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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pH

Classification: Reagent -> pH

Citations 264

"Comparison Of Extraction Procedures For Arsenic Speciation In Environmental Solid Reference Materials By High-performance Liquid Chromatography-hydride Generation-atomic Fluorescence Spectroscopy"
Appl. Organomet. Chem. 2002 Volume 16, Issue 7 Pages 347-354
M. Montperrus, Y. Bohari, M. Bueno, A. Astruc, M. Astruc

Abstract: Water and soft extractions (hydroxylammonium hydrochloride, ammonium oxalate and orthophosphoric acid) have been studied and applied to the determination of arsenic species (arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) in three environmental solid reference materials (river sediment, agricultural soil, sewage sludge) certified for their total arsenic content. The analytical method used was ion exchange liquid chromatography coupled online to atomic fluorescence spectroscopy through hydride generation. Very low detection limits for arsenic were obtained, ranging from 0.02 to 0.04 mg kg-1 for all species in all matrices studied. Orthophosphoric acid is the best extractant for sediment (mixed origin) and sludge samples (recent origin) but not for the old formation soil sample, from which arsenic is extracted well only by oxalate. Both inorganic forms (As(III) and As(V)) are significant in all samples, As(V) species being predominant. Moreover, organic forms are found in water extracts of all samples and are more important in the sludge sample. These organic forms are also present in the soft extracts of sludge. Microwave-assisted extraction appears to minimize the risk of a redox interconversion of inorganic arsenic forms. This study points out the necessity of combining direct and sequential extraction procedures to allow for initial arsenic speciation and to elucidate the different mineralogical phases-species associations.

"Evaluation Of A Four Sensor Array Used In A Wall-jet Configured Flow Cell For Plow Injection Potentiometry"
Electroanalysis 2001 Volume 13, Issue 2 Pages 161-163
Lucy Tina Dimitrakopoulos, Telis Dimitrakopoulos

Abstract: Photo-cured calcium, potassium, and nitrate ion-selective electrodes and Ag/AgCl wire as a chloride electrode have been integrated into a sensor array that is suitable for FIP measurements in a wall-jet flow cell. Each sensor in the electrode-array exhibited near-Nemstian response over a log-linear range between 0.1 mM and 10 mM and detection limits of 0.01 mM in the flow injection potentiometric mode. The four coated wire electrodes were used simultaneously in the flow injection mode to determine their respective determinand in various water samples and the results were in good agreement with standard analytical methods.

"Gradient Elution Techniques For Capillary Electrochromatography"
J. Chromatogr. A 2000 Volume 887, Issue 1-2 Pages 115-124
Catherine A. Rimmer, Stephanie M. Piraino and John G. Dorsey

Abstract: Capillary electrochromatography (CEC) is a rapidly maturing technique, but still in need of further instrumental development and in need of unique applications that are not possible by traditional pressure-driven LC. We review the development of gradient elution schemes for CEC, beginning with pH gradients initially developed for capillary electrophoresis. Step gradients are the most easily instrumentally implemented, but provide less flexibility in separation than continuous gradients. Pressure-assisted CEC is easily adapted to gradient elution schemes, but does not offer the advantages of very high column efficiency provided by totally electro-driven mobile phases. The development of flow injection interfaces allows a true solvent gradient to be generated by Ir-LC pumps, with the mobile phase drawn into the separation capillary by pure electroosmotic flow. While requiring both a CEC instrument and a traditional pump or pumps capable of generating the gradient, this method offers advantages of greatly reduced column handling, prolonging column lifetimes, and allows simple autosampling. We also discuss voltage gradients, which provide a mobile phase velocity gradient.

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

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

"Application Of Ion Sensitive Field Effect Transistor Based Sensors To Soil Analysis"
Comput. Electron. Agric. 2001 Volume 31, Issue 3 Pages 281-293
J. Artigas, A. Beltran, C. Jiménez, A. Baldi, R. Mas, C. Domínguez and J. Alonso

Abstract: Standard methods to measure nutrient levels in soil are complex and time consuming due to the extraction and pre-treatment processes involved. Besides, the instrumentation used for these measurements is also expensive. Therefore, the use of chemical sensors warrants investigation since they can be placed directly in the soil and results can be provided in real or quasi-real time at a moderate cost. The control of nutrients with sensors will permit an optimization of irrigation and fertilisation management systems and thus will be useful for reducing the environmental impact caused by the runoff of nutrients into surface and ground waters. In this work, the use of chemical sensors based on ion sensitive field effect transistors (ISFETs) for soil analysis is proposed. These devices are fabricated with microelectronic technology - providing some important advantages such as robustness, small size, low output impedance and mass production. Fabrication of pH, Ca2+, K+ and NO3- ISFETs with photocurable polymeric membranes and their evaluation in aqueous solutions is reported. Studies of their response in horticulture soils and comparison with standard methods have been performed. The results confirm the feasibility of ISFET based sensors for in-soil monitoring and the promising future applications they have. (C) 2001 Elsevier Science B.V. All rights reserved.

"Determination Of Nano-molar Levels Of Formaldehyde In Drinking Water Using Flow Injection System With Immobilized Formaldehyde Dehydrogenase After Off-line Solid-phase Extraction"
Anal. Chim. Acta 1999 Volume 378, Issue 1-3 Pages 169-175
Nobutoshi Kiba, Limin Sun, Shinya Yokose, Masaki Tachibana Kazue and Tani Takashi Suzuki

Abstract: Low levels of formaldehyde were determined by pre-concentration with poly(allylamine) beads and analysis by flow injection system with immobilized formaldehyde dehydrogenase. Formaldehyde dehydrogenase was immobilized on tresylate-poly(vinyl alcohol) beads and packed into a stainless-steel column (5 cm x 4 mm). The column was incorporated in a flow injection system with fluorimetic detection. The calibration graph was linear from 0.5 to 10 µM (15-300 µg l-1). The poly(allylamine) beads (0.5 g) were used to adsorb formaldehyde present at 20-400 nM (0.6-12 µg l-1) from drinking water (11). Formaldehyde was eluted with 1 M HCl (10 ml). The solution (50 µl) adjusted to pH 9 was injected into the flow injection system. Concentration factor was 25-fold. Recovery of formaldehyde spiked into purified water was >96% with a relative standard deviation of <3.0%.
Formaldehyde Water Spectrophotometry

"Electrocatalytic Reduction Of Nitrite At A Carbon Fiber Microelectrode Chemically Modified By Palladium(II)-substituted Dawson Type Heptadecatungstodiphosphate"
J. Electroanal. Chem. 1999 Volume 469, Issue 1 Pages 63-71
Wenliang Sun, Song Zhang, Xinrong Lin, Litong Jin, Songling Jin, Jiaqi Deng and Jilie Kong

