM Hg(I)42- (pH adjusted to 5 with phosphate - citrate buffer solution) which is then passed through a reaction coil (77 cm x 0.5 mm) resulting in the formation and precipitation of a levamisole(I) - Hg(I)42- ion-association complex (2:1); the absorbance of the suspension is measured at 430 nm. Calibration graphs are rectilinear from 7 to 32 µg mL-1 of I. In the determination of 91 µM-I, the coefficient of variation was 0.9% (n = 40). The method was used to determine I in pharmaceutical preparations also containing chlorpheniramine, giving results which agreed with those of a bromocresol purple method.
Drugs Levamisole hydrochloride Pharmaceutical Turbidimetry Sample preparation

"Fluorimetric Determination Of Nitrite In Natural Waters With 3-aminonaphthalene-1, 5-disulfonic Acid By Flow Injection Analysis"
Talanta 1986 Volume 33, Issue 9 Pages 729-732
Shoji Motomizu, Hiroshi Mikasa and Kyoji T&ocirc;ei

Abstract: Nitrite was determined in a flow injection system with water as carrier, and 10 µM-3-aminonaphthalene-1,5-disulfonic acid - 1 mM Na2EDTA - 2 M HCl as reagent stream. Following reaction in a PTFE tube (13 m x 0.5 mm) at 90°C, the stream was mixed with aqueous 20% NaOH solution, and the resulting azoic acid salt was detected spectrofluorimetrically at 470 nm (excitation at 365 nm). Calibration graphs rectilinear over various ranges from 0.1 to 50 µM were obtained by varying the sensitivity of the detector. The detection limit was 1 nM and the coefficient of variation at 1 µM was 0.4% (n = 10). Sodium chloride (>0.2M) interfered, but many ions did not. Results for various natural waters agreed well with those of other methods.
Nitrite River Sea Fluorescence

"Spectrophotometric Determination Of Bromide And Iodide In A Flow System After Oxidation By Peroxodisulfate"
Talanta 1987 Volume 34, Issue 7 Pages 615-618
Annika Carlsson, Ulla Lundstr&ouml;m and &Aring;ke Olin*

Abstract: An earlier method (cf. Lundstrom, Ibid., 1982, 29, 291) for the determination of Br- was modified to include flow injection spectrophotometric measurement and a smaller ion-exchange column for pre-concentration. Sample solution containing BrO3- and IO3- obtained by oxidation of Br- and I- is mixed with a carrier solution containing 0.2 M NaCl, 1 M NaClO4, 0.05 M Na2SO4, 0.09 M NaH2PO4 and 0.01 M Na2HPO4 before detection at 355 nm. Calibration graphs are rectilinear for 1 to 15 µM and the limit of detection is 0.7 µM for both IO3- and IO3- plus BrO3-. The injection frequency is 60 h-1. Results were compared with those obtained by the original method and agreed to within ±1.5%. The method was applied to water samples.
Bromide Iodide Environmental Spectrophotometry

"Continuous-flow Determination Of Chloride In The Nonlinear Response Region With A Tubular Chloride Ion-selective Electrode"
Talanta 1987 Volume 34, Issue 11 Pages 921-926
Hirokazu Hara* and Yoshiki WakizakaSatoshi Okazaki

Abstract: The tubular electrode is constructed from copper pipe (2 cm x 0.28 cm) plated internally with silver, which is then electro-oxidized in 0.1 M KCl to form a AgCl layer. This electrode is used in conjunction with an Orion double-junction reference electrode containing 1 M NaNO3 in 30% methanol solution as outer filling solution The electrode is incorporated into a microcomputer-aided flow system in which sample or standard solution is mixed with colloidal AgCl solution to remove Br- and I- before the sample is passed through the tubular electrode. The concentration. is interpolated with use of the spline function in the range 0.1 to 10 mg L-1 and the corresponding coefficient of variation were 10 to 2% (n = 5). The detection limit is ~0.1 mg l-1. Results of analysis of rain and snow containing >0.75 mg L-1 of Cl-1 agreed within 10% of those of ion chromatography (n = 12).
Chloride Snow Rain Electrode Potentiometry

"Manual And Flow Injection Analysis Methods For The Determination Of Cadmium With Malachite Green And Iodide"
Talanta 1988 Volume 35, Issue 11 Pages 885-889
I. Lopez Garcia, P. Navarro and M. Hernandez Cordoba

