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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Buffer

Classification: Reagent -> Buffer

Citations 484

"Continuous Monitoring Of Amino Acids And Related Compounds With Poly(3-methylthiophene)-coated Cylindrical Carbon Fiber Microelectrodes"
Anal. Chim. Acta 1999 Volume 401, Issue 1-2 Pages 145-154
L. Agüí, A. González-Cortés, P. Yáñez-Sedeño and J. M. Pingarrón

Abstract: The use of cylindrical carbon fiber microelectrodes (CFMEs) modified with poly(3-methylthiophene) (P3MT) films as amperometric microsensors for continuous monitoring of some amino acids such as tyrosine (Tyr), tryptophan (Trp), L-dopa, and related compounds such as tyramine and ascorbic acid, as well as small peptides such as Trp-Ala and Tyr-Gly, is discussed. Important practical advantages with respect to conventional glassy carbon (GC) electrodes, and also with respect to P3MT-coated GC electrodes of conventional size are demonstrated. The electrocatalytic ability of the modified surface allows the possibility of applying moderate potentials for the amperometric detection of the above mentioned compounds. Flow injection experiments carried out using a phosphate buffer solution of pH 7.0 as the carrier, and an applied potential of +0.8 V showed that no cleaning or regeneration pretreatment was needed when working with the same polymer modified electrode during the whole working day. The effect of the presence of acetonitrile or methanol in the flowing solution was evaluated. A flow injection method with amperometric detection was developed for the determination of L-dopa in pharmaceutical preparations. Finally, the modified microelectrodes have also shown suitable for amperometric detection in liquid chromatography (LC). A mobile phase composed of 5 : 95 (v/v) methanol : phosphate buffer solution of pH 7.0 allowed a good separation of mixtures of ascorbic acid, L-dopa, Tyr, tyramine and Trp, with detection limits of around 160 pmol. Furthermore, the-possibility of detection of Tyr-and Trp-containing oligopeptides Was also demonstrated.
Amino Acids l-Dopa Pharmaceutical Electrode Electrode

"Extraction Based On The Flow Injection Principle. 2. Determination Of Codeine As The Picrate Ion-pair In Acetylsalicylic Acid Tablets"
Anal. Chim. Acta 1979 Volume 104, Issue 1 Pages 21-28
Bo Karlberg, Per-Arne Johansson and Sidsel Thelander

Abstract: Codeine phosphate (I phosphate) [52-28-8] in aqueous samples was extd. as its picrate ion pair into CHCl3 in a continuous-flow system. The sample was introduced into an aqueous picrate stream buffered at pH 6.5; its dispersion gave controlled mixing before the aqueous stream was segmented by a CHCl3 stream. A specially constructed fitting is included to produce segments, typically 5-10 mm long, which passes into a Teflon coil (2 m long: inner diameter, 0.8 mm). At the outlet of the coil, the phases were separated and a fraction of the CHCl3 phase was passed through a spectrophotometric flow cell. The sample volume was 25-40 µ, the sampling rate ~60/h, and the relative standard deviation 1%.
Codeine Pharmaceutical Spectrophotometry Sample preparation

"Single-point Titration. 4. Determination Of Acids And Bases With Flow Injection Analysis"
Anal. Chim. Acta 1979 Volume 105, Issue 1 Pages 67-75
Ove Åström

Abstract: A single-point titrimetric system for acids and bases based on the flow injection principle is reported. The 30 µL sample is introduced into a water stream with a pneumatic injector; this stream is recorded potentiometrically with a glass electrode in a flow-through cell. The peak maxs. are a linear function of the acid or base concentration. in the range 0.01-0.1M. At a sampling rate of 180 samples/h, the relative deviation is <1%. The method can be used at sampling rates as high as 720 samples/h.
Acids Bases Potentiometry Electrode

"Flow Injection Extraction-spectrophotometric Determination Of Permanganate With The Ethylenebis(triphenylphosphonium) Cation"
Anal. Chim. Acta 1989 Volume 217, Issue 1 Pages 183-186
D. Thorburn Burns, N. Chimpalee, M. Harriott and G. M. Mckillen

Abstract: Buffer solution (citric acid - KH2PO4 - H3BO3 - diethylbarbituric acid - H2O; pH 6) was mixed with aqueous 10% NH4F before injection of the sample (250 µL). The solution was then mixed with aqueous 0.25% ethylenebis(triphenylphosphonium) bromide in a mixing coil (20 cm x 0.5 mm) before extraction with CHCl3. The mixture then passed to a phase separator and the absorbance of the organic phase was measured at 545 nm. The calibration graph was rectilinear for up to 25 µg mL-1 of Mn(VII), the detection limit was 0.58 µg mL-1 and the coefficient of variation (n = 10) was 1%. The method was applied in the determination of Mn in standard steel samples and results agreed well with certified values.
Permanganate Alloy Spectrophotometry Sample preparation

"Determination Of Trace Manganese In High-purity Titanium, Silicon And Mineral Acids By A Flow Injection Method Based On A Catalytic Reaction"
Anal. Chim. Acta 1989 Volume 217, Issue 1 Pages 23-30
Chongliang Zhang, Susumu Kawakubo and Tsutomu Fukasawa

Abstract: Sample solution (1 to 2 ml; 1.5 M in HF and 0.2 M in HCl) was subjected to ion-exchange extraction on a column of Amberlite CG-120 (H+ form, 100 to 200 mesh), with elution of the Mn with 6 M HCl. The eluate was evaporated almost to dryness, and the residue was dissolved in acetate buffer (pH 4.4). Portions (100 µL) were injected into the flow injection system where they were mixed with reagent solution [0.26 mM malachite green (C. I. Basic Green 4) - 0.01 M KIO4] before passing to a reaction coil at 50°C. The absorbance of the solution was measured at 615 nm. The calibration graph was rectilinear for up to 7 ng of Mn and the coefficient of variation (n = 5) at 3 ng of Mn was 2%. The method was successfully applied in the analysis of HF, HCl and HNO3 and of Ti metals and Si (sample prep. described).
Manganese Inorganic compound Inorganic compound Inorganic compound Metal Metal Spectrophotometry

"Specific Detection Of Nicotinamide Coenzymes By Liquid Chromatography And Amperometric Detection With Immobilized Glucose-6-phosphate Dehydrogenase"
Anal. Chim. Acta 1989 Volume 218, Issue 1 Pages 129-135
Toshio Yao, Yoshihiro Matsumoto and Tamotsu Wasa

Abstract: Glucose-6-phosphate dehydrogenase was immobilized (described) on LiChrosorb NH2 in a stainless-steel column (5 mm x 4 mm) and the reactor was incorporated into a flow injection system (illustrated) for determination of NAD+, NADH, NADP+ and NADPH. The sample was subjected to HPLC on a column (25 cm x 4.6 mm) of ODS-A material, with 0.02 M phosphate buffer (pH 7) as mobile phase (1 mL min-1), and the eluate was mixed with 0.2 M phosphate buffer (pH 8.5) containing 3 mM glucose 6-phosphate before passing to the enzyme reactor. The NADH and NADPH produced in the reactor were allowed to react with 0.1 M phosphate buffer (pH 8.5) containing phenazine methosulfate before amperometric detection at 0.0 V at a Pt electrode vs. Ag - AgCl. Calibration graphs were rectilinear from 0.05 to 20 nmol per 10 µL injection and detection limits were 3.2, 5.2, 7.9 and 9.4 pmol for NADP+, NADPH, NAD+ and NADH, respectively. The coefficient of variation (n = 5) were 1.2 to 3.0%.
Nicotinamide adenine dinucleotide oxidized Nicotinamide adenine dinucleotide phosphate oxidized Nicotinamide adenine dinucleotide phosphate reduced Nicotinamide adenine dinucleotide reduced LC Amperometry Electrode

"Flow Injection Determination Of Branched-chain L-amino-acids With Immobilized Leucine Dehydrogenase"
Anal. Chim. Acta 1989 Volume 218, Issue 1 Pages 161-166
Nobutoshi Kiba, Sachie Hori and Motohisa Furusawa

Abstract: Leucine dehydrogenase was immobilized on polystyrene Bio-Beads in a stainless-steel column (10 cm x 4 mm) and the column was incorporated into a flow system for determination of L-leucine, L-isoleucine and L-valine. A solution of 10 mM NAD+ in 1 mM Na4 EDTA was mixed with buffer solution (glycine - KCl - KOH of pH 11) before injection of the sample. The solution then passed to the enzyme reactor (thermostatted at 40°C) and the NADH produced was monitored fluorimetrically at 465 nm (excitation at 340 nm). The calibration graph was rectilinear from 5 µM to 0.5 mM isoleucine. The detection limit for L-leucine was 1 µM. The method was applied in the analysis of serum.
l-Leucine l-Isoleucine l-Valine Blood Serum Fluorescence

"Flow Injection Amperometric Determination Of Oxalate With Immobilized Oxalate Oxidase"
Anal. Chim. Acta 1989 Volume 218, Issue 1 Pages 1-6
Ala'ddin M. Almuaibed and Alan Townshend

Abstract: Oxalate oxidase (7.2 mg) was immobilized on 0.2 g of aminopropylsilanized controlled-pore glass as described by Masoom and Townshend (Anal. Chim. Acta, 1984, 166, 111) and the glass was packed into a column (2.5 cm x 2.5 mm) which was incorporated into a flow injection system for determination of oxalate. Sample solution (40 µL) was injected into the carrier stream (0.05 M Na succinate buffer of pH 3.5; 1 mL min-1) before passing, via a 15-cm mixing coil, to the enzyme-immobilized column where oxlate was oxidized to CO2 with the production of H2O2. The H2O2 was determined amperometrically at 0.6 V. Interference from Cu was masked by addition of Na2EDTA to the carrier stream or by incorporating a Chelex-100 column before the immobilized-enzyme column. The calibration graph was rectilinear from 6 µM to 0.9 mM oxalate and the detection limit was 5.7 µM. The coefficient of variation (n = 10) was 1% at 0.45 mM. Sample throughput was 40 h-1. The effects of ascorbic and uric acids were studied. Oxalate oxidase (7.2 mg) was immobilized on 0.2 g of aminopropylsilanized controlled-pore glass as described by Masoom and Townshend (Anal. Chim. Acta, 1984, 166, 111) and the glass was packed into a column (2.5 cm x 2.5 mm) which was incorporated into a flow injection system for determination of oxalate. Sample solution (40 µL) was injected into the carrier stream (0.05 M Na succinate buffer of pH 3.5; 1 mL min-1) before passing, via a 15-cm mixing coil, to the enzyme-immobilized column where oxlate was oxidized to CO2 with the production of H2O2. The H2O2 was determined amperometrically at 0.6 V. Interference from Cu was masked by addition of Na2EDTA to the carrier stream or by incorporating a Chelex-100 column before the immobilized-enzyme column. The calibration graph was rectilinear from 6 µM to 0.9 mM oxalate and the detection limit was 5.7 µM. The coefficient of variation (n = 10) was 1% at 0.45 mM. Sample throughput was 40 h-1. The effects of ascorbic and uric acids were studied.
Oxalate Amperometry

"Spectrophotometric Flow Injection Determination Of Urea In Body Fluids By Using An Immobilized Urease Reactor"
Anal. Chim. Acta 1989 Volume 218, Issue 1 Pages 151-155
Petr Solich, Miroslav Pol&aacute;ek and Rolf Karl&iacute;ek, Olga Valentov&aacute; and Miroslav Marek

Abstract: Urease was immobilized on poly(glycidyl methacrylate)-coated controlled-porosity glass which was then packed into PTFE tubing. The reactor was incorporated into a flow system for determination of urea. Serum was diluted 1:50 and urine 1:1000 or 1:2000 with water before injection into 0.2 M phosphate buffer (pH 6.9) containing 2 mM Na2 EDTA, 1 mM NaN3 and 5 µM-2-mercaptoethanol. The solution passed to the enzyme reactor before being mixed with 0.37 M Na salicylate - 4 mM Na nitroprusside - 0.25 M NaOH in aqueous 30% ethanol, and then with 30 mM NaClO and passing to a reaction coil (1.5 m x 0.5 mm) at 50°C. The absorbance of the solution was measured at 700 nm. The calibration graph was rectilinear for 25 to 500 µM-urea, and the coefficient of variation (n = 10) for 300 µM-urea was 1.1%.
Urea Blood Serum Urine Spectrophotometry

"Resolution Of Chemical Species In Flow Injection Analysis By Using Self-modeling Curve Resolution"
Anal. Chim. Acta 1989 Volume 218, Issue 2 Pages 303-311
Brice C. Erickson, Jaromir Ruzicka and Bruce R. Kowalski

Abstract: The application of chemometrics to improve resolution in flow injection analysis is described. The model systems analyzed contained phenolphthalein as analyte and methyl violet as interfering species. The sample and carrier solution contained 5% (v/v) of methanol to minimize adsorption, together with 5 mM acetic acid, -H3BO3 and -H3PO4; samples were adjusted to pH 6 and the carrier to pH 11 to provide a pH gradient as the sample dispersed in the carrier. The flow rate was 0.7 mL min-1, and the absorption spectrum from 328 to 600 nm at 4-nm intervals was acquired every 2 s by a photodiode-array detector. The data were processed by computer, and a self-modeling curve resolution algorithm was used to establish the spectra and the concentration. profiles of the two components. The method showed good predictive ability for 5 to 20 mg L-1 of phenolphthalein, with slighty larger errors at the higher concentration.
Phenolphthalein Spectrophotometry

"Automated Micro Stopped-flow - Continuous-flow Apparatus For Serial Measurement Of Enzyme Reactions And Its Application As A Real-time Analyser For Column Chromatography"
Anal. Chim. Acta 1989 Volume 220, Issue 1 Pages 13-21
Kojiro Takahashi and Shigehiko Taniguchi, Tadafumi Kuroishi and Kazuo Yasuda, Takayuki Sano

Abstract: In the described personal computer-controlled system, the volume required per measurement of a time course in an enzyme reaction is as low as 30 µL for each enzyme and assay solution; the time course can be traced by sampling 10 observation points in 1 s; and the serial measurement of such a time course can be performed with automated cyclic operation. Protein concentration, pH and conductivity can also be monitored simultaneously in the enzyme solution with use of appropriate detectors. The four-channel apparatus was applied to the monitoring of the reaction between calf bone alkaline phosphatase and p-nitrophenylphosphate in the Tris buffer, and to the purification of bone alkaline phosphatase by ion-exchange (Q-Sepharose) and affinity-column (Zn2+-agarose) chromatography.
Enzymes Conductometry

"Quantitation Of Sodium Hydrogen Sulfite In Parenteral Samples By A Flow Injection Method"
Anal. Chim. Acta 1989 Volume 220, Issue 1 Pages 281-285
Dennis R. Jenke

Abstract: Sodium hydrogen sulfite in pharmaceutical formulations (1 µL) was injected into a stream of 0.03% 3,3'-dithiobis-(6-nitrobenzoic acid) solution in 44 mM citric acid buffer of pH 6.0 (1 mL min-1) and, after passage through a 2.5 mL reaction coil, the absorbance was measured at 410 nm. The processing time was 4 min per injection. The calibration graph was rectilinear from 1 ng (practical detection limit) to 1 µg of NaHSO3 injected, and coefficient of variation were 1.5% at 10 mg L-1 and ~7% at 3 mg l-1. Matrix components did not interfere.
Hydrogen sulfite Pharmaceutical Spectrophotometry

"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

"Flow Injection Determination Of Malate With Immobilized Malate Dehydrogenase"
Anal. Chim. Acta 1989 Volume 221, Issue 2 Pages 337-340
Ala'ddin M. Almuaibed and Alan Townshend

Abstract: Malate dehydrogenase was immobilized on controlled-pore glass and packed in a glass column (2.5 cm x 2.5 mm); the column was used in a flow injection system. The carrier stream (2 mL min-1) consisted of 0.1 M phosphate buffer (pH 11.5) - 3.6 mM NAD+ (1:1); detection was at 340 nm. The detection limit was 7 µM and calibration graphs were rectilinear for 0.9 mM malate. The coefficient of variation (n = 10) was 1.5% for 0.44 mM. The column was stable for 1 month without loss in activity. The sampling rate was 50 h-1. Malate dehydrogenase was immobilized on controlled-pore glass and packed in a glass column (2.5 cm x 2.5 mm); the column was used in a flow injection system. The carrier stream (2 mL min-1) consisted of 0.1 M phosphate buffer (pH 11.5) - 3.6 mM NAD+ (1:1); detection was at 340 nm. The detection limit was 7 µM and calibration graphs were rectilinear for 0.9 mM malate. The coefficient of variation (n = 10) was 1.5% for 0.44 mM. The column was stable for 1 month without loss in activity. The sampling rate was 50 h-1.
l-Malate

"Flow-through PH-ISFET Detector For Flow Injection Analysis"
Anal. Chim. Acta 1989 Volume 222, Issue 2 Pages 373-377
S. Alegret, J. Alonso, J. Bartroli and J. Domenech, N. Jaffrezic-Renault and Y. Duvault-Herrera

Abstract: The alumina-chip (1.5 mm x 1.5 mm) pH ISFET described by Van den Vlekkert et al. (Sens. Actuators, 1988, 14, 165), having rear-side contacts into which leads can be inserted and bonded by conductive epoxy-resin, is suitable for incorporation in a flow cell (diagrams presented). The detector shows a sensitivity of 53 mV per pH unit, with a drift of 0.2 mV h-1. Detector responses to 25 µL injections of buffer solution of pH 4.3, 9.0 and 12.0 into a carrier stream (3.5 mL min-1) buffered at pH 7.0 are illustrated.
Field effect transistor

"Flow Injection Determination Of L-tyrosine In Serum With An Immobilized Tyrosinase Reactor And Fluorescence Detection"
Anal. Chim. Acta 1989 Volume 224, Issue 1 Pages 133-138
Nobutoshi Kiba, Masae Ogi and Motohisa Furusawa

Abstract: Serum (100 µL) was deproteinized with Na2WO4 - H2SO4 and filtered, and 50 µL of the filtrate was injected into a carrier stream of 0.3 M phosphate buffer of pH 7.2 (0.6 mL min-1), which passed through a separation column (5 cm x 4 mm) of Capcell 120 C18 (5 µm) and a reactor column (5 cm x 4 mm) containing the cited enzyme immobilized on controlled-pore glass beads and was then mixed with a stream of 5 M KOH (1 mL min-1). The fluorescence was measured at 490 nm (excitation at 375 nm). The calibration graph was rectilinear in the range 0.1 µM to 0.1 mM tyrosine, the detection limit was 50 nM, and the coefficient of variation (n = 10) for the determination of 5.0 µM-tyrosine was 2.0%.
Tyrosine Blood Serum Fluorescence

"Use Of Diode-array Detectors For The Simultaneous Spectrophotometric Determination Of Calcium And Magnesium By Flow Injection"
Anal. Chim. Acta 1989 Volume 224, Issue 1 Pages 23-30
M. Blanco, J. Coello, J. Gen&eacute;, H. Iturriaga and S. Maspoch

Abstract: The sample solution and reagent (0.2 mM arsenazo III) are injected simultaneously into separate carrier streams (1.05 mL min-1) of Tris - HCl buffer solution (pH 8.5) that merge to form a colored zone for diode-array detection. Although arsenazo III absorbs strongly and its spectrum overlaps those of the complexes, separate concentration. values for Ca and Mg can be obtained by the method described (based on either normal or first-derivative absorption spectra) in which the unconsumed arsenazo III is considered as a component of the mixture. The method is applicable to 0.1 to 1 µg mL-1 of Mg and 0.2 to 1.5 µg mL-1 of calcium. The analysis rate is 50 samples h-1. The sample solution and reagent (0.2 mM arsenazo III) are injected simultaneously into separate carrier streams (1.05 mL min-1) of Tris - HCl buffer solution (pH 8.5) that merge to form a colored zone for diode-array detection. Although arsenazo III absorbs strongly and its spectrum overlaps those of the complexes, separate concentration. values for Ca and Mg can be obtained by the method described (based on either normal or first-derivative absorption spectra) in which the unconsumed arsenazo III is considered as a component of the mixture. The method is applicable to 0.1 to 1 µg mL-1 of Mg and 0.2 to 1.5 µg mL-1 of calcium. The analysis rate is 50 samples h-1.
Calcium Magnesium Spectrophotometry

"Utilization Of Kinetic-based Flow Injection Methods For The Determination Of Chlorine And Oxychlorine Species"
Anal. Chim. Acta 1989 Volume 224, Issue 2 Pages 383-391
G. Gordon, K. Yoshino, D. G. Themelis, D. Wood and G. E. Pacey

Abstract: The flow injection system was a Tecator 5020 analyzer. with a Tecator Chemifold II, and the detector was a Tecator 5024 FIAstar photometer with a 5024-011 optical unit and a 5032 controller. Samples were injected into water as carrier stream and mixed in a coil with 0.02 M or 12 M HCl, then this solution was mixed with 0.3 M KI reagent. The absorbance of the resulting I3- was measured at 370 nm in a 1-cm flow cell (volume 18 µL). With use of 0.02 M HCl, the signal is due to ClO2-, and with use of 12 M HCl it corresponds to ClO2- plus ClO3-, for solution free from ClO2 and/or Cl. By analysis at pH 8.3, ClO2 and free Cl can be determined without interference from the anions; oxalic acid can be used to mask Cl in the determination of ClO2 at pH 8.3. Conditions are given for determining each species without interference; calibration ranges were 0.2 to 10, 0.3 to 10, 0.08 to 5 and 0.08 to 5 mg L-1 for Cl, ClO2, ClO2- and ClO3-, respectively. The method is intended for application to drinking water.
Chlorine Chlorite Chlorate ion Chlorine dioxide Water 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

"Flow Injection And Liquid Chromatographic Determination Of Aluminum Based On Its Fluorimetric Reaction With 8-hydroxyquinoline-5-sulfonic Acid In A Micellar Medium"
Anal. Chim. Acta 1989 Volume 225, Issue 2 Pages 339-350
Jos&eacute; Ignacio Garci&aacute; Alonso, Angeles L&oacute;pez Garci&aacute;, Alfredo Sanzmedel and Elisa Blanco Gonzales, Les Ebdon and Phil Jones

Abstract: Reaction of Al with 8-hydroxyquinoline-5-sulfonic acid (I) in cationic micelles of hexadecyltrimethylammonium bromide (II) formed a strongly fluorescent compound and allowed continuous determination of Al in flowing systems. At pH 6.3, with 0.2 mM I and 2 mM II, the detection limit for Al by flow injection analysis was 0.1 ng mL-1. The calibration graph was rectilinear for 100 ng mL-1, and the peak-height precision was 2% for 10 ng mL-1. Interference was greatly decreased compared with the batch method. The reaction was applied to the post-column detection of Al in fresh and high-salinity waters and dialysis fluid by ion chromatography, and for speciation of Al in serum after separation of proteins by ion-exchange LC.
Aluminum Dialysis Fluid Environmental Blood Serum Sea Fluorescence

"Direct Spectrophotometric Determination Of Total Boron In Soils With Ultrasonic Leaching In Automatic Flow Systems"
Anal. Chim. Acta 1989 Volume 222, Issue 2 Pages 221-227
Danhua Chen, F. L&aacute;zaro, M. D. Luque De Castro and M. Valc&aacute;rel

Abstract: Sample (5 to 10 mg) was leached for 0.5 min in 0.1 M HCl at 80°C with ultrasonic agitation. The solution was injected into a flow of 0.1 M HCl (0.36 mL min-1) which merged with previously mixed aqueous azomethine-H (7.5 mg mL-1) and EDTA - H3PO4 - aqueous NH3 buffer solution (pH 7.35) each flowing at 0.18 mL min-1. The mixture passed through a reaction coil (440 cm x 0.7 mm) and the absorbance was measured at 416 nm. The calibration graph was rectilinear for 0.2 to 2.5 µg mL-1, and the mid-range coefficient of variation (n = 5) was 2.6%. The sampling rate was 25 h-1.
Boron Environmental Sample preparation Spectrophotometry

"Continuous-flow Bioluminescent Assay Of NADH Using A Fibre-optical Sensor"
Anal. Chim. Acta 1989 Volume 222, Issue 2 Pages 331-336
L. J. Blum, S. M. Gautier and P. R. Coulet

Abstract: The sensor comprises bacterial luciferase - oxidoreductase co-immobilized on pre-activated nylon membranes and placed in close contact with the tip of a glass optical fiber bundle. A light-tight flow cell was adapted to fit the end of the bundle. Sample solution were prepared in 0.1 M phosphate buffer (pH 7.8), and the reagent solution comprised 50 mM phosphate buffer (pH 7) containing 2 mM dithiothreitol, 0.2% of bovine serum albumin, 30 µM-FMN and 9.5 µM-decanal. The calibration graph was rectilinear from 2 pmol (the detection limit) to 1 nmol of NADH, and the coefficient of variation was 3.4% for 0.1 nmol. The sampling rate was 25 h-1. No loss in activity was observed after 150 determinations over 3 days.
Nicotinamide adenine dinucleotide reduced Blood Serum Sensor

"Continuous-flow Bioluminescent Assay Of NADH Using A Fibre-optical Sensor"
Anal. Chim. Acta 1989 Volume 222, Issue 2 Pages 331-336
L. J. Blum, S. M. Gautier and P. R. Coulet

Abstract: The sensor comprises bacterial luciferase - oxidoreductase co-immobilized on pre-activated nylon membranes and placed in close contact with the tip of a glass optical fiber bundle. A light-tight flow cell was adapted to fit the end of the bundle. Sample solution were prepared in 0.1 M phosphate buffer (pH 7.8), and the reagent solution comprised 50 mM phosphate buffer (pH 7) containing 2 mM dithiothreitol, 0.2% of bovine serum albumin, 30 µM-FMN and 9.5 µM-decanal. The calibration graph was rectilinear from 2 pmol (the detection limit) to 1 nmol of NADH, and the coefficient of variation was 3.4% for 0.1 nmol. The sampling rate was 25 h-1. No loss in activity was observed after 150 determinations over 3 days.
Nicotinamide adenine dinucleotide reduced Blood Serum Sensor

"Flow Injection Immunoassays With Acridinium Ester-based Chemiluminescence Detection"
Anal. Chim. Acta 1989 Volume 227, Issue 1 Pages 97-107
C. Shellum and G. G&uuml;bitz

Abstract: The cited method was demonstrated by determination of mouse IgG. Anti-mouse IgG was labelled with acridinium N-hydroxysuccinimide ester and immobilized on a column of Trisacryl GF-2000. Samples (20 µL) of IgG, labelled IgG and a mixture of H2O2 and NaOH solution were consecutively injected into a buffered carrier stream to the column and the emitted light was measured with a Kratos fluorimeter. The response was rectilinear up to 20 fmol with a limit of detection of 0.2 fmol. The coefficient of variation (n = 10) were 4.3%.
Immunoglobulin G Immunoassay Chemiluminescence

"Radiometric And Fluorimetric Determination Of Aminosilanes And Protein Covalently Bound To Thermally Pre-treated Glass Substrates"
Anal. Chim. Acta 1990 Volume 228, Issue 1 Pages 107-116
Laurie Locascio-Brown, Anne L. Plant and Richard A. Durst, Marius V. Brizgys

Abstract: Derivatization of soda-lime glass spheres with aminosilanes and the stability of these groups at near-physiological pH in flow streams of aqueous buffered solution were studied. The extent of silanization was determined by a radioactive tracer method and a method based on a fluorescent marker, which confirmed the presence of immobilized and adsorbed amines in the nmol range. A method for covalently attaching bovine serum albumin to the beads via a cross-linking reagent which reacts selectively with amines is described. Thermal pre-treatment of the glass before derivatization enhanced suface derivatization with aminosilanes. Less than monolayer films prepared with monofunctional silanes were stable, after initial conditioning, with a 3% loss over 24 h in constantly flowing solution at pH 8, allowing the design of reusable immunoassay systems which were readily calibrated.
Protein Aminosilanes Immunoassay Radiochemical Fluorescence

"Mixed Ferrocene - Glucose Oxidase - Carbon-paste Electrode For Amperometric Determination Of Glucose"
Anal. Chim. Acta 1990 Volume 228, Issue 2 Pages 251-257
Joseph Wang, Li-Huey Wu, Ziling Lu, Ruiliang Li and Juanita Sanchez

Abstract: The incorporation (by hand-mixing for >30 min) within a carbon-paste matrix (435 mg) of both the enzyme (50 mg) and a ferrocene derivative (15 mg) provided an effective electrode, which was used in a supporting electrolyte of 0.05 M phosphate buffer of pH 6.5. The best sensitivity was obtained with 1,1'-dimethylferrocene, with rectilinear response from 0.5 to 6.0 mM glucose and a slope of 7.4 nA l mmol-1. In a flow injection system (0.75 mL min-1) the coefficient of variation (n = 12) at 10 mM was 3.1%. The presence of ascorbic acid (I), dopamine and uric acid inhibited the response, but incorporation of stearic acid into the paste greatly reduced the interference by I.
Glucose Electrode Amperometry

"Determination Of Parathion In The Presence Of Paraoxon And 4-nitrophenol By Flow Injection Analysis With Amperometric Detection"
Anal. Chim. Acta 1990 Volume 228, Issue 2 Pages 317-321
J. Hern&aacute;ndez Mendez, R. Carabias Mart&iacute;nez, E. Rodriguez Gonzalo and J. Perez Trancon

Abstract: The method was based on determination of the 4-nitrophenol produced by the hydrolysis of parathion (I), which was optimally effected offline with 11.9 µM-Pd in 0.1 M acetic acid in aqueous 20% methanol for 15 min or with 29.6 µM-Hg in 0.06 M acetic acid - 0.04 M Na acetate buffer in aqueous 40% methanol for 150 min. After hydrolysis, the mixture (0.157 ml) was injected into a carrier stream of 18 mM HClO4 - 0.1 M acetic acid in aqueous 20% methanol (2.14 mL min-1) or of acetate buffer solution in aqueous 40% methanol (1.47 mL min-1), respectively, and the response at a vitreous-carbon electrode at 1.2 V vs. Ag - AgCl was measured. The response in the presence of Pd or Hg was rectilinear for 0.24 to 6.0 µM- or 0.20 to 7.1 µM-I, respectively, and the respective detection limits and coefficient of variation were 49 nM and 34 nM and 2.2% (1.19 µM-I) and 2.3% (2.38 µM-I). In the presence of 4-nitrophenol the sample was analyzed both before and after hydrolysis and I was determined by difference.
Parathion Amperometry Electrode

"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

"Flow Injection Determination Of Mixtures Of Amines Immobilized In The Flow Cell Of A Photometric Diode-array Detector"
Anal. Chim. Acta 1990 Volume 229, Issue 1 Pages 177-182
Beatriz Fernandez-Band, Fernando L&aacute;zaro, M. D. Luque de Castro and Miguel Valcarcel

Abstract: Mixtures of 2,4-dinitrophenylhydrazine (I) and 2- and 4-nitrophenylhydrazine in 0.1 M phosphate buffer (pH 6.5) containing 5% of methanol were injected into the manifold of a single-channel flow system and passed, in a carrier stream (1.1 mL min-1) of 0.1 M phosphate buffer (pH 6.5) - methanol (3:2), through the detector flow cell packed with C18 bonded silica. The amines were concentrated, retained and determined in situ. Spectra were recorded from 300 to 500 nm, and three wavelengths per analyte were selected for calibration and separation of the mixtures. The retained compounds were rapidly eluted by the carrier, allowing a sampling frequency of 40 h-1. Calibration graphs were rectilinear from 0.5 (determination limit) to 10 µM for each amine, and the coefficient of variation (n = 11) at 20 µM-I was 1.4%.
Amines

"Amperometry Of Thiols In A Flow Injection System With A Nickel Oxide Electrode"
Anal. Chim. Acta 1990 Volume 229, Issue 1 Pages 191-195
Yoshiko Arikawa and Calvin O. Huber

Abstract: The electrochemical oxidation of a series of thiols on a nickel oxide electrode surface was investigated in a flow injection system. The thiols were dissolved in phthalate buffer (pH 3.0), the injection volume was 25 µL, 0.1 M NaOH containing 0.05 mM NiSO4 was used as background electrolyte (1.0 mL min-1), and Pt auxiliary and SCE reference electrodes were sited downstream of the working electrode. The optimum applied potential was 0.46 V. Graphs of peak current vs. concentration. were rectilinear from 0.1 to 1 mM, and detection limits ranged from 0.03 to 0.2 mM. The coefficient of variation (n = 10) for 0.1 mM ethanethiol was 1.6%.
Thiols Amperometry Electrode

"Simultaneous Flow Injection Determination Of Aluminum And Zinc Using LED Photometric Detection"
Anal. Chim. Acta 1990 Volume 230, Issue 1 Pages 125-130
Marek Trojanowicz and Joanna Szpunar-obiska

Abstract: The sample solution was injected into a carrier stream of 0.4 M acetate buffer (pH 4.5) that was then blended with aqueous 0.05% xylenol orange and passed through a reaction coil before detection in a 1.5-cm path-length flow cell by sequential operation of light-emitting diodes with emission max. at 563, 580 and 638 nm under computer control so that separate peak heights for the two analytes could be obtained by multiple linear regression with matrix inversion. Rectilinear calibration graphs were obtained for 0.2 to 25 µg mL-1 of Al and 0.2 to 30 µg mL-1 of Zn, and each could be determined in the presence of a 100-fold concentration. of the other. Several metals and anions interfered; interference from Fe(III) was minimized by reduction with ascorbic acid and masking with EDTA. The method was applied to alloys.
Aluminum Zinc Alloy Spectrophotometry

"Flow-through PH-ISFET As Detector In The Determination Of Ammonia"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 53-58
S. Alegret, J. Alonso, J. Bartroli and M. del Valle, N. Jaffrezic-Renault and Y. Duvault-Herrera

Abstract: The alumina pH-ISFET with rear-side contacts described by Van den Vlekkert et al. (Sens. Actuators, 1988, 14, 165) was incorporated in a gas-dialysis flow injection system, which is illustrated schematically. Ammonium ions are converted into NH3, which diffuses through a microporous hydrophobic membrane (Millipore GVHP 0950) into a stream of 2 mM NH4Cl (I adjusted to 4 mM with K2SO4) to form a buffer solution, the pH of which is monitored by the ISFET. The range of rectilinear response was 0.1 to 10 mM, the detection limit was 0.05 mM, and the within-day coefficient of variation (n = 12) at 0.7 mM NH4Cl was 1.03%. The system was applied to river water.
Ammonia River Field effect transistor Electrode Electrode

"Flow Injection Analysis For L-glutamate Using Immobilized L-glutamate Oxidase: Comparison Of An Enzyme Reactor And Enzyme Electrode"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 121-124
Toshio Yao, Naokazu Kobayashi and Tamotsu Wasa

Abstract: The enzyme was covalently immobilized by the use of aminopropyl-controlled-pore glass and glutaraldehyde, and by cross-linking the enzyme and bovine serum albumin with glutaraldehyde on one side of a Pt sheet silanized with 3-aminopropyltriethoxysilane. The former was used in a packed-bed reactor and the latter as a flow-through enzyme electrode in a flow injection system. Both systems were compared in the determination of L-glutamate (I), the H2O2 evolved being monitored amperometrically. The carrier solution was 0.1 M phosphate buffer (pH 7.5) pumped at 1.5 mL min-1. The speed of analysis was 60 samples h-1 with the enzyme electrode compared with 90 to 120 samples h-1 with the enzyme reactor. The detection limits were 2 and 4 µM for the reactor and electrode, respectively. For both systems the peak current was rectilinearly related to the I concentration. from 5 µM to 1 mM. The selectivity and stability of both systems were similar. The methods were applied to the determination of I in Japanese seasonings; the coefficient of variation was 0.7% (n = 12).
l-Glutamate Amperometry Electrode

"Flow Injection Spectrofluorimetric Determination Of Paracetamol"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 259-264
J. Martinez Calatayud, C. Gomez Benito

Abstract: Duolite A102 D anion-exchange resin (Probus) was saturated with K3Fe(CN)6 solution and slowly stirred for 30 min. The resin was separated and washed with water until a colorless filtrate was obtained. Oxidative mini-columns, prepared by introducing the resin into PTFE coils, were incorporated into the flow injection assembly (diagram given). Powdered tablets containing paracetamol (I; 0.04 to 17.6 mg l-1) were dissolved in water and the solution was applied to the mini-columns followed by direct injection into a stream of Na2CO3 - H3BO3 - KCl buffer (pH 9.94) which then merged with a stream of N,N'-dimethylformamide in an inert single-bead string reactor. Fluoresence detection was at 427 nm (excitation at 331 nm). The calibration graph was rectilinear from 0.04 to 100 mg L-1 of I and the coefficient of variation was 1.4%. Tolerance levels for foreign species are tabulated and the determination of I in several pharmaceutical formulations is discussed.
Acetaminophen Pharmaceutical Ion exchange Fluorescence

"Off-line And Online Assay Of Membrane Protein With O-phthaldialdehyde By Flow Injection With Post-column Reaction"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 249-257
Samuel M. Mozersky

Abstract: Sample (325 µL) was injected into an off-line flow injection analysis system (details and diagram given) with 300 mM sucrose - 1 mM 2-mercaptoethanol (I) - 1 mM dithiothreitol - 3 mM HEPES buffer (pH ~7.4) as sample carrier solution (0.5 mL min-1) and 2% sodium dodecyl sulfate - 11.9 mM o-phthalaldehyde - 57 mM I - 4% methanol - 100 mM tetraborate buffer (pH ~10.8) as reagent solution (0.5 mL min-1). Adequate flushing was ensured by using a load volume of 1 mL to fill the injection loop. Detection was at 340 nm. A rectilinear relationship between peak height and protein concentration. was observed for 0 to 1000 mg L-1 of bovine serum albumin and 0 to 140 mg L-1 of mitochondrial protein. The off-line system was modified for online monitoring of the effluent from a field flow fractionator (the same basic design could be applied to any separation device yielding an effluent stream, e.g., a chromatographic column). The online apparatus was applied in the determination of the distribution of membrane protein in the channel effluent after fractionation of sub-cellular particle preparations containing corn root mitochondria and microsomes.
Albumin Cow Serum Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Acetyl-coenzyme A With Immobilized Phosphotransacetylase"
Anal. Chim. Acta 1990 Volume 232, Issue 1 Pages 281-286
Susumu Yamato and Kenji Shimada

Abstract: A method is given for immobilizing phosphotransacetylase on AF-Tresyl TOYOPEARL 650 gel. The treated gel, suspended in 0.1 M phosphate buffer, (pH 8) containing 1 mM NaN3, was packed in stainless-steel columns (1 cm x 4 mm), which were stored at 4°C. The carrier stream for flow injection analysis contained 30 mM Na2HPO4, 15 mM (NH4)2SO4 and Ellman reagent in 0.1 M borate buffer of pH 7.5 (1 mL min-1). Samples (25 µL) were injected into the carrier stream, which then passed through the gel column at 40°C In the reaction, acetyl coenzyme A was converted into acetyl phosphate and the free mercapto-compound reacted with Ellman reagent; the yellow color was detected at 412 nm. Calibration graphs were rectilinear from 4 µM to 0.4 mM, with a detection limit of 0.8 µM. At 0.2 mM, the coefficient of variation (n = 27) was 1.7%. The column was stable for 2 months, comprising ~1000 analyzes.
Acetyl-CoA Spectrophotometry

"Separation Of Rhenium By Extraction With Crown Ethers And Flow Injection Extraction-spectrophotometric Determination With Brilliant Green"
Anal. Chim. Acta 1990 Volume 232, Issue 1 Pages 287-292
Hideko Koshima and Hiroshi Onishi

Abstract: Rhenium solution (20 µg) were prepared in 2 M KOH - 10 mM K Na tartrate (10 to 30 ml), and the Re(VII) was extracted into a 10 mM dicyclohexano-18-crown-6 in 1,2-dichloroethane (5 ml, then 2 ml). The combined extracts were diluted with hexane, and the Re(VII) was back-extracted into 0.2 M phosphate buffer of pH 6.0 (6 ml, then 3 ml). The Re in the buffer was determined by flow injection, with 4 reagent lines, viz, buffer (0.4 mL min-1), water (0.4 mL min-1), ethanolic 0.15% C. I. Basic Green 1 and benzene (0.2 mL min-1). The absorbance of the benzene extract of the complex was measured at 640 nm. The calibration graph was rectilinear for up to 1.5 mg L-1 of Re(VII) in aqueous solution There was serious interference by NO3- and ClO4-; the former could be prevented by decomposition with formic acid. Large amounts of Mo(VI) did not interfere, so the method could be applied directly to, e.g., molybdenite.
Rhenium Spectrophotometry Sample preparation

"Phosphorescence Detection In Flowing Systems: Selective Determination Of Aluminum By Flow Injection Liquid Room-temperature Phosphorimetry"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 233-238
Yi-Ming Liu, M. R. Fernandez de la Campa, M. E. Diaz Garcia and A. Sanz-Medel

Abstract: Aluminum was determined by micelle-stabilized phosphorimetry. A three-line flow injection manifold was used, involving 1 M acetate buffer (pH 5.5) containing Na2SO3 as carrier stream, 5 mM ferron in the buffer as chelating agent, and 0.2 M hexadecyltrimethylammonium bromide in the buffer as stabilizer. Phosphorescence was measured at 596 nm (excitation at 400 nm). The calibration graph was rectilinear for 4 µg mL-1. The coefficient of variation were 2.7% for 1 µg mL-1 (n = 10). The method was reasonably selective; >20 common species did not interfere or could be masked. The method was applied without sample pre-treatment to tap-water and dialysis fluid.
Aluminum Water Dialysis Fluid Phosphorescence

"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

"Multi-function Fibre-optic Sensor For The Bioluminescent Flow Determination Of ATP Or NADH"
Anal. Chim. Acta 1990 Volume 235, Issue 2 Pages 243-253
Sabine M. Gautier, Lo&ouml;ic J. Blum and Pierre R. Coulet

Abstract: Photinus-luciferin 4-monooxygenase (ATP hydrolysing) was co-immobilized with alkanal monooxygenase (FMN-linked) and NAD(P)H dehydrogenase (FMN) from Vibrio harveyi on a pre-activated polyamide membrane. The membranes was applied in the determination of ATP and NADH in a flow injection system (details described) with 0.05 M Tris buffer of pH 7.75 containing 4 mM DDT, 0.2% bovine serum albumin (BSA), 30 mM Mg acetate and 0.2 mM luciferin for determination of ATP and 0.05 M phosphate buffer (pH 7.0) containing 2 mM DDT, 0.2% BSA, 9.5 µM-decyl aldehyde and 30 µM-FMN for determination of NADH. Light emitted at the enzymatic membrane was transmitted from the light-tight flow cell through a glass-fiber bundle (1 m x 8 mm) to the photomultiplier tube of a luminometer. Calibration graphs were rectilinear from 0.25 pmol to 3 nmol of ATP and 5 pmol to 1 nmol of NADH, with coefficient of variation of 4.0 and 4.5%, respectively, when using continuous-flow measurement.
Sensor Bioluminescence

"Enzymatic Determination Of L-lysine By Flow Injection Techniques"
Anal. Chim. Acta 1990 Volume 235, Issue 1-3 Pages 329-335
Andreas Pohlmann and Wolfgang W. Stamm, Hitoshi Kusakabe, Maria-Regina Kula

Abstract: Samples (2 µL) were injected into a carrier stream (~0.8 mL min-1) of 0.2 M phosphate buffer (pH 7.4) and mixed with a reagent stream containing phenol and 4-aminoantipyrine. The mixture was passed through an enzyme reactor. The enzyme reactor consisted of a perspex cartridge (4 cm x 3 mm) filled with 100 mg of VA-Epoxy Biosynth resin on which L-lysine oxidase and horse-radish peroxidase were co-immobilized. The color development in the stream was monitored at 500 nm. Response was rectilinear for up to 16 mM L-lysine with an injection volume of 2 µL; the detection limit was 1 mM but could be improved to 0.05 mM by increasing the injection volume to 36 µL. Analysis time was 30 samples h-1. The technique could also be used with both enzymes in solution or with L-lysine oxidase immobilized and horse-radish peroxidase in solution
l-Lysine

"Flow Injection Catalytic Kinetic Determination Of Manganese Using Stopped-flow And Gradient Calibration"
Anal. Chim. Acta 1990 Volume 235, Issue 1 Pages 323-327
Jiannan Yang, Chenglong Ma and Shuliang Zhang, Zhao Shen

Abstract: Sample solution was injected in to a carrier stream of borax - NaOH buffer (pH 9.5), mixed with two reagent streams of aqueous 0.5 M H2O2 and 0.1 M Tiron - 20 mM 1,10-phenanthroline, respectively, and the absorbance was monitored at 440 nm. Calibration was effected by the stopped-flow technique and only one standard was required. The calibration graph was rectilinear for up to 640 nM-Mn(II) and no interference was observed from Zn(II), Co(II), Ni(II), Fe(III), Cd(II) and Cu(II). The method was applied in the determination of Mn2+ in resevoir water; results agreed well with those by an alternative catalytic method. Throughput was 40 samples h-1.
Manganese

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

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

"Determination Of Cobalt(II), Copper(II) And Iron(II) By Ion Chromatography With Chemiluminescence Detection"
Anal. Chim. Acta 1990 Volume 236, Issue 2 Pages 287-292
Bolei Yan and Paul J. Worsfold

Abstract: Optimum conditions for the separate flow injection determination of Cu(II), Co(II), Fe(II) and Cr(III) comprised water as carrier stream, a reagent of 50 µM-luminol and 5 mM H2O2 in 0.1 M carbonate buffer of pH 11.7, and a flow rate of 1.5 mL min-1 per channel. Separation of the metals was achieved by ion chromatography on a column (25 cm x 4.6 mm) of Partisil 10 SCX, with an aqueous solution of a carboxylic acid as mobile phase (1.5 mL min-1). Complex formation between the carboxylic acid and the metal suppressed the chemiluminescence in the subsequent luminol - H2O2 reaction; however, oxalic acid (5 mM) caused only a 14% suppressive effect for 100 ng mL-1 of Cu(II) and gave good separation of Cu(II), Co(II) and Fe(II); 5 mM oxalic acid at pH 4.2 was thus used as mobile phase. Detection limits by ion chromatography were 0.01 and 5 ng mL-1 for Co and Cu, respectively; those by flow injection analysis were 0.6 pg mL-1 for Co, 80 pg mL-1 for Cu, 0.3 ng mL-1 for Fe(II) and 0.1 ng mL-1 for Cr(III).
Cobalt(II) Copper(II) Iron(2+) Chemiluminescence

"Determination Of Chromium By Online Preconcentration On A Poly (hydroxamic Acid) Resin An Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1990 Volume 236, Issue 2 Pages 469-473
Ajay Shah and Surekha Devi

Abstract: Seven poly(hydroxamic acid) resins [Analyst (London), 1985, 110, 501] were evaluated for LC separation of Cr(III) from U(VI) and from multi-component mixtures. Columns (17 cm x 5 mm) containing the resins in H+ form were used, and the flow rate for sorption and elution was 1 mL min-1. At pH 5, U(VI), Fe(III), Zn and Cu(II) were retained on the resin, but ~80% of the Cr(III) passed through. Retained U(VI) was eluted by 1 M HCl, Zn and Cu(II) by 0.1 M HCl and Fe(III) by 3 M HCl. Cross-contamination was observed between Zn and Cu. Tervalent Cr could also be determined by flow injection flame AAS with use of a column (4 cm x 2.5 mm) of poly(hydroxamic acid) resin and a carrier stream of 0.2 M acetate buffer (pH 2) for pre-concentration.; the Cr(III) was then eluted with 1 M HCl for AAS at 357.9 nm. The calibration graph was rectilinear for 10 µL portions of solution containing 20 to 100 ng mL-1 of Cr(III). The flow injection method was used to determine Cr(III) in seawater at pM concentration.
Chromium Sea Spectrophotometry

