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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Detection limit

Classification: Detection limit -> Detection limit

Citations 296

"4-Hydroxynaphthyl-1-phosphate As A Substrate For Alkaline Phosphatase And Its Use In Sandwich Immunoassay"
Anal. Chim. Acta 1999 Volume 402, Issue 1-2 Pages 29-35
Már Másson, Tetsuya Haruyama, Eiry Kobatake and Masuo Aizawa

Abstract: The synthesis and the use of a new substrate, 4-hydroxy-naphthyl-1-phosphate (HNP), for the amperometric detection of alkaline phosphatase activity is described. The product of the enzymatic hydrolysis of HNP was dihydroxy naphthalene (DHN). DHN was rapidly oxidized in air to give naphthoquinone (NQ), which was measured in amperometric flow injection analysis (AFIA) at 300 mV versus Ag/AgCl. DHN standards could be measured at a 60 nM detection limit. There was a linear response to the enzyme with a 300 fM detection limit, which was equivalent to 6 attomole for each injection. The measurement range for human IgG, in an alkaline phosphatase amplified sandwich immunoassay with amperometric, was 1-1000 ng/ml.

"Selective Determination Of TNT In Soil Extracts By Sequential Injection Spectrophotometry"
Anal. Chem. 1999 Volume 71, Issue 14 Pages 2739-2744
Roger T. Echols, Marcy M. Christensen, Ryan M. Krisko, and Joseph H. Aldstadt, III

Abstract: A rapid sequential injection spectrophotometric method for the selective determination of 2,4,6-trinitrotoluene (TNT) in soil samples is presented. The method is based on a derivatization reaction of TNT with sodium sulfite in a basic acetone medium. The reaction conditions, namely the percentage of acetone used in the reaction, the sample and reagent volumes, the mixing coil volume, and the reaction time, were optimized. The reaction was found to be particularly sensitive to the concentration of acetone; an acetone/water medium of 88% (v/v) acetone was found to be optimal. A study of the response of the method to other explosives demonstrated that the method is selective for TNT, In particular, it was shown that the method had little (<2%) or no response to other secondary explosives such as 2,4-or 2,6-dinitrotoluene (DNT). An average precision of 6.1% RSD was established for five soil samples (n = 4). The limit of detection was 0.5 µg mL-1 for aqueous standards and 80 µg g-1 for similar to 300 mg soil samples. analysis time was approximately three minutes per sample. Quantitative results from the determination of TNT in authentic contaminated soil samples compared favorably to those obtained using a standard method. The extension of the method to water samples and the means by which samples can be pre-concentrated online using solid-phase extraction (SPE) techniques are discussed.

"Improved Integrated Waveguide Absorbance Optodes For Ion-selective Sensing"
Anal. Chem. 2002 Volume 74, Issue 14 Pages 3354-3361
Mar Puyol, &Iacute;&ntilde;igo Salinas, Ignacio Garc&eacute;s, Francisco Villuendas, Andreu Llobera, Carlos Dom&iacute;nguez, and Juli&aacute;n Alonso

Abstract: The first prototype of a technologically improved integrated waveguide absorbance optode (IWAO) was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a cadmium ionophore. It was designed with curved instead of rectilinear planar waveguides. Results demonstrated the suitability of the new IWAOs to be employed as sensing platforms, which confer versatility, robustness, and mass production capabilities besides high sensitivity on conventional bulk optodes, as well as the usefulness of such dyes in developing ion-selective membranes in combination with a selective ionophore. The sensor integration as a detector in a flow injection system (FIA) was proposed to obtain an automated, simple, and sufficiently reproducible (RSD < 5%) analytical methodology with a sample throughput of 55 h-1. Very sensitive optodes were obtained, and detection limits on the order of 20 ppb were achieved. Because of the ionophore employed, the optode system showed excellent selectivity over alkali and alkaline-earth metals,with the exception of samples containing lead and cadmium ions, where the membrane responded to both analytes. The proposed procedure combines an the advantages of the FIA systems, the simplicity of optical detection, ion recognition selectivity, and sensitivity of ketocyanine dyes, and the features achieved using the integrated device, which comprise an improved sensitivity and short response times as well as robustness, easy handling, and mass production.

"Detection Limits In Classical Multivariate Calibration Models"
Anal. Chim. Acta 2000 Volume 423, Issue 1 Pages 41-49
Ricard Boqu&eacute;, Nicolaas (Klaas) M. Faber and F. Xavier Rius

Abstract: This work presents a new approach for calculating multivariate detection limits for the commonly used classical or direct calibration models. The derived estimator, which is in accordance with latest IUPAC recommendations, accounts for the different sources of error related to the calibration and prediction steps. Since the multivariate detection limit for a given analyte is influenced by the presence of other components in the sample, a different detection limit is calculated for each analyte and analyzed sample, at the chosen significance levels α and beta. The proposed methodology has been experimentally validated by determining four pesticides in water using a FIA method with diode-array detection. The results compare favourably with the ones obtained using previously proposed estimators.
Pesticides Environmental Spectrophotometry

"Feasibility Studies Of Simultaneous Multianalyte Amperometric Immunoassay Based On Spatial Resolution"
J. Pharm. Biomed. Anal. 1999 Volume 19, Issue 1-2 Pages 153-161
Ying Ding, Liping Zhou, H. Brian Halsall and William R. Heineman

Abstract: A multianalyte immunoassay concept based on the geometric separation of different analyte-specific antibodies has been demonstrated. The assay and amperometric detection are done in a cell with two working electrodes controlled at the same potential, and the amperometric signal at each electrode is monitored. The distance between any two adjacent electrodes in this prototype is 2.5 mm, and during the course of amperometric measurement, the product formed at one electrode does not reach the other working electrode within 20 min after the addition of enzyme substrate, Thus, the method relies on the spatial resolution between the different antibodies being such that measurements are taken before cross-interference due to diffusion can occur. Identical enzyme labels (alkaline phosphatase, ALP) and substrates (p-aminophenyl phosphate, PAPP) are used for all analytes. Alkaline phosphatase-conjugated rat anti-mouse IgG was immobilized by passive adsorption. Our studies showed that this concept is feasible and can be applied to the simultaneous measurement of multiple analytes.

"Rotating Disk Electrode Amperometric Detection For A Bead-based Immunoassay"
J. Electroanal. Chem. 1999 Volume 468, Issue 1 Pages 2-8
C. Ajith Wijayawardhana, S. Purushothama, M. A. Cousino, H. Brian Halsall and William R. Heineman

Abstract: Amperometric detection with a rotating disk electrode (RDE) for a bead based enzyme immunoassay for the model antigen mouse IgG has been developed. Alkaline phosphatase was used as the enzyme label for the conversion of the substrate 4-aminophenyl phosphate to the electroactive 4-aminophenol (PAP). The detection scheme allows enzyme turnover to be monitored continuously and thus reduces errors associated with obtaining data at fixed times as in flow injection analysis The determination of PAP by the RDE has a linear range from 5 x 10^-9 to 5 x 10^-5 M. An 800 µL electrochemical cell was used to minimize enzyme product dilution. A linear response for mouse IgG was obtained in this non-optimized system over the concentration range of 50-5000 ng mL-1.

"Capillary Electrochemical Enzyme Immunoassay (CEEI) For Phenobarbital In Serum"
J. Pharm. Biomed. Anal. 1999 Volume 19, Issue 1-2 Pages 145-152
Jin Zhang, William R. Heineman and H. Brian Halsall

Abstract: A competitive heterogeneous capillary enzyme immunoassay with electrochemical detection has been developed for phenobarbital in serum. The oxidized primary antibody was attached covalently to the modified interior surface of a microcapillary (22 µl). The competition between analyte phenobarbital and alkaline phosphatase labeled phenobarbital for a limited number of antibody binding sites was complete in 1.5 h. The enzymatic product (p-aminophenol) from the catalytic conversion of the substrate (p-aminophenyl phosphate) was detected by amperometric flow injection analysis. The calibration curve for phenobarbital had a detection limit of 30 µg L-1 (2.8 pmoles or 0.65 ng) and a range of 30-3000 µg L-1. The assay could be used to determine the phenobarbital serum concentration in a 4 µl clinical serum sample without pretreatment.

"Sorbent Extraction In Flow Injection Analysis And Its Application To Enhancement Of Atomic Spectrometry"
Anal. Chim. Acta 1989 Volume 216, Issue 1-2 Pages 243-255
J. Ruzicka and A. Arndal

Abstract: Standard Cu(II) and Pb(II) solution were prepared from the respective nitrates in 0.1 M HNO3. A time-based injection and a fixed-volume system are described and illustrated. The sample was mixed with a 0.05% solution of Na diethyldithiocarbamate (I) in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) containing 0.1% of Na2S2O4, and the solution was passed through a column (6.5 mm x 5 mm) containing 100 mg of Bond-Elut C18, with methanol as eluent. Lead and Cu were determined by AAS at 283.3 and 324.8 nm, respectively. Alternatively, saturated quinolin-8-ol (II) solution in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) was used as reagent solution and the eluent was ethanol. Complexation with 1-(2-pyridylazo)-2-naphthol and 4-(2-pyridylazo)resorcinol was also possible. Detection limits were 0.01 mg L-1 for Pb and 4 µg L-1 for Cu by using I and II, respectively. Standard Cu(II) and Pb(II) solution were prepared from the respective nitrates in 0.1 M HNO3. A time-based injection and a fixed-volume system are described and illustrated. The sample was mixed with a 0.05% solution of Na diethyldithiocarbamate (I) in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) containing 0.1% of Na2S2O4, and the solution was passed through a column (6.5 mm x 5 mm) containing 100 mg of Bond-Elut C18, with methanol as eluent. Lead and Cu were determined by AAS at 283.3 and 324.8 nm, respectively. Alternatively, saturated quinolin-8-ol (II) solution in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) was used as reagent solution and the eluent was ethanol. Complexation with 1-(2-pyridylazo)-2-naphthol and 4-(2-pyridylazo)resorcinol was also possible. Detection limits were 0.01 mg L-1 for Pb and 4 µg L-1 for Cu by using I and II, respectively.
Copper Lead Spectrophotometry Sample preparation

"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

"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

"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

"Flow Injection Method For Antimony(III) Based On Its Enhancement Of The Molybdenum Blue Reaction"
Anal. Chim. Acta 1989 Volume 224, Issue 2 Pages 373-381
Nathan Lacy, Gary D. Christian and Jaromir Ruzicka

Abstract: Flow injection analysis was performed at 20°C in a system in which the sample was injected into the carrier stream, the resulting solution was mixed with 2.5 M (NH4)6Mo7O24 in 0.2 M HNO3 containing 10 mg L-1 of phosphate-P in a 10-cm coil, and this solution was subsequently mixed with 5% L-ascorbic acid in aqueous 10% glycerol in a 200-cm coil before absorbance measurement at 600 nm. All reaction parameters were kept constant apart from the Sb concentration. to evaluate the enhancing effect of Sb(III) and thence its concentration. Continuous-flow analysis, with measurement 10 s after introduction of the ascorbic acid, gave reproducible calibration up to 100 mg L-1 of Sb, and the detection limit was 0.5 mg l-1. For 5 mg L-1 of Sb, the coefficient of variation was 2.1% (n = 10). Slight positive and negative interference was caused by SiO2 and As, respectively. Up to 120 samples could be processed in 1 h.
Antimony(3+) Spectrophotometry

"Steady-state And Flow Injection Response Of A Metallic Silver Electrode For Potentiometric Detection Of Metal Cyanide Complex Formation"
Anal. Chim. Acta 1989 Volume 225, Issue 1 Pages 105-113
Douglas P. Root, Daya Wijesuriya and Peter W. Alexander

Abstract: A 10 µL portion of a solution of Ag, Hg(II), Fe(III), Cu(II), Zn, Co(II) or Ni(II) was injected into a stream (0.8 mL min-1) of 0.29 mM CN-, and the change in potential was measured with use of a Ag metal electrode and Ag - AgCl reference. Response was rapid; the detection limit of Cu was 0.5 nmol per injection with a max. peak height of ~20 mV.
Copper Iron Zinc Nickel Cobalt Silver Potentiometry Electrode

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

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

"Determination Of Low Concentrations Of Chlorite And Chlorate Ions By Using A Flow Injection System"
Anal. Chim. Acta 1989 Volume 225, Issue 2 Pages 437-441
Demetrius G. Themelis, Delmer W. Wood and Gilbert Gordon

Abstract: Determination of ClO2- alone and in mixtures with ClO3- was achieved by reaction with I- at pH 2 to liberate I, which was measured spectrophotometrically at 370 nm. Both ClO2- and ClO3- react with I- in 6 M HCl, and the individual species were determined by multiple regression. The calibration graph was rectilinear from 2 to 150 µM-ClO2- and from 2 to 100 µM-ClO3-, with coefficient of variation of 0.4 and 1.2%, respectively. Detection limits were 0.04 mg L-1 for ClO2- and 0.03 mg L-1 for ClO3-. The method was fast and simple and suitable for sub mg L-1 levels in drinking water. Determination of ClO2- alone and in mixtures with ClO3- was achieved by reaction with I- at pH 2 to liberate I, which was measured spectrophotometrically at 370 nm. Both ClO2- and ClO3- react with I- in 6 M HCl, and the individual species were determined by multiple regression. The calibration graph was rectilinear from 2 to 150 µM-ClO2- and from 2 to 100 µM-ClO3-, with coefficient of variation of 0.4 and 1.2%, respectively. Detection limits were 0.04 mg L-1 for ClO2- and 0.03 mg L-1 for ClO3-. The method was fast and simple and suitable for sub mg L-1 levels in drinking water.
Chlorite Chlorate ion Water Spectrophotometry

"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

"Flow Injection Ultraviolet Spectrophotometric Determination Of Sulfate In Natural Waters"
Anal. Chim. Acta 1990 Volume 228, Issue 1 Pages 287-292
Anatol Kojo and Jacek Michaowski, Marek Trojanowicz

Abstract: Sample-injection and reagent-injection manifolds are presented for the formation of FeSO4+ in a stream of dilute HClO4 in the presence of Al(III) and Hg(II) to mask F- and Cl-, respectively. The absorbance is measured at 355 nm; the response is rectilinear for 25 to 600 and 10 to 150 mg L-1 of SO42-, respectively, and the detection limit of the former method is 19 mg l-1. Results agreed well with those obtained gravimetrically. Organic compounds that interfere by UV absorbance can sometimes be removed on a charcoal column, but the possibility exists of loss of SO42-; a subtractive procedure with sample injections in the presence and absence of Fe(III) can alternatively be used. The sampling rate is 10 to 30 h-1.
Sulfate Environmental Spectrophotometry

"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

"Determination Of Uranium Using A Flow System With Reagent Injection. Application To The Determination Of Uranium In Ore Leachates"
Anal. Chim. Acta 1990 Volume 230, Issue 1 Pages 217-220
J. L. Perez Pavon, B. Moreno Cordero, E. Rodriguez Garcia and Hernandez Mendez

Abstract: A flow injection spectrophotometric system is described in which UO22+ in the sample stream is reduced by passage through a glass column (5 cm x 2 mm) packed with Pb powder (0.1 to 0.3 mm) to U(IV), which then reacts with an injection of 0.2 mM arsenazo III in 3.6 M HCl containing 1% of Triton X-100 to form a complex for absorbance measurement at 665 nm. The detection limit is 26 nM-U, and the coefficient of variation (n = 10) at 6 µM was 0.62%. Zirconium can be masked with oxalic acid, and of 19 other species tested only Th interferes; this interference can be overcome by incorporating a valve to by-pass the reducing column and measuring the difference in peak heights with and without reduction.
Uranium Leachate

"Flow Injection Extraction-spectrophotometric Method For The Determination Of Lead And Its Combination With Minicolumn Preconcentration"
Anal. Chim. Acta 1990 Volume 230, Issue 1 Pages 157-162
E. A. Novikov, L. K. Shpigun and Yu. A. Zolotov

Abstract: Two flow injection systems were devised, one without and one with ion-exchange pre-concentration. [2-mm-i.d. glass column of Chelex-100 resin (NH4+ form; 50 to 100 mesh)]. The Pb(II) was extracted from an aqueous HNO3 carrier stream into dicyclohexano-18-crown-6 solution in CHCl3 in a PTFE coil (2 m x 0.5 mm), and after phase separation in a membrane separator the CHCl3 layer was treated with 0.002% dithizone - 0.4% triethanolamine solution in CHCl3 (mixing ratio 3:2) in a 30-cm PTFE reaction coil for absorbance measurement at 512 nm. With ion-exchange pre-concentration. for 79 s, the calibration graph was rectilinear in the range 10 to 200 µg l-1, the detection limit was 5 µg L-1 and the coefficient of variation at 100 µg L-1 was 9% (n = 4). Test applications to analyzes of alloys, soil extracts and seawater are described briefly.
Lead Sea Environmental Alloy Ion exchange Spectrophotometry Sample preparation

"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 For Continuous Sample Introduction In Solid-substrate Room Temperature Phosphorescence"
Anal. Chim. Acta 1990 Volume 231, Issue 2 Pages 289-293
A. D. Campiglia, A. Berthod and J. D. Winefordner

Abstract: A flow injection system is described and illustrated for continuous sample introduction in two-nebulizer phosphorescence analysis. Thallium acetate (0.1M) in aqueous 50% ethanol was used as heavy-atom enhancer, and sprayed continuously on to the moving filter paper at a flow rate adjusted to deliver ~10 µL cm-2 of substrate. The method was tested with use of phenanthrene (I), pyrene and 4-aminobenzoic acid (II) as model analytes. Detection limits were in the ng range and, for I and II, calibration graphs were rectilinear over 2 orders of magnitude. Precision was 10.6 to 12.8%.
Phenanthrene Pyrene 4-Aminobenzoic acid Phosphorescence

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

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

"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

"Continuous-flow Determination Of Reserpine By Oxidation With Periodate Ion And Catalysis By Manganese(II) In Solution Or By An MnO2 Reactor"
Anal. Chim. Acta 1990 Volume 233, Issue 2 Pages 235-241
S. R. Varma, J. Martinez Calatayud and Horacio A. Mottola

Abstract: Reserpine oxidation by periodate, catalyzed by Mn(II) or Mn(IV), in acidic medium, produced yellow 3,4-didehydroreserpine which could be detected spectrophotometrically at 385 nm. The solid MnO2 was thermally embedded on the walls of Tygon tubing and incorporated in the flow system in an open-tubular reactor. Both methods were easily adapted for rapid, repetitive continuous-flow determinations. The detection limit with the Mn(II) system was 5.0 or 7.5 µM, the coefficient of variation (n = 10) was ~2% and the throughput was 60 samples h-1. The figures for the MnO2 reactor were not as good, but this method was simpler and showed remarkable stability and reproducibility. Fluorimetric detection could be used if a lower detection limit was required. The methods were used to analyze single reserpine tablets and Rauwolfia serpentina standard powders.
Reserpine Pharmaceutical Spectrophotometry

"Detection Of Slightly Soluble Systems By Means Of Organized Media In Flow Injection Analysis"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 239-245
B. Moreno Cordero and J. L. Perez Pavon

Abstract: The detection of species that are slightly soluble in water is possible by using an appropriate organized medium in flow injection analysis. Triton X-100 (I) was used to give stable aqueous solution of 1-(2-pyridylazo)-2-naphthol, which were used to determine rare-earth metals, with detection at 560 nm. Detection limits for La, Pr, Nd, Er, Tm and Y ranged from 0.16 to 0.56 µM. The effect of pH on signals was studied. I was also used to stabilize strongly acidic solution (3.6 M HCl) of arsenazo III, which were used for determination of U and Th, with detection at 665 nm.
Metals, rare earth Lanthanum Praseodymium Neodymium Erbium Thulium Yttrium pH Uranium Thorium-232 Spectrophotometry

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

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

"Determination Of Nitrate With A Flow Injection System Combining Square-wave Polarographic Detection With Online Deaeration"
Anal. Chim. Acta 1990 Volume 234, Issue 2 Pages 475-478
Mouna Noufi, Ch. Yarnitzky and Magda Ariel

Abstract: The catalytic reaction between NO3- and UO22+ is used to provide a simple, rapid, sensitive and accurate method for determining NO3- in river and potable water. The carrier (H2O) and reagent (0.2 M KCl - 0.02 M HCl - 0.2 mM - UO22+) streams are pumped (0.6 mL min-1) into a coil (30 cm x 0.5 mm) and 200 µL of aqueous NO3- is injected. A diagram of the apparatus is given. Voltammetry is performed with reference to an Ag - AgCl (3 M KCl) electrode, delay 4 s, scan rate 100 mV s-1 and a potential range of -0.6 to -1.1 V. The calibration graph is rectilinear for 5 to 60 µM-NO3-1, with a detection limit of 2 µM. The effect of anions on the reduction is studied.
Nitrate River Water Polarography Electrode Voltammetry

"Exchangeable Immobilized Enzyme Reactor For Enzyme Inhibition Tests In Flow Injection Analysis Using A Magnetic Device. Determination Of Pesticides In Drinking Water"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 113-117
Ralf Kindervater, Wolfgang K&uuml;nnecke and Rolf D. Schmid

Abstract: A flow injection analysis system is described for rapid automated enzyme inhibition testing. Sample in a carrier stream is mixed with a portion of enzyme immobilized on magnetic particles, and the amount of inactivated enzyme is determined. Exchange of used enzyme substrate is achieved with magnetic devices, which can be switched off to release bound material. The magnetic reactor is described and illustrated; its flow resistance is excellent. The system was applied in the determination of pesticides (carbofuran and malaoxon) in drinking water, with use of acetylcholinesterase, the activity of which was determined spectrophotometrically or electrochemically. The response was different for the two pesticides, but the limit of detection was 0.5 µg l-1. One analysis, including calibration, took 20 min.
Pesticides Water

"Integrated Photochemical Reaction/electrochemical Detection In Flow Injection Systems: Kinetic Determination Of Oxalate"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 227-232
Luis E. Leon, Angel R&iacute;os, M. D. Luque de Castro and Miguel Valc&aacute;rcel

Abstract: A method is described for the kinetic electrochemical determination of photosensitive compounds, by using a novel electrochemical cell incorporating an optical fiber (described and illustrated). The cell allows irradiation of the sample - reagent mixture and simultaneous detection of product. The system was applied to the oxalate - Fe(III) reaction, with amperometric detection of the Fe(III) produced at +900 mV. Calibration graphs were rectilinear from 4 to 13 and 13.4 to 134 µg mL-1 of oxalate, with coefficient of variation (n = 10) of 7.8 and 3.8% at 5.3 and 13.4 µg mL-1, respectively. The detection limit was 3 µg mL-1 of oxalate. The sampling rate was 20 h-1. The kinetic parameters of the system were studied.
Oxalate Electrochemical analysis

"Online Continuous-flow Extraction System In Liquid Chromatography With Ultraviolet And Mass Spectrometric Detection For The Determination Of Selected Organic Pollutants"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 119-126
A. Farran, J. L. Cortina and J. de Pablo, D. Barcel&oacute;

Abstract: A system is described which allows UV detection and MS characterization of ng amounts of pesticides in water. It involves completely continuous-flow analysis, with extraction with heptane, a PTFE membrane separator, separation on a column of Spherisorb ODS, and detection at 220 nm and by MS. Extraction varied from 60% (for organophosphorus pesticides and the degradation product 2,4,5-trichlorophenol) to 100% for chlorophenoxy acids, except for the degradation product 4-nitrophenol (10%). The limit of detection was 200 to 400 pg with UV detection. Tetrachlorvinphos was determined in a spiked river water at 1 mg L-1 by MS with selected-ion monitoring.
Pesticides Tetrachlorvinphos 2,4,5-Trichlorophenol River LC Mass spectrometry Sample preparation

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

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

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

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

"Application Of A Capillary Flow Cell To Sophisticated Flow Injection Systems"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 141-151
C. Thommen, A. Fromageat, P. Obergfell and H. M. Widmer

Abstract: The use is described of a low-volume flow cell for detection in flow injection analysis. It comprises a capillary, through which the carrier stream flows, and optical fibers which transmit and collect light, through the capillary. The difference between sample- and reagent-injection flow systems was studied by using the flow cell. The dynamic range of sample-injection systems can be extended by using gradient techniques, but this is not so for reagent injection. The detector was used in a mixed aqueous organic system in flow injection extraction, without prior phase separation. Although the detection limit for a model compound (a pesticide) was lower after phase separation (1 mg L-1 vs. ~30 mg l-1), the cited method eliminated the need for the problematical phase separation.

"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

"Determination Of Quinine And Quinidine By Continuous-flow Chemiluminescence"
Anal. Chim. Acta 1990 Volume 236, Issue 2 Pages 463-468
Ioanna I. Koukli and Antony C. Calokerinos

Abstract: A chemiluminescence analyzer. [Koukli et al., Analyst (London), 1988, 113, 603] with an air-segmented continuous-flow manifold (diagram given) was used to determine quinine and quinidine by their sensitizing action on the reaction between Ce(IV) and SO32-. The Ce(IV) solution in 0.1 M H2SO4 was segmented with air before introduction of the analyte solution also in 0.1 M H2SO4. The stream was de-bubbled, then mixed with the SO32- solution before entering the coil for generation of chemiluminescence. The calibration graph for either analyte (log-log scale for quinine) was rectilinear from 5 to 500 µg mL-1, and the analysis rate was 40 h-1. The limit of detection was 0.64 and 1.6 µg mL-1 for quinidine and quinine, respectively. The method was successfully applied to pharmaceuticals.
Quinine Quinidine Pharmaceutical Chemiluminescence

"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

"Flow Injection Enzyme Immunoassay Of Haptens With Enhanced Chemiluminescence Detection"
Anal. Chim. Acta 1990 Volume 237, Issue 2 Pages 285-289
A. A. Arefyev, S. B. Vlasenko, S. A. Eremin, A. P. Osipov and A. M. Egorov

Abstract: A non-equilibrium flow injection enzyme immunoassay for thyroxine (model hapten) is described, involving affinity separation of the immunocomplex of horseradish peroxidase-labelled antibodies and antigen from the free labelled antibodies. The analyte solution and peroxidase - IgG conjugate were introduced by a two-channel microinjector into two streams of 0.05 M Tris - HCl buffer (pH 8.5) containing 0.05% of polysorbate 20. The reaction zone was incubated, the stream was combined with solution of luminol, p-iodophenol and H2O2 and the mixture was fed into the flow cell of an LKB-1250 luminometer. The chemiluminescence intensity was measured for at least 3 min. The detection limit of the antigen was 12 pM within 5 min and the coefficient of variation was 10%.
Thyroxine Chemiluminescence Immunoassay

"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

"Segmental Flow Injection Analysis: Device And Applications"
Anal. Chim. Acta 1990 Volume 238, Issue 1 Pages 183-190
Li-Ching Tian, Xiao-Ping Sun, Yi-Yun Xu and Zheng-Liang Zhi

Abstract: The cited system possesses features of both flow injection and continuous-flow analysis. The sample zone is segmented by only two air bubbles and contained a valve designed so that sample and bubbles could be quantitatively injected into the carrier stream. The system provided residence times of >10 min at temperature up to 95°C without loss of peak height or sampling frequency, and owing to good reproducibility, analysis could be carried out before the equilibrium state was reached. The method was demonstrated by the determination of amino-acids in tea with the ninhydrin reagent, giving recoveries from 97 to 106%, a limit of detection of 5 mg L-1 and a coefficient of variation (n = 3) of 2.8%. Other applications included determination of ammonium and V in water, Cu in ores and creatine in urine.
Ammonium Vanadium Copper Creatine Water Urine Geological

"Amperometric Flow Injection System With An Immobilized Enzyme Reactor For The Highly Selective Detection Of Phosphate And Online Amplification By Substrate Recycling"
Anal. Chim. Acta 1990 Volume 238, Issue 2 Pages 339-343
Toshio Yao, Naokazu Kobayashi and Tamotsu Wasa

Abstract: The method of Yao et al. (Ibid., 1990, 231, 121) was applied in the determination of PO43- with a reactor of co-immobilized purine nucleoside phosphorylase and xanthine oxidase. The response was rectilinear from 1 to 500 µM-PO43- with a limit of detection of 0.3 µM for 20 µL. The coefficient of variation (n = 7) were 4.9 and 2.2% for 2 µM and 50 µM, respectively. In the presence of alkaline phosphatase, the reactor was twenty times more sensitive due to substrate recycling but responded also to nucleotides and pyrophosphate.
Phosphate Amperometry

"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

"Flow Injection Chemiluminometric Analysis Of Some Steroids By Their Sensitizing Effect On The Bromate-sulfite Reaction"
Anal. Chim. Acta 1990 Volume 239, Issue 2 Pages 195-202
Aristotelis B. Syropoulos, Evangelos G. Sarantonis and Antony C. Calorkerinos

Abstract: The solution of cortisone (I), hydrocortisone, corticosterone, testosterone (II) or progesterone (III) were injected into 2 mM NaBrO3 in 20 mM H2SO4 at 1.5 mL min-1. After mixing with 0.5 mM SO32- the luminescence was measured with a photomultiplier. The responses were rectilinear between 0.5 and 5 to 6 µg mL-1 except for I which was from 0.5 to 20.0 µg mL-1, with limits of detection between 0.1 and 0.4 µg mL-1. The coefficient of variation (n = 6) for 0.5 and 4.0 µg mL-1 of III were 2.3 and 0.5%, respectively, which were typical for all the steroids. Recoveries of II from various excipients were between 95.8 and 104.0%.
Steroids Hydrocortisone Corticosterone Testosterone Progesterone Chemiluminescence

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

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

"Determination Of Nanoequivalent Amounts Of Organic Halogens By Sample Combustion-flow Injection Conductimetry With Online Preconcentration"
Anal. Chim. Acta 1990 Volume 241, Issue 1 Pages 71-82
I. G&aacute;cs and K. Payer

Abstract: The sample was heated at 950°C in a stream of O2 and the decomposition products containing halogens were absorbed in a capillary denuder tube coated with an aqueous solution of a hydrazine monohydrohalide. The hydrohalic acid formed in the liquid film was eluted with a solution of the absorbant to a conductivity microdetector where the change in specific conductance due to the acid was rectilinearly related to the halogen content. The method was tested with 14 compounds and was applied to the analysis of river and drinking water and to industrial atmospheres. The limit of detection for the volatile organic halogen content in water was 0.01 µg L-1 and 0.2 µg m-3 for the total organic halogen content in air. For 3 to 100 nanoequivalents of Cl, the precision (95% confidence limits) (n = 5) was 5%.
Organic, halogenated Water Water River Conductometry

"Flow-through Calcium-selective Electrode: Application In Flow Injection Analysis And Ion Chromatography"
Anal. Chim. Acta 1991 Volume 242, Issue 1 Pages 65-72
N. Kolycheva, H. M&uuml;ller

Abstract: The possible use was studied of a solid-contact flow-through Ca2+-selective electrode based on a membrane containing tetratolyl-m-xylylenediphosphine dioxide (cf. Bessis et al., Zh. Anal. Khim., 1988, 43, 1769) as a potentiometric detector in flow injection analysis and non-suppressed ion chromatography. The composition and thickness of the membrane influence the detection limit and selectivity. The detection limit is ~1 µM, and 100-fold amounts of alkali-metal ions, NH4+ or Mg2+ do not interfere. In ion chromatography, the sensitivity of the detector is about two orders of magnitude better than that of a commercial detector relative to other alkaline-earth and heavy metals.
Metals, alkaline earth Metals, heavy HPIC Electrode Potentiometry

"Application Of A Polyaniline - Nafion Composite Electrode To The Determination Of Alkali And Alkaline-earth Metal Ions Using Flow Injection Analysis And Ion Chromatography"
Anal. Chim. Acta 1991 Volume 246, Issue 2 Pages 275-281
Jung-Yu Sung and Hsuan-Jung Huang

Abstract: A polished Pt electrode was coated with Nafion by a published method and then with a polyaniline film by immersing the electrode in stirred 0.5 M Na2SO4 - 0.1 M H2SO4 - 0.1 M aniline; the electrode potential was scanned (20 mV s-1) from 0.00 to +1.10 V and back to -0.20 V for three complete successive cycles. The prepared electrode was used as a detector in the separation and determination of alkali and alkaline-earth metal ions by flow injection amperometry or ion chromatography. In the former technique, the prepared electrode, together with the reference electrode, was embedded in a thin-layer PTFE flow cell; the carrier solution was 0.1 mM HNO3. Detection limits were of the order of 1 µM for all analytes. In ion chromatography, a Wescan cation-exchange column (5 cm x 4.6 mm) was used with 1.5 mM HNO3 (pH 2.59) or 1.0 mM HNO3 - 2.0 mM ethylenediamine (pH 6.11) as mobile phase. Detection limits were 0.2 µM for Na+ and K+ and 10 µM for the alkaline earths.
Metals, alkali Metals, alkaline earth Sodium Potassium Amperometry HPIC Electrode Electrode

"Photocured Polymers In Ion-selective Electrode Membranes. 5. Photopolymerized Sodium-sensitive Ion-selective Electrodes For Flow Injection Potentiometry"
Anal. Chim. Acta 1996 Volume 334, Issue 1-2 Pages 133-137
J. R. Farrell, P. J. Iles,* and T. Dimitrakopoulos

Abstract: A drop of membrane mixture (described), which contained the ionophore ETH 157 [o-phenylenedioxybis-(N-benzyl-N-phenylacetamide)], was placed over the Cu substrate of a solid-contact electrode and cured. Equilibrium experiments were run against an Ag/AgCl/saturated KCl/10% KNO3 double-junction reference electrode in water or 0.1 M MgCl2. The photocured sodium ISE exhibited a log.-linear relationship for 1-1000 mM Na+ and a detection limit of 20 µM. The response was independent of pH in the range 4-9.6. FIA was performed in a cell with separate flow lines for the ISE and the Ag/AgCl reference wire electrode. The carrier and reference streams, which both contained 0.1 M MgCl2 to maximize the activity for Na+, were both pumped at 1.9 ml/min. The electrode exhibited a log.-linear relationship for 1-1000 mM Na+ and a detection limit of 40 µM.
Sodium Electrode Electrode Potentiometry

"Electrochemical Response Of A Polypyrrole-dodecylsulfate Electrode With Multicharged Cations And Vitamins B1 And B6. Application As A Microsensor In Flow Injection Analysis"
Anal. Chim. Acta 1996 Volume 336, Issue 1-3 Pages 47-56
R. Carabias Mart&iacute;nez*, F. Becerro Dom&iacute;ngueza, I. M. Sierra Garc&iacute;aa, J. Hern&aacute;ndez M&eacute;ndeza, R. C&oacute;rdova Orellanab and R. Schrebler Guzm&aacute;nb

Abstract: The cited electrode was prepared by electropolymerization on to a Pt or vitreous C electrode (20 mm2 area) from a solution containing 0.23 M pyrrole/0.05 M SDS in 80% acetonitrile. A potential of +1.4 V vs. SCE was applied for 5 min followed by 5 potential scans from +0.7 V to -1.3 V and then a constant potential of +0.7 V for 5 min. The amperometric response of the electrode to multicharged cations (Cu2+, Sr2+, Ba2+, Mg2+ and Al3+) and vitamins [B1 (thiamine) and B6] was investigated by cyclic voltammetry by scanning the potential from +0.7 to -1.3 V at 25 mV/s. A linear relationship between the cathodic current at -0.8 V and the analyte concentration was obtained for concentrations up to 0.1-1 mM. The detection limits were 1 µM for all analytes except vitamin B6 (7.5 µM). RSD (n = 10) for concentrations of 0.1 mM were 1.7% (Ba2+) to 8% (thiamine). The electrode was used as an amperometric detector in a single channel FIA system with 10 mM glycine as the carrier stream (1.54 ml/min) and an injection volume of 200 µL. Linear calibration graphs were obtained for all analytes up to 1 mM except Al3+ (up to 0.1 mM). The detection limits were 0.1-0.34 µM. RSD (n = 10) were 0.6-1.6% at the 0.1 mM level.
Cations Copper(II) Strontium(II) Barium(2+) Magnesium(II) Aluminum(III) Vitamin B1 Vitamin B6 Amperometry Electrode Electrode Electrode Voltammetry Sensor

"Determination Of Ascorbic Acid In A Mixture Of Ascorbic Acid And Uric Acid At A Chemically Modified Electrode"
Anal. Chim. Acta 1997 Volume 343, Issue 1-2 Pages 49-57
Zhiqiang Gao*, Kok Siong Siow, Adeline Ng and Yimin Zhang