Abstract: A new type of chemically modified electrode (CME) was fabricated by electrodeposition of palladium(II)-substituted Dawson type heptadecatungstodiphosphate, K-8[P2W17O61Pd(H2O)] (abbreviated as P2W17Pd in the following), onto a carbon fiber microelectrode (CFME). A pair of waves was observed on the P2W17Pd CFME, which is ascribed to the redox process of the palladium center in the heteropolytungstate. After continuous potential scanning for 30 min in a pH 4.0 buffer, 92% of the original electrode response remained for the P2W17Pd CFME. The P2W17Pd CFME had high electrocatalytic activity for nitrite reduction and exhibited good reproducibility and stability. The catalytic peak current was found to be linear with the nitrite concentration in the range of 1.0 x 10^-7 similar to 1.2 x 10^-3 mol L-1 (at 25°C) with a correlation coefficient of 0.9886 The detection limit (signal/noise = 3) was found to be 2.0 x 10^-8 mol L-1. The response time of the microsensor for nitrite measurement was less than 15 s. For 10 parallel measurements of 1.0 x 10^-5 mol L-1 nitrite, the relative standard deviation (RSD) was found to be 4.5%. The sensitivity of the microsensor was 0.57 nA (µmol l-1)-1. The P2W17Pd CME was applied successfully as an electrochemical detector (ECD) to determine the nitrite level in rat brain by flow injection analysis (FIA) coupled with microdialysis sampling. The linear range was over three orders of magnitude and the detection limit was 3.0 pmol for nitrite determination. The mechanism of the catalytic reaction was also addressed.

"Continuous Monitoring Of Amino Acids And Related Compounds With Poly(3-methylthiophene)-coated Cylindrical Carbon Fiber Microelectrodes"
Anal. Chim. Acta 1999 Volume 401, Issue 1-2 Pages 145-154
L. Ag&uuml;&iacute;, A. Gonz&aacute;lez-Cort&eacute;s, P. Y&aacute;&ntilde;ez-Sede&ntilde;o and J. M. Pingarr&oacute;n

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

"Development Of Xylitol Oxidase-based Flow Injection Analysis For Monitoring Of Xylitol Concentrations"
Anal. Chim. Acta 2002 Volume 456, Issue 2 Pages 293-301
J. I. Rhee, M. Yamashita and Th. Scheper

Abstract: A flow injection method for monitoring xylitol was developed using xylitol oxidase (XYO) immobilized on a VA-Epoxy Biosynth E3-support. The immobilized XYO cartridge had a good operational lifetime (up to 24 h) and storage stability (up to I month). The XYO-FIA system with an oxygen electrode was investigated systematically regarding the factors that can affect enzyme activity, such as pH, reaction temperature, carrier solution and sample matrix. In order to attain high activity of the immobilized XYO, potassium phosphate solution (I M) with 0.5 g L-1 Triton X-100 adjusted to pH 8.5 was used as the carrier solution. Sample matrix effects on the immobilized XYO were also investigated. High concentrations of some components (arabinose, 20 g l-1; xylose, 30 g l-1; NaCl, 30 g l-1) in the sample had significant inhibitory effects on the response of the XYO-FIA system. The performance of the XYO-FIA system was tested by using different sample injection volumes (75-250 µL) and carrier flow rates (0.7-2.0 mL min-1).

"Soil Analysis Procedures Using 0.01 M Calcium Chloride As Extraction Reagent"
Commun. Soil Sci. Plant Anal. 2000 Volume 31, Issue 9-10 Pages 1299-1396
Houba, V.J.G.;Temminghoff, E.J.M.;Gaikhorst, G.A.;Van Vark, W.

Abstract: This publication gives details of laboratory procedures for the determinations of bioavailable (e.g., plants) quantities of nutritional and polluting inorganic elements in 0.01 MCaCl2 extracts of air-dry soil samples. Air-day soil samples are extracted for two hours with a 0.01 M CaCl2 solution of 20°C in a I:10 extraction ratio (W/V). After measuring the pH in the settling suspension, the concentrations of nutritional and polluting elements are measured in the clear centrifugate or filtrate. The procedure is simple, easy to perform, and cheap (labor, chemicals) in daily use in routine soil laboratories. The method receives internationally more and more attention as an alternative for the many extraction procedures for a single nutrient or pollutant that are still in use nowadays. The soil is extracted with a solution what has more or less the same ionic strength as the average salt concentration in many soil solutions. Various nutrients and metals can be measured in a single extract that allows considering relationships between them during interpretation of the data. For most elements, different detection techniques are described in detail in this publication. Detailed laboratory procedures are described for the determination of pH, total dissolved organic carbon, nitrate, ammonium, total dissolved nitrogen, sulfate, total dissolved sulfur, ortho-phosphate, total dissolved phosphate, sodium, potassium, magnesium, cadmium, copper, nickel, lead, aluminum, iron, arsenic, boron, and phenols. Since only one extract of soil samples is used, profitable use can be made of multi-element detection techniques like segmented-flow analysis spectrometry, ICP-OES, and ICP-MS.

"Online Monitoring Of Calcium In Natural, Borehole And Boiler Feed Water With A Flow Injection System Using A Calcium-selective Membrane Electrode As A Sensor"
South Afr. J. Chem. 1999 Volume 52, Issue 1 Pages 24-26
Van Staden, J.F.; Stefan, R.I.

Abstract: An online automated system for the determination of calcium in natural, borehole and boiler feed water based on the concept of flow injection with a calcium-selective membrane electrode as sensor is described. The system is suitable for the on-site monitoring of calcium at a sampling rate of 60 samples per hour in the linear range 10^-4 - 10^-2 mol L-1 (approximately 4-400 mg l-1) with an RSD better than 0.7%. The detection limit of the system is 2.1 x 10^-6 mol L-1 (about 0.084 mg l-1).

"Simultaneous Flow Injection Determination Of Calcium And Fluoride In Natural And Borehole Water With Conventional Ion-selective Electrodes In Series"
Talanta 1999 Volume 49, Issue 5 Pages 1017-1022
J. F. van Staden and R. I. Stefan

Abstract: An online automated system for the simultaneous flow injection determination of calcium and fluoride in natural and borehole water with conventional calcium-selective and fluoride-selective membrane electrodes as sensors in series is described. Samples (30 µl) are injected into a TISAB II (pH = 5.50) carrier solution as an ionic strength adjustment buffer. The sample-buffer zone formed is first channeled to a fluoride-selective membrane electrode and then via the calcium-selective membrane electrode to the reference electrodes. The system is suitable for the simultaneous on-site monitoring of calcium (linear range 10^-5-10^-2 mol L-1 detection limit 1.94 x 10^-6 mol L-1 recovery 99.22%, RSD < 0.5%) and fluoride (linear range 10^-5-10^-2 mol L-1 detection limit 4.83 x 10^-6 mol L-1 recovery 98.63%, RSD = 0.3%) at a sampling rate of 60 samples h-1.