"Electrochemical Determination Of Allopurinol Based On Its Interaction With Xanthine Oxidase"
Anal. Chim. Acta 1990 Volume 237, Issue 1 Pages 91-98
Glenn B. Martin and Garry A. Rechnitz

Abstract: Allopurinol (I) can be determined either from its inhibition of xanthine oxidase (II) activity or directly as a substrate for II. In a homogeneous inhibition assay, a 0.01 M Tris - HCl buffer of pH 8.0 containing 0.05 M NaCl and 2 mM EDTA, plus 200 µM-hypoxanthine as substrate, was saturated with O at 24°C. Portions of a solution (0.2 miu mL-1) of II were incubated for 30 min with I at final concentration. of 0.01 to 100 µM, then an aliquot was added to the buffer. After each addition the II activity was measured by electrochemical detection of uric acid at a carbon paste electrode maintained at 0.5 V vs. the SCE; a Pt counter-electrode was used. Alternatively, the II was applied to a carbon paste electrode and covered by a dialysis membrane. Under static conditions, the electrode was used in measurements on hypoxanthine solution in the Tris buffer after additions of I. A flow-through system incorporating a similar electrode was also constructed, which could be used in stopped-flow or flow injection mode; I could be determined either from its inhibiting effect on II or directly by measuring the superoxide radical produced by enzymatic conversion of I into oxypurinol. The direct method is considered to be advantageous owing to the quasi-reversiblity of II inhibition.
Allopurinol Electrochemical analysis Electrode Electrode

"Kinetic Determination Of Sulfonamides At The Millimolar Level By The Continuous Addition Of Reagent Technique"
Anal. Chim. Acta 1990 Volume 237, Issue 2 Pages 353-359
M. M&aacute;rquez, M. Silva and D. P&eacute;rez-Bendito

Abstract: A sulfonamide solution was mixed with 5 mM 1-naphthol in ethanol and 1.0 M acetic acid - Na acetate buffer (pH 4.15) and the mixture was diluted with water. The reaction was developed by continuous addition of 1 M NaNO2 at 0.5 mL min-1 with stirring at 200 rpm. The production of an azo dye was monitored at 470 nm. The calibration graph was rectilinear from 3 to 30 µM. The coefficient of variation for 18.7 µM-sulfonamide was 1.0% (n = 11) and the sampling rate was 25 h-1. The detection limit was 1.5 to 2.0 µM. The method is more sensitive than a reported flow injection method and more rapid than the conventional photometric micellar method. The technique was used for the determination of sulfonamides in pharmaceuticals.
Sulfonamides Pharmaceutical

"Utilization Of Adsorption-immobilized Urease In Gas Diffusion Flow Injection"
Anal. Chim. Acta 1990 Volume 237, Issue 2 Pages 503-508
T. L. Spinks and G. E. Pacey

Abstract: The enzyme was immobilized by addition of perfluorialkyl chains to the free amine groups of the enzyme and then adsorption on a PTFE gas-permeable microporous membrane. Injections. of 100 µL of urea were made into a carrier stream of 0.02 M Tris - HCl buffer (pH 8.5) at 0.9 mL min-1. This stream was merged with another stream of the same buffer. When the sample plug reached the membrane there was a 1 min stopped-flow period for conversion of the urea to NH3. The indicator on the acceptor side was Tecator NH3 - N mixed indicator (pH 6.4). When the streams were re-started the change in indicator absorbance was measured at 590 nm. The method was applicable in the range 0.1 to 500 mM urea. The method was used for the determination of urea in whole blood serum, with a sample throughput of 50 samples h-1.
Urea Blood Serum Spectrophotometry

"Enzyme Co-immobilization For The Sequential Determination Of Lactic Acid And Glucose In Serum"
Anal. Chim. Acta 1990 Volume 238, Issue 2 Pages 411-415
M. T. Morales, P. Linares, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: Lactic acid (I) and glucose (II), in a phosphate buffer carrier solution (pH 8.5), were determined by flow injection analysis in a reactor of immobilized glucose-6-phosphate dehydrogenase, hexokinase and L-lactate dehydrogenase at pH 8.0. The products, NADH and NADPH, from I and II, respectively, were monitored at 340 nm. Calibration graphs were rectilinear from 10 to 400 and 2 to 100 µg mL-1 of I and II, respectively, with corresponding coefficient of variation (n = 11) of 1.63 and 2.30%. Recoveries were 88.84 to 118.4% for I and 92.72 to 110.3% for II in serum. Mixtures of the analytes (up to 1:10) could be resolved.
Lactic acid Glucose Blood Serum

"Determination Of A Non-ionic Surfactant In Aqueous Environmental Samples By Flow Injection Analysis With Chemiluminescence Detection"
Anal. Chim. Acta 1990 Volume 239, Issue 2 Pages 189-194
J. Steven Lancaster and Paul J. Worsfold, A. Lynes

Abstract: Nonidet AT 85 was determined in seawater, with use of a glass coil flow cell; sample (100 µL) was merged first with borate buffer, pH 10.5, then with 4.45 mM rhodamine B and finally with 0.46 M NaOCl. The luminescence was measured with a photomultiplier. The response was rectilinear up to 50 mg L-1 with a limit of detection of 5 mg L-1 and coefficient of variation (n = 6) from 2.9% to 26.8% for these limits, respectively.
Surfactants, non ionic Environmental Sea Chemiluminescence

"Determination Of L-alanine In A Flow Injection System With An Immobilized Enzyme Reactor"
Anal. Chim. Acta 1990 Volume 239, Issue 2 Pages 307-310
Nobutoshi Kiba, Hirohisa Tagami and Motohisa Furusawa

Abstract: The sample was injected into a merged stream of 15 mM NAD+ and 0.2 M glycine - NaCl - NaOH buffer, pH 10.3, at 0.8 mL min-1, which flowed into a reactor of alanine dehydrogenase immobilized on poly(vinyl alcohol) beads at 40°C. The fluoresence of the NADH produced was measured at 465 nm (excitation at 340 nm). The response was rectilinear from 0.5 to 500 µM, with a limit of detection of 0.2 µM and a coefficient of variation (n = 9) of 0.9% for 100 µM. The coefficient (n = 5) for serum and beverages were between 1% for 0.02 to 410 µM.
l-Alanine Beverage Blood Serum Fluorescence

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

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

"Flow Injection Diode-array Detection: A Hybrid Approach To The Automation Of Simultaneous Determinations Of Metal Ions With Chromogenic Reagents"
Anal. Chim. Acta 1990 Volume 241, Issue 1 Pages 153-159
A. Gallardo Melgarejo and J. M. Cano Pav&oacute;n, A. R&iacute;os Castro

Abstract: The system was demonstrated by the determination of Ni(II) and Zn(II) with 0.8 mM 1-(2-pyridylazo)-2-napthol in ethanol - water (2:3) and acetate buffer, pH 4.8, in the same solvent, as the carrier at 1.5 mL min-1. The overlapping spectra were resolved by their second derivatives with scans every 1 s from 500 to 600 nm, the optimum wavelengths being 550 nm for Zn and 562 nm for Ni. The coefficient of variation (n = 11) for 3 µg mL-1 of Zn and 2 µg mL-1 of Ni were 3.8 and 4.0%, respectively.
Metals Zinc(II) Nickel(II) Spectrophotometry Spectroscopy

"Kinetic - Enzymic Determination Of Oxalate In Urine By Flow Injection Analysis With Double Stopped-flow"
Anal. Chim. Acta 1991 Volume 242, Issue 2 Pages 179-183
Juan A. Infantes, Mar&iacute;a Dolores Luque de Castro and Miguel Valc&aacute;rcel

Abstract: The method involved injection of a sample (acidified and filtered) into NAD+ solution in citrate buffer (pH 3.2). The flow was stopped with the sample plug in a reactor containing oxalate decarboxylase immobilized on glass. After 3 min, flow was re-started and the carrier was merged with formate dehydrogenase solution in phosphate buffer (pH 9.5). When the sample plug reached a flow cell, flow was again halted, and the absorbance at 340 nm was measured vs. time for 60 to 240 s. Calibration graphs were rectilinear for 0.1 to 3 mM oxalate. The coefficient of variation (n = 3) were 2.1 to 5.1%, and recovery was 94 to 105.5%. Sensitivity increased with increased measuring time, but the sampling rate fell from 20 to 12 samples h-1.
Oxalate Urine

"Flow Injection System For The Fluorimetric Determination Of Fructose With An Immobilized Mannitol Dehydrogenase Reactor"
Anal. Chim. Acta 1991 Volume 243, Issue 2 Pages 183-186
Nobutoshi Kiba, Yukari Inoue and Motohisa Furusawa

Abstract: Sample solution was injected into a carrier stream of water (0.5 mL min-1), which was merged with 10, 100 or 200 µM-NADH in 0.2 M phosphate buffer (pH 7.0; 0.5 mL min-1) for reaction in a reaction column (5 cm x 4 mm) of mannitol dehydrogenase immobilized on poly(vinyl alcohol) beads (prep. described) at 40°C. The decrease in NADH was monitored fluorimetrically at 465 nm (excitation at 340 nm). Calibration graphs were rectilinear for 3 to 30, 15 to 150 or 60 to 600 µM-fructose (I) for 10, 50 and 200 µM-NADH, respectively; the detection limit was 1 µM-I for 10 µM-NADH. Seventeen carbohydrates did not interfere; D-mannitol did interfere. The sampling rate was 30 h-1. The column retained >80% of its activity after continuous use over 2 months. The method was applied in the determination of I in fruit juice, wine and cola.
Fructose Wine Fruit Soft drink Fluorescence

"Flow Injection Determination Of D-mannitol With Immobilized Mannitol Dehydrogenase"
Anal. Chim. Acta 1991 Volume 244, Issue 1 Pages 105-107
Nobutoshi Kiba, Yukari Inoue and Motohisa Furusawa

Abstract: In the flow injection method described (diagram of apparatus given), 5 mM NAD+ was mixed with 0.2 M carbonate buffer of pH 10.0 (total flow-rate 0.5 mL min-1) and passed through a mixing coil (1 m x 0.5 mm). Sample solution (50 µL) was injected into the stream, the mixture was passed through a column reactor (5 cm x 4 mm) containing mannitol dehydrogenase immobilized on poly(vinyl alcohol) beads (cf., Ibid., 1991, 243, 183) at 37°C and the NADH produced was detected fluorimetrically at 465 nm (excitation at 340 nm). The calibration graph was rectilinear for 0.5 to 100 µM-D-mannitol and the detection limit was 0.1 µM. The sampling rate was 30 h-1 and the coefficient of variation (n = 12) was 1%. The method was applied in the analysis of celery juice and chewing gum (prep. described); results compared well with those by a chromatographic method. The method should also be applicable to biological samples.
d-Mannitol Juice Food Fluorescence

"Spectrofluorimetric Determination Of Diquat By Manual And Flow Injection Methods"
Anal. Chim. Acta 1991 Volume 244, Issue 1 Pages 99-104
T. P&eacute;rez-Ruiz, C. Mart&iacute;nez-Lozano and V. Tom&aacute;s

Abstract: In the manual method, sample solution, containing 0.03 to 9 µg of diquat (I), was mixed with 2 mL of 0.5 M borax buffer (pH 8), 1 mL of 0.5% sodium dithionite and water to 10 mL and, after 5 min, the resulting stable radical of I was detected fluorimetrically at 497 nm (excitation at 428 nm). The method was also adapted for use in a flow injection procedure (diagram of apparatus and details given. The calibration graph was rectilinear from 3 to 900 and 18 to 4000 µg L-1 of I by the manual and flow injection methods, respectively; the detection limit by the manual method was 0.4 µg L-1 and coefficient of variation were 2%. The method was applied in the determination of I in commercial herbicide formulations, water, potatoes, flowers and soil (sample prep. described) and in serum and urine directly with use of a standard additions method.
Diquat Blood Serum Urine Environmental Vegetable Plant Environmental Fluorescence

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

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

"Monitoring Of Mouse Immunoglobulin G By Flow Injection Analytical Affinity Chromatography"
Anal. Chim. Acta 1991 Volume 245, Issue 1 Pages 1-6
W. St&ouml;cklein, V. J&auml;ger and R. D. Schmid

Abstract: Oxiran acrylic beads (Sigma) (10 mg) were incubated at room temperature for 15 h with 1 M phosphate buffer (pH 7.5) (200 µL) and antibody (rabbit, sheep or goat anti-mouse IgG) or protein A solution (40 to 300 µL), corresponding to 0.5 mg of protein. Remaining oxiranyl groups were blocked by addition of 1 M ethanolamine (1 ml) and further incubation (2 h). The analytical column (1.5 cm x 1 mm) was filled with the prepared beads and formed part of the flow injection system. The procedure comprised: injection of sample or standard (35 µL), diluted as required with phosphate-buffered saline containing 0.1% of bovine serum albumim, 20 mM NaN3 and 0.1% of thiomersal; washing with phosphate-buffered saline containing 20 mM NaN3 and 0.1% of 6-aminohexanoic acid; and elution with 0.1 M Na citrate (pH 3.0 for protein A, pH 2.5 for antibodies) containing 20 mM NaN3. Detection was by fluorescence at 280 nm (excitation) and 360 nm (emission). The calibration graph was rectilinear up to 200 µg mL-1 of mouse IgG standard with use of protein A and up to 75 µg mL-1 with use of antibodies. Prerequisites for accurate determination are: the use of protein A as ligand if the mouse IgG sub-class is 2a, b or 3 and if calibration graphs already exist for these sub-classes; the use of an IgG standard from the same hybridoma line, irrespective of the ligand; or the use of a well-characterized mixture of anti-mouse IgG antibodies with equal affinities for each sub-class.
Immunoglobulin G Plasma Mouse LC Fluorescence

"Amperometric Glucose Sensor Based On Glucose Dehydrogenase Immobilized On A Graphite Electrode Modified With An NN'-bis(benzophenoxazinyl) Derivative Of Benzene-1,4-dicarboxamide [terephthalamide]"
Anal. Chim. Acta 1991 Volume 246, Issue 2 Pages 283-292
Miroslav Pol&aacute;ek, Lo Gorton, Roger Appelqvist, Gy&ouml;rgy Marko-Varga and Gillis Johansson

Abstract: Graphite rods were cut, polished, washed with water, dried at 60°C for 30 min and heated at 700°C for 90 s. The electrode was modified by application of several drops of an ethereal solution of terephthaloylbis-(5-imino-9H-benzo[a]phenoxazin-9-ylene)bis(diethylammonium chloride) and permitting the solvent to evaporate at ambient temperature Enzyme immobilization was effected by applying a buffered solution of glucose dehydrogenase - glutaraldehyde mixture. The sensor was used in a flow injection system with a buffered solution of NAD+ as carrier; the electrode potential was 0.0 mV vs. silver - AgCl. Calibration graphs were rectilinear for 3 to 500 µM-glucose. The sensor was also used to determine NADH, for which the calibration graph was rectilinear from 0.3 µM to 2 mM.
Glucose Amperometry Electrode Sensor

"Flow Injection Radio-release Analysis For Vanadium"
Anal. Chim. Acta 1991 Volume 246, Issue 2 Pages 329-331
Kate Grudpan and Duangjai Nacapricha

Abstract: The system consisted of a peristaltic pump that delivered the carrier solution (1.2 mL min-1) to a micro-column packed with 110 mAg powder; the packed column was shielded with lead. Acetate buffer solution (pH 3) was used as carrier solution Standard V solution (0.5 to 0.7 ml) was injected into the carrier stream and transported into the micro-column; the released radioactive Ag+ was detected by means of a flow-through coil mounted within a well-type NaI(Tl) detector. The detection limit was 10 µg mL-1 of V; calibration graphs were rectilinear up to 100 µg mL-1.
Vanadium

"Spectrophotometric Method For The Determination Of Ionic Surfactants By Flow Injection Analysis With Acidic Dyes"
Anal. Chim. Acta 1991 Volume 246, Issue 2 Pages 333-339
Koichi Yamamoto, Shoji Motomizu

Abstract: Two systems are described for the determination of cationic and anionic surfactants, respectively. In the former system, the reagent stream (0.37 mL min-1) consists of 25 µM-bromocesol purple in 30 mM phosphate buffer (pH 8.1); a portion (200 µL) of the sample cationic surfactant (e.g., benzyldimethyltetradecylammonium chloride) solution is injected into a carrier stream (0.37 mL min-1) of water. After reaction in the reaction coil (200 cm x 0.5 mm), the resulting decrease in absorbance at 588 nm is measured and related to the surfactant concentration.; calibration graphs are rectilinear up to 50 µM. No interference was observed from ions commonly present in river water. In the second system, anionic surfactants are determined by a similar method, except that the carrier solution is replaced by 40 µM-benzylhexadecyldimethylammonium chloride; the method is based on reaction between the anionic surfactant (analyte) and the cationic surfactant in the carrier stream, which results in a depression of the decrease in absorbance at 588 nm.
Surfactants, anionic Surfactants, cationic River Spectrophotometry

"Comparison Of Two Fibre-optic L-glutamate Biosensors Based On The Detection Of Oxygen Or Carbon Dioxide, And Their Application In Combination With Flow Injection Analysis To The Determination Of Glutamate"
Anal. Chim. Acta 1991 Volume 248, Issue 2 Pages 351-359
Bernd A. A. Dremel and Rolf D. Schmid, Otto S. Wolfbeis

Abstract: Food or pharmaceutical prep. was dissolved in boiling H20 and the mixture was filtered. The filtrate was subjected to flow injection analysis with mixing with the carrier solution [0.1 M potassium phosphate buffer (pH 7.0 or 5.0)] and passing through an air damper before detection in the flow-through cell with use of a glutamate biosensor. The biosensor was based on (i) oxygen optrode with immobilized glutamate oxidase, or (ii) carbon dioxide optrode with immobilized glutamate decarboxylase. Detection was at 495 or 560 nm (excitation at 400 or 460 nm) for detectors (i) and (ii), respectively. The corresponding calibration graphs were rectilinear for 0.02 to 1 mM and 0.1 to 2.5 mM glutamate. The coefficient of variation were ~3% (n = 5). Interference from volatile acids was observed with detector (ii). Detector (i) was recommended.
Carbon dioxide Glutamate Oxygen Food Pharmaceutical Fluorescence Sensor Optrode

"Continuous Monitoring Of Gas-phase Species At Trace Levels With Electrochemical Detectors. II. Detection Of Chlorine And Hydrogen Chloride"
Anal. Chim. Acta 1991 Volume 248, Issue 2 Pages 391-398
Wojciech Matuszewski and Mark E. Meyerhoff

Abstract: The sample gases were trapped through the wall of a microporous polypropylene tube into the recipient buffer solution [10 mM borate (pH 9.0)]. Detection was initially made potentiometrically with Ag - AgCl working electrode, followed by biamperometric detection at 100 mV with two Pt electrodes. The limits of detection were 0.75 and 2.1 ppb of Cl and HCl gas, respectively, with use of the continuous-flow method. The method was applicable to air. For Part I, see previous abstract.
Chlorine Hydrogen chloride Environmental Biamperometry Electrode Electrode Potentiometry

"Flow Injection ELISA For Process Monitoring And Control"
Anal. Chim. Acta 1991 Volume 249, Issue 1 Pages 163-168
Mats Nilsson, H&aring;kan H&aring;kanson and Bo Mattiasson

Abstract: A fully automated competitive flow injection ELISA is described (with diagrams). The flow system is computer-controlled and its operation involves mixing of sample and labelled antigen solution, passing of this mixture through a column containing immobilized antibodies, application of substrate solution at the column, spectrophotometric detection and column reconditioning with buffer solution The system was evaluated with the determination of IgG with a protein A - sepharose column and horse-radish peroxidase-labelled rabbit anti-human IgG.
Immunoglobulin G Spectrophotometry

"Immunological Online Detection Of Specific Proteins During Fermentation Processes"
Anal. Chim. Acta 1991 Volume 249, Issue 1 Pages 113-122
Ruth Freitag, Christel Fenge, Thomas Scheper, Karl Sch&uuml;gerl, Andreas Spreinat, Garo Antranikian and Elisabeth Fraune

Abstract: A merging zones stopped-flow flow injection system is described (with diagram) for online immunoturbidimetric determination of proteins in fermentation processes. Sample and reagent solution are injected into separate buffer streams, the streams are merged and the flow is stopped to allow incubation at 37°C. After incubation, turbidity is measured at 340 nm vs. a sample blank. For determination of monoclonal IgG, the reagent solution (0.1 mL min-1) was anti-mouse IgG (1.8 mg mL-1), the buffer solution (1 mL minmin1) was 0.01 M sodium phosphate buffer solution (pH 7.2) containing PEG 6000 (30 g l-1) and NaCl (4.5 g l-1) and the incubation time was 90 s. For assay of α-dextrin endo-1,6-α-glucosidase (I), the reagent was rabbit anti-I antibody solution, the buffer solution was the same as that for IgG, but with 40 g L-1 of PEG 6000, and the incubation time was 120 s. From 10 to 1000 iu L-1 of I and 1 to 1000 mg L-1 of IgG could be determined.
Proteins Fermentation broth Turbidimetry

"Amperometric Glucose Sensor With A Photolithographically Patterned Enzyme Membrane"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 117-120
T. Vopel, A. Ladde and H. M&uuml;ller*

Abstract: A solution (0.25 ml) containing partially hydrolyzed poly(methyl methacrylate), bisphenol A, bis-(2-hydroxypropyl methacrylate), Michler ketone and benzophenone was mixed with glucose oxidase (26 iu mg-1) and dodecyltrimethylammonium chloride for 5 min in an ultrasonic bath. The mixture was either dropped or spin-coated on to multi-layer thin film Ti - Au - Pt electrodes. The layer was dried at room temperature, exposed to UV radiation and developed in ethyl methyl ketone. The electrodes were conditioned for 1 hr in phosphate buffer solution For an electrode with a 10 µm thick membrane, the calibration graphs were rectilinear from 0.05 to 3.5 mM glucose in batch mode and 0.05 to 5 mM glucose in flow injection mode.
Glucose Amperometry Electrode Electrode Electrode Sensor

"Flow Injection Analysis With Tetrameric Calixarene-based Potentiometric Detection"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 149-155
Martin Telting-Diaz, Dermot Diamond* and Malcolm R. Smyth

Abstract: A thin-film membrane was prepared (described) containing methyl p-t-butylcalix[4]aryl acetate or p-t-butylcalix[4]arene methyl tetraketone, K tetrakis-p-chlorophenylborate, 2-nitrophenyl octyl ether and PVC. The membrane was inserted into a flow-through potentiometric detector for flow injection analysis. For determination of Na, plasma was diluted 10-fold with Tris buffer and a 100 µL portion was injected into a carrier stream containing physiological concentration. of plasma electrolytes. Results compared well with those obtained with a Technicon analyzer..
Sodium Blood Plasma Electrode Potentiometry

"Post-column Liquid Chromatographic Method For The Determination Of Cyanide With Fluorimetric Detection"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 255-259
Keiji Gamoh*, Senya Imamichi

Abstract: Cyanide ions were separated from other ions by ion-exclusion HPLC on a Shim-pack SCR-102H column operated at 40°C with 10 mM HClO4 as mobile phase (1 mL min-1). Column eluate was mixed at 40°C with 2 mM phthalaldehyde (OPA) or naphthalenedicarboxaldehyde (NDA) and 20% ethanolic 0.5 mM Na4 EDTA in carbonate - borate buffer solution and then with 2 mM amino acid and 0.5 mM Na4 EDTA in carbonate-borate buffer. Fluorimetric detection was at 400 nm (excitation at 330 nm) for CN- - OPA derivatives or at 490 nm (excitation at 420 nm) for CN- - NDA derivatives. Use of NDA gave the best sensitivity. The calibration graph was rectilinear from 0.5 µg L-1 to 2 mg L-1 of CN-. The detection limit was ~0.1 µg l-1. The coefficient of variation (n = 10) were 1.4% at 10 µg L-1 and 3.1% at 0.5 µg l-1.
Cyanide HPLC Fluorescence

"Dehydrogenase And Ethanol Assay Based On Visible Semiconductor Laser Spectrometry"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 191-195
Totaro Imasaka, Toshiyuki Higashijima and Nobuhiko Ishibashi*

Abstract: Methods are described for the assay of dehydrogenases and the determination of NAD+ and ethanol based on visible semiconductor laser spectrometry of methylene blue. Lactate dehydrogenase (I) was assayed in serum by using a batch system. Serum (20 µL) was incubated at 37°C for 20 min with reagent solution (1 ml) containing lactic acid, NAD+, diaphorase and methylene blue in Tris buffer solution (pH 8.6) and the reaction was stopped with 1 M HCl (5 ml). Fluorescence was measured with a semiconductor laser fluorimeter. Alcohol dehydrogenase (II) and ethanol (III) were determined by using a flow system (described with diagram). II solution (0.5 µL) was injected into a merging zone (5 µL) containing diaphorase (0.6 iu), NADH (5 nmol), III (300 nmol) and 500 mM methylene blue at pH 8.7. III (1 µL) was injected into a merging zone containing II (0.6 iu), diaphorase (0.1 iu), NAD+ (5 nmol) and 500 mM methylene blue at pH 8.7. For NAD+ determination, the merging zone contained diaphorase (0.6 iu) and methylene blue (2.5 pmol) in Tris buffer solution (pH 8.7). Detection limits were 0.1 miu of II and 10 nmol of III. The calibration graph for NAD+ was rectilinear up to 40 nmol.
Ethanol Enzyme, lactate dehydrogenase Blood Serum Fluorescence Sensor

"Determination Of The Fluorescent Drugs Dipyridamole And Benzydamine In Rat Plasma By Liquid Chromatography With Peroxyoxalate Chemiluminescence Detection"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 247-253
Atsuhiko Nishitani, Yukie Tsukamoto, Susumu Kanda and Kazuhiro Imai*

Abstract: Plasma (10 µL) or, for dipyridamole (I) determination, plasma diluted 10-fold with 150 mM imidazole buffer solution (pH 6.0) was mixed with imidazole buffer solution (40 µL; as above), internal standard solution (20 µL) and acetonitrile (130 µL) and the mixture was centrifuged at 2500 g for 5 min. The internal standards were 5-(NN-dimethylaminonaphthalene)-1-sulfonyl-L-phenylalanine for I and I for benzydamine hydrochloride (II). Sample solution was injected into a flow system (described with diagram) containing a column (15 cm x 4.6 mm) of TSK ODS 8OTm (5 µm) operated at 40°C with 50 mM imidazole buffer (pH 6.0) - acetonitrile (1:1) as eluent. The eluate was mixed with 0.25 mM bis-[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl]oxalate and 12.5 mM H2O2 solution in acetonitrile - ethyl acetate (1:1) before detection of chemiluminescence. Calibration graphs were rectilinear from 2.5 to 200 nM-I and 2.5 to 100 µM-II. Detection limits were 345 pM-I and 147 nM-II.
Benzydamine Dipyridamole Plasma Rat Chemiluminescence LC

"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

"Polyaniline Chemically-modified Electrode For Detection Of Anions In Flow Injection Analysis And Ion Chromatography"
Anal. Chim. Acta 1991 Volume 252, Issue 1-2 Pages 53-57
Erkang Wang* and Anhua Liu

Abstract: A film of polyaniline was electrochemically deposited on a glassy carbon electrode (c.f., Ye and Baldwin, Anal. Chem., 1988, 60, 1979). With the electrode in FIA the maximum response for NO3-, I-, SCN-, Br-, SO42-, ClO4-, acetate and oxalate was at +0.4 V vs. SCE for 0.2 M acetate buffer eluent (pH 3.8), and at +0.6 V for 0.2 M boric acid (pH 5.2) or NaNO3 (pH 5.7). For ion chromatography the detector was used with a column of AS1 and a mobile phase of 0.06 M NaNO3 at 1.5 mL min-1. The calibration graphs for I-, Br-, SCN- and S2O32- were rectilinear from 2 to 100, 8 to 100, 15 to 100 and 15 to 100 mg L-1 with detection limits of 1, 5, 10 and 10 mg l-1, respectively. With FIA the range extended over >3 orders of magnitude with a detection limit for I- and ClO4- of 0.1 mg l-1.
Anions Iodide Perchlorate HPIC Electrode Electrode

"Flow Injection Determination Of Traces Of Formaldehyde By The Brilliant Green - Sulfite Reaction With Spectrophotometric Detection"
Anal. Chim. Acta 1991 Volume 252, Issue 1-2 Pages 167-171
A. Safavi* and A. A. Ensafi

Abstract: Solutions of SO32- (6 µg mL-1), phosphate buffer (pH 7.0), 50 µM-brilliant green (C. I. Basic Green 1) and the analyte (100 µL) were mixed in a flow injection system (diagram given) and the absorbance was measured at 615 nm at 25°C. The calibration graph was rectilinear from 4 to 300 ng of formaldehyde with a limit of detection of 20 ng mL-1. The coefficient of variation (n = 10) were 0.4% for 0.3 µg mL-1 and 0.2% for 1 µg mL-1. The method was applied to steam distillates from melamine - formaldehyde resin and industrial waste water. Other aldehydes only interfered at concentration. >20 µg mL-1.
Formaldehyde Industrial Spectrophotometry

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

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

"Rapid Screening Of Porphyrins Using Flow Injection Analysis And Visible Laser Fluorimetry"
Anal. Chim. Acta 1991 Volume 254, Issue 1-2 Pages 189-196
Carmen W. Huie, Joseph H. Aiken and William R. Williams

Abstract: Urine and serum were diluted with 0.15 M hexadecyltrimethylammonium bromide in 0.01 M NaH2PO4 buffer, pH 7.4, and the solution were injected into a carrier stream of the same buffer. The fluorescence of the compounds was measured at ~620 nm with excitation at 488 nm provided by an Ar laser. Urine spiked with 0.02, 0.04 and 0.06 µmM was clearly distinguishable from the blank, these concentration. representing the lower range for abnormal urine. With serum the limit of detection was ~0.015 µM.
Porphyrins Blood Serum Urine Fluorescence

"Flow Injection Determination Of Zinc By Fluorescence Spectrometry"
Anal. Chim. Acta 1991 Volume 255, Issue 2 Pages 325-328
R. Compa&ntilde;&oacute;, S. Hern&aacute;ndez-Cassou and M. D. Prat*, L. Garc&iacute;a-Beltr&aacute;n

Abstract: A flow injection manifold is illustrated in which a stream of succinate buffer solution (pH 6.1) containing masking agents, 0.1 M Na2S2O3 and/or Na pyrophosphate, was merged with a stream of Brij-35 surfactant (both at 5 mL min-1) in a 60-cm coil, before mixing with the sample stream (58 µL). The mixture was reacted with 1 mM 5,7-dichloro-2-methylquinolin-8-ol in aqueous 40% ethanol (1 mL-1) in a 30-cm coil, before fluorimetric detection at 534 nm (excitation at 397 nm). The calibration graph was rectilinear from 10 to 600 µg L-1 of Zn, with a detection limit of 3 µg l-1. The coefficient of variation (n = 15) was 1.8% for 200 µg Zn. Tolerance limits for interfering ions are tabulated; sampling time was 180 h-1. The method was applied to potable water and pharmaceutical preparations and results were in good agreement with those obtained by AAS and the values stated by manufacturers, respectively. The masking agent was more efficient in this flow injection system than one in which the reagent stream was mixed with the buffer and surfactant streams before mixing with the sample stream.
Zinc Pharmaceutical Water Fluorescence

"Flow Injection Determination Of L-glutamate In Serum With An Immobilized Glutamate Dehydrogenase Reactor"
Anal. Chim. Acta 1992 Volume 256, Issue 2 Pages 221-224
Nobutoshi Kiba*, Takami Moriya and Motohisa Furusawa

Abstract: Serum (10 µL) is treated with 10 µL of 5% Na2WO4 solution and 30 µL of 0.15 M H2SO4 and filtered through an Airpress-30 filter (Tosoh), and 30 µL of the filtrate is injected into a carrier stream (0.4 mL min-1) of 5 mM NAD+ in 0.05 M glycine buffer of pH 9.5. The stream passes through a stainless-steel column (3 cm x 4 mm) containing glutamate dehydrogenase (NAD(P)+) immobilized on poly(vinyl alcohol) beads (method described), and the NADH formed is detected at 465 nm (excitation at 340 nm). The calibration graph is rectilinear for 0.5 to 500 µM-glutamate, and the detection limit is 0.2 µM. Glutamate dehydrogenase is immobilized on poly(vinyl alcohol) beads and packed into a stainless-steel column (3 cm x 4 mm i.d.). Serum is deproteinized with tungstic acid. Sample solution (30 µL) is injected into the carrier stream [5 mM NAD+ in glycine buffer (pH 9.5)]. The NADH formed is detected at 465 nm (excitation at 340 nm). The calibration graph is linear for 0.5-500 µM glutamate; the detection limit is 0.2 µM.
l-Glutamate Blood Serum Fluorescence

"Determination Of Trace Amounts Of Lead By Chelating Ion Exchange And Online Preconcentration In Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 259, Issue 1 Pages 53-60
Rajesh Purohit and Surekha Devi*

Abstract: Resins synthesized from quinolin-8-ol and resorcinol or quinol, with furfuraldehyde, formaldehyde or benzaldehyde as cross-linking agent, were evaluated for the pre-concentration. of traces of Pb. Characteristics of each column are tabulated. Columns (2 to 3 cm x 2 mm) of any of the resins could be used in a flow system for separation of Pb from Cu or Zn. The metals were adsorbed at pH ~3 on to the resin, which was washed with acetate buffer solution of pH 3 before elution of (a) Pb with 0.05 M HNO3 followed by Cu(II) with 1 M HNO3 or (b) Zn with 0.2 M acetic acid followed by Pb with 0.1 M HNO3. The eluted metals were determined by flame AAS. There was no cross-contamination, and the detection limit was 10 ng mL-1 of Pb with pre-concentration. from 5 mL of solution Resins synthesized from quinolin-8-ol and resorcinol or hydroquinone, with furfuraldehyde, formaldehyde, or benzaldehyde as crosslinking agent, were used for the pre-concentration. of nanogram amounts of lead. The rate of exchange and activation energy of lead exchange were calculated Column sepns. of lead-copper and lead-zinc did not show any cross-contamination. A continuous-flow manifold using resin microcolumns was developed for the pre-concentration. and determination of lead.
Lead Ion exchange Spectrophotometry

"Porous-membrane Permeation Of Halogens And Its Application To The Determination Of Halide Ions And Residual Chlorine By Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 461-469
Shoji Motomizu* and Takehiro Yoden

Abstract: Details are given of a gas diffusion unit (diagram given) with an easily constructed tubular microporous PTFE membrane through which halogen molecules can permeate into an acceptor solution. The sample is introduced via a six-way valve with a variable loop into water as carrier, and this stream is mixed with an oxidizing reagent to generate the molecular halogen (e.g., 10 µM-KMnO4 - 1 M H2SO4 to produce I2 from I-; 0.1 M NaCl - 0.1 M H2SO4 to generate Cl2 from ClO-). After passage through a 10-cm mixing coil, the stream passes through the diffusion unit, where the halogen molecules pass into 0.2 mM NN-diethyl-p-phenylenediamine - 0.1 mM H2SO4 for spectrophotometric detection or (for Cl2) into 0.1 mM acetate buffer of pH 4.8 for potentiometric detection with a coated-wire ion-selective electrode. Conditions are described for the determination of I-, Br-, residual Cl and (by the reduction of I2 to I-, thus affording negative peaks) S2O32-. Microporous polytetrafluoroethylene membrane tubing was used to assemble a newly designed gas diffusion unit and was applied to the permeation of halogens. It was found that halogens such as bromine and iodine, which are not gaseous at room temp., permeated through the membrane tubing; the permeability decreased in the order chlorine > bromine > iodine. The permeated halogens react with N,N-diethyl-p-phenylenediamine to produce colored substances. By coupling this chromogenic reaction with the permeation of halogens, the sensitive and selective determination of halogens and halide ions can be achieved. Iodide and bromide ions were determined by spectrophotometric methods coupled with oxidation by permanganate. Thiosulfate was determined on the basis of the reduction of iodine to iodide. Residual chlorine was determined by a flow injection potentiometric method with a coated-wire ion-selective electrode, and by a flow injection spectrophotometric method.
Halides Chlorine, residual Spectrophotometry Potentiometry Electrode

"Spectrophotometric Determination Of Phenolic Compounds By Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 253-259
Wolfgang Frenzel* and Jolanta Oleksy-Frenzel, J&uuml;rgen M&ouml;rlen

Abstract: Methods involving reaction with (a) 4-aminoantipyrine (I) or (b) 3-methylbenzothiazolin-2-one hydrazone (II) have been evaluated with a view to the determination of phenolic compounds in water. The sample (400 or 300 µL, respectively) is injected into water as carrier, then merged with (a) 0.1% I solution in a buffer solution (pH 9.8 to 10.2) containing 0.52% of NaHCO3, 0.58% of H3BO3 and 0.62% of KOH, or (b) aqueous 0.1% II. The resulting solution is treated with (a) 0.2% K3Fe(CN)6 solution adjusted to pH 11 with NaOH or (b) 0.2% (NH4)4Ce(SO4)4 solution in H2SO4 (4 mL l-1) as oxidant. In method (b) provision is made for the optional addition of a buffer solution (0.5% of NaOH, 0.2% of Na2EDTA and 0.8% of H3BO3). The absorbance is measured at (a) 510 or (b) 470 nm; the latter is a compromise value. Method (b) is the more sensitive (detection limit for phenol 12 µg l-1, compared with 30 µg l-1) and responds to various compounds that do not react with I, but the λmax values cover a wide range. Flow injection procedures for the spectrophotometric determination of PhOH in water by 2 different color reactions were developed. The common 4-aminoantipyrine (4-AAP) reaction and the oxidative coupling of PhOH with 3-methyl-2-benzothiazoline hydrazone (MBTH) are both readily applicable and permit the determination of PhOH at a sampling rate of 60 h-1 and a relative standard deviation better than 3%. The sensitivity of the MBTH method is ~4 times higher than that of the 4-AAP reaction, with detection limits of 12 and 30 µg/L PhOH, respectively. A study of the responses of the 2 methods to PhOH derivatives revealed particular merits and limitations. The 4-AAP reaction products have similar absorbance max. but the reactivity is comparatively low. MBTH reacts with several p-substituted phenols and exhibits higher response factors. Because the absorption max. of the products differ significantly, a problem is the appropriate choice of the measuring wavelength.
Phenols Spectrophotometry

"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

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

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

"Trace Gold Determination In Cyanide Process Solutions - Preconcentration Using Supported Liquid Membranes In A Flow Injection Manifold"
Anal. Chim. Acta 1992 Volume 265, Issue 1 Pages 71-79
M. J. C. Taylor*, D. E. Barnes and G. D. Marshall

Abstract: The Au(CN)2- anion was extracted into a supported liquid membrane, formed by the in situ coating of a thin layer of organic phase onto a polymeric support. Of the systems tested, the most selective was a 1% solution of tridecylamine in a diluent consisting of 50% TBP in heptane, supported on Polysorb MP-1. This material was packed into a mini-column which formed part of a flow injection manifold. Sample (10 ml) was adjusted to pH 8 with 0.5 M triethanolamine - Titriplex III buffer. After the solution had flowed over the liquid membrane for a suitable time, the entire organic phase was washed off the column with methanol and introduced into the flame of an atomic absorption spectrometer. At a load time of 120 s and a flow-rate of 5 mL min-1, a 53-fold pre-concentration. of Au was achieved and the throughput was 24 samples h-1. The method allowed the determination of Au in the range 0.01 to 0.1 mg l-1, and the detection limit was 5 µg l-1. The coefficient of variation was 2.7% at the 40 µg L-1 level. A 20-fold excess of Ag could be tolerated. A method for the determination of traces of gold in cyanide process solutions has been developed. Preconcentration. of the dicyanoaurate(I) anion is achieved by extraction into a supported liquid membrane, formed by the in situ coating of a thin layer of organic phase onto a polymeric support. This support is packed into a minicolumn, which forms part of a flow injection manifold. After the sample solution has flowed over the organic phase for a suitable period, the entire organic phase is washed off the column with an organic solvent and introduced into the flame of a conventional atomic absorption spectrometer. The method allows gold to be determined in the range of 0.01 to 0.1 mg/L with a 2-7% relative standard deviation of the 0.04 mg/L level. With an anal. time of 150 s per sample, a detection limit of 0.005 mg/L was achieved with a sampling frequency of 24 h-1.
Gold Cyanide Spectrophotometry Sample preparation

"Zeptomole Detection Limit For Alkaline Phosphatase Using 4-aminophenylphosphate, Amperometric Detection, And An Optimal Buffer System"
Anal. Chim. Acta 1993 Volume 271, Issue 2 Pages 223-229
Robert Q. Thompson*, Margaret Porter and Cameron Stuver, H. Brian Halsall and William R. Heineman, Eileen Buckley and Malcolm R. Smyth

Abstract: The trace detection of bovine alkaline phosphatase using the substrate 4-aminophenylphosphate and amperometric measurement of the product, 4-aminophenol, was studied. The effects of buffer type, pH, buffer concentration, and additives (Zn and Mn) on the activity of alkaline phosphatase and on the detection of 4-aminophenol were examined. The buffers studied were ethanolamine, diethanolamine, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, triethanolamine, and tris(hydroxymethyl)aminomethane. The detection limits for alkaline phosphatase were determined using a flow injection amperometric system. At pH 10.0, 2-(methylamino)ethanol buffer and in the presence of 1 mg mL-1 of MgCl2 the detection limit for aqueous mouse IgG - alkaline phosphatase conjugate was 25 amol mL-1 or 500 zeptomoles (10-21 mol).
Enzyme, alkaline phosphatase Amperometry

"Fluorescence-based Flow Injection Determination Of Biotin And Biotinylated Compouds"
Anal. Chim. Acta 1993 Volume 279, Issue 2 Pages 287-292
Truis Smith-Palmer, Minas S. Barbarakis, Tadeausz Cynkowski and Leonidas G. Bachas*

Abstract: The assay described was based on the enhancement of the emission intensity of the fluorescein-labelled conjugate of streptavidin by the biotin moiety. A merging-zone FIA system was used in which 70 µL of streptavidin-fluorescein isothiocyanate reagent (1.0 mg/l) was injected into one buffer stream and 70 µL of sample was injected into a second buffer stream. Both streams consisted of 50 mM phosphate buffer of pH 8 (1 ml/min). The streams were merged and passed through a 2-m knitted open-tubular reactor coil into the detection cell were the emission signal at 518 nm was recorded (excitation at 495 nm). The calibration graphs for biocytin, biotin, biotin-thyroxine and biotinylated BSA were linear at low concentration. (0.4 µM) but the gradients varied considerably. The detection limit was 2 nM-biotin.
Biotin Biocytin Biotin thyroxine Albumin, biotinylated Cow Serum Fluorescence

"Dual Flow Injection Analysis System For Determining Bromide And Reactive Phosphorus In Natural Waters"
Anal. Chim. Acta 1993 Volume 282, Issue 2 Pages 379-388
Paul R. Freeman, Barry T. Hart and Ian D. McKelvie

Abstract: A computer-controlled injection system (description given) and a manifold constructed from PTFE tubing were used in the simultaneous determination of P and bromide by methods based on previously published methods (cf. Ibid., 1990, 234, 409; and Anagnostopoulou and Koupparis, Anal. Chem., 1986, 58, 322). The bromide was determined first by injecting a sample (60 µL) into a stream of water (0.75 ml/min) which was mixed (0.31 ml/min) with 2.4 mM HCl in a 30 cm coil before removal of dissolved organic matter in a PVC column (2 cm x 2.8 mm i.d.) containing Sep-Pak C18. Streams (0.31 ml/min) of 0.01 or 0.02 g/l of phenol red, e.g., in 50 mM acetate buffer, and chloramine T, were mixed in a 60 cm coil before mixing with the column eluate in a 43 cm coil and detection at 583 nm. To determine P, a sample (600 µL) was injected into a stream of water (1.2 ml/min) and mixed with acid molybdate and SnCl2 streams (0.54 ml/min) in 30 and 120 cm coils, respectively, before detection at 650 nm. Calibration graphs were linear up to 2 mg/l of bromide and 50 µg/l of P and the detection limits were 4 and 0.6 µg/l, respectively. The corresponding RSD ranged from 0.3-5.3 (n = 10) and 0.5-2.9% (n = 3).
Bromide Phosphorus Environmental Spectrophotometry

"Flow Injection Study Of Inhibition And Reactivation Of Immobilized Acetylcholinesterase: Determination Of The Pesticides Paraoxon And Carbamoylcholine"
Anal. Chim. Acta 1993 Volume 282, Issue 2 Pages 307-312
I. A. Takruni, Ala'ddin M. Almuaibed and Alan Townshend

Abstract: To determine paraoxon (I), the sample solution (60 µL) was injected into a carrier stream of 50 mM potassium phosphate buffer of pH 8 (1 ml/min) flowing through a PTFE manifold (50 µm i.d.). A solution of 7 mM acetylthiocholine iodide (60 µL) was injected into the centre of the I plug 10 cm downstream of the first injection point and the stream was passed through a glass column (2 cm x 2.5 mm i.d.) of acetylcholinesterase immobilized on controlled-pore-glass beads. The presence of I in the column inhibited the catalytic activity of the enzyme in the hydrolysis of acetylthiocholine iodide to thiocholine determined spectrophotometrically according to Quintero et al. (Talanta, 1991, 38, 1273) after mixing the column effluent with 1 mM 5,5'-dithiobis(2-nitrobenzoic acid). The total uninhibited catalytic activity of the acetylcholinesterase was determined similarly by injecting acetylthiocholine iodide after reactivation of the enzyme by pyridine-2-aldoxime methochloride. Calibration graphs were linear up to 0.8 mM I and the detection limit was 50 µM-I. The RSD (n = 5) was 5% for 0.6 mM I. A procedure for determining up to 0.6 mM carbamoylcholine was also described.
Pesticides Paraoxon Carbamoylcholine Spectrophotometry

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

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

"A Mechanized System For The Determination Of Low Levels Of Quickly Reacting Aluminium In Natural Waters"
Anal. Chim. Acta 1995 Volume 306, Issue 2-3 Pages 173-181
Lars-G&ouml;ran Danielsson and Anders Spar&eacute;n*

Abstract: A continuous flow system has been connected to a graphite furnace atomic absorption spectrometer. The system is used to determine low levels of 'quickly reacting Al' (Alqr) in natural waters. In the flow system, aluminium reacts with oxine for 2.3 s and the formed complex is then extracted into toluene. Iron interference is minimized with a masking buffer present in the reagent. Via a simple interface, the toluene extract is introduced into the graphite tube. Good repeatabilities (RSD ~2%, n = 10) were obtained, both for standard solutions and for natural waters. The detection limit is < 0.5 g l-1, and the sample throughput using 3 injections/sample, is ~10 samples h-1. The system has been used for determining Alqr in tap water, and is well suited for aluminium fractionation in near-neutral waters.
Aluminum, reactive Environmental Water 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

"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

"Multicomponent Flow Injection Based Analysis With Diode-array Detection And Partial-least-squares Multivariate Calibration Evaluation. Rapid Determination Of Calcium(II) And Magnesium(II) In Waters And Dialysis Liquids"
Anal. Chim. Acta 1996 Volume 320, Issue 2-3 Pages 177-183
O. Hern&aacute;ndez, F. Jim&eacute;nez, A. I. Jim&eacute;nez, J. J. Arias,* and J. Havel