Abstract: The electrochemical behaviours of ascorbic acid (AA) and uric acid (UA) at a vitreous C electrode modified with 3,4-dihydroxybenzaldehyde were investigated by voltammetry and amperometry. At pH 7.4, the anodic peak due to the oxidation of AA occurred at 0.15 V (vs. SCE) at the modified electrode, which was at least 250 mV more negative than the voltage required at an unmodified electrode. The modification of the electrode had no effect on the oxidation of UA. The modified electrode was employed in a flow injection system for the amperometric determination of AA in the presence of UA. A thin layer flow-through electrochemical cell was used equipped with the working electrode maintained at 0.15 V, a SCE as the reference electrode and a Pt foil counter electrode. The carrier stream (1 ml/min) was 0.1 M phosphate buffer at pH 7.4. A linear response was obtained for 0.7 µM- to 1 mM AA, the detection limit was 0.3 µM and the RSD (n = 50) for 10 µM-AA was 4%. The system was used to determine AA in single- and multi-vitamin tablets.
Ascorbic acid Uric acid Pharmaceutical Amperometry Voltammetry Electrode Electrode

"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

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

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

"Coupling Of Membrane-immobilized Enzyme Reaction And Heteropoly Acid Luminol Chemiluminescence Reaction For The Determination Of Adenosine-5'-triphosphate"
Anal. Chim. Acta 1997 Volume 349, Issue 1-3 Pages 159-164
Terufumi Fujiwara, Kiyomi Kurahashi and Takahiro Kumamaru*

Abstract: A method based on the combination of a membrane-immobilized enzyme reactor with a flow injection (FI) chemiluminescence (CL) detector was developed and applied to the determination of >10 nM adenosine-5'-triphosphate (ATP). Alkaline phosphatase from Escherichia coli was immobilized on a nitrocellulose membrane by adsorption. When a sample of ATP was circulated in this enzyme reactor, orthophosphate was produced from alkaline phosphatase-catalyzed hydrolysis of ATP. In the FI system, the enzymatically generated phosphate in the sample solution was led into the loop of an injection valve followed by its conversion into molybdovanadophosphoric acid by mixing with a reagent mixture containing ammonium molybdate, ammonium metavanadate and sulfuric acid. The heteropoly acid subsequently reacts with luminol in a basic medium to produce CL, proportional to ATP concentration. A detection limit (DL) of 10 nM and a dynamic range extending from the DL to 10 µM were obtained for ATP. The relative standard deviation for five replicate measurements of 1.0 µM ATP was 6.6%. 18 References
Chemiluminescence Sensor

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

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

"7,7,8,8-Tetracyanoquinodimethane Chemiluminescence Sensitized By Rhodamine B On Surfactant Bilayer Membrane Assemblies For Determination Of Sulfide By A Flow Injection Method"
Talanta 1989 Volume 36, Issue 4 Pages 505-508
Qian Xue-Xin, Guo Yue-Ying, Masaaki Yamada*, Eigo Kobayashi and Shigetaka Suzuki

Abstract: Optimum conditions have been established for the cited analysis. The two reagent streams (7.5 mL min-1) comprising 0.1 mM 7,7,8,8-tetracyanoquinodimethane - 0.5 mM rhodamine B - 40% acetonitrile and 1 mM dioctadecyldimethylammonium chloride - 1 mM NaOH, respectively, were separately heated in 1-m PTFE coils at 57°C. The streams were then mixed before injection of sample solution (30 µL) and measurement of the chemiluminescence signal by using a photomultiplier tube. The calibration graph was rectilinear from 0.05 to 5 µM-S2- ,and the detection limit was 0.01 µM. The coefficient of variation (n = 19) was 3.0% for 0.3 µM-S2-. The effects of various common ions were studied. Bivalent Mn and Fe and species forming a ppt. with S2- interfere. The method was applied to determine S2- in hot-spring water, and results agreed with those obtained by iodimetry.
Sulfide Environmental Chemiluminescence

"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

"Determination Of The Flotation Collector Ethyl Xanthate By Flow Injection Analysis"
Talanta 1990 Volume 37, Issue 11 Pages 1067-1070
Miloslav Kopanica, Vra Star&aacute; and Anton&iacute;n Troj&aacute;nek

Abstract: A flow-through cell suitable for voltammetric detection was constructed from Plexiglas (diagram given) containing a carbon-paste disc working electrode of silica gel - ceresine - graphite (14:43:43) and a Ag - AgCl reference electrode. Sample solution containing ~5 mg L-1 of K ethylxanthate was injected into the carrier stream of 0.1 M KNO3 (0.6 mL min-1) and voltammetric scanning (0.5 V s-1) was performed from -0.15 V to +0.9 V. Calibration graphs were rectilinear for 0.1 to 10 mg L-1 of ethylxanthate. The detection limit was 0.4 mg l-1. Interference from cations was overcome by addition of EDTA. The method was successfully applied to the analysis of ore.
Ethyl xanthate Geological Voltammetry Electrode

"Determination Of Thiamine By Continuous-flow Chemiluminescence Measurement"
Talanta 1990 Volume 37, Issue 11 Pages 1043-1048
Nikos Grekas and Antony C. Calokerinos*

Abstract: Sample solution stream was mixed with the oxidant stream of 5 mM ferricyanide solution in 1 M NaOH. The mixed stream was pumped to a spiral glass flow cell in front of a photomultiplier; the output of the photomultiplier tube was fed to an operational amplifier and then to a recorder. The effect on chemiluminescence intensity of sample and oxidant flow rates and concentration. of ferricyanide and alkali solution were investigated. Calibration graphs were rectilinear from 20 to 500 µM-thiamine nitrate or hydrochloride. The detection limit was 9 µM. In the analysis of pharmaceutical formulations, ascorbic acid interfered.
Thiamine Pharmaceutical Chemiluminescence

"Indirect Determination Of Chloride And Carbonate By Reversed Flow Injection Analysis Coupled With Atomic Absorption Spectrometry And Inline Preconcentration By Precipitation"
Talanta 1990 Volume 37, Issue 12 Pages 1123-1128
Fatima T. Esmadi, Maher A. Kharoaf and Abdulrahaman S. Attiyat*

Abstract: Chloride and CO3-1 were determined by precipitation as AgCl and CaCO3 in a Tygon tube containing glass beads, dissolution of the ppt. in Na thiosulfate solution and HCl, respectively, and analysis by reversed flow injection AAS. The signal obtained for the cation was proportional to the concentration. of anion in the sample. Calibration graphs were rectilinear from 0.5 to 16 and 1 to 14 µM for Cl- and CO32-, respectively, with detection limits of 0.3 and 0.5 µM. Corresponding recoveries and coefficient of variation were 94 and 3.7 and 92 and 1.6% (n = 10). Thiocyanate, I- and Br- interfered with Cl- and PO43- interfered with CO32-. The method was fairly selective and sensitive and had a lower detection limit and higher sampling frequency than other methods.
Chloride Carbonate Spectrophotometry

"Determination Of Chloramphenicol By Coupling A Continuous Reduction System To An Atomic Absorption Spectrometer"
Talanta 1990 Volume 37, Issue 12 Pages 1129-1132
R. Montero, M. Gallego and M. Valcarcel

Abstract: Sample solution (90 µL) at pH 3.7 to 4.2 was injected into the water carrier stream and passed through the Cd or Zn reductor column where the nitro-group was reduced. The released Cd or Zn cations were then determined by AAS; peak height was proportional to the concentration. of drug injected. Chloramphenicol could be determined in the range 2 to 30 µg mL-1 and the sampling frequency was 150 h-1. The detection limits were 0.7 and 1.3 µg mL-1 for the Zn and Cd columns, respectively; the corresponding recoveries and coefficient of variation (n = 7) were 99.5 and 1.1 and 99.8 and 2.1%. The method was applied to pure powders, capsules, tablets, oral suspensions and eye ointments. Advantages over the previously reported batch method included low sample and reagent consumption, lower cost and higher sensitivity and precision.
Chloramphenicol Spectrophotometry

"Potentiometric Flow Injection Determination Of Iodide And Iodine"
Talanta 1990 Volume 37, Issue 3 Pages 313-316
David E. Davey, Dennis E. Mulcahy and Gregory R. O'Connell

Abstract: A flow injection system and detection-cell manifold (cell volume 4 µL) with Orion 94-06A AgI - Ag2S ion-selective and 90-02 double-junction reference electrodes were used for determination of I- in a reagent stream of 0.1 M KCl, or iodine was determined after online reduction with 0.1 M Na2S2O5. Maximum throughput was 360 or 60 samples h-1 for I- and iodine, respectively. The lower limits of determination were ~5 µM. The method was applied to determination of I- in Iodine Colorless BPC34 and iodine and I- in betadine antiseptic, and results agreed well with those obtained by AgNO3 titrimetry.
Iodide Iodine Potentiometry

"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

"Flow Injection Spectrophotometric Determination Of Cyanide By The Phenolphthalein Method"
Talanta 1997 Volume 44, Issue 4 Pages 545-551
Amin T. Haj-Hussein*

Abstract: Aqueous sample (50 µL) was injected into a carrier stream of 1 mM NaOH which merged with premixed streams of 0.3 mM phenolphthalin and 0.2 M carbonate buffer of pH 10.3. The flow passed through a column (6 cm x 1.4 mm i.d.) packed with 80 mg CuS particles (0.8-1.2 mm) where phenolphthalein was produced, and then to a detector where the absorbance was measured at 552 nm. The optimal flow rate was 1.08 ml/min. The calibration graph was linear for 0.6-4.3 ppm cyanide and the RSD were ~1%. The detection limit was 0.1 ppm. Interferences were investigated. The method was applied to well water. Recoveries were 98.7-101.5%.
Cyanide Well Spectrophotometry

"Equilibrium And Kinetic Properties Of A Fast Iminodiacetate Based Chelating Ion Exchanger And Its Incorporation In A FIA ICP-AES System"
Talanta 1997 Volume 44, Issue 6 Pages 1037-1053
Payman Hashemi* and &Aring;ke Olin

Abstract: Chelating ion-exchangers based on cross-linked agarose (Novarose; Scand Inovata AB, Stockholm, Sweden) were characterized for their metal binding abilities. Material with a metal binding capacity of 55 µmol/ml showed fast adsorption and desorption of Cu(II), Cd(II), Ni(II) and Ca(II) under both batch and column modes. When incorporated in a column (0.5 cm x 6 mm i.d.) in a FIA system (diagram given) quantitative adsorption of Cu(II), Cd(II) and Ni(II) occurred at flow-rates of up to 110 ml/min. Elution was achieved with 1 mL 1 M HCl at 4 ml/min for ICP-AES detection. Calibration graphs were linear for 15-120, 45-350 and 90-700 ng Cd(II), Cu(II) and Ni(II), respectively, and the detection limits were 2, 5 and 10 ng, respectively. RSD were 1.3-2.4%. The method was applied determine Cu and Cd in tap water at a flow rate of 60 ml/min.
Cadmium(2+) Calcium(2+) Copper(II) Nickel(II) Water Spectrophotometry

"Determination Of Bromide Using Flow Injection And Chemiluminescence Detection"
Analyst 1989 Volume 114, Issue 8 Pages 951-954
Issam M. A. Shakir and Azad T. Faizullah

Abstract: The aqueous sample (60 µL) was injected into 50 mM KBrO3 - 0.125 M HNO3 (3 mL min-1) before passing either through a by-pass tube or through a mini-column of Dowex HCR-W (16 to 40 mesh) to remove cations. The mixture was then merged with a stream of 5 µM-luminol - 5 mM H2O2 in a reaction coil and the chemiluminescence was measured at 417 nm. The calibration graph was rectilinear for 1 to 100 µg mL-1 of Br-, and the detection limit was 3.75 pg. The effects of various foreign ions were studied; I- interfered seriously at >1 µg mL-1. The aqueous sample (60 µL) was injected into 50 mM KBrO3 - 0.125 M HNO3 (3 mL min-1) before passing either through a by-pass tube or through a mini-column of Dowex HCR-W (16 to 40 mesh) to remove cations. The mixture was then merged with a stream of 5 µM-luminol - 5 mM H2O2 in a reaction coil and the chemiluminescence was measured at 417 nm. The calibration graph was rectilinear for 1 to 100 µg mL-1 of Br-, and the detection limit was 3.75 pg. The effects of various foreign ions were studied; I- interfered seriously at >1 µg mL-1.
Bromide Chemiluminescence

"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

"Tensammetric Determination Of Phospholipids In Batch And Flow Injection Systems"
Analyst 1989 Volume 114, Issue 12 Pages 1593-1596
Hendrik Emons, Thomas Schmidt and Karel Stul&iacute;k

Abstract: Phospholipids in a flow system can be detected from the non-equilibrium differential capacitance - time response of a hanging-Hg-drop electrode at -1.8 V with an a.c. (60 Hz) amplitude of 20 mV. At this applied potential the reponse is constant at flow rates 0.5 mL min-1, but at higher flow rates increases rectilinearly with the square root of the flow rate; good reproducibility is demonstrated for successive 10.9 µg injections of phosphatidylcholine at 0.8 mL min-1 when a fresh Hg drop was formed before each injection. The rectilinear range depended on the individual phospholipids, but included the range 0.5 to 5 µg for all compounds studied. Phase transitions in the adsorbed layer as the amount of adsorbed phospholipid increases can cause reproducible discontinuities in the calibration graphs, as is shown to occur for sphingomyelin at 5 µg injected. Phospholipids in a flow system can be detected from the non-equilibrium differential capacitance - time response of a hanging-Hg-drop electrode at -1.8 V with an a.c. (60 Hz) amplitude of 20 mV. At this applied potential the reponse is constant at flow rates 0.5 mL min-1, but at higher flow rates increases rectilinearly with the square root of the flow rate; good reproducibility is demonstrated for successive 10.9 µg injections of phosphatidylcholine at 0.8 mL min-1 when a fresh Hg drop was formed before each injection. The rectilinear range depended on the individual phospholipids, but included the range 0.5 to 5 µg for all compounds studied. Phase transitions in the adsorbed layer as the amount of adsorbed phospholipid increases can cause reproducible discontinuities in the calibration graphs, as is shown to occur for sphingomyelin at 5 µg injected.
Phospholipids Sensor Electrode

"Determination Of Selenium In Blood Plasma And Serum By Flow Injection Hydride Generation Atomic Absorption Spectrometry"
Analyst 1990 Volume 115, Issue 3 Pages 275-278
Kieran McLaughlin, Darioush Dadgar, Malcolm R. Smyth and Dorothy McMaster

Abstract: A flow injection hydride generation atomic absorption spectrometric (AAS) method has been used to determine the selenium concentrations of human serum and plasma samples following digestion with nitric, sulfuric and perchloric acids. In the hydride generation process, reduction was carried out by sodium tetrahydroborate to produce a hydride that was atomized in a flame-heated atomisation cell. The method had a detection limit of 1.2 ng mL-1 and a sensitivity of 2.1 ng mL-1. Within-run precisions of 5.8% at 20 ng mL-1 and 4.5% at 80 ng mL-1, and between-run precisions of 4.8% at 69 ng mL-1 and 3.4% at 80 ng mL-1 were obtained. An inter-laboratory comparison study with a graphite furnace AAS method was carried out and the results showed excellent agreement. The flow injection method of sample introduction allowed the use of a sample volume of 330 µL with an injection rate of 90 injections per hour. Plasma or serum (2 ml) was digested at 140°C for 20 min (temp. raised to 140°C over 20 min) with 5 mL of 16 M HNO3 and cooled; 2.5 mL of 18 M H2SO4 and 1 mL of 11.6 M HClO4 were added and the temperature was increased to 140°C (held for 15 min), then to 205°C over 15 min (held until white fumes appeared). The residue was cooled, then heated at 95°C for 30 min with 5 mL of 5 M HCl. After cooling and dilution to 25 mL with water, a 330 µL portion was injected into the flow injection hydride generator with 1% (w/v) NaBH4 (3.9 mL min-1) - 1 M HCl (5.4 mL min-1). The H2Se produced was carried by the Ar stream to the heated silica cell of the AAS instrument and atomized at 900°C. Absorbance was measured at 196 nm. The detection limit of Se was 1.2 ng mL-1; sensitivity was 2.1 ng mL-1. Within- and between-run precisions were 4.5 and 3.4%, respectively, at 80 ng mL-1 of Se. Recoveries were 95 to 109%. Results from an inter-laboratory comparison study with graphite-furnace AAS agreed well.
Selenium Blood Plasma Blood Serum Spectrophotometry Sample preparation

"Rapid Differential Flow Injection Of Phosphorus Compounds In Wastewater By Sequential Spectrophotometry And Inductively Coupled Plasma Atomic Emission Spectrometry Using A Vacuum Ultraviolet Emission Line"
Analyst 1990 Volume 115, Issue 8 Pages 1055-1058
Jamshid L. Manzoori, Akira Miyazaki and Hiroaki Tao

Abstract: Sample was injected into 0.5 M HNO3 as carrier stream, which was mixed with a reagent stream comprising (NH4)6Mo7O24 and NH4VO3 in HNO3. Phosphate was determined as molybdovanadophosphate by spectrophotometry at 470 nm, and the eluate was fed to an ICP-AES system for determination of total P at 177.499 nm. The calibration graphs were rectilinear for 200 µg mL-1 of P for both detection methods, and the limits of detection were 0.8 and 0.5 µg mL-1, respectively. Of several common ions examined, only Cr interfered in the spectrophotometric method. The coefficient of variation was 2.0% for 10 µg mL-1 of P (n = 11). Eighty samples per hour could be analyzed. The method was applied to treated sewage and metal-plating waste water.
Phosphorus Waste Spectrophotometry

"Coulometric Detector Cell For Use With Flow Injection"
Analyst 1990 Volume 115, Issue 9 Pages 1247-1249
Liliana Ilieva Ilcheva and Anastas Dimitrou Dakashev

Abstract: A cell for constant potential coulometric detection is described and illustrated comprising of a porous working-electrode containing Pt particles and a SCE of large surface area. The SCE was not polarised, the potential was kept constant and it served both as the reference and counter electrode. The cell was demonstrated by the determination of Tl(I) by oxidation to Tl(II) in 0.1 M HCl. The response was rectilinear from 0.02 to 0.17 µeq with a limit of detection of 8 peq. Between 0.006 and 5.8 µg were analyzed with a coefficient of variation (n = 5 to 14) of 3 to 6%.
Thallium(I) Coulometry Electrode

"Simultaneous Determination Of Hydroxylamine And Cyanide In Formulations Containing Pralidoxime Salts By Flow Injection"
Analyst 1990 Volume 115, Issue 9 Pages 1239-1242
David Utley

Abstract: A flow injection method is described for the simultaneous determination of cyanide and hydroxylamine which are known decomposition products of formulations containing pralidoxime salts used in the treatment of anticholinesterase poisoning. By using the diffusion of HCN from the carrier stream followed by amperometric detection, high selectivity and sensitivity and a wide dynamic range can be achieved. Hydroxylamine is determined by its oxidation with iodine to nitrite which can then be determined colorimetrically. The gas diffusion unit effectively acts as a stream splitter for the two analytes allowing their simultaneous determination from a single sample injection. The performance of the system and its applicability to thermally stressed pralidoxime solutions are described. The HCN was determined by diffusion from a carrier stream of 0.2 M citrate buffer (pH 3.2) into a collection stream of 0.1 M NaH2BO3. Amperometric detection with a Ag working electrode vs. Ag - AgCl was used. The response was rectilinear from 10 to 100 µg mL-1 of KCN and the coefficient of variation (n = 5) were 1.0% over the range studied. Hydroxylamine was determined in the same carrier stream by oxidation with a stream of iodine reagent followed by reduction of the excess iodine with 0.705 M NaAsO2 and determination of the NO2- by diazocoupling with a 0.2% naphthylethylenediamine solution Detection was at 540 nm. The response was rectilinear from 0.1 to 20 µg mL-1 of hydroxylamine, with a limit of detection of 0.03 µg mL-1. The coefficient of variation (n = 5) was 0.7% over most of the range but was 4.3% for 0.1 µg mL-1.
Hydroxylamine Cyanide Amperometry Electrode

"Flow Injection Of Lithium Ion Using Chromogenic 14-crown-4 Derivatives As Extraction-spectrophotometric Reagents"
Analyst 1990 Volume 115, Issue 9 Pages 1251-1255
Keiichi Kimura, Shin-ichi Iketani, Hidefumi Sakamoto and Toshiyuki Shono

Abstract: A system for flow injection of Li+ has been designed, with use of proton-dissociable chromogenic 14-crown-4 derivatives as the extraction-spectrophotometric reagents, and the analytical conditions have been optimized. This flow injection system showed high selectivity for Li+ reflecting the cation-complexing property of the chromogenic crown ethers. The determination of Li+ in the clinical range in blood under a high Na+ background of 130-160 mM was feasible, with a small sample size (50 µL) and high sampling rate (more than 100 injections per hour), with this method. The proposed extraction-spectrophotometric flow injection system was, therefore, found to be promising for the efficient determination of Li+ in biological samples, such as blood sera, with a high Na+ background. Conditions for the use of six 14-crown-4 derivatives were determined. The best results were obtained with 14-crown-4-dinitrophenol at pH 9.5 for a carrier stream of H3BO3 - KOH and a solvent stream of CHCl3, both at 0.75 mL min-1. Detection was at 410 nm and the coil length was 1 m. The samples e.g., blood sera, and the crown ether were injected into the aqueous and organic streams respectively and the Li+ was extracted in the coil. The response was rectilinear up to 2 mM with a limit of detection of 0.1 µM. High backgrounds caused by the presence of Na+ were compensated for, by preparing calibration standards containing 145 mM Na+.
Lithium Blood Serum Spectrophotometry Sample preparation

"Enzymic Determination Of Ammonia In Food By Flow Injection"
Analyst 1990 Volume 115, Issue 9 Pages 1243-1246
Lucia Canale-Gutierrez, Angel Maquieira and Rosa Puchades

Abstract: Ammonia in food samples was determined by its reaction in an immobilized enzyme reactor containing glutamate dehydrogenase (GIDH) in a flow injection system, by measuring the decrease in the absorbance of ultraviolet radiation by reduced nicotinamide adenine dinucleotide (NADH). There was a linear relationship (r = 0.9995) between peak height and ammonia concentration over the range 0.05-0.6 mM. The detection limit was 0.005 mM for an injection volume of 19 µL. Sampling frequency was 60 h-1 and the precision was better than 1.09% for 11 successive assays. The interference effect of urea and ascorbic acid at concentrations greater than 100 mg per 100 g of product should be taken into account. The interference caused by glycine, creatinine and amino acids is negligible. Only a 20% loss in the activity of the GIDH column was observed after 500 determinations during a 3-month period. Samples were extracted by a modification of the method of Parris and Foglia (Anal. Abstr., 1984, 46, 1F8). The extract was mixed with a carrier stream of 0.1 M phosphate buffer (pH 8), containing 1 mM EDTA, 0.2 mM NADH and 0.1 M oxoglutarate and was passed into a reactor containing immobilized glutamate dehydrogenase and the decrease in the absorbance was measured at 340 nm. The response was rectilinear from 0.05 to 0.6 mM of NH4+ with a limit of detection of 5 µM for a 19 µL injection. The coefficient of variation (n = 11) for 0.25 mM was 1.09%. Urea and ascorbic acid interfered significantly at concentration. >1000 ppm.
Ammonia Food

"Continuous-flow Chemiluminescence Determination Of Isoniazid By Oxidation With N-bromosuccinimide"
Analyst 1990 Volume 115, Issue 9 Pages 1229-1234
Stergios A. Halvatzis, Meropi M. Timotheou-Potamia and Antony C. Calokerinos

Abstract: Powdered tablets equivalent to 200 mg of isoniazid (I) were dissolved in water, filtered and diluted with water to give a final solution containing 0.05 to 20 µg mL-1 of I and 1.0 M-NaOH and 0.5 mM NH3. I was reacted with 15 mM N-bromosuccinimide solution in a continuous-flow chemiluminescence analyzer. (illustrated), reagent and sample flow rates were 2.5 and 3.9 mL min-1, respectively. Detection was by photomultiplication. The limit of detection was 0.024 µg mL-1 and the coefficient of variation (n = 10) for 0.2 and 1.0 µg mL-1 were 3.0 and 0.9% respectively. Recoveries of 0.2 µg mL-1 in the presence of a tenfold concentration. of fifteen additives used as excipients were 97.5 to 103.9% and for 0.2, 0.4 and 0.8 µg mL-1, were 96.0 to 104.2%. The results were compared with those obtained by the BP official method and gave a mean relative difference of 2.4%.
Isoniazid Pharmaceutical Chemiluminescence

"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

"Flow Injection Spectrophotometric Determination Of 4-aminophenazone Based On Diazotization And Coupling Reactions"
Analyst 1990 Volume 115, Issue 11 Pages 1419-1422
AbdulAziz M. Alwehaid

Abstract: Sample is injected into a carrier stream of water (1.5 mL min-1) and merged with a reagent stream (0.7 mL min-1) comprising 33.3 mL of 3 mM 4-nitroaniline, 7 mL of 0.1 M HCl and 5 mL of 20 mM NO2- diluted to 100 mL with water. The mixture passes through a reaction coil (250 cm), and the azo-product is detected at 380 nm. The calibration graph is rectilinear for 50 µg mL-1 of 4-aminoantipyrine, and the detection limit is 0.05 µg mL-1. The coefficient of variation (n = 10) are 0.6 and 0.3% for 4 and 50 µg mL-1, respectively. The sampling rate is 50 h-1.
4-Aminophenazone Spectrophotometry

"Electrocatalytic Detection Of Streptomycin And Related Antibiotics At Ruthenium Dioxide Modified Graphite--epoxy Composite Electrodes"
Analyst 1990 Volume 115, Issue 11 Pages 1447-1450
Donal Leech, Joseph Wang and Malcolm R. Smyth

Abstract: The application of ruthenium dioxide (RuO2) modified electrodes to the electrocatalytic detection of the saccharide-related antibiotics streptomycin, novobiocin and neomycin, at low fixed potentials, was investigated. The RuO2-modified graphite - epoxy composite electrodes give extremely stable and reproducible catalytic oxidation currents for these antibiotics at potentials as low as +0.2 V (versus Ag - AgCl). Rapid quantification at the micromolar level is therefore possible. Standard calibration graphs for streptomycin and neomycin yielded slopes of 4.43 and 0.08 nA µM-1 over the linear ranges of 1.5 x 10^-6 - 2.5 x 10^-4 and 1 x 10^-5 - 2 x 10^-3 M, respectively. Owing to its catalytic oxidation by the Ru(III) - Ru(IV) couple, rather than the Ru(IV) - Ru(VI) transition (which catalyses the oxidation of streptomycin and neomycin), novobiocin could be detected at a lower (+0.2 V) potential, with a sensitivity of 1.31 nA µM-1. Detection limits of 1.5, 6.0 and 10 µM were obtained for streptomycin, novobiocin and neomycin, respectively. These catalytic surfaces can be renewed (by polishing), with a surface-to-surface reproducibility of 6.5% for the detection of 5 x 10^-5 M streptomycin. The analytical application of RuO2-modified carbon paste electrodes to the analysis of these antibiotics by flow injection was investigated, with a view to liquid chromatographic separation with electrochemical detection applications.
Streptomycin Novobiocin Neomycin B Electrode Electrode Electrode

"Continuous-flow Chemiluminescence Determination Of Some Corticosteroids"
Analyst 1990 Volume 115, Issue 12 Pages 1553-1557
Ioanna I. Koukli and Antony C. Calokerinos

Abstract: Powdered tablets (200 mg), injection solution (2 ml) or creams (1 g) were dissolved in and diluted with 0.1 M H2SO4 for dexamethasone (I) and hydrocortisone (II) or 0.1 M H2SO4 containing 1% acetone for prednisolone (III), methylprednisolone (IV), dexamethasone (V) or betamethasone (VI). Portions of solution were analyzed in an air-segmented continuous-flow manifold by mixing the sample stream (2 mL min-1) with 0.5 mM ammonium Ce(IV) sulfate in 0.1 M H2SO4 and with aqueous 0.01 M Na2SO3 (both at 0.8 mL min-1) and the resulting chemiluminescence was measured. Calibration graphs were rectilinear from 0.1 to 1 µg mL-1 of I, II, III and IV, and from 0.5 to 5 µg mL-1 of V and VI with detection limits of 0.02 to 0.3 µg mL-1. The coefficient of variation were 1.3 to 4.9% and 1.6 to 6.2% for I and II, respectively. There was no interference from excipients. The sampling rate was 40 h-1. Results agreed well with those of an official method.
Corticosteroids Pharmaceutical Chemiluminescence

"Flow Injection Manifolds With Membrane Filters For Preconcentration And Interference Removal By Precipitation In Flow Injection Flame Atomic Absorption Spectrometry"
Analyst 1990 Volume 115, Issue 12 Pages 1543-1547
Ebenezer Debrah, Christina E. Adeeyinwo, Stephen R. Bysouth and Julian F. Tyson

Abstract: The use of disposable, non-metallic membrane filters in two manifolds was evaluated for the collection of gelatinous or crystalline ppt. formed in a flow injection system with subsequent dissolution for analysis by flame AAS. As an example, Cu was pre-concentrated by precipitation with NaOH by using a valve configuration that allowed mixing of sample and reagent during a load cycle followed by a subsequent injection cycle to dissolve the ppt. through the filter; the detection limit was 0.01 ng L-1 and a pre-concentration. factor of 12 was obtained. A method is also described for the determination of Ca in the presence of Al (1 g l-1) by selective precipitation of Ca with ammonium oxalate followed by dissolution in 0.5 M HCl without the use of valves. The detection limit was 0.25 µg L-1 of calcium. Aluminum did not interfere.
Calcium Copper Spectrophotometry

"Flow Injection Determination Of Thiamine Based On Its Oxidation To Thiochrome By Mercury(II)"
Analyst 1990 Volume 115, Issue 2 Pages 217-220
Carmen Martinez-Lozano, Tom&aacute;s P&eacute;rez-Ruiz, Virginia Tom&aacute;s and Concepci&oacute;n Abell&aacute;n

Abstract: A 175 µL sample was mixed with 5 mM Hg(II) solution at pH 4 before combining with 0.2 M phosphate buffer (pH 12.5), each flowing at 0.87 mL min-1, in a thermostatted PTFE reaction coil (300 cm x 0.5 mm). Thiochrome fluorescence was measured at 465 nm (excitation at 370 nm). Calibration graphs were rectilinear from 0.2 to 7 µM. The detection limit was 34 nM, and the coefficient of variation for 4.5 µM was 0.2% (n = 11). Sample throughput was 22 samples h-1. The method was successfully applied to multivitamin preparations.
Thiamine Fluorescence

"Automated Spectrophotometric Determination Of Titanium(IV) In Water And Brines By Flow Injection Based On Its Reaction With Hydrogen Peroxide"
Analyst 1990 Volume 115, Issue 3 Pages 315-318
M. Mu&ntilde;oz, J. Alonso, J. Bartrol&iacute; and M. Valiente

Abstract: A flow injection system is described (with diagram). Water (13 µL) in H2SO4 was injected into a 0.7 M H2SO4 carrier stream (2.2 mL min-1) and diluted in a coil (50 cm x 0.7 mm) with water (2.2 mL min-1). The stream was then mixed in a coil (1 m x 0.7 mm) with 3% (w/v) H2O2 in 0.7 M H2SO4 (2.2 mL min-1) and the absorbance was measured at 410 nm. Calibration graphs of Ti in the sample were rectilinear up to 1000 ppm at a sampling rate of 240 hmin1. Detection limit was 9 ppm, and the coefficient of variation was 0.6%. Interference from Fe, V and Mo can be avoided by selective precipitation during sample pre-treatment. A system is also described for the determination of low Ti concentration. in brine using 3.3 M Mg(NO3)2 - 1 M HCl as carrier; the calibration graph was rectilinear up to 30 ppm, coefficient of variation were 0.7% and the detection limit was 0.3 ppm.
Titanium(IV) Water Environmental Spectrophotometry

"Gel-phase Absorptiometry Of Phosphate With Molybdate And Malachite Green And Its Application To Flow Analysis"
Analyst 1990 Volume 115, Issue 6 Pages 843-848
Kazuhisa Yoshimura, Sawako Nawata and Genichiro Kura

Abstract: Phosphate in water was determined by formation of an ion-association complex with ammonium molybdate - C. I. Basic Green 4, then either, (i) adsorption onto Sephadex LH-20 beads which were then packed into a 5-mm cell for absorbance measurement at 627 and 750 nm vs. air; the difference between the absorbance at the two wavelengths was proportional to the PO43- concentration, or (ii) concentration online onto the gel in a flow-through cell for measurement of the absorbance at 627 nm. For procedure (i) calibration graphs were rectilinear for up 10 µg L-1 of PO43-; the detection limit was 0.6 µg l-1. For procedure (ii) calibration graphs are plotted for up to 3 µg l-1; the rectilinear range varied with sample volume. Recoveries were 98 to 105%; detection limit (flow injection procedure) was 75 ng l-1. The method was applied to softened-, rain-, ground-, river and seawater.
Phosphate River Ground Sea Rain Spectrophotometry

"Bismuth(III) Hydride Generation, Its Separation And The Determination Of Bimuth(III) By Atomic Absorption Spectrometry Using Flow Injection"
Analyst 1990 Volume 115, Issue 5 Pages 567-569
Wing-Fat Chan and Ping-Kay Hon

Abstract: Sample (200 µL) containing Bi(III) was injected into a water stream (4.3 mL min-1) and mixed with NaBH4 solution in a reaction coil. From the gas - liquid separator comprising a PTFE membrane backed by a stainless-steel screen (10 mm x 60 mm, 200 mesh), the BiH3 diffused into a N stream (280 mL min-1) to be carried into the absorption cell. The detection limit was 0.17 ng with a rectilinear response up to 50 ppb of Bi, and a sample rate of 300 h-1 was achieved. The method was applied satisfactorily to standard gun-metal. Interference from Cu and other metals can be avoided by using the standard addition method.
Bismuth(3+) Spectrophotometry

"Determination Of Orthophosphate In Waters And Soils Using A Flow Analyser"
Analyst 1990 Volume 115, Issue 1 Pages 65-67
David J. Malcolme-Lawes and Koon Hung Wong

Abstract: Samples (0.3 ml) were injected into a high performance continuous-flow analyzer. (carrier 1.5% of NaCl in 0.12 M HNO3) downstream of the manifold where the reagents NH4MoO4, K - Sb tartrate (catalyst) and L-ascorbic acid were pre-mixed. Absorbance of the heteropolymolybdenum blue complex was measured at 670 nm. Interferences from ions commonly found in potable waters were small. The calibration graph was rectilinear for 100 ppm, and the detection limit was 4.8 ppb of P. Sample throughput was >120 h-1 at 4 ppm. The method was applied to soil samples after extraction with NaHCO3 solution
Phosphate Water Environmental Spectrophotometry Sample preparation

"Determination Of Oxonium Ion In Strongly Ionisable Inorganic Acids And Determination Of Substituted Acetic Acids Using Flow Injection And Chemiluminescence Detection"
Analyst 1990 Volume 115, Issue 1 Pages 69-72
Issam M. A. Shakir and Azad T. Faizullah

Abstract: Samples (60 µL) of 200 mM of H2SO4, HCl, HClO4, HNO3 or H3PO4 were injected first into a water carrier stream (2 mL min-1) before combining with a BrO3- - Br- stream and entering the reaction coil with 100 mM H2O2 and 0.5 mM luminol in Na2CO3 solution The H3O+ concentration. was determined indirectly from the chemiluminescence peak intensity. The log. - log. calibration graphs were rectilinear. The method was applicable to chloroacetic and trichloro- and trifluori-acetic acids. Detection limits ranged from 4 mM for formic acid to 20 mM for H3PO4 and chloroacetic acid. The coefficient of variation were 1% (n = 4) and sample throughput was 90 h-1.
Oxonium Chloroacetic acid Trichloroacetic acid Trifluoroacetic acid Formic acid Chemiluminescence

"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

"Improvement Of Accuracy For The Determination Of Transient Signals Using The Kalman Filter. 1. Simulations"
Analyst 1992 Volume 117, Issue 12 Pages 1925-1928
Ian D. Brindle and Shaoguang Zheng

Abstract: Results of computer simulations are presented to show that the Kalman filter is very efficient for removing white noise in transient signals from one-component systems. Even at a signal to noise ratio of 1:1 the simulated response was recovered with negligible error. The method does not involve initial guesses of variance and estimated value and works best when several hundred data points are available for processing. It should improve detection limits in e.g. flow injection systems and batch hydride generators for analysis of hydride-forming elements and Hg.
Spectrophotometry