"PH Study Of The Electrocatalytic SO2 Detection At A Glassy Carbon Electrode Modified With Iron(II)tetrasulfophthalocyanine"
Microchim. Acta 2002 Volume 140, Issue 3-4 Pages 233-239
Mamothibe Thamae, Philippe Westbroek, Tebello Nyokong

Abstract: The electrocatalytic determination of SO2 is studied as a function of pH at a glassy carbon electrode modified with iron(II)tetrasulfophthalocyanine ([Fe(II)TSpC](4-)). It was found in the literature that depending on pH, SO2 . xH(2)O, HSO3- and/or SO32 are the main compounds in solution, that these compounds behave differently at the electrode surface, and that the condition of the electrode surface is stable over the entire pH-range. The use of SO2(g) or sodium sulfite as starting material did result in identical curves except in the pH range from 7.5-9.0. A possible explanation could be given by proposing that SO2 . xH(2)O is very unstable in the presence of SO3. In strongly acidic medium, SO2 . xH(2)O is the main compound, which can be oxidized as well as reduced with exchange of two electrons. HSO3- is the main compound at pH = 4 and can also be oxidized and reduced with exchange of, respectively, two and four electrons. In alkaline solution sulfite is the main compound and can only be oxidized, also under exchange of two electrons. Detection limits are in the range of 4.0±0.1 x 10^-5 and 7.5±0.1 x 10^-5 mol L-1, dependent of pH and of the type of reaction (oxidation or reduction) used.

"Comparison Study Of Five Analytical Methods For The Fractionation And Subsequent Determination Of Aluminum In Natural Water Samples"
J. Environ. Monit. 2000 Volume 2, Issue 2 Pages 171-181
Torild Wickstr&oslash;m, Nicholas Clarke, Kirsti Derome, John Derome and Eirin R&oslash;geberg

Abstract: Five methods for aluminum fractionation used in different laboratories in Norway and Finland were compared using six control, 75 soil water and 10 lake water samples. Different fractionation principles [cation exchange, formation of the Pyrocatechol Violet (PCV) or quinolin-8-ol (oxine) complex], types of cation exchanger [Amberlite (Na/H) or Bond Elut (H)], reaction time (from 2.3 s), flow systems (flow injection analysis or segmented flow) and determination principles (molecular absorption spectrometry or ICP-AES) were tested. Determination of the labile fraction was strongly dependent on the method used and the largest differences were observed between the ICP-AES method with cation exchange (Bond Elut H form) and the quickly reacting method (oxine, 2.3 s). Different flow systems, both using cation exchange and determination of the PCV complex but with different reaction times and an extra acidification step, resulted in large differences in the reactive and non-labile fractions determined. However, the determination of the labile fraction gave similar results with both these methods. The two different types of cation exchanger used (with and without pH buffering and with different counter ions) in the ICP-AES methods resulted in differences, mainly because of a smaller non-labile fraction in the non-buffered system. The two flow injection systems (oxine and PCV complexation) showed common trends, which may be connected with the short reaction times used. Comparison with theoretical equilibrium calculations using the model ALCHEMI suggested that the best correlation for the determination of the labile fraction were obtained with the ICP-AES method with an Amberlite column.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

"Spectrophotometric Determination Of PH By Flow Injection"
Anal. Chim. Acta 1990 Volume 231, Issue 1 Pages 21-26
Stephen H. Pia, Donna P. Waltman and Daniel C. Hillman, Kenneth W. Street, Jr

Abstract: An appropriate combination of pH indicators was used in a flow injection system (manifold illustrated); e.g., for the pH range 3 to 8 the methyl red - methyl yellow - neutral red mixture of Tucker et al. (J. Chem. Educ., 1989, 66, 769) was used, with detection at 555 nm. The degree of rectilinearity of the response is discussed. The sample throughput is ~100 h-1, and the precision and accuracy are ±0.2 pH. Use of the system for determining the pH of lake waters is described.
pH Lake Spectrophotometry

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

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

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

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

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

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

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

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

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

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

"Indirect Flow Injection Determination Of Methadone By Atomic Absorption Spectrometry"
Anal. Chim. Acta 1990 Volume 234, Issue 2 Pages 433-437
R. Montero, M. Gallego and M. Valc&aacute;rcel

Abstract: Methadone (I) is determined in tablets and urine in the presence of other drugs after reduction on a Cd or Zn micro-column and flame AAS detection of the metal ions released. For urine, a 5 mL sample is made alkaline with NaOH and extracted with CH2Cl2. The residue from evaporation of the extract, is dissolved in water, and the solution is adjusted to pH 4.0 with 0.01 M acetic acid. Crushed tablet (200 mg) is dissolved in water by shaking for 55 min and filtering. The final solution (90 µL), at pH 3.3 to 4.3, is injected into a carrier stream of water (3.0 mL min-1) which proceeds to the reduction column (8.5 cm x 1.8 mm) and subsequently to the spectrometer. The calibration graph is rectilinear from 5 to 50 ng mL-1 of I. Recoveries from either column are quantitative, and coefficient of variation in urine (n = 3) are 1.2 to 3.0%. Sampling frequency is 150 h-1, and other drugs do not interfere.
Methadone Pharmaceutical Urine Spectrophotometry 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

"Amperometric Determination Of Glucose In Undiluted Food Samples"
Anal. Chim. Acta 1991 Volume 242, Issue 1 Pages 91-98
A. Amine and G. J. Patriarche, G. Marrazza and M. Mascini

Abstract: A sensor is described for determination of glucose. It involves glucose oxidase immobilized on to a cellulose acetate membrane through glutaraldehyde bonding. The membrane is placed over the Pt electrode of a H2O2 sensor. By placing a silanized polycarbonate membrane over the enzyme layer, the rectilinear range of the calibration graph was extended to higher concentration. The variation in response was studied as a function of pore size of the polycarbonate membrane. Response was approximately even from pH 4 to 8. The sensor was used in a flow injection system to determine 1 M glucose in soft drinks at a sampling rate of 60 h-1, and without the need for sample dilution. The coefficient of variation was 1.8% (n = 16) for 0.4 M glucose.
Glucose Soft drink Amperometry Electrode Electrode

"Amperometric Determination Of Hydrogen And Hydroxy Ion Concentrations In Unbuffered Solutions In The PH Range 5 To 9"
Anal. Chim. Acta 1991 Volume 243, Issue 1 Pages 55-59
G. Horvai and E. Pungor