Abstract: The FIA manifold comprised 0.5 mm i.d. PTFE capillaries, a 4-way injection valve and a peristaltic pump. Samples were injected in to 2 mM 4-(2-pyridylazo)-resorcinol in 0.1 M Tris buffer of pH 9.6 (2 ml/min) and after passage through a reaction coil (80 cm) spectra were recorded on a diode array spectrophotometer every 1s. A partial least squares method was used for calibration (details given). The system was used to determine Ca and Mg in potable waters and dialysis liquids and in mixtures of Ca, Mg and Cu. Satisfactory results were obtained with a scanning time equivalent to 21 s and wavelengths of 510 nm to 552 nm. Sample throughput was 30 per hour.
Calcium(2+) Magnesium(II) Water Dialysis Fluid Spectrophotometry

"Spectrofluorimetric Flow Injection Method For The Successive Determination Of Chloroxine And Chlorquinaldol In Pharmaceutical Preparations"
Anal. Chim. Acta 1996 Volume 326, Issue 1-3 Pages 41-47
Tom&aacute;s P&eacute;rez-Ruiz*, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Jos&eacute; Carpena

Abstract: The FIA method was based on the formation of fluorescent complexes between Al(III) chloroxine (5,7-dichloroquinolin-8-ol; COX) and Cd(II) and both COX and chlorquinaldol (CQD). A sample volume of 95 µL was injected into a 14 mM SDS carrier stream (1.2 ml/min) and merged with 0.2 M acetate buffer of pH 4.2 (0.4 ml/min) and 2.5 mM Al(III) (0.4 ml/min). The Al(III)-COX complex was determined at 550 nm (excitation at 395 nm). For the combined determination of COX and CQD, a 235 µL sample volume was injected into a 18 mM cetyltrimethylammonium bromide carrier stream (1.2 ml/min) and merged with 0.2 M phosphate buffer of pH 8.3 (0.4 ml/min) and 2 mM Cd(II) (0.4 ml/min). The combined fluorescent intensity of Cd(II)-COX and Cd(II)-CQD was measured at 550 nm (excitation at 395 nm). Linear calibration graphs were obtained for 0.13-13 µg/ml COX and 0.09-13.2 µg/ml CQD and detection limits were 0.04 and 0.02 µg/ml, respectively. The RSD (n = 11) for the analysis of a mixture containing 2.5 µg/ml COX and 3 µg/ml CQD were 0.81 and 0.29%, respectively. The method was applied to the analysis of pharmaceutical preparations and the results were in agreement with manufacturers` specifications.
Chloroxine Chlorquinaldol Pharmaceutical Fluorescence

"Automated Analytical Biosystem For Urea Monitoring"
Anal. Chim. Acta 1996 Volume 327, Issue 3 Pages 243-251
M. Jurkiewicz, M. Del Valle, S. Alegret and E. Mart&iacute;nez-F&aacute;bregas*

Abstract: Sample was injected into a carrier stream of 0.1 M Tris buffer of pH 7.4. The stream flowed through a nylon column onto which urease was previously immobilized. The carrier stream containing the hydrolyzed ammonium ions was then merged with a stream of 1 M NaOH and passed through a reaction tube. The resulting NH3 gas was transported to a gas diffusion cell in which NH3 gas diffused through a hydrophobic membrane into another carrier solution of 0.1 M Tris buffer for measurement by an ammonium ISE. Measurements were made relative to a Ag/AgCl reference electrode. Under optimum conditions, calibration graphs were linear for 30 µM to 3 mM. For hemodialysis measurements, the experimental parameters had to be adjusted; under such conditions the response was linear only for 1-2 mM.
Urea Potentiometry Electrode

"Electroluminescent Detection Of Enzymatically Generated Hydrogen-peroxide"
Anal. Chim. Acta 1996 Volume 327, Issue 3 Pages 253-260
MaEsther Fern&aacute;ndez Laespada, Jos&eacute;Luis P&eacute;rez Pav&oacute;n and Bernardo Moreno Cordero*

Abstract: The present work studies the analytical possibilities of the electroluminescent detection of hydrogen peroxide generated in an enzymatic reaction. Glucose oxidation through the enzyme glucose oxidase (GOD) was used as the study system. The hydrogen peroxide generated reacts in situ with the radical obtained by electrochemical oxidation of luminol (5-amino-2,3-dihydrophthalazine-1,4-dione) on a glassy carbon electrode. The detection limit (2 x background noise) was 4.3 x 10^-6 M. The variables affecting the electroluminescent detection of hydrogen peroxide in the enzymatic reaction were studied. A linear calibration range of 5-50 µg mL-1 glucose was achieved. The proposed system was applied to the determination of glucose in different types of fruit juice and human serum. A dialysis membrane was coupled to the flow system in order to avoid electrode fouling, giving a linear calibration range of 50-300 µg mL-1. Glucose solution was merged with glucose oxidase and the flow was stopped for a preset time. The generated H2O2 was injected into a stream of carbonate buffer of pH 10.6 which was merged with a stream of 50 µM luminol dissolved in the same buffer. The mixture was passed through a reaction coil and then to a 30 µL flow cell constructed from Plexiglas and equipped a vitreous C working electrode held at 1.9 V vs. Ag/AgCl reference electrode. A Pt electrode served as the counter electrode. The emitted light was measured by means of a photomultiplier tube connected to a conventional spectrophotometer. The system was used for the determination of glucose in human serum and fruit juice samples. The detection limit was 4.3 µM glucose. Calibration graphs were linear for the range 50-300 µg/ml. Recoveries were >92%.
Glucose Serum Human Fruit Chemiluminescence Electrode

"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

"Electrochemical Detection Of NADH And Dopamine In Flow Analysis Based On Tetraruthenated Porphyrin Modified Electrodes"
Anal. Chim. Acta 1996 Volume 329, Issue 1 Pages 91-96
L&uacute;cio Angnes, Carla M. N. Azevedo, Koiti Araki and Henrique E. Toma*

Abstract: A glassy carbon electrode modified with a molecular film of tetraruthenated cobalt-porphyrin complex was used in a FIA system for the amperometric determination of NADH and dopamine. The working electrode was maintained at 0.85 V (for NADH) or 0.9 V (for dopamine) vs. a Ag/AgCl reference electrode with a steel auxiliary electrode. The carrier stream was 0.05 M acetate buffer at pH 4.7 at a flow rate of 0.8 ml/min and the injection volume was 130 µL. Calibration graphs were linear from 2-8 µM and 0.2-0.8 µM NADH and dopamine, respectively; detection limits were at the ppb level.
Dopamine Nicotinamide adenine dinucleotide oxidized Amperometry Electrode Electrode

"The Determination Of Vanadium(V) In The Presence Of Vanadium(IV) Using 4-(2-pyridylazo)resorcinol In A Flow Injection Manifold"
Anal. Chim. Acta 1996 Volume 329, Issue 3 Pages 275-284
M. J. C. Taylor, G. D. Marshall, S. J. S. Williams, J. F. van Staden and C. Saling

Abstract: Process streams arising from flue-gas scrubbers, and containing V(V) and V(IV) were filtered (0.2 µm) and 100 µL injected into an aqueous carrier stream of 2 g/l CDTA and the solutions mixed in a 200 µL stirred chamber. After a known time delay, a 50 µL fraction was switched into a carrier stream of 5 mM CDTA/68 pM-4-(2-pyridylazo)resorcinol (PAR) in 100 mM KH2PO4 buffer of pH 5.3, mixed in a reaction coil (2.5 m) and the resultant V(V)-PAR complex detected at 550 nm. Calibration graphs were linear up to 5 mg/1 of V(V) a RSD (n = 10) of 0.03% for 0.1 g/l V(V). Interference from a range of cations including V(IV) was non-significant.
Vanadium(V) Industrial Spectrophotometry

"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

"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

"Determination Of Pharmaceutical Thiols By Liquid Chromatography With Electrochemical Detection: Use Of An Electrode With A Conductive Carbon Cement Matrix, Chemically Modified With Cobalt Phthalocyanine"
Anal. Chim. Acta 1996 Volume 332, Issue 2-3 Pages 249-255
Gabriella Favaro* and Mario Fiorani

Abstract: An electrode, prepared by doping conductive C cement with 5% cobalt phthalocyanine, was used in FIA and LC systems to detect the pharmaceutical thiols, captopril, thiopronine and penicillamine. FIA determinations were performed with phosphate buffer of pH 2 as carrier stream (1 ml/min), an injection volume of 20 µL and an applied potential of 0.6 V vs. Ag/AgCl (stainless steel counter electrode). The calibration curves were presented for 5-100 µM of each analyte. The dynamic linear range was up to ~20 µM. The detection limits were 76, 73 and 88 nM for captopril, thiopronine and penicillamine, respectively. LC determinations were performed on a 5 µm Bio-Sil C18 HL 90-5S column (15 cm x 4.6 mm i.d.) with 1 mM sodium 1-octanesulfonate in 0.01 M phosphate buffer/acetonitrile as mobile phase (1 ml/min) and gradient elution from 9:1 (held for 5 min) to 7:3 (held for 10 min) in 5 min. The working electrode was maintained at 0.6 V vs. Ag/AgCl and the injection volume was 20 µL. For thiopronine, penicillamine and captopril the retention times were 3.1, 5 and 11.3 min and the detection limits were 0.71, 1 and 2.5 µM, respectively.
Thiols Captopril Thiopronine Penicillamine Pharmaceutical LC Electrode

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

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

"Electroimmobilization Of Sulfite Oxidase Into A Polypyrrole Film And Its Utilization For Flow Amperometric Detection Of Sulfite"
Anal. Chim. Acta 1996 Volume 332, Issue 2-3 Pages 145-153
S. B. Adeloju*, J. N. Bariscib and G. G. Wallaceb

Abstract: Sulfite oxidase (SOD) was immobilized in polypyrrole film by galvanostatic polymerization. The quantity of immobilized SOD was dependent on the concentration in the electrolyte, the current density and the polymerization period. Typically polymer films were deposited on Pt or Au (both 1.5 mm diameter) or vitreous C (3 mm diameter) electrodes from 5 mL aqueous 0.5 M pyrrole containing 10 iu SOD with a current density of 0.5 mA/cm2 and a polymerization time of 5 min. The deposited films were characterized by a radiolabelling technique, cyclic voltammetry, resistometry, electrochemical quartz crystal microbalance, scanning electron microscopy and atomic force microscopy. A FIA system for determining sulfite is described using a thin-layer electrochemical detection cell equipped with a Pt working electrode coated with polypyrrole/SOD, a Ag/AgCl (3 M NaCl) reference electrode and the stainless-steel body as the auxiliary electrode. A linear response was obtained up to 200 mg/l sulfite with 0.5 M KCl in 0.1 M phosphate buffer as the carrier stream (0.5 ml/min) and an applied potential of -0.9 V.
Sulfite Amperometry Electrode Electrochemical analysis Electrode

"Paraquat Sensors Containing Membrane Components Of High Lipophilicities"
Anal. Chim. Acta 1997 Volume 338, Issue 1-2 Pages 89-96
Bahruddin Saad*, Marinah Mohd. Ariffin and Muhammad Idiris Saleh

Abstract: Membrane-type ISE for paraquat were prepared using PVC membranes containing octamethylcyclotetrasiloxane as the sensing substance, bis-(1-butylpentyl)decane-1,1-diyl diglutarate or tetra-n-undecyl-3,3',4,4'-benzophenone tetracarboxylate as the plasticizer and sodium tetrakis-[3,5-bis(trifluoromethyl)phenyl] borate or potassium tetrakis-(4-chlorophenyl)borate as additive. The optimum compositions for the membranes were 3.6% sensor substance, 63.5% plasticizer, 30% PVC and 3% additive. The ISE were fabricated by casting the PVC membranes onto Pt electrodes and the potentiometric response to paraquat was measured against a Ag/AgCl reference electrode. All the ISE exhibited a Nernstian response to paraquat with response times of ~20 s for paraquat concentration greater than 10 µM. The detection limit was 1 µM-paraquat. The ISE were used in a FIA system with Trizma buffer at pH 5.5 as the carrier stream (2.6 ml/min) and an injection volume of 50 µL. The mean recoveries of 10 µM-paraquat from well, river and lake waters were 96.3%, 94.7% and 93.9%, respectively. The sample throughput was 85/h.
Paraquat River Well Lake Potentiometry Electrode Electrode Sensor

"Buffer Composition Suitable For Determining Very Low Fluoride Concentrations Using A Fluoride Ion-selective Electrode And Its Application To The Continuous Analysis Of Rain Water"
Anal. Chim. Acta 1997 Volume 338, Issue 1-2 Pages 141-147
Hirokazu Hara*, and Chun-ching Huang

Abstract: Various buffers were evaluated for determining fluoride in rain water using a continuous-flow system. The most sensitive response was obtained with Sorensen's buffer, a mixture of glycine and HCl of pH 2.8. The continuous-flow system allowed a rain water stream (1 ml/min) to be merged with the buffer stream (0.1 ml/min). The flow was then passed through the detection cell equipped with a fluoride ISE and a double-junction Orion reference electrode. A linear response was obtained for up to 0.1 µM-fluoride and the detection limit was 10 nM. RSD were M and the recovery of 60 nM-fluoride from spiked rain water was 92%. The method was used to continuously monitor fluoride in rain.
Fluoride Rain Potentiometry Electrode

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

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

"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

"The Aluminum(III)-4-nitrocatechol System: Potentiometry, Voltammetry And Application To The Determination Of Reactive Al(III)"
Anal. Chim. Acta 1997 Volume 345, Issue 1-3 Pages 5-15
A. J. Downard, R. J. Lenihan, S. L. Simpson, B. O'Sullivan and K. J. Powell

Abstract: Four Al(III)-4-nitrocatechol (4ncat) complexes were studied by potentiometry and voltammetry from pH 3-11 and with 4ncat:Al(III) ratios of 1-4. A technique involving amperometric detection was described for determining Al(III) in environmental materials. The method was based on the quantitative formation of [Al(4ncat)3]3- at pH 9. The method was applied to aqueous extracts from soils. An extract (700 µL) was inserted into a carrier stream of acetate buffer of pH 5 at a flow rate of 0.98 ml/min then propelled through an oxine microcolumn (22 µl). The retained Al3+, Al(OH)2+, Al(OH)2+ and labile Al complexes (e.g. AlF2+, AlF2+) were subsequently eluted with 200 µL 0.02 M KOH to form an analyte plug of [Al(OH)4]-. The analyte plug was merged with a reagent stream prepared online from ammonium buffer of pH 9 at a flow rate of 0.36 ml/min and 1.6 mM 4ncat at a flow rate of 0.03 ml/min. Detection was carried out at a glassy carbon electrode at 0.3 V vs. SCE (Pt auxiliary electrode). Calibration graphs were linear from 0.4-8 µM-Al(III); the detection limit was 0.08 µM. RSD were 3.5% and 0.3% for 1 and 10 µM-Al(III), respectively.
Aluminum(III) Environmental Amperometry Electrode Voltammetry Potentiometry Sample preparation

"Combination Of Flow Injection With Capillary Electrophoresis. 1. The Basic System"
Anal. Chim. Acta 1997 Volume 346, Issue 2 Pages 135-143
Zhao-Lun Fang, Zhi-Song Liub and Qi Shen

Abstract: A flow-through conical reservoir was used to couple a flow injection (FI) system to a CZE system. The reservoir was attached to the outlet of the FI system. One end of the capillary column was positioned in the conical reservoir together with a grounded electrode. Samples were injected into the FI system and transported to the reservoir. Here, a portion of the sample plug was electrokinetically injected into the capillary. The same electrolyte was used as the carrier stream for the FI system and the running buffer. The system was demonstrated using benzoic acid and benzoic acid/magnolol mixtures as model analytes and 25 mM sodium tetraborate at pH 9.3 as the carrier/running buffer. Sample volumes of 40 µL were injected into the carrier stream (0.7 ml/min). The electrophoretic separations were performed on an uncoated capillary of 35 cm x 75 µm i.d. with an applied voltage of 12 kV (also injection voltage) and on-column UV detection at 224 or 254 nm. The precision of the coupled system was evaluated by repeated measurement of the peak heights and retention times for 200 mg/l benzoic acid. The RSD (n = 7) were 2.1% for peak heights and 0.4% for retention times. Similar measurements for a mixture of 150 mg/l benzoic acid and 140 mg/l magnolol yielded RSD (n = 7) of 2.3% for peak heights. The sampling frequency was 18/h.
Benzoate Magnolol Electrophoresis Spectrophotometry

"Prototype Of A Newly Developed Immunochemical Detection System For The Determination Of Pesticide Residues In Water"
Anal. Chim. Acta 1997 Volume 347, Issue 1-2 Pages 187-198
Petra M. Kr&auml;mer*, Bert A. Baumann and Peter G. Stoks

Abstract: Methods based on flow injection immunoaffinity analysis (FIIAA) are described for determining atrazine and diuron in water. The analyzes were performed on a prototype instrument consisting of an affinity column packed with protein A immobilized on polymethacrylate and a flow-through fluorimeter. The sequential experimental procedure was carried out by subjecting the affinity column to the following treatments; (i) incubating with anti-pesticide antibodies, (ii) rinsing, (iii) incubating with pesticide solution, (iv) rinsing, (v) incubating with peroxidase tracer for 3 min, (vi) rinsing and (vii) incubating with 3-hydroxyphenyl propionic acid/H2O2 substrate solution. The product of the enzyme reaction was detected at 415 nm (excitation at 320 nm). Between each determination the protein A affinity column was regenerated with 100 mM sodium citrate buffer. The linear range of the assays was 0.02-0.5 µg/l for both atrazine and diuron and the concentration producing 50% inhibition of the maximum response for atrazine was 0.1 µg/l. Diuron and isoproturon had no effect on the atrazine determination but simazine caused a decline in the atrazine signal. Recoveries for 0.02-0.5 µg/l atrazine were satisfactory.
Atrazine Diuron Environmental LC Immunoassay Fluorescence

"Simultaneous Amperometric And Potentiometric Detection Of Inorganic Anions In Flow Systems Using Platinum And Silver/silver Chloride Electrodes"
Anal. Chim. Acta 1997 Volume 350, Issue 1-2 Pages 1-6
Z. Chen and D. B. Hibbert*

Abstract: Platinum and silver/silver chloride electrodes were evaluated for electrochemical detection (amperometry and potentiometry, respectively) of inorganic anions in flow systems. In flow injection analysis, a linear response over three decades and detection limit of 1 x 10^-7 M for I- and NO-2 were obtained at an applied potential of +0.9 V (vs. Ag/AgCl) in 30 mM phosphate buffer at pH 3.0 as carrier. A silver/silver chloride electrode responded potentiometrically to halides and pseudo-halides in this buffer with a detection limit of 1 x 10^-5 M. The detector, which included both detection systems, was coupled with ion chromatography. Following separation by anion-exchange chromatography with 40 mM phosphate buffer at pH 4.5 as eluent, Cl-, Br-, I-, SCN-, and S2O2-3 were determined potentiometrically with a detection limit of 1 x 10^-5 M, and, simultaneously, NO-2, Br-, I-, and SCN- were determined amperometrically with a detection limit of 1 x 10^-6 M. Ioninteraction chromatography with an eluent of 20 mM phosphate at pH 5.0 containing 5 mM tetrabutylammonium hydroxide separated and detected Br-, NO-2 and SCN-.
Iodide Nitrite Chloride Bromide Thiocyanate ion Sulfite Potentiometry Amperometry Electrode Electrode

"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

"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

"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

"Ion Exchange Of Cationic Drugs At A Nafion-coated Electrode In Flow-through Analysis"
Anal. Chim. Acta 1991 Volume 249, Issue 2 Pages 489-494
Jianxun Zhou and Erkang Wang

Abstract: The selectivity of the electrode to such drugs was tested with promethazine by steady-state voltammetry and flow-through amperometric measurements. The best results were obtained with a low-concentration. Li buffer, e.g., 0.01 M as acetate, pH 4.0. The electrode was stable in a mobile phase containing 10% acetonitrile or 25% methanol for >24 h.
Drugs Promethazine Amperometry Electrode Ion exchange Voltammetry

"Periodate Determination By FIA With Chemiluminescence Emission Detection And Its Application To Ethylene Glycol [ethanediol]"
Talanta 1989 Volume 36, Issue 3 Pages 357-362
N. P. Evmiridis

Abstract: The method is based on measurement of the chemiluminescence generated by the oxidation of pyrogallol (I) by IO4-. A 40 µL sample is injected into a carrier stream of phosphate buffer solution of pH 8.0, which is then mixed with a reagent stream of 1 mM I - 1 mM hydroxylamine. The detection limit is 0.35 µg of IO4-, and the coefficient of variation is 3%. The method can be applied in the determination of ethanediol (II). II is treated with an excess of IO4- in buffer solution of pH 8.0, and residual IO4- is determined as before. The detection limit of II is 0.5 µmol. The sampling rate is 15 min-1.
Periodate 1,1-Ethanediol Chemiluminescence

"Mixed Reagents In Multi-component Flow Injection Analysis. Simultaneous Determination Of Iron And Copper In Blood Serum With Mixed Bathocuproinedisulfonate And Bathophenanthrolinedisulfonate Or Ferrozine"
Talanta 1989 Volume 36, Issue 4 Pages 463-467
V. Kub&aacute;, D. B. Gladilovich and L. Sommer, P. Popov

Abstract: Deproteinized serum (0.5 ml) was mixed with 0.1 mL of 0.1 M ascorbic acid, 0.1 mL of 3 M trichloroacetic acid and 0.3 mL of 0.33 M formate buffer (pH 3.5) and, after 15 min, the solution was centrifuged and a 0.4 mL portion of supernatant solution was diluted with 0.1 mL of water. A 20 µL portion of solution and 20 µL of reagent solution [0.6 mM bathocuproinedisulfonate (I) - 0.2 mM bathophenanthrolinedisulfonate or 2 mM I - 0.2 mM ferrozine] were synchronously injected into the carrier stream (1 mM HNO3) of the flow injection system. A PTFE reaction coil (27 cm x 0.6 mm) was used and the flow rate was 0.5 mL min-1. Spectra were recorded with a photodiode-array detector over the range 390 to 590 nm. A computer program, ORTHO, was used to evaluate results. The merging zones multi-component method was suitable for determination of 0.7 to 33 µM Fe(II) and 0.4 to 35 µM Cu(I), and for Cu-to-Fe ratios of 10:1 to 1:10. The coefficient of variation for Fe and Cu were, respectively, 3 and 6% in artificial mixtures and 2 and 5% in serum (n = 5 or 7).
Iron Copper Blood Serum Spectrophotometry

"Photometric And Amperometric Flow Injection Determination Of Triazolam And Clotiazepam"
Talanta 1989 Volume 36, Issue 7 Pages 761-765
R. M. Alonso*, R. M. Jimenez, A. Carvajal, J. Garcia and F. VicenteL. Hernandez

Abstract: For spectrophotometric determination, the carrier solution for triazolam (I) and clotiazepam (II) were aqueous 13% methanol and 0.1 M H2SO4, respectively, at flow rates of 5.0 and 5.4 mL min-1. Sample volume was 75 µL and delay coil dimensions were 37 cm x 0.58 mm i.d. for I and 35 cm x 0.58 mm i.d. for II. Calibration graphs were rectilinear for 3 to 55 µM-I at 228 nm and for 31 to 502 and 6 to 125 µM-II at 390 and 260 nm, respectively. For amperometric determination, the carrier solution for I and II were acetate buffer (pH 4.7) in 10% methanol and 0.1 M H2SO4, respectively, at flow rates of 4.5 and 6.4 mL min-1, sample volume were 106 and 75 µL for I and II, respectively, and delay coil dimensions were 50 cm x 0.58 mm i.d. for II and 16 cm x 0.58 mm i.d. for I. Detection was at -1.125 and -0.950 V for I and II, respectively, at a hanging-Hg-drop electrode vs. a SCE. Calibration graphs were rectilinear for 6 to 116 µM-I and 16 to 162 µM-II. Both methods were applied in the analysis of phamaceuticals.
Triazolam Clotiazepam Pharmaceutical Amperometry Electrode Spectrophotometry

"Evaluation Of The Analytical Use Of The Manganese-catalysed Malachite Green - Periodate Reaction By The Stopped-flow Technique"
Talanta 1989 Volume 36, Issue 11 Pages 1091-1094
M. C. Quintero, M. Silva and D. Perez-Bendito

Abstract: Sample solution contained 2 to 200 ng mL-1 of Mn(II) and 0.1 M NaIO4 (0.7 ml); the reagent solution consisted of 0.22 mM malachite green (2.5 ml) and acetate buffer (pH 3.8; 4 ml). The solution were diluted to volume and mixed, and the decrease in absorbance was measured at 615 nm. The effect on reaction rate of temp., concentration. of reagents and pH were investigated; the detection limit depended on the presence of the activator nitrilotriacetic acid. The calibration graphs were rectilinear from 0.1 to 15 and 0.5 to 100 ng mL-1 of Mn(II), and precision was 2% (n = 11). The proposed method was more sensitive and rapid than reference batch and flow injection methods.
Manganese

"Determination Of Ortho- And Pyrophosphates In Waters By Extraction Chromatography And Flow Injection Analysis"
Talanta 1990 Volume 37, Issue 10 Pages 889-894
B. Ya. Spivakov, T. A. Maryutina, L. K. Shpigun, V. M. Shkinev and Yu. A. Zolotov, E. Ruseva and I. Havezov

Abstract: A flow injection manifold is described which includes an extraction mini-column and a post-column spectrophotometric detector. The sum of ortho- and pyro-phosphate was determined in an aqueous sample by hydrolysis of the pyrophosphate at 50°C using inorganic pyrophosphatase, then the solution was mixed with a stream of 1 M HNO3 before passage through a column of Chromaton N-AW-HMDS modified with dioctyltin dichloride. The column was washed with water and Tris - HCl buffer for 1 min, and total orthophosphate was eluted with 0.5 M HCl. The orthophosphate was determined by mixing the solution with 1 M HNO3, pumping the stream through the column and elution with HCl as before, followed by monitoring the absorbance at 660 nm of the molybdenum blue produced in a reaction coil. For a sample volume of 6 ml, the calibration graph was rectilinear from 5 to 100 ng mL-1 of P, and the detection limit was 0.3 ng mL-1. The recovery of the ions was >96%. The method was used for the analysis of river water.
Phosphate Pyrophosphate River Spectrophotometry Sample preparation

"Spectrophotometric Determination Of Palladium With Sulfochlorophenolazorhodanine By Flow Injection"
Talanta 1990 Volume 37, Issue 3 Pages 329-336
Paul M. Shiundu, Peter D. Wentzell and Adrian P. Wade*

Abstract: A computer-controlled flow injection system (Betteridge et al., Anal. Chem., 1986, 58, 2258) with 70 µL injection loop, peristaltic pumping and a 30 µL 1-cm pathlength detection cell is used with diode-array detection at 488 nm for determination of Pd at pH 5. The sample injection medium was 1 mM HCl, the reagent stream contained the Na salt of the cited reagent at 0.94 mM buffered with pH 2 Universal buffer and 0.2 M NaOH and the carrier stream was aqueous solution The rectilinear calibration range was from 0.045 to 30 µg mL-1. Interference studies are reported for 19 metal ions.
Palladium Spectrophotometry

"Flow Injection Determination Of Phosphate With A Cadmium Ion-selective Electrode"
Talanta 1990 Volume 37, Issue 7 Pages 683-687
David E. Davey, Dennis E. Mulcahy and Gregory R. O'Connell

Abstract: A solution of K2HPO4 or KH2PO4 in 10 mM ammonium acetate buffer (pH 6.6 to 9.0) or 2 M acetate buffer (pH 3.6 to 5.4) was introduced into a reagent stream of aqueous Cd(NO3)2 resulting in the formation of Cd3(PO4)2. The reduction in free metal concentration. was determined by a cadmium-selective electrode. There was excellent response to PO43- and good selectivity over several common anions in solution buffered at pH 8.4. Major interference was caused by I- and moderate interference by Br- and SCN-. The sampling rate was 160 h-1, for standards containing 10 µM to 0.1 M PO43-, with a 0.1 mM Cd2+ reagent stream at a total flow-rate (carrier and reagent stream combined) of 8.4 mL min-1.
Phosphate Electrode

"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

"Simultaneous Determination Of Calcium And Magnesium By Using A Flow Injection System With Simultaneous Injection Of Two Sample Plugs And A Masking Agent Plug"
Talanta 1991 Volume 38, Issue 2 Pages 139-143
Takeshi Yamane* and Eiichi Goto,

Abstract: Two sample plugs were injected into a carrier stream of water, one plug was mixed with a plug of 10 mM EGTA in dilute aqueous NH3 to complex Ca. The carrier steam was merged with 0.05% of 3,3'-bis-[NN-bis(carboxymethyl)aminomethyl]-o-cresolphthalein in aqueous NH3 - NH4Cl buffer of pH 10.1 (0.5 mL min-1) then passed through a 1-m reaction coil before detection at 575 nm. One peak corresponds to Mg and the other to Mg plus Ca; Ca was determined by difference. Calibration graphs were rectilinear for at least 30 µg mL-1 of Ca or Mg. Phosphate, citrate and oxalate interfered at concentration. of ~0.5 mg mL-1. Analysis rate was 15 samples h-1. Results from the analysis of ground, river and seawater agreed well with those obtained by titration with EDTA.
Calcium Magnesium Ground River Sea

"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

"Determination Of Copper At Ng-levels By Inline Preconcentration And Flow Injection Analysis Coupled With Flame Atomic Absorption Spectrometry"
Talanta 1991 Volume 38, Issue 7 Pages 753-759
Rajesh Purohit and Surekha Devi*

Abstract: The synthesis and characterization of oxine (I) - formaldehyde (II) - resorcinol and I - II - hydroquinone chelating resins are described. Conditions were optimized for the pre-concentration. of Cu from binary and ternary mixtures also containing Co, Pb and/or Ni by batch extraction and by column chromatography, alone or in a flow injection system, with use of the resins. For batch pre-concentration, a pH of ~2.5 to 3 was optimal whereas in the flow injection method a broader pH range (~2 to 3.5) could be used. Separations of binary mixtures of Cu(II) with Ni(II) or Pb(II) at the µg mL-1 level did not show any cross contamination. A flow injection analytical procedure is described in which Cu was pre-concentrated by passage of the sample solution through a microcolumn (2 cm x 2 mm) containing the oxine resin. The carrier (2 mL min-1) was 0.2 M acetate or -phosphate buffer (pH 2 or 3, adjusted with HCl). The column was washed with buffer, and the chelated Cu was eluted by the injection of 50 µL of 0.5 M HCl, and was determined by flame AAS. The detection limit was 5 ng mL-1 with pre-concentration. from a 15 mL solution
Copper Chromatography Spectrophotometry Sample preparation

"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

"Determination Of Trace Amounts Of A Proteolytic Enzyme By FIA With A Stopped-flow And An Online Preconcentration Technique"
Talanta 1991 Volume 38, Issue 8 Pages 851-856
Thomas G&uuml;beli, Jaromir Rika* and Gary D. Christian,

Abstract: In the cited technique (diagram and details given) 5 mM N-succinyl-L-Ala-L-Ala-L-Pro-(4'-nitrophenylalaninamide) substrate was injected into a stream of-Tris-HCl buffer (pH 8.3) and this stream was merged with the enzyme sample solution The mixture was incubated at 40°C for 5 to 30 min during the stopped-flow period and the hydrolysis product, p-nitroaniline was concentrated on a column of 10 mg of C18 (40 µm), eluted with methanol, in counter-current mode, and detected at 400 nm. The limit of detection was 0.1 µU mL-1 of protease with a reaction time of 30 min and the coefficient of variation (n = 2 or 3) were from 2.8 to 17%.
Enzymes, proteolytic Spectrophotometry

"Determination Of Bromazepam By Coupling A Continuous Liquid - Liquid Extractor To An Atomic Absorption Spectrometer"
Talanta 1991 Volume 38, Issue 11 Pages 1241-1245
Ricardo E. Santelli, Mercedes Gallego and Miguel Valcarcel,

Abstract: Sample solution (3.2 mL min-1), containing 0.4 to 4.0 µ mL-1 of bromazepam (I) in aqueous 25% methanol, was merged with a carrier stream (0.7 mL min-1) of Cu - NaClO4 - acetate buffer (pH 4.75) and the ion-pair formed was extracted into isobutyl methyl ketone in a solvent segmenter. A portion of the extract was separated in a membrane phase separator and a 100 µL portion of the organic extract was carried by water for determination by AAS. The calibration graph was rectilinear over the cited range, the detection limit was 0.1 µg mL-1 and the coefficient of variation (n = 11) for 1 µg mL-1 of I was 1.7%. Sample throughput was 40 h-1. Recoveries from commercial pharmaceuticals were >98%.
Bromazepam Pharmaceutical Spectrophotometry Sample preparation

"Flow Injection Successive Determination Of Cysteine And Cystine In Pharmaceutical Preparations"
Talanta 1991 Volume 38, Issue 11 Pages 1235-1239
Tom&aacute;s P&eacute;rez-Ruiz, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Gabriel Lambertos

Abstract: Sample solution was merged with an aqueous hydroxylamine (1.7 mL min-1) stream, the mixture was merged with a stream of 50 µm-Hg(II) (3.0 mL min-1) at 30°C and 3.5 mM thiamine solution was added. The reaction mixture was then merged with 0.2 M phosphate buffer of pH 12 (1.7 mL min-1) and the fluorescence intensity of the resulting mixture was measured at 445 nm (excitation at 356 nm). The calibration graph was rectilinear for 10 to 100 µm-cysteine (I); the coefficient of variation (n = 11) was 1.1%. The determination of cystine (II) required previous reduction to I before analysis as above; coefficient of variation was 1.2%. The method was used to determine I and II in pharmaceuticals; results agreed well with expected values. Recoveries were 99.5 to 100.4 and 99.8 to 100.3% for I and II, respectively. Tolerance limits for interfering compounds are tabulated.
Cysteine Cystine Pharmaceutical Fluorescence

"Sequential Injection Technique For Automation Of Complex Analytical Procedures: Fluorimetric Assay Of Factor Thirteen"
Talanta 1993 Volume 40, Issue 1 Pages 81-87
Miguel Guzman, Cy Pollema, Jaromir Rika and Gary D. Christian,

Abstract: A non-segmented flow method is described for the automation of the fluorimetric assay of factor thirteen (I) by the sequential injection of 6 different solution zones. The procedure consisted of introduction of a bicine buffer - monodansyl cadaverine mixture, I sample and thrombin solution to activate the I, followed by addition of N,N-dimethylcasein and dithiothreitol to quench the I activation and initiate the formation of the fluorescing component. Then a sampling cycle was carried out by aspirating portions of the solution from the mixing chamber and propelling them to the detector. The system was washed with bicine buffer. The calibration graph was rectilinear in the range 0 to 50 µg mL-1 of I. The effects of the experimental variables are discussed in terms of optimization and validation of the system. Both quantitative and kinetic data were obtained.
Factor thirteen Fluorescence

"Spectrophotometric Determination Of Mixtures Of 2-, 3- And 4-hydroxybenzaldehydes By Flow Injection Analysis And UV/VIS Photodiode-array Detection"
Talanta 1994 Volume 41, Issue 1 Pages 59-66
Lars N&oslash;rgaard and Carsten Ridder*

Abstract: Samples (77 µL) containing 2-hydroxybenzaldehyde (I), 3-hydroxybenzaldehyde (II), 4-hydroxybenzaldehyde (III) or mixtures thereof in aqueous 10% ethanol and a modified Britton-Robinson buffer (pH 11.4) as the reagent solution were injected simultaneously into the flow injection apparatus (described) with a modified Britton-Robinson buffer (pH 4.5) as the carrier (0.375 ml/min) and a 8 µL flow cell. Spectrometric scanning (250-450 nm, every 2 nm) commenced 20 s after the injection and continued with a 1 s interval in 88 s. Each sample injection provided a data matrix consisting of 89 x 101 absorbances, containing both the acidic and basic characteristics of the sample injected. A least-squares algorithm was used to predict concentration in unknown samples. No assumptions about the qualitative mixture composition were necessary. Four data types were used in the least-squares modeling: unfolded raw data; acidic spectra; basic spectra; and first spectral derivative of the raw data. The prediction errors obtained for I-III were comparable to literature values. A graphic method was developed.
2-Hydroxybenzaldehyde 3-Hydroxybenzaldehyde 4-hydroxybenzaldehyde Spectroscopy Spectrophotometry

"Spectrophotometric Determination Of Rare-earth Elements By Flow Injection Analysis Based On Their Reaction With Xylenol Orange And Cetylpyridinium Bromide"
Talanta 1994 Volume 41, Issue 8 Pages 1251-1254
J. Havel, C. Moreno, A. Hrdlika and M. Valiente*

Abstract: Portions (30 µL) of 15 rare-earth elements in 0.1 M HNO3 were injected into a carrier stream of 0.06 mM Xylenol Orange and 0.6 mM cetylpyridinium bromide in 0.1 M acetate buffer of pH 5.5 at a flow rate of 1.8 ml/min, and reacted in a coil (30 cm x 0.8 mm i.d.) with detection at 600 nm. Calibration graphs were linear from 2.5-25 µM-metal with detection limits of 0.43 µg/ml or better. Method RSD was 0.88%. Applications of the method to the analysis of Pr(III) in HNO3 of pH 3 through a supported liquid membrane containing bis(2-ethylhexyl)phosphoric acid are discussed. A sampling frequency of 80-100 samples/h was achieved.
Metals, rare earth Praseodymium Spectrophotometry

"Fluorimetric Flow Injection Analysis Of Total Amounts Of Aldehydes In Auto Exhaust Gas And Thermal Degradation Emission Gas With Cyclohexane-1,3-dione"
Talanta 1996 Volume 43, Issue 6 Pages 859-865
Tadao Sakaia,*, Hideki Nagasawaa and Harumitsu Nishikawab

Abstract: Car exhaust gases and emission gases from the thermal degradation of polymers were collected by drawing through methanol. The methanol solution was injected into a carrier stream of water and the carrier stream merged with a reagent stream of 0.02% cyclohexane-1,3-dione in aqueous ammonium acetate/acetic acid buffer of pH 5 (0.75 ml/min). The resultant stream passed through a reaction coil (7 m x 0.5 mm i.d.) at 70°C, then through a cooling coil (2 m x 0.5 mm i.d.) at 10°C to a fluorescence detector for measurement of 452 nm (excitation at 376 nm). Calibration graphs were linear from 100-1000 ppb aldehydes with a detection limit of 30 ppb and RSD (n = 10) of 1.5% for 500 ppb formaldehyde. Sample frequency was 30 samples/h.
Aldehydes, total Exhaust Automobile Polymer Fluorescence

"Automatic Extraction-spectrophotometric Method For The Determination Of Ambroxol In Pharmaceutical Preparations"
Talanta 1996 Volume 43, Issue 7 Pages 1029-1034
Tom&aacute;s P&eacute;rez-Ruiza,*, Carmen Mart&iacute;nez-Lozanoa, Antonio Sanza and M. Teresa San Miguela

Abstract: Ambroxol was dissolved in water and injected into a carrier stream (0.8 ml/min) of 0.5 M acetate buffer of pH 4. The carrier stream merged with a reagent stream (0.8 ml/min) of 0.6 mM bromothymol blue and passed through a reaction coil (30 cm x 0.5 mm i.d.). The resulting stream merged with a reagent stream (2 ml/min) of 1,2-dichloroethane at a segmentor, the stream passed through an extraction coil (150 cm x 0.5 mm i.d.) to a phase separator. The absorbance of the organic phase was measured at 420 nm. The calibration graph was linear from 8-400 µM-ambroxol with a detection limit of 0.5 µM and RSD (n = 10) of 0.88% for 10 µM and 0.32% for 80 µM. The method was used to determine ambroxol in pharmaceuticals with recoveries of 97.2-102.6%. Excipients did not interfere.
Ambroxol Pharmaceutical Spectrophotometry Sample preparation

"Polarographic Study Of Acrolein And Its Determination By Flow Injection With Amperometric Detection At A Mercury Electrode"
Talanta 1996 Volume 43, Issue 7 Pages 1117-1124
Ignacio Naranjo Rodr&iacute;guez, Juan A. Mu&ntilde;oz Leyva and Jos&eacute; L. Hidalgo Hidalgo de Cisneros*

Abstract: The electrochemical behavior of acrolein (acrylaldehyde) was studied using direct current tast and differential pulse polarography. Three drop sizes of mercury at a dropping mercury electrode were also investigated. The studies were performed in Britton-Robinson buffer of pH 10 with a drop time of 1 s, a scan rate of 4 mV/s and a potential range of -1.1 to -1.5 V. A FIA method is proposed for the polarographic determination of acrylaldehyde with linear calibration graphs from 0.1-1 µM and 1-10 µM and a detection limit of 98 nM. The RSD (n = 11) was 2.9% for 0.2 µM. Acrylaldehyde was determined in seawater by injecting sample containing 0.25 mM EDTA into a carrier stream (1.8 ml/min) of Britton-Robinson buffer of pH 10 and polarographic detection at -1.4 V using a fresh hanging-Hg-drop electrode. Recoveries were 96-105%.
Acrolein Sea Polarography Amperometry Electrode

"Flow Injection Analysis Of L-lactic Acid Using An Enzyme-polyion Complex - Coated Electrode As The Detector"
Talanta 1996 Volume 43, Issue 10 Pages 1815-1820
Fumio Mizutania,*, Soichi Yabukia and Yoshiki Hirataa

Abstract: An enzyme electrode for L-lactic acid was fabricated by applying 0.04 M potassium phosphate buffer of pH 7 containing 10 µM-lactate oxidase and 10 mM poly-L-lysine and the same buffer containing 20 mM poly(4-styrene-sulfonate) successively on a polished glassy carbon electrode. The electrode was then used in a FIA system. Serum or sour milk was injected into a carrier stream (0.5 ml/min) of 0.1 M potassium phosphate buffer of pH 7.7 which passed to a flow-through cell comprising the enzyme electrode a Ag/AgCl reference electrode, a stainless-steel auxiliary electrode and a PTFE gasket. The potential was set at 1 V. Calibration graphs were linear up to 2.5 mM lactic acid with a determinable concentration range up to 6 mM. The detection limit was 20 µM and the RSD (n = 100) was 1.4% for 2 mM lactic acid.
l-Lactic acid Milk Blood Serum Electrode Electrode Electrode

"Determination Of L-phenylalanine In Serum By Flow Injection Analysis Using Immobilized Phenylalanine Dehydrogenase And Fluorimetric Detection"
Talanta 1996 Volume 44, Issue 1 Pages 131-134
Nobutoshi Kiba*, Akiko Itagaki and Motohisa Furusawa

Abstract: A flow injection system with an immobilized enzyme reactor is proposed for the determination of L-phenylalanine. Phenylalanine dehydrogenase from Rhodoccus sp. M4 was immobilized on tresylated poly (vinyl alcohol) beads (13 µm) and packed into a stainless-steel column (5 cm times 4 mm i.d.). Serum sample was deproteinized with tungstic acid and filtered through an ultrafiltration membrane. The sample solution (30 µl) was injected into the carrier stream (water). The NADH formed was detected at 465 nm (excitation at 340 nm). The calibration graph was linear for 0.9-600 µm L-phenylalanine; the detection limit was 0.3 µm, The sample throughout was 25 h-1 without carryover. The half-life period of the immobilized enzyme was 23 days. Serum (50 µL) was deproteinized by addition of 100 µL 10% sodium tungstate solution and 100 µL 0.06 M H2SO4 and filtration through an ultrafiltration membrane (mol. wt. cut off 10 000). A portion (30 µL) of the filtrate was injected into a carrier stream (0.2 ml/min) of water which merged with streams (0.2 ml/min) of 8 mM NAD+ and 2% glycerol in 0.2 M glycine buffer of pH 10 that had been pre-mixed in a mixing coil (100 cm x 0.5 mm i.d.). The flow passed through an enzyme column reactor (5 cm x 4 mm i.d.) at 20°C prepared by immobilization (details given) of phenylalanine dehydrogenase on poly(vinyl alcohol) beads (10 µm diameter). The NADH produced was detected fluorimetrically at 465 nm (excitation at 340 nm). The calibration graph was linear for 0.9-600 µM-L-phenylalanine and the detection limit was 0.3 µM. The within-day and day-to-day RSD were 0.88% and 1.2%, respectively. Recoveries were 97-103%. Results agreed with those obtained by LC.
l-Phenylalanine Blood Serum Sample preparation Fluorescence

"Spectrophotometric Determination Of A Nanomolar Amount Of Ascorbic Acid Using Its Catalytic Effect On Copper(II) Porphyrin Formation"
Talanta 1997 Volume 44, Issue 2 Pages 151-157
Masaaki Tabata*, and Hirofumi Morita

Abstract: A solution (120 µL) containing sample (ascorbic acid), 0.1 M NaNO2, 0.01 M acetate buffer of pH 5, 18 µM-5,10,15,20-tetrakis-(1-methylpyridinium-4-yl)porphyrin and 0.1 mM trans- 1,2-diaminocyclohexane-NNN'N'-tetra-acetic acid (DCTA) was injected into a stream (1.9 ml/min) of water which merged with a stream (1.9 ml/min) of water into which a solution (120 µL) of 0.4 mM Cu(II), 0.1 mM DCTA and 0.1 M NaNO2 in 0.01 M acetate buffer of pH 5 had been injected. The flow passed through a reactor (2 m x 5 mm i.d.) to a detector where the absorbance was measured at 550 nm. The calibration graph was linear for 0.12-0.5 µM-ascorbic acid and the RSD was 2.8% for 0.1 nM-ascorbic acid. No detection limit or recoveries are given. Reducing agents such as sugars and vitamin B compounds did not interfere seriously. The method was applied to urine, tea and blood.
Ascorbic acid Urine Blood Tea Spectrophotometry

"Application Of Sequential Injection Analysis To Anodic-stripping Voltammetry"
Talanta 1997 Volume 44, Issue 4 Pages 713-723
Ari Ivaskaa,* and Wladyslaw W. Kubiakb

Abstract: The system (diagram given) incorporated an eight-port value, PVC tubing (0.8 mm i.d.), holding and auxiliary coils (1.5 m), and a thin-layer detector cell with a vitreous-C working electrode, Ag/AgCl/3 M NaCl reference electrode and stainless-steel auxiliary electrode. Successive aspiration of stripping solution, deaerated 0.1 M HCl, sample, plating solution (10 µM-HgSO4 in 0.1 M HCl) and deaerated 0.1 M HCl was performed with the potential held at +0.5 V. Solutions stacked in the holding coil were pumped to the detector in reverse sequence. The generation of the Hg film on the electrode was followed by deposition of sample at -1 V, scanning to 0 V at 20 mV/s and measurement of the stripping current. Separation of Cd(II) and In(III) was achieved using 0.01 M EDTA in 2 M NaOH as stripping solution. Separation of Cd(II) and Tl(I) was achieved using 2 M ethylenediamine in 0.1 M HCl as stripping solution. Separation of Pb(II), Cd(II), Tl(I), Cu(II) and Sn(II) was achieved using a stripping solution giving 0.04 M EDTA, 0.8 M ethylenediamine in 0.8 M NH3 buffer of pH 9.8 at the detector. The calibration graph was linear for 30-175 nM-Pb in water and the detection limit was 25 nM. Sequential injection analysis (SIA) technique has been applied to anodic stripping voltammetry (ASV). The sample and reagent volumes can easily be controlled by SIA. The technique also allows plating of the mercury film online and therefore substantially reduces generation of mercury containing waste. Repeated sample passage through the detector was used during the deposition step to enhance the sensitivity. The way solution handling is done in SIA allows an easy and effective medium exchange procedure increasing the selectivity of the method. This has been demonstrated by changing the stripping medium and having different complexing agents in the stripping solution. The observed potential shifts of the stripping peaks could theoretically be explained in the cases where the complexation constants are known. Calibration and the standard addition methods are discussed and demonstrated by determining copper in tap water as a method of testing the procedure. (C) 1997 Elsevier Science B.V.
Lead(2+) Cadmium(2+) Thallium(I) Copper(II) Tin(II) Water Voltammetry Electrode