"Potentiometric Differential Microdetector With Interchange Solid Membranes Used In Flow Injection Analysis"
Analyst 1997 Volume 122, Issue 2 Pages 107-109
Liliana Olenic, Elena Hop&icirc;rtean and Liviu Olenic

Abstract: A flow-through potentiometric detector for use in FIA is described. The detector consists of two identical tubular solid-state ion-selective membranes fabricated from pressed pellets. One membrane is the working electrode while the other is a reference electrode. FIA measurements are based on measuring the potential difference between the two electrodes on passing the sample through the working electrode. The approach is illustrated by the potentiometric determination of Ag(I) and sulfide with a detector based on Ag2S membranes and by the determination of Cu(II) with a detector based on CuS/Ag2S membranes. The lower concentration limits of the linear response ranges for each analyte are given. The sample throughput was 40-60 samples/h. RSD were n = 5).
Copper Silver Potentiometry Electrode Electrode Electrode

"Spectrofluorimetric Determination Of Vitamin K3 By A Solid-phase Zinc Reactor Immobilized In A Flow Injection Assembly"
Analyst 1997 Volume 122, Issue 2 Pages 139-142
I. Gil Torr&oacute;, J. V. Garc&iacute;a Mateo and J. Mart&iacute;nez Calatayud

Abstract: The spectrofluorimetric determination of vitamin K3 (menadione) using a flow injection (FI) assembly provided with a solid-phase reactor with immobilized zinc is described. The naphthohydroquinone was produced by means of two coupled steps in the FI system: hydrolysis of the sodium sulfite derivative of the menadione in a basic medium and reduction of the generated menadione in the zinc reactor in an acidic medium. The fluorescent product was monitored spectrofluorimetrically (lambda ex 325 nm; lambda em 425 nm). The calibration graph was linear over the range 0.1-18 µg mL-1 with a reproducibility of 1.6%; the limit of detection was 0.005 µg mL-1 and the sample throughput was 70 h-1. The influence of foreign compounds was studied and the procedure was applied to the determination of vitamin K3 in three different pharmaceutical formulations. A stream of menadione sodium hydrogensulfite in aqueous 90% acetonitrile at a flow rate of 3.5 mL/min was merged with a stream of 35 mM NaOH at a flow rate of 0.3 mL/min. The merged stream was then passed through a 330 cm mixing coil before being merged with a stream of 0.08 M HCl in aqueous 40% acetonitrile at a flow rate of 0.3 ml/min. After passing through a 10 cm mixing coil, 850 µL of the resultant solution was injected into a carrier stream of aqueous 90% acetonitrile at a flow rate of 3 mL/min. The mixture was applied to a column (35 cm x 1.5 mm i.d.) of Zn particles then through a 25 cm mixing coil. Fluorescence was measured at 425 nm (excitation at 325 nm). A diagram of the manifold used is given. The calibration graph was linear from 0.1-18 µg/ml vitamin K3 (determined as menadione sodium hydrogensulfite); the detection limit was 0.005 µg/ml and RSD was 1.6% (n = 32). The throughput was 70 samples/h. The method was applied to the analysis of pharmaceuticals.
Vitamin K3 Pharmaceutical Fluorescence

"Optosensor For Cinchona Alkaloids With C18 Silica Gel As A Substrate"
Analyst 1997 Volume 122, Issue 3 Pages 283-285
Zhilong Gong, Zhujun Zhang and Xiaofeng Yang

Abstract: A sample was mixed with 5 mL 0.5 M H2SO4 then diluted to 25 mL with water. A portion (2 ml) was injected into a carrier stream of 0.1 M H2SO4 at a flow rate of 1 ml/min and passed through a flow cell packed with C18 silica gel. The fluorescence intensity of the alkaloid(s) retained on the silica gel was measured at 430 nm (excitation at 346 nm) for quinine (I) and quinidine (II) and at 436 nm (excitation at 363 nm) for cinchonine (III) and cinchonidine (IV). The calibration graphs were linear from 5-20 000 ng/ml I and II and from 200-20 000 ng/ml III and IV. The detection limits were 2.3 ng/ml for I and II and 31.6 ng/ml for III and IV. RSD were 0.9% at the 20 ng/ml level of I and II, and 1.1% at the 4 µg/ml level of III and IV (n = 7). Sample throughput was 10 samples/h. The method was successfully applied to the determination of I in pharmaceuticals and soft drinks. A flow-through optosensor for cinchona alkaloids with C18 silica gel as a substrate is proposed. The sensor is developed in conjunction with a flow injection analysis system and is based on the retention of the cinchona alkaloids on a C18 column and the enhancement of their fluorescence. The analytical performance characteristics of the proposed sensor for the detection and quantification of these alkaloids were as follows: the detection limits of quinine, cinchonine, quinidine and cinchonidine were 2.3, 31.6, 2.3 and 31.6 ng mL-1, respectively, with relative standard deviations of 0.9% for quinine and quinidine (20 ng mL-1, n = 7) and 1.1% for cinchonine and cinchonidine (4.0 µg mL-1, n =7), respectively. Most of the common species did not interfere. The recommended method has been successfully tested for determination of quinine in pharmaceutical preparations and soft drinks.
Alkaloids Quinine Cinchonine Quinidine Cinchonidine Soft drink Pharmaceutical Fluorescence Sensor

"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

"Flow Injection Spectrophotometric Determination Of L-dopa And Carbidopa In Pharmaceutical Formulations Using A Crude Extract Of Sweet Potato Root As Enzymatic Source"
Analyst 1997 Volume 122, Issue 4 Pages 345-350
Orlando Fatibello-Filho and Iolanda da Cruz Vieira

Abstract: Sweet potato root (25 g) was extracted with 100 mL 0.1 M phosphate buffer of pH 7 (buffer A) containing 2.5 g Polyclar SB-100. The crude extract was used as a source of polyphenol oxidase (PPO) directly in the carrier solution in the cited determination. Twenty tablets were powdered and mixed; a portion was dissolved in buffer A then filtered and the filtrate was diluted. A portion (500 µL) was injected into a carrier stream of 120 iu PPO in buffer A at a flow rate of 10.01 ml/min. The mixture was then passed through a 400 cm coiled reactor maintained at 25°C. Absorbance was measured at 370 and 500 nm for carbidopa (I) and L-dopa (II), respectively. The calibration graphs were linear from 0.4-10 mM I and II. The detection limits were 0.2 and 0.15 µM for I and II, respectively. RSD was n = 6). Recoveries were 99-106% I and II. The throughput was 26 samples/h. A flow injection (FI) spectrophotometric method is proposed for the determination of L-dopa and carbidopa in pharmaceutical formulations. After selection of the extraction medium (e.g., buffer-to-tissue ratio, pH, buffer concentration, protective agents and/or stabilizers) and storage conditions, crude extract of sweet potato root [Ipomoea batatas (L.) Lam.] was used as an enzymatic source of polyphenol oxidase (Tyrosinase; catechol oxidase; EC.1.14.18.1) directly in the carrier. This enzyme catalyses the oxidation of these catecholamines to the corresponding dopaquinone. Further, dopaquinone undergoes a rapid spontaneous auto-oxidation to leucodopachrome, which is in turn oxidized to dopachrome; this last compound has a strong absorption at 480 and 360 nm for L-dopa and carbidopa, respectively. For the optimum extraction conditions found the enzyme activity of the crude extract did not vary for at least five months when stored at 4°C and decreased by only 4-5% during an 8 h working period at 25°C. The results obtained for L-dopa and carbidopa by the proposed enzymatic FI method were in close agreement with the label values (r1 = 0.9699 and r2 = 0.9999) and also with those obtained using a pharmacopeial method (r3 = 0.9675). The throughput was 26 samples h-1, and 2.30 mL of crude extract were consumed in each determination, corresponding to only 72 mg of the original sweet potato root. The detection limit (three times the signal blank/slope) was 1.5 x 10^-5 and 2.0 x 10^-5 mol L-1 for L-dopa and carbidopa, respectively; the recovery of L-dopa and carbidopa from three samples ranged from 98.6 to 106.3% of the added amount.
l-Dopa Carbidopa Pharmaceutical Spectrophotometry

"Fully Automatic Online Separation Preconcentration System For Electrothermal Atomic Absorption Spectrometry: Determination Of Cadmium And Lead In Seawater"
Analyst 1997 Volume 122, Issue 7 Pages 679-684
Facundo M. Fern&aacute;ndez, Jorge D. Stripeikis, Mabel B. Tudino and Osvaldo E. Troccoli

Abstract: A fully automated system for analyte separation and pre-concentration prior to ET AAS determination is described. Preconcentration is performed on a chelating resin microcolumn (Chelex-100) placed in the injection tip of the graphite furnace autosampler. A time-based computer-controlled flow injection manifold is used for column conditioning, pre-concentration and washing steps. Elution is performed in a single step by the programmable graphite furnace autosampler; both complete and partial injection of the eluate into the graphite furnace for ET AAS analysis are possible. Diagrams of the manifold used, illustrating the sequence of operations involved, are given. The system was used to determine Cd and Pb in seawater. Detection limits of 0.9 and 8 ng/l were obtained for Cd and Pb, respectively. The RSD (n = 10 or 15) were 2.7-4%.
Cadmium Lead Sea Sample preparation Spectrophotometry

"Determination Of Trimethylamine In Fish By Pervaporation And Photometric Detection"
Analyst 1997 Volume 122, Issue 7 Pages 663-666
J. A. Garc&iacute;a-Garrido and M. D. Luque de Castro

Abstract: Two methods for trimethylamine determination in fish are described. In the first method (method A), the sample was extracted with TCA. The filtered extract was mixed with streams of formaldehyde and NaOH in a continuous-flow manifold before reaching a pervaporation cell kept at 60°C. The analyte evaporated and diffused through a PTFE membrane into a Bromothymol Blue solution of pH 6 and the color change was recorded. In the second method (method B), the sample was mixed with TCA, formaldehyde and NaOH directly in the pervaporation cell. After 5 min at 60°C, the analyte was collected in a Bromothymol Blue solution of pH 6 and the color change was recorded. The calibration graphs were linear for 2-30 mg/l and for 0.1-10 mg/g trimethylamine for methods A and B, respectively; the corresponding detection limits were 1.6 mg/l and 0.08 mg/g. The RSD (n = 11) were 3.5-4.3%. The throughputs were 8 and 2 samples/h for methods A and B, respectively.
Trimethylamine Marine Spectrophotometry

"Miniaturized Graphite Sensors Doped With Metal-bathophenanthroline Complexes For The Selective Potentiometric Determination Of Uric Acid In Biological Fluids"
Analyst 1997 Volume 122, Issue 8 Pages 815-819
Saad S. M. Hassan and Nashwa M. H. Rizk

Abstract: Miniaturized poly(vinyl chloride) matrix membrane sensors in an all- solid-state graphite support, responsive to urate anion, were developed. The membranes incorporate lipophilic ion-pair complexes of urate anion with ruthenium(III), iron(II), nickel(II) and copper(I) bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) counter cations. The sensors demonstrate a near-Nernstian response to urate over the concentration range 1 x 10^-2-1 x 10^-5 mol L-1 and have micromolar detection limits and good selectivity properties. The response is virtually unaffected by pH changes in the range 7-10 and the response times are 5-10 s in aqueous solutions and in human serum and urine samples. A flow injection detector incorporating an iron(II) bathophenanthroline-urate graphite sensor was used for continuous monitoring of uric acid. The minimum detectable concentration was approximately 8 µg mL-1 and the sample throughput was approximately 120 h-1. Direct potentiometric determination of uric acid in the static and hydrodynamic modes of operation over the range 15 µg mL-1-1.5 mg mL-1 showed average recoveries of 98.7 and 97.8% with RSDs of 0.6 and 0.7%, respectively. Application of the method to the determination of uric acid in human serum and urine gave results that compared favourably with those obtained by the standard spectrophotometric method.
Uric acid Blood Serum Urine Potentiometry Electrode Electrode Electrode Sample preparation Sensor

"Determination Of Iodide In Brines By Membrane Permeation Flow Injection Analysis"
Analyst 1997 Volume 122, Issue 11 Pages 1235-1237
J. T. H&aring;kedal and P. K. Egeberg

Abstract: A flow injection method is described for the determination of iodide based on the oxidation of iodide to iodine, which after permeation through a PTFE membrane is detected spectrophotometrically. The sample is injected into a carrier stream of water and merged with acidic dichromate reagent, oxidising iodide to iodine. The iodine permeates through the membrane into a collector stream containing iodide, The iodine reacts with iodide forming triiodide, and is measured spectrophotometrically in a flow cell at 350 nm, The repeatability of the technique was better than a relative standard deviation of 2% at 5 mg L-1 level, with a throughput of 50 samples hr-1, The detection limit was 0.2 mg L-1 iodide, The method is suitable for analyzing high saline waters, No significant matrix effect is found for seawater up to 32 parts per thousand S, or sodium chloride concentrations up to 50 g L-1, The method is tested for potential interfering substances (Br-, COOH, CH3COOH, HCO3-, Fe2+, Mn2+ and S2-), The only interfering compound found was sulfide, which can be removed by preheating the samples after acidification. The method was tested by analyzing marine pore water samples from Ocean Drilling Program Leg 164; the results compared well with data obtained by the manual method. 17 References
Iodide Sea Spectrophotometry

"Study Of The Possible Benefits Of Flow Injection Sample Introduction For Flame Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 2 Pages 191-194
Julian F. Tyson, Christina E. Adeeyinwo and Stephen R. Bysouth

Abstract: A brief review is presented, with 30 references, of flow injection techniques used in conjunction with atomic spectrometry. The possible benefits of flow injection sample introduction at reduced flow rates to reduce interference and improve detection limits were studied. Conclusions are that such sample introduction does not result in any fundamental differences in signals compared with conventional nebulization, in that different operating parameters are still required for different figures of merit. The best approach for optimum detection limits in flow injection sample introduction is to maximize the peak height and minimize noise. By generation of a volatile metal chelate in a flow injection manifold for subsequent determination and with appropriate solvent extraction and heated tubing, it is possible to increase considerably the atomization efficiency over conventional nebulization. A brief review is presented, with 30 references, of flow injection techniques used in conjunction with atomic spectrometry. The possible benefits of flow injection sample introduction at reduced flow rates to reduce interference and improve detection limits were studied. Conclusions are that such sample introduction does not result in any fundamental differences in signals compared with conventional nebulization, in that different operating parameters are still required for different figures of merit. The best approach for optimum detection limits in flow injection sample introduction is to maximize the peak height and minimize noise. By generation of a volatile metal chelate in a flow injection manifold for subsequent determination and with appropriate solvent extraction and heated tubing, it is possible to increase considerably the atomization efficiency over conventional nebulization.
Spectrophotometry

"Determination Of Arsenic In A Nickel-based Alloy Using A Microwave Digestion Procedure And A Continuous-flow Hydride-generation Atomic Absorption System Incorporating Online Matrix Removal"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 2 Pages 181-184
Philip G. Riby, Stephen J. Haswell and Roman Grzeskowiak

Abstract: Sample (1 g) was dissolved in HNO3 - HF in a microwave digestion unit over 1 h, and the resulting solution was passed through a Bond Elut strong cation-exchange column to remove Ni. The resulting solution was then mixed in a flow injection system with 1% NaBH4 solution in aqueous 1% NaOH followed by 4 M HCl, and the generated AsH3 was stripped by Ar in a gas - liquid separator and determined at 193.7 nm. The cation-exchange resin could be regenerated by washing with 1 M HCl. Recovery of 25 ppm of As added to low-As Ni-based alloy was 98%. The limit of detection in the final solution was 1.3 ppb of As, the calibration graph was rectilinear up to 20 ppb, and the coefficient of variation (n = 10) for 10 ppb was 3%.
Arsenic Alloy Ion exchange Sample preparation Spectrophotometry

"Evaluation Of Three Low-volume Interfaces For Organic Solvent Introduction To The Inductively Coupled Plasma - Applications To Flow Injection"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 4 Pages 341-345
Timothy J. Brotherton, Peter E. Pfannerstill, John T. Creed, Douglas T. Heitkemper, Joseph A. Caruso and Sotiris E. Pratsinis

Abstract: Three low-volume sample delivery systems (described and illustrated) were evaluated for continuous solution nebulization and for flow injection introduction into the ICP: (i) a cooled mini-spray chamber, (ii) a desolvation interface, and (iii) a partial-suction injector. Each system was operated under the same conditions (tabulated). The max. solution delivery rates for each interface were >2 mL min-1 for both methanol and acetonitrile. Calibration graphs were rectilinear over three to four orders of magnitude in each instance. Detection limits under continuous solution nebulization conditions were in the mid- to sub ng mL-1 range. Flow injection peak widths were narrower for (i), (ii) and (iii) than for systems involving spray chambers with larger volume.
Spectrophotometry

"Flow Injection Inductively Coupled Plasma Mass Spectrometry For The Determination Of Platinum In Airborne Particulate Matter"
J. Anal. At. Spectrom. 1990 Volume 5, Issue 1 Pages 75-80
Hitoshi Mukai, Yoshinari Ambe and Masatoshi Morita

Abstract: Standard solution of Pt in 0.6 M HCl and samples of particulate airborne matter (prep. described) were introduced into a flow injection system (described) incorporating a cation-exchange column (16 cm x 8 mm) of Dowex 50W-X8 (50 to 80 mesh) which was pre-washed with 3 M HCl and stabilized with 0.6 M HCl. This system was used online for trapping major matrix elements, which cause suppression of the Pt signal at m/e = 195, and Hf (which interferes spectrally) from 0.6 M HCl medium. The eluate from the column was introduced into the ICP-MS for the determination of Pt. The calibration graph was rectilinear up to 40 µg L-1 of Pt, and the coefficient of variation (n = 5) for 2 µg L-1 of Pt was ~5%. The detection limit was ~0.1 µg L-1 of Pt in solution or 5 ng g-1 in airborne particulate matter. The method was applied to the determination of Pt in samples such as vehicle exhaust particulates and roadside dust.
Platinum Exhaust Particulates Road Mass spectrometry Ion exchange

"Online Aluminum Preconcentration And Its Application To The Determination Of The Metal In Dialysis Concentrates By Atomic-spectrometric Methods"
J. Anal. At. Spectrom. 1990 Volume 5, Issue 1 Pages 15-19
M. R. Pereiro Garc&iacute;a, A. L&oacute;pez Garc&iacute;a, M. E. D&iacute;az Garc&iacute;a and A. Sanz-Medel

Abstract: The use was studied of the cation and anion exchangers Dowex 50W-X2 and Amberlite IRA-400, and of Chelex 100 and a synthetic chelating resin (Kelex 100 adsorbed on Amberlite XAD-7) for the pre-concentration. of Al with elution with various concentration. of NaOH, KOH, HCl and HNO3. The materials were packed in a mini-column inserted in a flow injection pre-concentration. manifold and Al was determined by AAS or ICP-AES. The pre-concentration. conditions were optimized and detection limits of 15 and 3 µg mL-1 were obtained with AAS and AES detection, respectively. Chelex 100 and Amberlite IRA-4 were most suitable for determination of Al in dialysis concentrates, but the latter cannot be used if the acetate concentration. is >40 mg mL-1.
Aluminum Spectrophotometry Spectrophotometry

"Design And Optimization Of A Flow Injection Hydride Generator And Its Use For Automated Standard Additions"
J. Anal. At. Spectrom. 1990 Volume 5, Issue 8 Pages 675-679
raham D. Marshall and Jacobus F. van Staden

Abstract: The flow injection hydride generator is described and depicted schematically. The sample is injected into an acidic carrier stream which is subsequently merged with the reductant. The apparatus allows rapid analysis, ease of automation and simple inline handling of interferences. To determine, e.g., As, the sample was injected into a stream of 4.8 M HCl (1.8 mL min-1) and mixed with a stream of aqueous NaOH (10 g l-1) containing 1.0% of NaBH4 in a reaction tube (50 cm x 1.5 mm). An Ar stream (35 mL min-1) was used to strip the AsH3 from the solution in a separator with a cotton gauze membrane and the As was determined by AAS at 193.7 nm. Calibration graphs were rectilinear for 40 ng to 0.5 µg mL-1 of As with coefficient of variation 2.9% (n = 10); the detection limit was 8 ng mL-1 of As. The detection limits of Bi, Sb, Se and Te were 2, 10, 6 and 3 ng mL-1, respectively, while those of Ge, Pb and Sn were similar to flame AAS values.
Arsenic Germanium Lead Tin Spectrophotometry

"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

"Flow Injection Online Sorbent Extraction Preconcentration For Graphite Furnace Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1990 Volume 5, Issue 7 Pages 639-646
Zhaolun Fang, Michael Sperling and Bernhard Welz

Abstract: A micro-flow injection online sorbent extraction pre-concentration system was developed to improve the performance of flame and graphite-furnace AAS. Lead was determined as a test element. A Perkin-Elmer Model 2100 spectrometer was used at 283.3 nm. A 26-fold enhancement in peak area compared with 50 µL direct introduction was obtained with pre-concentration. for 60 s while achieving a coefficient of variation of 1.9% (n = 11) for 0.1 µg L-1 of Pb and a detection limit of 3 ng l-1. Determination of Pb in seawater revealed that the interfering matrix had been almost completely removed during pre-concentration. Results obtained for some National Research Council of Canada Standard Reference Materials agreed well with certified values.
Lead Sea 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

"Detection Limits Versus Matrix Effects: Analysis Of Solutions With High Amounts Of Dissolved Solids By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 6 Pages 927-931
Peter Richner

Abstract: The ICP-MS determination of trace impurities in high-purity nickel with use of flow injection or conventional solution nebulization was compared. The ability to analyze solution with high dissolved-solid content in flow injection mode in a carrier solution of 1% sample injections (0.2 ml) allowed 3 to 40-fold improvements in detection limits to achieve ppb levels; detection limits for 16 elements were tabulated and limits were defined mainly by blank values in the reagents and containers used.
Metal Mass spectrometry Spectrophotometry

"Development Of A Proposed International Standard For Determining Arsenic In Workplace Air Using Hydride Generation Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1994 Volume 9, Issue 3 Pages 273-280
Robert D. Foster and Alan M. Howe

Abstract: Air was sampled on a cellulose ester membrane filter and paper back-up pad previously conditioned with 1 M Na2CO3 in aqueous 5% glycerol. The exposed filters were treated at 175°C with 5 mL of concentrated HNO3 and 1 mL of concentrated H2SO4, the volume was reduced to 1 ml, 2 mL of H2O2 was added after cooling, and the mixture was heated until SO3 evolution ceased. The residue was dissolved in 10 mL of water, and 5 mL aliquots were treated with 12.5 mL of concentrated HCl and 2.5 mL of 10% KI solution and then with a stream (5 ml/min) of 0.2-2% NaBH4 solution in 0.1 M NaOH. As was determined at 197.2 or 193.7 nm (calibration graphs linear for 0-50 and 0-25 ng/ml of As, respectively) in both flow injection (FI) and continuous-flow (CF) systems. For 4.8-96 µg of As added on-filter, recoveries were >98.8% for both systems. For 10^-40 ng/ml of As, RSD of 1 and 3% were obtained for the CF and FI systems, respectively, at 197.2 nm. The limits of detection and determination were 0.3 and 1 ng/ml at 197.2 nm. Preliminary results from an inter-laboratory study are discussed.
Arsenic Environmental Spectrophotometry

"Analysis Of Geological Materials For Bismuth, Antimony, Selenium And Tellurium By Continuous-flow Hydride-generation Inductively Coupled Plasma Mass Spectrometry. 2. Methodology And Results"
J. Anal. At. Spectrom. 1997 Volume 12, Issue 1 Pages 103-106
GWENDY E. M. HALL and JEAN-CLAUDE PELCHAT

Abstract: The apparatus and procedure for removal of mutual interference were as described in Part 1 (Ibid., 1997, 12, 97). Sample digestion with aqua regia gave complete recovery of Bi, but some matrices required digestion with HF/HClO4/HNO3/HCl to obtain full recoveries of Te, Se and Sb. The analytes were separated from some potentially interfering elements (e.g., Co, Cu and Ni) by coprecipitation on lanthanum hydroxide. Results are presented for 18 of the Chinese GSD and GSR stream sediment and rock standard reference materials. RSD were in the range 3-8% and the detection limits were 1 µg/kg for Bi and Te and 6 µg/kg for Sb and Se.
Antimony Bismuth Selenium Tellurium Geological Environmental Sample preparation Mass spectrometry

"Determination Of Cadmium By Flow Injection Isotope-dilution Inductively Coupled Plasma Mass Spectrometry With Vapor-generation Sample Introduction"
J. Anal. At. Spectrom. 1997 Volume 12, Issue 5 Pages 579-584
TARN-JIUN HWANG and SHIUH-JEN JIANG

Abstract: The sample (0.1 ml) is injected into a carrier stream of 2% thiourea/0.0002% Co solution in 0.1 M HCl (4.8 ml/min), which then merges with a stream of 4% NaBH4 solution in 0.1 M NaOH (2.4 ml/min) for passage to a gas-liquid separator that consists essentially of a vessel (diagram presented), containing 120 glass beads (5 mm diameter), from which the Cd-containing vapor is carried to the ICP by a stream of Ar. Interference from MoO+ and ZrO+ is thereby alleviated. Sample-preparation procedures are described for sediments, urine and water, in which 111Cd is added as the tracer; the result is calculated by use of the equation proposed previously (Ibid., 1996, 11, 353). The detection limit is 26 pg/ml of Cd. Recoveries of 5 ng/ml of Cd added to standard refence waters were quantitative, and the results for standard reference freeze-dried urine and marine sediments agreed well with the certified values.
Cadmium Urine Marine Environmental Mass spectrometry Mass spectrometry

"Effect Of Sample Volume On The Limit Of Detection In Flow Injection Hydride Generation Electrothermal Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 1 Pages 17-21
Julian F. Tyson, Robert I. Ellis, Susan A. Mcintosh and Christopher P. Hanna

Abstract: The anal. performance of methods for the determination of hydride-forming elements has been improved recently by the development of procedures in which the hydride is trapped on the interior surface of a graphite furnace atomizer. The signal for a given concentration. increases with an increase in sample volume, and it is often implied that a decrease in the limit of detection may also be achieved by increasing the sample volume To evaluate this claim, a simple equation was derived which predicts the relationship between detection limit and sample volume when all the contributions to the blank are proportional to sample volume A time-based approach to the variation of sample volume was developed to ensure that the analyte introduced from reagent contamination was, in fact, proportional to sample volume Detection limits were measured for a series of sample volumes between 156 and 1560 µL. As the sample volume was increased, the detection limit improved significantly from 0.3 to around 0.05 µg/L up to a volume of about 500 µL. Between 500 and 1000 µL, a further improvement, to around 0.02 µg/L, was obtained, but for volumes larger than 1000 µL no further significant improvement was obtained. Good agreement between the predicted and experimental determined variations in detection limit with sample volume was obtained, and, thus, the underlying inverse proportionality of the relationship between detection limit and sample volume was confirmed. This rectangular hyperbolic relationship has practical consequences for the extent to which detection limits can be improved by increasing the sample volume, even when the blank is very low or zero.
Arsenic Spectrophotometry

"Hazards Of A Naive Approach To Detection Limits With Transient Signals"
Anal. Chem. 1988 Volume 60, Issue 7 Pages 725-727
T. W. Williams and Eric D. Salin

Abstract: Detection limits were calculated for transient signals (as generated in flow injection, chromatographic and atomic spectrometric methods) taking into consideration the time window in which a peak would be expected to appear. Procedures used for computerized smoothing of noisy signals are outlined. It is shown that a 99.9% confidence limit would not be correctly obtained by a simple standard deviation calculation, and that the window size and degree of smoothing affect the calculated detection limit.

"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

"Automated Segmented-flow Electrochemical Analyser"
Anal. Chem. 1989 Volume 61, Issue 18 Pages 2102-2108
Palitha Jayaweera and Louis Ramaley

Abstract: An automated system combining segmented-flow analysis with pulse-voltammetric detection is described. Using a static-Hg-drop electrode in the reductive mode, multi-component determinations could be carried out at 100 samples h-1. The instrument can be programmed to perform square-wave voltammetry, staircase voltammetry and pulse voltammetry, all with scan reversal capability. Features include a simple flow system, complete computer control, an inline deoxygenator, stopped-flow analysis and signal averaging for reduced noise. Excellent rectilinearity, sensitivity and reproducibility were obtained; for metals such as Cd(II) and Pb(II) the detection limits were 6 and 8 ppb, respectively.
Metals Cadmium Lead Voltammetry Electrode

"Electrocatalysis And Detection Of Amino-sugars, Alditols And Acidic Sugars At A Copper-containing Chemically Modified Electrode"
Anal. Chem. 1989 Volume 61, Issue 20 Pages 2258-2263
Sunil V. Prabhu and Richard P. Baldwin

Abstract: The use of the electrode described previously (Anal. Abstr., 1990, 52, 4J112) for the oxidative detection of simple sugars has been extended. Cyclic voltammetric scans for the compounds showed a broad oxidation in the region of +0.4 to +0.6 V vs. Ag - AgCl. When used in flow injection analysis and LC, detection limits were in the pmol to nmol range. With flow injection the coefficient of variation (n = 60) for 10 µM-gluconic acid was 4.9% and in the analysis of a tobacco leaf extract by LC, the standard deviation, e.g., for 3.7% of glucose was 0.2%.
Gluconic acid Leaves Electrode Voltammetry

"Amperometric Detection Of Non-electroactive Cations In Flow Systems At A Cupric Hexacyanoferrate Electrode"
Anal. Chem. 1989 Volume 61, Issue 23 Pages 2594-2598
Karsten N. Thomsen and Richard P. Baldwin

Abstract: A vitreous carbon electrode coated with an electro-deposited film of Cu3[Fe(CN)6]2 was evaluated as a sensor for non-electroactive cations in flow injection analysis and ion chromatography. The activity of the electrode in the flow system was similar to that seen for static solution in that reduction of the film was selectively enhanced by K+ and NH4+. Consequently, these ions could be detected indirectly as cathode peaks. HPLC detection limits of 0.5 µM, corresponding to 10 pmol injected, were obtained for both ions at an applied potential of +0.45 V vs. Ag - AgCl. Coating the electrode with a supporting overlayer of Nafion improved the stability and reproducibility; coefficient of variation were 1 to 5% over several hours.
Potassium Ammonium Electrode HPIC Amperometry

"Copper Determination In Urine By Flow Injection Analysis With Electrochemical Detection At Platinum Disk Microelectrodes Of Various Radii"
Anal. Chem. 1990 Volume 62, Issue 1 Pages 27-31
Darryl L. Luscombe, Alan M. Bond, David E. Davey, and John W. Bixler

Abstract: The incorporation of platinum disk microelectrodes of various radii (2.5-50 microns) in a well-jet flow cell offers reduced limits of detection for the determination of copper in urine by flow injection analysis compared with standard methods based on a conventional sized glassy carbon disk macroelectrode (radius 1.5 mm), in a thin-layer cell. The radius of the platinum disk microelectrode was found to be critical with respect to both the limit of detection and flow rate dependence. An optimal radius value of 28 microns was found with detection limits increasing with both larger and smaller electrode radii. In contrast, as theoretically expected, a diminished flow rate dependence was observed the smaller the radii of the platinum disk microelectrodes. Sample cleanup and preparation is conveniently achieved by the use of Sep-Pak cartridges and formation of a copper dithiocarbamate complex. The metal complex is easily oxidized at platinum disk microelectrodes in acetonitrile, which was the solvent used in the flow injection method of analysis.
Copper Urine Electrode Electrochemical analysis

"In Vivo Microdialysis And Thermospray Tandem Mass Spectrometry Of The Dopamine Uptake Blocker 1-[2-[bis(4-fluorophenyl)m Ethoxy]ethyl]-4-(3-phenylpropyl)-piper Azine (GBR-12909)"
Anal. Chem. 1990 Volume 62, Issue 6 Pages 597-601
Stanley D. Menacherry and Joseph B. Justice

Abstract: Microdialysis in conjunction with thermospray tandem mass spectrometry was employed in following the time course of the experimental drug GBR-12909 in vivo. GBR-12909 is 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-3(phenylpropyl)- piperazine. An important feature of microdialysis exploited in the method is the elimination of sample cleanup procedures. The detection limit was determined to be 100 pg and the relative standard deviation of estimates for standard solution in the range of 50 nmol/L to 1 µmol/L concentrations was found to be 17%. Important factors in obtaining high sensitivity and reproducibility were carrier phase composition and operation in the flow injection mode. The maximum concentration of GBR-12909 in the brain for a dose of 100 mg/kg i.p. was determined to be 250 nmol/L with the maximal concentration occurring approximately 2 h postinjection. This represents a 40-fold lower concentration of GBR-12909 in the brain as compared to cocaine concentration obtained at a dose of 30 mg/kg, which was estimated earlier under similar experimental conditions. This observation could explain the discrepancy between relative in vivo and in vitro potencies of the two drugs.
Mass spectrometry

"Flow Injection Analysis Of L-lactate With Enzyme Amplification And Amperometric Detection"
Anal. Chem. 1990 Volume 62, Issue 7 Pages 708-712
Moore U. Asouzu, William K. Nonidez, and Mat H. Ho

Abstract: A flow injection analysis method for the determination of the lactate anion with enzyme amplification and amperometric detection is described. The system utilizes an oxygen electrode for measurement of changes in the oxygen concentration in the flow stream. Two enzymes, lactate oxidase and lactate dehydrogenase, were randomly coimmobilized on aminopropyl controlled-pore glass (AMP-CPG) and packed into a reactor. β-NADH was used as a coenzyme for the regeneration of lactate from pyruvate. The experimental conditions for the determination of the lactate anion were studied for this system by the simplex and the univariant methods. The results obtained under these two conditions were compared. The simplex experimental condition yielded a calibration curve whose linear portion had a slope that was 1.2 times greater than that of the linear portion of the curve obtained under univariant conditions. The limit of detection under simplex condition was 1.19 x 10^-7 M vs 3.29 x 10^-7 M lactate under univariant conditions. The relative standard deviation obtained for this system at 6 x 10^-6 M lactate (n = 10) was about 2.5% under simplex conditions and 3.6% under univariant maximization conditions.
l-Lactate Amperometry Electrode

"Surface-enhanced Raman Spectroscopy At A Silver Electrode As A Detection System In Flowing Streams"
Anal. Chem. 1990 Volume 62, Issue 7 Pages 678-680
Neil J. Pothier and R. Ken Force

Abstract: A three-electrode surface-enhanced Raman spectroscopy detector, with a Ag working electrode, Pt foil auxiliary electrode and SCE reference and a cell volume of 30 µL, was evaluated for use with HPLC and flow injection analysis. In a flowing system, the analyte is rapidly removed from the electrode surface in 10 s, and spectra was obtained in 5 s with an optical multichannel analyzer.. Under stopped-flow conditions, detection limits were 175, 233 and 211 pmol for adenine, thymine and cytosine, respectively.
Adenine Thymine Cytosine Raman Electrode HPLC

"Fiber-optic Glucose Sensor With Electrochemical Generation Of Indicator Reagent"
Anal. Chem. 1990 Volume 62, Issue 7 Pages 755-759
Hari Gunasingham, Chin Huat Tan, and Jimmy K. L. Seow

Abstract: The prep. is described of a reversible enzyme-based optical-fiber sensor, involving the electrochemical regeneration of the optically active redox mediator tetrathiafulvalene as the indicator. The performance of the sensor as a thin-layer cell configuration was evaluated in flow injection and steady-state analyzes giving a rectilinear calibration graph for ~12 and 3 mM, respectively, and a detection limit of 0.2 mM glucose. Potential interfering species such as O and organic species had no significant effect on detector response. The response was compared with an amperometric detector.
Glucose Amperometry Sensor

"Highly Stable Phospholipid - Cholesterol Electrode Coatings For Amperometric Monitoring Of Hydrophobic Substances In Flowing Streams"
Anal. Chem. 1990 Volume 62, Issue 8 Pages 826-829
Joseph Wang and Ziling Lu

Abstract: Vitreous-carbon rotating disc electrodes were coated with a solution of phosphatidylcholine and cholesterol in CHCl3 and dried. The electrode provided improved stability compared with that of single-domain phospholipid layers without affecting the selectivity. The response, e.g., for promethazine was rectilinear from 20 to 140 µM with a limit of detection of 1.4 µM. The coefficient of variation (n = 24) for an injection (10 µL) of a 0.25 mM solution was 3%.
Amperometry Electrode

"Composite Electrodes Based On Carbonized Polyacrylonitrile Foams"
Anal. Chem. 1990 Volume 62, Issue 10 Pages 1102-1104
Joseph Wang, Albert Brennsteiner, and Alan P. Sylwester