Abstract: Sample solution (20 ml) containing 50 µg of Cd was mixed with 1 mL of KI - ascorbic acid solution, 1 mL of 2 M acetate buffer solution (pH 4) and 2 mL of poly(vinyl alcohol) solution, and then 1 mL of malachite greeen(I) solution was added. After 15 min, the absorbance was measured at 685 nm vs. a reagent blank. Beer's law was obeyed for 0.04 to 2 µg mL-1 of Cd. The coefficient of variation (n = 10) for 1 µg mL-1 of Cd was 1.7%. The method was adapted for flow injection analysis by using a two-channel manifold with reaction coils of 1 m and 25 cm (both i.d. 0.5 mm) and flow rates of 1.4 mL min-1. The optimum concentration. for carrier solution were 0.08 M KI and 0.25 mM I both in 0.1 M acetate buffer (pH 4). The calibration graph was rectilinear for 0.1 to 3 µg mL-1 of Cd, and the coefficient of variation for 1.5 µg mL-1 of Cd was 1.8%. Tolerance levels for foreign ions are tabulated. The flow injection method was more selective than the batch method. The method was applied to determine Cd in solution from Zn manufacturing, and results agreed with those obtained by AAS. Recovery of Cd was 99 to 102%.
Cadmium Process liquor Spectrophotometry

"Air-carrier Continuous Analysis System"
Talanta 1989 Volume 36, Issue 1-2 Pages 49-61
Kaj Petersen and Purnendu K. Dasgupta*

Abstract: An air-carrier continuous analysis system is described which allows the reaction of a fixed volume of sample with fixed volume of one or more reagents, either simultaneously or sequentially. The system is intended to complement segmented continuous-flow and flow injection analysis, and is capable of high throughput rates (~3600 samples h-1) and low waste generation, but suffers from carry-over problems.

"Improvements In The NN-diethyl-p-phenylenediamine Method For The Determination Of Free And Combined Residual Chlorine Through The Use Of FIA"
Talanta 1991 Volume 38, Issue 2 Pages 145-149
G. Gordon, D. L. Sweetin, K. Smith and G. E. Pacey

Abstract: Buffer solution (pH 6.3) was mixed sequentially with NN-diethyl-p-phenylenediamine (I) solution and a stream of water containing the sample. After passage of the mixture through a 30-cm reaction coil, the absorbance of the solution was measured at 520 nm to give free Cl. For the determination of total Cl, the eluate was mixed with KI solution, passed through a 40-cm reaction coil and the absorbance of the solution was measured at 520 nm; combined Cl was determined by difference. The rectilinear range of the calibration graph was extended (to 0.1 to 8 mg L-1 of Cl) and coefficient of variation were improved (to 0.5 to 3%), compared with colorimetric or titrimetric methods involving I. The detection limit was 0.07 mg L-1 of Cl.
Chlorine, free Chlorine, residual Water Spectrophotometry

"Flow Injection Stopped-flow Kinetic Spectrophotometric Determination Of Drugs, Based On Micellar-catalysed Reaction With 1-fluoro-2,4-dinitrobenzene"
Talanta 1991 Volume 38, Issue 7 Pages 689-696
Constantinos A. Georgiou, Michael A. Koupparis* and Themistocles P. Hadjiioannou,

Abstract: Dihydralazine (I), isoniazid (II), levodopa (III) and aspartame (IV) are determined in a flow injection system in which a solution of 8.40 mM 1-fluoro-2,4-dintrobenzene in aqueous 20% ethanol acidified with 1 mM HCl was pre-mixed with 0.10 M borate buffer (pH 9.5) containing hexadecyltrimethyl-ammonium bromide (3.5 mM for I and II, 1.5 mM for III and IV) before merging with the aqueous injected sample stream. After mixing, the reaction mixture flow was stopped for 16 s followed by 2 s of mixture equilibration before multiple (40 to 256) absorbance measurements were recorded during 15 to 40 s at 428 nm for I and II and 340 and 342 nm for III and IV, respectively. The calibration graphs were rectilinear from 0.01 to 0.2 mM (III) and from 0.05, 0.01 and 0.06 to 0.6 mM (I, II and IV, respectively), and the respective detection limits were 18, 0.9, 6.3 and 20 µM for I, II, III and IV. The method, which may also be used to determine several other drugs which form soluble derivatives with the reagent, was used to determine II, III and IV in pharmaceutical formulations, II in formulations containing rifamycin, and IV in colored beverages. The results agreed well with those of reference methods.
Drugs Pharmaceutical Beverage Spectrophotometry

"Indirect Determination Of The Pesticide Dimethoxydithiophosphate In An FIA - AAS System With Liquid - Liquid Back-extraction"
Talanta 1991 Volume 38, Issue 8 Pages 857-861
Oroncio Jimenez de Blas, Jose Luis Pereda de Paz and Jesus Hernandez Mendez