"Continuous-flow System For The Determination Of Trace Vanadium In Natural Waters Utilizing Inline Preconcentration/separation Coupled With Catalytic Photometric Detection"
Talanta 1998 Volume 45, Issue 3 Pages 583-589
Takeshi Yamane*, Yoshie Osada and Miho Suzuki

Abstract: A sensitive and rapid method is presented for the determination of vanadium at ng to sub ng/mL levels in natural waters, in which inline pre-concentration/separation is directly coupled with catalytic detection of vanadaium in a flow injection system. Vanadium was adsorbed on a small column packed with Sephadex G-25 gel and desorbed with a small volume of 0.010 M HCl. The catalytic action of vanadium on the oxidation of chromotropic acid by bromate in pH 3.8 buffered media was used in the sensitive determination of V. Effective pre-concentration/separation of trace vanadium can be achieved from Fe(III), Cu(II) and a large excess of NaCl in seawater sample. A linear calibration using a 5 m sample loop was obtained for 0-2.5 ng V/mL. The limit of detection was 0.02 ng/mL and the relative standard deviation was 1.2% for 1.0 ng V/mL (n = 5). This system is rapid and sensitive and can be readily applied to river water and coastal seawater samples.
Vanadium River Sea Spectrophotometry

"New Phase Separator For Extraction-spectrophotometric Determination Of Anionic Surfactants With Malachite Green By Flow Injection Analysis"
Talanta 1998 Volume 45, Issue 3 Pages 543-548
Tadao Sakaia,*, Hiromasa Haradaa, Xiaoqin Liua, Nobuo Uraa, Kenji Takeyoshib and Kunihiko Sugimotob

Abstract: A simple flow injection spectrophotometric method for the determination of anionic surfactants in river water was studied. A 3-channel flow system was assembled. The distilled water as a carrier and 5 x 10^-5 mol/L malachite green (MG) dissolved in 0.1 mol/L CH3COONa-CH3COOH buffer solution (pH 5) were delivered at 1.94 mL/min. The mixed solvent (toluene + methylisobutyl ketone = 1 + 1) was pumped at 0.78 mL/min. Other conditions were the extraction coil 0.5 mm i.d. x 3 m, the reaction temperature 20°C and the sample size 200 µL. The calibration graph was linear at 0.1-0.4 ppm and 626 nm. The detection limit (S/N = 3) was 18 ppb and a sample frequency of 20/h was attained. The relative standard deviation (n = 7) for 0.4 ppm standard Na dodecylsulfate solutions was 1.1%. A phase separator with a convenient connector was designed. This method was applied to the determination of anionic surfactants in river water.
Surfactants, anionic River Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Calcium Using Murexide As A Color Agent"
Talanta 1998 Volume 46, Issue 6 Pages 1245-1257
Kate Grudpana,*, Jaroon Jakmuneea, Yuthsak Vaneesorna, Surasak Wataneska, U Aye Maung, a and Ponlayuth Sooksamitib

Abstract: FI spectrophotometric determination of Ca using murexide was developed. The problem of the color of the dye fading and/or its complex in an alkaline medium in the batch method can be overcome by taking advantage of FIA. A Ca solution is injected into an ethylenediamine-ethylenediamine hydrochloride buffer (1 M, pH 11) which also serves as a masking agent, and is then merged with the aqueous murexide (0.005%, wt./v) and continuously monitored. Simple FIA manifolds, including an LED colorimeter detector hooked up to a PC-based data acquisition and evaluation system are described. Optimization of FIA systems was made. The proposed procedures were validated by using reference materials and comparing the results with the standard methods, and then applied to ores and drug samples.
Calcium Geological Pharmaceutical Spectrophotometry

"Micellar Systems In Flow Injection For The Spectrophotometric Determination Of Neodymium In Glasses"
Analyst 1989 Volume 114, Issue 7 Pages 849-851
Jos&eacute; Luis P&eacute;rez Pav&oacute;n, Bernardo Moreno Cordero, Jes&uacute;s Hern&aacute;ndez M&eacute;ndez and Jorge Cerd&aacute; Miralles

Abstract: Glass (~0.25 g) was dissolved as previously described (Anal. Abstr., 1988, 50, 8B222), the pH of the solution was adjusted to 2.7 and NaNO3 was added to a final concentration. of 0.4M. After dilution to 25 ml, a 143 µL portion of solution was injected into the carrier stream (2.2 mL min-1), viz, of aqueous 1.6 mM 1-(2-pyridylazo)-2-naphthol - Triton X-100 (150:1), buffered at pH 9.2 with 0.04 M HBO2 - NaBO2. A 50-cm reaction coil was used, and the absorbance was measured at 560 nm. Interference from heavy metals was removed by extracting their diethyldithiocarbamates into CHCl3 - ethyl acetate (1:1). The detection limit was 27 ppb and the calibration graph was rectilinear from 56 to 80 µM-Nd. Results agreed with those obtained by conventional and derivative spectrophotometriy.
Neodymium Commercial product Sample preparation Spectrophotometry

"Spectrophotometric Determination Of Periodate With Salicylaldehyde Amidinohydrazone Using Flow Injection. Determination Of Glycerol In Vegetable Oils"
Analyst 1989 Volume 114, Issue 8 Pages 989-990
Juan Jos&eacute; Berzas Nevado and Pablo Valiente Gonz&aacute;lez

Abstract: A 0.2 mL sample containing 50 ppm of IO4- was injected into a carrier stream of water (1 mL min-1) and then mixed with 0.06% salicylaldehyde amidinohydrazone solution followed by 0.25 M NH4Cl - NH3 buffer (pH 9.2) (both 1 mL min-1). The absorbance was measured at 490 nm; the calibration graph was rectilinear. Glycerol was determined by treatment with excess of IO4- and set aside for ~30 min before analysis as above. Oil was dissolved in CHCl3 before analysis. Recoveries from olive and sunflower oil were quantitative. The sampling rate was 20 h-1. Periodate has been determined using flow injection with spectrophotometric detection on the basis of the red color obtained when salicylaldehyde guanylhydrazone (SAG) and periodate were mixed in a basic medium. The carrier stream was de-mineralised water. The reagent stream was an aqueous SAG solution and another stream contained an ammonia buffer (pH 9.2) solution. The calibration graph was linear between 5 and 50 p.p.m. of periodate when the injection volume was 200 µL. The relative standard deviation (n= 10) was 1.0% and the detection limit, corresponding to a signal to noise ratio of 3, was 0.35 p.p.m. The proposed method was applied to the determination of glycerol in vegetable oils using the Malaprade reaction.
Periodate Glycerol Oil Oil Oil Spectrophotometry

"Spectrophotometric Determination Of Total Cyanide, Iron - Cyanide Complexes, Free Cyanide And Thiocyanate In Water By A Continuous-flow System"
Analyst 1989 Volume 114, Issue 8 Pages 959-963
ohannes C. L. Meeussen, Erwin J. M. Temminghoff, Meindert G. Keizer and Ivo Novozamsky

Abstract: The spectrophotometric method used is based on that of Nagashima (Anal. Abstr., 1979, 36, 1B81), except that 1,3-dimethylbarbituric acid is used instead of barbituric acid, and 0.1 M phthalate instead of 1 M phosphate buffer. Total cyanide plus SCN- is determined spectrophotometrically after UV irradiation and distillation with citric acid at pH 3.8; free CN- plus SCN- is determined without irradiation and distillation; and SCN- is determined after masking of CN- with formaldehyde. Iron - CN- complexes are determined as the difference between the first two measurements. The detection limit is 0.6 µg L-1 of CN-, and recovery of Fe - CN- complexes is quantitative. Interference from NO3- is minimized.
Cyanide, total Thiocyanate ion Iron(2+) hexacyanide Cyanide, free Environmental Spectrophotometry

"Investigation Of The Contribution Of Metal Ion Enhancement Of The Rate Of Hydrolysis Of Sodium Tetrahydroborate To Interferences In The Determination Of Arsenic(III) By Hydride-generation Atomic Absorption Spectrometry"
Analyst 1989 Volume 114, Issue 9 Pages 1159-1161
John Aggett and Glenn Boyes

Abstract: The rate of hydrolysis of NaBH4 in an acetate buffer (pH 5.0) is significantly increased in the presence of Ni(II) or Co(II), but that the rate of formation of AsH3 is still much faster than the rate of hydrolysis. In continuous-flow methods of determination of As(III) by hydride-generation AAS, the increased rate of hydrolysis may contribute to the interference by Co(II) and Ni(II), but in manual methods, the interference is more likely to be due to a competition between precipitation and hydride evolution.
Arsenic(3+) Spectrophotometry

"Oxygen Removal In Flow Injection Anodic-stripping Voltammetry"
Analyst 1989 Volume 114, Issue 10 Pages 1271-1273
Eddie Boon-Tat Tay, Soo-Beng Khoo and Siau-Gek Ang

Abstract: The method involves use a new flow cell (illustrated) and a six-way valve. A Hg-film electrode is formed by deposition on vitreous carbon, in the presence of O, at -1.0 V for 30 s, and the sample solution is then passed through the cell for deposition of metals at -0.8 V. After deposition, the sample solution is replaced by the stripping solution (0.1 M Na acetate buffer, pH 4.5), which is purged with N to remove O. The metals are determined by anodic-stripping voltammetry by scanning at 10 mV s-1 from -0.8 to 0 V. The method was applied in the determination of Cu, Pb and Cd in seawater. The corresponding limits of detection were 1.2, 0.8 and 0.75 nM with a flow rate of 3.1 mL min-1 and deposition for 3 min. The coefficient of variation were 5% for 5 nM and 2% for 0.5 µM.
Copper Cadmium Lead Sea Voltammetry Electrode

"Flow Injection With Anodic Polarographic Detection For The Determination Of Allopurinol In Pharmaceutical Formulations"
Analyst 1989 Volume 114, Issue 11 Pages 1449-1452
Tommaso R. I. Cataldi, Francesco Palmisano and Pier Giorgio Zambonin

Abstract: Powdered tablets (50 mg) were dissolved in 1 mM NaOH with sonication, and portions were injected into a stream (1 mL min-1) of 50 mM borate buffer (pH 9.2) for flow injection analysis, with use of a PAR model 174A polarographic analyzer., a dropping mercury electrode (0.5-s drop time) and detection at +150 mV vs. Ag - AgCl. The calibration graph was rectilinear for 300 µM, and the limit of detection was 1.8 µM. The within-run coefficient of variation (n = 10) was 3.1% for 28 µM. Mean recovery was 99.6% of the label claim. About 90 samples h-1 could be analyzed.
Allopurinol Pharmaceutical Electrode Polarography

"Simultaneous Determination Of Total Iron And Chromium(VI) In Waste Water Using A Flow Injection System Based On The Sandwich Technique"
Analyst 1989 Volume 114, Issue 11 Pages 1465-1468
Alberto N. Araujo, Jose Luis F. C. Lima, Antonio O. S. S. Rangel, Julian Alonso, Jordi Bartroli and Raquel Barber

Abstract: The 'sandwich technique' involves injection of sample solution between two different reagent solution by means of an eight-port injection valve. The sample was injected between 0.1 M H2SO4 - aqueous ~1% ethanolic 0.05% 1,5-diphenylcarbazide and aqueous 20% hydroxylammonium chloride - aqueous ~1% ethanolic 0.1% 1,10-phenanthroline - ammonium acetate buffer. Two peaks were obtained at 526 nm, corresponding to the concentration. of Cr(VI) and total Fe (hydroxylamine reduces Fe(III) to Fe(II)). The range of application was 0.2 to 10 ppm of either metal, with detection limits of 0.18 ppm of Fe and 0.16 ppm of Cr(VI). The method was applied to waste water, and results agreed with those obtained by batch analysis.
Iron Chromium(VI) Waste Spectrophotometry

"Flow Injection Procedure For The Determination Of Tertiary Amines In Water And Seawater Using Chemiluminescence Detection"
Analyst 1989 Volume 114, Issue 12 Pages 1659-1661
J. Steven Lancaster, Paul J. Worsfold and A. Lynes

Abstract: Sample was injected into a stream of borate buffer (pH 11.0), which merged first with 1 mM rhodamine B and then with 1.64 mM NaOCl (all at 1 mL min-1); detection of chemiluminescence was by a photomultiplier tube. The calibration graph for triethylamine was rectilinear for 0.2 mM in water and 0.1 mM in seawater. Coefficients of variation were generally 2% (n = 5). The method can also be used to determine trimethyl- and tripropyl-amine. Quenching of the chemiluminescence occurs in the presence of a 10-fold excess of diethylamine or ethylamine.
Trimethylamine Triethylamine Tripropylamine Amines, alkyl Environmental Sea Chemiluminescence

"Use Of Masking Agents In The Determination Of Lead In Tap Water By Flame Atomic Absorption Spectrometry With Flow Injection Preconcentration"
Analyst 1990 Volume 115, Issue 5 Pages 571-573
Stephen R. Bysouth, Julian F. Tyson and Peter B. Stockwell

Abstract: The selectivity of immobilized 8-hydroxyquinoline for lead is shown to be improved by the use of masking agents during pre-concentration, prior to determination by flame atomic absorption spectrometry. Interference by iron, copper, aluminum and zinc is suppressed by including triethanolamine, thiourea, fluoride, acetylacetone or cyanide in the buffer as masking agents. Species such as iron or copper can completely prevent the pre-concentration of lead. This is shown to be overcome by using a buffer consisting of 0.2 M boric acid, 2% triethanolamine, 2% thiourea and 2% acetylacetone, even when the interfering species is in a 200-fold excess over lead. Recoveries from tap water samples, to which various amounts of lead had been added, ranged from 94 to 108%. Results of analyzes of tap water samples using this method were in good agreement with those obtained by electrothermal atomic absorption spectrometry. A buffer consisting of 0.2 M H3BO3, 2% of triethanolamine, 2% of thiourea and 2% of acetylacetone was used in pre-concentration. of samples containing 50 ppm of Pb on a column of immobilized 8-hydroxyquinoline. Interferent ions at 200-fold excess can be tolerated but signal losses of 25% occur. Recoveries were from 94.9 to 107.7%. Results agreed with those from electrothermal AAS, losses in precision were overcome by careful flow-rate control.
Lead Water Spectrophotometry

"Interference Study On A Continuous-flow Determination System For Sulfate With A Lead-selective Electrode Detector And Its Application To Natural-water Analysis"
Analyst 1990 Volume 115, Issue 8 Pages 1077-1083
Hirokazu Hara and Shigetsugu Mori

Abstract: The previously described method (cf. Ibid., 1988, 113, 1817), in which SO42- is determined indirectly by reaction with Pb(NO3)2 and detection with a Pb-selective electrode, was further studied. The interference caused by HCO3-, Cl-, Ca, NO3- and PO43- was studied, and the composition of the reagent was optimized. Even in the presence of an acidic buffer, HCO3- caused positive interference. A concentration.-dependent interference by Cl- was interpreted in relation to the dynamic response of the electrode. The optimum reagent comprised 1 mM monochloroacetic acid - 10 mM NaClO4 in ethanol also containing 10 or 50 µM-Pb(NO3)2 for analysis of rain or river water, respectively.
Sulfate Rain River Electrode

"Determination Of L-ascorbic Acid In Fruit And Vegetable Juices By Flow Injection With Immobilised Ascorbate Oxidase"
Analyst 1990 Volume 115, Issue 10 Pages 1297-1299
Gillian M. Greenway and Peter Ongomo

Abstract: Ascorbate oxidase was immobilized on cyanogen bromide activated-Sepharose 4B and incorporated in a flow injection system with amperometric detection at a glassy carbon electrode at +0.6 V. On passage through the immobilized ascorbate oxidase a fraction of the L-ascorbic acid was converted into dehydroascorbic acid and the decrease in signal was measured. This could be directly related to the amount of L-ascorbic acid present. The calibration graph was linear over the range 0-400 ng mL-1 with a correlation coefficient of 0.9994. The detection limit (2s) in phosphate buffer (0.08 M, pH 5.5) was 4.0 ng mL-1. The relative standard deviation for a 200 ng mL-1 standard was 1.0% (n = 10) and the sampling throughput was 30 samples h-1. The method was used for the simple and rapid determination of L-ascorbic acid in fruit and vegetable juice.
l-Ascorbic acid Fruit Vegetable Amperometry Electrode

"Selective Determination Of Triton-type Non-ionic Surfactants By Online Clean-up And Flow Injection With Spectrophotometric Detection"
Analyst 1990 Volume 115, Issue 5 Pages 609-612
M. Eugenia Le&oacute;n-Gonz&aacute;lez, M. Jes&uacute;s Santos-Delgado and Luis M. Polo-D&iacute;ez

Abstract: An aqueous sample (100 µL) containing Triton-type surfactants was passed through either an ion-exchange column at 0.6 mL min-1 (Amberlite IRA-904 cation exchange or IR-120 anion exchange) to remove interfering ionic surfactants, or an Amberlite XAD-4 adsorption resin followed by elution of I with 1 mL of ethanol. Alizarin fluorine blue was released into the acetate buffer stream (pH 4.5, 1.2 mL min-1) to mix with the column outflow before spectrophotometric determination at 432 nm. Beer's law was obeyed from 0.2 to 12.0 mg L-1 and 2.0 to 120 µg L-1 of such compounds. The method was compared with the picrate batch and picrate flow injection methods.
Surfactants, non ionic Triton X-100 Ion exchange Spectrophotometry

"Simultaneous Determination Of Trace Amounts Of Iron(III) And Titanium(IV) By Flow Injection With Spectrophotometric Detection"
Analyst 1990 Volume 115, Issue 4 Pages 431-434
Shoji Kozuka, Kenichi Saito, Koichi Oguma and Rokuro Kuroda

Abstract: Powdered silicate rock sample was fused with Li2CO3 - H3BO3 (1:1) and the melt was dissolved in 1 M HCl. The solution was injected simultaneously into a carrier stream of 1 M HCl at 2 mL min-1 at two inlet points separated by a Ag reductor column that reduced Fe(III) to Fe(II). The stream was merged with a reagent solution of 0.5% disodium 1,2-dihydroxybenzene-3,5-disulfonate in acetate buffer, pH 4.9, at 2.0 mL min-1 and monitored at 430 nm. The absorption of the first peak represented the total Fe(III) and Ti(IV) content and that of the second, the Ti(IV) concentration. The method was applied in the analysis of reference materials, the results obtained agreed closely with certified values with mean coefficient of variation of 1.0 and 0.87% for Fe and Ti respectively. There was no interference.
Iron(III) Titanium(IV) Silicate Spectrophotometry

"Spectrophotometric Or Coulometric Determination Of Nitrate With An Electrochemical Reductor Using Flow Injection"
Analyst 1990 Volume 115, Issue 4 Pages 425-430
Ryuji Nakata, Minoru Terashita, Akihiko Nitta and Keiko Ishikawa

Abstract: The flow-through column electrode, with Cu and Cd deposited on glassy carbon beads, as described previously by Nakata (Fresenius Z. Anal. Chem., 1984, 317, 115) was used. The NO3- was reduced to NO2- at -0.85 to -1.05 V vs Ag - AgCl in NH4OH buffer, pH 10.0. The NO2- was determined by conventional colorimetry with a detection limit of 0.7 µm and a coefficient of variation (n = 10) of 0.52% for 10 µm. By using a column electrode with Ag deposited on the grains, as an O2 scrubber at -0.8 V, before the Cu - Cd electrode, the NO3-1 could be determined coulometrically. The limit of detection was 2 µm with coefficient of variation (n = 10) of 1.9% for 50 µm and 3.3% for 10 µm. The method was applied in the analysis of waters, the results obtained were in close agreement with those obtained by ion chromatography.
Nitrate Coulometry Electrode Electrode Spectrophotometry

"Determination Of Aluminum In Kaolins By Flow Injection"
Analyst 1991 Volume 116, Issue 2 Pages 191-194
Anuchit Prownpuntu and Umaporn Titapiwatanakun

Abstract: Sample (0.2 g) was fused with 5 g of NaOH for 5 min, and the melt was extracted with water, the ppt. was dissolved in 6 M HCl, and the solution was diluted to 250 mL. A portion (10 ml) was made alkaline with aqueous 3 M NH3 until a ppt. appeared, 5 M acetic acid was added to dissolve the ppt., and the solution was diluted to 100 mL. An aliquot (75 µL) was injected into a stream (5 mL min-1) of 0.01% alizarin red S in ammonium acetate buffer (pH 4.5), the mixture was passed though a 50-cm reaction coil, and the absorbance was measured at 510 nm. The calibration graph was rectilinear for 25 ppm of Al, and the limits of detection and determination were 0.8 and 2 ppm, respectively. Recovery was quantitative. Results for several kaolins showed good agreement with those of an official method.
Aluminum Ceramic Sample preparation Spectrophotometry Sample preparation

"Determination Of Creatine Kinase Activity Using A Co-immobilized Auxiliary Enzyme Reactor Coupled Online With A Flow Injection System"
Analyst 1991 Volume 116, Issue 2 Pages 167-169
J. M. Fern&aacute;ndez-Romero and M. D. Luque de Castro

Abstract: Two flow injection methods (based on spectrophotometric and spectrofluorimetric detection) were developed for the determination of over-all creatine kinase activity. Despite the complexity of the reactions involved (both include three enzyme-catalyzed steps), the manifold is very simple because the two auxiliary enzymes which catalyse the two-step indicator reaction are co-immobilized on controlled-pore glass. The features of the proposed methods (calibration ranges between 0.1 and 2.0 and 0.01 and 1.0 U l-1, relative standard deviation 0.93 and 0.53% for the spectrophotometric and spectrofluorimetric methods, respectively) allow the successful determination of the analyte activity in serum samples (recoveries better than 95-105% for both methods). In the flow injection method described, a sample of serum is injected into a stream of 100 mM Tris - acetate buffer (pH 7.00) and mixed with the reagent stream containing 20 mM Mg acetate, 1 mM EDTA, 10 µM-p'p5-di(adenosine-5')pentaphosphate, 1 or 0.5 mM AMP, 10 mM N-acetyl-L-cysteine, 2 or 1.5 mM ADP, 15 mM creatine phoshate, 1.5 mM D-glucose and 1.5 or 2 mM NADP in the same buffer. The mixture was passed through a reaction coil and an enzymatic reactor containing hexokinase and glucose-6-phosphate dehydrogenase immobilized on controlled pore glass (cf. Masoom and Townshend, Anal. Chim. Acta., 1984, 166, 111). Detection was by spectrophotometry or fluorimetry (where two concentration. are given, they refer to the two methods, respectively). Calibration graphs were rectilinear for 0.1 to 2 and 0.01 to 1 iu l-1, respectively, and coefficient of variation were 1% (n = 11). Recoveries were 95 to 105%.
Enzyme, creatine kinase Blood Serum Fluorescence

"Use Of Ion-selective Electrodes In Kinetic Flow Injection: Determination Of Phenolic And Hydrazino Drugs With 1-fluoro-2,4-dinitrobenzene Using A Fluoride-selective Electrode"
Analyst 1991 Volume 116, Issue 3 Pages 233-237
John C. Apostolakis, Constantinos A. Georgiou and Michael A. Koupparis

Abstract: A flow injection (FI) kinetic potentiometric method for the determination of phenolic (acetaminophen and isoxsuprine) and hydrazino (isoniazid) drugs is described. This work shows the usefulness of ion-selective electrodes as detectors in FI systems, not only for direct ion determination but also in routine kinetic analysis. The method is based on the reaction of 1-fluoro-2,4-dinitrobenzene (FDNB) with the analytes in a weakly alkaline medium, which proceeds through the liberation of fluoride from the reagent. The slow reactions with phenols are catalyzed by micelles of cetyltrimethylammonium bromide. The reaction rate is monitored with a fluoride-selective electrode in a wall-jet configuration and is used to construct a calibration graph of antilog(delta E/S)-1 versus c (where E = potential, s = slope of the electrode and c = concentration), using the fixed-time approach. The response time and the long-term stability of the electrode were found to be adequate for such kinetic determinations. The proposed method overcomes problems associated with end-point spectrophotometric methods using FDNB and allows measurements in highly colored or turbid solutions. The optimized method has a linear concentration range of 1 x 10^-4-50 x 10^-4 mol L-1, a measurement throughput of 20 or 40 per hour and the precision ranges from 1.8 to 3.6% relative standard deviation (n = 3). Results obtained for commercial pharmaceutical formulations compare favourably with those given by reference methods. In the flow injection method described, sample solution is injected into water (3 mL min-1), which is mixed with 4.3 mM 1-fluoro-2,4-dinitrobenzene in acidified aqueous ethanol - acetone (0.8 mL min-1) and 13 or 15 mM NaOH without or containing 0.5 mM hexadecyltrimethylammonium bromide (for hydrazino and phenolic compounds, respectively). After passage through a 100-cm reaction coil, total I and pH adjustment buffer (pH 5.5; 1.2 mL min-1) was added, and after passage through a 50-cm reaction coil, F- was detected with a selective electrode. Paracetamol and isoxsuprine were determined as phenolic drugs and isoniazid as a hydrazino drug. Calibration graphs were rectilinear for 0.1 to 5 mM, and coefficient of variation were 1.8 to 3.6% (n = 3). The sampling rate was 20 or 40 h-1. Results for pharmaceutical formulations agreed with reference methods.
Hydrazine Phenols Drugs Pharmaceutical Electrode Potentiometry Spectrophotometry

"High-pressure Flow Injection Assembly. Indirect Determination Of Glycine By Atomic Absorption Spectrometry"
Analyst 1991 Volume 116, Issue 3 Pages 327-329
J. Martinez Calatayud and J. V. Garcia Mateo

Abstract: A procedure for the determination of glycine is described. The method is based on the reaction of the analyte with finely powdered, solid copper(II) carbonate in a continuous-flow assembly. The optimum experimental conditions of pH, temperature, sample volume, flow-rate, column length and internal diameter, and the linear range of calibration, were studied. Interference from foreign substances that accompany this amino acid in pharmaceutical formulations was studied, and the method was applied to the determination of glycine. Sample solution (adjusted to pH 9.5) was injected into a carrier stream of CO32- - HCO3- buffer solution (pH 9.5), and this was passed through a packed-bed reactor (5 mm x 0.9 mm) containing solid CuCO3.Cu(OH)2.10H2O. The stream, containing the Cu - glycine complex, was passed to an AAS spectrometer for determination of Cu at 324.8 nm. The effects of pH, temperature, sample volume, flow-rate and column dimensions were investigated. The coefficient of variation was 1.9% for 50 ppm. The sampling rate was 40 h-1. The method was applied in the analysis of pharmaceuticals.
Glycine Pharmaceutical Spectrophotometry

"Solvent Extraction Of Trace Amounts Of Fluoride Prior To, Mainly, Spectrometry - A Review: Recent Advances In The Alizarin Fluorine Blue Approach"
Analyst 1991 Volume 116, Issue 4 Pages 379-385
Marie M. Ferris and Michael A. Leonard

Abstract: The Alizarin fluorine blue - La method of Johnson and Leonard (J. Pharm. Pharmacol., 1961, 13, 164T) was modified. Water (0.5 l) was mixed with 2 mL of acetate buffer solution (pH 4.5), 10 mL of 0.5 mM Alizarin fluorine blue, 60 mL of acetone, and immediately after the addition of 10 mL of 1.75 M lanthanum nitrate, with 96 mL of 0.2 M diphenylguanidine in isobutyl alcohol with shaking every 15 min for 30 s over a 4-h period. The organic phase was separated, the extract and ethanolic washings were diluted to 25 mL with ethanol and, with use of the standard additions method, the absorbance of the solution was measured at 580 nm vs. a reagent blank. The calibration graph was rectilinear up to 1 µg of F-, with a detection limit of 40 ng L-1 and a coefficient of variation of 0.6% for 4 µg of F-. The method may act as a check on results by ion-chromatographic methods at low levels of F- or as a basis for a flow injection method.
Fluoride Spectrophotometry Sample preparation

"Studies On The Application Of Photochemical Reactions In A Flow Injection System. 1. Determination Of Trace Amounts Of Nitrite, Based On Its Inhibitory Effect On The Photochemical Reaction Between Iodine And Ethylenediaminetetra-acetic Acid"
Analyst 1991 Volume 116, Issue 5 Pages 497-499
Ren-Min Liu and Dao-Jie Liu

Abstract: Natural water samples, 0.01 M ethanolic iodine solution, 0.01 M NaH2EDTA solution and pH buffer solution (0.1 M sodium acetate - 0.1 M acetic acid adjusted with 0.1 M NaOH) were pumped into photochemical reactors (diagram given) and the reactants were injected into another channel of buffer solution Residual iodine was determined in the flow-through amperometric detector at 100 mV vs. SCE. Calibration graphs were rectilinear from 0.1 to 4 µM-nitrite. Coefficient of variation for tap, rain, well and lake water were 0.91, 0.84, 0.93 and 0.87%, respectively. Recoveries were 91%. Tolerance limits of foreign ions are tabulated.
Nitrite Environmental Amperometry

"Shipboard Flow Injection Method For The Determination Of Manganese In Seawater Using In-valve Preconcentration And Catalytic Spectrophotometric Detection"
Analyst 1991 Volume 116, Issue 7 Pages 707-710
I. Ya. Kolotyrkina, L. K. Shpigun, Yury A. Zolotov and G. I. Tsysin

Abstract: Sample was applied to a micro-column (1 cm x 2.5 mm) of DETATA fibrous sorbent (H+ form; cf. Tsysin et al., Zh. Neorg. Khim., 1990, 34, 960) and the Mn adsorbed was eluted with 0.5 M HCl or HNO3. The eluate was mixed with 10 mM KIO4 in phosphate buffer solution and NN-diethylaniline in dilute HCl amd the increase in absorbance at 470 nm was recorded. Preconcentration times of 10 s to 10 min allowed determination of 20 µg L-1 to 10 ng L-1 of Mn. The coefficient of variation were 5 to 8% and a sampling rate of 15 h-1 was achieved. Recoveries of 50 ng L-1 to 10 µg L-1 of Mn were 97 to 118%. The method was applied to the direct shipboard measurement of Mn in deep seawater samples.
Manganese Sea Spectrophotometry

"Spectrophotometric Flow Injection Procedure For The Online Monitoring Of Sulfite In High-ionic-strength Brine"
Analyst 1991 Volume 116, Issue 7 Pages 701-705
Paul MacLaurin, Paul J. Worsfold, Alan Townshend, Neil W. Barnett and Michael Crane

Abstract: The effects of pH, temperature and KCl concentration. on the determination of SO32- in KCl brines by a previous method (cf. Anal. Chim. Acta., 1990, 238, 171) was investigated (details given). A modified online procedure is described, in which a stream containing brine (0.5 mL min-1), water (1.6 mL min-1) and disodium tetraborate - NaOH buffer solution (pH 9.9; 1.6 mL min-1) was mixed with water (1.6 mL min-1) containing a plug (20 µL) of 2.5 mM 2,2'-dinitro-5,5'-dithiodibenzoic acid and subsequent detection of the reaction stream at 500 nm. The calibration graph was rectilinear from 3 to 100 mg L-1 of SO32- with a coefficient of variation (n = 168) of 2.1%. Results were in good agreement with those obtained by an offline iodimetric procedure.
Sulfite Environmental Spectrophotometry

"Determination Of Cobalt In Two Glasses By Atomic Absorption Spectrometry After Flow Injection Ion-exchange Preconcentration"
Analyst 1991 Volume 116, Issue 11 Pages 1141-1144
M. C. Vald&eacute;s-Hevia y Temprano, J. P&eacute;rez Paraj&oacute;n, M. E. D&iacute;az Garc&iacute;a and A. Sanz-Medel

Abstract: Ground glass (0.5 g) was digested with concentrated HNO3 - concentrated HCl04 - HF (details given) and the digest was treated with HCl, boric acid, NaOH and sodium citrate. After dilution with 0.1 M ammonium acetate - HCl buffer solution of pH 2.7 (buffer A), a 1 mL portion of the solution was injected into a carrier stream (0.5 mL min-1) of buffer A and passed through a reaction coil (3 ml). The mixture was merged with a second carrier stream (2.5 mL min-1) of 1 M NH3 - NH4Cl buffer solution of pH 8.5 and passed sequentially through a reaction coil (5 m) and a minicolumn (10 cm x 3 mm) loaded with Chelex-100. After 5 to 6 min, 200 µL of 5 M HNO3 was injected into the system to elute the Co directly into the nebulizer of the spectrometer. A schematic diagram of the flow manifold is given; operating conditions are tabulated. The calibration graph was rectilinear for 1.2 µg mL-1 of Co; the detection limit was 20 ng mL-1. For 0.5 µg mL-1 of Co, the coefficient of variation (n = 10) was 1.5%. The detection limit was 4-fold better than that obtained by direct aspiration without pre-concentration.
Cobalt Commercial product Sample preparation Ion exchange Spectrophotometry

"Kinetic Study And Analytical Applications Of The Micellar Catalysed Reactions Of 1-fluoro-2,4-dinitrobenzene With Thiols Using A Fluoride-selective Electrode"
Analyst 1993 Volume 118, Issue 8 Pages 1001-1006
Athanasios M. Gerakis and Michael A. Koupparis

Abstract: The reaction between a thiol and 1-fluoro-2,4-dinitrobenzene (I) in the presence of a surfactant and NaF was studied kinetically by using an Orion model 96-09 fluoride electrode for potentiometric measurement in various buffered media. Optimum conditions for the determination of, e.g., mercaptoacetic acid, benzenethiol or thiosalicylic acid comprised 2 mM hexadecylpyridinium chloride, 0.01 M Tris buffer of pH 7.5, initial I concentration. 0.86 mM, temperature 25°C, and fixed-time measurement at 11 s. Rectilinear response was obtained for, e.g., 10^-250 or 5-75 µM-benzenethiol or -thiosalicylic acid, respectively. The method was used for the determination of mercaptoacetic acid in hair-waving and depilatory preparations. A manifold for flow injection potentiometric determination of thiols is also described.
Mercaptoacetic acid Benzenethiol Thiosalicylic acid Commercial product Electrode Potentiometry

"Photochemical Spectrophotometric Determination Of Riboflavine And Riboflavine 5'-phosphate By Manual And Flow Injection Methods"
Analyst 1994 Volume 119, Issue 6 Pages 1199-1203
Tom&aacute;s Perez-Ruiz, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Otilia Val

Abstract: For the manual analysis, 0.2 M phosphate buffer of pH 7.2 was mixed with 3% Triton X-100, 1 mM MnSO4 and 16 mM dianisidine. Sample solution was added to the mixture before dilution with water. The solution was irradiated at 25°C and the absorbance at 460 nm was recorded as a function of the irradiation time. Calibration graphs were linear from 0.1-5 µM-riboflavine (I) and -riboflavine 5'-phosphate (II) with an RSD of 0.68%. For FIA, three reagent streams, viz, 2 mM dianisidine containing 0.45% Triton X-100 (0.7 ml/min), 0.1 M phosphate buffer of pH 7.2 (0.7 ml/min) and 0.1 mM MnSO4 (0.7 ml/min), were mixed. Sample solution was injected into the mixed reagent stream (2.1 ml/min) and transported to a reaction coil (100 cm x 0.5 mm i.d). The flow was stopped, the solution irradiated for 60 s and the absorbance at 460 nm was measured. A diagram of the manifold used is given. Calibration graphs were linear from 1-10 µM-I and -II; corresponding RSD were 1.3 and 1.1%. The throughput was 40 samples/h. Recoveries were quantitative for both methods. The methods were applied to multivitamin preparations and fortified bread.
Food Pharmaceutical Spectrophotometry

"Use Of The Sequential Injection Technique To Determine The Concentrations And Stoichiometries Of Trimeprazine And Perphenazine Complexed With Palladium(II) In Hydrochloric Acid"
Analyst 1995 Volume 120, Issue 2 Pages 561-563
Salah M. Sultan, Fakhr Eldin O. Suliman and Bahruddin B. Saad

Abstract: A method for determining trimeprazine (I) and perphenazine (II) is described. The determination was performed by first pumping the carrier solution (HCl buffered to pH 4.7 or 4.85 for determination of I and II, respectively) for 25 s. Then 176.4 µL of Pd(II) [5 or 2.5 mM for I and II, respectively) and 176.4 µL drug solution were sequentially aspirated into a holding coil (100 cm x 0.8 mm i.d.). By means of flow reversal (29.4 µL/s), the solutions were propelled through a reaction coil (40 cm x 0.8 mm i.d.) and the absorbance was measured at 515 and 560 nm for I and II, respectively. A diagram of the manifold used is given. The calibration graphs were linear from 50-400 and from 50-500 ppm of I and II, respectively. The method was applied to the determination of I and II in synthetic samples containing some compounds usually added to pharmaceutical preparations. The recoveries were quantitative. The method was also used to determine the reaction stoichiometry.
Perphenazine Trimeprazine Pharmaceutical Spectrophotometry

"Selective Spectrophotometric Determination Of Cobalt(II) Using 2,2'-dipyridyl-2-pyridylhydrazone And A Flow Injection Manifold"
Analyst 1995 Volume 120, Issue 5 Pages 1593-1598
Demetrius G. Themelis, George A. Zachariadis and John A. Stratis

Abstract: Sample (100 µL) was injected into a carrier stream (2.6 ml/min) of buffer solution of pH 7.24 (prepared from 0.4 M H3PO4/0.4 M acetic acid/0.4 M H3BO3/0.2 M NaOH) and merged with a reagent stream (0.9 ml/min) of 0.8 mM 2,2'-dipyridyl-2-pyridylhydrazone in aqueous 40% ethanol. The mixture passed through a reaction coil (60 cm x 0.5 mm i.d.) before merging with a second reagent stream (0.4 ml/min) of 1.5 M HCl. The resulting mixture then passed through a second reaction coil (12 cm x 0.5 mm i.d.) after which the absorbance was measured at 500 nm (ε = 42 000 l/mol/cm). A diagram of the manifold used is given. The calibration graph was linear from 0-12 mg/l of Co, the detection limit was 0.017 mg/l and the RSD (n = 5) was 0.4%. The throughput was 90 samples/h. The method was used to determine Co in cyanocobalamin (vitamin B12) after digestion with HNO3/HCl (details given). Recoveries were 98.5-102.7%.
Cobalt(II) B12 Sample preparation Spectrophotometry

"Simultaneous Assay Of Nitrite, Nitrate And Chloride In Meat Products By A Flow Injection Method"
Analyst 1996 Volume 121, Issue 10 Pages 1393-1396
I. M. P. L. V. O. Ferreira, J. L. F. C. Lima, M. C. B. S. M. Montenegro, R. P&eacute;rez Olmos and A. Rios

Abstract: Sample was homogenized and extracted with hot water and the extract was purified and filtered. A portion (100 µL) of the filtrate was injected into a carrier stream (2.9 ml/min) of 50 mM Na2SO4/0.02 mM NaCl of a flow injection manifold (schematic shown). Chloride (I) was determined potentiometrically a tubular ISE (cf. Ferreira et al., Fresenius' J. Anal. Chem., 1993, 374, 314). The carrier was mixed with a buffer stream (0.5 ml/min) of NH4Cl/sodium tetraborate/Na2EDTA and split into two. One stream passed through a Cd/Cu column to reduce nitrate (II) to nitrite (III). The two streams subsequently passed through a confluence point and were mixed a reagent stream (1 ml/min) of acidified sulfanilamide/N-(1-naphthyl)ethylenediamine dihydrochloride and the absorbance was measured (wavelength not given). As each channel had a different residence time, two peaks were obtained, one for nitrite III and one for total N: II was measured by difference. The calibration graphs were linear from 0.01-0.1 M I, up to 104 ppm II and from 0.03-0.2 ppm III. RSD (n = 10) were 2.5, 0.7 and 1.1%, respectively, for I, II and III.
Chloride Nitrate Nitrite Meat Meat Potentiometry Electrode Electrode

"Multicomponent Analysis By Flow Injection Using A Partial Least-squares Calibration Method. Simultaneous Spectrophotometric Determination Of Iron, Cobalt And Nickel At Sub-ppm Levels"
Analyst 1996 Volume 121, Issue 11 Pages 1609-1612
Carlos Moreno, Manuel P. M&aacute;nuel-Vez, Inmaculada G&oacute;mez and Manuel Garc&iacute;a-Vargas

Abstract: Sample (136 µL) was injected into a reagent stream (1 ml/min) of 0.02% 2,2'-di-pyridyl ketone picolinoylhydrazone/0.05% ascorbic acid in 0.02 M acetate buffer of pH 4.9 in a flow injection manifold (schematic shown). The mixture was passed through a 130 cm coil and the absorbance was recorded spectrophotometrically at 367, 410 and 385 nm, respectively, for Fe, Co and Ni with corresponding epsilon of 6640, 3890 and 5170. A partial least-squares calibration method was applied to the data in order to determine the Fe, Co and Ni concentrations in the sample. The method was applied to a washing solution used in an automotive factory and to a waste acidic mine effluent. Results obtained agreed well with those obtained by AAS or ICP-AES.
Cobalt Iron Nickel Environmental Waste Spectrophotometry

"Catalytic Determination Of Dissolved Inorganic Carbon In Natural Waters By Flow Injection Spectrophotometry"
Analyst 1996 Volume 121, Issue 11 Pages 1617-1619
Nelson Maniasso, Sandra Sato, Maria F. Gin&eacute; and Antonio O. Jacintho

Abstract: Sample was aspirated (2 ml/min) so as to fill a 750 µL sampling loop. The loop contents were injected into a carrier stream (1.6 ml/min) of 30 mg/l silicate of a flow injection manifold (schematic shown). The sample zone was merged successively, with reagent streams of 0.5 M acetate buffer of pH 5 (0.4 ml/min), Cr(III) (3 g/l aged for 10 days before use; 0.4 ml/min) and 0.3 M EDTA (0.4 ml/min). The mixture was passed through a 200 cm coil maintained at 45°C and the absorbance was measured at 540 nm. The calibration graph was linear for 10^-300 mg/l dissolved inorganic carbon (as hydrogencarbonate). The RSD (n = 9) at the 50 mg/l level was The throughput was 36 samples/h. The method was applied to lake, river, well and tap water. The results obtained agreed with those obtained by titrimetry.
Carbon, inorganic Environmental Water Lake River Well Spectrophotometry

"Determination Of Ammonia In Waste Waters By A Differential PH Method Using Flow Injection Potentiometry And A Nonactin-based Sensor"
Analyst 1997 Volume 122, Issue 1 Pages 89-93
Hongda Shen, Terence J. Cardwell and Robert W. Cattrall

Abstract: A water sample (20 µL) was injected into a water stream (0.9 ml/min) which merged with a stream (0.9 ml/min) of 0.6% acetic acid buffer of pH 6 containing 0.84% LiCl and 0.42% LiOH, then passed through a PTFE reaction coil (20 cm x 0.5 mm i.d.) prior to detection. The potential was recorded at a nonactin-based ammonium ion-selective sensor (fabrication described) vs. Ag/AgCl and a reference stream (0.9 ml/min) of 0.15 M LiCl (diagram of FIA system given). A second analysis was carried out, using LiCl/LiOH/0.75% boric acid buffer of pH 9.4 containing 0.84% LiCl, 0.42% LiOH and 5 µM-KCl in place of the pH 6 buffer. The difference between the potentials recorded with the different buffers was used to determine NH3 by a chemometric technique (details given). The use of this approach enabled the interference from moderate concentrations of K and Na to be corrected. Calibration graphs were linear (graphs shown) and the determination limit was ~1 µM. Recoveries and RSD are presented. The throughput was 30 samples/h. The method was applied to waste water and river water. The results were compared to those obtained by a gas diffusion technique.
Ammonia River Waste Potentiometry Electrode Sensor

"Electrochemical Detection Of African Swine Fever Virus In Pig Serum With A Competitive Separation Flow Injection Analysis Immunoassay"
Analyst 1997 Volume 122, Issue 2 Pages 155-159
Matthias Stiene and Ursula Bilitewski

Abstract: Pig serum was diluted 50-fold with PBS containing 0.05% Tween 20. A portion (1 ml) of the resulting solution was incubated with 50 ng biotinylated virus protein VP73 (preparation described) and 250 ng horse-radish peroxidase-labelled mAb 18BG3 (Ingenasa) for 25 min. A portion of the reaction mixture was injected into a carrier stream of 0.1 M phosphate buffer of pH 5.5 (buffer A) and passed through a column of biotinylated glass beads coated with streptavidin (preparation described) where the immunological complex formed during the incubation reaction was trapped. The peroxidase activity of the captured labelled antibodies was determined by passing a solution of H2O2 and hydroquinone (each 2 mM) in buffer A through the column and detecting the enzymatic product amperometrically at a vitreous C electrode at -100 mV vs. Ag/AgCl. The calibration graph was linear from 1-80 ng/ml mAb 18BG3 with a concentration of 50% inhibition at 6 ng/ml.
African swine fever virus Serum Pig Immunoassay Amperometry Electrode

"Flow Injection Fluorimetric Determination Of Ascorbic Acid Based On Its Photooxidation By Thionine Blue"
Analyst 1997 Volume 122, Issue 2 Pages 115-118
Tom&aacute;s P&eacute;rez-Ruiz, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Ciriaco Sidrach

Abstract: The photooxidation of ascorbic acid sensitized by Thionine Blue was studied. The Leucothionine Blue formed during the reaction is highly fluorescent. A flow injection method using merging zones is proposed for the determination of ascorbic acid over a concentration range from 8 x 10^-7 to 5 x 10^-5 mol L-1 with a throughout of 80 samples per h. The method was used for the simple and rapid determination of ascorbic acid in pharmaceuticals, fruit juices and soft drinks. A sample (250 µL) and 150 µL 80 µM-Thionine blue were simultaneously injected into two carrier streams (each flowing at 0.6 ml/min) of 0.2 M phosphate buffer of pH 3 then synchronously merged. The mixture was passed through a 200 cm PTFE reactor where it was irradiated for 20 s. Fluorescence intensity was then measured at 464 nm (excitation at 340 nm). A diagram of the manifold used is given. The calibration graph was linear from 0.14-8.8 µg/ml ascorbic acid. The throughput was 80 samples/h. The method was applied to pharmaceuticals, fruit juices and soft drinks. The results obtained agreed with those obtained by the standard 2,6-dichlorophenolindophenol method.
Ascorbic acid Soft drink Fruit Pharmaceutical Fluorescence

"Determination Of Trace Amounts Of Zinc In Water Samples By Flow Injection Isotope-dilution Inductively Coupled Plasma Mass Spectrometry"
Analyst 1997 Volume 122, Issue 3 Pages 233-237
Tarn-Jiun Hwang and Shiuh-Jen Jiang