Abstract: Carbon-foam composites (prep. described) were machined into discs (3 mm diameter), which were polished and epoxied into the end of a glass tube. Electrical contact was made to the inner surface with carbon paste and copper wire, and the surface was polished until highly smooth, clean and shiny. The electrodes were characterized by linear scan and chronoamperometric experiments at stationary electrodes under quiescent conditions, and applied in amperometric monitoring of dopamine in flow injection analysis. The detection limit was 60 nM-dopamine and the coefficient of variation (n = 10) for peak current was 3.6%.
Dopamine Amperometry Electrode

"Multiple Sensor Response In Segmented-flow Analysis With Ion-selective Electrodes"
Anal. Chem. 1990 Volume 62, Issue 10 Pages 1015-1019
D. Brynn Hibbert, Peter W. Alexander, Sri Rachmawati, and Sylvia A. Caruana

Abstract: Improved sensitivity in potentiometic analysis is achieved with multiple cells in a continuous-flow system. A study was made of the use of air segments in the flowing stream, to isolate electrically each flow cell. The sensing and reference electodes used were Ag - AgCl. An expression for the total cell potential is given. The sensitivity of a three-cell sensor system for detection of Cl- ions gave up to 3 times the single Nernstian slope. The detection limit in the sub-Nernstian region of the cell response was 0.7 µM, a 10-fold improvement over the single cell system, and peak height measurements showed a coefficient of variation of 1.5% for determination of 20 µM-Cl-.
Potentiometry Sensor

"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

"Catalytic Oxidation And Flow Detection Of Carbohydrates At Ruthenium Dioxide-modified Electrodes"
Anal. Chem. 1990 Volume 62, Issue 14 Pages 1413-1416
Joseph Wang and Ziad Taha

Abstract: A RuO2-modified carbon paste electrode (prep. described) was used in the constant-potential cyclic voltammetric flow detection of carbohydrates. Samples in 1 M NaOH were analyzed at the electrode (+0.4 V; 20 mV s-1) with Ag - AgCl and Pt-wire reference and auxillary electrodes, respectively. The effects of variables, viz, pH, flow rate, operating potential and surface 'loading', were studied. The method was applied in the detection of deoxyribose, fructose, galactose, gluconic acid, glucose, glycerol, lactose, maltose, ribose and sucrose (electrode responses are tabulated). Working ranges were from 0.1 to 10 mM glucose and 0.1 to 1 mM ribose, fructose and galactose. The detection limits were pmol-levels and the coefficient of variation (n = 72) was 1.2%. The electrode was stable for >48 h with a signal loss of 10% over this period.
Carbohydrates Deoxyribose Fructose Galactose Glucose Gluconic acid Glycerol Lactose Maltose Ribose Sucrose Electrode Electrode Voltammetry

"Characterization Of Formaldehyde And Formaldehyde-releasing Preservatives By Combined Reversed-phase Cation-exchange High Performance Liquid Chromatography With Post-column Derivatization Using Nash's Reagent"
Anal. Chem. 1990 Volume 62, Issue 14 Pages 1397-1402
William Russell Summers

Abstract: Preservative solution (50%) was injected on to a polymeric reversed-phase column (15 cm x 4.6 mm) of PRP-1 (5 µm), with gradient elution with water, acetonitrile and diaminopropionic monohydrochloride solution (details given), the eluate was derivatized with Nash reagent (2 M ammonium acetate - 0.02 M penta-2,4-dione - 0.03% acetic acid) and the absorbance and fluorescence of derivatives was measured at 410 and 510 nm, respectively. The method is labour-saving and permits the simultaneous analysis of preservatives and formaldehyde. The detection limit was ~400 ppb with rectilinear dynamic ranges of two orders of magnitude. The coefficient of variation was ~0.5%.
Formaldehyde Preservatives HPLC Ion exchange Spectrophotometry Fluorescence

"Selective Determination Of Histamine By Flow Injection Analysis"
Anal. Chem. 1990 Volume 62, Issue 18 Pages 1971-1976
James M. Hungerford, Kevin D. Walker, Marleen M. Wekell, Jack E. LaRose, and Harold R. Throm

Abstract: A flow injection analysis (FIA) method for the determination of histamine is described. Control of reaction timing allows exploitation of a transient, chemical-kinetic increase in selectivity that occurs when o-phthalaldehyde reacts with histamine. The molar fluorescence ratio (selectivity) of histamine/histidine reaches a maximum value of 800 in 32 s, precluding the need for separation of histamine from histidine, spermidine, and other potential interferences in biological samples. Online dilution prevents matrix effects and affords a linear response up to approximately 4.45 mM histamine, or 500 mg of histamine free base/100 g. Under these conditions the detection limit (3 times peak-to-peak baseline noise) is 5.5 pg (corresponding to 0.60 mg of histamine free base/100 g of sample) and throughput is 60 injections per hour. The high sensitivity and high selectivity of the method allow the rapid determination of histamine in fish with minimal sample conditioning and will find application in the determination of endogenous histamine as well, such as in blood plasma and brain tissue.
Histamine Blood Plasma Brain Marine Fluorescence

"Solute Focusing In Flow Injection Analysis: Limits Of Detection And Linear Dynamic Range"
Anal. Chem. 1990 Volume 62, Issue 14 Pages 1392-1397
Beverly F. Johnson and John G. Dorsey

Abstract: On-line solute focusing traditionally utilizes a two-injection valve system In which the analyte is injected and concentrated on a suitable column and is subsequently eluted by the injection of a concentrated plug of a suitable elution solvent. Here a single injection valve solute focusing system was investigated. The solutes were injected In a chromatographically weaker solvent than the carrier stream in order to retain the solute at the head of the column until the carrier stream causes it to elute. This process causes a reduction in the solute bandwidth or "solute focusing". The use of a bonded- phase silica column as a solute focusing device for hydrophobic solutes improves the analysis over traditional flow injection analysis (FIA) in several ways. Solute focusing gives comparable or improved concentration limits of detection (LODs) relative to conventional FIA and gives absolute LODs independent of injection volume. A linear relationship is observed when one standard solution is injected in increasing volumes with the solute focusing method. This allows the use of only one standard solution for the construction of a calibration plot. Finally, when an on-line reaction is employed, no peak splitting at large injection volumes is observed with the solute focusing method.

"Online Preconcentration And Volatilization Of Iodine For Inductively Coupled Plasma Atomic-emission Spectrometry"
Anal. Chem. 1991 Volume 63, Issue 21 Pages 2539-2542
Scott P. Dolan, Scott A. Sinex, Stephen G. Capar, Akbar Montaser, and Robert H. Clifford

Abstract: The limit of detection for iodine in ICP-AES is 154 µg mL-1, too high to be of use in food analysis. Conversion of I- (and IO3-) to I2 before nebulization increased the transport efficiency and hence the sensitivity. Oxidation to I2 was achieved online by mixing the acidified test solution with H2O2. The signal at 183.04 nm was enhanced by a factor of 33 for an Ar ICP and of 100 for a He ICP, with sensitivities of 5 and 9 ng mL-1, respectively. In the flow injection mode, I- and IO3- were adsorbed on a membrane disc containing AG1-X8 anion-exchange resin. The membrane was washed and the anions were eluted with 4 M HNO3, with simultaneous oxidation to I2. The detection limit for I- was thereby improved to 0.75 ng mL-1. A further improvement by a factor of 8 is required to match the sensitivity of the current spectrophotometric method.
Iodine Food Spectrophotometry

"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

"Photoelectrochemical Sensor For Catalase Activity Based On The In Situ Generation And Detection Of Substrate"
Anal. Chem. 1993 Volume 65, Issue 2 Pages 169-175
Claudia B. Cohen and Stephen G. Weber

Abstract: A device for the in situ generation and detection of hydrogen peroxide is presented for application to the automation of enzyme immunoassay and application to biosensors. The device is fabricated from a gold-coated optical fiber. It photochemically generates and electrochemically detects H-2O-2 in aqueous, buffered solutions. The electrochemical signal is attenuated in the presence of the enzyme catalase (EC 1.11.1.6), for which H-2O-2 is a substrate. The quantum efficiency of the peroxide-producing reaction (0.20%), the collection efficiency of the gold ring electrode ((3.8 +- 0.05) times 10^-3), and the sensitivity of the photocurrent to catalase have been evaluated. The sensor's photosignal is reduced by 50% in the presence of 25 nM catalase. Detection limits of 76 pM catalase have been obtained using FIA.
Enzyme, catalase Immunoassay Sensor

"Selective And Rapid Ion-chromatographic Determinations Of Alkaline-earth Metals And Applications To The Analysis Of Barite"
Fresenius J. Anal. Chem. 1989 Volume 335, Issue 7 Pages 687-691
Daren Yan, Jingan Zhang and Georg Schwedt

Abstract: Alkaline-earth metals, Pb and Cd were separated on a column (20 cm x 4 mm) of Nucleosil SA (10 µm) with 20 mM oxalic acid - 10 mM citric acid - 2 or 3 mM ethylenediamine, adjusted to pH 3.4, as mobile phase (1 mL min-1). A solution containing 1 mM 4-(2-pyridylazo)resorcinol, 0.5 mM ZnEDTA and 2 M NH3 (pH 11) was used for post-column derivatization (flow rate 0.33 mL min-1), with absorbance measurement at 495 nm and quantitation based on peak areas. Complete separation of the above metals, Cu, Zn, Fe and Mn required a mobile phase (0.9 mL min-1) of 2 mM oxalic acid - 3 mM ethylenediamine - 0.02% of NaCl (pH 2.8). To determine alkaline-earth metals in barite, 0.1 g of sample was fused with 5 g of Na2CO3 - K2CO3 (4:1) at 700°C for 30 min, the cooled melt was leached with hot water, and the ppt. was filtered off and dissolved in HCl. The resulting solution was diluted and filtered before analysis of a 0.1 mL portion (pH ~1.5). Detection limits ranged from 25 to 100 µg L-1 and recoveries were quantitative. At mg L-1 levels, coefficient of variation ranged from 0.7 to 1.6%.
Metals, alkaline earth Barite HPIC Spectrophotometry

"Application Of Flow Injection Potentiometry To The Determination Of Chloride In Various Matrices"
Fresenius J. Anal. Chem. 1989 Volume 335, Issue 8 Pages 931-937
Wolfgang Frenzel

Abstract: Chloride-selective electrodes were prepared from silver tubes (1 cm x 0.3 to 1.0 mm i.d.); the inner wall was coated with AgCl. Behaviour under steady-state and flow injection conditions was studied and the influence of system parameters on sensitivity, detection limit, response time and sample throughput was discussed. Sample throughput was 60 to 200 h-1. The calibration graph was rectilinear from 0.1 to 10,000 mg L-1 of Cl-, with a detection limit of 0.01 mg L-1 and a coefficient of variation of 1%. The method was applied in the analysis of tap and mineral water, emission control of HCl and the determination of Cl- in silicon nitride.
Chloride Water Mineral Gas Inorganic compound Electrode Electrode Potentiometry

"Direct Determination Of Calcium, Magnesium, Sodium And Potassium In Water By Flow Injection Flame Atomic Spectroscopy, Using A Dilution Chamber"
Fresenius J. Anal. Chem. 1989 Volume 335, Issue 8 Pages 975-979
M. de la Guardia, V. Carbonell, A. Morales and A. Salvador

Abstract: The cited elements were determined in water using a dilution chamber to extend the calibration range and allow a single concentration. standard to be used for the calibration of each analyte. A double channel injector and the merging zone technique were used to add La solution to the samples (1:1) and reduce reagent consumption. Samples were analyzed by flow injection flame AAS, peak heights were measured at 422.67, 285.21, 589.00 and 766.49 nm for Ca, Mg, Na and K, respectively. Results agreed well with those obtained by a batch AAS procedure and gave better precision. Sensitivities were 0.0408, 0.046, 0.0122 and 0.20 ppm and detection limits were 2.5, 1.5, 7.0 and 0.5 ppm for Ca, Mg, Na and K, respectively. The sample throughput was ~180 samples h-1. The cited elements were determined in water using a dilution chamber to extend the calibration range and allow a single concentration. standard to be used for the calibration of each analyte. A double channel injector and the merging zone technique were used to add La solution to the samples (1:1) and reduce reagent consumption. Samples were analyzed by flow injection flame AAS, peak heights were measured at 422.67, 285.21, 589.00 and 766.49 nm for Ca, Mg, Na and K, respectively. Results agreed well with those obtained by a batch AAS procedure and gave better precision. Sensitivities were 0.0408, 0.046, 0.0122 and 0.20 ppm and detection limits were 2.5, 1.5, 7.0 and 0.5 ppm for Ca, Mg, Na and K, respectively. The sample throughput was ~180 samples h-1.
Calcium Magnesium Sodium Potassium Environmental Spectrophotometry

"Flow Injection Determination Of Boron, Copper, Molybdenum, Tungsten, And Zinc In Organic Matrices With Direct-current Plasma Optical-emission Spectrometry"
Fresenius J. Anal. Chem. 1989 Volume 335, Issue 8 Pages 893-899
M. C. Brennan and G. Svehla

Abstract: The sample was dissolved in a suitable solvent, and the solution was diluted with isobutyl methyl ketone and introduced via a 600 µL loop into a stream of anhydrous acetic acid (4.5 mL min-1) and then to the nebulizer of the spectrometer via a 25-cm silicon rubber tube (0.8 mm i.d.). The line intensities were measured at 249.773, 324.754, 379.825, 400.875 and 202.548 nm for B, Cu, Mo, W and Zn, respectively. Calibration graphs were rectilinear up to 500 ng mL-1 of B, Cu, Mo and Zn and up to 1000 ng mL-1 of W with detection limits of 21, 14, 28, 120 and 20 ng mL-1 for B, Cu, Mo, W and Zn, respectively. The throughput was 100 samples h-1. The continuous introduction of the carrier liquid into the plasma cleaned out the nebulizer and reduced memory effects.
Boron Copper Molybdenum Tungsten Zinc Spectrophotometry

"Miniature Hydride-generator System For Inductively Coupled Plasma Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 5 Pages 423-424
Katsuhiko Yokoi, Mieko Kimura and Yoshinori Itokawa

Abstract: In the cited continuous-flow hydride-generator system (described and illustrated), sample solution is mixed with trichloroacetic acid solution and NaBH4 solution in NaOH and passed through a gas - liquid separator (diagram given). The generated hydrides were passed into the ICP by Ar carrier gas (1 l min-1). A Shimadzu ICPS-1000 II sequential plasma spectrometer was used to determine Sn and Ge at 189.989 and 209.423 nm, respectively. The detection limits were 30 and 150 pg mL-1 for Sn and Ge, respectively; ~100-fold better than those of conventional pneumatic nebulizer ICP-AES.
Tin Germanium Spectrophotometry

"Online Preconcentration Of Silver On Activated Alumina And Determination In Borehole Water By Flow Injection Atomic Absorption Spectrophotometry"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 3 Pages 201-204
P. P. Coetzee, I. Taljaard and H. de Beer

Abstract: Silver in borehole water is pre-concentrated on a polyethylene micro-column (3 cm x 1 mm) of activated alumina (basic form) connected to a flame AAS instrument (schematic diagram given). Sample (pH 4.0) is passed through the column for 3 to 6 min at 5 mL min-1 with water as carrier stream, elution is with 0.5 mL of 2 M HNO3 and regeneration is with 0.15 M NH4OH (2 min at 5 mL min-1). The effluent is directed to a nebulizer and analyzed by AAS at 328.1 nm. The calibration graph is rectilinear for up to 100 µg mL-1 of Ag, with coefficient of variation (n = 10) of ±5 and 18% for >10 and 5 µg l-1, respectively. The detection limit is 4 µg l-1. Sodium, Mg and Ca salts at 0.1 M to 0.5 M decrease the Ag signal by 10%.
Silver Borehole Spectrophotometry Sample preparation

"Speciation Of Tetraalkyllead Compounds By Flow Injection - Atomic Absorption Spectrophotometry"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 1 Pages 9-15
R. Borja, M. de la Guardia, A. Salvador, J. L. Burguera and M. Burguera

Abstract: To determine total Pb in liposoluble samples (e.g., gasoline), containing tetraethylstannane (I) and tetramethylstannane (II), samples (100 µL) were injected into a carrier stream (2.4 mL min-1) of aqueous 0.1% Emulsogen M in one channel of a double-channel manifold and were demetallated by a 200 µL injection of 6% iodine solution in light petroleum into the other channel. The two channels converged before demetallation in a reaction coil of length 300 cm and emulsification in a 2.8 mL PTFE stirred dilution chamber. Lead was determined in an air - acetylene flame. The two compounds were determined individually by single injection (i.e., without the iodine) into the flow system followed by emulsification; the carrier flow rate was 16.6 mL min-1 and a coil of length 25 cm was used. The theory is presented. The detection limits for total Pb, for I as Pb and for II as Pb were 43, 0.8 and 0.6 µg g-1, respectively.
Lead Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Calcium In Rain And Snow With Chlorophosphonazo III"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 6 Pages 707-709
Michio Zenki, Kikuko Ohmuro and Kyoji T&ocirc;ei

Abstract: A two-fold manifold (diagram given) is used for the determination of Ca in rain and snow based on the complex formation with chlorphosphonazo III in the presence of 0.01 M oxalate (pH 2.8). Barium, Sr and rare-earth metals interfered. Under optimum conditions, the calibration curve was rectilinear up to 1.2 ppm Ca and the detection limit was 0.01 ppm for 120 µL of sample. The coefficient of variation for 0.4 and 1.0 ppm Ca were 0.354 and 0.352%, respectively. Results agreed well with those obtained by AAS.
Calcium Rain Snow Spectrophotometry

"Improvement Of Detection Limits In Flow Injection Analysis"
Fresenius J. Anal. Chem. 1991 Volume 341, Issue 11 Pages 647-649
Hanswilly M&uuml;ller, Birgit Frey and Wolfgang B&ouml;hme

Abstract: The use of flow cells with longer pathlengths in a conventional UV - visible spectrometer with a large sample compartment as a detector for flow injection analysis was studied with emphasis on the determination of phosphate with use of the molybdenum blue method. For determinations using 1-cm flow cells, calibration graphs were rectilinear for 0.1 to 1 mg L-1 of phosphate; with use of a 5-cm flow cell, the calibration graph was rectilinear for 0.005 to 1 mg mL-1. The use of the long path flow caused band broadening but this could be compensated for by slight modifications to the manifold.
Phosphate Spectrophotometry

"Semi-automatic Determination Of Tin In Marine Materials By Continuous-flow Hydride-generation Inductively Coupled Plasma Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 822-826
Yong-Lai Feng, H. Narasaki, Hong-Yuan Chen, Li-Ching Tian

Abstract: Sample (1.25 g) was equilibrated overnight with 15 mL 68% HNO3 and 2 mL 70% HClO4, then digested by heating with 0.5 mL concentrated H2SO4. The resulting solution was adjusted to pH 3.5 with 4 M NaOH and passed through a DIAION SA 10A anion-exchange resin column (15 cm x 8 mm i.d.; Mitsubishi Kasei Corp., Tokyo, Japan). The eluate was mixed with 3.5 mL 3 M H2SO4 and 2.5 mL 10% L-cysteine hydrochloride monohydrate, diluted to 25 mL and then analyzed for Sn by continuous-flow hydride-generation ICP-AES at 189.93 nm (operating conditions given). The detection limit was 0.4 ng/mL Sn and the RSD (n = 10) was 0.5%. The effects of varying the H2SO4, NaBH4 (hydride-generating reagent) and NaOH concentrations, Ar (carrier gas) and NaBH4 flow rates and the ratio of flow rates of sample solution and NaBH4 were investigated (results presented). The effects of interferents were also investigated, along with seven methods for masking interference (results tabulated). The method was applied to an environmental (marine) CRM. The result agreed with the certified value and the RSD (n = 6) was 0.95%.
Tin Environmental Marine Ion exchange Sample preparation Spectrophotometry

"Sensitive Spectrophotometric Determination Of Ascorbic-acid In Fruit Juices And Pharmaceutical Formulations Using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (br-padap)"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1174-1178
S&eacute;rgio L. C. Ferreira, Marcus L. S. F. Bandeira, Valfredo A. Lemos, Hilda C. dos Santos, A. C. Spinola Costa, Djane S. de Jesus

Abstract: A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP). The iron((II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 x 10(5) l mol-1 cm-1 and 5.69 x 10(4) l mol-1 cm-1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 µg mL-1, a calibration sensitivity of 0.744 mL µg-1 at 560 nm and 0.323 mL µg-1 at 748 nm, and a detection limit of 15 ng mL-1 and 44 ng mL-1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations. The results demonstrated a good precision (RSD < 1%) and are in agreement with those obtained with others methods. The Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system. 65 References
Ascorbic acid Fruit Pharmaceutical Spectrophotometry

"Cyclodextrin-based Optosensor For The Determination Of Quinine"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1093-1096
Zhilong Gong and Z. Zhang

Abstract: β-Cyclodextrin (β-CD) was immobilized on to silica gel (100-200 mesh) using a standard method; 20 µL was loaded into one end of a flow-cell (25 µL) and the other end was kept free. The cell was then connected into the flow system of a simple optosensing FIA manifold (diagram given). Samples of standards (2 ml) were injected via a valve and pumped through the flow system; quinine was complexed with the β-CD. The carrier solution used throughout was 0.1 M H2SO4 at a flow rate of 2 ml/min. The fluorescence of the complex on the β-CD immobilized gel was measured at 451 nm (excitation at 350 nm). Calibration graphs were linear from 3 x 10^-9 to 2 x 10^-5 M quinine. The detection limit was 0.2 ng/ml quinine; RSD was 2.1% (n = 7) for 0.05 µg/ml quinine. The method was successfully applied to the analysis of some pharmaceuticals (results tabulated); recoveries were 97-104%.
Quinine Pharmaceutical Fluorescence Sensor

"An Optosensor For Tryptophan With C18 Silica Gel As A Substrate"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1097-1100
Zhilong Gong and Z. Zhang

Abstract: C18 silica gel (15 µL) was loaded into one end of a Perkin-Elmer flow cell L225 1247 (10 x 1.8 mm i.d.) and the other end was kept free. The cell was then connected into the flow system of a simple optosensing FIA manifold (diagram given). Samples or standards (2 ml) were injected into the flow system at a flow rate of 1 ml/min. The carrier solution was 0.1 M NaH2PO4/0.1 M NaOH of pH 8. tryptophan passed into the flow cell where it was retained on the gel. Fluorescence was measured using a Perkin-Elmer LS-SO instrument with excitation and emission slits set at 5 and 15 nm, respectively. Calibration graphs were linear from 0.1-50 µg/ml tryptophan; detection limit was 25 ng/ml. RSD was 2.9% (n = 7) for 10 µg/ml tryptophan. Most common species did not interfere. The method was successfully applied to the analysis of a pharmaceutical preparation containing 18 amino-acids; composition results compared favourably with those reported by the manufacturer.
Tryptophan Pharmaceutical Fluorescence Sensor

"Flow Injection Determination Of Silver With Spectrophotometric Detection"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 4 Pages 475-479
A. A. Ensafi and K. Zarei

Abstract: Sample (170 µL) was injected into a stream (8 ml/h) of water which merged with streams (8 ml/h) of 0.8 M peroxodisulfate in 32 mM H2SO4 and of 18 mM 1,10-phenanthroline/0.42 mM gallocyanine and passed through a reaction coil (220 cm x 0.5 mm i.d.) before the absorbance was measured at 540 nm. The optimal temperature was 40°C. Tolerance limits for interfering ions are tabulated. Tolerance to bromide, chloride, iodide and thiosulfate was increased 1000-fold by digestion of sample with concentrated HNO3. The detection limit was 0.001 µg Ag and the analytical range was 0.002-0.7 µg. The RSD (n = 10) at 0.035 and 0.17 µg were 2.8% and 0.9%, respectively. The method was applied to river water after digestion with HNO3/H2SO4 and to panchromatic plates (photographic materials) after treatment with NaOH and digestion of the gelatinous film with HNO3. Results agreed with those obtained by AAS. Calibration graphs were linear.
Silver Plate River Sample preparation 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

"Potassium Permanganate-octylphenyl Polyglycol Ether Chemiluminescence System For FIA Determination Of Hydrogen Peroxide"
Microchim. Acta 1997 Volume 126, Issue 1-2 Pages 73-76
Manliang Feng, Zheng Li, Jiuru Lu and Hailong Jiang

Abstract: A mixture solution of aqueous H2O2/octylphenyl polyglycol ether was injected into a flow (2 ml/min) of mixed H2SO4/KMnO4 solution, which then passed through a flow cell for chemiluminescence detection (wavelength not given). The calibration graph was linear from 0.01-60 µM-H2O2, the detection limit was 6 nM and the RSD (n = 7) for 40 nM- to 4 mM H2O2 solutions were 1.6-2.3%. The sampling rate was 60/h. The tolerance of the method to interferents was investigated. The maximum tolerable amounts of interferents are listed. The method was also applied to rain. Results were comparable to those obtained by a fluorescence method (cf. Cheng, 'Fluorescence Analysis', Science Press, China, 1990, p 427) and RSD were 2.3-2.9%. Details of the optimization of the method (i.e. concentrations, flow rate and choice of reagents) are given.
Hydrogen peroxide Rain Chemiluminescence

"Spectrophotometric Determination Of Aniline By Flow Injection Analysis In A Non-aqueous Medium"
Microchem. J. 1989 Volume 39, Issue 1 Pages 20-24
Berman, R.J.;Clark, G.D.;Whitman, D.A.;Christian, G.D.

Abstract: Samples (25 µL) were injected into a carrier stream (2.5 mL min-1) of 0.1 M chloranil in dioxan - propan-2-ol (1:1), and the mixture passed through a PTFE reaction coil (3 m x 0.8 mm) before absorbance measurement at 543 nm. The calibration graph was rectilinear for up to 25 mM aniline; the detection limit was 0.23 mM. Sixty samples can be analyzed in 1 h. The reaction is not specific. Samples (25 µL) were injected into a carrier stream (2.5 mL min-1) of 0.1 M chloranil in dioxan - propan-2-ol (1:1), and the mixture passed through a PTFE reaction coil (3 m x 0.8 mm) before absorbance measurement at 543 nm. The calibration graph was rectilinear for up to 25 mM aniline; the detection limit was 0.23 mM. Sixty samples can be analyzed in 1 h. The reaction is not specific.
Aniline Spectrophotometry

"Indirect Determination Of Iodine In Seawater And Brine By Atmospheric-pressure Helium Microwave Induced Plasma Atomic Emission-spectrometry Using Continuous-flow Cold Vapor Generation Of Mercury"
Microchem. J. 1990 Volume 41, Issue 2 Pages 148-155
Taketoshi Nakahara* and Tamotsu Wasa

Abstract: The method was based on the decrease of the Hg emission intensity in highly acidic solution due to the formation of Hg(II) - iodide complexes. The reductant, 0.02% SnCl2 in 0.1 M HCl and Hg(II) in 4 M HNO3 (10 ng mL-1) were added to the sample solution containing I- and the decrease in the Hg signal at 253.652 nm was measured. In the analysis of seawater and brine, IO3- was reduced to I- with 0.001% ascorbic acid. The response was rectilinear from 2 to 100 ng mL-1; limit of detection was 0.74 ng mL-1. The coefficient of variation (n = 100) for 50 ng mL-1 was 1.05%. Mean recoveries were >93%.
Iodine Sea Environmental Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Hydrazine"
Microchem. J. 1997 Volume 56, Issue 3 Pages 269-275
Ali A. Ensafi and B. Naderi

Abstract: A three-line FIA manifold was used. The method was based on the decolorization of thionine by reaction with nitrite and its subsequent inhibition when trace amounts of hydrazine are present due to the reaction of hydrazine with nitrite in acidic media. A mixture of 0.1N-H2SO4 and 0.16 mM thionine solution, 4 µg/ml nitrite solution, and water were pumped at 0.5 ml/min. Sample (170 µL) containing 2-40 µg/ml of hydrazine was injected into the water carrier and the absorbance of thionine was measured at 602 nm. The method was optimized. The calibration graph was linear from 2-40 µg/ml of hydrazine with a detection limit of 1 µg/ml. The RSD (n = 10) was 3.3% for 7 µg/ml of hydrazine. The method was more selective than other kinetic and FIA methods and was applicable to river and drinking water; results are tabulated.
Hydrazine Water River Spectrophotometry

"Determination Of Acetylcholine And Choline By Flow Injection With Immobilized Enzymes And Fluorimetric Or Luminometric Detection"
Anal. Biochem. 1989 Volume 176, Issue 2 Pages 221-227
Jan R&iacute;cn&yacute;, Jil&iacute; Coupek and Stanislav Tucek

Abstract: Acetylcholine and choline were determined in solution and tissue extracts by a continuous-flow system with a sequence of enzyme reactors containing immobilized acetylcholinesterase, choline oxidase and peroxidase. Additional reactors with immobilized choline oxidase and catalase were used to remove choline and choline-generated H2O2 from samples when acetylcholine was being determined. Acetylcholinesterase, choline oxidase and catalase were immobilized on Separon HEMA E and peroxidase was immobilized on Separon HEMA (for fluorimetric detection) or on a coiled glass capillary or on controlled-pore glass beads (for luminometric detection). Detection was by measuring fluorescence generated from the reaction of H2O2 with 3-(4-hydroxyphenyl)propionic acid in presence of peroxidase, or measuring luminescence generated from the reaction of H2O2 with luminol in presence of peroxidase. Calibration graphs were rectilinear up to 100 pmol of acetylcholine with fluorescence detection. Detection limits were 10 or 25 pmol of acetylcholine with the coiled-capillary peroxidase or controlled-pore-glass peroxidase columns, respectively, with luminometric detection, and 0.2 pmol with fluorimetric detection.
Acetylcholine Choline Biological tissue Luminescence Fluorescence

"Continuous-flow Automated Assay For Iodimetric Estimation Of Hydroperoxides"
Anal. Biochem. 1989 Volume 176, Issue 2 Pages 353-359
Sian M. Thomas*, Wendy Jessup, Janusz M. Gebicki

Abstract: Lipid hydroperoxides in aqueous samples or heptane extracts of biological materials were determined by an automated continuous-flow iodimetric method. The reagent was 1% KI in methanol - acetic acid (2:1) (made 1 mM with respect to desferal, used to inactivate contaminating Fe) and the wash solution was 2% acetic acid. The formation of tri-iodide ions was measured at 360 nm. All operations were protected from light. The detection limit was 60 pmol of hydroperoxide; coefficient of variation were 3, 3.6 and 2.5% (n = 10) for serum, aqueous lipid and heptane extracts of biological material, respectively. Results correlated well with those by the manual iodimetric assay (r = 0.999).
Hydroperoxides, lipid Blood Serum Spectrophotometry

"Determination Of Thiobarbituric Acid-reactive Substances In Oxidized Lipids By High Performance Liquid Chromatography With A Post-column Reaction System"
Anal. Biochem. 1989 Volume 182, Issue 1 Pages 116-120
Kazuaki Yoden* and Toshihiro Iio

Abstract: Free malonaldehyde (I) and other thiobarbituric acid-reactive substances were determined in oxidized lipids (prep. described) by HPLC on a column (15 cm x 6 mm) of Inertsil ODS-2 (5 µm) with linear gradient elution (0.7 mL min-1) from aqueous 50 to 100% methanol over 30 min, and held at 100% methanol for 15 min. The eluate was mixed (0.7 mL min-1) with 0.5% 2-thiobarbituric acid in 0.05 M HCl in a reaction coil (20 m x 0.4 mm) at 55°C and the resulting red pigment was determined fluorimetrically at 553 nm (excitation at 515 nm). The calibration graph was rectilinear up to 4 nM-I and the detection limit was 0.5 nM. The procedure was applied in the analysis of thermally oxidized methyl linoleate, the degradation products of methyl linoleate hydroperoxides and the oxidation products of rat liver microsomes.
Thiobarbituric acid Liver HPLC Fluorescence

"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 Methylguanidine In Plasma And Urine By High Performance Liquid Chromatography With Fluorescence Detection Following Post-column Derivatization"
Anal. Biochem. 1990 Volume 184, Issue 2 Pages 213-218
Venkata K. Boppana*, Gerald R. Rhodes* and David P. Brooks

Abstract: Plasma (1 ml) was mixed with 0.2 µg of ethylguanidine as internal standard, adjusted to pH 11 with 26 µL of 1 M NaOH and applied to a 1 mL weak-cation-exchange extraction column, which was washed with water before elution with methanolic 1% trifluoroacetic acid. After evaporation under N, the residue was dissolved in 0.2 mL of the mobile phase [0.06 M chloroacetate buffer (pH 4.0) - methanol (17:3)], and a 0.1 mL portion was subjected to HPLC on an Ultrasil cation-exchange silica (10 µm) column (25 cm x 4.6 mm) at 60°C with a mobile phase flow rate of 0.75 mL min-1, post-column mixing at 70°C with NaOH and ninhydrin solution and fluorescence detection with a 470 nm cut-off filter (excitation at 390 nm). Urine was diluted tenfold with water before injection of a 20 µL portion. Calibration graphs were rectilinear for 1 to 1000 ng mL-1 of methylguanidine in plasma and 0.1 to 600 µg mL-1 in urine, and the detection limit was 100 pg. The intra- (n = 5) and inter-day (n = 15) coefficient of variation for 10, 100 and 1000 ng mL-1 of methylguanidine in plasma were 2.49, 1.30 and 1.38% and 7.51, 5.20 and 7.98%, respectively.
Methylguanidine Blood Plasma Urine HPLC Fluorescence

"Metalloprotein Separation And Analysis By Directly Coupled Size Exclusion High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectroscopy"
Anal. Biochem. 1990 Volume 186, Issue 2 Pages 187-201
A. Z. Mason*, S. D. Storms and K. D. Jenkins

Abstract: The feasibility of using directly coupled size exclusion high performance liquid chromatography inductively coupled plasma mass spectroscopy (HPLC/ICP-MS) for the separation and subsequent elemental analysis of metalloproteins in biological samples has been studied. Data, on up to eight elements, was acquired simultaneously and the reconstructed elemental profiles from the chromatographed samples were quantified by flow injection analysis. Absolute and relative detection limits, reproducibility, operational dynamic range, and linearity of response were initially evaluated by analyzing standards of metallothionein protein of known elemental composition for Cd, Zn, and Cu. There was evidence of displacement of Zn from the protein during chromatography and the substitution of Cu sequestered from the mobile phase. Cd associated with the protein was fully recovered during chromatography. Memory effects, due to protein adsorption to the glassware in the torch box, were minimal and there was no degradation of the resolution of the chromatographed peak during extended transport through the HPLC/ICP-MS interface. The versatility of the technique has been demonstrated by the quantitative multi-element analysis of cytosolic metal-binding proteins separated from the polychaete worm Neanthes arenaceodentata. Fidelity of analysis has been demonstrated by two independent procedures: first, by comparing the elemental profiles obtained by directly aspirating the HPLC eluant into the ICP-MS to those obtained by collecting fractions and quantifying the metal content of the proteins in the conventional analytical mode; second, by comparing the stable isotopic profiles for 114Cd obtained by simultaneous ICP-MS analysis with radiometric profiles of 109Cd obtained by counting radioactivity associated with collected fractions.(ABSTRACT TRUNCATED AT 250 WORDS)
Proteins, metallo Mass spectrometry HPLC

"Flow Injection Analysis Of Serum Urea Using Urease Covalently Immobilized On 2-fluoro-1-methylpyridinium Salt-activated Fractogel And Fluorescence Detection"
Anal. Biochem. 1990 Volume 188, Issue 2 Pages 325-329
D. Narinesingh, R. Mungal and T. T. Ngo

Abstract: Serum samples were analyzed for their urea content using fluorescence flow injection analysis incorporating an immobilized urease bioreactor and a gas permeable separator. The urease was immobilized under mild and facile conditions to a hydrophilic 2-fluoro-1-methylpyridinium-activated support. The ammonia released as a result of urease-catalyzed urea hydrolysis diffused through a gas permeable membrane into a constant stream of o-phthaldehyde solution to form a highly fluorescent product with lambda ex at 340 nm and lambda em at 455 nm. Up to 25 serum samples can be analyzed per hour. The within-day coefficient of variation (CV) was 1.12% and the day-to-day CV was 1.25% for serum containing 10.50 mg urea nitrogen dl-1. The bioreactor shows excellent storage (at 4°C) and operational stabilities (at 37°C). Urea was determined in serum by flow injection analysis (illustrated) with urease immobilized on 2-fluori-1-methylpyridinium toluene-4-sulfonate-activated Fractogel. The ammonia released diffuses through a gas-permeable membrane into a stream of phthalaldehyde. The fluorescence of the resulting product is measured at 455 nm (excitation at 340 nm). Calibration graphs were rectilinear up to 1400 mg dl-1 and the detection limit was 0.1 mg dl-1. Recovery was 98 to 103% and coefficient of variation were 1.5%.
Urea Blood Serum Fluorescence