Abstract: In the cited FIA - AAS system (details and diagram given) dimethoxydithiophosphate (I) was shaken with 0.01 M nitric acid, CHCl3 and an excess of Cu for 2 min. The organic extract was decanted, the Cu(I)2 complex formed was extracted (x 2) into CHCl3 and Cu was continuously back-extracted into 0.2 M NH4+ - NH3 buffer (pH 10). The extract was injected into a carrier stream of water and Cu was determined by AAS at 324.8 nm. The detection limit was 0.39 ppm of I with a coefficient of variation (n = 9) of 1.6%. Results were comparable to those obtained by standard methods. Interference from Fe and Bi was eliminated by adding an excess of Cu; some thiophosphate pesticides interfered. The method was applied in the determination of malathion in an agricultural formulation.
Pesticides, dimethoxydithiophosphate Agricultural Spectrophotometry Sample preparation

"Investigation Of Turbomixers In Continuous-flow Analysis"
Talanta 1992 Volume 39, Issue 3 Pages 293-297
T. L. Spinks and G. E. Pacey*L. Fabian, S. Lee and B. P. Bubnis,

Abstract: Turbomixers were studied as replacements for mixing coils in flow injection methods for the determination of O3, ClO2-, ClO3-, Kjeldahl N, NO2- and phosphate. The limits of detection and coefficient of variation were generally comparable with or better than those obtained by standard flow injection analysis and sample throughput was 10% higher. The mixers removed the need for circular, serpentine or knotted coils. This paper describes an investigation of turbomixer as replacements for mixing coils in flow injection analysis (FIA). The turbomixer is a device that will efficiently mix three streams simultaneously. Although the traditional FIA gradient is not produced, the data shows that the reproducibility of a turbomixer-continuous-flow system is comparable to a standard FIA system.
Ozone Chlorite Chlorate ion Nitrogen, kjeldahl Nitrite Phosphate

"Bromine Number Determination By Coulometric Flow Injection Titration"
Talanta 1992 Volume 39, Issue 7 Pages 789-794
Richard H. Taylor, Camilla Winbo, Gary D. Christian* and Jaromir Rika*,

Abstract: The bromine number (unsaturation value) of petroleum distillates was determined by coulometric flow injection titrimetry with use of a single-line manifold system described previously (Ibid., 1992, 39, 285). The carrier stream (5.0 mL min-1) was acetic acid - methanol - aqueous 15% KBr (30:13:7) with addition of 1.8% methanolic HgCl2 as catalyst when needed. At a specified delay time flow was stopped and current was applied to generate Br as reagent in the cell chamber (0.90 ml). When the end-point had passed and sufficient unconsumed Br had formed for measurement, the current was cut off and flow was resumed to flush out the chamber. Unconsumed Br was detected by its absorbance at 470 nm. Results obtained for alkenes were nearer to theory value than those obtained by the ASTM Manual method. Sulfur compounds (e.g., ethanethiol) interfered but N-heterocyclic aromatics did not. In determination of 1-hexene (Br number theory 189.9, found 193), the coefficient of variation (n = 10) was 1.7%. The Br no., the number of g of Br which react with 100 g of a substance under given conditions, is a widely used parameter in the chemical and petroleum industries. A method of performing the Br number determination by coulometric flow injection titration, using both sequential injection with sinusoidal flow and single zone techniques, is described. Titrns. of olefins, known interfering compounds, and petroleum distillates were performed and compared with the results of conventional Br number titrns. Analyses yielded a relative standard deviation of 2%. Results compared favorably with those obtained by the conventional method for both pure (97%) olefins and petroleum distillates. The method is insensitive to interference from N compounds The CFIT technique combines the advantages of coulometric titrns.: controlled generation of reagent, avoidance of reagent standardization requirements and reagent storage and stability problems; with the advantages of FIA: small volume requirements which reduce cost and waste, controllable dilution through flow programming, toxic materials contained within a closed environment, and the capability of being automated.
Bromine Coulometry

"Simultaneous Determination Of Chloride, Bromide, Iodide And Fluoride With Flow Injection - Ion-selective Electrode Systems"
Talanta 1992 Volume 39, Issue 10 Pages 1259-1267
Fadhil M. Najib* and Shireen Othman,

Abstract: Electrodes for Cl-, Br- and I- were constructed (preparation described) from Ag2 - AgCl or AgBr (1:1) and Ag2S - AgI (1:3); for F- a commercial electrode was used. By combining the electrodes and suppressor columns of AgCl and amalgamated Pb, the ions were simultaneously determined in a carrier stream (0.5 mL min-1) of e.g. 0.1 M HClO4 at pH 4.0. The calibrati