Abstract: A water sample (25 ml) was adjusted to pH 4 with 5 mL 1 M ammonium acetate buffer. After a suitable amount of Zn-67 had been added, the solution was diluted to 50 mL with water. A portion (10 ml) of the resulting solution was loaded at a flow rate of 10 ml/min on to a column (5 cm x 10 mm i.d.) of SO3-quinolin-8-ol carboxy-methylcellulose. The column was washed with 0.1 M ammonium acetate buffer of pH 4; the retained Zn was eluted (3 ml/min) with 0.5 M HNO3. The eluate was analyzed by ICP-MS (details given). The Zn-66/Zn-67 isotope ratio was calculated from the peak areas of the flow injection peaks. The calibration graph was linear up to 50 ng/ml Zn-66; the detection limit was 14 pg/ml. RSD was 1.4% (n=7). The method was applied to several water CRM; the results agreed with the certified values.
Zinc-66 Zinc-67 Estuarine River Sea NRCC NASS-3 NRCC SLEW-1 NRCC SLRS-2 NRCC CASS-3 Mass spectrometry Mass spectrometry

"Lactate Amperometric Biosensor Based On An Electrosynthesized Bilayer Film With Covalently Immobilized Enzyme"
Analyst 1997 Volume 122, Issue 4 Pages 365-369
F. Palmisano, G. E. De Benedetto and C. G. Zambonin

Abstract: A Pt disc electrode coated with a poly(pyrrole) film as previously described (Centonze et al., Fresenius' J. Anal. Chem., 1992, 342, 729) was cycled between 0 and 1.5 V at a rate of 50 mV/s in 0.3 M methanolic NaOH containing 0.1 M tyramine. The Pt/poly(pyrrole)/poly(tyramine) electrode thus obtained was dipped in 2.5% glutaraldehyde for 2 h before being exposed to a solution of 100 iu/ml lactate oxidase in phosphate buffer for 2 h. Amperometric measurements of lactate with the fabricated biosensor were made at 0.7 V vs. Ag/AgCl in 0.1 M phosphate buffer of pH 7. The biosensor response time was 10 s. Calibration graphs were linear up to 0.6 mM lactate when used in a flow injection system; the detection limit was 70 nM. The biosensor was stable for at least 3 weeks. Although uric acid and paracetamol interfered slightly, the biosensor was able to separate the interferent and lactate responses in the time domain, giving an essentially bias-free measurement.
Lactate Amperometry Sensor Electrode Electrode

"Modulation Of The PH In The Determination Of Phosphate With Flow Injection And Fourier Transform Infrared Detection"
Analyst 1997 Volume 122, Issue 6 Pages 525-530
R. Vonach, B. Lendl and R. Kellner

Abstract: A sample (1.5 ml) was injected into a carrier stream at a flow rate of 1.1 ml/min (carrier not specified) and mixed with a stream of acetate buffer at a flow rate of 0.055 ml/min to adjust the pH to 5. The FTIR spectrum (reference spectrum) was recorded from 900-1300 cm-1. A second portion (1.5 ml) of the sample was then injected into the carrier stream and mixed with 100 µL of either carbonate buffer (method A) or NaOH solution (method B) to adjust the pH to 10 or >13, respectively. The FTIR spectrum (sample spectrum) was again recorded. Phosphate was quantified from the difference between the reference and sample spectra, using the peaks at 1085-1095 and 999-1009 cm-1 for methods A and B, respectively. The calibration graph was linear from 0.1-1 g/l phosphate. The throughput was 60 samples/h. The methods were applied to the analysis of soft drinks (results presented).
Phosphate Soft drink Spectrophotometry

"Use Of A Bentonite-modified Carbon-paste Electrode For The Determination Of Some Phenols In A Flow System By Differential Pulse Voltammetry"
Analyst 1997 Volume 122, Issue 6 Pages 601-604
Ignacio Naranjo Rodr&iacute;guez, Juan A. Mu&ntilde;oz Leyva and Jos&eacute; L. Hidalgo Hidalgo de Cisneros

Abstract: The behavior of various phenols at the cited electrode in a flow system was studied. A sample (0.25 ml) was injected into a carrier stream of either Britton-Robinson buffer of pH 4 or formate buffer of pH 4-5 at a flow rate of 1.25 ml/min. Differential-pulse voltammetric measurements were made at a C paste electrode modified with 5-10% bentonite. Both flow injection and stopped-flow modes were employed. The following phenols: 2,4-Dinitrophenol (I), 2-methyl- 4,6-dinitrophenol (II) and 2,4-dimethylphenol (III) showed good electroanalytical behavior at the bentonite-modified electrode, enabling these compounds to be determined successfully. However, pentachloro-phenol and 4-chloro-3-methylphenol could not be determined satisfactorily owing to a lack of stability of the electrode surface. The method was used to determine I-III in spiked seawater: recoveries were 95-101%.
Phenols 2,4-Dinitrophenol 2-Methyl-4,6-dinitrophenol 2,4-Dimethylphenol Sea Voltammetry Electrode Electrode

"Flow Injection Photometric Determination Of Zinc And Copper With Zincon Based On The Variation Of The Stability Of The Complexes With PH"
Analyst 1997 Volume 122, Issue 10 Pages 1045-1048
Pablo Richter, M. In&eacute;s Toral, A. Eugenia Tapia and Emely Fuenzalida

Abstract: A flow injection photometric method for the sequential determination of zinc and copper in mixtures was developed based on the variation of the stability of the chromogenic complexes between the analytes and the reagent zincon with pH. At pH 5.0 only the Cu-zincon complex exists, whereas at pH 9.0 the copper and zinc chelates co-exist. A three-channel manifold was implemented containing two alternating buffer streams (pH 5 and 9) which permit the colored reaction products to be formed sequentially at both pH values, and consequently the mixtures can be resolved. A continuous pre-concentration unit (Chelex-100) was used in order to increase the sensitivity of the method, thus allowing the analysis of water samples in which the analytes are present at the ng mL-1 level. On the other hand, pre-concentration was not required when the analytes were determined in brass. Under the optimum conditions and using a pre-concentration time of 2 min, the detection limits (3s) were found to be 0.35 and 0.80 ng mL-1 for zinc and copper, respectively. The repeatability of the method, expressed as the RSD, was in all instances less than 3.1%. Considering the sequential determination of both species, a sampling rate of 70 h-1 was obtained if pre-concentration of the samples was not required.
Zinc Copper Environmental Spectrophotometry

"Multi-insertion Of Small Controlled Volumes Of Solutions In A Flow Assembly For Determination Of Nitrate And Nitrite With Proflavin Sulfate"
Analyst 1998 Volume 123, Issue 3 Pages 429-434
J. Mart&iacute;nez Calatayud, J. V. Garc&iacute;a Mateo and V. David

Abstract: A simple, maintenance-free, noncontaminating and completely automated flow system was developed for non-simultaneous determinations of nitrite and nitrate, in which spectrophotometric measurements at 328 nm were performed on the nitrite reaction with proflavin sulfate [bis(3,6-diaminoacridinium)sulfate]. The sample solutions were automatically inserted into phosphate buffer (pH 6.8) containing 10 mM EDTA by using a programmable solenoid valve; then they flowed through a 6.4 m x 0.5 mm id PTFE coil, wrapped around an 8 W low pressure Hg lamp, and finally they merged with a HCl solution of proflavin. With the lamp off the nitrite in the sample was selectively measured with a sensitivity of 0.75 x 104 absorbance (linearity range up to 0.6 absorbance; detection limit of 1.9 x 10^-7 M). With the lamp on, to determine the sum of nitrite + nitrate there was a decrease in sensitivity of 41% vs. that of the selective variant for nitrite determination The sample throughput was 15 h-1 and the relative standard deviation at a 6.4 x 10^-5 M level of nitrate was 0.4% (n = 15). Many interferences were studied and simple methods of correcting for them were applied to analyze samples such as waters, soils, fertilizers and meat. (26 References)
Nitrate Nitrite Environmental Environmental Commercial product Meat Spectrophotometry

"Liquid Chromatography With An Inductively Coupled Plasma Mass-spectrometric Detector For Simultaneous Determination Of Gold Drug Metabolites And Related Metals In Human Blood"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 8 Pages 767-771
Susan G. Matz, R. C. Elder and Katherine Tepperman

Abstract: Blood plasma or serum (0.5 ml) was digested with 2.5 mL of aqueous 40% HNO3 with heating for 30 s at 700 W. The cooled digest was analyzed by ICP-MS in conjunction with a flow injection system. The mobile phase comprised water, aqueous 5% HNO3, 50 mM NH4 acetate buffer (pH 5.5) or 50 mM Tris buffer (pH 6.5). Matrix effects were significant. Detection limits were 0.2 to 0.7 ppb of Au, Zn and Cu, and calibration graphs were rectilinear up to 1000 ppb. The digests were also determined by ICP-MS after separation by HPLC on a column (15 cm x 4.6 mm) of Alltech WAX 300 anion exchanger with 20 to 200 mM Tris buffer (pH 6.5) as mobile phase or on a column (30 cm x 7.5 mm) of Bio-Sil TSK 250, with 25 mM Tris buffer (pH 7.7) as mobile phase. The HPLC - ICP-MS system was applied in the simultaneous determination of sixteen elements.
Copper Gold Zinc Plasma Human Serum Human Mass spectrometry Sample preparation

"Indirect Determination Of Diethyldithiocarbamate By Atomic Absorption Spectrometry With Continuous Extraction: Application To The Determination Of The Fungicide Ziram"
J. Anal. At. Spectrom. 1990 Volume 5, Issue 8 Pages 693-696
Oroncio Jim&eacute;nez de Blas, Jos&eacute; Luis Pereda de Paz and Jes&uacute;s Hern&aacute;ndez M&eacute;ndez

Abstract: The method was based on formation of the dithiocarbmate ion - Cu(II) complex which was extracted into isobutyl methyl ketone (I) in a flow injection system and determined by AAS. An aqueous solution (25 ml) containing the sample, e.g., diethyldithiocarbamate (II), 2.0 mL of 10 mM Cu(II) and 15 mL of 0.5 M acetic acid - acetate buffer (pH 4.7) was mixed in a segmenter with a I stream (1.0 mL min-1) and passed through a 25-cm long extraction coil and a membrane phase separator (described). An aliquot (40 µL) of the separated I solution was injected into a water stream (2.25 mL min-1) in which the Cu was determined by AAS in an air - acetylene flame at 324.7 nm. The possibility of interference from other metals and dithiocarbamates in the determination of II was discussed. The method was used to determine 6.0 to 12 µM-II; the detection limit was 0.12 µM-II. In the determination of 8.0 µM-II the precision was 2.6% (n = 10). The method was applied to determining 3.2 to 8.0 µM-ziram (procedure described).
Ziram Spectrophotometry Sample preparation

"Immobilized Alga As A Reagent For Preconcentration In Trace Element Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1991 Volume 6, Issue 8 Pages 643-646
Hayat A. M. Elmahadi and Gillian M. Greenway

Abstract: Metal ions in buffer solution were injected into a carrier stream (2 mL min-1) of water in a flow injection system (diagram given). The mixture was passed through a column (5 cm x 2.5 mm) packed with the alga Selenstrum capricornutum immobilized on controlled pore glass (details given). After washing with water, the accumulated ions were released by injection of HNO3 and passed to the flame for detection by AAS. Under optimized conditions (details given), the calibration graphs were rectilinear for 5 to 45, 10 to 100, 55 to 300, 650 to 5000, 15 to 80 and 60 to 450 ng mL-1 of Cu2+, Zn2+, Co2+, Hg2+, Cd2+ and Pb2+, respectively; corresponding detection limits were 0.05, 0.2, 8, 30, 2 and 2.5 ng mL-1. The sampling rate was 20 h-1.
Trace elements Spectrophotometry

"Determination Of Copper, Cadmium, Manganese, And Lead In Saline Water With Flow Injection And Atom Trapping Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 7 Pages 631-634
Lyndon A. Ellis and David J. Roberts

Abstract: A flow injection device has been developed to sep. Cu, Cd, Mn and Pb from a solution of sodium chloride, thus minimizing interference and enabling their accurate determination in high salinity waters such as sea- or estuary water. Micro-columns of Chelex 100 resin were used and parameters of ammonium acetate buffer concentration, pH and the concentration. of a buffer flush have been optimized. Close to 100% recovery of the transition elements and 99.8% exclusion of sodium chloride was achieved. Atom trapping atomic absorption spectrometry (ATAAS) was used as the detection technique to determine concentrations. of the four elements at four sites on the Severn Estuary. In addition, a water cut-off device has been incorporated to improve the safety of the AT app.
Copper Cadmium Manganese Lead Estuarine Sea Spectrophotometry

"Enzymatic Determination Of Urea In Serum Based On PH Measurement With The Flow Injection Method"
Anal. Chem. 1979 Volume 51, Issue 2 Pages 199-203
J. Ruzicka, E. H. Hansen, Animesh K. Ghose, and H. A. Mottola

Abstract: A method based on flow injection analysis incorporating a flow-through capillary pH electrode is described for the enzymatic determination of urea in aqueous and serum samples. By maintaining a constant buffering capacity of the carrier stream solution, a linear relation between the recorded pH signal and the urea content was obtained. Anaytical readouts were obtained within 30 s of sample introduction, and the sampling rate was 60 samples/h. The reproducibility of measurement was ±.0.0029 pH unit, corresponding to ±0.52%. When solution urease was used in the carrier stream, its consumption was 25 units per analysis. The possibility of further reducing the enzyme consumption by using the merging zone principle in the flow injection stop-flow system is discussed.
Urea Blood Serum Clinical analysis Electrochemical analysis Electrode

"Separation Of Trace Metal Complexes For Analysis Of Samples Of High Salt Content By Inductively Coupled Plasma Mass Spectrometry"
Anal. Chem. 1989 Volume 61, Issue 2 Pages 149-153
Michael R. Plantz, James S. Fritz, Fred G. Smith, and R. S. Houk

Abstract: Solutions of trace metals (Au, Bi, Co, Cr, Cu, Fe, Hg, Mo, Nb, Ni, Pt, Tl, U and V) in aqueous media of high salt content were treated with bis(carboxymethyl)dithiocarbamate reagent (prep. described) and injected into the loading solvent (0.05 M formate buffer of pH 3.25) for application to a column of Amberlite XAD-4 resin. The adsorbed complexes were eluted with aqueous 0.1 M NH3 (pH 11) and the eluate was analyzed by ICP-MS on a Sciex Elan model 250 instrument fitted with a continuous-flow ultrasonic nebulizer. Detection limits in salt-rich aqueous solution ranged from 6 ng L-1 for Bi to 80 ng L-1 for Pt. The method has been used to determine Cr, Ni and Pt in urine, and trace metals in seawater.
Chromium Nickel Platinum Sea Urine Mass spectrometry

"Polishable And Robust Modified Graphite Epoxy Electrodes"
Anal. Chem. 1989 Volume 61, Issue 5 Pages 508-512
Joseph Wang, Teresa Golden, Kurian Varughese, and Ibrahim El-Rayes

Abstract: Electrodes were prepared from Dylon grade RX epoxy-bonded graphite, with a modifier incorporated, packed into 4-mm-i.d. glass tubes; a Cu wire provided electrical contact. The electrode was cured at 55°C and 100°C for 2 h each, and the surface was polished with silicon carbide paper and 0.05 µm alumina slurry, then cleaned by sonication in water. Electrodes modified with, e.g., Co phthalocyanine (I), poly-(4-vinylpyridine) (II) or Dowex CGC241 cation-exchange resin were prepared. The last-named could be used to concentrate Cu non-electrolytically from methanol - acetate buffer (1:1) solution, and electrodes incorporating II were used to pre-concentrate Fe(CN)64- from phosphate buffer solution of pH 3. The I-containing electrode could be used to accumulate biological compounds, e.g., cysteine and penicillamine, and was suitable for amperometric detection in flow injection and LC systems. The electrodes could be re-polished to allow use over a period of several weeks.
Cysteine Penicillamine Electrode

"Fluorimetric Measurement Of Aqueous Ammonium Ion In A Flow Injection System"
Anal. Chem. 1989 Volume 61, Issue 5 Pages 408-412
Zhang Genfa and Purnendu K. Dasgupta

Abstract: The test solution (14 µL), containing NH3 or NH4+, is injected into a carrier stream (50 µL min-1) of water freed from NH3 and NH4+ by cation exchange, and the stream is mixed with 10 mM phthalaldehyde in aqueous 25% methanol (50 µL min-1) in a knotted coil and then with 3.0 mM Na2SO3 in 0.1 M phosphate buffer of pH 11.0 (50 µL min-1). The mixture is heated for ~40 s in a stainless-steel coil at 85°C (unnecessary at high NH4+ concentration.) and its fluorescence is measured at >425 nm (excitation at 351 nm). The detection limit is better than 20 nM-NH4+. The method is unaffected by NaCl concentration, and response to amino-acids is slight. The method has been used to determine NH4+ in tap- and lake water and rain.
Ammonium Water Lake Rain Environmental Fluorescence

"Sorbent Isolation And Elution With An Immiscible Eluent In Flow Injection Anlysis"
Anal. Chem. 1989 Volume 61, Issue 5 Pages 496-499
Wei Lei, Purnendu K. Dasgupta, Jorge L. Lopez, and Don C. Olson

Abstract: The use of a flow injection carrier that is immiscible with the sample matrix is illustrated. To determine thiols in gasoline, the sample is passed through a column of Amberlite IRA-401-S strongly basic anion exchanger (OH- form) on which the thiols are concentrated. A portion of aqueous NaOH (>1M) is then injected into the gasoline stream before the column, and elutes the thiols and regenerates the column. This solution enters a flow of the same NaOH, which is mixed with a stream of 1 M NaHCO3 as buffering agent; 1 mM 5,5'-dithiobis-(2-nitrobenzoic acid) is then introduced and the absorbance is measured at 450 nm. To determine aniline in benzene, the mixture is passed through a column of Rexyn-101 strongly acid cation-exchange resin (H+ form), which retains aniline. A portion of 0.1 M H2SO4 is then introduced to elute aniline from the column, and after this flow has merged with more 0.1 M H2SO4 the absorbance is measured at 280 nm. The sensing and delay circuits are illustrated. Response was rectilinear up to 2 mM for thiols and up to 10 ng mL-1 for aniline. Further possible applications are discussed.
Aniline Thiols Organic compound Oil Spectrophotometry

"Quantitative Determination Of Aqueous-phase Ozone By Chemiluminescence Using Indigo-5,5'-disulfonate"
Anal. Chem. 1989 Volume 61, Issue 6 Pages 619-623
Koji Takeuchi and Takashi Ibusuki

Abstract: The cited reagent (I; C. I. Food Blue 1) was used to determine O3 in aqueous solution from the chemiluminescence generated in a continuous-flow system (diagram presented). The optimum reagent composition was 10 mg L-1 of I in 2 mM phosphate buffer (pH 7.2). The calibration graph was rectilinear from 25 ng L-1 to 410 µg L-1 of O3; the limit of detection was 6 ng l-1, three orders of magnitude lower than that by spectrophotometry with use of I. The method should be applicable to environmental samples such as rain and fog.
Ozone Rain Fog Chemiluminescence

"Flow System For Starch Determination Based On Consecutive Enzyme Steps And Amperometric Detection At A Chemically Modified Electrode"
Anal. Chem. 1990 Volume 62, Issue 3 Pages 263-268
J. Emneus and L. Gorton

Abstract: A flow injection system is described for the determination of the total glucose content of starch. The system comprises three reactors, in each the required enzyme is immobilized on glutaraldehyde-activated, aminopropyl-silanized controlled-pore glass (CPG) of specific diameter and pore size, these being, respectively, (i) Termamyl 120L (Novo Industri, Denmark), used at 60°C on CPG (75 to 125 µ diameter), (ii) amyloglucosidase, from Aspergillus niger, on CPG (125 to 180 µm) and (iii) porcine mutarotase co-immobilized with glucose oxidase, on CPG (37 to 74 µm). The H2O2 released in (iii) is detected at a graphite electrode with a catalytic layer of Au - Pd (3:2), operated at +0.6 V vs. Ag - AgCl. The carrier flow (0.5 mL min-1) is 0.1 M acetate buffer of pH 5.0 for (i) and (ii) adjusted to pH 7.0 for (iii) by addition of 0.2 M phosphate (pH 7.6). Calibration graphs are rectilinear from 10 µM- to 0.6 mM of glucose with an injection volume of 160 µL and 15 samples h-1 throughput.
Glucose Organic compound Amperometry Electrode

"Electrochemical Platinization Of Reticulated Vitreous-carbon Electrodes To Increase Biosensor Response"
Anal. Chem. 1990 Volume 62, Issue 11 Pages 1106-1110
George H. Heider, Sylvia V. Sasso, Keming Huang, Alexander M. Yacynych, and Henry J. Wieck

Abstract: A method is given for the partial plating of a reticulated vitreous-carbon electrode (2 cm x 3 mm diameter) with Pt. The electrode was then coated with glucose oxidase with use of the carbodi-imide immobilization technique. The resulting electrode was used for the determination of glucose in serum by flow injection analysis (max. sampling rate 118 h-1). Samples (5 or 100 µL) were injected into the carrier stream (0.1 M phosphate buffer of pH 7.4; 2 mL min-1). The H2O2 formed in the enzymatic reaction was detected amperometrically at +0.6 V vs. the SCE. Calibration graphs were rectilinear for up to 50 and 10 mM glucose, respectively, for the two sample sizes, with corresponding detection limits of 0.25 and 0.05 mM. These responses make the electrode applicable in the clinical range (3.5 to 6.5 mM).
Glucose Blood Serum Electrode Sensor

"Use Of Ionomer Membranes To Enhance The Selectivity Of Electrode-based Biosensors In Flow Injection Analysis"
Anal. Chem. 1990 Volume 62, Issue 22 Pages 2418-2424
Sara A. Rosario, Geun Sig Cha, Mark E. Meyerhoff, and Marek Trojanowicz

Abstract: The use of ionomer membranes to enhance the selectivity of potentiometric enzyme electrodes in flow injection measurement arrangements is examined. The ionomer membranes employed are permeable to analyte substrates but relatively impermeable to detectable ions that would normally interfere with the measurement of the substrates if the enzyme electrodes were in direct contact with the sample. As a model system, the selectivity of enzyme electrodes prepared with nonactin-based ammonium-sensitive polymeric membranes is evaluated. In the preferred configuration, a thin hydrophilic anion-exchange membrane is incorporated within a flow-through dialysis unit upstream from the enzyme-electrode detector. As the sample passes through the dialysis unit, neutral or anionic analyte molecules (urea or glutamine) move through the membrane while the permeation of endogenous ammonium ions and other cations in the sample is retarded. A flowing recipient buffer on the other side of the membrane carries the analyte substrate to the enzyme-electrode detector. Enhancements in selectivity for analyte substrates over endogenous ammonium and potassium ions are greater than or equal to 9-fold when compared to enzyme-electrode flow injection analysis (FIA) systems assembled without the ionomer membrane unit. The analytical utility of the proposed system is demonstrated by the accurate measurements of urea in blood serum and L-glutamine in hybridoma bioreactor media.
l-Glutamine Urea Blood Serum Potentiometry Ion exchange Sensor Electrode

"Flow Injection Solid-phase Chemiluminescent Immunoassay Using A Membrane-based Reactor"
Anal. Chem. 1991 Volume 63, Issue 7 Pages 666-669
Hanjiu Liu, Jim C. Yu, Dilbir S. Bindra, Richard S. Givens, and George S. Wilson

Abstract: A flow injection analysis sandwich immunoassay system is described which uses a thin layer flow cell as the immunoreactor with antigen immobilized on a poly(vinylidene fluoride) polymer-based membrane. The membrane and a PTFE spacer are mounted between transparent plates, forming a 5 µL flow cell. The analytical performance of the system was evaluated by the sequential injection of monoclonal anti-bovine IgG (analyte), horseradish peroxidase (I)-labelled goat anti-mouse IgG, 0.1 M phosphate buffer (pH 7.4) and the enzyme substrate and luminol reagents. The I was used to catalyse the enhanced luminol reaction, resulting in chemiluminescence which was detected directly within the immunoreactor by a photomultipiler tube. The light-scattering problem associated with tubing reactors was eliminated and a universal calibration graph was obtained for different pieces of membrane coupled to the protein under identical conditions. A detection limit of 1 fmol was achieved with an assay time of about 10 min.
Chemiluminescence Immunoassay

"Batch-injection Analysis"
Anal. Chem. 1991 Volume 63, Issue 10 Pages 1053-1056
Joseph Wang and Ziad Tah

Abstract: The cited technique is a non-flow injection technique in which a small liquid sample is injected towards a nearby detector surface immersed in a large volume of stirred blank solution A transient peak-shaped response is recorded by the detector, which corresponds to passage of the sample zone over its surface. Determination was carried out in a cell that consisted of a retangular-shaped container (10 cm x 10 cm x 8 cm) made of Plexiglas and in which an inverted working disc electrode (e.g., a carbon-paste disc electrode) was introduced at the bottom corner. A micro-pipette, which was used for sample introduction, was positioned so that its tip was ~2 mm above the disc electrode surface. The counter and reference electrodes were mounted through two holes in the top cover of the cell, and the cell was placed over a magnetic stirrer. The system was used for the determination of K4Fe(CN)6, paracetamol, quinol, ascorbic acid and glucose with use of 0.1 M phosphate buffer (pH 7.4), 0.1 M KCl or 1 M NaOH as supporting electrolyte. In all instances, response increased rectilinearly with increasing analyte concentration. The technique is rapid and simple and performs well in terms of sensitivity and reproducibility.
Ascorbic acid Glucose Acetaminophen Quinol Electrode Electrode

"Solid-surface Room-temperature Phosphorescence Optosensing In Continuous-flow Systems: An Approach For Ultratrace Metal Ion Determination"
Anal. Chem. 1991 Volume 63, Issue 17 Pages 1759-1763
Rosario Pereiro Garcia, Yi Ming Liu, Marta Elena Diaz Garcia, and Alfredo Sanz-Medel

Abstract: Solid-surface room-temperature phosphorescence (SSRTP) optosensing in an aqueous flow is reported here for the first time, and it has been applied to aluminum control in samples of clinical interest. This technique makes use of flow injection analysis (FIA) and is based on the transient immobilization (on a strongly basic anion-exchanger resin packed in a flow cell) of the complex formed by the phosphorogenic reagent 8-hydroxy-7-iodo-5-quinolinesulfonic acid (ferron) with aluminum in a continuous-flow carrier at pH 5.5. The analytical performance characteristics of the proposed method for semiautomated analysis and control of very low levels of Al were as follows: 2 µg/L detection limit, +- 3.2% precision analyzing 40 µg/L of the metal and most of the common ions in biological samples did not interfere. Only Fe(III) caused serious interference, but it can be masked by 1,10-phenanthroline. The recommended method has been successfully tested for Al determinations at µg/L levels in samples of particular importance today (dialysis fluids and concentrates). Basic experiments on the characteristics of the RTP observed for different media used to secure the necessary rigidity (micelles, vesicles, filter paper, strong anionic resins, etc.) have demonstrated that Dowex 1 times 2-100 resin seems to provides the best sheltering to the excited triplet state. Possible interaction mechanisms between phosphor and supports are suggested. The cited technique was applied in the determination of Al in clinical samples. Sample or standard solution (0.5 ml) were injected into 0.2 M acetic acid - Na acetate buffer solution (pH 5.5) in the flow injection manifold (described with diagram) and mixed in a T-piece with a buffer stream into which 75 µM-8-hydroxy-7-iodoquinoline-5-sulfonic acid solution (0.6 ml) had been injected. The resulting stream was passed through a 3.5-m reaction coil and then to a flow cell (25 µL) containing Dowex IX2-100 resin. The phosphorescence of the complex adsorbed on the resin was measured at 600 nm (excitation at 400 nm). After detection, the adsorbed complex was desorbed with 6 M HCl (2 ml). Calibration graphs were rectilinear up to 100 ng mL-1 of Al. The detection limit was 2 ng mL-1 of Al. The coefficient of variation was ±3.2% at 40 ng mL-1 of Al
Aluminum Biological Phosphorescence

"Kinetic Study Of Background Emission From Peroxyoxalate Chemiluminescence Reaction And Application To The Improvement Of Detection Limits In Liquid Chromatography"
Anal. Chem. 1991 Volume 63, Issue 23 Pages 2680-2685
Nobuaki Hanaoka, Hiroshi Tanaka, Akira Nakamoto, and Michinosuke Takada

Abstract: A stopped-flow method based on a modified HPLC system (ODS column) with peroxyoxalate chemiluminescence detection was used to monitor the background emission vs. time in a mixture of imidazole buffer, bis-(2,4,6-trichlorophenyl) oxalate and H2O2. Similar measurements were carried out in conjunction with the HPLC of dansylated amino-acids. Background emission occurred much sooner than that from the fluorophores. The effects of temp., pH, water content and reagent concentration. on the intensity and kinetics of emission were assessed, together with the effects of an optical filter and of quenching materials, in order to clarify the sources and mechanisms of background emission. Conditions for the determination of dansylamino-acids were optimized by means of flow injection analysis; thus, a detection limit of ~4fM for dansylalanine was attained by using 2 mM imidazole and 40 mM H2O2 at 30°C, and this was improved to 2fM by commencing measurements 20 s after the start of reaction.
Chemiluminescence HPLC

"Determination Of Boron In Light- And Heavy-water Samples By Flow Injection Analysis With Indirect UV - Visible Spectrophotometric Detection"
Anal. Chem. 1992 Volume 64, Issue 19 Pages 2201-2205
Therese Lussier, Roland Gilbert, and Joseph Hubert

Abstract: The sample was injected into a carrier stream of water, which was then merged with a stream of 0.29 mM chromotropic acid buffered at pH 7.4 with 0.5 M Na acetate (both 0.3 mL min-1). Detection was at 361.6 nm; the calibration graph was rectilinear from 40 to 6000 µg l-1. The coefficient of variation was 3% for 1000 µg L-1 and 1% at higher levels. The relative error was 6% and the detection limit was 8 µg l-1.
Boron Water Water Spectrophotometry

"Penicillin Sensor Based On A Micro-array Electrode Coated With PH-responsive Polypyrrole"
Anal. Chem. 1992 Volume 64, Issue 21 Pages 2642-2644
Matsuhiko Nishizawa, Tomokazu Matsue, and Isamu Uchida

Abstract: A micro-array electrode with two Pt arrays with six elements each on a glass substrate was fabricated by photolithography in a configuration previously described (e.g., Matsue et al., J. Chem. Soc., Chem. Commun., 1991, 1029). The electrode was made hydrophobic by immersion in 20 mM octadecyltriethoxysilane solution in benzene for 12 h before electrodeposition of polypyrrole from aqueous 0.1 M KNO3 containing 0.1 M pyrrole under N with one array at 650 mV and the other at 670 mV vs. SCE. The polypyrrole-coated electrode was coated with a cross-linked penicillinase membrane. The device was placed in a flow-cell in a flow injection system operated with 0.1 M KNO3 - 10 mM Britton - Robinson buffer solution or 0.1 M KNO3 - 5 mM phosphate buffer solution as mobile phase (2 mL min-1).
Penicillin Electrode Electrode Electrode Sensor

"Flow Injection Renewable Surface Immunoassay: A New Approach To Immunoanalysis With Fluorescence Detection"
Anal. Chem. 1994 Volume 66, Issue 11 Pages 1825-1831
Cy H. Pollema and Jaromir Ruzicka

Abstract: Agarose beads (~35 µm) coated with goat anti-mouse IgG1 (heavy chain specific) were diluted 1:20 in 0.01 M phosphate buffer containing 0.5 M NaCl (buffer A) to give a suspension containing ~2 x 105 beads/ml. Portions (42 µL) of the suspension were pumped into the jet ring cell of the sequential injection system (diagram given). The beads were retained on a optical flat surface monitored by fluorescence microscopy with excitation at 450-490 nm and use of a 520 nm long-pass emission filter. For competitive assays, a mixture of unlabelled (sample) and R-Phycoerythrin-conjugated mouse IgG1 mAb diluted in buffer A was then pumped into the cell. Unbound sample was washed away, the signal change due to the bound labelled sample was measured, and the beads were then removed from the cell with a reversed buffer flow; buffer A was used as the carrier throughout (0.25-1 ml/min). The calibration graph was linear from 1-5 µg/ml of mouse IgG1 mAb (using 5 µg/ml of labelled antigen and a contact time of 25 s). The method was also applied to a non-competitive immunoassay (details given).
Immunoglobulin G Plasma Mouse Fluorescence Immunoassay

"Incorporation Of A Coated Tubular Solid-state Iodide Selective Electrode Into The Conduits Of A Flow Injection System"
Fresenius J. Anal. Chem. 1986 Volume 325, Issue 3 Pages 247-251
Jacobus F. van Staden

Abstract: A tubular flow-through electrode (5 mm long, 2 mm i.d.) prepared by depositing AgI on silver foil and connected to an Orion Research microprocessor Ionalyzer with an Orion double-junction reference electrode was incorporated in a flow injection system (diagram given) capable of 90 samples h-1. Samples and ionic-strength-adjustment buffer were fed by a peristaltic pump with a pulse suppression system. Optimum sensitivity and response were obtained with 0.1 M KNO3 - 0.02 M acetic acid buffer. Response of carefully conditioned electrodes was rectilinear from 5 to 5000 mg L-1 of I-; they were stable and needed little maintenance. Analyses of iodized table salt agreed reasonably with quoted I- concentration, with a coefficient of variation of <1.8% (n = 15). The practical range was 5 to 2000 mg l-1.
Iodide Iodized Electrode Potentiometry

"Determination Of Cyanide In Waste Water By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1989 Volume 333, Issue 7 Pages 719-720
G. Sch&ouml;ndorf and H. Engelhardt

Abstract: Waste water containing CN- is caused to react with Chloramine T in buffer solution under conventional flow injection conditions and the resultant solution is combined in a mixer and a coiled capillary with pyridine - barbituric acid before spectrophotometric determination. Detection limits are improved considerably by a reversed method in which the reagents are injected into the CN--containing stream. Calibration graphs are rectilinear for 0.01 to 6 ppm and for 0.002 to 1.5 ppm by normal and reversed flow injection analysis, respectively.
Cyanide Waste Spectrophotometry

"Ion-chromatographic Trace Analysis Of Mercury, Cadmium And Zinc By Post-column Derivatization With A Water-soluble Porphyrin"
Fresenius J. Anal. Chem. 1989 Volume 334, Issue 6 Pages 507-510
Daren Yan, Jingan Zhang and Georg Schwedt

Abstract: Sample solution was subjected to ion chromatography on a Nucleosil SA (10 µm) column (20 cm x 4 mm) with 0.5% NaCl solution in 1 mM tartrate (pH 4.3) as mobile phase (0.6 mL min-1). Post-column reaction with 10 µM-4,4',4'',4'''-(21H,23H-porphine-5,10,15,20-tetrayl)tetrabenzenesulfonic acid - 1 µM-4-(2-pyridylazo)resorcinol - 0.6% of NaCl - 32 mM borate buffer of pH 11.5 (0.3 mL min-1) was carried out in a T-shaped mixing cell, and detection was at 430 nm. Calibration graphs (injection volume 0.1 ml) were rectilinear for 0.002 to 0.8, 0.1 to 8 and 0.05 to 20 mg L-1 for Cd, Hg and Zn, respectively; corresponding detection limits were 0.5, 50 and 10 µg l-1. The method was successfully applied in the determination of these metals in waste water, a silicate sample and rice.
Mercury Cadmium Zinc Waste Rice HPIC Spectrophotometry

"Gas Diffusion Separation And Flow Injection Potentiometry"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 1 Pages 21-28
Wolfgang Frenzel

Abstract: The similarities and differences between gas-sensing ion-selective electrodes and gas diffusion separation - flow injection potentiometry are discussed with emphasis on selectivity and sensitivity. Examples of the latter method are described. For the determination of NH4+, a liquid sample stream containing 10^-8 to 10^-5 M NH4+ is mixed with 1 M NaCl in 0.1 M NaOH and passed at 1.7 mL min-1 through a grooved diffusion cell with a membrane of microporous polypropylene tubing, NH4+ is adsorbed in Tris-buffer (pH 7.5) and detected with an NH4+ sensitive liquid membrane electrode. The method was also applied in the determination of CN-, sulfide and gas-phase nitrogen oxides.
Potentiometry

"Simultaneous-fluorimetric Methods For The Determination Of Ammonia And Urea By Use Of Flow Injection Configurations With Dual Injection Valves"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 6 Pages 490-493
Andr&eacute;s Izquierdo, Pilar Linares, M. D. Luque de Castro and Miguel Valcarcel

Abstract: With a parallel-valve configuration, two sample plugs (130 µL for NH3, 230 µL for urea) were simultaneously injected, one into a phosphate buffer (pH 8.0) stream which passed through a reactor containing immobilized urease (to form NH3 from urea) and the other into a borate buffer (pH 9.5) stream. The streams were merged before undergoing fluorimetric reaction with pre-mixed phthalaldehyde and 2-mercaptoethanol solution A delay between the arrival of the plugs at the detector was achieved by use of the enzyme reactor in conjunction with a delay coil in the phosphate stream. For the serial-valve configuration two sample plugs were injected into the phosphate buffer, and separated from each other by the enzyme reactor and the delay coil. Two peaks were obtained, the first giving NH3 concentration. and the second giving the NH3 originally present plus that formed from urea. Both configurations produced similar results, with rectilinear calibration ranges of 0.5 to 6.0 µg mL-1 (for NH3) and 1.0 to 10.0 µg mL-1 (for urea), recoveries of 94 to 107%, and a sampling rate of 60 h-1. The only serious interference was caused by Fe(II). The methods were applied to water samples.
Ammonia Urea Fluorescence

"Automatic Determination Of Malate Dehydrogenase Activity By Two Flow Injection Modes"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 8 Pages 676-678
Juan Manuel Fernandez-Romero and M. D. Luque de Castro

Abstract: Malate dehydrogenase activity was determined by normal (A) and stopped-flow (B) flow injection analysis by monitoring the decrease in absorbance due to NADH uptake. Injected volumes of 100 µL for A and 160 µL for B were mixed with 1 mM NADH and phosphate buffer solution (pH 7.0) in reactors 1.5 m and 20 cm long, respectively. For B, a delay of 28 s with a 60 s stop time were used. Both methods are suitable from 0.02 to 1.5 U l-1, and recoveries from human serum samples were >96%. Sample throughput was 60 h-1 and 36 h-1 for A and B, respectively.
Enzyme, malate dehydrogenase Serum Human Spectrophotometry

"Flow Injection Ion-exchange Preconcentration For The Determination Of Iron(II) With Chemiluminescence Detection"
Fresenius J. Anal. Chem. 1990 Volume 337, Issue 7 Pages 848-851
Abdulrahman A. Alwarthan, Khalil A. J. Habib and Alan Townshend

Abstract: Solutions of 10 µM-luminol and 10 µM-H2O2, each in 0.1 M carbonate buffer, were continuously pumped, each at 2 mL min-1, through the manifold of the flow injection system; the sample (3 ml; adjusted with 0.1 M phosphate buffer to pH 6.0) was pumped at 1.5 mL min-1 through a chelating column (2 cm x 2.5 mm i.d.) containing 8-hydroxyquinoline-5-sulfonic acid immobilized by azo-coupling on controlled-pore glass (pore diameter 22.6 nm; 80 to 120 mesh). The sample flow was then replaced by water to wash the column for 3 min. For elution of Fe, 52 µL of 0.15 M HCl was injected via the injection valve into the column, and the eluate was mixed with the reagent stream before measurement of the emitted chemiluminescence. A log - log calibration graph was rectilinear for Fe(II) pre-concentrated from triple 52 µL injections of Fe(II) solution (10 to 70 ng mL-1), and the detection limit was ~2 pg mL-1. Of the foreign ions tested, Mo(VI), VV, Ti(IV) and AgI increased and Cu(II) slightly decreased the chemiluminescence signal; Co did not interfere. One analysis took 5 min.
Iron(2+) Chemiluminescence

"Evaluation Of Experimental Conditions On The Response Of Fluoride And Cyanide Selective Electrodes In Flow Injection Potentiometry"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 2 Pages 159-162
Olaf Elsholz, Wolfgang Frenzel, Cheng-Yu Liu and J&uuml;rgen M&ouml;ller

Abstract: The response of three F-- and two CN--selective electrodes was studied under steady-state and flow injection conditions. Three flow cells were used, one with a tubular electrode configuration and two wall-jet cells. All measurements were carried out vs. SCE. The surface condition of the electrodes rather than the geometry of the flow cell determined the response time, especially at low analyte concentration. Polishing the surfaces improved the response time of both electrodes, making them suitable for use in flow injection systems. Long-term stability of the F--selective electrode was improved by using CDTA-free acetate buffer as the carrier stream and by mixing the sample with total ion strength adjustment buffer before injection. The lifetime of the CN--selective electrode was limited by corrosion, especially when used in a wall-jet cell; this may be improved by using a Ag2S membrane.
Electrode Electrode Electrode Electrode Potentiometry

"Fluorimetric Enzymic Flow Injection Determination Of Bile Acids In Human Serum"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 6 Pages 749-751
Antonio Membiela, Fernando L&aacute;zaro, M. D. Luque de Castro and Miguel Valc&aacute;rcel

Abstract: Bile acids were determined in serum based on the enzymatic oxidation of the analytes in a stream of 0.1 M phosphate buffer (pH 8.0) and 2.25 mM NAD+ and fluorimetric detection. Tauro-, cheno-, glyco- and chenodeoxy-cholic acids were determined from 0.3 to 10 µg mL-1. The coefficient of variation was 3%. Recoveries of bile acids were 93.6 to 104.4%. The method was fast, simple and convenient.
Bile acid Serum Human Fluorescence

"Diode-array Detectors In Flow Injection Analysis. Simultaneous Determination Of Rare Earth Metals With Arsenazo III"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 7 Pages 831-835
M. Blanco, J. Coello, J. Gen&eacute;, H. Iturriaga and S. Maspoch

Abstract: Ore (1 g) was treated with 20 mL of concentrated HNO3 and heated to dryness. The residue was treated with 20 mL of concentrated HCl and heated to dryness. The residue was resuspended in 0.1 M HCl, filtered, washed and the filtrate was diluted to 100 mL with 0.1 M HCl. A 25 mL aliquot was treated with 0.1 M NH3 and the ppt. was filtered off, washed and dissolved in 0.1 M HCl. The solution was mixed with 10 mL of tartaric acid and diluted to 100 mL with 0.1 M HCl. A portion of this solution was injected into a carrier stream of 1 M acetic acid - sodium acetate buffer (pH 4; 1.2 mL min-1), mixed with a reagent stream containing 0.3 mM arsenazo III and the absorbance of the solution was measured between 600 and 720 nm with use of a diode array detector. Binary mixtures of 0.5 to 2.5 µg g-1 of tervalent rare-earth-metal cations and 1.4 to 4.3 µg g-1 of U were accurately resolved with use of univariate calibration. The presence of Th (2.8 to 7.0 µg g-1) required use of multivariate calibration. Results obtained for the determination of Th and U in pitchblende agreed well with the certified values.
Metals, rare earth Uranium Thorium-232 Pitchblende Spectrophotometry

"Flow Injection Determination Of Oxalate In Urine Based On An Inhibitory Effect"
Fresenius J. Anal. Chem. 1991 Volume 339, Issue 1 Pages 58-61
J. A. Infantes, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: The method is based on the inhibitory effect of oxalate on the catalysis of H2O2 oxidation of 2,4-diaminophenol (I) by Fe(III). Thus, 0.1 M I is mixed with 1 M H2O2 - 1 M glycine buffer of pH 3.43, and sample mixed with 1 mM Fe(III) is injected into this stream. The mixture is passed through a reaction coil (350 or 50 cm), and detection is by measuring the absorbance decrease at 500 nm. For normal and stopped-flow methods, the calibration graphs were rectilnear for 0.2 to 12 and 0.2 to 40 µg mL-1, the precision was ±5.4% and ±3.5% (n = 11), and sampling rates of 30 and 20 h-1, respectively. Sample prep. was by the method of Archer et al. (Clin. Sci., 1958, 16, 405). Results for urine were good.
Oxalate Urine

"Potentiometric And Conductometric Determination Of Ammonium By Gas Diffusion Flow Injection Analysis"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 4-5 Pages 276-280
Wolfgang Frenzel Contact Information and Cheng-Yu Liu

Abstract: Sample in water carrier stream was merged with a 0.1 M NaOH reagent and the mixture was consequently merged in the gas diffusion cell with an acceptor stream of 0.02 M Tris - HCl buffer of pH 8 or of boric acid - NH4OH for potentiometric or conductometric detection. A liquid membrance ammonium-selective electrode was used for potentiometric detection in the 0.1 µM to 1 mM range. Both potentiometric and conductometric detection give similar selectivity and sensitivity, but the latter gave a linear rather than logarithmic response. Considerable enhancement of selectivity in the potentiometric and conductometric determination of ammonium is provided by gas diffusion separation in flow injection analysis Ammonium and potassium selective liquid membrane electrodes can be used for determination in the concentration. range 10^-7 - 10^-2 mol/L with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.
Ammonium Conductometry Potentiometry Electrode

"Flow Injection Analysis - Spectrophotometric Determination Of 8-hydroxyquinoline With P-aminophenol"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 216-220
B. A. Hasan A, K. D. Khalaf A, A. Morales-Rubio A, M. de la Guardia

Abstract: A 10 mL portion of 1 M NaOH was added to 8-hydroxyquinoline (quinolin-8-ol; I) prepared in HCl of pH 3, or in KCl/H3BO3/NaOH buffers of pH 8 or 10 and the total volume was diluted to 25 mL. Streams (3.2 ml/min) of p-aminophenol (PAP) (100 µg/ml) and 0.004 M KIO4 were mixed in a reactor coil (45 cm x 0.8 mm i.d.) and the benzoquinoneimine, formed in situ fed into a second reactor coil (400 cm x 0.8 mm i.d.) with 0.4 M NaOH (3.2 ml/min) into which a 500 µL portion of I in an appropriate buffer had been injected. The resultant indophenol dye (structure illustrated) was measured at 610 nm in a 50 µL flow cell (1 cm path). The calibration graph was linear from 2-8 µg/ml I and the detection limit was 7.6 ng/ml. The RSD (n = 4) was 0.06% for 4 µg/ml I. Recoveries of 98-102% were obtained at pH 3, 8 or 10. Sensitivity is lower (ε = 9500) for the reaction of I with PAP than reported for batch procedures which employ reactions of I with orthanilic acid (ε = 26 500) or diazotized 4-aminoacetophenone (ε = 33 700).
8-Quinolinol Water Environmental Spectrophotometry

"Flow Injection Analysis With Amperometric Detection For Measurements Of Proton Activities In Solutions Of Strong Acids And Strong Bases"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 4 Pages 392-396
Anastas Dimitrov Dakashev

Abstract: Flow injection and reversed flow injection analysis with amperometric detection were used for the determination of the concentrations of strong acids and strong bases and the pH of the solutions. The amperometric detection was based on the reduction current of hydrogen ion or water molecules. A platinum indicator electrode cathodically polarized at a constant potential was employed, choosing the potential in the rising part of the current/potential curve. On the basis of the experimental data an equation was developed for the calculation of the concentrations of the strong acids and strong bases and the pH by a non-linear regression computer program. Analysis was carried out with an FIA system (schematic given) consisting of a peristaltic pump and an injection valve with a loop volume of ~100 µL. An electrochemical detector as described previously (Ilcheva and Dakashev, Analyst, 1990, 115, 1247) was adapted to amperometric determination using a Pt wire (4 x 0.5 mm diameter) placed axially in a cylindrical channel (2 mm diameter) as an indicator electrode. An OH 102 polarograph was also used. A buffer vessel (75 ml) was inserted between the peristaltic pump and the injector valve. Buffer solutions were aqueous solutions of 0.1 M HCl/glycine for acid buffers and 0.1 M NaOH/glycine for basic. An equation was developed, using the data obtained by this system, to calculate concentrations of strong acids and bases, and pH, by a non-linear regression computer program (details given).
Acids Bases pH Amperometry Electrode