"Determination Of Tin In Biological Samples Using Gaseous Hydride Generation - Inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Biochem. 1990 Volume 190, Issue 1 Pages 71-77
Katsuhiko Yokoi, Mieko Kimura and Yoshinori Itokawa

Abstract: Liver, brain, testis or kidney was homogenized and heated with HNO3 and HClO4 in Kjeldahl flasks until white fumes appeared. Water was added with heating until the solution was clear and colorless. An aliquot of the solution was treated with trichloroacetic acid (I) and diluted with water to 0.2% in I. This solution was mixed, in a continuous-flow hydride-generation system (diagram given), with 1% I solution and then with 0.5% NaBH4 in 0.1% NaOH solution and passed through a gas - liquid separator (design presented) and the hydride, in an Ar-stream, was determined by ICP-AES at 189.989 nm. The limit of detection was 30 pg mL-1 of Sn, mean recovery was 87 to 99% and the coefficient of variation was 1.2%.
Tin Liver Brain Kidney Testis Spectrophotometry

"Amperometric Determination Of Isoniazid In A Flowing Stream At The Glassy Carbon Electrode"
Anal. Lett. 1983 Volume 16, Issue 12 Pages 913-924
Mumtaz H. Shah; James T. Stewart

Abstract: The detector incorporated a vitreous-carbon electrode (area 5 mm2), an auxiliary platinum electrode and a silver - AgCl reference electrode. Acetonitrile - aqueous 0.1 M LiClO4 (9:1) was pumped (at 1 mL min-1) through the electrochemical cell (Bioanalytical Systems Model TL-5A; Kel-F), samples (<50 µL) containing isoniazid were injected into the flow, and the current was measured at +825 mV. The calibration graph was rectilinear over the range 0.05 to 6 µg mL-1 of isoniazid, and the detection limit was 0.5 ng. Sources of interference, which are relatively few, are reported.
Isoniazid Pharmaceutical Amperometry 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

"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

"Indirect Atomic Absorption Spectrometric Determination Of Ammonia, Thiosulfate And Cyanide In An Unsegmented Flow System"
Anal. Lett. 1990 Volume 23, Issue 6 Pages 1069-1086
F. T. Esmadi; M. Kharoaf; Abdulrahman S. Attiyat

Abstract: A flow injection analysis method (FIA), has been developed for the determination of cyanide, thiosulfate and ammonia by atomic absorption spectrometry (AAS). Aqueous solution of the analyte was injected into an on-line column containing glass beads and packed with silver chloride and deionized water was used as the carrier. The analyte dissolves the silver chloride and the dissolved silver complex is introduced to the nebulizer of the AAS. This method has proved to be sensitive, simple and precise. Detection limits of 1.0 x 10^-7 M, 5.0 x 10^-7 M and 5.0 x 10^-6 M were obtained for thiosulfate, cyanide and ammonia, respectively. The precision of the technique was 2.0%, 2.4% and 1.4% in case of thiosulfate, cyanide and ammonia, respectively. The effects of flow rate and sample volume on the FIA/AAS signals are presented.
Ammonia Thiosulfate ion Cyanide Spectrophotometry

"Extractable Sulfate-sulfur, Total Sulfur And Trace-element Determinations In Plant Material By Flow Injection Analysis. 2. Total Sulfur And Copper, Zinc, Manganese And Iron In Plant Material"
Anal. Lett. 1990 Volume 23, Issue 4 Pages 675-702
D. L. Heanes

Abstract: Oven-dried samples (200 to 500 mg) were digested (at 100 samples per day) with HNO3 containing HClO, NH4NO3 and CaCl2 in a Pyrex tube at 60°C to 220°C (details given). The cooled digest was diluted to 15 mL with water and a flow injection analysis (FIA) system was used for the turbidimetric determination of total S in the supernatant solution, with the use of aqueous 0.01% Brij 35 as carrier solution, aqueous 1% Na ascorbate as sample diluent, and 0.25% of Na2EDTA in 0.1 M NaOH and 11% of BaCl2.2H2O in 1% gum arabic as reagent solution (valve switch timing sequence given). The throughput rate was 120 samples h-1. Calibration graphs were rectilinear for 1 to 200 mg mL-1 of sulfate-S in 0.25 M HClO4. The detection limit was 8 mg kg-1 in plant material. In the determination of 100 mg L-1 of sulfate-S in 0.254HClO4 and the analysis of kale, lucerne hay and oat grain, the coefficient of variation was 0.7% (n = 10). The recovery of 0.2% of S in plants was 97 to 104%. There was no interference from 6% of Ca, 5% of Mg, Na or K, 2.5% of Si, or 0.5% of P or N. A procedure for the FIA of Zn, Mn, Cu and Fe with AAS detection was also described.
Sulfate Sulfur Copper Zinc Manganese Iron Vegetable Oat Lucerne Sample preparation Spectrophotometry Turbidimetry

"Flow Injection Amperometry Of Cysteine And Glutathione At An Electrode Modified With A Ruthenium-containing Inorganic Film"
Electroanalysis 1990 Volume 2, Issue 2 Pages 107-112
James A. Cox *, Thomas J. Gray

Abstract: A vitreous-carbon electrode modified with a thin film of Ru oxides (prep. described) promotes the diffusion-controlled oxidation of cysteine and glutathione at +0.92 V (vs. Ag - AgCl). In flow injection amperometry in 0.2 or 0.02 M K2SO4 (pH 2.0), log. - log. calibration graphs were rectilinear over three orders of magnitude, and detection limits (injection volume 7.5 µL) were 1 µM. Up to 60 samples h-1 could be analyzed, and there was no evidence of electrode fouling during use. The electrode exhibited no change in sensitivity after regular use during 2 weeks.
Cysteine Glutathione Amperometry Electrode

"Flow-reversal Injection Analysis For Improved Stripping Voltammetry"
Electroanalysis 1990 Volume 2, Issue 2 Pages 127-132
Joseph Wang *, Huang Huiliang, Wladyslaw Kubiak

Abstract: Repeated reversal of the flow direction during deposition in flow injection stripping voltammetry promotes improved plating efficiency and hence better detection limits. In the determination of Pb2+ at a Hg-coated carbon-fiber electrode, a 13-fold enhancement in response was obtained by application of 10 flow oscillations, which corresponded to a detection limit of 7 nM as compared with 90 nM with a once-through system. The calibration graph (15 oscillations) was rectilinear in the range 0.1 to 0.8 µM-Pb (injection volume 0.1 ml); at 0.5 µM (10 oscillations) the coefficient of variation (n = 10) was 6%. The better plating efficiency also permits use of smaller sample volume.
Lead(2+) Voltammetry Electrode

"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

"Determination Of The Pesticide Guthion By Flow Injection Analysis With Amperometric Detection"
Electroanalysis 1990 Volume 2, Issue 6 Pages 487-492
J. Hern&aacute;ndez M&eacute;ndez, R. Carabias Mart&iacute;nez*, E. Rodr&iacute;guez Gonzalo, J. P&eacute;rez Trancon

Abstract: Guthion, a pesticide, was determined by flow injection analysis using single- and three-channel systems with and without a chemical reaction. The experimental variables involved in each case were investigated and optimized, and the analytical features of the two procedures were compared. A method based on the oxidation of anthranilic acid yielded in the alkaline hydrolysis of the pesticide at a glassy carbon electrode is proposed for its determination. The detection limit is 4.1 times 10^-7 M, and the relative standard deviation is 2.2% (n = 10) when the hydrolysis reaction takes place within the three-enamel manifold. The method is based upon the oxidation at a vitreous-carbon electrode of anthranilic acid (I) produced in the alkaline hydrolysis of the cited pesticide (II). A methanolic solution of I is injected (157 µL) into a 0.06 M acetic acid - 0.04 M Na acetate - 20% methanol carrier stream that is subsequently mixed with 0.4 M NaOH and passed through a 2-m reaction coil. Then 0.5 M acetic acid is added to the reaction mixture and the resulting solution is passed through a 49-cm tubular reactor and into the detector cell where I is determined amperometrically at +1.2 V (vs a Ag - AgCl electrode) at a wall-jet vitreous-carbon electrode. The calibration graph is rectilinear for 96.6 µM-II and the detection limit is 0.41 µM. At 38.6 µM the coefficient of variation was 2.2% (n = 10). By carrying out hydrolysis separately and using a single channel flow injection system the limit of detection is reduced to 18 nM-II. In this instance the calibration graph was rectilinear for 28.0 µM-II and for 0.84 µM-(II) the coefficient of variation was 2.5% (n = 10).
Pesticides Guthion Amperometry 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

"Determination Of Sterigmatocystin In Fermentation Broths By Reversed-phase High Performance Liquid Chromatography Using Post-column Fluorescence Enhancement"
J. Chromatogr. A 1990 Volume 523, Issue 1 Pages 305-311
Frank L. Neely* and Curt S. Emerson

Abstract: Sterigmatocystin (I, fungal toxin often found in food) was separated from the broth by homogenization with methanol, filtration, extraction of I from the filter-cake with methanol and 0.45 µm re-filtration of the supernatant solution A portion of solution was subjected to HPLC in a column (25 cm x 4.6 mm) of Beckman Ultrasphere C18 (5 µm) with use of a guard column (1.5 cm x 3.2 mm) of Brownlee Newguard RP-18 (7 µm), a mobile phase (0.5 mL min-1) of aqueous 88% methanol, post-column derivatization (reaction coil diameter 0.01 in.) at 35°C with aqueous 5% AlCl3 (added at 0.5 mL min-1) and fluorimetric detection at 455 nm (excitation at 254 nm). The limit of detection was 0.09 ppm, with rectilinear calibration range from 0.1 to 15 ppm and coefficient of variation (n = 12) of 0.2% at 0.82 ppm. A TLC separation on Whatman LK-5D silica with a mobile phase of 1% acetic acid in CCl4 - CHCl3 (1:1) and fluorimetric detection of the same derivative is summarized.
Sterigmatocystin Fermentation broth HPLC Fluorescence Sample preparation

"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

"Chemical Reaction Detection Of Catechins And Proanthocyanidins With 4-dimethylaminocinnamaldehyde"
J. Chromatogr. A 1989 Volume 467, Issue 1 Pages 185-193
D. Treutter

Abstract: The cited flavanols were determined in crude plant extracts and beverages by HPLC on a column (25 cm x 4 mm) of Hypersil ODS (3 µm), with gradient elution from 5 to 90% of methanol in 5% acetic acid. Post-column derivatization was carried out with 1% 4-dimethylaminocinnamaldehyde solution in methanolic 1.5 M H2SO4 and detection was at 640 nm. Sensitivity was improved 200 to 40,000-fold for (-)-epicatechin compared with other phenols and substituted indoles; the detection limit was 2.5 ng. For terpenes, this factor ranged from 4000 to 2,000,000. The selective detection of catechins and proanthocyanidins extracted from tea and beer is described.
Catechins Proanthocyanidins Beer Tea HPLC Spectrophotometry

"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 Pseudouridine In Human Urine And Serum By High Performance Liquid Chromatography With Post-column Fluorescence Derivatization"
J. Chromatogr. A 1990 Volume 515, Issue 1 Pages 495-501
Yoshihiko Umegae, Hitoshi Nohta and Yosuke Ohkura

Abstract: Urine (100 µL) was mixed with 100 µL of 0.5 mM 5-fluorouridine (I; internal standard) and 800 µL of water. Serum (0.5 ml) was mixed with 0.5 mL of 0.05 mM I and 0.5 mL of 2 M HClO4, and the mixture was centrifuged at 1000 g and 4°C for 10 min. The supernatant solution (0.5 ml) was mixed with 65 µL of 2 M K2CO3 and re-centrifuged. An aliquot (100 µL) of either solution was analyzed by HPLC on a column (15 cm x 4.6 mm) of TSK gel ODS-80 (5 µm), with 2 or 4% of methanol in 10 mM phosphate (pH 5.0) as mobile phase (0.5 mL min-1). Detection was at 254 nm, and, after mixing the eluate with 2 mM NaIO4 and 20 mM 1,2-bis-(4-methoxyphenyl)ethylenediamine (each at 0.25 mL min-1), by fluorimetry at 470 nm (excitation at 340 nm). Calibration graphs were rectilinear for 0.5 to 50 nmol of pseudouridine in 100 µL of urine or 0.1 to 4 nmol of I in 0.5 mL of serum. Limits of detection were 40 and 8 nM, respectively.
Pseudouridine Urine Serum Human HPLC Fluorescence

"High Performance Liquid Chromatographic Determination Of Some Polar Phospholipids In Serum"
J. Chromatogr. B 1989 Volume 495, Issue 1 Pages 61-70
Jir&iacute; B&ouml;swart, Thomas Schmidt, Pavel Kostiuk, Vera Pac&aacute;kov&aacute; and Karel Stul&iacute;k

Abstract: The experimental conditions have been optimized for high performance liquid chromatographic determination of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM) in serum. The phospholipids are separated on a silica gel column, using a mobile phase of acetonitrile-methanol-water (100:10:18, v/v), with ultraviolet photometric detection at 200 nm. The limit of detection was 0.2 µg (in 20 µL) for natural phospholipids and 2.5 µg for synthetic phospholipids; the relative standard deviation was ~5%. An alternative detection is tensammetry at a mercury electrode, at a potential of -1.8 V, with an a.c. current frequency of 60 Hz and an amplitude of 20 mV. The tensammetric detection has an advantage in its independence of the structure of the phospholipids. In measurements without a column (flow injection analysis), the tensammetric detection also yields a somewhat lower limit of detection than photometry (0.15 µg per 20 µL), but this value increases more than ten times in chromatographic detection. The precision is poorer and is more susceptible to interferences. The method was applied to the determination of the above substances in the blood of obese children, as a function of physical stress and spa treatment. It was shown that physical exercise causes a decrease in the contents of PE and PC in the patients. On the other hand, the spa treatment has no pronounced effect on the phospholipid content in the blood.
Phosphatidylethanolamine Phosphatidylcholine Sphingomyelin Blood Serum HPLC Electrode Sensor

"Rapid And Sensitive Determination Of Nucleoside H-phosphonates And Inorganic H-phosphonates By High Performance Liquid Chromatography Coupled With Flow Injection Analysis"
J. Chromatogr. A 1990 Volume 507, Issue 1 Pages 103-111
Yoshinobu Baba, Mitsutomo Tsuhako, and Norimasa Yoza

Abstract: A solution (100 µL) containing phosphate, phosphonate, hypophosphonate and isohypophosphonate was injected into a stream (1 mL min-1) of 0.1 to 0.3 M KCl containing 0.1% of Na4EDTA, and the phosphonates were separated on a column (25 cm x 4.0 mm) of TSKgel SAX (10 µm) and then mixed with chromogenic reagent (MoV - Mo(VI); 0.8 mL min-1) and oxidizing agent [aqueous NaHSO3 (104 g l-1); 0.2 mL min-1]. After detection at 260 nm, the solution was passed through a 20-m reaction coil at 140°C and the absorbance of the heteropoly blue complex was measured at 830 nm. The detection limit was ~1 µM for inorganic, sugar and nucleoside phosphonates.
Phosphonates HPLC Spectrophotometry

"Constant-potential Amperometric Detector For Carbohydrates At A Nickel(III) Oxide Electrode For Microscale Flow Injection Analysis And High Performance Liquid Chromatography"
J. Chromatogr. A 1990 Volume 515, Issue 1 Pages 213-220
Masashi Goto, Hiroyoshi Miyahara and Daido Ishii

Abstract: The cited amperometric detector is described and illustrated. The tubular cell comprises a Ni wire (25 or 50 µm diameter x ~5 mm) inside a fused-silica tube (50 or 100 µm), and has an effective cell volume of 30 mL. The active Ni2O3 is formed in situ on the electrode surface at ~0.5 V vs. Ag - AgCl; the Ni(III) acts as a strong oxidizing agent, reacting with carbohydrates by H abstraction to yield a radical. The detector was successfully applied in flow injection analysis and HPLC determination of various sugars such as aldo-pentoses and -hexoses, sugar alcohols and di- and tri-saccharides. The detection limit for glucose by flow injection analysis was 0.1 ng.
Sugars Electrode HPLC Amperometry

"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

"Post-column Reaction Detection And Flow Injection Analysis"
J. Chromatogr. A 1990 Volume 535, Issue 1-2 Pages 41-53
H. Engelhardt, R. Klinkner and G. Sch&ouml;ndorf

Abstract: The principles, synergic effects and potentials of post-column derivatization with non-dispersive chemical-reaction detection and essentially dispersive flow injection analysis are compared. Use of low-dispersion knitted open tubes improved sensitivity 10 to 50-fold; detection limits were also lowered by various modifications of the flow injection analysis principle, viz., forced mixing in a branched system; inverse flow injection analysis and plug injection of solute and reagent in an inert carrier. For plug injection, the use of chromogenic reagents and solutes can reduce reagent consumption.

"High Performance Liquid Chromatographic Analysis Of Unchanged Cis-diamminedichloroplatinum (cisplatin) In Plasma And Urine With Post-column Derivatization"
J. Chromatogr. B 1990 Volume 529, Issue 1 Pages 462-467
Masafumi Kinoshita, Naomi Yoshimura and Hiroyasu Ogata, Daijiro Tsujino, Toshiaki Takahashi, Satoru Takahashi, Yuji Wada and Kazuhiko Someya, Tetsuro Ohno, Keisou Masuhara and Yoshio Tanaka

Abstract: Plasma was ultra-filtered and analyzed directly. Urine was centrifuged and diluted 1:10 before analysis. HPLC was carried out on a column (15 cm x 4.6 mm) of Hitachi No. 3013-N anion-exchange resin (5 µm), with a Guard-Pak CN pre-column and acetonitrile - 10 mM NaCl (17:3) as mobile phase (0.7 mL min-1). The eluate was mixed with 26 µM-K2Cr2O7 (0.14 mL min-1) and 6.6 mM NaHSO3 (0.7 mL min-1), and cisplatin was determined as Pt by AAS at 265.9 nm (heating program given). The limit of detection was 80 ng mL-1 and the calibration graph was rectilinear for 30 µg mL-1. Recovery was 95.0 to 104.0% from plasma and 98.0 to 103.8% from urine, with corresponding coefficient of variation of 4.9 to 7.9% and 3.0 to 5.5%. The method is applicable to pharmacokinetic studies.
Blood Plasma Urine HPLC

"Quantitation Of Busulfan In Plasma By High Performance Liquid Chromatography Using Post-column Photolysis"
J. Chromatogr. B 1990 Volume 532, Issue 1 Pages 429-437
Joachim Blanz, Cornelius Rosenfeld, Barbara Proksch and Gerhard Ehninger, Klaus-Peter Zeller

Abstract: Plasma was applied to a Bond Elut C8 cartridge and busulfan (I) was eluted with methanol by centrifugation. The eluate was heated at 70°C for 40 min with 4 M NaI and heptane and, after cooling, the organic phase was mixed with 2-methoxyethanol. The heptane phase was evaporated and the remaining extract was analyzed by HPLC on a column (25 cm x 4.6 mm) of LiChrosorb CN (5 µm) with a mobile phase (1 mL min-1) of aqueous 20% methanol, post-column derivatization in a photochemical reaction unit and detection at 226 nm. The calibration graph was rectilinear from 0.05 to 5 µg mL-1 of I and the limit of detection was 20 ng mL-1. Recovery was 93% and the intra- and inter-day coefficient of variation were 2.7 and 7.6 to 11.5%, respectively.
Busulfan Blood Plasma HPLC Spectrophotometry

"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

"A Microfabricated Flow-through Cell With Parallel-opposed Electrodes For Recycling Amperometric Detection"
J. Electroanal. Chem. 1997 Volume 436, Issue 1-2 Pages 27-34
Sunday A. Brooks and Robert T. Kennedy*

Abstract: Flow-through recycling electrochemical detectors with dual Au electrodes were fabricated using micromachining techniques. Detector cells contained two microband electrodes that were 50 µm wide by 3-5 mm long separated by a 5 or 10 µm gap in a parallel-opposed configuration. One electrode was defined in the bottom of a channel which was etched into the surface of a Si wafer while the other electrode was defined on a glass substrate. The depth of the channel defined the gap distance between the electrodes. The Si and glass pieces were anodically bonded together to create a flow cell. The stability and reproducibility of single and dual electrode cells were characterized with cyclic voltammetry and amperometry during flow injection analysis (FIA). Single electrode detectors had detection limits of 50 nM with root mean square noise in the 3-10 pA range. The dual electrode cells showed enhanced sensitivity over single electrode cells through detection of analyte molecules multiple times as they were transported through the cell. Signal enhancements up to 60-fold were obtained with dual electrode cells during FIA at a flow rate of 50 nL/min. Simulations predict that signal-to-noise ratio enhancements > 100-fold may be possible with appropriate designs.
Electrode Electrode Voltammetry Amperometry

"Bioamperometric Sensors For Phenol Based On Carbon Paste Electrodes"
J. Electroanal. Chem. 1989 Volume 266, Issue 1 Pages 47-55
M. Bonakdar, J. L. Vilchez and Horacio A. Mottola

Abstract: The sensors were prepared by incorporating K4Fe(CN)6 and poly-(4-vinylpyridine) in carbon - mineral oil paste and adding (i) the commercial enzyme monophenol monooxygenase or (ii) fresh Agaricus bisporus albida mushroom before packing the mixture into the cavity of a thin-layer cell (Bioanalytical Systems). Alternatively, the carbon paste and the fresh mushroom were separately packed into a dual-electrode thin-layer cell mounted in serial mode. Measurements were made in a continuous-flow system at -0.2 V vs.. Ag - AgCl; 0.1 M KCl (pH 7.5) was used as supporting electrolyte. Response to phenol was rectilinear up to 2.5 ppm with a slope of 7.8 nA ppm-1 for the electrode incorporating the commercial enzyme, with a detection limit of 14 ppb; that incorporating mushroom admixed with the mediator had a dynamic range above 15 ppm and the detection limit was 0.16 ppm. The dual electrode also responded rectilinearly. The electrodes are easier to construct and condition than those incorporating tyrosinase adsorbed on nylon membranes.
Phenol Sensor Electrode Electrode

"Electrocatalyst For Non-enzymic Oxidation Of Glucose In Neutral Saline Solutions"
J. Electroanal. Chem. 1997 Volume 424, Issue 1-2 Pages 43-48
Waldemar Gorski and Robert T. Kennedy*

Abstract: The potential of a carbon-fiber microelectrode in 0.2 mM Na2IrCl6/0.5 mM lead nitrate/0.1 M KNO3 was cycled between 0 and +1.15 V at 50 mV/s for 80 min. The resulting electrode could be used in the flow injection amperometric determination of glucose in PBS (pH 7.4) at +0.75 V vs. Na-saturated SCE; the response was linear from 0.1 mM to >20 mM (response time 50 ms), and the detection limit was 50 µM-glucose. The short- and long-term stability of the response and also the selectivity could be improved by coating the electrode with Nafion, but at the expense of response speed and sensitivity. An electroactive coating was deposited on the surface of carbon microelectrodes from solutions containing Pb(NO3)(2), Na2IrCl6 and KNO3 by scanning their potentials from 0.0 to 1.15 V. The coating, believed to be IrO2 entrapped inside a PbO2 matrix, catalyzes oxidation of glucose, and other carbohydrates (e.g. mannose), in a phosphate buffered saline solution at pH 7.4. The microelectrodes coated with iridium and lead oxides were used as amperometric detectors at 0.75 V (versus a sodium saturated calomel electrode) for flow injection analysis of glucose samples. The linear dynamic range extended from 0.1 mM up to at least 20 mM, and the detection limit was 50 µM for glucose. The stability and selectivity of the oxide-modified electrodes were improved by application of Nation(R) coating. The response of the Nafion(R)-coated electrode to 15 mM glucose was stable for four days. 34 References
Glucose Amperometry Electrode Electrode Electrode

"Improved Mediated Tyrosinase Amperometric Enzyme Electrodes"
J. Electroanal. Chem. 1997 Volume 425, Issue 1-2 Pages 1-11
Maria Hedenmo, Ar&aacute;ntzazu Narv&aacute;ez, Elena Dom&iacute;nguez* and Ioanis Katakis

Abstract: The electroreduction of the quinonoid products of the oxidation of phenols by monophenol monooxygenase in carbon-paste electrodes to two-electron-donating phenolic species in order to regenerate the active (oxy-) form of the enzyme in the presence of O2 has been made more efficient by the incorporation of bis-(4,4'-dimethyl-2,2'-bipyridyl)(1,10-phenanthroline-5,6-dione)osmium chloride as mediator in the carbon paste. The reduction-current response was thereby rendered mass-transport-limited. Both batch cyclic-voltammetric and flow injection experiments are described. Under flow injection conditions the presence of the mediator increased the current density threefold, decreased the detection limit by nearly two orders of magnitude, and increased the lifetime by more than one order of magnitude. For injection of a 20 µL sample into a carrier stream of 0.25 M phosphate buffer of pH 6.0 (0.7 ml/min) with the electrode maintained at -0.5 V vs. Ag/AgCl, the detection limits for phenol and catechol were both 10 nM, as compared with 500 nM and 250 nM, respectively, in the absence of the mediator.
Phenol Catechol Amperometry Electrode

"Development And Validation Of A Flow Injection Method For The Determination Of Albumin Tannate, The Active Component Of A Pharmaceutical Preparation"
J. Pharm. Biomed. Anal. 1997 Volume 15, Issue 4 Pages 447-452
L. G&aacute;miz Gracia and M. D. Luque de Castro*

Abstract: Powdered tablets (5 mg) were sonicated in aqueous 2.5% NH3 solution for 3 min. A portion (275 µL) was injected into a carrier stream (1 ml/min) of water which merged with a stream (1 ml/min) of aqueous 25% Folin-Ciocalteu reagent and passed through a mixing coil (30 cm x 0.5 mm i.d.). The flow then merged with a stream (1 ml/min) of 1 M NaOH and passed through a second mixing coil (200 cm x 0.5 mm i.d.) before passing to the detector where the reaction product was monitored at 760 nm. The calibration graph was linear for up to 50 mg/l albumin tannate (I) and the mean recovery was 100%. The detection limit was 0.56 mg/l. Sample throughput was 50/h. The intra- and inter-day RSD (n = 10) for 25 mg/l I were 1.17% and 1.76%, respectively. No interference was observed. A flow injection analysis method for the determination of albumin tannate in tablets is reported. After optimization of the variables involved, the method has been characterized and validated in terms of calibration using three procedures: repeatability and reproducibility; ruggedness; and selectivity. Finally, it has been applied to real samples (tablets).
Tannin albuminate Pharmaceutical Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Frusemide Or Sulfathiazole In Pharmaceuticals"
J. Pharm. Biomed. Anal. 1997 Volume 15, Issue 4 Pages 453-459
M. S. Garc&iacute;a, C. Sanchez-Pedre&ntilde;o*, M. I. Albero and V. R&oacute;denas

Abstract: Powdered tablets equivalent to 40 mg frusemide (I) or 50 mg sulfathiazole (I) were sonicated for 5 min with 0.6 mL and 1 mL 1 M NaOH, respectively, then diluted to 100 mL with water. Injection solutions were dissolved in water. Portions (72 µL) were injected into a carrier stream of water (1.2 ml/min) which merged with a stream (1.2 ml/min) of 3 mM PdCl2 in Britton-Robinson buffer of pH 5 and passed through a reactor (3 m x 0.5 mm i.d.) maintained at 55°C before the absorbance was measured at 410 nm. The calibration graphs were linear for 20-400 µM-I and 50-300 µM-II, the detection limits were 55 µM and 14 µM, respectively, and the RSD were 0.3% and 0.9%, respectively, (n = 10) at 0.2 mM I. The sampling frequency was 50/h. No interference was observed from ethacridine or ephedrine ricinoleate. Results agreed with those obtained by reference methods (spectrophotometry for I and amperometric titrimetry for II). Recoveries were >=98.9%. Two sensitive and fast flow injection spectrophotometric methods are proposed for the determination of frusemide or sulfathiazole based on the formation of colored complexes between these compounds and Pd(II) at pH 5.0 and 55°C. Using the peak height as a quantitative parameter, frusemide or sulfathiazole was determined at 410 nm over the range 2.0 x 10^-5-4.0 x 10^-4 M or 5.0 x 10^-5-3 x 10^-4 M, respectively. The methods were applied to the determination of these sulfonamides in pharmaceuticals.
Frusemide Sulfathiazole Pharmaceutical Sample preparation Spectrophotometry

"Flow Injection Analysis With Amperometric Detection Of Naltrexone In Pharmaceuticals"
J. Pharm. Biomed. Anal. 1997 Volume 16, Issue 1 Pages 15-19
M. T. Fern&aacute;ndez-Abedul and A. Costa-Garcia*

Abstract: Flow injection analysis (FIA) with amperometric detection using a carbon paste electrode is applied to the determination of naltrexone. The sample solution was injected into the carrier stream of 0.1 M perchloric acid, being determined by oxidation at +1.0 V vs. Ag/AgCl/sat. KCl using a flow rate of 4 mL min-1. A relative standard deviation of 1.5% was calculated for a concentration level of 10^-5 M (n = 17) without carrying out a carbon paste electrode pretreatment. Calibration curves were found to be linear between 2 x 10^-8 and 10^-5 M (almost three orders of magnitude) and the method has a detection limit of 2 x 10^-8 M. A simple and reproducible procedure is proposed for the determination of naltrexone in pharmaceuticals. The results compared favourably with those obtained by an HPLC-UV method.
Naltrexone Pharmaceutical Amperometry Electrode

"Polypyrrole, A New Possibility For Covalent Binding Of Oxidoreductases To Electrode Surfaces As A Base For Stable Biosensors"
Sens. Actuat. B 1990 Volume 1, Issue 1-6 Pages 537-541
W. Schuhmann, R. Lammert, B. Uhe and H. -L. Schmidt

Abstract: Pyrrole was electropolymerized on the surface of a Pt or graphite electrode, the polypyrrole film was nitrated with Cu(NO3)2.3H2O solution in acetic anhydride, and the nitro-groups were electroreduced to amino-groups to which glucose oxidase was bound after carobodi-imide activation. The resulting enzyme electrodes were compared with those prepared by immobilizing glucose oxidase on carbodi-imide-activated electro-oxidized graphite. The polypyrrole-based electrodes showed times to steady-state current 30 s in static and ~10 s in flow injection systems, and also showed good stability. The detection limit was ~5 µM-glucose (cf. ~1 µM for the oxidized graphite electrodes) and calibration graphs were rectilinear over three decades of concentration. Such electrodes can be used for 700 glucose determinations in a flow system.
Electrode Electrode Sensor

"Characterization Of A New Single-bore High-pressure Pneumatic Nebulizer For Atomic Spectrometry .2. Discrete Sample Introduction In Flame Atomic Absorption Spectrometry"
Spectrochim. Acta B 1993 Volume 48, Issue 12 Pages 1461-1470
Jos&eacute; Luis Todol&iacute;, Antonio Canals and Vicente Hernandis

Abstract: A study has been made of the analytical behaviour, with discrete sample introduction, of a new high-pressure pneumatic nebulizer as part of sample introduction systems in flame atomic absorption spectrometry. The nebulizer possesses a single bore for the gas and liquid flows. In comparison to the standard Meinhard nebulizer and under identical conditions, the new nebulizer exhibits a greater relative sensitivity (up to 4.5 times) that increases the lesser the gas flow and the greater the liquid flow. Precision is similar with both nebulizers, the detection limits being lower for the pressure nebulizer. The memory effect is likewise of the same order of magnitude for both nebulizers. The pressure nebulizer has also proven satisfactory when working with high salt content or organic solutions. [References: 24]
Spectrophotometry LC

"The Performance Of A Low Consumption Thermospray Nebulizer For Specific Use In Micro-HPLC And General Use In FI With ICP-AES Detection"
Spectrochim. Acta B 1991 Volume 46, Issue 6-7 Pages 1073-1088
J. W. Elgersma, J. Balke and F. J. M. J. Maessen

Abstract: The thermospray interface comprised a nebulizer with a fused silica vaporizer tube and a desolvation system containing a heated spray tube and condenser. The carrier stream was methanol - water (4:1) at 120 µL min-1 for HPLC and between 100 and 500 µL min-1 for the FI with an optimum at 400 µL min-1 and a sample of 80 µL. The limits of detection for eleven elements were 0.1 to 23 ng mL-1 in the FI mode.
Spectrophotometry HPLC

"Lophine Chemiluminescence For Determination Of Chromium(VI) By Continuous-flow Method"
Anal. Sci. 1989 Volume 5, Issue 4 Pages 429-433
T. KAMIDATE, K. YAMAGUCHI, T. SEGAWA and H. WATANABE

Abstract: Quantitative recovery of Cr(VI) was achieved by passage (10 mL min-1) of the aqueous sample (25 ml) through a column (20 cm x 7 mm) of activated alumina. The column was washed with 0.01 M HNO3 to remove other metal ions, then 0.2 M KOH (10 ml) was used to elute Cr(VI). The eluate was mixed with 0.02 M HNO3 and 0.3 M H2O2 in a continuous-flow analyzer. and the resulting solution was treated with methanolic 1 mM lophine and 0.3 M KOH in a chemiluminescence detection cell. The calibration graph (log. - log. plot) was rectilinear from the detection limit of 0.02 to 30 µg mL-1 of Cr(VI). The method was used to determine Cr(VI) in water.
Chromium(VI) Environmental Chemiluminescence

"Hydride-generation System With A Hydrogen Separation Membrane For Low-power Inductively Coupled Plasma Emission Spectrometry"
Anal. Sci. 1990 Volume 6, Issue 2 Pages 195-199
H. TAO, A. MIYAZAKI and K. BANSHO

Abstract: A hydrogen separation membrane module is described consisting of hollow aromatic polyimide fibers. The module, operated at ~90°C, was connected to a continuous-flow hydride generator (diagram given) for removal of H before analysis of the hydrides by ICP-AES with Ar as carrier gas. Detection limits obtained for As, Ge, Hg, Sb and Sn are tabulated. The coefficient of variation were 1% at 50 ng mL-1 of each element. Calibration graphs were rectilinear from the detection limit to 100 µg mL-1. Online pre-concentration with use of the module could not be carried out with He instead of Ar as carrier gas beause He permeated the membrane reducing its flow rate.
Arsenic Germanium Antimony Tin Spectrophotometry

"Spectrophotometric Determination Of Calcium With Dicyclohexano-24 Crown-8 And Propyl Orange By Solvent Extraction/flow Injection Method"
Anal. Sci. 1990 Volume 6, Issue 2 Pages 215-220
S. MOTOMIZU, M. OSHIMA, N. YONEDA and T. IWACHIDO

Abstract: The optimum conditions for the cited determination (flow diagram of apparatus given) were: an injection volume of 100 µL; water as carrier stream (0.8 mL min-1); 0.5 mM propyl organge - 0.1 mM LiOH as reagent solution (0.8 mL min-1); 2 mM dicyclohexano-24-crown-8 in benzene - chlorobenzene (1:1) as extractant; a PTFE extraction coil (2 m x 0.5 mm) and detection at 420 nm. The calibration graph was rectilinear up to 0.1 mM Ca and the detection limit was 0.2 µM. The coefficient of variation was 1% at 50 µM-Ca. Results for determination of Ca in river water agreed well with those by EDTA titration. The system can be applied in the determination of Sr and Ba if interference by Ca is accounted for.
Calcium River Spectrophotometry Sample preparation

"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

"High Performance Liquid Chromatographic Determination Of Ribonucleotides By Post-column Derivatization Involving Oxidation Followed By Fluorescence Reaction And Its Application To Human Erythrocyte Samples"
Anal. Sci. 1990 Volume 6, Issue 4 Pages 519-522
Y. UMEGAE, H. NOHTA and Y. OHKURA

Abstract: Ribonucleotides such as ATP and ADP were separated on a column (25 cm x 4.6 mm) of TSK gel ODS-80 (5 µm) and converted into fluorescent derivatives by reaction with 1,2-bis-(4-methoxyphenyl)ethylenediamine in acidic medium after oxidation with NaIO4. The detection limits were 14 to 67 pmol injected. The method was applied to human erythrocytes, and showed good sensitivity and high selectivity.
Ribonucleotides Human HPLC Fluorescence