Abstract: The cited determination was performed with use of a dual-channel flow injection system. The LC amperometric detector was equipped with a large-volume wall-jet cell containing a H+-selective working electrode, which comprised a plasticized PVC membrane loaded with tridodecylamine (prep. described) and filled with 1 mM HCl - 0.1 M KCl into which was immersed a Ag - AgCl reference electrode. A Pt wire was used as the counter electrode. The sample solution, injected into water in one channel of the system, was mixed with 0.1 M NaCl from the second channel; flow rates were 1.05 mL min-1. Both H+ and OH- were determined from 1 to 10 µM. Satisfactory selectivity with respect to several common cations and anions was demonstrated. The flow injection amperometric method was also used for flow acid - base titrations.
Acidity Hydroxide Amperometry LC Electrode Electrode

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

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

"Activity Of Immobilized Yeast Aldehyde Dehydrogenase In A Flow Injection System"
Anal. Chim. Acta 1991 Volume 249, Issue 1 Pages 145-154
Elena Dom&iacute;nguez, Gy&ouml;rgy Marko-Varga, B&auml;rbel Hahn-H&auml;gerdal and Lo Gorton

Abstract: The stability of an immobilized yeast aldehyde dehydrogenase (I) reactor used in a flow injection system for determination of aldehydes was studied. Stability was improved if the Schiff base formed during immobilization was reduced with sodium cyanoborohydride. Reactivation of immobilized I with glycine, other amino-acids and mercaptoethanol and the effects of pH and NAD+ are discussed. Under optimum analysis conditions, viz., 0.1 M potassium phosphate buffer solution (pH 7.5) containing 0.15 M KCl, 200 mM glycine, 4 mM mercaptoethanol and 2 mM NAD+ as carrier solution and flow rate 1 mL min-1, a 10 µL reactor was stable for 1 month. Calibration graphs were rectilinear from 3 µM to 7 mM of aldehyde and sample throughput was 45 h-1.
Aldehydes

"Fluorimetric Determination Of Boron With Chromotropic Acid By Flow Injection Analysis"
Anal. Chim. Acta 1991 Volume 251, Issue 1-2 Pages 269-274
S. Motomizu*, M. Oshima and Z. Jun

Abstract: Three flow injection systems were evaluated for the cited determination. The best results were obtained with the system in which sample solution (200 µL) was injected into water (carrier stream; flow rate 0.4 mL min-1), the stream was merged with 0.25 mM chromotropic acid (reagent stream) and allowed to react in a 2-m PTFE reaction coil before being merged with 0.5 M NaOH and passed to a spectrofluorimeter. Fluorimetric detection was at 350-360 (excitation at 313 nm). With this system a sample pH of 2 to 12 was tolerated. The calibration graph was rectilinear from 0.5 nM to 0.1 mM B(OH)3. The detection limit was 5 nM-B. The sampling rate was 60 h-1. Tolerated concentration. of ions normally present in water are tabulated. The method was applied to water samples.
Boron Water Fluorescence

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

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

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

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

"Batchwise And Flow Injection Methods For Thermo-spectrophotometric Determination Of Acetylcholine And Choline With Tetrabromophenolphtalein Ethyl Ester"
Anal. Chim. Acta 1991 Volume 255, Issue 1 Pages 135-141
Tadao Sakai*, Yun-Hua Gao and Noriko Ohno, Nobuo Ura

Abstract: Aqueous sample solution was injected into a carrier stream of 0.3 M KH2PO4 - 0.1 M Na borate adjusted to pH 11 with 1 M NaOH, which merged with the extracting solution of tetrabromophenolphthalein ethyl ester in CH2Cl2. The extract was separated with use of a PTFE porous membrane and passed through a micro-flow cell at 45°C before its absorbance was measured at 610 nm. Sample throughout was 36 h-1 for acetylcholine (I) and choline (II). Calibration graphs were rectilinear for 0.625 to 7.5 µM-I and 1.25 to 15 µM-II. The coefficient of variation was 1.2% for 5 µM-I and 10 µM-I. The effect of amines on the determination is discussed. The determination was also carried out by batchwise method (details given).
Acetylcholine Choline Electrode Spectrophotometry Sample preparation

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

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

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

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

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

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

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

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

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

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

"Sequential Flow Injection Spectrofluorimetric Determination Of Coumarins Using A Double-injection Single-line System"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 293-298
P. Solich*, M. Pol&aacute;ek and R. Karl&iacute;ek

Abstract: A flow injection technique with fluorimetric detection was described for the sequential determination of 6-methoxy-7-hydroxycoumarin (scopoletine) and 7-hydroxycoumarin (umbelliferone) without prior separation. A single-line flow injection system equipped with a double-injection valve was employed to allow the simultaneous injection of sample (40 µL) and phosphate buffer (100 µL) into an aqueous 50% ethanol carrier stream (1 ml/min). The buffer-sample-buffer plug was propelled through the mixing coil (0.5 m x 0.5 mm i.d.) to the detector where the fluorescence at 418 nm was measured (excitation at 350 nm). Buffer solutions of pH 6 and 11 were injected sequentially. A calculation method based on differential fluorimetry was used to determine 1 µM-scopoletine in the presence of a 9-fold excess of umbelliferone or 1 µM-umbelliferone in the presence of a 23-fold excess of scopoletine. The analysis of synthetic binary mixtures containing 24 µM-coumarins yielded recoveries of 96-115%. The technique can be applied to the analysis of binary mixtures of other fluorescent compounds which exhibit pH-dependent excitation spectra.
Coumarin, 6-methoxy-7-hydroxy 7-Hydroxycoumarin Fluorescence

"Automatic Testing Of Enzyme Modifiers By The Flow-gradient Technique"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 152-158
Juliana Marcos, Angel R&iacute;os and Miguel Valc&aacute;rcel*

Abstract: A flow system was developed for studying the influence of various substances (potential modifiers) on an enzymatic reaction. The flow system utilized a variable flow pump (PP) controlled by a microcomputer and a conventional constant flow pump (CP). The flow rate of PP was increased linearly from 0-0.5 ml/min to produce a linear increase in modifier concentration in a 0.1 M phosphate buffer stream at pH 7. The mixture was merged sequentially with substrate and enzyme streams propelled by the CP pump. In this way a linear concentration gradient of the modifier was produced whilst keeping the concentration of the substrate and enzyme constant and maintaining a constant flow of 1.7 ml/min through the spectrophotometric detection cell. The flow system was evaluated by studying the influence of 33 potential modifiers on the acetylthiocholine/acetylcholinesterase reaction. Substrate and enzyme solution of 280 iu/l and 1 mM, respectively, were prepared and the detector was operated at 410 nm. The modifiers were classified into three groups: (i) those substances which are strong inhibitors; (ii) those substances that effect the enzyme reaction only at concentrations greater than or equal to that of the substrate; and (iii) those substances which are modifiers at high concentration only.
Enzyme, activity Spectrophotometry