"Flow Injection Determination Of Anionic Polyelectrolytes Using An Anionic Surfactant-selective Plasticized Poly(vinyl Chloride) Membrane Electrode Detector"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 901-903
Takashi Masadome, T. Imato, Satoshi Itoh, Yasukazu Asano

Abstract: A portion (200 µL) of anionic polyelectrolyte solution was injected into a water stream (0.5 ml/min), which passed through a Dowex 50W-X4 cation-exchange column (19.5 cm x 2 mm i.d.), merged with a stream (0.5 ml/min) of NH3 buffer solution of pH 10 and passed through a mixing coil (1 m x 0.5 mm i.d.). A stream (0.5 ml/min) of 0.5 mM Cat-floc polymer (Wako Pure Chem. Co.) merged with a stream (0.5 ml/min) of 20 mM NaNO3 containing 0.6 mM sodium dodecylbenzenesulfonate, passed through a mixing coil (3 m x 0.5 mm i.d.), merged with the polyelectrolyte-containing stream and passed through a similar 1 m mixing coil prior to detection by a dodecylbenzenesulfonate-selective PVC-membrane electrode (cf. Anal. Sci., 1987, 3, 121). The calibration graph was linear from 0.1-1 mM potassium poly(vinyl sulfonate), the detection limit was 25 µM and the RSD (n = 5) was ~1.3%. The sampling rate was 10/h. Linear calibration graphs were also obtained for 0.1-1 mM sodium alginate and 0.1-1 mM carrageenan.
Electrolytes Polyvinyl sulfonate Alginate Carrageenan Potentiometry Electrode

"Sequential Flow Injection Spectrophotometric Determination Of Iron(II) And Iron(III) By Copper(II)-catalysed Reaction With Tiron"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 4 Pages 546-547
M. Endo and Shigeki Abe

Abstract: The method was based on the differential reaction kinetics of Fe(II) and Fe(III) with Tiron in a double-injection flow injection system (schematic of manifold given). Acetate buffer (0.1M) of pH 6 containing 6 mM Tiron was pumped into two reaction coils whilst 0.79 mM Cu(II)/6 mM Tiron/0.1 M acetate buffer of pH 6 flowed into a third reaction coil at 3.6 ml/min. Two sample solutions were injected into the reaction streams at the same time and the resulting absorbance of the Fe(III)-Tiron complex was measured at 560 nm. The oxidation of Fe(II) was increased by Tiron and Cu(II) catalyst. The first and second peaks at the detection cell corresponding to Fe(III) and total Fe, respectively. The calibration graph was linear from 18 µM to 0.18 M Fe(II) and Fe(III). The sample throughput was 30 injections/h.
Iron(2+) Iron(III) Spectrophotometry

"Liposome-based Flow Injection Enzyme-immunoassay For Theophylline"
Microchim. Acta 1990 Volume 100, Issue 3-4 Pages 187-195
Tai -Guang Wu and Richard A. Durst

Abstract: A peristaltic pump was used to supply, in 0.1 M Tris buffer (pH 7.2) as carrier, a standard solution of theophylline (I) or plasma sample, in the same buffer, to a column (17.8 cm x 2.5 mm) of glass beads coupled to monoclonal anti-theophylline antibodies. The injector (Rheodyne type 7010) then delivered a solution of liposomes that encapsulated horse-radish peroxidase and had been sensitized with 4-(1,3-dimethylxanthin-8-yl)butyric acid (II). Competition between I and II for the antibodies occured, and unbound liposomes were eluted for post-column reaction with H2O2 and 4-fluoriphenol. This reaction caused release of F-, which was determined with an Orion model 69-09 ion-selective electrode. The column was then washed with glycine - HCl solution to dissociate the antigen - antibody complex and reactivate the column. Calibration graphs are presented for two liposome compositions (10 and 20 miu mL-1 of enzyme activity). I can be detected over the concentration. range 0.2 to 4000 ng mL-1, i.e., a detection limit of 100 fmol in a 0.1 mL sample. For an activity of 10 miu mL-1, the coefficient of variation (n = 6) was 4.6% at the level of 4.3 ng mL-1. The assay takes ~10 min.
Theophylline Blood Plasma Immunoassay Electrode

"HPLC Post-column Derivatization Of Aromatic Amines Using N-methyl-9-chloroacridinium Triflate"
Microchim. Acta 1990 Volume 102, Issue 4-6 Pages 221-232
Myungsoo Kim and James T. Stewart

Abstract: Benzocaine (I) and butesin (II) in mobile phase were separated by HPLC on a column (25 cm x 4.6 mm) of ASI ODS (5 µm) with aqueous 80% methanol as mobile phase (1 mL min-1). Hydralazine (III), isoniazid (IV) and procainamide (V) in mobile phase were separated by HPLC on a column (10 cm x 4.6 mm) of Brownlee RP-8 (5 µm) with 100% methanol - aqueous phosphate buffer of pH 3 (1:1) as mobile phase (1 mL min-1). The column eluates were mixed with N-methyl-9-chloroacridinium triflate in acetonitrile (details given) and detected at 460 nm. Calibration graphs for I and II were rectilinear from 25 to 500 µM; coefficient of variation ranged from 1 to 6%. The limit of detection for I and II was 100 ng mL-1. Recoveries of III, IV and V were >97%, with coefficient of variation of 1.6, 0.5 and 1.4%, respectively.
Amines, aromatic HPLC

"Plastic Membrane Electrodes For The Potentiometric Determination Of Codeine In Pharmaceutical Preparations"
Microchim. Acta 1997 Volume 126, Issue 1-2 Pages 147-151
Eman M. Elnemma and M. A. Hamada

Abstract: The precipitates resulting from the mixing of codeine phosphate and tetraphenylborate or ammonium reineckate solutions were dried and ground. Portions were dissolved in THF, along with PVC powder and plasticizer (dioctyl phthalate or dibutyl sebacate), and the mixtures were evaporated in petri dishes, giving codeine-PVC membranes which were used to fabricate ISE. Crushed tablets were dissolved in aqueous citrate/phosphate buffer solution and potentiometrically analyzed using a codeine-PVC membrane electrode with a Ag/AgCl reference electrode. Pharmaceutical syrup was diluted with the same buffer and similarly analyzed. The electrode was also used for the potentiometric titration of codeine (I) solutions against sodium tetraphenylborate. The applicability of the electrode to FIA was investigated by determinations of I in samples injected into a flow of buffer and potentiometric detection using a sandwich cell incorporating the electrode. For the bulk methods, the calibration graphs were linear from 0.1-10 mM I and detection limits were 0.03-0.07 mM I. The electrodes were stable from pH 3-7. Recoveries from pharmaceuticals averaged 100.6%, and RSD (n = 3) averaged 0.8%. Titrimetric and FIA methods performed similarly, and the FIA method enabled the detection of down to 1 µM-I.
Codeine Pharmaceutical Pharmaceutical Potentiometry Electrode

"Multi-component Analysis With A Computerized Flow Injection System Using LED Photometric Detection"
Microchim. Acta 1991 Volume 103, Issue 3-4 Pages 159-169
Marek Trojanowicz, Joanna Szpunar-&#321;obi&#324;ska and Zdzislaw Michalski

Abstract: A ternary analyte mixture of metal ions (e.g., Al3+ - Fe3+ - Zn2+; 100 µL) was mixed with a chromogenic reagent, e.g., 0.05% xylenol orange solution in acetate buffer solution of pH 4.5, in a flow injection manifold and pumped to a POAS-4B LED photometer (Poliservice, Poland) modified for computer control with a stainless-steel flow cell (pathlength 1.5 cm), various LED (563, 580 and 638 nm) as light sources and a reverse-biased Si-diode light detector. All three wavelengths for a single sample mixture were monitored by a computer-controlled signal processor system. Precision for the above ternary mixture ranged from 1 to 5% with satisfactory accuracy up to 10 µg mL-1 (Al and Fe) or 5 µg mL-1 (Zn) and detection limits in the range 0.01 to 0.03 µg mL-1. Throughput was 150 samples h-1.
Aluminum(III) Iron(2+) Zinc(II) Spectrophotometry

"Indirect Ultra-violet Determination Of Cyanide By Flow Injection Analysis Using Absorption Of The Mercury - EDTA Complex At 250 Nm"
Microchem. J. 1989 Volume 39, Issue 1 Pages 99-105
Haj Hussein, A.T.

Abstract: The sample was injected into a carrier stream (0.37 mL min-1) of ammoniacal buffer solution containing 0.01 M EDTA, which was subsequently mixed with a reagent stream (0.37 mL min-1) of Hg - EDTA complex solution The mixture passed through a reaction coil (40 cm x 0.51 mm), and CN- was determined from the decrease in absorbance at 250 nm. The calibration graph was rectilinear for 0.5 (detection limit) to 52 ppm of CN-. At a sampling rate of 60 h-1, the coefficient of variation was ~1%. The effects of 16 foreign ions are tabulated.
Cyanide Spectrophotometry

"Spectrophotometric Determination Of Vanadium(V), Vanadium(IV), And Vanadium(III) With Pyrogallol In A Flow Injection System"
Microchem. J. 1990 Volume 42, Issue 3 Pages 319-322
B. Haghighi, N. Maleki, A. Massoumi, S. Razi and A. Sapavi

Abstract: Sample solution containing V (100 µL) were injected into a stream of acetate buffer solution (pH 6.0) that had been merged with a stream of pyrogallol (I) solution The I concentration. (1M), the length of the post-injection mixing coil (100 cm), the flow rates of the I and buffer streams (2 mL min-1) and the sample volume were optimized; the average sampling rate was 60 h-1. The absorbance of the resulting complex was monitored at 580 nm. The calibration graph (peak height) was rectilinear in the range 0 to 10 µg mL-1 and the limit of detection was 40 ng mL-1; there was no interference from any closely related ions. The method was applied to different synthetic samples, with good precision and excellent accuracy.
Vanadium(III) Vanadium(IV) Vanadium(V) Spectrophotometry

"Stabilization Of Lactate Dehydrogenase Activity By Poly[oxy]ethylene Glycol For Enzymic Assays Using Flow Injection Analysis At Microlitre Per Minute Flow Rates"
Microchem. J. 1991 Volume 44, Issue 1 Pages 4-14
James R. Marsh and Neil D. Danielson*

Abstract: Stabilization of lactate dehydrogenase (I) in the determination of pyruvate was achieved by the addition of polyoxyethylene glycol to the reagent solution By using a flow injection system containing a 50 cm knitted open tubular reactor and 67 µM-NADH - 15% polyoxyethylene glycol - I (2.5 iu mL-1) in Tris buffer solution as carrier stream (10 µL min-1), the calibration graph was rectilinear from 0.01 to 0.75 mM pyruvate and ~900 samples could be analyzed (330 s per sample at 10 µL min-1) with a loss of only 125 iu of I activity.
Pyruvate

"Flow Injection Fluorimetric Determination Of Tiopronin In Pharmaceutical Preparations"
Microchem. J. 1991 Volume 44, Issue 1 Pages 72-77
Tom&aacute;s P&eacute;rez-Ruiz*, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Gabriel Lambertos

Abstract: The method described is based on the inhibition by tiopronin (I) of the oxidation of thiamine to thiochrome by Hg(II). A three-channel manifold (diagram given) is used, in which sample and 1 mM Hg(II) (pH 4) reagent streams (1.7 mL min-1) are merged and mixed in a 1-m mixing coil. The resulting stream is merged with a 0.2 M phosphate buffer stream (1.7 mL min-1) and passed to a second mixing coil (2 m). Flow is stopped for 1 min, 30 s after injection to allow the reaction to occur in the second mixing coil. Fluorimetric detection was at 445 nm (excitation at 365 nm). The calibration graph was rectilinear from 10 to 80 µM-I and coefficient of variation of 1.2%. The method was applied to dosage forms containing I.
Tiopronin Pharmaceutical Fluorescence

"Fluorimetric Flow-through Sensor For The Determination Of Pyridoxal"
Microchem. J. 1991 Volume 44, Issue 2 Pages 215-221
Danhua Chen, M. D. Luque de Castro* and M. Valcarcel

Abstract: The flow injection configuration selected from the three tested comprised two carrier streams of water, each at 0.48 mL min-1, into which the sample solution and a mixture (1:9, prepared fresh daily) of 5 mM Be in 0.05 M HNO3 with 3 M ammoniacal buffer of pH 9.9, respectively, were injected, a 3-m coil through which the combined streams flowed, and a flow-through fluorescence cell (Hellma 178-12 QS) containing a porous plastic plug. The portion in the light path was packed with C18 silica (60 to 100 µm). The fluorescence of the Be - pyridoxal (I) complex retained by the adsorbent was measured at 450 nm with excitation at 360 nm. The range of rectilinear response was 0.2 to 16.0 µM-I. The coefficient of variation at 10 µM was 0.79% (n = 7) and the sampling frequency was 6 h-1. This method was more sensitive by two orders of magnitude than a conventional flow injection method.
Pyridoxal Fluorescence Sensor

"Simultaneous Determination Of Hydrochlorothiazide And Spironolactone In Pharmaceutical Preparations Using Batch And Dynamic Systems"
Microchem. J. 1997 Volume 56, Issue 2 Pages 207-215
E. Mart&iacute;n, O. Hern&aacute;ndez, J. J. Arias and A. I. Jim&eacute;nez

Abstract: A batch and flow injection method for the determination of hydrochlorothiazide (I) and spironolactone (II) in pharmaceuticals are described. For the batch method, samples were prepared in a 20% ethanolic solution containing acetic acid/sodium acetate buffer of pH 5 and scanned from 220-350 nm. For the flow injection method, samples diluted in ethanol were injected into a carrier stream of acetic acid/sodium acetate buffer of pH 5 in 90% ethanol. Spectra were recorded from 220-350 nm at 1 s intervals and an integration time of 0.4 s. Errors were Results by numerical and graphical methods were satisfactory but the best results were achieved with multiwavelength linear regression particularly with the flow injection system.
Spironolactone Hydrochlorothiazide Pharmaceutical Spectrophotometry

"Flow Injection Binding Assays: A Way To Increase The Speed In Binding Analyses"
Anal. Biochem. 1989 Volume 181, Issue 2 Pages 379-382
Bo Mattiasson, Per Berd&eacute;n and Torbj&ouml;rn G. I. Ling

Abstract: A flow injection binding assay for glucosides and mannosides is described. The sample was mixed with enzyme label (horseradish peroxidase) and passed through a column of immobilized concanavalin A. Bound activity was measured by passing substrate (to peroxidase) and chromogenic reagent through the column and monitoring the effluent spectrophotometrically. To speed up the assay, the sample was applied in pulses and the substrate was included in the column regeneration buffer. Calibration graphs for glucosides and mannosides were rectilinear for 0.02 to 2 mM.
Carbohydrates Glycoproteins Glycosides Mannosides Spectrophotometry

"Determination Of Inorganic Phosphate By Flow Injection Method With Immobilized Enzymes And Chemiluminescence Detection"
Anal. Biochem. 1989 Volume 182, Issue 2 Pages 366-370
Hideki Kawasaki, Katsumi Sato, Jyunko Ogawa, Yukio Hasegawa and Hidetaka Yuki

Abstract: Inorganic phosphate (I) was determined by flow injection analysis with use of two glass columns (0.9 cm x 3 mm), one packed with purine-nucleoside phosphorylase-coated controlled-pore glass beads (AMP-500; 120 to 200 mesh), and the second packed with xanthine oxidase and urate oxidase-coated beads (preparation described). The carrier solution (1 mL min-1) was 25 µM inosine in 10 mM HEPES - NaOH buffer (pH 7.5) and the H2O2 produced was determined with use of 10 µM luminol and 0.8 µM peroxidase in 50 mM carbonate buffer (pH 10.5) and chemiluminescence detection. The calibration graph was rectilinear for 5 to 250 pmol of K2HPO4 and the detection limit was 500 fmol. The within-assay coefficient of variation was 1.03 to 9.36%. The method was applied in determination of I in DNA.
Phosphate DNA Chemiluminescence

"Flow Injection Fluorometry Of Protein Using Hypochlorite-thiamine Reagent"
Anal. Biochem. 1990 Volume 184, Issue 1 Pages 184-188
Toshio Yokoyamaa, Noriko Nakamurab and Toshio Kinoshitac

Abstract: This paper describes a flow injection protein assay based on the formation of N-chlorides. Thiamine, which gives fluorescent thiochrome on reaction with N-chlorides, is used as a reagent. The protein sample is first mixed with the carrier solution containing sodium hypochlorite to chlorinate peptide bonds. The fluorescence reagent, containing thiamine and sodium nitrite, is then delivered to the mixture; the sodium nitrite decomposes active chlorine. The assay is sensitive, reproducible, and linear over a range from 20 ng to 2 µg of bovine serum albumin. The fluorescence intensity reflects the correct amount of protein because the thiochrome formed is proportional to the number of peptide bonds. The method is based on that of Kinoshita et al. (Chem. Pharm. Bull., 1976, 24, 2901; 1980, 28, 641). The flow injection system is described and illustrated. Injected protein samples are heated in a spiral coil at 70°C with NaClO solution in a 50 mM phosphate buffer carrier stream of pH 7.5 containing 0.1% of Brij 35 (total available Cl content 0.05%). After this, the N-chloroproteins formed are mixed with phosphate-buffered 0.5% NaNO2 - 0.005% thiamine hydrochloride solution in a second reactor coil at 70°C. The unconsumed ClO- is thereby destroyed and the thiamine to oxidized by the N-chloroproteins to thiochrome. The flow stream is then cooled to 25°C and the fluorescence is measured at 440 nm (excitation at 370 nm). The response is rectilinear for 20 ng to 2 µg of protein (e.g., bovine serum albumin, for which the detection limit is 10 ng). Some compounds interfere, e.g., those with NH-groups (e.g., tryptophan, proline and some purine bases); it is suggested that interfering compounds can be removed by prior HPLC.
Protein HPLC Fluorescence

"Determination Of Phosphatidylcholine In A Flow Injection System Using Immobilized Enzyme Reactors"
Anal. Biochem. 1990 Volume 187, Issue 2 Pages 240-245
Mohammed Masoom, Rita Roberti and Luciano Binaglia

Abstract: Two alternative procedures are described for the quantitative determination of phosphatidylcholine in a flow injection system utilizing immobilized enzymes. Phospholipase C from Bacillus cereus and phospholipase D from cabbage were covalently bound to the surface of controlled-pore glass beads and the enzyme-derivatized beads were packed in small columns. In the first procedure, the phospholipase C column was connected with a second column containing coimmobilized alkaline phosphatase and choline oxidase. In the alternative procedure, the column packed with immobilized phospholipase D was connected with a column packed with immobilized choline oxidase. The hydrogen peroxide produced through the action of choline oxidase in both flow injection systems was detected amperometrically. Both procedures are suitable for an accurate and rapid quantitation of phosphatidylcholine. The sensitivity of the method based on phospholipase C and alkaline phosphatase is higher than that using phospholipase D. Quantitation of phosphatidylcholine at the nanomole level can be easily obtained using the first methodology. Membrane lipids were extracted from brain by the method of Folch et al. (J. Biol. Chem., 1957, 226, 497) and dissolved in CHCl3 - methanol (2:1). The solution was evaporated in vacuo and the lipid residue was dissolved in 0.1 M Tris - HCl buffer of pH 7.5 containing 0.3% of Triton X-100 and 0.4 mM ZnCl2. The suspension was injected into a stream (pH 6.5) of 30 mM CaCl2 containing 0.3% of Triton X-100 and 20 mM diethylbarbitone and passed through columns of phospholipase C immobilized on glass beads and of alkaline phosphatase and choline oxidase immobilized on glass beads before electrochemical detection with a vitreous-carbon electrode at +0.6 V. The calibration graph was rectilinear for 0.05 to 2 mM phosphatidylcholine. The sensitivity was higher than that of a flow injection method using phospholipase D.
Phosphatidylcholine Amperometry Electrochemical analysis Electrode

"Determination Of Proteolytic Enzymes By Flow Injection Analysis"
Anal. Biochem. 1991 Volume 192, Issue 1 Pages 70-73
Pierre Nicolas, Annick Lamy and Sylviane Reymond

Abstract: Quantitation of proteolytic enzymes using N-succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide has been adapted to flow injection analysis. This procedure has been developed using two different proteases: subtilisin and chymotrypsin. For both enzymes the influence of substrate concentration on spectrophotometric response has been studied. The assay is based on the merging zones technique combined with a washing step. Results are obtained in less than 15 s and samples may be run at a rate of 90/h with good reproducibility. A linear relation between peak heights and enzyme concentrations was observed for 0-0.15 Anson unit/liter of subtilisin and for 0-30 mg/liter of a commercial preparation of chymotrypsin. The method requires only small sample volumes, and the consumption of the chromogenic substrate is reduced to a minimum by using intermittent pumping. The flow injection system described for the determination of subtilisin (I) and chymotrypsin (II) is based on the merging-zones principle with intermittent pumping; N-succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide was used as substrate. High sampling rates were achieved by incorporating a second pump to flush the system with a wash solution Injection of samples into the buffer stream activated a pump that immediately delivered the substrate at the merging point and propelled the sample into the system. When the top of the peak had been recorded, the first pump was stopped and a second one was started, thereby delivering the wash buffer at a higher rate. The absorbance was monitored at 405 nm. The calibration graphs were rectilinear in the ranges 0.5 to 2 mM I and 0.75 to 2 mM II. Results were obtained in 15 s and samples could be analyzed at 90 h-1 with good reproducibility.
Enzymes, proteolytic

"Determinations Of Lactate And Lactate Dehydrogenase Activity In Serum With The Flow Injection Analysis System Involving Immobilized Enzyme Column And Chemiluminescence"
Anal. Biochem. 1991 Volume 193, Issue 1 Pages 112-117
Masayoshi Tabata, Masayuki Totani* and Takashi Murachi

Abstract: The methods for the highly sensitive flow injection analysis of lactate and lactate dehydrogenase (LDH) activity in serum using immobilized enzymes in column form and chemiluminescence detection which does not require a blank correction are described. The methods were based on the determination of chemiluminescence formed by the reaction of a luminol-ferricyanide mixture with hydrogen peroxide. This hydrogen peroxide was produced by the lactate oxidase (LOD) reaction from lactate, which was in serum or was produced by the action of LDH in serum. The action of LDH in a flow injection analysis system was performed for 2 min in an incubation coil placed parallel to the substrate-buffer line between the LOD column and the LOD/catalase column. Endogenous lactate in serum was removed by an immobilized LOD/catalase column prior to the action of LDH. The present method gave perfect linearity of the data up to 5.6 mmol/liter for lactate and 1840 IU/liter for LDH activity with satisfactory precision, reproducibility, and accurate reaction recoveries. The results from the lactate and LDH activity correlated satisfactorily with those obtained by other well-established methods. Serum was applied to a column of lactate oxidase - catalase immobilized on alkylamine glass beads. The eluate was incubated at 37°C for 2 min with phosphate buffer solution (pH 7.5) containing pyruvate and NADH. The mixture was applied to a lactate oxidase column and the eluate was subjected to chemiluminometric determination (J. Appl. Biochem., 1984, 6, 251). Lactate in serum was determined as above but the sample was applied directly on to the lactate oxidase column. The calibration graph was rectilinear for 5.6 mM lactate and the detection limit was 10 µM. For lactate dehydrogenase, the calibration graph was rectilinear for 1840 IU L-1 and the within- and day-to-day coefficient of variation were 3.0 and 3.9%, respectively. The results correlated well (r = 0.974) with those obtained on a Hitachi Model 726 discrete automatic analyzer. with use of pyruvate as substrate.
Lactate Enzyme, lactate dehydrogenase Blood Serum Chemiluminescence

"Flow Injection Analysis Of Lactose Using Covalently Immobilized β-galactosidase, Mutarotase, And Glucose Oxidase/peroxidase On A 2-fluoro-1-methylpyridinium Salt-activated Fractogel Support"
Anal. Biochem. 1991 Volume 194, Issue 1 Pages 16-24
Dyer Narinesingh, Valerie A. Stoute, Gershwin Davis and That T. Ngo

Abstract: Milk samples were analyzed for their lactose content using flow injection analysis and incorporating immobilized β-galactosidase or β-galactosidase/mutarotase and glucose oxidase/peroxidase bioreactors. These enzymes were immobilized, under mild conditions, on to a 2-fluoro-1-methylpyridinium salt-activated Fractogel support. The use of a phosphate buffer (0.15 M) was found to facilitate the rapid mutarotation of α-D-glucose and hence could obviate the need for the more expensive mutarotase. The chromogenic agents of choice for monitoring the reaction were 3-methyl-2-benzothiazolinone hydrazone and 3-dimethylaminobenzoic acid. Linearity was observed over the concentration range 16-160 µg/ml using lactose standards (r = 0.996). Between 30 and 40 milk samples/h can be analyzed. Comparisons are made with existing HPLC and alkaline methylamine methods for a range of milk matrices. The FIA method consistently gives the lowest standard deviations and coefficient of variation for the various milk matrices analyzed. Milk was incubated at 25°C for 10 min with concentrated HCl and then gravity-filtered. The filtrate was adjusted to pH 6.5 and mixed with 3-dimethylaminobenzoic acid and 3-methyl-2-benzothiazolinone hydrazone in phosphate buffer solution (pH 6.5). The mixture was subjected to flow injection analysis at 33°C on a column of β-galactosidase in series with a bioreactor of glucose oxidase - peroxidase, with detection at 590 nm. The calibration graph was rectilinear for 160 µg mL-1 of lactose and the coefficient of variation was 2.7 to 3.8% (n = 3). Between 30 and 40 samples per h can be analyzed.
Lactose Milk Spectrophotometry

"Reversed-phase Ion-pair High Performance Liquid Chromatography Method For Bovine Testicular Hyaluronidase Digests Using Post-column Derivatization With 2-cyanoacetamide And Ultra-violet Detection"
Anal. Biochem. 1991 Volume 196, Issue 1 Pages 183-191
Jeffrey A. Cramer and Leonard C. Bailey

Abstract: Bovine testicular hyaluronidase was incubated with hyaluronic acid hexasaccharide, at 37°C. After addition of the mobile phase [0.03 M tetrabutylammonium hydroxide (pH 9.0) - acetonitrile (4:1)], the mixture was subjected to HPLC on a column (15 cm x 4.1 mm) of Hamilton PRP-1 polymeric C18. The mobile phase flow rate was 0.8 mL min-1 and the eluant was mixed with 1% 2-cyanoacetamide in 0.2 M Na borate buffer (pH 9.0) for 2 min at 100°C before cooling and detection at 276 nm. The calibration graphs were rectilinear for 10 to 400 nmol of C-4 and C-6 oligomers and the coefficient of variation were 1.5 to 5.7%.
HPLC Spectrophotometry

"Determination Of Serum Cholinesterase Activity By Liquid Chromatography With Electrochemical Detection"
Anal. Biochem. 1991 Volume 196, Issue 2 Pages 377-384
R. Brent Miller and C. LeRoy Blank

Abstract: Serum was incubated at room temperature for 10 min in phosphate buffer solution (pH 7.2) containing ethylhomocholine, choline and acetylcholine. After addition of HClO4 and centrifugation, the supernatant solution was subjected to HPLC on a C18 (3 µm ODS) column (10 cm x 3.2 mm). The mobile phase (0.9 mL min-1) was Tris buffer solution (pH 7.5) containing acetic acid, tetramethylammonium chloride, Na octyl sulfate, NaN3, EDTA and acetonitrile. Post-column derivatization was effected with choline oxidase and acetylcholinesterase with electrochemical detection at 0.5 V vs. Ag - AgCl. The limit of detection was 3 pmol of choline or 0.1 µmol mL-1 h-1 of cholinesterase. The calibration graph was rectilinear for up to 269 µmol mL-1 h-1, with a coefficient of variation of 1.7%.
Enzyme, cholinesterase Blood Serum HPLC Electrochemical analysis

"Flow Injection Determination Of Proteins Using Enhanced Peroxyoxalate Chemiluminescence Applied To The Determination Of Immunoglobin G And Albumin In Serum"
Anal. Biochem. 1991 Volume 197, Issue 2 Pages 340-346
R. deLavalle and M. L. Grayeski

Abstract: The intensity of the chemiluminescence (CL) signal from an aqueous peroxyoxalate CL reaction can be significantly enhanced in the presence of various proteins with hydrophobic sites. A flow injection measurement for various hydrophobic proteins based on this CL enhancement was developed. The enhancement is due to the inclusion of the CL species in the favorable environment provided by the protein's hydrophobicity, which results in efficient light production. Various protein structures were evaluated; the degree of enhancement depends on the protein structure and CL reaction conditions. The CL enhancement measurement in the flow injection system is made after the introduction of the protein solution to the main phosphate buffer stream followed by the addition of the CL reagent streams: (1) hydrogen peroxide in water and (2) 8-anilino-1-naphthalene sulfonic acid and 4,4'-oxalylbis-(trifluoromethylsulfonylimino)ethylene bis(4-methyl morpholinium trifluoromethane sulfonate) in acetonitrile. Although prior separation of proteins is required before the measurement, the advantage of this approach is increased sensitivity without derivatization of the protein. The enhancement was demonstrated for several proteins, including antibodies, which suggests that this approach may be generally applicable to a variety of measurements, including immunoassay determinations. This CL enhancement was used to develop a simple and accurate flow injection measurement for the determination of albumin and IgG in human serum. A flow injection system (diagram presented) is presented for the determination of hydrophobic proteins, based on enhanced peroxyoxalate chemiluminescence. The protein sample was carried in the main phosphate buffer stream (pH 7.5) to mix with 4,4'-oxalyldisulfonylbis(trifluoromethylimino)diethylenebis-(4-methylmorpholinium trifluoromethanesulfonate) - 8-anilinonaphthalene-1-sulfonic acid reagent followed by H2O2. The resulting light emission was detected by a photomultiplier tube. Separation of proteins before measurement was achieved on open protein G - Sepharose 4 fast-flow columns. The method was applied to the development of an automated method to determine albumin and IgG in human serum.
Proteins Albumin Immunoglobulin G Serum Human Chemiluminescence

"Semi-automated Flow Injection Procedure For Acetylcholinesterase And Cholinesterase Activities"
Anal. Biochem. 1992 Volume 200, Issue 1 Pages 176-179
Ignacio L&oacute;pez Garc&iacute;a, Fernando Ruiz Abell&aacute;n and Manuel Hern&aacute;ndez C&oacute;rdoba

Abstract: A stopped-flow flow injection method is described (details and diagram of apparatus given) for the assay of cholinesterase (I) and acetylcholinesterase (II) based on the Ellman colorimetric method. For determination of I, serum (100 µL) was diluted to 10 mL with phosphate buffer solution For determination of II, 25 µL of blood was mixed with 1 mL of isotonic saline. The erythrocytes, pelleted by centrifugation, were haemolysed in 1 mL of water and the haemolysate was analyzed. Sample solution (50 µL) was injected into a carrier stream (0.1 mL min-1) comprising 2 mM acetylthiocholine and 0.2 mM 5,5'-dithiobis-(2-nitrobenzoic acid) in 0.1 M phosphate buffer solution (pH 7.2) and the resulting stream was passed through a 46 cm reaction coil at 37°C to a flow cell where the flow was stopped to allow detection at 410 nm. The calibration graphs for I and II were rectilinear and the FIA was significantly more sensitive than the manual procedure. A stopped-flow FIA adaptation of the classical Ellman's colorimetric procedure for the measurement of acetylcholinesterase or cholinesterase activity is described. The samples are injected into a flow analytical system which is provided with an electronic timer and an electrovalve in order to stop the flow when the sample is inside the measurement cell. In this way, the absorbance-time relationship is obtained with a savings of sample, time, and reagents.
Acetylcholinesterase Enzyme, cholinesterase Blood Serum Blood Spectrophotometry

"Determination Of Organophosphorus And Carbamate Insecticides By Flow Injection Analysis"
Anal. Biochem. 1992 Volume 200, Issue 1 Pages 187-194
Satish Kumaran* and C. Tran-Minh

Abstract: For determination of the cited groups of insecticides, substrate solution (0.5 mM acetylcholine in 2.5 mM HEPES buffer solution of pH 8.0 containing 20 mM MgCl2, 100 mM NaCl and 0.01% of gelatin; 250 µL) was injected into a carrier stream (0.45 mL min-1) of HEPES buffer solution and the mixture was passed through a 10 cm single bead string reactor containing acetylcholinesterase (I) immobilized on glass beads (0.5 to 0.75 mm). The H+ produced was detected by a pH electrode with a wall-jet entry to assay I activity. Insecticide sample solution was passed through the reactor for 15 min instead of the working buffer. The working buffer was then reintroduced into the carrier line and the substrate solution was injected again to determine I activity. The concentration. of insecticide was determined by the inhibition of enzyme activity. I was reactivated by passing 20 µM 2-pyridine aldoxime methiodide solution through the reactor for 15 to 20 min. The method was applied in the analysis of simulated seawater. Calibration graphs are presented for paraoxon and malathion. Detection limits ranged from 0.5 ppb for malathion to 275 ppb for bromophos-methyl. A flow injection system, incorporating an acetylcholinesterase (AChE) single bead string reactor (SBSR), for the determination of some organophosphorus (azinphos-Et, azinphos-Me, bromophos-Me, dichlorovos, fenitrothion, malathion, paraoxon, parathion-Et, and parathion-Me) and carbamate insecticides (carbofuran and carbaryl) is presented. The detector is a simple pH electrode with a wall-jet entry. Variations in enzyme activity due to inhibition are measured from pH changes when the substrate (acetylcholine) is injected before and after the passage of the solution containing the insecticide. The percentage inhibition of enzyme activity is correlated to the insecticide concentration. Several parameters influencing the performance of the system are studied and discussed. The detection limits of the insecticides ranged from 0.5 to 275 ppb. The determination of these compounds was conducted in Hepes buffer and a synthetic seawater preparation The enzyme reactor can be regenerated after inhibition with a dilute solution of 2-PAM and be reused for analysis. The immobilized enzyme did not lose any activity up to 12 weeks when stored at 4°C.
Insecticides Paraoxon Malathion azinphos-methyl Azinphos ethyl Bromophos Dichlorophos Fenitrothion Ethylparathion Methylparathion Carbofuran Carbaryl Sea Electrode

"Potentiometric Enzyme-amplified Flow Injection Analysis Detection System: Behaviour Of Free And Liposome-released Peroxidase"
Anal. Lett. 1989 Volume 22, Issue 5 Pages 1107-1124
Wu, T.G.;Bellama, J.M.;Durst, R.A.

Abstract: A three-channel peristaltic pump was used, with one channel pumping the carrier stream (0.5 M acetate buffer of pH 5.2, containing 1 M NaCl) and the other two, arranged to mix with each other and then with the carrier after sample injection, containing 4.8 mM H2O2 and the enzyme substrate, viz, 36 mM 4-fluoriphenol, both in acetate buffer solution Peroxidase in the sample catalyzed the oxidation of the substrate to F-, which was detected at an ion-selective electrode. Electrode fouling and slow recovery of electrode response were overcome with use of a separately pumped wash solution containing acetate buffer, 1 µM-NaF and 0.1% of Triton X-100. Sensitivity was increased by ~20%. To avoid loss of enzyme activity, sample solution were diluted with the acetate buffer containing 0.5% of gelatin. The reaction temperature was 25°C and the reaction coil was adjusted to give a reaction time of 3 min. The calibration graph covered the range from 0.2 to 3 miu of the enzyme per 100 µL injected; for 3 miu, the coefficient of variation was 1.5% (n = 16). A lower response, though still useful, was obtained when the enzyme was encapsulated in liposomes. In this instance, H2O2 also functioned as lysis reagent.
Enzyme, peroxidase Potentiometry Electrode

"Indirect Flow Injection Assays For Glucose-6-phosphate Dehydrogenase - Glucose-6-phosphate And Malate Dehydrogenase - L-malate Using Immobilized Bacterial Luciferase"
Anal. Lett. 1989 Volume 22, Issue 8 Pages 1861-1871
Nabi, A.;Worsfold, P.J.

Abstract: The assay involves the use of alkanal monooxygenase (FMN-linked) - oxidoreductase co-immobilized on CNBr-activated Sepharose 4B (0.1 g in a 6 cm x 2.5 mm coil). Reagent streams consisted of phosphate buffer solution (pH 7.5) containing (A) 1 µM-glucose-6-phosphate dehydrogenase (I), 0.1 mM NADP, 0.1 mM glucose 6-phosphate (II) and 0.1 mM dithiothreitol and (B) 1 µM-flavine mononucleotide, decaldehyde (10 ppm) and Triton X-100 (1 ppm). Bioluminescence was detected at 490 nm. For determination of II, carrier stream (A) contained II instead of I, carrier stream (B) was unchanged and the serial glass coils contained immobilized I and alkanal monooxygenase (FMN-linked) - oxidoreductase (0.1 g of each). Analogous methods were used to assay malate dehydrogenase (III) and determine L-malate (IV). Detection limits were 15 fmol of I, 10 nM-II, 30 fmol of III and 1 µM-IV; the coefficient of variation (n = 5) were 5%.
Enzyme, glucose-6-phosphate dehydrogenase Enzyme, malate dehydrogenase Glucose 6-phosphate l-Malate Bioluminescence

"Determination Of Hydrogen Peroxide Concentrations By Flow Injection Analysis Based On The Enhanced Chemiluminescent Reaction Using Peroxidase"
Anal. Lett. 1989 Volume 22, Issue 9 Pages 2037-2050
Eremin, S.A.;Vlasenko, S.B.;Osipov, A.P.;Eremina, I.D.;Egerov, A.M.

Abstract: Hydrogen peroxide solution (200 µL) is injected into a water carrier stream (0.8 mL min-1), and mixed with a reagent stream containing luminol (4 µg mL-1), 4-iodophenol (80 ng mL-1) and horse-radish peroxidase (40 µg mL-1) in 0.1 M Tris - HCl buffer (pH 8.4). The resulting mixture is passed on to a flow-through luminometer for measurement of chemiluminescence. The calibration graph is rectilinear for 1 (detection limit) to 100 µM-H2O2. For 6, 20 and 80 µM-H2O2, the coefficient of variation (n = 10) are 3.2, 2.0 and 0.8%, respectively. Zinc, Fe(III), Ni(II), Cu(II), Mn(II), Pb(II) and Co(II) interference could be tolerated to 10 µM. The sampling rate is 80 h-1.
Hydrogen peroxide Chemiluminescence

"Chemiluminescence Detection Of Amino-acids, Peptides, And Proteins Using Tris-(2,2'-bipyridine)ruthenium (III)"
Anal. Lett. 1990 Volume 23, Issue 2 Pages 195-210
Li He; Kathleen A. Cox; Neil D. Danielson

Abstract: Results are presented for the chemiluminescence detection of 21 amino-acids and some peptides and proteins; secondary amino-acids were particularly suitable for the proposed technique. By using flow injection analysis, detection limits ranged from 20 pmol (for proline) to 50 nmol (asparagine). The flow rate of the 1 mM tris-(2,2'-bipyridine)ruthenium(III) (I) reagent stream in 10 mM acetate buffer (pH 5.8) was maintained at 0.5 mL min-1; due to the short lifetime of the signal, the sample and I streams were mixed directly in the flow cell. The carrier mobile phase was acetonitrile - Na acetate buffer (27:73, pH 6) containing 10 mM heptanesulfonic acid (1 mL min-1). Amino-acids and peptides were dissolved in the mobile phase, proteins were dissolved in cold Na acetate buffer. A mechanism for the reaction of I with aliphatic amines is proposed. The separation of hydroxyproline and proline in synthetic collagen by HPLC with chemiluminescence detection with use of I is also presented.
Amino Acids Peptides Protein Chemiluminescence HPLC

"The Determination Of Total Serum Cholesterol By Flow Injection Analysis With Amperometric Detection"
Anal. Lett. 1990 Volume 23, Issue 3 Pages 425-435
Alexis Carpenter; William C. Purdy

Abstract: As a cleanup step, serum (0.25 ml) was passed through a column of Amberlite IRA-400 (Cl- form), the column was washed with 5 mL of 0.1 M phosphate buffer (pH 7.4), and the eluate was diluted to 25 mL with the carrier solution (phosphate buffer containing 0.1% of Triton X-100). This solution was analyzed in a flow injection system involving immobilized cholesterol (I) esterase and I oxidase, and detection of the H2O2 produced with a Pt electrode at +600 mV vs. Ag - AgCl. The thin-layer flow cell used is illustrated. The limit of detection was ~2.6 µM, and the calibration graph was rectilinear up to 31 mM. In analysis of three standard reference materials, the bias was -1.4 to -2.4%, and the coefficient of variation were 1.5% (n = 16).
Cholesterol Blood Serum Amperometry Electrode

"Combining Flow Injection Analysis And Immobilized Enzymes For Rapid And Accurate Determination Of Serum Glucose"
Anal. Lett. 1991 Volume 24, Issue 5 Pages 727-747
Narinesingh, D.;Stoute, V.A.;Davis, G.;Shaama, F.;Ngo, T.T.

Abstract: Glucose oxidase and peroxidase in an optimum activity ratio of 1.8:1 were co-immobilized on 2-fluoro-1-methylpyridinium-activated Fractogel (BioProbe International, Tustin, CA, USA) in 0.05 M phosphate coupling buffer of pH 8.0; the optimum loading was 0.72 mg mL-1 of protein. The resulting material was packed in Tygon tubing (2 cm x 2 mm) to provide a bioreactor, which was incorporated into a flow injection manifold (illustrated). The centrifuged serum sample was mixed (1:1) with 0.1 M phosphate buffer of pH 6.0 containing 0.02 M 3-methylbenzothiazolin-2-one hydrazone and 1.0 mM 3-dimethylaminobenzoic acid, and a 25 µL portion was injected into a flow (0.6 mL min-1) of 0.1 M phosphate buffer (pH 6.0). To compensate for background effects, the mixture was allowed to flow alternately through an enzyme reactor and a blank reactor, then passed through a detector operated at 590 nm. The optimum temperature and reaction time were 30°C and 50 s, respectively. The calibration graph of the difference signal vs. glucose concentration. was rectilinear up to 7 mg mL-1. The within-day coefficient of variation at 555 µg mL-1 was 2.0% (n = 15). The bioreactor retained 95% of its activity after storage in the buffer solution for 60 days. Results on a range of patients` samples correlated well with those obtained by a hospital method.
Glucose Serum Human

"Photometric And Fluorimetric Determination Of Creatine Kinase Activity By Using Co-immobilized Auxiliary Enzymes And An Open - Closed Flow Injection Manifold"
Anal. Lett. 1991 Volume 24, Issue 5 Pages 749-765
M. D. Luque de Castro; J. M. Fern&aacute;ndez-Romero

Abstract: The method involves reaction between creatine phosphate (I) and ADP catalyzed by creatine kinase (II), phosphorylation of D-glucose by the produced ATP catalyzed by hexokinase (III), and oxidation of the resulting D-glucose 6-phosphate by NADP+ catalyzed by glucose-6-phosphate dehydrogenase (IV); the NADPH formed is monitored photometrically at 340 nm or fluorimetrically at 470 nm (excitation at 340 nm). The serum sample is diluted with 0.1 M Tris - acetate buffer of pH 7.0 before injection into a stream of the same buffer, which is then merged with a stream containing ADP and I and passed through a reaction coil. Subsequently, the sample plug is passed repeatedly through an enzyme reactor containing III and IV co-immobilized on controlled-pore glass, the flow-through detector and two reaction coils; the series of peaks of increasing height thus obtained is used to provide fixed-time or reaction-rate measurements of II activity. Optimum values of the reaction variables are tabulated. Typical rectilinear ranges of calibration were 0.01 to 1.00 or 2.00 iu L-1 of II, and recoveries of added II (0.1 or 0.2 iu l-1) were quantitative.
Enzyme, creatine kinase Blood Serum Fluorescence

"Nanomolar-level Amperometric Determination Of ATP Through Substrate Recycling In An Enzyme Reactor In A FIA System"
Anal. Lett. 1991 Volume 24, Issue 8 Pages 1401-1417
Yang, X.;Pfeiffer, D.;Johansson, G.;Scheller, F.W.

Abstract: The method described involves substrate recycling by a three-enzyme system comprising pyruvate kinase, hexokinase and glucose-6-phosphate dehydrogenase and amperometric detection of the NADH produced. Sample solution (25 µL) is injected into a carrier solution of 0.05 M imidazole acetate buffer solution (pH 7.5) containing 10 mM potassium acetate, 5 mM magnesium acetate, 0.5 mM EDTA, 1 mM NAD+, 3 mM phosphoenolpyruvate and 1 mM glucose. The solution is passed through an enzyme reactor (prep. described) containing the cited enzymes and NADH was detected at 0 V vs. Ag - AgCl at a graphite electrode modified with 3,3'-bis~benzo[a]phenoxazin-7-ium, 5-amino-9-(diethylamino)~-1,4-NN'-diamidobenzene. The calibration graph was rectilinear for 5 nM to 5 µM-ATP. The detection limit was 1 nM-ATP. The coefficient of variation (n = 20) was 2.8% at 100 nM-ATP.
ATP Amperometry Electrode

"Synthetic IgG Receptor, Avid AL: Applications In Quantitative IgG Determination And In Immunoprecipitation"
Anal. Lett. 1991 Volume 24, Issue 11 Pages 2005-2015
Narinesingh, D.;Pope, A.;Khatter, N.;Ngo, T.T.

Abstract: Flow injection analysis and low-pressure liquid affinity chromatography are combined to give a method for the determination of IgG using the affinity gel Avid AL as IgG receptor. The cartridge was conditioned with PBS binding buffer (0.01 M Na2HPO4 - 0.15 M NaCl - 0.01% NaN3, pH 7.3) at 1.5 mL min-1 and human IgG standards were injected into the buffer stream at 0.5 mL min-1. The absorbance of unbound protein in the effluent was monitored at 280 nm. When the value returned to baseline, the column was eluted with 0.1 M acetic acid at 2.9 mL min-1 and the absorbance was monitored as before. Between each sample injection the column was conditioned with regeneration and binding buffer. At an optimized sample loop size of 150 µL, the calibration graphs were rectilinear up to 2.5 mg mL-1 (375 µg applied to column), the recovery was 99 to 101% and the coefficient of variation were 4.1 and 1.9% for 0.36 and 1.32 mg mL-1 of IgG, respectively (n = 12). The determination of IgG in human serum had a throughput rate of 10 min and a detection limit of 0.06 mg mL-1. The quantitative immuno-precipitation of soluble antibodies using Avid AL is also described.
Immunoglobulin G Serum Human LC

"Combining Low-pressure Liquid Affinity Chromatography And Flow Injection Analysis For The Quantitation Of Immunoglobulins"
Anal. Lett. 1991 Volume 24, Issue 12 Pages 2147-2155
Narinesingh, D.;Ngo, T.T.