"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

"High Performance Liquid Chromatographic Determination Of Acidic Catecholamine Metabolites In Human Urine Using Post-column Fluorescence Derivatization With Dl-1,2-diphenylethylenediamine"
Anal. Sci. 1990 Volume 6, Issue 5 Pages 677-682
H.-K. JEON, H. NOHTA and Y. OHKURA

Abstract: Urine was diluted 5-fold with water, ultra-filtrated, and 3,4-dihydroxymethoxymandelic acid, 4-hydroxy-3-methoxy- and 3,4-dihydroxy-phenylacetic acid and 4-hydroxy-3-methoxymandelic acid were determined by HPLC on a column (25 cm x 4.6 mm) of TSK gel DEAE-2SW anion-exchange gel (5 µm) with 25 mM NaH2PO4 (pH 3.0) - 70 µM-Na2EDTA containing 30% of acetonitrile as mobile phase (1 mL min-1) and electrochemical detection at 0.5 V vs. Ag - AgCl. The eluate was mixed with 40 mM dl-1,2-diphenylethylenediamine in propan-2-ol and 50 mM Na methoxide in propan-2-ol (0.4 mL min-1), the mixture was passed through a reaction coil (10 m x 0.5 mm) at 110°C. After cooling the fluorescence was monitored at 515 nm (excitation at 420 nm). The detection limits were 15 to 20 fmol. The method was 20-times more sensitive to 3,4-dihydroxymandelic acid than methods using meso-1,2-diphenylethylenediamine and did not require complicated sample cleanup.
Catecholamines Urine HPLC Fluorescence

"Selective Determination Of Inorganic And Total Mercury By Cold Vapor Atomic Fluorescence Spectrometry Coupled With Flow Injection Analysis"
Anal. Sci. 1990 Volume 6, Issue 1 Pages 91-95
H. MORITA, M. SUGIMOTO and S. SHIMOMURA

Abstract: An aqueous sample (0.6 ml), containing 0.5 to 20 ppb of Hg(II), is injected into a stream of 0.5 M H2SO4. Organomercury compounds, e.g., methylmercury chloride, are irradiated in a flow system for 1.5 min in 0.05 M H2SO4 with a 400-W UV lamp before sample injection. The Hg(II) is reduced to elemental Hg with SnCl2 solution (1 to 10%) in 0.5 M H2SO4, and the Hg is separated by passage through PTFE tubing counter-current to a flow of Ar in an outer tube. Any water in the Ar is removed by condensation at -5°C and Hg is determined by AFS in a special cell with irradiation at 253.7 nm and measurement with a solar-blind photomultiplier. The limit of detection is 0.18 ppb of Hg is reported. Of the substances tested only cysteine interferes in the determination of total Hg probably via decomposition to S2-. The coefficient of variation were 2% (n = 10). The sampling rate was 20 h-1.
Mercury Methylmercury ion River Water Estuarine Fluorescence

"Flow Injection Technique For Determination Of Thallium, Lead And Bismuth In Nickel-base Alloys By Inductively Coupled Plasma Mass Spectrometry"
Anal. Sci. 1990 Volume 6, Issue 2 Pages 191-194
T. MOCHIZUKI, A. SAKASHITA, H. IWATA, Y. ISHIBASHI and N. GUNJI

Abstract: Nickel-based alloy (0.25 g) was dissolved in 10 mL of HCl - HNO3 (6:1). The solution was evaporated to dryness and evaporation was repeated with 7 M HNO3 (5 ml). The residue was dissolved in 7 M HNO3 (5 ml) and 2.3 M HF solution (2 ml) and the solution was diluted to 50 mL with water. A portion of this solution (240 µL) was injected into a stream of 0.7 M HNO3 - 0.09 M HF (0.6 mL min-1) and passed to the ICP-MS instrument (operating conditions described). Detection limits for Tl, Pb and Bi were 0.001, 0.04 and 0.007 ppm, respectively. Results agreed with certified values.
Thallium Lead Bismuth Alloy NIST 897 NIST 898 NIST 899 Mass spectrometry

"Micelle Enhanced Spectrofluorometric Determination Of L-ascorbic-acid Based On Laccase-linked Coupling Reaction Using Flow Injection Stopped-flow Technique"
Anal. Sci. 1997 Volume 13, Issue suppl Pages 67-70
HOUPING HUANG, RUXIU CAI, TAKASHI KORENAGA, XINXIANG ZHANG, YI YANG, YUMIN DU, and YUN'E ZENG

Abstract: A novel spectrofluorimetric method for determination of L-ascorbic acid is described. It is based on the inhibition of L-ascorbic acid on the formation df 2,3-diaminophenazine, which is an oxidation product of o-phenylenediamine catalyzed by laccase, in the presence of Brij-35, which shows strong enhancement on the fluorescence(at lambda em/lambda ex=530 nm/430 nm) of the product, while no effect on the laccase-catalyzed reaction. The mechanism of o-phenylenediamine oxidation reaction catalyzed by laccase in the presence of L-ascorbic acid is discussed. L-ascorbic acid is determined in the range of 0.02 similar to 2.0 µg/ml with a detection limit of 0.014 µg/ml. The method is applied to the determination of L-ascorbic acid in pharmaceuticals, the results agree well with the nominal values and those obtained by the reference method. 20 References
l-Ascorbic acid Pharmaceutical Pharmaceutical Fluorescence

"Factors Affecting Detection Limit In Flow Injection Solution Spectrophotometry"
Anal. Proc. 1988 Volume 25, Issue 3 Pages 89-90
Andrew B. Marsden, Julian F. Tyson

Abstract: Strategies for minimization of baseline noise in flow injection - spectrophotometric systems are discussed and tested. Devices used included dampers to lessen pump roller noise, optimized design of the confluence junction of merging streams, and the introduction of intervening mixing stages, e.g., a packed-bed reactor and/or a reaction coil between the noise sources and the detector. Best results were achieved with packed-bed and open-tube coil reactors both included between the confluence point and the detector.
Chloride Spectrophotometry

"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 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

"Chemiluminescence Detection Of A Benzodiazepine"
Anal. Proc. 1989 Volume 26, Issue 11 Pages 368-369
Anthony R. J. Andrews, Alan Townshend

Abstract: Seven benzodiazepines (concentration. 1 mM) were examined for chemiluminescence in a flow injection system with various oxidizing and reducing reagents and water as carrier. Only loprazolam (I), with acidic KMnO4 as reagent, gave a measurable response. Optimum conditions for the determination of I were; water as solvent, 0.94 M formic acid, adjusted to pH 0.9 with HCl, as carrier, 0.2 mM KMnO4 as reagent, and a flow rate of 1.3 mL min-1 in the sample and reagent lines. The calibration graph was rectilinear from 0.01 to 5 mM I, and the detection limit was 7 µM. Of 12 metal ions examined, only Fe(II) and Mn(II) interfered. The method could be used to determine I in tablets; excipients did not interfere.
Loprazolam Benzodiazepine, derivatives Pharmaceutical Chemiluminescence

"A Comparative Study Of Methods For Determining Selenium In Biological Materials"
Acta Cient. Venez. 1990 Volume 41, Issue 1 Pages 5-10
Burguera, J.L.;Burguera, M.;Gallignani, M.;Alarcon, O.M.

Abstract: A comparative study of the analytical performance of fluorimetric spectrophotometric, atomic absorption spectrometric, flow injection analysis with atomic absorption spectrometric, flow injection analysis with atomic absorption spectrometric detection, hydride generation with atomic absorption spectrometric detection and hydride generation with molecular emission cavity analysis detection methods has been carried out for the determination of selenium in biological materials. Based on results concerning detection limit, linearity and sensitivity, only the fluorimetric and hydride generation with atomic absorption spectrometric detection methods were suitable for the determination of selenium in biological materials. Whereas, the spectrophotometric, flame absorption spectrometric flow injection atomic absorption spectrometric and hydride generation with molecular emission cavity detection, due to its worse detection limits and poorer sensitivities, were found to be unsuitable for the determination of selenium in such matrices. The accuracy of the fluorimetric and hydride generation with atomic absorption spectrometric detection methods were tested by using NBS standard reference materials.
Selenium Biological material Spectrophotometry Fluorescence Spectrophotometry Spectrophotometry

"Determination Of Nitrate In Carbon Black By Flow Injection Analysis With Potentiometric Detection"
Analusis 1997 Volume 25, Issue 2 Pages 32-35
IG. Canal, JLFC Lima, MCBSM Montenegro, R Prez-Olmos

Abstract: H2O (100 ml) was added to 10 g C black (details given) and the mixture incubated at 100°C for 5 min. The resulting suspension was filtered and the residue washed and diluted to 100 mL with water. A 150 µL portion was injected into channel 1 of a double channel manifold containing 10 µM-sodium nitrate. The resulting solution was mixed in a 70 cm reaction tube with carrier in channel 2 which comprised sodium sulfate or a solution of 0.02 M lead acetate, 0.01 M lead monoxide, 0.02 M potassium acetate and 0.01 M sulfamic acid. A flow rate of 6.8 ml/min was used. Nitrate levels were determined by an electrode which incorporated a PVC membrane and an ionic sensor based on tris(4,7-diphenyl-1,10-phenanthroline)nickel(II) complex dissolved in 2-nitrophenyl octyl ether. The lower limit of the linear range and the limit of detection were 70 and 30 µM, respectively. Levels of nitrate in C black are reported, with recoveries and RSD of 98.8-103.4% and 0.3-3.7% (n = 3), respectively. This paper reports the potentiometric detection of nitrate in carbon black samples by flow injection analysis (FIA). The detection system used consisted of a nitrate sensitive tubular electrode without inner reference solution, incorporating a PVC membrane with an ionic sensor based on tris(4,7-diphenyl-1,10-phenantroline) nickel(II) dissolved in 2-nitrophenyloctyl ether as the solvent mediator. According to the working characteristics of the tubular electrodes, a double channel flow injection system was constructed and optimized for direct sample analysis in a reduced time-frame. A solution of Pb(CH3COO)(2), PbO, CH3COOK and NH2SO3H was used as ionic strength and pH adjuster for both samples and standards. The tubular electrodes showed a linear response for a concentration of at least 5 10^-5 mol.L-1 with a slope of 58.3±0.9 mV/decade and a reproducibility of±0.1 mV within two successive calibrations. Analysis of 10 different samples from several factories showed satisfactory results with average recoveries of about 100.5%±1.5% and a variation coefficient of 1.5%. With the proposed system, a sampling rate of 120 samples/h was obtained. (11 References)
Nitrate Inorganic compound Electrode Electrode Potentiometry

"A Chemiluminometric Method For NADPH And NADH Using A Two-enzyme Bioreactor And Its Application To The Determination Of Magnesium In Serum"
Biomed. Chromatogr. 1990 Volume 4, Issue 3 Pages 123-127
Masayoshi Tabata, Masayuki Totani, Takashi Murachi

Abstract: Chemiluminometric methods are described for the automated flow injection analysis of NADPH and NADH using an immobilized enzyme column reactor and serum magnesium. This application is for the clinical analysis of NADPH and NADH. The reactor for NADPH and NADH contains immobilized L-glutamate dehydrogenase and L-glutamate oxidase, and that for serum magnesium immobilized hexokinase, glucose-6-phosphate dehydrogenase, L-glutamate dehydrogenase and L-glutamate oxidase. Whtained from standard solutions and 0.5% from complex samples (at 1000 mg/L).
Magnesium Nicotinamide adenine dinucleotide oxidized Nicotinamide adenine dinucleotide phosphate oxidized Blood Serum Chemiluminescence Clinical analysis

"Enzyme Entrapped Polypyrrole Modified Electrode For Flow Injection Determination Of Glucose"
Biosens. Bioelectron. 1990 Volume 5, Issue 2 Pages 149-156
M. Trojanowicz, W. Matuszewski and M. Podsiada

Abstract: Immobilization of glucose oxidase in electropolymerized polypyrrole film on the surface of a platinum wire electrode, provides a convenient sensor for flow injection glucose determination. An upper limit of linear response for 100 µL injected sample volume was estimated as 20 mM, whereas a 500 µL injected sample volume gave an estimated detection limit of 0.5 mM. A simple electrode preparation procedure allows quick electrode renewal before each series of measurements. A Pt wire electrode was cleaned electrochemically in aqueous Na2HPO4 (50 g l-1) - KOH (20 g l-1) at 80°C by multiple polarizaiton. Electropolymerization was carried out at room temperature for 10 s at 0.8 V vs. the SCE in a solution containing glucose oxidase (1 g) and freshly distilled pyrrole (20 µL) in 6 mL of deaerated 0.1 M KCl. The electrode was used in a flow injection system (illustrated) with a 60-cm delay coil and a flow-through detector. The upper limit of rectilinear response for a 100 µL sample was 20 mM; for a 500 µL sample, the detection limit was 0.5 mM. The electrode signal declined by 20% after 5 days, but the active layer was easily renewed, and the system was applicable in clinical and food analysis.
Glucose Food Electrode Electrode

"Determination Of A Small Amount Of A Biological Constituent By The Use Of Chemiluminescence. 15. Zeolite Column - Chemiluminescence Detection System For The Separation And The Determination Of A Protein Mixture"
Bull. Chem. Soc. Jpn. 1989 Volume 62, Issue 5 Pages 1501-1508
Tadashi Hara,Kazuhiko Tsukagoshi and Yuichiro Kurita

Abstract: The adsorption behavior of proteins (human serum albumin and γ-globulin) on molecular sieve 13X (100 to 120 mesh; pore diameter 10 .angstrom.) was examined by the depletion method in aqueous solution and by using a column, with detection at 280 nm in each instance. Globulin was adsorbed by the zeolite but albumin was not. Conditions were optimized for separating and determining the two proteins by a flow injection - chemiluminescence system (illustrated) with 1,10-phenanthroline - H2O2 - Cu(II) (Ibid., 1986, 59, 1833) as reagent. A detection limit of 1 ng, an analytical range of 0.02 to 5 mg L-1 and coefficient of variation of 5.4 and 8.3% (n = 5) at 1 mg L-1 were achieved for albumin and γ-globulin, respectively, by using a microbore column (25 cm x 1 mm) of NaX zeolite, 10 mM phosphate buffer of pH 6.4 to 6.5 as carrier solution, and 13.2 mM NaOH - 5 mM NaCl (pH 12.0) as eluent. The method was applied in analysis of serum.
Proteins γ-Globulin Albumin Blood Serum LC Chemiluminescence

"Determination Of Hyaluronic Acid In Rabbit Plasma By HPLC With Fluorimetric Post-column Detection"
Bunseki Kagaku 1989 Volume 38, Issue 2 Pages 92-93
Mitsuma, R.;Yamanashi, S.;Toyoda, H.;Imanari, T.

Abstract: Unsaturated oligosaccharides produced by the enzymatic digestion of hyaluronic acid (I) were separated on a column (15 cm x 4 mm) of TSK gel NH2 60, at 45°C, with 10 mM ammonium formate buffer (pH 5.0) containing 6.5 mM Na2SO4 and 4% of acetonitrile as mobile phase (0.5 mL min-1). After derivatization with 1% 2-cyanoacetamide solution and 0.3 M NaOH at 100°C, fluorescence detection was at 383 nm (excitation at 331 nm). The detection limit was 10 ng of I.
Hyaluronic acid Plasma Rabbit HPLC Fluorescence Sample preparation

"Chemically Amplified Detection Of Nicotinamide-adenine Dinucleotides In A Flow Injection System With Immobilized-enzyme Reactors"
Bunseki Kagaku 1989 Volume 38, Issue 3 Pages 109-114
Yao, T.;Matsumoto, Y.;Wasa, T.

Abstract: Immobilized reactors containing glucose-6-phosphate dehydrogenase (I) and I - dihydrolipoamide dehydrogenase were used to improve detection of nicotinamide-adenine dinucleotides in a flow injection system containing a vitreous-carbon electrode for amperometric detection. In the former reactor, amplified response was achieved by enzyme reaction - chemical reaction recycling in the presence of 2 mM glucose 6-phosphate (II) and 0.2 mM phenazine methosulfate in carrier solution (0.1 M carbonate buffer of pH 8.5). In the latter reactor, response was amplified by enzyme reaction - enzyme reaction recycling in the presence of 2 mM II and 0.5 mM Fe(CN)63- in 0.1 M carbonate buffer of pH 7.5. Calibration graphs for the two reactors were rectilinear for 0.02 to 10 and 0.05 to 10 nmol injected, respectively. Corresponding detection limits for dinucleotides were ~6 and ~20 pmol. Response amplification factors increased at lower flow rates. Immobilized reactors containing glucose-6-phosphate dehydrogenase (I) and I - dihydrolipoamide dehydrogenase were used to improve detection of nicotinamide-adenine dinucleotides in a flow injection system containing a vitreous-carbon electrode for amperometric detection. In the former reactor, amplified response was achieved by enzyme reaction - chemical reaction recycling in the presence of 2 mM glucose 6-phosphate (II) and 0.2 mM phenazine methosulfate in carrier solution (0.1 M carbonate buffer of pH 8.5). In the latter reactor, response was amplified by enzyme reaction - enzyme reaction recycling in the presence of 2 mM II and 0.5 mM Fe(CN)63- in 0.1 M carbonate buffer of pH 7.5. Calibration graphs for the two reactors were rectilinear for 0.02 to 10 and 0.05 to 10 nmol injected, respectively. Corresponding detection limits for dinucleotides were ~6 and ~20 pmol. Response amplification factors increased at lower flow rates.
Nicotinamide adenine dinucleotide oxidized Amperometry

"Spectrophotometric Determination Of Quaternary Ammonium Ions Based On Micelle Extraction Of Ion Associates"
Bunseki Kagaku 1989 Volume 38, Issue 5 Pages 205-210
Hosoi, Y.;Motomizu, S.

Abstract: The effects of pH and surfactant concentration. on the micelle extraction of ion association complexes of alkylammonium ions and tetrabromophenolphthalein ethyl ester (I) were studied. A flow injection system is described, in which sample solution (120 µL) is injected into a carrier solution (0.8 mL min-1) of water and mixed in a reaction coil (1 m x 0.5 mm) with reagent solution (0.8 mL min-1) consisting of 20 µM-I and 0.02% of Triton X-100 in 0.2 M acetate buffer of pH 4.0. Detection is at 605 nm. Calibration graphs for several quaternary ammonium compounds cover the range up to ~10 µM.
Quaternary Ammonium Ion Spectrophotometry Sample preparation

"Improvement In FIA System For Determining Small Amounts Of Proteins With Chemiluminescence Detection"
Bunseki Kagaku 1989 Volume 38, Issue 7 Pages T100-T103
Tsukagoshi, K.;Kimoto, H.;Hara, T.

Abstract: The determination of proteins by flow injection analysis as described previously, e.g., Hara et al (Anal. Abstr., 1989, 51, 1D198), was improved by the combined use of irregular-pulse-free pumps and a temp.-controlled chemiluminescence detector. Bovine serum albumin was determined in the range 5 µg L-1 to 10 mg L-1 with a detection limit of 0.25 µg (sample volume 50 µL). The determination of proteins by flow injection analysis as described previously, e.g., Hara et al (Anal. Abstr., 1989, 51, 1D198), was improved by the combined use of irregular-pulse-free pumps and a temp.-controlled chemiluminescence detector. Bovine serum albumin was determined in the range 5 µg L-1 to 10 mg L-1 with a detection limit of 0.25 µg (sample volume 50 µL).
Proteins Chemiluminescence

"Determination Of Calcium By FIA With Glyoxal Bis-(2-hydroxyanil)"
Bunseki Kagaku 1989 Volume 38, Issue 9 Pages T129-T133
Zenki, M.;Kogawa, H.;Nose, K.;Toei, K.

Abstract: Calcium was determined in natural waters by the cited method. Glyoxal bis-(2-hydroxyanil) reagent (0.05%), 0.2 M NaOH and water were used as reagent, buffer and carrier solution, respectively, and were propelled (0.6 mL min-1) by plunger micropumps. Sample solution (290 µL) was injected into the carrier solution, mixed with reagent solution and then passed to a PTFE reaction coil (8 m x 0.5 mm). The absorbance of the red solution obtained was measured at 520 nm. The calibration graph was rectilinear for up to 1.2 ppm of Ca and the detection limit was 5 ppb. The coefficient of variation (n = 10) were 1.2 and 0.22% at 0.4 and 1 ppm of Ca, respectively. Results agreed well with those obtained by AAS. Calcium was determined in natural waters by the cited method. Glyoxal bis-(2-hydroxyanil) reagent (0.05%), 0.2 M NaOH and water were used as reagent, buffer and carrier solution, respectively, and were propelled (0.6 mL min-1) by plunger micropumps. Sample solution (290 µL) was injected into the carrier solution, mixed with reagent solution and then passed to a PTFE reaction coil (8 m x 0.5 mm). The absorbance of the red solution obtained was measured at 520 nm. The calibration graph was rectilinear for up to 1.2 ppm of Ca and the detection limit was 5 ppb. The coefficient of variation (n = 10) were 1.2 and 0.22% at 0.4 and 1 ppm of Ca, respectively. Results agreed well with those obtained by AAS.
Calcium Environmental

"Indirect Spectrophotometric Determination Of Fluoride By FIA Using Arsenazo III - Uranium Complex"
Bunseki Kagaku 1989 Volume 38, Issue 9 Pages 424-428
Zenki, M.;Sai, K.;Ye, Y.;Toei, K.

Abstract: Lanthanum (III), Th(IV) and U(VI) complexes of arsenazo III were evaluated as reagents. Optimum arsenazo III concentration, metal ion concentration, pH, reaction coil length and sample volume were investigated. The U(VI) complex was preferred. A 48 µM-arsenazo III solution (pH 2.8) was used as reagent solution Sample solution (196 µL) was injected into water (carrier solution); PTFE tubing (20 cm x 0.5 mm) was used as the reaction coil. The absorbance was measured at 606 nm. Cation interference was eliminated with use of a cation-exchange column. The calibration graph was rectilinear up to 1.5 ppm of F- and the detection limit was 50 ppb. The coefficient of variation was 0.45% for 0.5 ppm of F- (n = 10). The method was applied in determination of F- in well waters. Lanthanum (III), Th(IV) and U(VI) complexes of arsenazo III were evaluated as reagents. Optimum arsenazo III concentration, metal ion concentration, pH, reaction coil length and sample volume were investigated. The U(VI) complex was preferred. A 48 µM-arsenazo III solution (pH 2.8) was used as reagent solution Sample solution (196 µL) was injected into water (carrier solution); PTFE tubing (20 cm x 0.5 mm) was used as the reaction coil. The absorbance was measured at 606 nm. Cation interference was eliminated with use of a cation-exchange column. The calibration graph was rectilinear up to 1.5 ppm of F- and the detection limit was 50 ppb. The coefficient of variation was 0.45% for 0.5 ppm of F- (n = 10). The method was applied in determination of F- in well waters.
Fluoride Environmental Spectrophotometry

"Continuous Measurement Of Sulfate Ion In Environmental Water Samples By FIA"
Bunseki Kagaku 1990 Volume 39, Issue 9 Pages T129-T133
Korenaga, T.;Okada, K.;Takahashi, T.;Moriwake, T.

Abstract: The determination of SO42- in water samples, e.g., rain and snow, was achieved by using a FIA sensing device equipped with a double plungent micropump; an aqueous 80% ethanol solution containing a Ba - sulfonazo III complex and EDTA was used as color reagent for SO42-. Results agreed well with those obtained by the official titration method (r = 0.99). The coefficient of variation was 0.5% and the detection limit was 0.02 mg L-1 of SO42-. The method was applied to waste water.
Sulfate Rain Snow Waste Spectrophotometry

"Determination Of Oxalate By Flow Injection Analysis (FIA) With Electrogenerated Chemiluminescence Detection"
Bunseki Kagaku 1990 Volume 39, Issue 6 Pages 323-326
Uchikura, K.

Abstract: Sample (10 µL) was injected into the carrier stream of water (0.3 mL min-1) and mixed with reagent solution (0.8 mL min-1) of 10 mM H2SO4 containing 0.12 mM tris(bipyridyl)ruthenium dichloride (I). The oxidation potential of the working electrode in the home-made electrochemical reactor, in which tris(bipyridyl)ruthenium3+ was continuously generated from I, was maintained with a potentio-galvanostat. Calibration graphs were rectilinear up to 16 pmol of oxalate. The detection limit was 0.3 pmol and the coefficient of variation was 2.3% (n = 5). The method was applied to the determination of oxalate in urine. Relative chemiluminescence intensities are tabulated for >30 compounds; tryptophan interferes.
Oxalate Urine Chemiluminescence

"Continuous Determination Of Total Sulfur Oxide In Waste Gas By FIA"
Bunseki Kagaku 1990 Volume 39, Issue 2 Pages T29-T34
Korenaga, T.;Yokota, Y.;Okada, K.;Takahashi, T.;Moriwake, T.

Abstract: Sulfur oxides from exhaust gas were absorbed into 10% (v/v) H2O2 solution and the solution was subjected to flow injection analysis with 10% (v/v) H2O2 as carrier solution (0.3 mL min-1) and a Ba - sulfonazo III complex reagent solution (0.6 mL min-1). The reaction mixture was passed through a PTFE reaction coil (15 m x 10 mm) before spectrophotometric detection at 645 nm. The detection limit was 0.02 mg L-1 and the coefficient of variation was 0.5% for 5 mg L-1 of sulfur oxides. Results correlated well with those obtained by the official titration method (r = 0.996). The analysis time was 30 samples h-1.
Sulfur dioxide Waste Spectrophotometry

"Development Of A Determination Method For Acetylcholinesterase Activity By FIA With Electrochemical Detection"
Bunseki Kagaku 1997 Volume 46, Issue 4 Pages 293-296
Goto, M.;Kobayashi, M.

Abstract: An enzyme electrode was constructed by cross-linking choline oxidase using glutaraldehyde on a Pt disc of 200 µm diameter. The electrode was used for acetylcholinesterase (I) detection in a FIA system. The detection limit was 5 miu/ml I and the RSD (n = 6) at 0.1 iu/ml I was 1.6%.
Acetylcholinesterase Electrode Electrode

"Flow Injection Analysis With Light Emitting Diodes Sources"
Chem. Anal. 1990 Volume 35, Issue 6 Pages 661-673
Trojanowicz, M.A.;Pobozy, E.;Szpunar Lobinska, J.

Abstract: A POAS-4B photometric analyzer. (Poli-Service, Poland) was equipped with CQYP 41 (green and yellow), CQP 461 (red), CQYP 15 (IR) light-emitting diodes and a BPSP 34 photodiode (all UnitraCemi, Poland). The optical pathlength was 1.5 mm wide and 1.5 cm long. The output signal was recorded by means of a Radelkis OH-814/1 potentiometric recorder. The flow injection system (manifold illustrated) consisted of a PP2-15 multi-channel pump (Zalimp, Poland), a laboratory-built rotary injection valve and a manifold made from polypropylene tubing (i.d. 0.7 mm). This apparatus was used for determination of Al, NH3, Cl-, Cr(VI), total Fe, NO3-, phosphate, phenol, water hardness and urea. The conditions of each analytical procedure, i.e., injection volume, flow rates, coil length, diode used, composition of solution in each line, detection limit, upper limit of rectilinear response, coefficient of variation, sampling rate, absorption λmax of chromophore used, emission λmax of the diode used, and the loss in sensitivity caused by the application of apparatus described instead of a conventional spectrophotometer are tabulated. Procedural details are given and discussed for each species determined.
Aluminum Chromium(VI) Ammonia Chloride Iron Phosphate Phenol Urea Potentiometry

"Simultaneous Determination Of 2-deoxyglucoseSimultaneous Determination Of 2-deoxyglucose"
Chem. Pharm. Bull. 1990 Volume 38, Issue 4 Pages 963-965
Umegae, Y.;Nohta, H.;Ohkura, Y.

Abstract: Sample solution (0.1 ml) was injected on to a TSK gel Sugar AXG column (15 cm x 4.6 mm) operated at 60°C with 1 M borate buffer (pH 9.0) as mobile phase (0.4 mL min-1). The effluent was mixed with 15 mM meso-1,2-bis-(4-methoxyphenyl)ethylenediamine in aqueous 30% ethanol - 0.6 M NaOH (0.3 mL min-1) and passed through a reaction coil (20 m x 0.5 mm) at 140°C and a cooling coil (1 m x 0.5 mm), and the fluorescence was measured at 460 nm (excitation at 330 nm). Calibration graphs were rectilinear for up to 100 nmol injected, the detection limits for 2-deoxy-D-ribose, 2-deoxyglucose (I), rhamnose, L-fucose and glucose (II) were 21, 26, 27, 18 and 28 pmol, respectively, and the respective coefficient of variation (n = 10) at 1 nmol were 1.7, 1.5, 2.1, 1.5 and 1.9%. The method was applied to determine I and II in deproteinized serum, with L-fucose as internal standard.
Glucose 2-Deoxyglucose Serum Rat HPLC Fluorescence

"High-speed Flow Injection Determinations Of Oxidative Agents In Aqueous-solutions Based On Reaction With An Online Generated Leuco Dye"
Chem. Tech. 1990 Volume 42, Issue 7 Pages 304-307
MU&Ecirc;LLER H. ; HANSEN E. H.

Abstract: In a FIAstar 5020 automatic analyzer. (Tecator) with motor-driven injector loop (60 µL), streams (2 mL min-1) of aqueous thionine violet solution (0.2 mg mL-1) and of EDTA solution (3 g in 100 mL of water, diluted to 200 mL with acetate buffer of pH 4.7) were combined and passed through a glass reaction coil (1 m x 2 mm) under a 250-W high-pressure Hg lamp to reduce the dyestuff to its leuco form. Sample solution [e.g., Cr2O72-, Fe(CN)63-, VO3-, S2O82- or Fe3+] was injected into the stream, and the absorbance was measured at 600 nm in a Corning 252 flow-through photometer with a Hellma 178.012 QS flow-through cell (10 mm; 18 µL). Up to 180 samples h-1 can be analyzed. The limit of detection is ~1 µM. As H2O2 reacts only at concentration. of >10 to 100 mM, the determination of, e.g., 10 µM-S2O82- is possible in a 150-fold excess of H2O2.
Dichromate Ferricyanide Vanadate Persulfate Iron(III) Spectrophotometry

"Comparison Of The Limits Of Detection Obtained By Means Of A H.f. Plasma (ICP) Used As A Source Of Photons Or Ions In Elementary Analysis"
Chimia 1990 Volume 44, Issue 4 Pages 93-96
Poussel, Emmanuelle; Michel Mermet, Jean

Abstract: A discussion is presented of the fundamental principles, including instrumental design, which determine the limits of detection in ICP-AES and ICP-MS. The better sensitivity of ICP-MS for analysis of solution is less of an advantage in analysis of solids because of the greater dilution factor that may be required. Alternative methods of sample introduction, including flow injection, electrothermal vaporization and laser ablation, are considered. These developments and those in instrumental design will make ICP-MS a very powerful method for ultratrace analysis.
Spectrophotometry Mass spectrometry

"Reversed-phase Chromatographic Separation Of The Rare-earth Elements"
Chromatographia 1990 Volume 29, Issue 11-12 Pages 579-582
M. Adachi, K. Oguma and R. Kuroda

Abstract: Rare-earth metals (1 mM to 4 mM in 3 M HCl) were separated by HPLC on a column (15 cm x 4 mm) of Hitachi ODS (5 µm) with a mobile phase (1.0 mL min-1) of 0.05 M to 0.5 M lactic acid (gradient concentration.) containing 10 mM octanesulfonate and aqueous NH3 to pH 3.5. The eluate was derivatized post-column with 0.1 mM arsenazo III and detection was at 650 nm. Separation was completed within 40 min. Specimen chromatograms are presented; there was co-elution of Dy with Y and of Eu with Gd. Detection limits were down to ~ 10 ng injected.
Metals, rare earth Dysprosium Yttrium Europium Gadolinium HPLC Spectrophotometry

"Competitive Heterogeneous Enzyme Immunoassay For Theophylline By Flow Injection Analysis With Electrochemical Detection Of P-aminophenol"
Clin. Chem. 1990 Volume 36, Issue 4 Pages 662-665
EP Gil, HT Tang, HB Halsall, WR Heineman and AS Misiego

Abstract: A competitive enzyme-linked immunoabsorbent assay based on the flow injection amperometric detection of p-aminophenol has been investigated with use of the materials and general procedure of a commercial kit for the determination of theophylline in human serum. The antibody is immobilized on glass beads, and the enzyme label is alkaline phosphatase (EC 3.1.3.1). The high currents generated during the electrochemical detection allowed a rapid (35 min) and simple determination of theophylline throughout its therapeutic range (10-20 mg/L) and also in the subtherapeutic range (detection limit of about 80 µg/L).
Theophylline 4-Aminophenol Serum Human Immunoassay Amperometry Electrode Clinical analysis

"Heterogeneous Enzyme Immunoassay Of α-fetoprotein In Maternal Serum By Flow Injection Amperometric Detection Of 4-aminophenol"
Clin. Chem. 1990 Volume 36, Issue 11 Pages 1941-1944
Y Xu, B Halsall and WR Heineman

Abstract: A sandwich-type heterogeneous enzyme immunoassay with flow injection analysis for α-fetoprotein (AFP) in human serum has been developed. 4-Aminophenol, the product of enzymatic reaction, is detected amperometrically. The interassay CV for this electrochemical enzyme immunoassay was less than 8.2%, with a minimum detection limit for AFP of 0.163 µg/L. The calibration curve had a linear range of 0.316-100 µg/L. Studies with 48 human maternal serum samples, comparing results by this method with those by a commercial kit, showed a good correlation (r = 0.961). This procedure provides an alternative method for determining low concentrations of AFP in human maternal serum.
α-Fetoprotein 4-Aminophenol Serum Human Immunoassay Amperometry Clinical analysis

"Determination Of Ultratrace Amounts Of Selenium(IV) In Water And Soil Extracts By Flow Injection Online Ion-exchange Preconcentration Hydride Generation Atomic Absorption Spectrometry"
Kexue Tongbao 1990 Volume 35, Issue 6 Pages 526-527
XU SHU-KUN, ZHANG SU-CHUN, FANG ZHAO-LUN

Abstract: Sample solution (9 mL min-1) was merged with 0.2 M acetate buffer (pH 5; 0.5 mL min-1) before passing through a column (4.5 cm x 3 mm) of D201 macroporous anion exchanger (50 mesh). Selenium was eluted with 1 M HCl (6 mL min-1) and the eluate was mixed with 0.5% of NaBH4 in 0.1% NaOH solution (2 mL min-1). The SeH4 was separated in a gas - liquid separator and carried by Ar (150 mL min-1) to a silica atomizer heated at 700°C for determination by AAS at 196.0 nm. The detection limit was 2 ng l-1, and the sampling rate was 50 h-1. The coefficient of variation were 1.1% (n = 11) for 0.5 µg L-1 and 6.4% (n = 10) for 0.01 µg l-1. Recoveries from tap, well and mineral waters were 96 to 100% and from soil extracts were 92 to 102%.
Selenium(IV) Environmental Mineral Well Water Ion exchange Spectrophotometry Clinical analysis Sample preparation

"Determination Of Trace Amounts Of Arsenic By Flow Injection Analysis - Hydride Generation - Inductively Coupled Plasma Atomic-emission Spectroscopy"
Fenxi Ceshi Tongbao 1990 Volume 9, Issue 1 Pages 9-14
Chen Hao;Jiang Zucheng;Kong Linying;Zen Yun'e

Abstract: A double capillary nebulizer was used to generate the hydride of the analyte. Factors affecting line intensity in the flow injection system were investigated. The effects of several inorganic acids, their acidity and inter-element interference effects were examined. Under optimum conditions the detection limit of As was 5.2 mg mL-1; the coefficient of variation was 1.48% for 2 µg mL-1 (n = 10). Recoveries of Al from NaCl and AlCl3.xH2O were >95%.
Arsenic Spectrophotometry

"Determination Of Trace Silver With Catalytic Flow Injection Spectrophotometry"
Fenxi Ceshi Tongbao 1990 Volume 9, Issue 3 Pages 39-42
Yang Jiannan;Shi Naih;He Wanli

Abstract: A flow injection spectrophotometric method is described for the determination of trace Ag in wastewater based on the catalytic action of Ag(I) on the oxidation reaction of S2O82- in the presence of o-phenanthroline. Sample throughput is 70 h-1. The limit of detection is 5 ng mL-1 at room temperature Coefficients of variation were 5.78%.
Silver Waste

"Studies On Flow Injection Analysis Of Platinum Metals. 4. Iridium - Potassium Iodate - α-naphtholphthalein System"
Fenxi Huaxue 1990 Volume 18, Issue 3 Pages 237-239
He, X.;Cai, Y.;Hu, Z.D.