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

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

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

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

"Determination Of Sulfite In Wines By Gas Diffusion Flow Injection Analysis Utilizing Spectrophotometric PH-detection"
Anal. Chim. Acta 1997 Volume 337, Issue 2 Pages 125-131
L. G. Decnop-Weever* and J. C. Kraak

Abstract: A flow injection spectrophotometric method was developed for determining total sulfite in wines. The sample preparation procedure was carried out in a N2 atmosphere using a solution that had been degassed with N2. A wine sample of 25 mL was mixed with 50 mL of 10% ethanol and then 10 mL 2.5 M KOH was added. After 5 min, the following solutions were added in succession; 6.25 mL 2 M H2SO4 in 10% ethanol, 25 mL 2 M H2SO4 in 10% ethanol and sufficient 10% ethanol to give a total volume of 250 mL. A 40 µL portion of the resulting solution was immediately injected into a carrier stream (0.9 ml/min) of 1 M H2SO4 in 10% ethanol and passed through the donor channel of the gas diffusion cell. The SO2 diffused through the PTFE membrane and was collected in the acceptor stream (0.9 ml/min), 35 mg/l bromocresol green in 10% ethanol at pH 5.5. The absorbance of the acceptor stream was monitored at 620 nm. The method was calibrated for 1-20 mg/l sulfite and the detection limit was 0.1 mg/l. The method was applied to white, red and rose wines. The RSD (n = 6) for the peak heights was 0.7-1.5%. The recoveries of up to 7.5 mg/l sulfite from spiked wines were 96-109%. The sampling frequency was 120/h.
Sulfite Wine Sample preparation Spectrophotometry

"Kinetic And Thermodynamic Considerations In The Determination Of Aluminum Using Pyrocatechol Violet Implications For The Use Of 'kinetic-based' Determinations Of Metal Ions In Natural Systems"
Anal. Chim. Acta 1998 Volume 359, Issue 3 Pages 329-340
Stuart L. Simpson, Kipton J. Powell*, Nils H. S. Nilsson and Staffan Sj&ouml;berg

Abstract: Kinetic and thermodynamic factors associated using pyrocatechol violet (PCV) for the determination of total reactive Al or free Al [Al3++Al(OH)2++Al(OH)+2] were studied. The rate of reaction of Al with PCV (in MES buffer, pH 6.2) was strongly influenced by the presence of competing ligands. The rate of formation of Al(PCV)2 on the addition of Al3+ to a PCV-competing ligand mixture was: oxalate ≈ F- ≈ malonate > salicylate >> no competing ligand > citrate. A similar increase in the reaction rate relative to standards (i.e. no competing ligand) was observed for Al pre-equilibrated in humic waters and soil solution (at concentrations. above or below the Al-complexation capacity). The discrepancy in reaction rates may be ascribed to the inhibition through pH-induced hydrolysis of Al(III) in the absence of ligands (i.e. in standards) or to acceleration in the presence of naturally occurring ligands. It has serious implications for the use of kinetic-based FIA protocols for the determination of Al fractions or total Al in natural waters. Specifically, the (usually) slower reaction for Al(III) standards implies that measurements on systems containing organic ligands may overestimate the concentration. of free or total Al. Quantitative studies on the thermodynamics of the citrate-Al(III)-PCV system established that the attainment of equilibrium in the pH range 5.0 to 6.6 required ≈300 min. Thus, determination of total Al by FIA in systems containing this or closely related ligands is not feasible.
Aluminum, free Aluminum, total Spectrophotometry

"Preconcentration And Separation Of Inorganic Selenium Species On Activated Alumina"
Anal. Chim. Acta 1998 Volume 363, Issue 2-3 Pages 141-146
Krystyna Pyrzy&#324;ska, Przemys&#322;aw Drzewicz and Marek Trojanowicz

Abstract: A simple and convenient method has been developed for the speciation of inorganic selenium in aqueous solutions using alumina microcolumn. Both Se(IV) and Se(VI) are retained on the microcolumn in a widely pH range of solution. The successive gradient elution of pre-concentrated species with ammonia solution allows to differentiate between them. Se(VI) and Se(IV) were eluted with 1 mL of 1 mol L-1 NH3 and 6 mL of 4 mol L-1 NH3, respectively, and determined by graphite furnace atomic absorption spectrometry. The detection limit for Se(VI) is 0.80 µg mL-1 and for Se(TV) 49 ng L-1. The method has been applied to the speciation of inorganic selenium in natural water samples.
Selenium(IV) Selenium(VI) Environmental Spectrophotometry

"Simultaneous Determination Of Cobalt(II) And Nickel(II) In Water And Soil Samples With Sequential Injection Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 177-186
R. E. Taljaard and J. F. van Staden*

Abstract: The discontinuous nature of the sequential injection technique make it ideally suitable for kinetic determinations One of the advantages of kinetic analysis over equilibrium methods is the possibility of carrying out simultaneous determinations based on the different rates of their reactions with a common reagent. The different rates of the pseudo-first order dissociation of the citrate complexes of cobalt(II) and nickel(II) at pH 8.00 are used as a basis for the kinetic determination of these ions at trace levels in water and soil extracts The reactions are followed by measuring the absorbance of complexes of the metal ions with 4-(2-pyridylazo)resorcinol (PAR) which are formed in a subsequent rapid reaction. EDTA is added to mask the major interferences. The proposed system is fully computerized and is able to monitor Co(II) and Ni(II) in samples at a frequency of 11 samples per h with a relative standard deviation better than 1.2%. The detection limits are 0.14 and 0.20 mg/l for Ni(II) and Co(II), respectively.
Cobalt(II) Nickel(II) Environmental Environmental Sample preparation Spectrophotometry

"Optical Sensing Of Sulfite With A Phosphorescent Probe"
Anal. Chim. Acta 1998 Volume 374, Issue 1 Pages 1-9
Dmitri Papkovsky*, Marsha A. Uskova, Gelii V. Ponomarev, Timo Korpela, Sakari Kulmala and George G. Guilbault