Abstract: Sample (100 µL) was injected into a phosphate-buffered saline binding buffer stream (0.7 mL min-1) and passed through a Protein A affinity column (prepared as described by Ngo, Biotechnol., 1986, 4, 134). The absorbance of the effluent was monitored at 280 nm. When the absorbance peak returned to baseline any bound immunoglobulin on the column was eluted with 0.1 M sodium acetate of pH 3 (1.5 mL min-1) and the eluate was monitored at 280 nm. Calibration graphs were rectilinear up to at least 4 and 10 mg mL-1 of IgG in human and bovine standards, respectively. Recoveries were 95.8 to 100.6%.
Immunoglobulins LC

"In-stream Masking Of Aluminum In The Determination Of Fluoride By Flow Injection Potentiometry"
Anal. Lett. 1992 Volume 25, Issue 3 Pages 607-624
Davey, D.E.;Mulcahy, D.E.;Muggleton, T.J.;O'Connell, G.R.

Abstract: CDTA, EDTA, tiron, K tartrate, Na citrate, Na acetate and hexamine were assessed as masking agents by using a flow injection manifold with a flow injection flow path and a separate stopped-flow path. Solutions of Al-to-F ratios of 1:1 to 10:1 were investigated. Kinetics of F- release are presented. The use is recommended of tiron for fast release of F- at moderate Al loadings and of citrate otherwise. A citrate buffer of pH 4 is required. Ageing of solution does not affect complexation. The ability of selected complexing agents to mask aluminum and release fluoride for potentiometric determination instream has been assessed. The experimental manifold incorporated a cascade flow cell and comprised two flow paths, the first for conventional flow injection and the second enabling stopped-flow analyzes to be performed. For solutions containing equimolar quantities of Al and F at concentrations up to 10^-3 M in each ion, better than 90% fluoride recovery was achieved in 16s using Tiron. At higher aluminum loadings, fluoride was released more slowly, with citrate and DCTA being found to be more efficient than Tiron. At an Al:F ratio of 4:1 (10-3 M F-), relative release rates for fluoride over a 10 min period occurred in the following order: citrate > DCTA > Tiron > tartrate > EDTA. Acetate and hexamine buffers, often recommended as components in total ionic strength adjustment buffer formulations, were as effective as EDTA in releasing fluoride. Using an acetate buffer with citrate as the decomplexing agent slowed this release. Aged Al/F solutions responsed almost as quickly as fresh solutions to Tiron and DCTA, with small pH-related effects being observed for solutions 20 days old.
Fluoride Potentiometry

"Determination Of Some Tetracyclines By Spectrophotometry And Flow Injection Analysis"
Anal. Lett. 1992 Volume 25, Issue 10 Pages 1865-1876
Al Tamrah, S.A.;Alwarthan, A.A.

Abstract: Capsule contents (equivalent to 250 mg of tetracycline) were dissolved in water and the solution was diluted to 100 mL. Portions (200 µL) were analyzed by flow injection analysis in a manifold (described with diagram). Aqueous 1 mM sodium tungstate solution was mixed with a stream of 1 mM Na acetate buffer solution (pH 6). The sample solution were injected into the resulting stream and pumped (4.1 mL min-1) to a 25-cm reaction coil and then to the detector. Detection was at 380, 385 and 390 nm for oxytetracycline (I), doxycycline (II) and chlortetracycline (III), respectively. Calibration graphs were rectilinear from 1 µM (detection limit) to 10 mM I, II and III. A spectrophotometric method for the determination of some tetracyclines in bulk and pharmaceuticals is based on the reaction of the drug with sodium tungstate at pH 6 to form a yellow complex which can be determined spectrophotometrically. The complexes show absorption max. at 380, 385, and 390 nm for oxytetracycline, doxycycline, and chlortetracycline respectively.
Oxytetracycline Doxycycline Chlorotetracycline Pharmaceutical Spectrophotometry

"Flow Injection Analysis For Beryllium Determination With Chrome Azurol S As Chromogenic Agent"
Anal. Lett. 1992 Volume 25, Issue 12 Pages 2289-2304
Kutsera, L.;Ghaziaskar, H.;Lai, E.P.C.

Abstract: The reagent stream (1.0 mL min-1) containing acetate buffer (pH 4.15), 0.021% aqueous chrome azurol S (C. I. Mordant Blue 29) and 1,3-phenylenediamine dihydrochloride solution (3:35:62) was merged with sample solution (up to 25 µL) and the mixture was passed through a 48 in. reaction coil, packed with glass beads. The absorbance was measured at 570 nm. The calibration graph was rectilinear from 1 to 300 µg mL-1 of Be(II), with a detection limit of 0.1 µg mL-1. Interference from Ag(I), Ba(II), Cu(II) and Ni(II) was suppressed by adding Na2S2O3 and EDTA to the dye solution, but Al(III) and Fe(III) still interfered. A flow injection analysis system which employs a visible absorption detection is used for the determination of beryllium. Be(II) ions are detected by means of a complexation reaction between Be(II) and Chrome Azurol S as the chromogenic reagent. The reaction forms a stable 1:1 complex which appears dark red-violet. The optimum conditions for the determination are pH 4.15, 35% Chrome Azurol S, 3% buffer, 62% HCl and 1,3-phenylenediamine, flow rate of 1.0 mL/min, and wavelength at 570 nm. A concentration. limit of 0.1 µg/mL (or 2 ng in 25 µL of a sample injected) of Be(II) can be detected, and the linear dynamic range extends to 100 µg/mL. Some interference limits are established in the presence of EDTA and thiosulfate which are used as masking agents.
Beryllium Spectrophotometry

"Determination Of Enzymic Activities Based On An Optical Flow-through P-nitrophenol Sensor"
Anal. Lett. 1993 Volume 26, Issue 9 Pages 1847-1866
J. M. Fern&aacute;ndez-Romero; M. D. Luque de Castro; M. Valc&aacute;rcel

Abstract: The activity of β-glucuronidase (I) in serum was assayed by monitoring its catalysis of the conversion of a p-nitrophenyl derivative to p-nitrophenol (II) using an optical flow-cell. Sample solution in 100 mM dipotassium hydrogen phosphate buffer of pH 6.8 (buffer A) was injected into a carrier stream of buffer A which was merged with the stream of 0.32 mM p-nitrophenyl-β-D-glucuronide in buffer A. After passing through a 250 cm reaction coil and merging with a stream of 10 mM NaOH, the stream was passed through a 50 cm reaction coil, followed by a Dowex-1 anion-exchange resin support (chloride form; 2% cross-linked and 100-200 mesh) packed in the flow cell, where I was retained; elution was effected with 0.1 M ethylenedinitrilo tetra-acetic acid disodium salt using a switching valve. All flow rates were 1.7 ml/min. The retention-elution process was monitored continuously at 405 nm. The calibration graphs for I and II were linear from 0.1-20 iu/l and 0.1-5 µg/ml, respectively with corresponding RSD of 1.7-3.0% and 2.0-2.4%. The sampling rate was 20 samples/h with recoveries of 95-104%.
Enzyme, β-glucuronidase Sensor

"Flow Injection Analysis Of Chlorophenoxy Herbicides Using Photochemically Induced Fluorescence Detection"
Anal. Lett. 1996 Volume 29, Issue 8 Pages 1447-1461
Luisa F. Garcia; Sergei Eremin; Jean-Jacques Aaron

Abstract: Sample (300 µL) was injected into a water carrier stream and passed through a PTFE photoreactor (200 cm length) where it was irradiated for 90 s to 12 min via a low-pressure Hg lamp. Two modes of irradiation were utilized: (i) stopped-flow for all herbicides; and (ii) continuous-flow for 2-methyl-4-chlorophenoxyacetic acid, mecoprop and 4-(2-methyl-4-chlorophenoxy) butyric acid. The fluorescence of the resulting photoproducts was measured at 292 nm (excitation at 276 nm). Fluorescence intensity was increased by photolysis in a 50% methanol/pH 5 buffer solution. The sensitivity of the method was greater by the stopped-flow mode compared with the continuous-flow mode. Detection limits ranged from 23-98 ng/ml of chlorophenoxy herbicides. RSD were 0.7-2.7%. The method was applied to the determination of the herbicides in water; recoveries ranged from 96-108%.
Herbicides, chlorophenoxy Environmental Environmental Fluorescence

"Horse-radish-root-modified Carbon Paste Bioelectrode"
Electroanalysis 1989 Volume 1, Issue 1 Pages 43-48
Joseph Wang*, Meng Shan Lin

Abstract: The crushed root (0.11 g) was hand-mixed with 0.9 g of mineral oil (Aldrich) and then with 1.1 g of graphite powder. A portion of the paste was packed into the electrode cavity of a thin-layer detector, and the amperometric response (at -0.2 V vs. Ag - AgCl) to H2O2 (due to peroxidase activity) was evaluated in flow injection and continuous-flow systems with use of phosphate buffer media (pH 7.4) containing 1 mM o-phenylenediamine. The calibration graph was rectilinear up to 0.12 mM H2O2, the detection limit was 0.3 µM and the coefficient of variation (n = 15) at 1 mM was 1.4%. Response time was short (down to 11 s); oxidizable biological compounds did not interfere, but the response to riboflavine was similar to that to water. The electrode was also applied to the determination of glucose (in the presence of glucose oxidase) with a rectilinear response up to 60 µM, a detection limit of ~1.6 µM and a coefficient of variation (n = 20) at 80 µM of 2.6%.
Glucose Hydrogen peroxide Sensor Electrode

"Electroanalytical Method For Estimation Of Fish Freshness Using A Flow Injection System With Some Immobilized Enzyme Reactors"
Electroanalysis 1989 Volume 1, Issue 2 Pages 173-176
Toshio Yao*, Yoshihiro Matsumoto

Abstract: The method involves determination of (a) hypoxanthine (I) plus inosine (II) and (b) the sum of I, II, IMP and AMP; the ratio of the two peak currents is used in calculating a freshness index. The two-channel flow injection system incorporates reactors containing (i) AMP deaminase, (ii) alkaline phosphatase, and (iii) purine-nucleoside phosphorylase - xanthine oxidase, respectively, immobilized on LiChrosorb NH2 (details given). These catalyse (i) conversion of AMP into IMP plus NH3, (ii) conversion of the endogenous and enzymatically formed IMP into II plus phosphate, and (iii) reaction of II with phosphate to form I and oxidation of I to uric acid plus H2O2. The H2O2 is detected with a peroxidase - bovine serum albumin membrane electrode. The carrier solution is 50 mM glycine buffer of pH 7.0 containing 3 mM MgCl2, and Fe(CN)64- is used as mediator in the indicator reaction. Fifteen samples can be analyzed in 1 h.
Hypoxanthine Inosine Marine Electrode

"Simultaneous Enzymatic Determination Of Glucose And Ascorbic Acid Using Flow Injection Amperometry"
Electroanalysis 1990 Volume 2, Issue 2 Pages 147-154
Wojciech Matuszewski, Marek Trojanowicz *, Liliana Ilcheva

Abstract: Sample solution (10 µL) is injected into a carrier stream of water (2 mL min-1) that subsequently merges with a stream of phosphate buffer solution The mixed stream then divides into two; one passes directly to the amperometric detector, whilst the other passes through a reactor containing glucose oxidase immobilized on controlled-pore glass and then through a delay coil before passing to the detector. The resulting signal consists of two peaks, the first corresponding to oxidation of ascorbic acid (I) and the second to the oxidation of I and enzymatically produced H2O2. Results for synthetic mixtures of I and glucose (up to 20 and 100 mM, respectively) agreed well with expected values. Recoveries of I and glucose added to fresh citrus juice were 100 to 101.8% and 100 to 102.5%, respectively. The sampling rate is 20 h-1
Glucose Ascorbic acid Amperometry

"Flow Injection Analysis Of Hydrogen Peroxide Using A Horseradish Peroxidase-modified Electrode Detection System"
Electroanalysis 1990 Volume 2, Issue 4 Pages 303-308
Pilar Dominguez S&aacute;nchez, Paulino Tu&ntilde;&oacute;n Blanco, Jos&eacute; Maria Fern&aacute;ndez Alvarez, Malcolm R. Smyth*, Richard O'Kennedy

Abstract: Horse-radish peroxidase was adsorbed on to a vitreous-carbon electrode, which was then used in a flow injection system for determination of H2O2. Sample solution (20 ml) was injected into a stream (10 mL min-1) of deoxygenated 0.1 M phosphate buffer (pH 7.0) containing 0.1 mM quinol, and the quinone produced was detected at -0.30 V vs. Ag - AgCl. The calibration graph was rectilinear for 25 nM to 1 µM-H2O2, and the detection limit was 10 nM. The coefficient of variation (n = 7) was 1.3% for 0.3 µM. Possible interference was studied.
Hydrogen peroxide Electrode Electrode

"Amperometric Flow Injection Analysis Of L-glutamate Using An Immobilized-enzyme Reactor: Amplification By Substrate Recycling"
Electroanalysis 1990 Volume 2, Issue 7 Pages 563-565
Toshio Yao*, Naokazu Kobayashi, Tamotsu Wasa

Abstract: A column (5 mm x 4 mm i.d.) of LiChrosorb NH2 (10 µm) was activated by circulation of 5% glutaraldehyde solution in 0.05 M NaHCO3 for 1.5 h, then washed with 0.1 M phosphate buffer of pH 7.0 before co-loading with glutamate oxidase (8.5 iu) and alanine aminotransferase (118 iu) by circulation of the enzyme solution in the same buffer for 2 h at room temperature The resulting reactor was washed for 3 h with 0.1 M glycine buffer of pH 7.5, and was stored in the 0.1 M phosphate buffer at 5°C when not in use. The reactor was positioned between the injector and a Yanagimoto flow-through Pt electrode in the flow injection system described previously (Anal. Chim. Acta, 1990, 231, 121) for the determination of L-glutamate with use of 1 mM L-alanine in 0.1 M phosphate buffer (pH 7.2) as carrier solution and an applied potential of 0.5 V vs. Ag - AgCl. The reaction principle is described. At the optimum reactor temperature of 37°C and a flow rate of 0.3 mL min-1, the amplification factor was 24; the detection limit was 0.1 µM and the calibration graph was curvilinear. The method could also be used to determine 2-oxoglutarate.
l-Glutamate Amperometry Electrode Electrode

"Pineapple-tissue-based Bio-electrode For The Determination Of Hydrogen Peroxide"
Electroanalysis 1990 Volume 2, Issue 7 Pages 511-515
Meng Shan Lin, Sock Ying Tham, Garry A. Rechnitz*

Abstract: Ground pineapple core tissue (60 mg) was mixed with 0.94 g of carbon paste [graphite powder - mineral oil (11:9)] and the mixture was packed into an electrode body. The electrode was installed in a flow cell having a channel 0.127 mm deep (volume 15 µL), and its potential (vs. a Ag - AgCl micro-electrode) was controlled by a BAS model CV-1B cyclic voltammograph (Bioanalytical Systems, West Lafayette, IN) and monitored by a Keithley 169 multimeter (Keithley Instruments, Cleveland, OH). The assembly was applied for the determination of H2O2 by flow injection analysis with a carrier solution of 0.1 M phosphate buffer (pH 7.4) containing 1 mM o-phenylenediamine as H donor. The flow rate was 1.1 mL min-1 and the electrode potential was -200 mV. Response was sufficiently rapid to allow a sampling rate of >60 h-1 at 1 mM H2O2 and the detection limit was 2.1 µM. Catechol, dopa, dopamine, tryptophan and tyrosine (0.1 mM) interfered by causing 35% suppression of the current response for 0.2 mM H2O2 in the presence of o-phenylenediamine. The electrode response remained stable for 20 days.
Hydrogen peroxide Electrode

"FIA Analysis With Immobilized Oxidase/peroxidase Enzymes And Fluoride Electrode Detection"
Electroanalysis 1990 Volume 2, Issue 7 Pages 525-531
Wojciech Matuszewski, Marek Trojanowicz*, Mark E. Meyerhoff

Abstract: Details are given of flow injection manifold arrangements in which (a) glucose oxidase (I) and horse-radish peroxidase (II) are co-immobilized on nylon net or a polyester membrane, which is then mounted on a F--selective electrode; (b) the two enzymes are immobilized on controlled-pore glass beads in a single reactor preceding the electrode; or (c) I is immobilized on glass beads in a reactor following the sample injection valve in the carrier stream, and II is so immobilized in a reactor following the merge point of the carrier and reagent streams and preceding the electrode. The sample is a substance that is enzymatically (by I) oxidized to yield H2O2, and the H2O2 then reacts with a fluoriaromatic compound as reagent, catalyzed by II, to liberate F- for detection. Arrangements (b) and (c) showed greater catalytic efficiency and better sensitivity than arrangement (a); glucose could be determined at 0.1 to 10 mM at throughputs of >30 h-1 by using arrangement (b). Either 4-fluorianiline or pentafluoriphenol (5 mM) in acetate buffer of pH 5.5 could be used as reagent; incorporation of 10 or 20 µM-NaF in the reagent stream stabilized the baseline potential. The F- electrode was more selective then amperometric detection systems for H2O2.
Hydrogen peroxide Electrode Amperometry

"Highly Sensitive Determination Of L-lactate And Pyruvate By Liquid Chromatography And Amperometric Detection With Lactate Oxidase [lactate 2-monooxygenase] - L-lactate Dehydrogenase-co-immobilized Reactor Involving Amplification By Substrate Recycling"
Electroanalysis 1991 Volume 3, Issue 6 Pages 493-497
Toshio Yao, Naokazu Kobayashi, Tamotsu Wasa

Abstract: Pyruvate (I) and L-lactate (II) were determined in 10 µL of sample solution by flow injection reversed-phase HPLC on a column (25 cm x 4.6 mm) of ODS-T with 0.02 M phosphate buffer (pH 2.5) as mobile phase (0.4 mL min-1). Post-column reaction was carried out with 0.2 M phosphate buffer (pH 7.3) containing 0.5 mM NADH (0.25 mL min-1). The eluate was passed to the cited co-immobilized enzyme reactor where the I and II were recycled enzymatically to produce a large amount of H2O2. This was detected amperometrically at 0 V vs. Ag - AgCl by using a flow-through peroxidase electrode and mixing with 0.1 M phosphate buffer (pH 7.3) containing 0.5 mM K4Fe(CN)6 as mediator, pumped at 0.5 mL min-1. The detection limit was 0.02 pmol and the calibration graphs were rectilinear in the range 0.2 to 200 pmol for both I and II. The coefficient of variation was ~3.8% for 2 pmol of I or II (n = 5).
l-Lactate Pyruvate Amperometry HPLC Electrode

"Enzymic Determination Of Ethanol By Flow Injection Analysis Using A Kel-F Wax - Carbon-paste Electrode"
Electroanalysis 1991 Volume 3, Issue 7 Pages 625-630
Julie Wangsa, Neil D. Danielson

Abstract: The electrode was prepared from graphite powder and Kel-F wax in the wt. ratio 1.25:1. The graphite powder was first treated with hexane folowed by CHCl3, acetone and 6 M HNO3 and then dried at 100°C. This pre-treatment improved the reponse of the Kel-F wax - carbon-paste electrode by ~36% and improved electrode-to-electrode reproducibility. The graphite powder was added slowly with stirring to the melted Kel-F. After cooling and further mixing, a small amount of the paste was packed into the flow cell cavity, and the electrode surface was flattened and polished. The freshly prepared electrode was equilibrated for ~8 h by flow injection in the presence of buffer. Generally, the carrier solution used for standards and samples contained 20 iu mL-1 of alcohol dehydrogenase, 1.25 mM NAD+ and 2% (w/v) of polyoxyethylene glycol (to stabilize the enzyme) in 0.05 M Tris - HCl buffer (pH 8.0). Wine samples were diluted by a factor of 200 before analysis. The calibration graph was rectilinear from the detection limit of 0.44 mM to 33 mM.
Ethanol Wine Electrode

"Determination Of Amalgam-forming Metals By Anodic-stripping Voltammetry In Solutions Containing Dissolved Oxygen"
Electroanalysis 1991 Volume 3, Issue 9 Pages 925-928
Miloslav Kopanica, Vera Stara

Abstract: Graphite powder (1 g) was mixed with silica gel (0.1 g) and the blend was further mixed with ceresin wax at 60°C. The warm mixture was pressed into a PTFE cylinder (5 cm x 0.2 mm) to form an electrode. Such electrodes (with Ag - AgCl reference and Pt counter electrodes) were used for linear scan or differential-pulse voltammetry. The solution for anlaysis were prepared to contain 0.1 M acetate buffer (pH 4.5) and 1 mM Hg(NO3)2 (to form the Hg film). After each use, the Hg film was removed mechanically or electrochemically. No O removal was necessary. Rectilinear calibration graphs were obtained for 5 to 150 µM of Cu(II), Pb(II) and Zn(II) with deposition at -1.2 V for 10 s (unstirred). For 10 to 500 nM solution of, e.g., Pb(II), the supporting electrolyte was 0.3 M HCl, the Hg2+ concentration. was 10 µM and deposition was for 3 min at -0.9 V, with stirring. The film was removed at +0.5 V. At 10 to 50 nM, the deposition was increased to 6 min. The method was applied in the determination of Pb in used motor oil (after extraction with 3 M HCl).
Metals Lead Oil Electrode Voltammetry Sample preparation

"Flow Injection Monitoring And Analysis Of Mixtures Of Simazine, Atrazine And Propazine Using Filter-supported Bilayer Lipid Membranes"
Electroanalysis 1996 Volume 8, Issue 10 Pages 907-912
Dimitrios P. Nikolelis*, Christina C. Siontorou

Abstract: A microporous glass fiber disk (0.9 cm diameter) was mounted between two plastic layers having a central hole of 0.32 mm diameter. The whole was clamped between two Plexiglass chambers. One of the chambers contained a flow-through electrochemical cell, through which the carrier solution was pumped. A Ag/AgCl reference electrode was immersed in the waste of the carrier solution. The second chamber was equipped with a second Ag/AgCl reference electrode and a potential of 25 mV was applied between the two electrodes. Formation of stabilized BLM was effected by the method of Nikolelis et al. (Ibid.,1995, 7, 531 and Anal. Chem., 1995, 67 936), using solutions of lyophilized egg phosphatidylcholine and dipalmitoylphosphatidic aci d in hexane/ethanol (4:1). The carrier electrolyte solution consisted of 0.1 M KCl/10 mM HEPES buffer of pH 8 containing 1 mM calcium ions. The herbicide solutions were injected into the carrier stream and the resulting transient current signal was recorded. Calibration graphs were linear up to 1.4 ppm, 210 ppb and 300 ppb, respectively, for atrazine, simazine and propazine and the corresponding detection limits were 40, 8 and 20 ppb.
Atrazine Propazine Simazine Amperometry Electrode

"Multichannel Electrochemical Analyses Of Enzyme Reactions"
Electroanalysis 1996 Volume 8, Issue 8-9 Pages 748-752
Nahoko Kasai, Tomokazu Matsue *, Isamu Uchida

Abstract: A multichannel microarray electrode was fabricated by the Au-sputtering technique. The array was mounted in a flow-through cell equipped with an Ag/AgCl reference electrode and a Pt-wire counter electrode. Enzyme-catalyzed reactions involving horseradish peroxidase or xanthine oxidase were investigated in continuous-flow systems involving 0.1 M phosphate buffer of pH 7.5 or 60 mM carbonate buffer of pH 10.7, respectively, as the mobile phase (1 ml/min). The acquired data were used for the determination of the Michaelis constant and the molecular activity.
Enzymes Electrode

"Determination Of Tin(II) In Pharmaceuticals By Amperometric Oxidation After Complexation With Tropolone"
Electroanalysis 1996 Volume 8, Issue 8-9 Pages 789-794
K. Boutakhrit, G. Quarin, S. A. &Ouml;zkan, J.-M. Kauffmann *

Abstract: Dental gel (2 g) was extracted with hot 1 M HCl (20 ml) by sonication for 5 min, and a portion of the extract was diluted with 50 mM acetate buffer of pH 5.5 containing 0.1 mM tropolone. A 20 µL portion of the mixture was injected into an FIA system comprising 50 mM acetate buffer of pH 5.5 as the carrier solution. The solution was pumped (0.8 ml/min) through a reaction coil (30 cm x 0.2 mm i.d.) to an electrochemical cell equipped with a vitreous-carbon working electrode, an Ag/AgCl reference electrode and a Pt-wire counter electrode. The working electrode potential was set at +0.1 V. The response was linear over the range 0.25-20 µM, and the detection limit was 0.1 µM. None of the cations investigated interfered. Interference caused by some organic compounds usually present in radiopharmaceutical preparations is reported.
Tin(II) Dental Amperometry Electrode Sample preparation

"Detection Of Hydrogen Peroxide And Other Molecules Of Biological Importance At An Electrocatalytic Surface On A Carbon Fibre Microelectrode"
Electroanalysis 1997 Volume 9, Issue 2 Pages 102-109
Wilbur B. Nowall, Werner G. Kuhr*

Abstract: The electrocatalytic oxidation of hydrogen peroxide in solution at a modified carbon fiber electrode has been investigated. A simple electrochemical procedure has been developed to dramatically improve the voltammetry for the oxidation of peroxide, NADH, and several other species under steady state and fast scan voltammetry. The surface is generated by the electrochemical oxidation of NADH followed by exposure to peroxide. This procedure yields a surface which is sensitive to peroxide and stable in air for more than 90 days. This oxidation occurs at a potential such that it is easily discriminated from the analytes tested in this study. The tapered tip of a 32 µm diameter C fiber electrode was exposed to a stream of H2O-saturated air before and after polishing with 1000-grit sandpaper for 10 s. The tip was subjected to sine wave excitation from 0.1-1.1 V at 50 Hz, 600 mV bias and 38°C in phosphate buffer of pH 7.4 with ten 5 s injections of 100 µM-NADH followed by 1 mM H2O2. The injections were made at 1 min intervals. The electrode was used with phosphate buffer of pH 7.4 as supporting electrolyte and a Ag/AgCl reference electrode. At a scan rate 10 mV/s E1/2 for H2O2 was >1.1 V and there was no interference from NADH, ascorbate, dopamine, 3,4-dihydroxyphenylacetic acid and uric acid (E1/2 = +290, -25, +60, +110 and +225 mV, respectively) which could also be determined at the electrode. The electrode response to these compounds was also studied at 100 V/s at which calibration graphs were linear from the detection limit (1 µM) to 10 mM H2O2. The electrode was stable in air for >90 days and the response time was a few hundred ms. H2O2 may be useful as a diffusive redox mediator for immobilized oxidases. The electrode may also be useful for in situ and FIA applications. 50 References
Hydrogen peroxide Voltammetry Electrode

"Amperometry And Cyclic Voltammetry Of Tyrosine And Tryptophan-containing Oligopeptides At Carbon-fibre Microelectrodes Applied To Single-cell Analysis"
Electroanalysis 1997 Volume 9, Issue 3 Pages 203-208
Charina D. Paras, Robert T. Kennedy*

Abstract: The electrode was prepared by inserting a 9 µm carbon fiber inside a glass capillary which was then pulled to a fine tip. The carbon fiber was kept in place by immersing the capillary tip in epoxy. After polishing the electrode surface, FIA measurements were made at a potential of 0.8 V vs. SCE using 60 mM phosphate buffer of pH 7.4 as the carrier stream (1.5 ml/min). Melanocytes were isolated from the pituitary neurointermediate lobe and the peptide hormones were extracted, incubated (details given) and determined. The stability of the electrode was improved by electrochemical pretreatment involving potential scanning from -1.0 to +1.0 V at 300 V/s for 2 min. Selectivity of the peptides was achieved by cyclic voltammetry over the range 0 to 1.2 V using a scan rate of 800 V/s. The experimental parameters were optimized for the detection of the melanocyte-stimulating hormone secreted from single melanocytes during exocytosis.
Peptides, oligo Cell Amperometry Voltammetry Electrode

"Critical Comparison Of Metallized And Mediator-based Carbon-paste Glucose Biosensors"
Electroanalysis 1997 Volume 9, Issue 4 Pages 298-301
Joseph Wang*, Liang Chen, Jie Liu

Abstract: Metallized carbon-paste electrodes were prepared by packing a portion of a mixture of 40 mg of 5% Rh on carbon, 60 mg of mineral oil, 10 mg of glucose oxidase and the desired amount of PEI into the cavity of a PTFE electrode body. A steel screw was used to provide electrical contact. The mediator-based carbon-paste electrodes were prepared similarly except that 3 mg of 1,1'-dimethylferrocene was added to the paste. The characteristics of the two electrodes were compared by performing amperometric and cyclic voltammetric measurements in 50 mM phosphate buffer of pH 7.4 as supporting electrolyte with an Ag/AgCl reference and a Pt-wire counter electrode. The effect of the loading of PEI on the response of the electrodes is reported. Under optimum conditions, calibration graphs were linear up to 10 mM for the metallized electrode and 8 mM for the mediator-based electrode. The detection limits under flow injection conditions were 30 µM and 22 µM, respectively.
Glucose Fluorescence Biamperometry Amperometry Electrode Voltammetry Sensor

"An Amperometric Lactate Sensor Based On A NAD+-analogue And Lactate Dehydrogenase Coimmobilized On Reticulated Vitreous Carbon"
Electroanalysis 1997 Volume 9, Issue 7 Pages 523-526
Masoud Khayyami, Nuria Pe&ntilde;a Garcia, Per-Olof Larsson, Bengt Danielsson, Gillis Johansson *

Abstract: The sensor was fabricated from a reticulated vitreous C cylinder previously treated with 6 M HCl for 1 h. After rinsing successively with water and methanol, the dried cylinder was fitted into a glass tubing through which a 4% solution of 1-cyclohexyl-3-(2-morpholinoethyl)carbodi-imide metho-p-toluenesulfonate in 50 mM acetate buffer of pH 5.1 was circulated for 2.5 h at 0.2 ml/min. A solution containing 60 mg of lactate dehydrogenase and 60 mg of N6-[(2-aminoethyl)carbamoylmethyl]-NAD+ in the same acetate buffer was circulated for 3 h at 1-2°C. The response of the electrode for lactate was investigated by FIA. The electrode was placed into a piece of glass tubing, which contained an uncoated reticulated vitreous C cylinder as counter electrode; the two electrodes were separated from each other by means of a nylon net. Measurements were made with an applied potential of +400 mV relative to a Ag/AgCl reference electrode, which was placed downstream. The carrier solution consisted of 0.1 M phosphate buffer of pH 7.5. Response was linear up to 0.5 mM. The stability of the electrode was improved by the addition of 5 µM-Meldola blue to the carrier solution and by decreasing the applied potential to -0.1 V.
Lactate Amperometry Electrode Electrode Sensor

"Separation Of Free Amino-acids By Reversed-phase Ion-pair Chromatography With Column Switching And Isocratic Elution"
J. Chromatogr. A 1990 Volume 507, Issue 1 Pages 95-101
Mitsuko Hirukawa, Masako Maeda and Akio Tsuji, Toshihiko Hanai

Abstract: Seventeen free amino-acids were separated in 35 min by ion-pair chromatography using two columns: an Inertsil phenyl column (5 cm x 4.6 mm) for hydrophobic and basic amino-acids, and an Inertsil ODS-2 column (25 cm x 4.6 mm) for polar acidic and small amino-acids. Two eluents, viz. 50 mM Na phosphate buffer (pH 2.7) containing 6.5% of ethanol, 6.5% of acetonitrile and 0.11 M NaCl and the same buffer containing 25.6 mM Na dodecyl sulfate plus 12% of methanol and 94 mM NaCl, were used isocratically at 1 mL min-1. After post-column derivatization with phthalaldehyde, the amino-acids were determined by fluorescence at 450 nm (excitation at 340 nm); detection limits were 2 to 5 pmol for those with shorter retention times. Calibration graphs were rectilinear up to 500 pmol. The method was applied to bovine serum albumin hydrolysate, and results agreed well with literature values with results from LC.
Amino Acids Cow Serum HPLC Fluorescence

"Phthalaldehyde Post-column Derivatization For The Determination Of Gizzerosine In Fish Meal By High Performance Liquid Chromatography"
J. Chromatogr. A 1990 Volume 515, Issue 1 Pages 527-530
Hiroyuki Murakita and Takeshi Gotoh

Abstract: Fish meal (200 mg) was hydrolyzed with 2 mL of 6 M HCl at 110°C for 22 h, and the digest was filtered and evaporated. The residue was dissolved in 2 mL of 10 mM phosphate buffer (pH 2.6) and cleaned up on a Bond Elut C18 cartrige. Analysis was on a column (15 cm x 4 mm) of Shim-pack ISC-07/S1504, with 30 mM sodium borate buffer (pH 9.8) at 45°C as mobile phase (0.4 mL min-1). The eluate was mixed with 15 mM citric acid containing 0.08% of phthalaldehyde and 0.4% of poly(oxyethylene lauryl ether) (0.2 mL min-1), and detection was by fluorimetry at 410 nm (excitation at 320 nm). The limit of detection was ~0.5 ppm, and the calibration graph was rectilinear for 1000 ng. Recovery of 10 ppm was 98.2%, with a coefficient of variation (n = 5) of 1.5%. The method should be useful, but an unknown interferent was observed.
Gizzerosine Meal HPLC

"Determination Of Citrulline And Homocitrulline By High Performance Liquid Chromatography With Post-column Derivatization"
J. Chromatogr. B 1990 Volume 497, Issue 1 Pages 37-43
Ichiro Koshiishi, Yumiko Kobori and Toshio Imanari

Abstract: For determination of citrulline (I) in plasma, samples were extracted with trichloroacetic acid and subjected to HPLC on a column (15 cm x 4 mm) of TSK gel SCX with 50 mM citrate buffer containing 0.3 mM NaCl as mobile phase (0.4 mL min-1). The post-column colorimetric reaction was carried out with phthalaldehyde and N-(1-naphthyl)ethylenediamine; detection was at 520 nm. For homocitrulline (I) in urine, acidified samples were applied to a column of Amberlite CG-120 (H+ form) cation exchange resin; II was eluted with 0.1 M Tris - HCl buffer and subjected to HPLC as described. Both I and II were well separated with no interference from protein amino-acids or urea. Calibration graphs were rectilinear in the ranges 2.6 to 500 and 4.3 to 500 µM, respectively. Results indicated that the level of I in the plasma of uremia patients is higher than that in healthy plasma, and that II is excreted into healthy human urine but not into plasma.
Citrulline Homocitrulline Plasma Human Urine HPLC

"High Performance Liquid Chromatographic Determination Of Proteins By Post-column Fluorescence Derivatization With Thiamine Reagent"
J. Chromatogr. A 1990 Volume 518, Issue 1 Pages 141-148
Toshio Yokoyama, Toshio Kinoshita

Abstract: Proteins in the 70% (NH4)2SO4 fraction of Escherichia coli cell debris were separated on a column (30 cm x 7.5 mm) of TSKgel-G3000SW, with 0.1 M phosphate buffer (pH 7.5) containing 0.1 M Na2SO4 as mobile phase (0.8 mL min-1). The column eluate was mixed with a stream (0.2 mL min-1) of hypochlorite reagent (NaOCl solution containing 0.05 M phosphate buffer of pH 7.5 and 0.1% of Brij-35, adjusted to pH 7.5 and 0.8% available Cl, and chlorination was performed online at 70°C in a PTFE reaction coil. The reaction stream was then mixed online with thiamine reagent (0.2 mL min-1, comprising 4% NaNO2 - 0.02% of thiamine hydrochloride in 0.05 M phosphate buffer of pH 7.5), thiochrome was produced in a second reaction coil at 70°C, and the fluorescence generated was monitored at 440 nm (excitation at 370 nm). Calibration graphs for five proteins were rectilinear from 20 ng to 2 µg injected, and the detection limit of bovine serum albumin was 10 ng. Ionic surfactants did not interfere.
Fluorescence HPLC

"Liquid Chromatographic Determination Of Felypressin Using A Column-switching Technique And Post-column Derivatization"
J. Chromatogr. A 1990 Volume 521, Issue 1 Pages 141-147
Mats Svensson* and Kerstin Gr&ouml;ningsson

Abstract: The nonapeptide felypressin (I) was determined in a dental anaesthetic containing prilocaine hydrochloride after cartridge cleanup. The cartridge (25 mm x 4 mm) packed with Superspher 60 RP-8 (4 µm; Merck) was connected in series with the analytical column (5 cm x 4 mm) of Superspher 60 RP-8e (4 µm). During cleanup (14 min) the mobile phase (1 mL min-1) of phosphate buffer (pH 6.0) - acetonitrile (22:3) was fed through the cartridge only, then flow was switched through cartridge and column and solvent component ratio was changed to 4:1 for the analytical phase (9 min). Post-column derivatization was by addition of 0.03% (w/v) of fluorescamine and 0.1% (v/v) of Brij 35 in acetonitrile (0.25 mL min-1) and fluorimetric detection was at 470 nm (excitation at 390 nm). For determination of I in Citanest Octapressin injection solution, coefficient of variation were 1.7% and mean recovery was 101.8% (n = 6). Life of the cleanup cartridge was ~100 determinations.
Felypressin Anaesthetic LC Fluorescence

"Preconcentration Of Divalent Trace Metals On Chelating Silicas Followed By Online Ion Chromatography"
J. Chromatogr. A 1991 Volume 541, Issue 1-2 Pages 443-452
D. Chambaz, P. Edder and W. Haerdi

Abstract: For online pre-concentration of the cited metals, a titanium pre-column (1.3 cm x 1.7 mm or 5 cm x 2 mm) of ethylenediamine triacetate-bonded silica (prep. described) was used, with adsorption from a mobile phase of 0.1 M acetate buffer (pH 5.0) and desorption with 0.1 M HNO3. The eluate was adjusted to pH 3.0 with 0.5 M tartaric acid for use as mobile phase for HPLC on a column (30 cm x 4 mm) of Nucleosil 10SA with post-column derivatization with 4-(2-pyridylazo)resorcinol in a PTFE coil (3 m x 0.5 mm) and detection at 500 nm. Calibration graphs for Co, Ni, Cu, Zn, Cd and Pb were rectilinear from 3 nM to 3 µM; the method was applied to river water.
Cadmium Cobalt Copper Lead Nickel Zinc River HPIC Spectrophotometry

"Analysis Of Paralytic Shellfish Poisons By Capillary Electrophoresis"
J. Chromatogr. A 1991 Volume 542, Issue 2 Pages 483-501
P. Thibault, S. Pleasance and M. V. Laycock

Abstract: Underivatized saxitoxin (I) and neosaxitoxin (II) were separated by capillary electrophoresis on a fused-silica capillary column (90 cm x 50 µm) with either sodium citrate buffer (20 mM, pH 2) or acetic acid (0.1M, pH 2.9); detection was at 200 nm. Sample introduction was performed using either hydrodynamic or electrokinetic injections. Identification of the electrophoretic peaks was confirmed by MS using ionspray ionization and by HPLC with fluorescence detection. The limits of detection were 15 and 18 pg for I and II, respectively; improvements in sensitivity are likely to be achieved using pre- or post-column fluorescent derivatization. Results for dinoflagellates and scallops are presented and are reproducible in terms of both migration times and sensitivity, comparing well with existing techniques.
Saxitoxin Neosaxitoxin Marine HPLC Electrophoresis Fluorescence Mass spectrometry

"Sensitive Liquid Chromatographic Determination Of Alkyl-, Nitro- And Chlorophenols By Pre-column Derivatization With Dansyl Chloride, Post-column Photolysis And Peroxyoxalate Chemiluminescence Detection"
J. Chromatogr. A 1991 Volume 553, Issue 1 Pages 345-356
P. J. M. Kwakman, D. A. Kamminga and U. A. Th. Brinkman, G. J. De Jong

Abstract: Aqueous phenol-containing solution was adjusted to pH 12 with 1 M NaOH, treated with aqueous tetrabutylammonium bromide and dansyl chloride in CH2Cl2. After mixing, a portion of the organic phase was applied to an amino-bonded SPE column and the dansyl derivatives were eluted with CH2Cl2. The eluate was evaporated to dryness and the residue was dissolved in aqueous 50% methanol. A portion of the solution was analyzed by LC on a column (20 cm x 3.2 mm) of LiChrosorb RP-18 (3 µm) with methanol - imidazole buffer of pH 7 as eluent (gradient elution details given). After chromatography, the dansyl derivatives were irradiated in a photochemical reactor (cf. Scholten et al., ibid, 1980, 199, 239) before 2-nitrophenyl oxalate - H2O2 in acetonitrile were added to the column eluate (for chemical excitation); peroxyoxalate chemiluminescence detection at 470 nm (excitation at 340 nm) was used. The method was applied to determine several phenolic compounds in surface water; detection limits were 0.01 to 0.1 ng mL-1.
Phenols, alkyl Phenols, chloro Phenols, nitro Surface Chemiluminescence LC

"Comparative Studies On The High Performance Liquid Chromatographic Determination Of Thiamine And Its Phosphate Esters With Chloroethylthiamine As An Internal Standard Using Pre- And Post-column Derivatization Procedures"
J. Chromatogr. A 1991 Volume 558, Issue 1 Pages 115-124
S. Sander, A. Hahn, J. Stein and G. Rehner*

Abstract: Chloroethylthiamine was added to tissue before threefold ice-cold homogenization in 10% trichloroacetic acid and centrifugation. Supernatant solution were combined and buffered to pH 4.5 with Na acetate. Derivatization was with K3Fe(CN)6 in aqueous NaOH (0.1% in aqueous 15% pre-column or 0.02% in aqueous 10% post-column) to form thiochromes for fluorimetry at 450 nm (excitation at 365 nm). HPLC of thiochromes was in a column (25 cm x 4.6 mm) of ODS-Hypersil (5 µm) with a mobile phase (1.2 mL min-1) of aqueous 25 mM potassium phosphate (pH 8.4) - methanol [17:3 gradient in 6 min to 1:1 (held 5 min)] or HPLC before derivatization was in a column (12.5 cm x 4.6 mm) of ODS-Hypersil (3 µm) with a mobile phase [5 mM Na hexane sulfate in 50 mM Na citrate (pH 4.0) - methanol (19:1 held 2 min, then 3-min gradient to 1:1, held 3 min)]. Similar results in nmol g-1 range were obtained by both methods for thiamine and its mono- and pyro-phosphates. Pre-column derivatization was easier but reagent reactivity caused on-column problems; a chemically inert derivatization pump was essential.
Thiamine monophosphate HPLC Fluorescence

"High Performance Liquid Chromatographic Analysis Of Diastereomers And Enantiomers Of Pyrroloisoquinoline Antidepressants"
J. Chromatogr. A 1991 Volume 588, Issue 1-2 Pages 348-351
Rekha D. Shah and Cynthia A. Maryanoff*

Abstract: The diasteriomeric purity of three different sets of isomers of pyrroloisoquinoline compounds in a reaction mixture was determined by reversed-phase HPLC on a column (25 cm x 4.6 mm) of Supelcosil-LC-18-DB (5 µm) with 0.01 M triethylamine buffer of pH 6.2 - acetonitrile (1:3) as mobile phase (2 mL min-1) and detection at 220 nm. Enantiomeric purity was determined by normal-phase HPLC on a column (25 cm x 4.6 mm) of Chiralcel OD (10 µm) with hexane - propan-2-ol (4:1) containing 0.1% of triethylamine as mobile phase (1 mL min-1) and detection at 220 nm. Neither method required pre- or post-column derivatization. Responses were rectilinear for 0.01 to 0.50 mg mL-1 (for diastereoisomeric purity) and 0.01 to 0.15 mg mL-1 (for enantiomeric purity).
Antidepressants HPLC

"Indirect Chemiluminescence Detection Of Amino-acids Separated By Capillary Electrophoresis"
J. Chromatogr. A 1996 Volume 736, Issue 1-2 Pages 247-254
Shao-Yen Liao and Chen-Wen Whang*

Abstract: An indirect chemiluminescence (CL) detection method for amino acids following capillary electrophoretic separation is described. Since amino acids can form stable complexes with Cu(II) and complexed Cu(II) is a much poorer catalyst for the CL reaction between luminol and H2O2, indirect detection is based on the measurement of the decreasing catalytic activity of Cu(II) in the presence of amino acids. The degree of CL suppression is proportional to the amino acid concentrations. The optimal conditions for the indirect CL detection were determined with regard to buffer composition and reagent concentration. However, the sensitivity of the indirect CL signal to buffer additives limits the buffer composition and, hence, the resolution of complex mixtures. Due to the sigmoid nature of the calibration curves, a limited working range (less than or equal to 2 orders of magnitude) was generally obtained. Detection limits for the unlabeled amino acids were in the 100-400 fmol range, depending upon the magnitude of the complex formation constants. Precision was between 3 and 6%. Applicability of this method to the analysis of amino acids in relatively simple samples was demonstrated.
Amino Acids Chemiluminescence Electrophoresis

"Direct Determination Of Biogenic Amines In Wine By Integrating Continuous-flow Clean-up And Capillary Electrophoresis With Indirect UV Detection"
J. Chromatogr. A 1998 Volume 803, Issue 1-2 Pages 249-260
Lourdes Arce, AngelR&iacute;os and Miguel Valc&aacute;rcel*

Abstract: A flow injection manifold for automating the determination of biogenic amines in wine using capillary electrophoresis (CE) with indirect UV detection was developed. The ensuing method involves clean-up and solid phase extraction (SPE) of the target analytes in the sample. Various treatments involving different SPE minicolumns were tested and compared. The C18 minicolumn was chosen to concentrate the amines following addition of ammonium chloride and ammonium hydroxide as buffer to neutralize them. Addns. of amine standards were used to determine recoveries. Biogenic amines can be separated and detected after SPE with limits of detection in the range 0.05-0.1 µg mL-1 by using 4 mM copper(II) sulfate, formic acid and 18-crown-6 as running buffer. All the amines studied are eluted within 15 min under the optimum conditions established. The overall process was successfully used to identify biogenic amines in various types of wine from different Spanish regions.
Amines, biogenic Wine Electrophoresis Spectrophotometry

"High Performance Liquid Chromatographic Determination Of Substance P-like Arginine-containing Peptide In Rat Brain By Online Post-column Fluorescence Derivatization With Benzoin"
J. Chromatogr. B 1989 Volume 490, Issue 1 Pages 301-310
Masahiro Ohno, Masaaki Kai and Yosuke Ohkura

Abstract: Brain homogenate, containing [D-Phe11]neurotensin as internal standard, was deproteinized by centrifugation with acetone. The supernatant solution was mixed with 1 M NaHCO3 (0.22 ml) and 0.1 M Na2EDTA (0.5 ml), the ppt. was removed by centrifugation, the acetone was evaporated off and the residue was dissolved in water (2 ml). The solution was cleaned up on a Bond Elut C18 cartridge (details given), the eluate was evaporated and the residue was dissolved in water. A portion (100 µL) of solution was analyzed by HPLC on a column (20 cm x 4 mm) of TSKgel ODS-120T (5 µm) with gradient elution (1 mL min-1) with acetonitrile - 0.3 M sodium phosphate buffer (pH 2.3) - water. The eluate was mixed with a stream (1 mL min-1) of 2 mM benzoin - 1.6 M KOH - 0.7 M 2-mercaptoethanol in a PTFE coil (15 m x 0.3 mm) at 76°C and then with a stream (0.4 mL min-1) of 0.5 M Tris - 2.1 M HCl before fluorimetric detection at 435 nm (excitation at 325 nm). The calibration graph was rectilinear up to 320 pmol of substance P. The detection limit for substance P-like arginine-containing peptide was 580 fmol mg-1 of protein.
Arginine Peptides Brain HPLC Fluorescence

"High Performance Liquid Chromatographic Determination Of Clenbuterol And Cimaterol Using Post-column Derivatization"
J. Chromatogr. B 1991 Volume 564, Issue 2 Pages 537-549
Dirk Courtheyn*, Carlo Desaever and Roland Verhe