Abstract: Iridium catalyses the decoloration of α-naphtholphthalein by KIO4. Based on this reaction, a flow injection analysis method for determining Ir(IV) was developed. The reaction mixture comprised 10 mM KIO4, 0.3 mM α-naphtholphthalein, and Na2B4O7 - NaOH buffer solution (pH 10), at 80°C, and detection at 640 nm. The sampling rate was 61 h-1. The calibration graph was rectilinear for 0.05 to 0.40 µg mL-1 of Ir. The detection limit was 0.02 µg mL-1. The coefficient of variation for simulated samples were 1.0 to 1.3%.
Platinum(IV) Iridium(4+) Spectrophotometry

"Determination Of Trace Cobalt By Online FIA Ion-exchange Preconcentration AAS"
Fenxi Huaxue 1990 Volume 18, Issue 5 Pages 468-471
Xu, S.K.;Zhang, S.;Fang, Z.L.

Abstract: Water (pH 3 to 6) is injected into the online column pre-concentration FIA system (block diagram given) to undergo double-column parallel pre-concentration with 0.5 M ammonium acetate buffer (pH adjustable) as carrier (0.3 mL min-1), pre-column flow rate of 9 mL min-1 and 2 M HCl as eluent (5 mL min-1) followed by AAS analysis of the eluate. A multi-functional valve is used to control the various processes. Columns (45 x 3 mm) containing CPG-8HQ ion-exchanger, Chelex-100 and 501 resins are compared; optimum operating pHs are 7 to 8 for CPG-8 HQ and Chelex-100 and 9 to 10 for Chelex-501. When determining 100 µg L-1 of Co, recoveries are 96 to 106% (with exception of Chelex-501 in some cases). At 40 µg l-1, coefficient of variation (n = 11) is 1.7%. The detection limit is 0.2 µg l-1. There is no interference from up to 1000 ppm of Na and K (allowed amounts of other ions presented).
Cobalt Ion exchange Spectrophotometry

"Stopped-flow Catalytic Spectrophotometric Determination Of Trace Manganese"
Fenxi Huaxue 1990 Volume 18, Issue 11 Pages 1041-1043
Li, K.;Ren, Y.

Abstract: A flow injection analysis method is proposed (diagram given). Natural water, containing 180 ng of Mn, is mixed with 2 mL of 9 mM nitrilotriacetic acid solution (pH 3.8; I), 5 mL of 0.2 M Na acetate - acetic acid buffer (pH 3.8) and diluted with water to 25 mL. Three reagent streams of viz, 20 µM-Malachite green (C.I. Basic Green 4), 10 mM KIO4 and 10 mM I solution in buffer solution (pH 3.8), are pumped (2 mL min-1) into a reactor for 1 to 2 min with a stopped-flow time of 10 min. The mixture is mixed with a carrier stream of test solution (2 mL min-1) at 52°C in a 2-m coil with detection at 615 nm. The calibration graph was rectilinear for up to 7.2 ng mL-1 of Mn2+ and the detection limit was 0.07 ng mL-1. The coefficient of variation was 3.9%.
Manganese Environmental Spectrophotometry

"Study Of Flow Injection Analysis - Inductively Coupled Plasma Atomic-emission Spectrometry. 4. Rapid Method For The Determination Of Trace Scandium"
Fenxi Huaxue 1990 Volume 18, Issue 12 Pages 1152-1154
Chen, H.;Jiang, Z.C.;Lai, Z.;Liao, Z.H.

Abstract: Trace Sc in technological processing solution is determined by the cited method (details given) in the presence of matrix elements (30 mg mL-1 of Fe and 10 mg mL-1 of Ti). Interference from matrix elements is investigated, and conventional and flow injection analysis sample introduction methods are compared. For the injection of a 0.5 mL portion of sample solution with detection at 363.075 nm, the detection limit was 8.4 ng mL-1 of Sc and coefficient of variation (n = 12) were 2.5%.
Scandium Industrial Spectrophotometry

"Reverse Flow Injection Chemiluminescence Determination Of Glucose"
Fenxi Huaxue 1997 Volume 25, Issue 1 Pages 34-36
Huang, Y.W.;Feng, M.L.;Zhang, Z.J.

Abstract: Sample was injected via an FIA manifold into a stream of 0.08 M KOH and merged with 0.5 mM K7[Cu(IO6)]2 followed by mixing with 25 mM luminol in 0.1 M NaOH prior to measuring the chemiluminescence intensity. The calibration graph was linear from 0.4-80 ng/l glucose, with a detection limit of 0.18 ng/ml. the RSD was 2%. Cu(II), Co(II), ascorbic acid, uric acid, amines and proteins interfered.
Glucose Chemiluminescence

"Determination Of Cobalt(II) With Alizarin Violet Chemiluminescence System By Flow Injection Analysis"
Fenxi Shiyanshi 1989 Volume 8, Issue 2 Pages 27-29
Zhang Wumin, Zhong Shiming, Hu Hejin and Gong Jianyi

Abstract: Cobalt was determined by mixing the sample with 0.2 M NaOH, 1.25 mM hexadecylammonium bromide and alizarin violet in a flow injection system (diagram given) with chemiluminescence detection. The calibration graph was rectilinear from 0.02 to 60 µg L-1 of Co and the detection limit was 3.2 ng l-1. The coefficient of variation at 10 µg L-1 was 0.27%. The method can be applied to the determination of Co in hair.
Cobalt Hair Chemiluminescence

"Flow Injection Spectrophotometric Determination Of Trace Amounts Of Cobalt In Purified Zinc Electrolyte"
Fenxi Shiyanshi 1990 Volume 9, Issue 3 Pages 5-7
Li Wanchun and Fu Bin

Abstract: Purified Zn electrolyte was mixed with 5% Na acetate solution, injected into a carrier stream of water to react with 0.03% 5-Cl-PADAB [4-(5-chloro-2-pyridylazo]-m-phenylenediamine] and combined with 2.5% H2SO4 from two emerging zones before spectrophotometric detection of the red complex at 570 nm. The coefficient of variation was 2% for 2 µg mL-1 of Co; detection limit was 0.14 µg mL-1. Interference from Zn was eliminated by matrix matching. Results agreed well with those obtained by nitroso-R salt spectrophotometry.
Cobalt Zinc Spectrophotometry

"Determination Of Micro-amounts Of Beryllium By Direct Spectrophotometry And Flow Injection Analysis"
Fenxi Shiyanshi 1990 Volume 9, Issue 6 Pages 28-30
Chen Xingguo, Xu Yanjun and Hu Zhide

Abstract: Beryllium bronze (0.2 g) was digested by heating with concentrated HNO3 or HCl - H2O2 and the digest was heated to remove HNO3 or H2O2, cooled and diluted to 100 mL with water. A 1 mL portion of the solution was mixed with 1 mL of 0.5 M KI and 2 mL of 4% ascorbic acid solution and the mixture was centrifuged. The supernatant solution was diluted to 50 mL with water. For direct spectrophotometric determination of Be, a portion of the sample solution was mixed with 2.5 mL of aqueous 0.1% eriochrome cyanine R (C.I. Mordant Blue 3) solution, 5 mL of ammonium acetate buffer (pH 7), 1.5 mL of aqueous 1% phosphatidylcholine solution and water to 25 mL and, after 30 min, the absorbance was measured at 608 nm (ε =80,000) vs. a reagent blank. Beer's law was obeyed from 20 to 80 ng mL-1 of Be and recoveries were 92 to 104%. For flow injection analysis, a Teactor FIA 5020 Analyser and a spectrophotometric detection system were used. The calibration graph was rectilinear from 0.04 to 2 µg mL-1 of Be and the detection limit was 20 ng mL-1. The coefficient of variation was 1% and recoveries were from 97 to 105%. Tolerance limits of foreign ions are listed.
Beryllium Spectrophotometry

"Application Of 4-aminohippuric Acid Chlorophosphonazo In Determination Of Palladium(II) By Spectrophotometry And Flow Injection Analysis"
Huaxue Shiji 1990 Volume 12, Issue 1 Pages 12-14
Chen Xingguo Xu Yanjun Liu Mancang Hu Zhide

Abstract: Ore (0.2 g) is dissolved in 10 mL of aqua regia, evaporated to near dryness and further evaporated to near dryness with 2 mL of HCl prior to dilution with 10% HCl to 10 mL. For direct spectrophotometric determination, an aliquot of the solution is treated with 5 mL of 12N-H2SO4, 0.5 mL of 1 mM cited compound (N- 4-[7-(4-chloro-2-phosphophenylazo)-1,8-dihydroxy-3,6-disulfo-2-naphthylazo]benzoyl glycine; I) followed by heating in a boiling-water bath for 5 min, dilution to volume and measurement of absorbance at 631 nm (ε = 37,000) vs. a reagent blank. Beer's law is obeyed for 3 to 20 µg of Pd(II) in 25 mL of final solution For flow injection analysis, 100 µL of the solution is applied to the apparatus (diagram given) and flows to the reactor coil (at 90°C) with a stream of 2% H2SO4 to mix with 80 µM-I and then 5N-H2SO4 before measurement of absorbance at 631 nm; the sampling rate is 60 samples h-1. The calibration graph is rectilinear for 0.25 to 1.25 µg of Pd in 1 mL of solution The detection limit is 0.15 µg mL-1 and the coefficient of variation is 1% for 1 µg mL-1 of Pd. Interferences of 9 foreign ions in both methods have been studied.
Palladium(II) Geological Sample preparation Spectrophotometry

"Flow Injection Spectrophotometric Determination Of Ultra Trace Amounts Of Selenium(IV)"
Indian J. Chem. A 1997 Volume 36, Issue 1 Pages 105-107
ENSAFI A.A

Abstract: A schematic diagram of the FIA system is presented. Sample (250 µL) was injected into a water carrier and merged with 0.32 mM gallocyanine buffered at pH 7 by phosphate and 0.55 mM sulfide solution containing barium disodium EDTA. All reagents were pumped at 0.5 ml/min. The solutions were mixed in a 200 cm reaction coil and the decrease in absorbance of gallocyanine as a result of its catalytic (Se) reduction by sulfide was measured at 620 nm. The decrease in gallocyanine absorbance was proportional to the Se(IV) concentration from 2.5-500 ng/ml and the detection limit was 1 ng/ml. The RSD (n = 10) was 1.5% for 50 ng/ml of Se(IV). The method was applied to ores, personal care products and water. The interference effects of various ions on the determination were investigated.
Selenium(IV) Geological Commercial product Environmental Spectrophotometry

"Spectrophotometric Flow Injection Determination Of Thiocyanate"
Indian J. Chem. A 1997 Volume 36, Issue 4 Pages 344-346
ENSAFI A.A.

Abstract: The determination was performed using a previously described flow injection system (Ensafi, Ibid., 1997, 36, 105). The following optimum conditions were used: 0.4 M sodium azide; 0.175 mM iodine solution (prepared by dissolving I2 in KI solution); and a pH of 5. Sodium azide solution, phosphate buffer, iodine solution and water were pumped at a flow rate of 30 ml/h. A portion (300 µL) of thiocyanate solution was injected and the absorbance was read at 349 nm after reaction in a 300 cm mixing coil at 25°C. The calibration graph was linear from 0.005-1.8 µg/ml and the limit of detection was 0.62 ng/ml. The RSD (n = 10) was 1.3% and the sample throughput was ~40/h. The method was applied to the determination of thiocyanate in waste water and urine. An interference study is described.
Thiocyanate ion Urine Waste Spectrophotometry

"Flow Injection Methods For Monitoring The Environment"
Indian J. Environ. Prot. 1989 Volume 9, Issue 6 Pages 412-419
Mahadevappa, D. S.

Abstract: Flow injection analysis methods are presented for determination of S2- in solution, residual Cl in solution, and aromatic sulfonylhaloamines (e.g., chloramine-T and chloramine-B) and Fe(III) based on previously reported spectrophotometric methods. Optimum conditions for all the determinations are described. The detection limits were 0.14 to 1.4 ppm and max. sampling rates were >200 samples h-1. Beer's law ranges and tolerance limits for diverse ions are reported. At pH 4.0, Fe (23.4 ppm) was determined in the presence of 120 ppm of Fe by using the reaction with sulfosalicylic acid. Chlorine in seawater samples and iron in steel were determined by the described methods.
Chloramine T Chloramine, B Sulfide Chlorine Iron Sea Alloy Spectrophotometry

"Analysis Of Aflatoxins (B1, B2, G1 And G2) In Rodent Feed By HPLC Using Post-column Derivatization And Fluorescence Detection"
J. Agric. Food Chem. 1991 Volume 39, Issue 1 Pages 137-140
Manuel Holcomb and Harold C. Thompson

Abstract: To the feed sample (50 g), NaCl (5 g) was added and the mixture was extracted with 70% methanol. A diluted portion of the filtered extract was purified on an Aflatest P monoclonal antibody affinity column. After washing with water, the aflatoxins were eluted with methanol. A portion (50 µL) was analyzed by HPLC on a Supelco reversed phase C18 column (25 cm x 4.6 mm) equipped with a guard column; water - methanol - acetonitrile (5:4:1) was used as mobile phase (0.8 mL min-1). Post-column derivatization was effected by reaction with a stream of 0.2% iodine solution; the reactor coil was heated to 68°C. Fluorescence detection at 440 nm with excitation at 365 nm was used. Response was rectilinear up to 1 ng of injected analyte for aflatoxins B1, B2 and G1 and up to 0.5 ng for G2. Detection limits were 0.25 ppb for B1, B2 and G1 and 0.12 ppb for G2.
Aflatoxin B1 Aflatoxin B2 Aflatoxin G1 Aflatoxin G2 Feed HPLC Fluorescence

"Ion-exchange Chromatographic Determination Of Hypoglycine A In Canned Ackee Fruit"
J. AOAC Int. 1989 Volume 72, Issue 2 Pages 374-377
Chase, G.W.;Landen, W.O.;Gelbaum, L.T.;Soliman, A.G.M.

Abstract: Canned ackee fruit were drained from the liquid medium and homogenized with aqueous 80% ethanol, the homogenate was centrifuged and the supernatant solution was mixed with trichloroacetic acid. The mixture was filtered and a 15 µL portion was analyzed on a Waters automatic amino-acid analyzer. fitted with a No. 80002 ion-exchange column (25 cm x 4.6 mm) operated at 62°C with Na acetate buffer solution (pH 7.4) - Na citrate buffer solution (pH 3.15) (7:3) as mobile phase (0.4 mL min-1) and post-column derivatization with ninhydrin at 120°C for detection at 436 and 546 nm. Calibration graphs were rectilinear from 4.8 (detection limit) to 73 µg mL-1 of hypoglycine A in the final solution Recoveries of standard additions to the fruit and liquid medium (analyzed similarly) were 103 and 102%, respectively.
Hypoglycine A Fruit HPIC Spectrophotometry

"Liquid Chromatographic Method For Quantitation Of Glyphosate And Metabolite Residues In Organic And Mineral Soils, Stream Sediments And Hardwood Foliage"
J. AOAC Int. 1989 Volume 72, Issue 2 Pages 355-360
Thompson DG, Cowell JE, Daniels RJ, Staznik B, MacDonald LM

Abstract: Soil, sediment, foliage and deposit collectors (polyethylene sheets) were extracted with aqueous 0.5 M NH3 and the extract was applied to an AG 1-X8 anion-exchange column, with elution with 0.5 M NH4HCO3. After removal of bicarbonate by repeated evaporation and dissolution in water, further cleanup was effected on a Dowex 50W-X8 cation-exchange column. The aqueous eluate was evaporated to dryness and the residue was dissolved in 5 mM KH2PO4 for HPLC on a column (10 cm x 4.6 mm) of Aminex A-9 equipped with a guard column of the same material and operated at 50°C with 5 mM KH2PO4 (pH 1.9) buffer in aqueous 4% methanol as mobile phase (0.5 mL min-1). After post-column derivatization with ninhydrin at 100°C, glyphosate (I) and its metabolite aminomethylphosphonic acid (II) were detected at 570 nm. Calibration graphs were rectilinear for 0.05 to 3.0 µg of I and 12.5 to 750 ng of II, and detection limits ranged from 0.01 to 0.1 µg g-1.
Glyphosate Environmental River Plant LC Sample preparation

"Continuous-flow Vapor Generation For Inductively Coupled Argon Plasma Spectrometric Analysis. 1. Selenium"
J. AOAC Int. 1990 Volume 73, Issue 3 Pages 404-410
Tracy ML, M&ouml;ller G.

Abstract: Sample (~1.5 g of solid or ~10 mL of liquid) is wet ashed with HNO3, H2SO4 and HClO4 at ~310°C; details are presented for treatment of different samples. The digest is cooled to room temp., 5 M HCl is added and the solution is diluted. In a simple continuous-flow manifold, sample solution is mixed with 12 M HCl and then 0.6% NaBH4 solution The H2Se produced is separated off by a standard pneumatic neublizer, and Se is determined by ICP-AES at 196.090 nm. The detection limit is 0.4 µg l-1, or 4 µg kg-1 for a nominal 1-g sample. The calibration graph is rectilinear for 4 mg kg-1. The method has been applied to biological tissues and fluids and to water. Results show good agreement with those by AAS and NAA.
Selenium Biological tissue Water Spectrophotometry

"Slurries Introduction In Flow Injection Atomic Absorption Spectroscopic Analysis Of Sewage Sludges"
J. AOAC Int. 1990 Volume 73, Issue 3 Pages 389-393
Martinez-Avila, R.; Carbonell, V.; Guardia, M. de la; Salvador, A

Abstract: The effects were studied of flow injection parameters on the determination of Cu, Mn and Pb in sewage sludge, by injection of a sample into a carrier stream and detection by air - acetylene flame AAS. Samples were pre-digested with HNO3 with heating in a microwave oven. AAS instrumental parameters are given for each metal. The limits of detection were 0.06, 0.05 and 0.3 ppm, respectively, which are adequate for analysis of real samples. The method was applied to two reference materials; accuracy was better than that obtained by continuous aspiration.
Copper Manganese Lead Sludge Spectrophotometry Sample preparation

"Design And Operation Of An Autosampler-controlled Flow Injection Preconcentration System For Lead Determination By Flame Atomic Absorption Spectrometry"
J. Autom. Methods Manag. Chem. 1989 Volume 11, Issue 1 Pages 36-39
S. R. BYSOUTH, J. F. TYSON, and P. B. STOCKWELL

Abstract: The design and operation of simple flow injection manifolds for the pre-concentration. of Pb are described. The manifolds make use of glass columns (4 cm x 2.5 mm) contained within the sample loop of an injection valve, and the valves and pump of the system are controlled by an autosampler via an interface. The effects were studied of sample flow rate, pre-concentration buffer type and pH, and optimum eluent concentration. and flow rate. Detection limits ranged from 2.8 to 1.4 ng mL-1, representing an improvement in sensitivity of ~50 times that obtained by manual methods.
Lead Spectrophotometry

"Simple Flow Injection Method For The Determination Of Blood Glucose Using A Technicon Immobilized-enzyme Coil"
J. Autom. Methods Manag. Chem. 1989 Volume 11, Issue 2 Pages 87-88
SVEINBJ&Ouml;RN GIZURARSON

Abstract: Sample solution was injected into the carrier solution [55.46 mM PIPES - 2.63 mM MgCl2 - 0.015% Brij 35 - 0.8 mM ATP - 1.1 mM NAD+], which then passed to the Technicon enzyme coil on which hexokinase and glucose-6-phosphate dehydrogenase were immobilized. The solution then passed to the detector for detection of glucose at 340 nm. The calibration graph was rectilinear for up to 3.3 mM glucose and the detection limit was 0.1 mM. The mean coefficient of variation was 1.5%.
Glucose Blood Spectrophotometry

"Evaluation Of The Jokoo-ION 150AC: Guidelines For The Evaluation Of Analysers By Ion-selective Electrodes"
J. Autom. Methods Manag. Chem. 1990 Volume 12, Issue 3 Pages 116-128
JOAN FARR&Eacute;, CARMEN BIOSCA, and ROM&Aacute;N GALIMANY

Abstract: Details are given of the cited automated analyzer. for Na, K and Cl- which incorporates ion-selective electrodes and is applied to blood, serum or diluted urine. The unit has a Ag - AgCl (saturated KCl) reference electrode, a glass membrane electrode for Na, a liquid membrane electrode based on valinomycin with PVC as support for K, and, for Cl-, a liquid membrane electrode based on ion exchange involving quaternary ammonium salts in a polymeric solvent. The unit was evaluated by comparison with a SMAC II (Technicon) continuous-flow analyzer. and an IL 943 flame photometer (Instrumentation Laboratory), and gave acceptable performance in terms of detection limits, linearity, drift and carry-over. The electrode slope, electrode response, sample temperature and pH effects, effects of high concentration. of proteins or lipids, and influence of haematocrit on the Na, K and Cl- concentration. were also evaluated. The strategy is generally applicable to ion-selective electrode analyzer.s.
Sodium Potassium Chloride Blood Blood Serum Urine Electrode Electrode Electrode Electrode Electrode

"Continuous-flow Bioluminescent Determination Of ATP In Platelets Using Firefly Luciferase Immobilized On Epoxy Methacrylate"
J. Biolumin. Chemilumin. 1989 Volume 3, Issue 1 Pages 7-11
Giacomo Carrea, Roberto Bovara, Stefano Girotti, Elida Ferri, Severino Ghini, Aldo Roda

Abstract: Plasma was centrifuged, and the supernatant solution was diluted to give 105 platelets mL-1, and then diluted (1:200) with 0.1 mM Tris buffer of pH 8.5 containing 4 mM EDTA and 0.2% of Triton X-100 to release the ATP. Glass columns (3 cm x 2 mm) containing Eupergit C(Sigma)-immobilized firefly luciferase were placed in a luminometer (LKB 1250) in front of the photomultiplier window and Affi-Sep cartridges were inserted directly into the instrument. The manifold was similar to that described earlier (Anal. Chem., 1986, 58, 331), and involved two reagent streams. The first consisted of a bioluminescent solution of 0.02 M Tris - acetate buffer solution of pH 7.75, containing 0.12 mM luciferin, 5 mM Mg2+, 0.1 mM EDTA and 1 mM dithiothreitol; the second stream was a continuous-flow of air, to which a known volume (5 to 50 µL) of sample was intermittently added. The limit of detection was 0.3 pmol of ATP and response was rectilinear between 1 and 500 pmol of ATP. Intra- and inter-assay coefficient of variation were 7.1 (n = 10) and 9.6% (n = 7), respectively. Results correlated well with those obtained by using soluble luciferase (r = 0.99).
Blood Plasma Bioluminescence

"Bioluminescent Flow Sensors: L-lactate Dehydrogenase Activity Determination In Serum"
J. Biolumin. Chemilumin. 1989 Volume 3, Issue 2 Pages 41-45
Stefano Girotti, Cinzia Bassoli, Maria Loredana Cascione, Severino Ghini, Giacomo Carrea, Roberto Bovara, Aldo Roda, Roberto Motta, Roberto Petilino

Abstract: Alkanal monooxygenase (FMN-linked) and NAD(P)H dehydrogenase (FMN) were co-immobilized on a nylon coil (1 mm i.d.) activated with triethyloxonium fluoriborate and glutaraldehyde (Anal. Chim. Acta., 1988, 205, 229). In the flow injection system illustrated, the air-segmented sample was mixed with a solution containing NAD+, KCl and lactic acid in 0.01 M pyrophosphate buffer of pH 8.4, and the resulting solution was mixed with 0.1 M potassium phosphate buffer (pH 6.9) containing flavine mononucleotide, decanal and dithiothreitol before passage through the enzyme coil. The generated luminescence was measured with the photomultiplier tube of an LKB Wallac model 1250 luminometer. Enzymic reaction took 30 s at 37°C or 1 min at 25°C. Serum was diluted 10- or 20-fold with 0.02 M pyrophosphate buffer of pH 8.4 before analysis. The detection limit was 0.5 iu L-1 of lactate dehydrogenase with a sample injection of 25 µL, and at 25°C response was rectilinear from 3 to 2000 iu l-1. The within- and between-day reproducibility at 151 iu L-1 was 6.7 and 8.8%, respectively, and recovery was >92%.
Enzyme, lactate dehydrogenase Blood Serum Sensor Bioluminescence

"Chemiluminescent Assay Of Co-factors"
J. Biolumin. Chemilumin. 1989 Volume 4, Issue 1 Pages 454-462
Akio Tsuji, Masako Maeda, Hidetoshi Arakawa

Abstract: NADH was determined with use of isoluminol and microperoxidase with 1-methoxy-5-methylphenazium methyl sulfate as the electron mediator. The sensitivity was increased by coupling the chemiluminescent reaction with an enzyme cycling system with alcohol dehydrogenase and malate dehydrogenase as cycling enzymes, ethanol and oxaloacetate as substrates and aspartate aminotransferase and glutamate. The calibration graph was rectilinear from 30 to 500 fmol of NADH per assay with coefficient of variation of 2.1 to 10.5%. The method was applied as a detection system for the determination of bile acids by HPLC and bile acids and glucose (I) by flow injection analysis. By flow injection analysis the calibrations graphs were rectilinear from 5 to 100 pM-deoxycholic acid and 0.5 to 5 nmol per assay of I. Results correlated well (r = 0.986 and 0.975) with those by alternative methods. The method was also applied in the determination of ATP by two methods. In the preferred method, hexokinase and pyruvate kinase were used as cycling enzymes. The glucose 6-phosphate produced reacted with NADP+ in the presence of glucose-6-phospahte dehydrogenase to produce NADPH which was determined chemiluminometrically. The detection limit was 10 fmol of ATP per assay.
HPLC Chemiluminescence

"A Flow Injection Analysis System Involving Immobilized NADH Oxidase In Column Form For Clinical Analysis"
J. Biotechnol. 1990 Volume 14, Issue 1 Pages 33-41
Takashi Murachi*, Masayuki Totani, Masaki Ikemoto and Masayoshi Tabata

Abstract: A highly sensitive FIA system for chemiluminometric determination of reduced coenzyme, NADH, was developed, using immobilized NADH oxidase from Brevibacterium ammoniagenes. The enzyme catalyzed the oxidation of NADH generating hydrogen peroxide which emitted chemiluminescence when mixed with luminol and potassium ferricyanide. The immobilized enzyme reactor was a mini-column, measuring 1 or 2 mm in inner diameter and 20 mm in length, and the sample volume was only 1 µL per assay, with a feeding speed of one sample per min and a lowest detection limit of 10 pmol NADH. A FIA system was also developed for the determination of magnesium in human serum, using an enzyme column reactor with simultaneously coimmobilized hexokinase, D-glucose-6-phosphate dehydrogenase, and NADH oxidase. The performance of the system was as satisfactory as a routine colorimetric assay, but with much higher sensitivity. A flow injection analysis (FIA) system is described for the determination of NADH with a detection limit of 10 pmol. Samples (1 µL) were passed through a mini-column (2 cm x 2 mm) containing immobilized NADH oxidase and the H2O2 generated was determined by a chemiluminometric method using luminol and potassium ferricyanide. A FIA system was also developed for the determination of Mg in human serum using a reactor with co-immobilized hexokinase, D-glucose-6-phosphate dehydrogenase and NADH oxidase. The sensitivity was higher than that for the colorimetric assay using Xylidyl Blue.
Magnesium Nicotinamide adenine dinucleotide oxidized Serum Human Chemiluminescence Clinical analysis

"Development Of A FIA System With Immobilized Enzymes For Specific Post-column Detection Of Purine Bases And Their Nucleosides Separated By HPLC Column"
J. Biotechnol. 1990 Volume 14, Issue 1 Pages 89-97
Toshio Yao*, Yoshihiro Matsumoto and Tamotsu Wasa

Abstract: A sensitive and highly selective method for the simultaneous determination of purine bases and their nucleosides is proposed. An amperometric flow injection system with the two immobilized enzyme reactors (guanase immobilized reactor and purine nucleoside phosphorylase/xanthine oxidase co-immobilized reactor) is used as the specific post-column detection system of HPLC, to convert compounds separated by a reversed-phase. HPLC column to electroactive species (hydrogen peroxide and uric acid) which can be detected at a flow-through platinum electrode. The proposed detection system is specific for a group of purine bases and purine nucleosides and does not respond for purine nucleotides and pyrimidine bases. The linear determination ranges are from 10 pmol to 5 nmol for four purine bases (hypoxanthine, xanthine, guanine, and adenine) and four purine nucleosides (inosine, xanthosine, guanosine, and adenosine). The detection limits are 1.2-5.5 pmol. Samples were separated by HPLC on a column (25 cm x 4.6 mm) of ODS-A operated at 40°C with a mobile phase (1 mL min-1) of 0.05 M ammonium phosphate buffer solution (pH 2.5). The eluate was mixed with 0.3 M Na2PO4 buffer solution of pH 7.5 (0.5 mL min-) and the mixture was passed through a reactor containing co-immobilized nucleoside phosphorylase - xanthine oxidase. The resulting H2O2 was monitored amperometrically at 0.5 V vs. Ag - AgCl. Calibration graphs were rectilinear form 10 pmol to 5 nmol for the purine bases and purine nucleosides studied and the detection limits were 1.2 to 5.5 pmol. Coefficients of variation (n = 5) were 2.1 to 6.8% for 0.5 nmol of base or nucleoside.
Hypoxanthine Xanthine Guanine Adenine Inosine Xanthosine Guanosine Adenosine HPLC Amperometry Electrode Electrode

"Monitoring Of Enzymes During Chromatographic Separations"
J. Biotechnol. 1990 Volume 14, Issue 1 Pages 99-114
Wolfgang W. Stamm and Maria-Regina Kula*

Abstract: An online enzyme assay is presented based on flow injection techniques combined with fluorimetric detection. It allows to monitor NAD-dependent oxidoreductases during the purification of microbial crude extracts or partially purified enzymes by fast protein liquid chromatography (FPLC) in a near real-time mode. The arrangement is simple and can be easily integrated in the chromatographic system avoiding dead volumes. A high measuring frequency (up to 180 samples h-1) and a short response time (10-30 s) are achieved. The method has a low limit of detection (approximately 0.01 U mL-1), and a good reproducibility (1-4%), the injected sample volume is only 2 µL. Microbial alanine dehydrogenase, phenylalanine dehydrogenase and formate dehydrogenase were purified using fast protein liquid chromatography (Pharmacia LKB). Eluates passed through a UV detector then flow injection analysis (FIA) valve (Cheminert U Auto CSV-2) before collecting as fractions. At timed intervals 2 µL of sample was injected into the reagent mixture composed of buffer solution, substrate, and NAD coenzyme. The resulting NADH was estimated in the flow cell of an HPLC fluorescence detector at 460 nm (excitation at 340 nm). Sample throughput was 180 h-1, the limit of detection was 0.007 to 0.1 U mL-1 and the coefficient of variation (n = 13) was 1.0 to 1.4%.
Enzymes HPLC Fluorescence

"An Automated Spectrophotometric Flow Injection Procedure For The Determination Of Cellulase Activity In Bioreactor Preparations"
J. Biotechnol. 1990 Volume 14, Issue 1 Pages 81-87
P. J. Worsfold*,*, I. R. C. Whiteside, H. F. Pfeiffer and H. Waldhoff

Abstract: Sample (0.6 mL min-1) was injected through a rotary valve into a carrier stream of 0.05 M acetate buffer solution of pH 5 (0.2 mL min-1) until the sample loop (3900 µL) was filled. The loop contained two knitted reactor coils of 200 cm and 300 cm maintained at 50°C. Substrate solution (920 µL ) of 4% Na carboxymethyl cellulose in acetate buffer solution was injected through a second valve, 16 s after which the sample pump was turned off. After incubation the reducing sugar product was reacted with aqueous 5% p-amino-benzoylhydrazide in another reactor coil at 76°C. and the absorbance of the derivative was measured at 410 nm. The calibration graphs were rectilinear up to 0.56 U mL-1 of cellulase with a detection limit of 0.1 U mL-1. Sample throughput was 5 h-1. The method is applicable to other carbohydrases acting on soluble substrates and producing reducing sugars, e.g. amylase, dextranase, xylanase, glucanase, polygalacturonase. A spectrophotometric procedure for the determination of cellulase activity in precipitated bioreactor preparations and culture filtrates is described. It is based on the determination of reducing sugar produced by the action of the enzyme on carboxymethylcellulose. The reducing sugar is derivatized with p-aminobenzoyl-hydrazide and permits a limit of detection of 0.1 U mL-1 cellulase in the presence of background sugar, with a sampling rate of 5 h-1. The method can readily be applied to the determination of any carbohydrase acting on soluble substrates and producing reducing sugars, e.g. amylase, dextranase, xylanase, glucanase and polygalacturonase.
Enzyme, cellulase Spectrophotometry

"Autocatalysis In The Spectrophotometric Flow Injection Determination Of Manganese As Permanganate. Soil, Plant And Rock Analysis"
J. Braz. Chem. Soc. 1990 Volume 1, Issue 1 Pages 28-34
M. Mesquita, A O Jacintho, E. A G. Zagatto and R. F. Antonio

Abstract: Periodate oxidation was carried out under acidic conditions at ~95°C. The reaction rate was accelerated by exploiting the autocatalytic effect which was enhanced with addition of a permanganate confluent stream. Reagent concentration, permanganate addition, level, acidity, flow rates, color stability and interference effects were studied. Hydrochloric acid was tolerated up to 0.5M. Detection limit was ~0.3 mg L-1 Mn. Analysis time was 60 h-1. Results agreed well with those obtained by AES.
Manganese Permanganate Plant Environmental Geological Spectrophotometry

"Amperometric Bi-enzyme Based Biosensor For The Detection Of Lactose - Characterization And Application"
J. Chem. Technol. Biotechnol. 1990 Volume 49, Issue 3 Pages 255-265
Dorothea Pfeiffer, Edmundas V. Ralis, Alexander Makower, Frieder W. Scheller

Abstract: A 50 µL portion of 5% gelatin solution was mixed with β-galactosidase (I) from Escherichia coli (10.0 iu), Bifidobacterium adolescentes (4.0 iu) and Curvularia inaequalis (10.0 iu) and spread on 1 cm2 of polyethylene support (cf. Scheller et al., DD Patent 150 500, 1979). Additionally, cross-linking using polyvinylisocyanate (40 mL of 5% solution cm-2) was used (cf. Nentwig et al. DD Patent 277 888 4, 1985). The bi-enzyme membrane, obtained by combining a commercial glucose oxidase layer with a I layer between two cellulose membranes, was used to cover Clark-type electrodes which were then used manually or in a continuous-flow system at +600 mV vs. Ag - AgCl. The electrode was used to determine lactose (II) in milk, whey, baby foods, cottage cheese and bovine urine. The calibration graph was rectilinear for 25 mM II; the detection limit was 20 µM. In the analysis of milk, the coefficient of variation (n = 20) was 2%. Results compared well with those obtained by IR spectroscopy and photometry.
Lactose Milk Food Cottage Urine Amperometry Electrode Sensor

"Comparison Of Two Enzyme Sequences For A Novel L-malate Biosensor"
J. Chem. Technol. Biotechnol. 1997 Volume 68, Issue 1 Pages 31-36
Nenad Gajovic*, Axel Warsinke, Frieder W. Scheller

Abstract: Two novel amperometric biosensors for the determination of L-malic acid in food samples have been compared. Both sensors make use of a Clark-type O-2-electrode but differ in the enzymes used. The first sensor is composed of malate dehydrogenase (decarboxylating), also known as 'malic enzyme' (MDH(dec.), EC 1.1.1.40) and pyruvate oxidase (POP, EC 1.2.3.3). It covers a linear detection range from 1 µmol L-1 to 0.9 mmol L-1 L-malate, with a response time of 1.5 min (t(90)) and a relative standard deviation of 3.5%. Measurements with real samples offered a good correlation with the standard enzymatic assay (difference±7%) Stored at room temperature, the response of the sensor is constant for 8 days. The second biosensor is based on the three enzyme sequence malate dehydrogenase (MDH, EC 1.1.1.37), oxaloacetate decarboxylase (OAC, EC 4.1.1.3) and pyruvate oxidase (POP, EC 1.2.3.3). It has a non-linear calibration curve. Concentrations from 5 µmol L-1 to 1 mmol L-1 L-malate can be detected, within a response time of 1.5 min and with a relative standard deviation of 20%. The lower detection limit for L-malate is 2 µmol L-1. The response is constant for 10 days when the sensor is stored at room temperature. 11 References
l-Malate Food Potentiometry Electrode Sensor

"HPLC Analysis Of An Amino Bisphosphonate In Pharmaceutical Formulations Using Post-column Derivatization And Fluorescence Detection"
J. Chromatogr. Sci. 1990 Volume 28, Issue 11 Pages 563-566
Kwong, E.;Chiu, A.M.Y.;McClintock, S.A.;Cotton, M.L.