Abstract: Spectral-luminescent properties and quenching behavior of the covalent conjugate of the platinum(II) complex of coproporphyrin-I and bovine serum albumin (PtCP-BSA) was studied. Quenching of phosphorescence by sulfite was studied in detail in an acidic range as a function of pH. Strong dynamic quenching of the phosphorescence by sulfite occurred at pH <4.0 which was attributed to the formation of sulfur dioxide. The quenching reached its maximal level at pH <1.5, Stern-Volmer quenching constants being ≤2000 M-1. A new flow injection system for the determination of sulfite was developed based on the PtCP-BSA conjugate immobilized on a preactivated Biodyne ABC membrane and placed in a flow-cell, with an acidic carrier buffer and fiber-optic phosphorescent detector. Such a solid-state phosphorescent probe is quenchable by sulfite and allowed rapid online detection of sulfite with a detection limit of ~10 µM Performance of the new system and possible interferences were studied.
Sulfite Phosphorescence Sensor

"Flow Injection Immunoassay Using OPA Derivatization"
Anal. Chim. Acta 1998 Volume 374, Issue 2-3 Pages 177-183
Jong Il Rhee, J&ouml;rg Hagedorn, Gerlinde Kretzmer, Thomas Scheper and Karl Sch&uuml;gerl*

Abstract: A flow injection immunoassay (FIIA) using ortho-phthalaldehyde (OPA) derivatization was developed for online monitoring of protein products in biotechnology processes. Recombinant tissue-type plasminogen activator (rt-PA) and its antibodies were used in these studies as a model system. The derivatization of rt-PA with OPA led to a lower detection limit (higher fluorescence intensity) and an increase of sensitivity (higher slope of calibration curve) for rt-PA compared with the method without OPA derivatization. The derivatization of rt-PA with OPA was also systematically characterized: influence of pH, derivatization time, OPA concentration. and sample volume on fluorescence intensity. Interferences caused by proteins were investigated with different washing buffer solutions A 0.1 M potassium phosphate buffer (PPB) solution containing 1 g L-1 polyethylene glycol (PEG) was found to be optimal for minimizing the interference with BSA in the measurement. Online monitoring for rt-PA is carried out on a simulated bioprocess in the range 0-20 µg mL-1. The data obtained showed good agreement with the conventional off-line enzyme linked immunosorbent assay (ELISA) data. The FIIA using o-phthalaldehyde (OPA) derivatization is a valuable tool for online monitoring of low concentration protein products in biotechnology production processes.
Protein, recombinant tissue-type plasminogen activator Immunoassay

"Use Of 4-(2-pyridylazo)resorcinol Or 2-(2-pyridylazo)-5-dimethylaminophenol As Chelating Agent For Determination Of Cadmium In Seawater By Atomic Absorption Spectrometry With Online Flow Injection Sorbent Extraction"
Anal. Chim. Acta 1998 Volume 376, Issue 3 Pages 305-311
Pi-Guey Su and Shang-Da Huang*

Abstract: A home-made automatic online flow injection sorbent extraction system for graphite furnace atomic absorption spectrometry (GFAAS) was used to determine Cd in seawater using octadecyl functional group (C18) bonded silica gel as sorbent, 4-(2-pyridylazo)resorcinol (PAR) or 2-(2-pyridylazo)-5-dimethylaminophenol (PADMAP) as chelating agent and methanol as eluent. The range of pH for the determination of Cd in seawater was 4.7-7.4 and 7.1-9.0 for using PAR and PADMAP as chelating agents, respectively. For the long-term stability studies, (PAR-Cd or PADMAP-Cd) are stable within the pH range 4.7-7.4 (for PAR) or 7.1-9.0 (for PADMAP) for 1 h at least. Sample volume of only 500-1000 µL was required to determine Cd in seawater. The simple calibration curve method was used and the detection limits of the determination of Cd in seawater were 4.0 and 1.7 ng L-1 for PAR and PADMAP as chelating agents, respectively. The sample throughput is 9-12 h-1. The accuracy and precision of the method were confirmed by the anal. of three kinds of certifie reference saline water.
Cadmium Sea Spectrophotometry

"Simultaneous Determination Of Traces Of Iron(II) And Iron(III) Using Differential Pulse Anodic Stripping Voltammetry In A Flow-through Configuration On A Glassy Carbon Electrode"
Anal. Chim. Acta 1998 Volume 376, Issue 3 Pages 325-330
J. F. van Staden* and M. C. Matoetoe

Abstract: Iron(II) and iron(III) complexes of pyrophosphate can be determined simultaneously at pH 9. The peak potentials used were -0.8 and 0.5 V for Fe(III) and Fe(II), respectively. Linear calibration plots over the range 10^-6-10-3 mol L-1 were obtained. Detailed iron-couple cyclic voltammetric studies, sample handling procedures, possible interferences and applications of the method to real samples are described. Detection limits of 10^-8 mol L-1 and a relative standard deviation of <4% (n = 14) were achieved at a concentration. of 1 x 10^-6 mol L-1 for both iron species.
Iron(2+) Iron(III) Electrode Voltammetry

"Alternative Use Of Flow Injection Analysis And The Combination Of Liquid Chromatography And Flow Injection Analysis For The Determination Of Total And Individual Bile Acid Concentrations In Serum"
Anal. Chim. Acta 1991 Volume 249, Issue 2 Pages 461-467
A. Membiela, F. L&aacute;zaro, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: The sample was passed through a Sep-Pak C18 cartridge and the bile acids were eluted with methanol. The total acid content was determined by flow injection analysis and was based on the oxidation of the acids, catalyzed by 3-α-hydroxysteroid dehydrogenase and NAD+, the reduced forms of which being monitored fluorimetrically. Samples with abnormal acid concentration. were analyzed for individual analytes on a column (20 cm x 4 mm) of Nucleosil C18 (10 µm) with methanol - 20 mM KH2PO4 (9:1) as mobile phase, pH 4.5, with detection at 460 nm (excitation at 340 nm). Recoveries by both methods were between 87.3 and 115.7%. The calibration graphs were rectilinear from 1 to 10 µg mL-1, and the coefficient of variation (n = 11) were between 2.7 and 3.0% for 4 µg mL-1 of each acid.
Bile acid Blood Serum LC Fluorescence

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

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

"Online Monitoring Of Galactoside Conjugates And Glycerol By Flow Injection Analysis"
Anal. Chim. Acta 1998 Volume 373, Issue 1 Pages 57-62
F&eacute;lix Am&aacute;rita Vegaa, Carlos G. N&uacute;&ntilde;ezb, Beate Weigelc, Bernd Hitzmannc and Juan C. Diaz Riccid,*