Abstract: Animal tissues, faeces and feeding-stuffs were extracted with dilute 0.5 M HCl saturated with ethyl acetate; the resulting extracts or liquid samples, e.g., urine, plasma, blood and bile were purified on Chem Elut CE 120 columns and eluted with toluene - CH2Cl2. The eluate was mixed with 0.1 M HCl, ultrasonicated and centrifuged before a portion of the mixture was analyzed by HPLC on a column (15 cm x 4.6 mm) of Nova-Pak C18 (4 µm) with 25 mM sodium dodecyl sulfate and 0.02 M anhydrous acetic acid buffer of pH 3.5 containing 1 M NaOH - acetonitrile (53:47) as mobile phase (1.3 mL min-1). The eluate was derivatized with use of three reagents (details given) before the absorbance was measured at 537 and 493 nm for cimaterol and clenbuterol, respectively. Detection limits for liquid and solid samples were 0.1 ng mL-1 and 0.2 ng g-1, respectively. Results agreed well with those obtained by high performance TLC and GC - MS.
Cimaterol Clenbuterol Bile Blood Blood Plasma Urine Faeces Biological tissue Feed HPLC Spectrophotometry

"Determination Of Ampicillin In Biological Fluids By Coupled-column Liquid Chromatography And Post-column Derivatization"
J. Chromatogr. B 1991 Volume 567, Issue 1 Pages 121-128
K. Lanbeck-Vall&eacute;n*, J. Carlqvist and T. Nordgren

Abstract: Plasma (0.5 ml) was mixed vigorously with 70% trichloracetic acid in Na2PO4 - citric acid buffer solution, pH 5.4 (200 µL) and centrifuged at 2400 g for 10 min. A portion (400 µL) of the supernatant liquid was mixed with 1 M NaOH (85 µL) to adjust the pH to ~5. Paediatric plasma (100 µL) was treated in a similar manner. Urine was diluted with 0.5 M Na2PO4 - citric acid buffer solution of pH 4.85. Portions (20 to 100 µL) of the solution were analyzed by HPLC on a column of Perkin Elmer 3 x 3 (3 µm) connected in series with a column (10 cm x 4.6 mm) of Microspher C18 (3 µm) with elution (1 mL min-1) with 17% methanol in phosphate buffer solution of pH 7.4 containing 1 mM Na hexylsulfate for the first column and 35% methanol (for plasma) or 30% methanol (for urine) in phosphate buffer solution of pH 7.4 for the second column. The eluate from the second column was reacted with fluorescamine (0.16 mg mL-1) in acetonitrile and the fluorescence was measured at 470 nm (excitation at 372 nm). Detection limits were 14 nM and 570 nM-of ampicillin in plasma and urine, respectively.
Ampicillin Blood Plasma Urine HPLC Fluorescence

"High Performance Liquid Chromatographic Determination Of Branched-chain 2-oxo-acids In Serum Using Immobilized Leucine Dehydrogenase As Post-column Reactor"
J. Chromatogr. B 1989 Volume 497, Issue 1 Pages 236-242
Nobutoshi Kiba, Masakazu Muto and Motohisa Furusawa

Abstract: Serum (0.2 ml), containing 20 µL of 0.3 mM 2-oxohexanoic acid as internal standard, was passed through a membrane filter (mol. wt. 30,000), and a 30 µL portion of filtrate was injected on to a column (15 cm x 4 mm) and guard column (1 cm x 4 mm) of Capecell 120 C18 (5 µm), at 40°C. The mobile phase (0.8 mL min-1) was 0.5 M NH4Cl - NH3 buffer of pH 8.5 containing 5 µM-NADH. The eluate was passed through a column (5 cm x 4 mm), also at 40°C, of immobilized leucine dehydrogenase before fluorimetric detection of 2-oxo-acids, e.g., 2-oxo-butyric acid and 2-oxo-pentanoic acid. Calibration graphs were rectilinear in the range 4 to 55 µM. Detection limits were 1 µM. Recoveries were 53.5 to 56.5%, and coefficient of variation were 1.7 to 2.4% (n = 5). Results are compared with those of a direct HPLC method.
Acids Blood Serum HPLC Fluorescence

"Comparison Of Different Flow Injection Approaches To The Automatic Determination Of Enzymic Activity"
J. Pharm. Biomed. Anal. 1989 Volume 7, Issue 3 Pages 295-302
J. M. Fernandez-Romero*, M. D. Luque de Castro and M. Valcarcel

Abstract: A comparative study of normal, stopped-flow and open-closed flow injection assay of lactate dehydrogenase is presented (details given). Optimum pH, temp., buffer solution, NADH concentration. and flow rate were 7, 40°C, 0.1 M K2HPO4, 1.0 mM NADH and 1.64 mL min-1, respectively, for all three methods. Pyruvate concentration, reactor length and injected volume were variable. Advantages, reproducibility and sensitivity of the methods are discussed. Three configurations based on the principles behind flow injection analysis (FIA) are proposed for the automatic determination of enzymatic activity. The proposed approaches are normal, stopped-flow and open-closed FIA. The comparative study of the methods developed from these approaches allows the establishment of the scope of the application of each, with inherent advantages and disadvantages.
Enzyme, lactate dehydrogenase Spectrophotometry

"Determination Of Penicillin In Pharmaceutical Formulations By Flow Injection Analysis Using An Optimised Immobilised Penicillinase Reactor And Iodometric Detection"
J. Pharm. Biomed. Anal. 1990 Volume 8, Issue 1 Pages 49-60
M. A. J. van Opstal, R. Wolters, J. S. Blauw, P. C. van Krimpen, W. P. van Bennekom and A. Bult

Abstract: An automated assay for the determination of penicillin in formulations suitable for use in pharmaceutical quality control is presented. The method is based on the classical iodometric penicillin assay which is incorporated in a flow injection analysis (FIA) system. The required hydrolysis is performed online by using an immobilized penicillinase reactor. Packed-bed and single-bead-string enzyme reactors are compared. It turns out that a packed-bed penicillinase reactor (10 cm x 1.5 mm i.d.) provides complete hydrolysis within short residence time, while only little back-pressure is generated. This enzyme reactor is stable for at least 9 months. Enzymatic hydrolysis of the β-lactam ring results in the formation of the corresponding penicilloic acid, which consumes iodine. The iodine consumption is determined colorimetrically by measuring the decrease of the absorbance of the blue colored iodine/starch complex. The optimum reactor length and flow rate for the colorimetrical detection reaction are determined. The optimized method is applied to the assay of penicillin in formulations and the results are compared with the 'true' results obtained with a reference method: a mercurimetric titration. The reliability of the flow injection method is evaluated quantitatively by determining the maximum total error (MTE). The reliability is shown to be highest when measuring at a 0.3-mM level. Eight formulations including capsules, tablets and injectables containing penicillin G, amoxicillin or flucloxacillin are assayed. The MTE does not exceed the 6% level and the most probable MTE is between 1.5 and 3.5%. A 30 µL portion of aqueous penicillin (I) solution was injected into a carrier stream (0.3 mL min-1) of 0.2 M potassium phosphate buffer (pH 6.5) and pumped into a packed-bed immobilized β-lactamase reactor (10 cm x 1.5 mm). The penicilloic acid formed was passed into a single-bead-string reactor (25 cm x 1.5 mm) and mixed with a reagent stream (0.7 mL min-1) of aqueous 0.15% starch solution - (0.5 mM I in 0.5 mM KI) - phosphate buffer (1:1:3). The decrease in absorbance of the blue iodine - starch complex was measured at 590 nm. The calibration graph was rectilinear from 0.1 to 0.5 mM I; the detection limit was 0.025 mM. Results compared well with those obtained by mercurimetric titration. Results are presented for the determination of I in eight formulations, including capsules, tablets and injectables.
Penicillin Pharmaceutical Pharmaceutical Pharmaceutical Spectrophotometry

"Enzymatic Flow Injection Method For Determination Of Formate"
J. Pharm. Biomed. Anal. 1990 Volume 8, Issue 8-12 Pages 991-994
F. Ortega*, M. Ballesteros, J. I. Centenera and E. Dom&iacute;nguez

Abstract: Formate dehydrogenase was immobilized on controlled pore glass (CPG-10; pore diameter 51.5 nm, particle size 37-74 µm) after silanization of the glass with 2-aminopropyl triethoxy xilane and activation with glutaraldehyde. The immobilized enzyme was packed into Plexiglass reactors with polypropylene nets at each end. The flow injection apparatus (diagram given) consisted of a pump, an injection valve, the immobilized enzyme unit reactor, a UV detector and a recorder. Sample (50 µL) was injected into a carrier solution (0.5 mL min-1) of 2 mM NAD+ in 0.1 M phosphate buffer (pH 7) and the NADH formed was determined from the absorbance at 340 nm. The optimum temperature was 30°C. Response was rectilinear from 5 to 80 and from 50 to 2000 µM-formate with use of 400- and 50 µL reactors, respectively. The coefficient of variation were 5%. The method was applied in the analysis of commercially available carbohydrate solution for parenteral use.
Formate

"Kinetic Determination Of Aspartate Aminotransferase In Human Serum With A Flow Injection/multidetection System"
J. Pharm. Biomed. Anal. 1991 Volume 9, Issue 9 Pages 679-684
J. M. Fern&aacute;ndez-Romero* and M. D. Luque De Castro

Abstract: Photometric-kinetic methods for the determination of activity of aspartate aminotransferase are proposed. The flow injection manifold used for this purpose includes a selecting valve which allows the sample to be trapped in a closed circuit where a solid reactor housing an auxiliary enzyme and a conventional single detector allows a multipeak recording to be obtained for each sample. This record represents a typical kinetic curve from which much information can be obtained to develop fixed-time and reaction-rate methods for the determination of the analyte based on its catalytic action on the L- aspartic acid-2 oxoglutarate system. The linear range is found to be between 1 and 500 U l-1, with relative standard deviation less than 1%. The utility of the methods is illustrated by the determination of the analyte in human serum from healthy and sick individuals. Sample was injected into a stream of 0.1 M Tris - HNO3 buffer of pH 7.5 which merged successively with 6 mM 2-oxoglutarate in Tris buffer and 200 mM aspartic acid and 1 mM NADH also in Tris buffer. The mixture passed through the manifold (illustrated) to a selecting valve which trapped the reacting plug in a closed circuit. The plug passed through an enzymatic reactor (5 cm long) containing malate dehydrogenase immobilized on controlled-pore glass and the decrease in absorbance was monitored at 340 nm. The calibration graph was rectilinear for 1 to 500 U L-1 of aspartate aminotransferase; coefficient of variation was 1% for 30 U l-1.
Enzyme, aspartate aminotransferase Serum Human

"Automated Flow Injection Technique For Use In Dissolution Studies Of Sustained-release Formulations: Application To Iron(II) Formulations"
J. Pharm. Biomed. Anal. 1994 Volume 12, Issue 5 Pages 635-641
Constantinos A. Georgioua, Georgia N. Valsamib, Panayotis E. Macherasb and Michael A. Koupparisa,*

Abstract: Formulations were dissolved in 0.1 M HCl (procedure described), screened and 100 µL aliquots injected into the 0.1 M HCl carrier (0.66 ml/min) and mixed with 0.1% ferrozine, [3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine monosodium salt] containing ascorbic acid (anti-oxidant) in 0.5 M acetate buffer of pH 3.7, (2.62 ml/min) and the mixture passed through a reaction coil (100 cm). The Fe(II) complex (ε = 28 000) was mixed with further acetate buffer (3.96 ml/min) in a second coil (100 cm) and absorbance measured at 562 nm. A computer program was used to optimise the system and chemical parameters with respect to throughput and sensitivity. The calibration graph was linear for 1-130 ppm of Fe(II). Two calibration graphs were constructed: absorbance at maximum peak height (1-70 ppm); and from absorbance at the descending part of the FIA peak (2-130 ppm). RSD was 3% (n = 3). Recoveries from commercial formulations ranged from 99.2 to 103.2%. The application of flow injection analysis (FIA) to automated dissolution studies of sustained-release formulations is described. The long-term stability of the dissolution-FIA analyzer. was checked during unattended operation for 42 h. The construction of multiple calibration curves with the so-called electronic dilution FIA procedure was used to extend the linear range of the determination. The computer-controlled FIA system and the principles of associated software are described and applied to dissolution studies of sustained-release formulations of iron(II) using its sensitive reaction with the color reagent, ferrozine. The extended linear range of the determination is 1-130 ppm iron(II) and the precision (RSD) better than 3% (n = 3).
Iron(2+) Pharmaceutical Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Adrenaline And Dopamine With Sodium-hydroxide"
J. Pharm. Biomed. Anal. 1996 Volume 14, Issue 5 Pages 571-577
J. J. Berzas Nevado*, J. M. Lemus Gallego and P. Buitrago Laguna

Abstract: A new, rapid and economical flow injection method for determining adrenaline and dopamine is proposed on the basis of the hydrolysis of these compounds in alkaline medium. The method was optimized by using a spectrophotometer operating at lambda = 390 nm as detector. Calibration graphs were linear up to 2 x 10^-4 M with quantification limits of 2.5 x 10^-6 M and 3.3 x 10^-6 M for dopamine and adrenaline respectively. Flow injection allows the measurement of 130 samples per hour. The method was successfully applied for the determination of catecholamines in pharmaceuticals. A flow injection spectrophotometric method for the determination of adrenaline (I) and dopamine (II) in pharmaceuticals, based on their hydrolysis to colored aminochrome derivatives in alkaline medium, is presented. Pharmaceutical formulations were diluted appropriately with 50 mM acetate buffer of pH 4.8 and a 350 µL portion was injected into a stream of water carrier solution (2 ml/min) heated at 65°C in a flow injection manifold (schematic shown). The sample stream was merged with a reagent stream of 0.4 M NaOH flowing at the same rate and the mixture was pumped through a reactor (2.7 m x 0.5 mm i.d.) and the products were detected at 390 nm in a flow cell. Beer`s law was obeyed up to 200 µM-I and -II and the corresponding detection limits were 0.76 and 0.97 µM. The method was applied to the analysis of three pharmaceutical preparations (listed). Results were in good agreement with labelled values.
Catecholamines Adrenaline Dopamine Norepinephrine Epinephrine Pharmaceutical Spectrophotometry

"Fluorimetric Determination Of Chloroxine Using Manual And Flow Injection Methods"
J. Pharm. Biomed. Anal. 1996 Volume 14, Issue 11 Pages 1505-1511
Tom&aacute;s P&eacute;rez-Ruiz*, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s and Jos&eacute; Carpena

Abstract: Powdered tablets equivalent to 20 mg chloroxine (5,7-dichloroquinolin-8-ol; I) were shaken with 25 mL 4 M acetic acid, sonicated and diluted to 1 l with water. Topical preparations equivalent to 10 mg I were heated with 25 mL methanol/acetic acid (3:2) and diluted to 1 l with water. For FIA, sample (95 µL) was injected into a stream (1.2 ml/min) of 14 mM sodium lauryl sulfate which was merged with a stream of 0.2 M acetate buffer (0.4 ml/min) of pH 4.2 and then a stream (0.4 ml/min) of 2.5 mM AlCl3. After passing through a reactor coil (60 cm x 0.5 mm i.d.) the fluorescence was measured at 496 nm (excitation at 399 nm). A batch method was also carried out (details given) in which the calibration graph for I was linear for 20 nM- to 51 µM-I and the detection limit was 5 nM. For FIA, the calibration graph was linear for 0.56-56 µM-I, and the detection limit was 0.13 µM. RSD were 2.3% and 0.38% for the batch and FIA methods, respectively. Recoveries were 96-103%.
Chloroxine Pharmaceutical Pharmaceutical Fluorescence

"Amperometric Biosensing Of Copper(II) Ions With An Immobilized Apoenzyme Reactor"
Sens. Actuat. B 1990 Volume 1, Issue 1-6 Pages 499-503
Ikuo Satoh*, Teruo Kasahara and Naoto Goi

Abstract: An amperometric flow injection system, incorporating an immobilized-apoenzyme reactor for specific recognition of Cu, is presented (diagram given). Copper ions were selectively determined in the range 0.1 to 10 mM by activation of immobilized metal-free galactose oxidase (I). The I was immobilized on alkylamino controlled pore glass beads (120 to 200 mesh; pore diameter 51.5 nm) and the preparation was loaded into a plastic column which was mounted in a water-jacketed holder. A polarographic O electrode, or a cellulose-acetate-membrane covered Pt - Ag - AgCl electrode pair, housed in a plastic flow-through cell was connected to the outlet of the enzyme reactor to monitor the amount of O consumed, or H2O2 generated, by the activated enzyme. A constant voltage of -0.7 V vs. Ag - AgCl for O, or 0.7 V vs. Ag - AgCl for H2O2, was applied to the Pt electrode. The carrier solution (1 mL min-1) was 0.05 M phosphate buffer (pH 6) containing 0.1 M KCl. D-Galactose solution was added as substrate solution and 10 mM N,N-diethyldithiocarbamate solution (pH 8) was used to regenerate the reactor.
Copper(II) Amperometry Electrode Sensor

"Analytical Application Of Immobilized Acid Urease For Urea In Flow Streams"
Sens. Actuat. B 1991 Volume 5, Issue 1-4 Pages 241-243
Ikuo Satoh* and Masashi Akahane, Kunio Matsumoto

Abstract: A description is given of a system for the calorimetric flow injection determination of urea (I) which is based on acid urease immobilized on porous glass beads packed into a small polymer column. For determination of I, sample is introduced at 1 mL min-1 via a citrate buffer carrier stream (0.1M; pH 5) and the heat generated by the enzymatic hydrolysis of I is monitored through the enzyme thermistor system. The calibration graph was rectilinear from 0.05 to 2 mM I (1 mL samples). Analysis time was 6 min and the coefficient of variation for 1.0 mM I was 1%. The method may be applied to the determination of I in alcoholic beverages.
Urea Calorimetry Thermistor

"Calorimetric Flow Injection Determination Of Glutathione With Enzyme - Thermistor Detector"
Sens. Actuat. B 1991 Volume 5, Issue 1-4 Pages 245-247
Ikuo Satoh*, Shuji Arakawa and Akira Okamoto

Abstract: For the cited determination glutathione sulfhydryl oxidase and catalase were immobilized separately with bovine serum albumin on Eupergit-C (100 to 200 µm) and double layered into a small polymer column. Sample solution was introduced at 1 mL min-1 via McIlvain buffer (pH 5.0) and the heat generated was measured by the enzyme - thermistor device. The calibration graph was rectilinear from 0.5 to 10 mM glutathione. Analysis time was 6 min and the coefficient of variation for 5.0 mM glutathione was 1.2% (n = 5).
Glutathione Calorimetry Thermistor

"Combination Of An Amperometric Integrated Glucose Sensor With Flow Injection Analysis For Bioprocess Control"
Sens. Actuat. B 1991 Volume 4, Issue 3-4 Pages 309-313
P. Bataillard, S. Haemmerli, H. L&uuml;di and H. M. Widmer

Abstract: The sensor consisted of Pt working and counter electrodes and a Ag - AgCl reference electrode. A phosphate buffer solution (pH 6.0) containing 50 mg mL-1 glucose oxidase, 50 mg mL-1 bovine serum albumin and 0.5% glutardialdehyde was deposited on the electrodes. The sensor was used in a flow injection system for the detection of glucose. The enzyme reacted with the analyte to produce H2O2 which was oxidized at the working electrode set at +0.7 V vs. Ag - AgCl; the resulting current was measured amperometrically. A linear response was obtained for concentration. up to 2 mM glucose; the detection limit was 1 µM. Interferences due to oxidizable compounds (e.g., phenols) could be eliminated by immobilization of an electron mediator (e.g., ferrocene compounds) onto the electrodes. The method was successfully used for monitoring the progress of yeast fermentation in cultivation broth samples.
Glucose Amperometry Electrode Sensor

"Enzymic Flow Injection Analysis For Essential Fatty Acids"
Sens. Actuat. B 1994 Volume 19, Issue 1-3 Pages 607-609
M. Schoemaker and F. Spener

Abstract: Solution (10 mM) of linoleic (I) and α-linolenic (II) acids in Tween 20 were prepared as described by Axelrod et al. (Methods in Enzymology, 1981, 71, 441). Portions (20 µL) were injected into the FIA system and were carried in a stream (450 µL/min) of 0.2 M potassium borate buffer of pH 9 containing 0.02% Tween 20, to a column (5 cm x 3 mm i.d.) of lipoxygenase immobilized on CNBr-activated Sepharose 4B. The decrease in O2 concentration resulting from enzyme-catalyzed lipid peroxidation was measured using a Clark-type O2 electrode held at -600 mV vs. Ag/AgCl. The calibration graphs for I and II were linear from 0.1-1.2 mM. The RSD for determination of 1 mM I (n = 55) was 1.4%.
Linoleic acid α-Linolenic acid Organic compound Electrode Electrode

"Enhanced Luminescent Response Of A Fibre-optic Sensor For H2O2 By A High-salt-concentration Medium"
Sens. Actuat. B 1997 Volume 39, Issue 1-3 Pages 189-194
L. J. Bluma,* and A. B. Collaudina

Abstract: A H2O2 biosensor, based on the luminol-peroxidase system, exhibited an enhanced luminescent response in the presence of high concentrations of KCl or NaCl. The biosensor was fabricated by immobilizing horseradish peroxidase onto a polyamide membrane attached to an optical fiber. The biosensor was mounted in a black PVC detection cell (130 µL) and incorporated into a single channel FIA system. The FIA system was operated with a carrier stream (0.95 ml/min) of 0.1 M Tris-HCl buffer at pH 8.5 containing 55 µM-luminol and NaCl or KCl. The enhancement of the response was dependent on the H2O2 concentration and was 1-8 fold in the presence of 3 M KCl and 3-8 fold in the presence of 3 M NaCl for 6.25-25 nmol injected H2O2. The RSD (n = 40) for 250 pmol H2O2 were 3.2 or 2.7% in the presence of 3 M KCl or NaCl, respectively. The biosensor retained its full activity after 2 days of intensive use and 83% of its initial activity after 4 days of use. (21 References)
Hydrogen peroxide Sensor Chemiluminescence

"An Enzyme-modified Chemiluminescence Detector For Hydrogen Peroxide And Oxidase Substrates"
Sens. Actuat. B 1997 Volume 39, Issue 1-3 Pages 291-294
D. Janaseka,* and U. Spohna

Abstract: Enzyme-modified silica and graphite pastes were used to construct chemiluminescence detectors for hydrogen peroxide, glucose and L-lactate. The pastes for H2O2 detection were prepared by mixing a solution containing 1-5 mg fungal peroxidase in 2.9 mL 0.1 M Tris buffer with 100-300 µL 0.32% polyethyleneimine and 100 mg fumed silica, LiChrospher Si 100, Li-Chrospher NH2 100 or graphite powder. The mixtures were dried under vacuum and then dispersed in 2 µL octadecane/paraffin oil (9:1). The resulting paste was packed into a cavity (0.32 mm x 7 mm i.d.) in the flow-through detection cell (total volume 2.2 µL) in a FIA system. The stability of the graphite paste detector was improved by coating with electropolymerized o-phenylenediamine. The FIA system was equipped with a 30 µL injection loop and was operated with 0.5 mM luminol/0.2 M Na2CO3 at pH 9.2 as the reagent stream and 0.1 M potassium phosphate buffer at pH 7.4 as the carrier stream (both at 0.2 ml/min). H2O2 was injected into the buffer carrier stream which was then merged with the reagent stream. The chemiluminescence signal was detected with a photodiode. Bienzyme optrodes for the detection of glucose and L-lactate were prepared by immobilizing glucose oxidase and lactate oxidase, respectively, in a poly(carbamoylsulfonate) hydrogel adsorbed onto the graphite-paste H2O2 detector.
Glucose Hydrogen peroxide Lactate Chemiluminescence Optrode

"Catalytic Determination Of Nanogram Amounts Of Vanadium In Natural Water By Flow Injection Analysis"
Anal. Sci. 1989 Volume 5, Issue 1 Pages 69-72
S. NAKANO, M. TAGO and T. KAWASHIMA

Abstract: A 0.2 mL sample was injected into a carrier stream (0.8 mL min-1), which was then mixed with streams (0.8 mL min-1) of (i) 4 mM 4-aminoantipyrine, 30 mM NN-dimethylaniline and 0.1 M Tiron, (ii) 0.08 M BrO3-, and (iii) 0.15 M formate buffer in a coil (10 m x 0.5 mm) at 55°C. The absorbance was measured at 555 nm. The calibration graph was rectilinear for 0.05 to 2 ng mL-1 of VV; the detection limit was 20 pg mL-1. Coefficients of variation for 1 and 2 ng mL-1 were 0.8 and 0.5% (n = 10), respectively.
Vanadium(V) Environmental Spectrophotometry

"Glucose Sensor Carrying Monomolecular Layer Of Glucose Oxidase Covalently Bound To Tin(IV) Oxide Electrode"
Anal. Sci. 1989 Volume 5, Issue 5 Pages 507-512
Y. OKAWA, H. TSUZUKI, S. YOSHIDA and T. WATANABE

Abstract: The enzyme-immobilized SnO2 electrode (Watanabe et al., Chem. Lett., 1988, 1183) was immersed in 67 mM phosphate buffer (pH 6.4), to which a portion of glucose solution was added. The mixture was stirred for 10 s and the change in current was recorded; the steady-state current was taken as the output of the sensor, in which Ag - AgCl and Pt reference and counter-electrodes, respectively, were incorporated. The system was used in a flow injection analysis system; the detection limit was 10 µM. Calibration graphs were rectilinear up to 10 mM glucose. The flow injection system was applied for the determination of glucose in diluted serum; anion-exchange HPLC was used for preliminary removal of interfering matrix components.
Glucose Blood Serum Electrode Electrode Sensor

"Flow Injection Determination Of Acids And Bases In Non-aqueous Solvents"
Anal. Sci. 1989 Volume 5, Issue 6 Pages 777-779
T. IMATO, A. KATAKUCHI, T. HAMAZOE, J. YAGI, K. TAKAHARA and N. ISHIBASHI

Abstract: The sample solution is injected into a stream of propan-2-ol - toluene - water (159:40:1), which is subsequently merged with buffer solution containing an indicator in the same mixed solvent. The mixture then passes through a spectrophotometric detector in series with a flow-through glass pH electrode detector. With use of methyl red (20 µM) as indicator, the buffer is 5 mM butyric acid - 5 mM tetrabutylammonium butyrate containing 0.1 M LiCl (to stabilize the baseline potential of the pH detector) and the absorbance is measured at 520 nm; with use of bromophenol blue (5 µM), the buffer contains 5 mM chloroacetic acid, 5 mM tetrabutylammonium chloroacetate and 0.1 M LiCl and the absorbance is measured at 600 nm. The absorbance peak heights are rectilinearly related to peak height for, e.g., propylamine and chloroacetic acid.
Propylamine Chloroacetic acid Spectrophotometry Electrode

"Flow Injection Extraction-spectrophotometric Determination Of Copper With Dithiocarbamates"
Anal. Sci. 1990 Volume 6, Issue 3 Pages 415-420
J. SZPUNAR-LOBINSKA and M. TROJANOWICZ

Abstract: Several dithiocarbamates were investigated as reagents for the determination of Cu, and a flow injection method was developed. Sample solution (300 µL) in aqueous NH3 buffer (pH 8.5) as carrier solution was mixed with 0.05% Pb diethyldithiocarbamate in CHCl3, and passed through a coil (400 cm x 0.5 mm). The phases were separated in a membrane separator, and the absorbance of the organic phase was measured at 436 nm. The detection limit is 0.04 ppm of Cu, and the calibration graph is rectilinear up to 2 ppm. The method was applied to water and plants; results were precise and accurate.
Copper Vegetable Vegetable River Spectrophotometry Sample preparation

"Potentiometric Determination Of Reducing Sugars As Borate Complexes Using Hexacyanoferrate(III) - Hexacyanoferrate(II) Potential Buffer And Its Application To Liquid Chromatography"
Anal. Sci. 1990 Volume 6, Issue 5 Pages 777-779
H. OHURA, T. IMATO, S. YAMASAKI and N. ISHIBASHI

Abstract: A system of flow injection analysis with HPLC (diagram given) for the determination of mixed reducing sugars (mono- and di-saccharides) was described with use of a flow-through type oxidation-reduction potential electrode detector cell and a potentiometer. A potential buffer solution comprising 0.1 M [Fe(CN)6]3- - 0.1 M [Fe(CN)6]4- and containing 1 M NaOH was pumped at 0.45 mL min-1 and the 0.5 M borate reagent solution was pumped at 0.5 mL min-1. Sample solution (20 µL) was injected into the borate stream and carried through an anion-exchange column (15 cm x 4.6 mm) of TSK-Gel, Sugar AXI, TOSO for separation at 60°C. The column effluent was merged with the potential buffer solution and the composition change of the buffer caused by reduction of [Fe(CN)6]3- was measured. The calibration graph was almost rectilinear for 2.5 to 10 µM of the mixed saccharides. The coefficient of variation was 1.5% (n = 5) for a 10 µM mixture of cellobiose, maltose and lactose. Detection limits were 0.4 to 2 µM. Sensitivity was similar to or better than amperometric, fluorimetric and spectrophotometric detection methods.
Sugars, reducing Potentiometry HPLC Electrode Ion exchange

"Determination Of Seven Opioid Peptides In Rat Brain By High Performance Liquid Chromatography With Online Post-column Fluorescence Derivatization"
Anal. Sci. 1990 Volume 6, Issue 5 Pages 671-676
G.-Q. ZHANG, M. KAI and Y. OHKURA

Abstract: Sample solution (prep. described; 60 µL) was incubated with 10 µL of carboxypeptidase A or trypsin in 50 mM phosphate buffer (pH 7.8) and phosphate buffer (40 µL) for 30 min at 37°C. A 100 µL portion was analyzed by HPLC on a column (15 cm x 6 mm) of Asahipak ODP-50 (5 µm) with gradient elution (1 mL min-1) with acetonitrile - 50 mM sodium borate buffer (pH 10.0) - water (1:4:15 and 3:1:1). The column eluate was mixed with 0.3 M borate buffer (pH 8.5) and 8 mM hydroxylamine oxalate - 0.2 mM Co(II) acetate, the mixture was passed through a reaction coil (10 m x 0.5 mm) heated to 100°C, and the fluorescence was monitored at 430 nm (excitation at 330 nm). The method was used for the simultaneous determination of seven endogenous opioid peptides at the pmol level in brain tissue. Detection limits were 0.5 to 1.5 pmol injected.
Peptides Brain HPLC Fluorescence

"Flow Injection Determination Of Trace Amounts Of Hydrogen Peroxide With Thio-Michler's Ketone"
Anal. Sci. 1990 Volume 6, Issue 7 Pages 149-150
K. TOEI, T. TAMARU and M. ZENKI

Abstract: Samples (0.13 ml), containing 0.02 to 1 ppm of H2O2, are injected into a carrier stream comprising 25 mM NaI - 0.5 mM ammonium molybdate - 0.2% of Na polystyrene sulfate. This is mixed with a reagent solution comprising 45 µM-4,4'-bis(dimethylamino)thiobenzophenone (I) - 1.3% of Triton X-100 - 13% of methoxyethanol - 0.05 M formate buffer (pH 3.5) in a reaction coil maintained at 30°C. The color change of I (thio-Michler ketone) is measured at 660 nm. Samples could be analyzed at a rate of 42 h-1. The calibration graph was rectilinear over the cited range. The system could be used to determine glucose indirectly, by incorporation of glucose oxidase. The calibration graph was rectilinear for 80 mg l-1. The method was used to determine glucose in urine. Samples (0.13 ml), containing 0.02 to 1 ppm of H2O2, are injected into a carrier stream comprising 25 mM NaI - 0.5 mM ammonium molybdate - 0.2% of Na polystyrene sulfate. This is mixed with a reagent solution comprising 45 µM 4,4'-bis(dimethylamino)thiobenzophenone (I) - 1.3% of Triton X-100 - 13% of methoxyethanol - 0.05 M formate buffer (pH 3.5) in a reaction coil maintained at 30°C. The color change of I (thio-Michler ketone) is measured at 660 nm. Samples could be analyzed at a rate of 42 h-1. The calibration graph was rectilinear over the cited range. The system could be used to determine glucose indirectly, by incorporation of glucose oxidase. The calibration graph was rectilinear for 80 mg l-1. The method was used to determine glucose in urine.
Hydrogen peroxide Glucose Urine Spectrophotometry

"Rapid Microdetermination Of Hydroxyproline In Biomedical Samples By Flow Injection Analysis Using Cysteine As An Antioxidant"
Anal. Sci. 1990 Volume 6, Issue 1 Pages 39-44
K. UCHIDA, M. TOMODA, T. SHIBATA, S. IKEUCHI, T. HASEBE, T. MIWA, T. NOMOTO, K. FUKUSHIMA, S. SAITO and S. INAYAMA

Abstract: Tissue samples are hydrolyzed with 6 M HCl, the mixtures are freeze-dried, and the residues are dissolved in 0.01 M cysteine. Portions are injected into a stream of chloramine T solution (0.7 g L-1 in borate buffer of pH 8.7). Passage through a heating coil at 100°C causes hydroxyproline (I) to be oxidized and decarboxylated to pyrrole. Treatment with a solution of Ehrlich reagent (4-dimethylaminobenzaldehyde) in 10% H2SO4 and 10% Triton X-100 gives a colored product, which is detected at 560 nm. The calibration graph is rectilinear in the range 1 to 80 µg mL-1 of I. Optimization experiments are described especially for concentration. of chloramine T (oxidant) and cysteine (color stabilizer). The method, which avoids use of organic solvents, allows 100 samples to be analyzed in ~5 h. Recoveries of I are 94.8 to 103.7%. Results agreed well with those from a batch method.
Hydroxyproline Skin Spectrophotometry

"Determination Of Manganese By Flow Injection Analysis Based On Its Catalytic Effect On The Oxidative Coupling Reaction Of 3-methyl-2-benzothiazolinone Hydrazone With NN-dimethylaniline"
Anal. Sci. 1991 Volume 7, Issue 1 Pages 97-101
Y. MIYATA, T. HIRANO, S. NAKANO and T. KAWASHIMA

Abstract: Sample solution was injected into a carrier stream of aqueous 1.2% H2O2 and reacted at 50°C in a reaction coil (3 m) with 0.1 M citrate - 0.2 M Tris buffer solution (pH 11), 30 mM NN-dimethylaniline - 3 mM 3-methyl-2-benzothiazolinone hydrazone - 3 mM 1,10-phenanthroline. The mixture was cooled to 25°C in a 1-m reaction coil and the absorbance was measured at 590 nm. The calibration graph was rectilinear for 4 to 30 ng mL-1 of Mn and the coefficient of variation were 1.9 to 4.2%. The method was applied in the analysis of standard reference materials, the results obtained compared well with certified values.
Manganese NIES 1 NIES 3 NIES 7 Spectrophotometry

"Flow Injection Indirect Spectrophotometric Determination Of Iron(II) Based On Redox Reaction With Copper(II) In The Presence Of Neocuproine"
Anal. Sci. 1991 Volume 7, Issue 1 Pages 163-164
H. ITABASHI, K. UMETSU, K. SATOH and T. KAWASHIMA

Abstract: Sample solution was injected into a carrier stream of water and reacted with a stream of 0.1 mM Cu(II) - 2 mM pyrophosphate - 0.5 mM neocuprone in 50 mM acetate buffer solution of pH 5.6 (both at 1.2 mL min-1) in a reaction coil (1 m x 0.5 mm). The absorbance of the solution was measured at 454 nm. The calibration graph was rectilinear for up to 80 µM-Fe (II) with a detection limit of 0.2 µM, and the coefficient of variation was 0.1 to 6.0%. Interference was present from V (IV).
Iron(2+) Spectrophotometry

"Determination Of Selenium By Flow-injection Analysis Based On The Selenium(IV)-catalyzed Reduction Of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium Bromide"
Anal. Sci. 1991 Volume 7, Issue 1 Pages 103-107
E. AOYAMA, N. KOBAYASHI, M. SHIBATA, T. NAKAGAWA and H. TANAKA

Abstract: Sample solution was mixed with NaOH (to pH 7) and 0.1 M phosphate buffer solution (pH 7) containing 12 mM bathocuproine disulfate and the mixture was injected into a carrier solution of 0.1 M phosphate buffer solution (0.2 mL min-1) and through a column (5 cm x 4.6 mm) of Chemcasorb 3-ODS-H operated at 40°C. The eluate was mixed with 7.3 mM dithiothreitol and 3-[4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and the absorbance of the solution was measured at 565 nm. Analysis time was 8 min. The calibration graph was rectilinear for 1.3 pmol to 1.2 nmol Se (IV) and the coefficient of variation was 2.2%. The method was applied in the analysis of lobster refrence material, recovery was 103% for 5 µg mL-1 of Se and no interference was present.
Selenium NRCC TORT-1 Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Trace Amounts Of Iodide By Its Catalytic Effect On The 4,4'-bis(dimethylamino)diphenylmethane [4,4'-methylenebis-(NN-dimethylaniline)] - Chloramine T Reaction"
Anal. Sci. 1991 Volume 7, Issue 2 Pages 229-234
N. YONEHARA, S. KOZONO and H. SAKAMOTO

Abstract: Sample solution (300 µL) was injected into a water carrier stream (3 mL min-1) and this was mixed successively with acetate buffer solution (pH 4.5), 1.2 mM 4,4'-methylenebis-(NN-dimethylaniline) in aqueous 0.23% acetic acid, and 0.75 mM chloramine T (all 0.5 mL min-1). The reaction mixture was passed through a 4-m reaction coil at 30°C and then through a flow cell in which the absorbance was monitored at 600 nm. Calibration graphs were rectilinear for up to 2 µg L-1 of I-; the coefficient of variation at 0.4 and 4 µg L-1 were 2.8 and 0.8%, respectively (n = 10). The sampling rate was 85 h-1. Free iodine exhibits a lower catalytic effect, and IO3- has no effect at concentration. 50 µg L-1 (as iodine), but both species can be determined after reduction to I- by treatment with thioacetamide in acid solution The effects of >30 foreign ions are reported. Only ions that participate in redox processes or combine with I- interfere significantly. The method has been applied to various natural waters.
Iodide Environmental Spectrophotometry

"Simultaneous Determination Of Catecholamine-related Compounds By High Performance Liquid Chromatography With Post-column Chemical Oxidation Followed By A Fluorescence Reaction"
Anal. Sci. 1991 Volume 7, Issue 2 Pages 257-262
H. -K. JEON, H. NOHTA, H. NAGAOKA and Y. OHKURA

Abstract: Thirteen such compounds (three catecholamines, one precursor and nine metabolites), together with isoprenaline and 3-(3,4-dihydroxyphenyl)propionic acid, were separated on a TSK-gel ODS-80TM column (25 cm x 4.6 mm) with methanol - 0.4 mM Na octane-1-sulfonate in 30 mM citrate buffer (7:93) as mobile phase (0.8 mL min-1). The separated components were oxidized to the corresponding o-quinones by treatment with 10 mM NaIO4 - 3 mM K3Fe(CN)6, and these were converted into fluroescent derivatives by reaction with 30 mM meso-1,2-diphenylethylenediamine in aqueous 70% ethanol solution containing 0.13 M Na methoxide. The fluorescence intensity was monitored continuously at 480 nm (excitation at 350 nm). Detection limits ranged from 14 fmol for adrenaline to 570 fmol for (4-hydroxy-3-methoxyphenyl)ethanediol, and coefficient of variation were ~3.1% (n = 10).
Catecholamine, derivatives HPLC Fluorescence

"Chemiluminescence Determination Of Titanium(IV) By Flow Injection Analysis Using A Jones Reductor Column Online"
Anal. Sci. 1991 Volume 7, Issue 4 Pages 623-625
A. A. ALWARTHAN, A. ALMUAIBED and A. TOWNSHEND

Abstract: The cited determination involves the reaction of Ti(III) with a carbonate buffer after passing the Ti(IV) samples through a Jones reductor mini-column using 0.01 M HCl as a carrier stream. The detection limit was 1 µM. The coefficient of variation of 40 mM Ti was 4.4%. The Ti signal was affected by Ni(II), Co(II), Cd(II), Ce(IV) and Mo(VI).
Titanium(IV) Chemiluminescence

"Flow Injection Determination Of The Total Water Hardness By Using A Copper(II)-ion-selective Electrode And A Copper(II) Ion Buffer"
Anal. Sci. 1992 Volume 8, Issue 5 Pages 631-635
T. IMATO, K. ISHII and N. ISHIBASHI

Abstract: The flow injection system comprised two double-plunger pumps, a sample injector and a flow-through-type Cu2+-selective electrode detector (FLC 12, Denki KK). The output signals from a potentiometer were recorded. Sample solution (200 µL) containing Ca2+ and/or Mg2+ was injected into a stream of water that then merged with a stream of 0.5 M NaNO3. This mixed stream then mixed with the Cu2+ buffer [2.5 mM Cu(NO3) - 5 mM EDTA - 0.1 mM triethylenetetramine (I) - 0.5 M KNO3, adjusted to pH 9.4 with aqueous 0.1 M NH3 and 0.1 M NH4NO3] and passed to the flow-through electrode detector. Chloride interference was eliminated by the addition of I. The total hardness of seawater samples was determined at a rate of 30 h-1 with a coefficient of variation of 0.7%. A potentiometric determination of the total water hardness by flow -injection anal. is proposed, which uses both a Cu2+-selective electrode and a Cu2+ buffer stream comprising a Cu-EDTA complex and free EDTA. This method is based on the potentiometric change in the free Cu2+ concentration. in the buffer with a Cu2+-selective electrode, caused by the reaction of Ca2+ and Mg2+ with free EDTA in the buffer. Cl- interference was eliminated by adding triethylenetetramine to the Cu2+ buffer. The total hardness of seawater could be determined at a sampling rate of 30 h-1 and relative standard deviation 0.7%. The results were in good agreement with those obtained by conventional chelatometric titration.
Hardness Sea Electrode Potentiometry

"Selective Biosensing Of L-lysine By A Low-temperature Flow Injection Technique Using An Immobilized Lysine Oxidase Reactor"
Anal. Sci. 1996 Volume 12, Issue 1 Pages 87-90
R. L. C. CHEN, M.-H. LEE and K. MATSUMOTO

Abstract: A method for the determination of L-lysine (lysine; I) using a H2O2 electrode as a biosensor device in an enzymatic FIA system is presented and used to analyze the concentration of I in fish feed. Squid or white-fish meal (10 g) was suspended in 100 mL 0.1 M phosphate buffer of pH 7.3 (buffer A) and the suspension was incubated with protease (10 000 U Denazyme AP) for a definite time. The reaction mixtures were incubated at 90°C for 10 min and centrifuged at 11 000 g for 1 h. The supernatants were filtered (0.45 µm) and a 20 µL portion of the filtrate was injected into a carrier stream of buffer A (3 ml/min) of an automated flow injection system (schematic shown). A computer-controlled switching valve downstream allowed the carrier to pass alternately through a lysine oxidase (LO)-immobilized aminopropyl-glass (APG, pore size 70 nm, 80-120 mesh) enzyme reactor and aa identical reactor containing APG only. The H2O2 (I) produced by the enzyme reactor was detected electrochemically at 10°C. The calibration graph was linear up to the mM range of I and the detection limit was of the order of tens of µM. The RSD (n = 8) was 1.45% for 0.5 mM I. Results agreed well with those obtained by HPLC.
l-Lysine Feed Squid Meal Whitefish Meal Amperometry Electrochemical analysis Sensor

"Simultaneous Flow Injection Determination Of Acetylcholine And Choline Based On Luminol Chemiluminescence In A Micellar System With Online Dialysis"
Anal. Sci. 1997 Volume 13, Issue 1 Pages 93-98
T. HASEBE, J. NAGAO and T. KAWASHIMA

Abstract: The method was based on the determination of H2O2 produced from acetylcholine (I) and choline (II) by enzyme reactions. A flow diagram is given of the FIA system. A water carrier, a 0.02 M disodium hydrogen phosphate/NaOH buffer of pH 11, a 0.02 M phosphate buffer of pH 7, a 1 µM-Co(II) solution in 0.01 M HCl as a catalyst for the chemiluminescence reaction and a mixed solution of 0.5 µM-luminol, 0.1 M sodium hydrogen carbonate and 0.18% SDS in borate buffer solution of pH 11 were pumped by three double-plunger pumps. An 800 µL sample was injected into the carrier, dialysed to remove protein and passed through an anion-exchange column to remove other interferents such as ascorbic acid, uric acid, histidine and tryptophan. II was converted to H2O2 via choline at another immobilized enzyme column. H2O2 produced from II was passed through a delay coil before the chemiluminescence of I and II were measured from 350-650 nm. The reactions were performed at 37°C. The method could determine down to 1 µM at a sampling rate of 6 samples/h.
Acetylcholine Choline Chemiluminescence

"A Semi-continuous Flow Method For The Trace Analysis Of Dissolved Inorganic Antimony"
Anal. Proc. 1989 Volume 26, Issue 1 Pages 32-34
A. T. Campbell and A. G. Howard

Abstract: A 5 mL sample is mixed with 0.5 mL of 1 M KI pre-reductant, and masking agents (if required), and placed in the continuous-flow system (details and diagram given). The solution is acidifed with HCl for determination of total Sb, or mixed with acetate buffer of pH 5.0 for determination of Sb(III), segmented with air, and treated with aqueous 2% NaBH4; the products are swept through a delay coil and stripped from solution in a gas - liquid separator. Stibine is condensed in a cryogenic trap at -196°C, liquid N is then removed and the trap is warmed to room temp., before atomization of stibine and AAS detection at 217.6 nm. Calibration graphs are rectilinear for up to 3 ng of Sb(III) or total Sb, with a detection limit of 24 ng L-1 of total Sb (for a 5 mL sample). Interfering ions are tabulated. The method is applied in determination of total Sb in natural water.
Antimony(3+) Antimony, total Environmental Spectrophotometry

"Flow Injection Determination Of Organosulfur Compounds With Chemiluminescence Detection"
Anal. Proc. 1989 Volume 26, Issue 1 Pages 19-20
J. Steven Lancaster, Paul J. Worsfold

Abstract: A flow injection system is described and illustrated, for determination of 2-(ethylthio)phenol (I) in a carrier stream of acetone, with an oxidant stream of 1 M NaOCl in 0.1 M HCO3- buffer of pH 11.0 (both 1.0 mL min-1); chemiluminescent detection was used. The calibration graph (log. - log.) of concentration. vs. emission intensity was rectilinear from 1 to 50 mM I, and the detection limit was 0.4 mM. The coefficient of variation (n = 10) ranged from 1.6 to 22.8%.
2-Ethylthiophenol Chemiluminescence

"Flow Injection Analysis Of Phospholipids"
Anal. Proc. 1989 Volume 26, Issue 2 Pages 64-65
F. F. Barretto, J. M. Slater

Abstract: The flow injection system was based on a Stelte micro-cell detector, modified by machining a wall-jet electrode chamber for the working electrode, viz, a Pt electrode covered with nylon mesh on which were immobilized phospholipase D and choline oxidase (1:1). Optimum flow rate was 2.33 mL min-1, and the H202 produced was detected at +650 mV vs. Ag - AgCl. The carrier solution was 0.2 M glycine buffer of pH 10. The calibration graph was rectilinear from 0.2 to 0.6 g L-1 of phospholipids in serum, and the detection limit was 0.01 g L-1 of phosphatidylcholine. The enzyme electrode can be used for >8 weeks.
Phospholipids Palmitoyloleoylphosphatidylcholine Blood Serum Electrode Electrode Electrode