Abstract: Monosodium 4-amino-1-hydroxybutane-1,1-diphosphonic acid (MK 217) (in tablets or solution) was diluted or extracted with water and injected into an IONPAC NS1 5 µm column (Dionex) which was packed with a neutral macroporous resin that was stable over the entire pH range. The mobile phase (1 mL min-1) was 10 mM phosphate buffer (pH 8.0) - acetonitrile (3:2) containing 10 mM cetyltrimethylammonium bromide, with post-column derivatization (with o-phthalaldehyde and mercaptoethanol) and fluorimetric detection. The calibration graphs were rectilinear from 0.1 to 10 µg mL-1 and 10 µg mL-1 to 1 mg mL-1 with a detection limit of 100 ng. Within-day and between-day coefficient of variation at the 5 µg mL-1 level were 2% and 7%, respectively.
Monosodium 4-amino-1-hydroxybutane-1,1-diphosphonic acid Pharmaceutical HPLC Fluorescence

"Determination Of Some β-endorphin Fragments In Human Plasma By High Performance Liquid Chromatography With Laser-induced Fluorescence Detection"
J. Controlled Release 1990 Volume 13, Issue 2 Pages 129-139
C. M. B. van den Beld**, U. R. Tjaden*, N. J. Reinhoud, D. S. Stegehuis and J. van der Greef

Abstract: Plasma was deproteinized with trichloroacetic acid and applied to a column of Sephadex G-50. The appropriate fraction was concentrated on to a pre-column of Amberlite XAD-2 before analysis by HPLC on a column (10 cm x 3 mm) of C18 material with a mobile phase (0.75 mL min-1) of 0.01 M Na phosphate buffer (pH 2.4) - acetonitrile - 21.5 mM Na 1-octanesulfonate (763:232:5). The eluate was derivatized with 1.65 mM o-phthaldialdehyde - 9.25 mM 2-mercaptoethanol in 0.05 M borate buffer solution (pH 9.4) for 10 s before laser-induced fluorescence detection at 450 or 515 nm (excitation at 351.1, 363.8 or 488 nm). The calibration graph was rectilinear for 1 to 100 ng of des-enkephaline-γ-endorphin; the limit of detection was 0.4 ng mL-1. The method was more senstive than a method involving pre-column derviatization with fluorescein-5-isothiocyanate (described).
β-Endorphin (6-17) Plasma Human HPLC Fluorescence

"Simultaneous Determination Of Adenosine 5'-triphosphate And Glucose-6-phosphate Using A Flow Injection System With Immobilized Enzymes"
J. Flow Injection Anal. 1989 Volume 6, Issue 1 Pages 37-43
Toshio Yao, Yoshihiro Matsumoto-, and Tamotsu Wasa

Abstract: The immobilized enzyme reactors are prepared from 10 µm Lichrosorb-NH2 and hexokinase (I; 300 units) and glucose-6-phosphate dehydrogenase (II; 1000 units) in stainless-steel columns (12 or 5 mm x 4 mm, respectively), and installed into a flow system (diagram given). The sample (10 µL) is transported with a carrier stream of 0.05 M Tris - HCl buffer (pH 8) containing 0.1 mM NAD+, 2 mM D-glucose, 3 mM MgCl2 and 0.1 M NaCl (at 2 mL min-1) through a 3-way catch and split so that part of the reaction mixture flows through reactors II and I in series, and part of the mixture flows through reactor I only; galvanometric measurement is carried out with use of a vitreous-carbon electrode vs. Ag - AgCl. Separate peaks are obtained for glucose 6-phosphate (III) and III plus ATP. Calibration graphs are rectilinear from 0.01 to 4 mM for III and III plus ATP, with coefficient of variation of 2%. Detection limits for III and ATP are 1.2 and 2.3 µM, respectively.
Electrode Galvanometry

"Sensitive, Rapid And Precise Determination Of L-glutamic Acid In Cheese Using A Flow Injection System With Immobilized Enzyme Column"
J. Food Sci. 1989 Volume 54, Issue 2 Pages 423-426
Puchades, R.;Lemieux, L.;Simard, R.E.

Abstract: Glutamic acid in cheese was determined by its reaction in a packed-bed enzyme reactor containing immobilized glutamate dehydrogenase (GIDH) in a flow injection system, measuring fluorescence of NADH generated. There was a linear relationship (r = 0.999) between logpeak height and log-glumatic acid concentration (0.01 to 0.5 mM). The detection limit was 0.005 mM for an injection volume of 88 µL. The samples frequency was 30/h nad the precision was better than 1.2% for 10 successive assays. The accuracy of the enzyme reactor-flow injection system was evaluated by comparison with HPLC results and an excellent correlation was obtained (r = 0.996). No measurable decrease in activity of the GIDH column was observed after a 3-month period. Glutamate dehydrogenase (NAD(P)+) immobilized on controlled-pore glass beads packed in a glass tube (7.5 cm x 1.7 mm) was used for the flow injection determination of glutamic acid (I) at room temp.; the NADH generated was detected fluorimetrically at 450 nm (excitation at 360 nm). The log. (peak height) - log. calibration graph was rectilinear for 0.01 to 0.50 mM I (injection volume 88 µL), and the detection limit was 5 µM. Cheese was initially extracted by the method of Harwalkar and Elliott (J. Dairy Sci., 1971, 54, 8), the extract was freeze-dried, and the residue was dissolved in 0.1 M phosphate buffer (pH 8.0) with filtration. Results correlated well with those by HPLC (r = 0.996).
l-Glutamic acid Food Fluorescence Sample preparation

"Determination Of Neomycin In Milk By Reversed-phase Ion-pairing Liquid Chromatography"
J. Liq. Chromatogr. Relat. Technol. 1989 Volume 12, Issue 8 Pages 1497-1515
Badar Shaikh; Jean Jackson

Abstract: Milk was skimmed and a 1 mL portion was vortex-mixed with 20% trichloroacetic acid solution (100 µL) and centrifuged at 4000 rpm and 4°C for 30 min. A 180 µL portion of the supernatant liquid was vortex-mixed with 20 µL of 1 M Na pentanesulfonate - 0.07 M acetic acid, and a 25 µL aliquot of the mixture was analyzed by HPLC on a column (15 cm x 4.6 mm) fitted with a guard column (2 cm x 4.6 mm) both containing Supelcosil LC-8-DB (5 µm) at 32.5°C. Post-column derivatization was at 33°C in a reaction coil with phthalaldehyde. The ion-pairing mobile phase contained 0.01 M pentanesulfonate, 0.056 M Na2SO4, 7 mM acetic acid and 1.5% methanol and fluorimetric detection was at 455 nm (excitation at 340 nm). A calibration graph (peak heights) was rectilinear from 0.15 to 12 µg mL-1 of neomycin in whole milk, and overall recovery was 94%, with coefficient of variation of 6.8%. The method was applied to monitor neomycin in milk after intramuscular injection at 10 mg kg-1.
Neomycin B Milk Whole Skimmed HPLC Fluorescence

"An Automated Microtechnique For Selenium Determination In Human Body Fluids By Flow Injection Hydride Atomic Absorption Spectrometry"
J. Trace Elem. Electrolytes Health Dis. 1990 Volume 4, Issue 1 Pages 41-48
Negretti de Bratter VE, Bratter P, Tomiak A

Abstract: The automation of a flow injection system for the hydride generation of selenium and its subsequent determination by atomic absorption spectrometry (FI-HAAS) is described. Pre-treatment of the sample and the details of the automated equipment are reviewed. For the FI-HAAS selenium analysis a volume of 350 µL of acid-digested sample solution is injected. The online generated hydride is delivery by the gas-liquid separator and is transported together with an Ar stream to the heated quartz cell for the atomic absorption determination. The absolute detection limit is 35 pg Se; the relative detection limit 0.10 µg/L Se. The absolute determination limit in real biological samples is 110 pg Se; the relative detection limit 0.31 µg/L Se. The accuracy of the method was evaluated via analysis of certified standard reference materials. Quality control was made by comparing FI-HAAS and instrumental neutron activation analysis (INAA), as an independent analytical method. Two acid-digestion procedures (in open vessels at atmospheric pressure and bomb-digestion in pressure vessels) were experimentally tested. To determine the effectiveness of the selenium reduction and the completeness of the selenium hydride formation a parallel selenium determination was carried out by means of ICP-AES and FI-HAAS analysis. FI-HAAS was applied for blood serum analysis of children undergoing long-term total parenteral nutrition, as well as of persons with high dietary selenium intake, and for human milk analysis. Human serum or milk (150 µL) is digested overnight with 1 mL of concentrated HNO3, a further 1 mL of HNO3 is added, and the sample is ashed for 1 h at 170°C. After addition of 100 µL of H2SO4 and 50 µL of HClO4, the sample is ashed for a further 1.5 h. Alternatively bomb-digestion is performed for 5 h at 160°C. The digest is diluted to 3 mL with 5 M HCl and heated at 95°C for 30 min for reduction of Se(VI) to Se(IV). A 350 µL portion of this solution is injected into a water carrier stream (2.2 mL min-1) that is subsequently mixed with streams of HCl (2.2 mL min-1) and alkaline 3% NaBH4 (0.44 mL min-1). The reaction mixture is passed into a gas - liquid separator and the H2Se formed is swept by Ar (0.3 l min-1) into a heated silica tube, where it is atomized at 900°C for detection of Se at 196.0 nm. Calibration graphs are rectilinear for 0.87 to 8.7 ng of Se injected and the limit of detection is 0.1 µg l-1. Results for four biological standard reference materials (including NBS Bovine Serum and Oyster Tissue) agreed well with certified values. Results for Se in human serum or milk generally agreed well with those obtained by instrumental NAA.
Selenium Serum Human Milk NIST 1566 NIST 1598 Sample preparation Spectrophotometry

"Instrumentation Based On Microcomputers. 5. A Computer-operated Flow Injection Analyser"
Lab. Microcomput. 1989 Volume 8, Issue 2 Pages 44-52
Malcolme Lawes, D.J.;Pasquini, C.;Wong, K.H.

Abstract: Improvements in the instrument described previously (Anal. Abstr., 1988, 50, 9J17) and its control system are described. The apparatus was applied in the determination of NO2-, NO3-, NH4+ and PO43- in drinking water by conventional colorimetric reactions. Respective calibration graphs were rectilinear up to 0.1, 50, 0.12 and 20 ppm with limits of detection of 4, 30, 5 and 21 ppb. The coefficient of variation (n = 10) were generally 3%.
Nitrite Nitrate Phosphate Ammonium Nitrogen Water Spectrophotometry

"Automated Colorimetric Method For Determination Of Chlorine In Geological Materials Using Flow Injection Analysis Technique"
Lab. Rob. Autom. 1990 Volume 2, Issue 2 Pages 83-88
Chan, C.C.Y.

Abstract: Powdered rock sample (0.15 g) was fused with LiBO2 at 860°C and the melt was dissolved in 9% HNO3. After dilution to 15 ml, the solution was mixed with 0.5% Hg(SCN)2 and 0.5 M Fe(NO3) in a carrier flow of 6% HNO3 and the absorbance was measured at 480 nm. The method was applied to 22 geochemical reference samples and gave coefficient of variation from 0.7 to 9.3%; the results agreed closely with those obtained in the literature. The limit of determination was 15 ppm in rock and calibration covered 50 to 500 ppm.
Chlorine Geological Sample preparation Spectrophotometry

"Flow Injection Analysis System With Ion-selective Electrodes"
LaborPraxis 1990 Volume 14, Issue 7-8 Pages 596-597
Schwedt, G.

Abstract: The performance of such an analyzer. is demonstrated by the determination of S2- and CN- in waste water, for which the respective limits of determination are 0.03 and 0.1 mg l-1.
Waste Electrode

"Solid-phase Sample Collection For The Analysis Of Aldicarb Residues In Ground Water"
LC-GC 1989 Volume 7, Issue 3 Pages 268-271
Lesage, S.

Abstract: Samples were collected on Supelco C8 cartridges, the cartridges were dried for 1 min in pressurized air, and aldicarb and its sulfone and sulfoxide were eluted with 0.4 mL of acetonitrile and then 1.1 mL of 0.01 M HCl. The eluate was analyzed by HPLC on a column (25 cm x 4.6 mm) of Spherisorb ODS (10 µm), with aqueous 28% acetonitrile as mobile phase (1 mL min-1) and fluorescence detection after post-column derivatization as described by Krause (Anal. Abstr., 1981, 40, 5G41). A 20-fold pre-concentration of the sample was achieved; the detection limit was 1 µg l-1.
Aldicarb Ground Fluorescence

"Determination Of Traces Of Cobalt And Nickel In Steels By Flow Injection Online Extraction - Flame Atomic Absorption Spectrometry"
Lihua Jianyan, Huaxue Fence 1997 Volume 33, Issue 2 Pages 59-60
Gong Yu, Zhou Junming, Tang Zhiyong, Zhang Suicheng and Jin Zoxiang

Abstract: Sample (0.1 g) was heated gently to decompose in concentrated HCl and 2 mL HNO3 (1:1) then concentrated to 2 mL and cooled. The residue was treated with 5 mL triethanolamine and neutralized with HCl (1:1) and ammonia water. Having diluted with water to 25 mL (pH 7), a portion of the solution was injected into the flow injection online extraction setup (diagram illustrated) into a carrier stream of water (10 ml/min). The flow passed through a segregator into an extraction coil (3 m x 1 mm i.d.) with 2% ammonium pyrrolidinedithiocarbamate in IBMK as extractant (0.5 ml/min) for extraction for 1 min, with an organic-phase sampling time of 1 min. Determination of Co and Ni was by flame AAS. Detection limits for Co and Ni were 0.01 and 0.02 µg/ml, respectively. The method was used in the analysis of metallurgical-standard steels, with RSD of 3.9-6%.
Cobalt Nickel Alloy Spectrophotometry Sample preparation

"Online Trace Metal Enrichment In Flow Injection Atomic Absorption Spectrometry"
Quim. Anal. 1989 Volume 8, Issue 2 Pages 159-170
Devi, S.;Habib, K.A.J.;Townshend, A.

Abstract: Aqueous samples containing Cu2+, Cd2+, Mg2+, Zn2+, Pb2+ and Hg2+ were pre-concentrated on a mini-column of 8-hydroxyquinoline-5-sulfonic acid immobilized on to controlled-pore glass and eluted with HNO3 or HCl (depending on the metal to be analyzed) directly into a nebulizer for AAS analysis. Calibration graphs were rectilinear from 0 to 100, 100 to 1000, 20 to 220, 10 to 100, 10 to 300 and 20 to 2000 ng mL-1 of Cd2+, Pb2+, Zn2+, Mg2+, Cu2+ and Hg2+, respectively; detection limits ranged from 0.5 ng mL-1 (for Cu) to 25 ng mL-1 (for Hg). . The coefficient of variation ranged from 1.1 to 2.9% (n = 4). Aqueous samples containing Cu2+, Cd2+, Mg2+, Zn2+, Pb2+ and Hg2+ were pre-concentrated on a mini-column of 8-hydroxyquinoline-5-sulfonic acid immobilized on to controlled-pore glass and eluted with HNO3 or HCl (depending on the metal to be analyzed) directly into a nebulizer for AAS analysis. Calibration graphs were rectilinear from 0 to 100, 100 to 1000, 20 to 220, 10 to 100, 10 to 300 and 20 to 2000 ng mL-1 of Cd2+, Pb2+, Zn2+, Mg2+, Cu2+ and Hg2+, respectively; detection limits ranged from 0.5 ng mL-1 (for Cu) to 25 ng mL-1 (for Hg). . The coefficient of variation ranged from 1.1 to 2.9% (n = 4).
Copper Cadmium Magnesium Zinc Lead Mercury Spectrophotometry

"Design Of Flow Injection Manifolds To Give The Best Detection Limits For Methods Involving Online Chemical Derivatization. 1. Theoretical Basis For High Sensitivity"
Quim. Anal. 1989 Volume 8, Issue 2 Pages 171-178
Tyson, J.F.

Abstract: High sensitivity can be achieved by designing a system that allows mixing with minimum dispersion or dilution. For flow injection analysis in which the peak height, corresponding to the product formed online by the inter-dispersion of injectate and reagent, is monitored as the analytical parameter, the same maximum sensitivity is obtained from single- and double-line manifolds. The double-line manifold requires a large volume to be injected and the dispersion coefficient (D) is obtained by a suitable flow rate ratio. Single-line manifolds have a higher throughput than the double-line to achieve the same dispersion.

"Ion-spray Mass Spectrometry Of Marine Neurotoxins"
Rapid Commun. Mass Spectrom. 1989 Volume 3, Issue 5 Pages 145-150
Michael A. Quilliam, Bruce A. Thomson, George J. Scott, K. W. Michael Siu

Abstract: Ion-spray mass spectrometry was investigated for the analysis of three marine neurotoxins: domoic acid, saxitoxin and tetrodotoxin. All three compounds gave positive-ion spectra with abundant ions of protonated molecules and no significant fragmentation. Domoic acid gave a negative-ion spectrum with a strong [M-H]- ion. Tandem mass spectrometry provided useful fragment-ion spectra for all compounds. Detection limits for flow injection analyzes with selected-ion monitoring were determined to be 30 pg for saxitoxin, 100 pg for domoic acid and 200 pg for tetrodotoxin. Combining liquid chromatography with ion-spray mass spectrometry allowed the determination of domoic acid and some of its isomers in toxic shellfish tissue extracts.
Saxitoxin Domoic acid Tetrodotoxin Marine LC Mass spectrometry Sample preparation

"Determination Of Copper(II) By Flow Injection Analysis"
Rev. Chim. 1990 Volume 41, Issue 4 Pages 361-365
Danet, A.F.;Mircea, V.

Abstract: Details are given of a flow injection analysis system for the determination of Cu(II) with an emphasis on the injection valve (illustrated). Sample solution (200 µL) was injected into a reagent stream (2.5 min-1) of aqueous 1 M NH3 solution and passed through a 60-cm reaction coil before the absorbance of the solution was measured at 630 nm. The calibration graph was rectilinear from 50 to >1600 ppm of Cu(II). The limit of detection was 50 ppm and the coefficient of variation (n = 14) was 0.8% at 800 ppm of Cu(II). Sample throughput was 75 to 300 h-1, depending on Cu concentration.
Copper(II)

"Ion-chromatographic Determination Of Total Metals In Soils"
Soil Sci. Soc. Am. J. 1990 Volume 54, Issue 5 Pages 1289-1297
N. T. Basta and M. A. Tabatabai*

Abstract: Surface soil samples (2 g) were digested sequentially with concentrated HNO3, HClO4 and HF. The HF treatment was repeated until dissolution was complete. An aliquot (25 ml) of the resulting solution was treated with ammonium citrate buffer (5 ml), hydroxylammonium chloride solution (2 ml) and pyridine (2.5 ml). The solution, pH adjusted to 9.5 with 10 M NaOH, was extracted with 0.2% of dithizone in CHCl3 (2 x 15 ml). The combined extracts were evaporated to dryness and the residue was treated with concentrated HNO3 (3 ml) and again heated to dryness. The residue was dissolved in 0.1 M HCl and analyzed on a HPIC-CS 5 column equipped with a HPIC-CG 5 guard column with buffered 4 mM 2,6-pyridinedicarboxylic acid (pH 4.8) or 40 mM oxalic acid (pH 4.8) as mobile phase (1 mL min-1). Post-column derivatization was achieved by mixing the column effluent with a stream of 0.01% ammoniacal solution of 4-(2-pyridylazo)resorcinol and 0.02% NN-dimethylethanolamine; the absorbance of the metal complexes was measured at 520 nm. Results obtained for Cu, Ni and Zn agreed with those obtained by AAS; low results were obtained for Cd, Mn and Pb. With oxalic acid as eluent, the detection limits were 5 µg L-1 for Cu and Zn and 20 µg L-1 for Ni; the coefficient of variation were 4.9% (n = 6).
Metals Copper Nickel Zinc Cadmium Manganese Lead Environmental HPIC Sample preparation Spectrophotometry

"Determination Of Starch In A Flow Injection System With Immobilized Enzymes"
Swed. J. Agri. Res. 1990 Volume 20, Issue 1 Pages 27-29
Bengtsson, S.;Larsson, K.

Abstract: Starch in ground samples (40 to 50 mg) of 36 compound feeds was hydrolyzed with a thermostable α-amylase (Termamyl) for 30 min at 95°C and determined by flow injection analysis with a carrier stream of 25 mM citrate buffer of pH 4.5 (0.8 mL min-1) and three packed-bed enzyme reactors containing (i) immobilized glucan 1,4-α-glucosidase, (ii) co-immobilized glucose oxidase, aldose 1-epimerase and (iii) peroxidase. The chromogenic reagent, 2 mM chromotropic acid and 1 mM 4-aminophenazone in citrate - phosphate buffer (pH 7) was added to the carrier stream, between reactors (i) and (ii), and H2O2 produced was detected spectrophotometrically at 590 nm. The detection limit was 2 µg mL-1 of starch. Results correlated well with a reference method (r = 0.992).
Starch Feed Spectrophotometry

"Determination Of Phosphate In Waters By Flow Injection Analysis"
Water Air Soil Pollut. 1990 Volume 52, Issue 3-5 Pages 359-368
F. Mas, J. M. Estela and V. Cerda

Abstract: A flow injection system is described in which water (200 µL) is treated with 0.026 M molybdate ion [prepared from (NH4)6Mo7O24.4H2O] and 0.06 mM Rhodamine B solution in 0.9N-H2SO4 medium at a flow rate of 1.8 mL min-1. Baseline drift was corrected by 0.1% polyvinyl alcohol. The absorbance of the complex was measured at 586 nm. The detection limit was 12 ppb of phosphate at a signal-to-noise ratio of 3:1 and a sampling rate of 55 h-1 was achieved. The coefficient of variation in the determination of 0.02 to 0.4 ppm of phosphate was 0.13 to 0.013.
Phosphate Water Spectrophotometry

"Evaluation And Comparison Of Ion Chromatography, Segmented-flow Analysis And Flow Injection Analysis For The Determination Of Nitrate In Natural Surface Waters"
Water Res. 1989 Volume 23, Issue 4 Pages 519-521
Eileen M. Burke, F. Xavier Suarez, Daniel C. Hillman,* and Edward M. Heithmar

Abstract: The cited techniques were used in the determination of nitrate (0.04 to 1.5 mg l-1) in water. Suppressed ion chromatography (IC) was performed on an AS4A column, with an AG4 pre-column and an anion micro-membrane suppressor, with a mobile phase (2 mL min-1) of 0.75 mM NaHCO3 - 2.2 mM Na2CO3. For segmented-flow analysis (SFA), a Technicon GTpc AutoAnalyzer II system was used with an ASTM Type II water carrier, sulfanilamide - N-(1-naphthyl)ethylendediamine dihydrochloride color reagent and NH4Cl - EDTA buffer system with a copperized-Cd reduction column. Flow injection analysis (FIA) was performed colorimetrically as in SFA with use of a dual-channel Lachat QuikChem system. The coefficient of variation, accuracy (% recovery) and detection limits were 3%, 103% and 7 µg L-1 for IC, 1%, 101% and 6 µg L-1 for SFA and 1%, 100% and 30 µg L-1 for FIA, respectively. Analysis times were 10 h-1 for IC (including simultaneous Cl- and SO42- determination), and 30 to 60 h-1 for SFA and FIA.
Nitrate Surface HPLC

"Continuous-flow Method For Determination Of Total Trihalomethanes In Drinking Water With Membrane Separation"
Water Res. 1989 Volume 23, Issue 6 Pages 739-742
Toyoaki Aoki and Kouji Kawakami

Abstract: The trihalomethanes, CHCl3, CHCl2Br, CHClBr2 and CHBr3 were determined by mixing the water sample with 10% NaSO3 solution and passing the mixture through a double tube system at 50°C. The inner tube comprised microporous PTFE and the outer tube was of PTFE. The volatile trihalomethanes passed into the inner tube which contained 0.2 M NaOH, the solution was mixed with 30% nicotinamide solution and the mixture was passed to a reaction coil at 98°C. The reaction product was cooled in an ice bath and determined fluorimetrically at 467 nm (excitation at 372 nm). There was no interference from species in drinking or river waters using this membrane separation system. The detection limit for CHCl3 was 0.8 µg l-1, and the coefficient of variation was 4.4% for 20 µg L-1 (n = 5).
Chloroform Bromodichloromethane Chlorodibromomethane Bromoform Water River Fluorescence

"Comparison Of Digoxin Analysis By High Performance Liquid Chromatography - Post-column Derivatization And Fluorescence-polarization Immunoassay"
Xenobiotica 1990 Volume 20, Issue 6 Pages 635-643
L. Embree and K. M. McErlane

Abstract: The method described previously (J. Chromatogr., 1989, 496, 321) was compared with the Abbott TDx method. The r value between the two methods for digoxin added to drug-free serum was 0.9897 (n = 7). However, serum from digitalized patients showed higher digoxin levels by the TDx method, probably owing to cross-reactivity of metabolites. Cross-reactivity of the TDx method towards endogenous material in the serum of certain patient groups was an even greater problem. The HPLC method (loc. cit.) gave complete resolution of digoxin. The calibration graph for this method was rectilinear for 0.5 to 3.3 ng mL-1 of digoxin in a 3 mL serum sample, with a mean coefficient of variation of 5.6% and a detection limit of 0.5 ng injected.
Digoxin Serum Human HPLC Immunoassay Fluorescence

"Study Of Flow Injection Analysis Chemiluminescence System Of 3,5-dibromosalicylfluorone - Hexadecyltrimethylammonium Bromide - Hydrogen Peroxide - Cobalt(II) And Determination Of Trace Cobalt(II) In Vitamin B12 [cyanocobalamin]"
Yaowu Fenxi Zazhi 1990 Volume 10, Issue 1 Pages 26-28
Li, G.H.;Li, M.;Zhang, W.G.

Abstract: Optimum conditions involved 0.15 mM 3,5-dibromosalicylfluorone, 15 mM hexadecyltrimethylammonium bromide, 0.2 M H2O2 and 0.1 M NaOH, and flow rates of 6.4 mL min-1. The calibration graph was rectilinear for 0.5 to 200 ng mL-1 of Co(II). The detection limit was 0.3 ng mL-1, and the coefficient of variation was 0.9%.
Cobalt(II) B12 Chemiluminescence

"HPLC Dual-electrode Electrochemical Detection Of Phenols After Post-column Derivatization"
Z. Chem. 1990 Volume 30, Issue 12 Pages 448-450
J&ouml;rg Noack, J&uuml;rgen Mattusch, Gerhard Werner

Abstract: A mixture of catechol, resorcinol and quinol in McIlvain buffer solution (pH 2.4) was analyzed by HPLC on a Separon (18.5 µm) reversed-phase column (15 cm x 4 mm). The amperometric detection system consisted of an Ag - AgCl reference electrode, a steel auxiliary electrode and two vitreous-carbon working electrodes. The eluted analyte was first oxidized at the first and then reduced at the second carbon electrode. With applied potentials +1100 and +100 mV, all three isomers gave anodic and cathodic peaks, but at +800 and -100 mV only catechol and quinol were detected. When post-column derivatization by UV irradiation [in a PTFE tube (9.5 m x 0.3 mm) at a flow rate of 0.6 mL s-1] was applied, the sensitivity for catechol and quinol deteriorated to 59% of the value found without derivatization. For resorcinol, however, irradiation caused a sensitivity improvement to 154% (by measurement of the anodic current at +1100 mV) and a decrease in the detection limit to 0.7 pmol.
Phenols HPLC Electrochemical analysis Amperometry Electrode

"Clenbuterol Residue Analysis By HPLC - HPTLC In Urine And Animal Tissues"
Z. Lebensm. Unters. Forsch. 1989 Volume 189, Issue 2 Pages 128-131
Jean-Marie Degroodt, Brigitte Wyhowski de Bukanski, Hedwig Beernaert and Dirk Courtheyn

Abstract: Tissue samples were digested with subtilisin A at 55°C for 1 h in 0.2 M Tris buffer of pH 8 containing 0.1 M CaCl2. The mixture was centrifuged, the solid was washed with more buffer and the supernatant solution were combined. This solution, or a diluted urine sample, was adjusted to pH 10 with NaOH and applied to a Chem Elut CE 1020 column; after 15 min, clenbuterol was eluted with hexane (three portions) and extracted from the eluate into 0.01 M HCl. The resulting solution (100 µL) was analyzed by HPLC on a column (25 cm x 4 mm) of LiChrosorb RP-8 (10 µm), with 0.01 M Na acetate (pH 3.5) - acetonitrile (3:7) as mobile phase (1 mL min-1) and post-column derivatization by adding NaNO2 - HCl (cooled in ice), ammonium sulfamate and N-(1-naphthyl)ethylenediamine with product determination at 500 nm. The calibration range for clenbuterol was 5 to 100 ng mL-1 and the detection limit was 2 ng. Recoveries ranged from 70 to 73% for tissues and from 85 to 90% for urine. The results were confirmed by high performance TLC.
Clenbuterol Urine Biological tissue HPLC

"Direct Determination Of Copper In Urine Using A Sol–gel Optical Sensor Coupled To A Multicommutated Flow System"
Anal. Bioanal. Chem. 2004 Volume 380, Issue 1 Pages 108-114
Paula C. A. Jer&oacute;nimo, Alberto N. Ara&uacute;jo, M. Concei&ccedil;&atilde;o B. S. M. Montenegro, Celio Pasquini, Ivo M. Raimundo Jr

Abstract: In this work, a multicommutated flow system incorporating a sol-gel optical sensor is proposed for direct spectrophotometric determination of Cu(II) in urine. The optical sensor was developed by physical entrapment of 4-(2-pyridylazo)resorcinol (PAR) in sol-gel thin films by means of a base-catalyzed process. The immobilized PAR formed a red 2:1 complex with Cu(II) with maximum absorbance at 500 nm. Optical transduction was based on a dual-color light-emitting diode (LED) (green/red) light source and a photodiode detector. The sensor had optimum response and good selectivity towards Cu(II) at pH 7.0 and its regeneration was accomplished with picolinic acid. Linear response was obtained for Cu(II) concentrations between 5.0 and 80.0 µg L-1, with a detection limit of 3.0 µg L-1 and sampling frequency of 14 samples h-1. Interference from foreign ions was studied at a 10:1 (w/w) ion:Cu(II) ratio. Results obtained from analysis of urine samples were in very good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP-MS); there was no significant differences at a confidence level of 95%.
Copper Copper(II) Urine Sensor

"Determination Of Furfural In An Oscillating Chemical Reaction Using An Analyte Pulse Perturbation Technique"
Anal. Bioanal. Chem. 2005 Volume 384, Issue 6 Pages 1438-1443
Jinzhang Gao, Hongxia Dai, Wu Yang, Hua Chen, Dongyu Lv, Jie Ren, Lei Wang

Abstract: A rapid and convenient method for the determination of furfural is presented that is based upon sequential perturbation of the Mn(II)-catalyzed B-Z oscillating system with different amounts of furfural using a continuous-flow stirred tank reactor (CSTR). When the sample was injected, the change in the amplitude and/or period was linearly proportional to the logarithm of the concentration of furfural over the range 3 x 10^-8~1 x 10^-5 mol L-;1. This method gave a detection limit of 3 x 10^-9 mol L-;1 under optimum conditions. Finally, the possible mechanism of furfural perturbation in the oscillating reaction is discussed. When the furfural was injected into the Mn(II)-catalyzed B-Z oscillating system, the change in the amplitude and/or period was linearly proportional to the logarithm of the concentration of furfural over the range 3 x 10^-8~1 x 10^-5 mol L-;1, with a detection limit of 3 x 10^-9 mol L-;1 under optimum conditions.
Furfural

"Sample Introduction Assisted By Compressed Air In Flame Furnace AAS: A Simple And Sensitive Method For The Determination Of Traces Of Toxic Elements"
Anal. Bioanal. Chem. 2005 Volume 382, Issue 8 Pages 1826-1834
Harald Berndt, Erika Pulvermacher

Abstract: The power of detection of flame AAS for the toxic elements Cd, Hg, Pb and Tl can be improved by 1-2 orders of magnitude by using flame furnace AAS. In flame-furnace AAS, liquid samples are introduced directly into a nickel tube located in the flame, in the simplest case through a ceramic thermospray capillary. Transportation of the samples is achieved by using compressed air only. Comparatively low detection limits are achieved by both beam injection flame furnace (BIFF-AAS) and thermospray flame furnace AAS (TS-FF-AAS). For TS-FF-AAS, a pressure of less than 20 kPa (<80 in. water) is required. The TS-FF-AAS technique is very simple, robust and cheap. The detection limits were 0.2-0.4 µg L-1 (Cd), 40-100 µg L-1 (Hg), 5-9 µg L-1 (Pb) and 4-14 µg L-1 (Tl), respectively, depending on the method, flow rate and sample volume used. Pb and Cd were found at concentrations of 0.1-2 and 0.005-0.3 µg g-1, respectively, in samples of various spices.
Cadmium Mercury Lead Thallium Spectrophotometry Spectrophotometry Spectrophotometry

"Determination Of Copper In Powdered Chocolate Samples By Slurry-sampling Flame Atomic-absorption Spectrometry"
Anal. Bioanal. Chem. 2005 Volume 382, Issue 4 Pages 1099-1102
Walter N. L. dos Santos, Erik G. P. da Silva, Marcelo S. Fernandes, Rennan G. O. Araujo, Ant&ocirc;nio C. S. Costa, M. G. R. Vale, S&eagrave;rgio L. C. Ferreira

Abstract: Chocolate is a complex sample with a high content of organic compounds and its analysis generally involves digestion procedures that might include the risk of losses and/or contamination. The determination of copper in chocolate is important because copper compounds are extensively used as fungicides in the farming of cocoa. In this paper, a slurry-sampling flame atomic-absorption spectrometric method is proposed for determination of copper in powdered chocolate samples. Optimization was carried out using univariate methodology involving the variables nature and concentration of the acid solution for slurry preparation, sonication time, and sample mass. The recommended conditions include a sample mass of 0.2 g, 2.0 mol L-1 hydrochloric acid solution, and a sonication time of 15 min. The calibration curve was prepared using aqueous copper standards in 2.0 mol L-1 hydrochloric acid. This method allowed determination of copper in chocolate with a detection limit of 0.4 µg g-1 and precision, expressed as relative standard deviation (RSD), of 2.5% (n=10) for a copper content of approximately 30 µg g-1, using a chocolate mass of 0.2 g. The accuracy was confirmed by analyzing the certified reference materials NIST SRM 1568a rice flour and NIES CRM 10-b rice flour. The proposed method was used for determination of copper in three powdered chocolate samples, the copper content of which varied between 26.6 and 31.5 µg g-1. The results showed no significant differences with those obtained after complete digestion, using a t-test for comparison.
Copper Food Spectrophotometry

"Comparative Study Of Atomic Fluorescence Spectroscopy And Inductively Coupled Plasma Mass Spectrometry For Mercury And Arsenic Multispeciation"
Anal. Bioanal. Chem. 2005 Volume 382, Issue 2 Pages 485-492
Jos&eacute; Luis G&oacute;mez-Ariza, Fernando Lorenzo, Tamara Garc&iacute;a-Barrera

Abstract: Mercury and arsenic are two elements of undoubted importance owing to their toxic character. Although speciation of these elements has been developed separately, in this work for the first time the speciation of As and Hg using two atomic fluorescence detectors in a sequential ensemble is presented. A coupling based on the combination of high-performance liquid chromatography (where mercury and arsenic species are separated) and two atomic fluorescence detectors in series, with several online treatments, including photooxidation (UV) and hydride generation, has allowed the determination of mercury and arsenic compounds simultaneously. The detection limits for this device were 16, 3, 17, 12 and 8 ng mL-1 for As(III), monomethylarsinic acid, As(V), Hg2+ and methylmercury, respectively. This coupling was compared with an analogous one based on inductively coupled plasma-mass spectrometry (ICP-MS) detection, with detection limits of 0.7, 0.5, 0.8, 0.9 and 1.1 ng mL-1, respectively. Multispeciation based on ICP-MS exhibits better sensitivity than the coupling based on tandem atomic fluorescence, but this second device is a very robust system and exhibits obvious advantages related to the low cost of acquisition and maintenance, as well as easy handling, which makes it a suitable system for routine laboratories.
Arsenic Mercury Arsenic(3+) Monomethylarsine Arsenic(5+) Mercury(II) Methylmercury ion Fluorescence HPLC Mass spectrometry