Abstract: A biosensor attached to a flow injection analysis (FIA) system was developed for the automatic determination of galactoside conjugates and glycerol. The biosensor was based on the enzymatic reaction of galactose oxidase (GalOD) using galactose, raffinose, lactose and glycerol as substrates. GalOD converts galactoside conjugates to galactohexodialdose conjugates and glycerol to glyceraldehyde with formation of hydrogen peroxide and consumption of oxygen. Variation of dissolved oxygen in the carrier was estimated utilizing an amperometric oxygen probe. The FIA system consisted in a multichannel peristaltic pump, an injection valve and an electronic transducer which were controlled by the CAFCA software. Stability of the enzyme and optimal working condition were investigated. Optimum pH for the immobilized enzymes under these experimental conditions was 7.4 and the enzyme retained 80% of the original activity after two months of use. Studies on the dynamical response of the biosensor showed that the elapsed time between two successive injections could be as short as 120 s without signal deterioration when the flow rate was 2 mL/min and 50 l of injection volume Sensitivity of the biosensor was higher for galactose followed by raffinose, lactose and glycerol. The sensor showed linear response between 0.2 and 2 mM for galactose, 0.5 and 6 mM for raffinose, 25 and 250 mM for lactose, and 2 and 200 mM for glycerol.
Glycerol Galactose Raffinose Lactose Galactoside conjugates Amperometry Sensor Electrode

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

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

"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

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

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

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

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

"Simultaneous Flow Injection Determination Of Chlorpromazine And Promethazine By Photochemical Reaction"
Talanta 1991 Volume 38, Issue 11 Pages 1227-1233
Danhua Chen, A. R&iacute;os, M. D. Luque de Castro* and M. Valc&aacute;rcel,

Abstract: Chlorpromazine (I) and promethazine (II) were simultaneously determined by irradiating flow injection manifolds with UV light; the method was based on the difference in the pH of the media where the photochemical conversion of I or II into a fluorescent product took place. The choice of the best-flow injection configuration and a mathematical model for solving the mixtures are discussed. Sample throughput was 30 to 40 h-1. The coefficient of variation were 2 to 4%. The method was used to determine I and II in pharmaceuticals preparations; results agreed well with expected values.
Chlorpromazine Promethazine Pharmaceutical Fluorescence

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

Abstract: Electrodes for Cl-, Br- and I- were constructed (preparation described) from Ag2 - AgCl or AgBr (1:1) and Ag2S - AgI (1:3); for F- a commercial electrode was used. By combining the electrodes and suppressor columns of AgCl and amalgamated Pb, the ions were simultaneously determined in a carrier stream (0.5 mL min-1) of e.g. 0.1 M HClO4 at pH 4.0. The calibration graphs were rectilinear down to 100, 5, 1 and 5 µM for Cl-, Br-, I- and F-, respectively. The reproducibility was 1% for the determination of the halides in eight water samples, the results agreed well with those obtained by three reference methods. Flow-through ion-selective electrodes were constructed from compressed pellets (8-10 mm thick, 13 mm diameter, 10 tons/cm2 pressure) of Ag2S/AgX (X = Cl-, Br- or I-) drilled longitudinally (1.5 mm diameter hole) to be suitable for use in flow injection analysis. A column of AgCl (5.5 cm long, 2-3 mm internal diameter) was included in the Cl- electrode manifold to remove interferences from 10^-4 M Br- and 3 x 10^-5 M I- and S2-. A column of amalgamated lead (2-3 cm long, 2-3 mm internal diameter) was used in the Br--electrode manifold to remove interference from 2 x 10^-5 M I-, 3 x 10^-5 M S2- and 7 x 10^-4 M Cl-. These columns and the addition of ascorbic acid were not required when I- was determined with the iodide electrode. The carrier stream was 0.1 M sodium perchlorate (pH 4) at a flow-rate of 0.5 mL/min. The sample pH could be 4-7. Simultaneous determination of Cl- and I-, Cl-, I- and Br-, and Cl-, I-, Br- and F- ions was possible with combinations of the corresponding electrodes and columns in series and/or parallel in specially designed manifolds. Calibration plots were linear, with almost theoretical slopes, down to 10^-6 M I-, 5 x 10^-6 M Br-, 10^-4 M Cl- and 5 x 10^-6 M F-, with precision better than 1%. Sampling rates for single-ion determinations were 72, 102, 90 and 80 per h for the one-, two-, three- and four-electrode systems respectively. Determinations of these ions in water samples by the recommended procedure and by established batch methods showed no significant difference at the 95% confidence limits in a paired comparison t-test.
Chloride Bromide Iodide Fluoride Environmental Electrode Electrode Electrode Electrode

"Silver(I)-selective Membrane Electrodes Based On Sulfur-containing Podands"
Talanta 1997 Volume 44, Issue 7 Pages 1291-1298
Sarah Chung, Wantae Kim, Sung Bae Park, Dae Yeon Kim and Shim Sung Lee*

Abstract: Podands containing two S atoms in the ether chain and aromatic or lipophilic end groups (structures shown, syntheses described) were used to prepare Ag+-selective polymeric membrane electrodes. Membranes contained 30.9-33% PVC, 60-64.3% di-isodecyl adipate 1-6% podand and, optionally, potassium tetrakis-(4-chlorophenyl)borate. Measurements were made in 0.05 M Tris buffer of pH 9 with the following potentiometric cell: Ag/AgCl/4 M KCl saturated with AgClvertical barTris buffervertical barsamplevertical barmembranevertical bar 1 mM AgNO3/AgCl/Ag. The electrodes showed good selectivity for Ag over Cd2+, Pb2+, Cu2+, Hg2+ and other heavy metal ions, and alkali and alkali earth metal ions. They were stable for >1 month. For use in a FIA system, the RSD (n = 5) for 1 mM Ag+ was 0.7%. Detection limits were 0.6-2.2 µM. Calibration graphs are shown. Some podands, acyclic polyethers, were utilized as membrane active components to prepare Ag+-selective polymeric membrane electrodes. The thiapodand-based electrodes exhibited considerable selectivity toward Ag+ over other heavy metal ions including Cd2+, Pb2+, Cu2+ and Hg2+. Also, good selectivity over alkali and alkali earth metal ions were observed, Response slopes, pH effects; response time, and signal baseline return of the sensor systems were studied in static mode and/or in a flow injection system. The Ag+ -selectivity was explained by the soft-soft interaction of the Ag+ ion with the sulfur donor atoms as well as the stacking interaction between aromatic end groups of the host molecule on complexation. (C) 1997 Elsevier Science B.V.
Silver(I) Electrode Electrode Potentiometry

"Flow Injection Spectrophotometric Determination Of Boron In Ceramic Materials"
Talanta 1998 Volume 45, Issue 5 Pages 835-842
S. Sanchez-Ramos, M. J. Medina-Hern&aacute;ndez and S. Sagrado*

Abstract: A flow injection spectrophotometric method for the determination of boron in ceramic materials is described. The method is based on spectrophotometric measurement of the decrease in the pH produced by the reaction between boric acid and mannitol in the presence of an acid-base indicator. A bichannel FI (flow injection) manifold in which the sample solutions were injected into deionized water (at pH 5.4) and the stream was later merged with the reagent stream (a mannitol solution containing 1 x 10^-4 mol L-1 bromocresol green at pH 5.4), was used. Transient signals were monitored at 616 nm. A theoretical model which describes the dependence between the absorbance values and boric acid concentration. is presented. The model predicts a nonlinear dependence between the absorbance or increment in absorbance and the boric acid concentration. In contrast, the model predicts a linear dependence between the inverse of the absorbance values and the boric acid concentration. The calibration graphs (1/A vs. µg mL-1 B2O3) were linear over the range 1-30 µg mL-1 of B2O3. The relative standard deviations were 0.7 and 0.4% for 4 and 8 µg mL-1 of B2O3, respectively. The limit of detection was 0.02 µg mL-1 of B2O3 (3s criterium). The method was used to determine boron in nine ceramic materials with very different nominal boron compounds. The results were compared with those obtained using a potentiometric titration method as reference method. No significant differences (at 95% probability level) were found between the proposed and reference methods. The method is rapid, reliable, precise and free of interferences.
Boron Ceramic Spectrophotometry

"Selective Determination Of Nickel(II) And Cobalt(II) By Flow Injection Analysis And Adsorptive Cathodic Stripping Voltammetry On A Wall Jet Mercury Film Electrode"
Talanta 1998 Volume 46, Issue 5 Pages 1137-1146
A. Economou* and P. R. Fielden

Abstract: Ni(II) and Co(II) were determined simultaneously by adsorptive cathodic stripping voltammetry (AdCSV) in a computerized flow injection system. The working electrode was a glassy C disk that was fitted in a wall-jet flow cell. The electrode was initially electrochemically coated with a Hg film at -1.0 V by injecting a Hg(II) solution in the flow stream. Then, the sample, containing Ni(II) and Co(II), was mixed online with a solution containing dimethylglyoxime (DMG) at pH 9 to selectively complex the metal ions and was injected in the flow system. After a number of successive injections during which accumulation took place under controlled potentiostatic conditions, the surface-bound complexes were reduced in NH3 buffer at pH 9 by a cathodic scan of the potential of the working electrode in the square wave mode and the current-potential response was recorded. Finally, the electrode surface was regenerated by a potentiostatic polarization at -1.4 V in the same buffer. The app. could be easily converted for continuous-flow accumulation to increase the sensitivity; in this mode of operation, instead of performing discrete injections, the sample was continuously pumped through the cell. Various parameters associated with the pre-concentration, stripping and regeneration steps were optimized for the determination of Ni(II) and Co(II). The selectivity of the method was demonstrated for the anal. of high purity Fe; the accuracy for the determination of Ni(II) and Co(II) was 11 and 3%, respectively while the coefficient of variation was 10 and 8%, respectively.
Nickel(II) Cobalt(II) High purity Voltammetry Voltammetry Electrode Electrode

"Effect Of Pre-treatment Of Platinum For Modified Platinum Wire Glucose Oxidase Amperometric Electrodes"
Analyst 1989 Volume 114, Issue 1 Pages 29-32
S. K. Beh, G. J. Moody and J. D. R. Thomas

Abstract: The cited electrodes, which are based on Pt wire (100 µm diameter), were pre-treated by: (i) oxidation in an electric furnace under atmospheric pressure at 900°C for 5 h; and (ii) platinization involving reduction of hexachloroplatinate galvostatically at 450 nA for 2 h in Pb acetate solution Electrodes prepared by anodization at 2.5 V vs. Ag - AgCl in H2SO4 were studied for comparison. Each electrode was then silanized before immobilization of the enzyme. The electrodes were applied in the determination of glucose by flow injection analysis. The optimum conditions were: sample size 0.5 ml, flow rate 2.0 mL min-1 and pH 7.0. The response time of each electrode was 25 s; the electrode obtained by (ii) gave the widest rectilinear response, viz, 5 µM to 30 mM. The lifetimes of the systems during routine use were 10 days.
Glucose Electrode Electrode Amperometry

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

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

"Determination Of Diphenhydramine Hydrochloride By Flow Injection With Bromophenol Blue And Turbidimetric Measurement"
Analyst 1990 Volume 115, Issue 6 Pages 855-858
J. Martinez Calatayud, A. Sanchez Sampedro and S. Navasquillo Sarrion

Abstract: Powdered tablets were mixed with water, the mixture was filtered and diluted to volume A 210 µL aliquot of the solution was injected into a carrier - reagent stream (2.69 mL min-1) of 1.19 mM bromophenol blue (pH adjusted to 1.2 with HCl). The turbidity was measured spectrophotometrically at 650 nm. The calibration graph was rectilinear for 50 to 230 ppm of diphenhydramine hydrochloride. The coefficient of variation (n = 20) was 0.3% and the injection rate was 51 samples h-1. The study of a number of diphenhydramine-dye systems was carried out in order to determine the most suitable precipitate for the turbidimetric determination of diphenhydramine using flow injection (FI). The reagent selected was Bromophenol Blue. The chemical and FI variables were optimized. The calibration graph was linear over the concentration range 50-230 p.p.m. of diphenhydramine hydrochloride. A number of interfering substances were also investigated.
Diphenhydramine Pharmaceutical Spectrophotometry Turbidimetry

"Flow Apparatus For Monitoring Dissolution Rate Curves Using Ion-exchange Resins. 1. Phosphite Dissolution Rate Curve"
Analyst 1990 Volume 115, Issue 6 Pages 765-769
N. P. Evmiridis and E. D. Economou

Abstract: The system comprised a carrier stream of water or aqueous acidic solution, flowing through a cell containing a glass pH micro-electrode, and a syringe containing Dowex HGR-W2 ion-exchange resin, for exchange of metal ions for H+ for subsequent injection into the carrier stream. Two injections were made per sample, one before and one after ion exchange. The calibration graph was rectilinear for pH 1 to 5. The method was reasonably accurate, reproducible, rapid and simple. The method can be applied to determine a wide range of metal ion concentration. and can be made selective for one ion in the presence of others by pre-complexation. The method is applicable to study dissolution rate curves, and was applied to the dissolution of CaCO3 in H3PO4 as an example.
Calcium carbonate Inorganic compound

"Determination Of Chlordiazepoxide By Zinc Or Cadmium Reduction In A Continuous System Followed By Atomic Absorption Spectrometric Detection"
Analyst 1990 Volume 115, Issue 7 Pages 943-949
Rosa Montero, Mercedes Gallego and Miguel Valc&aacute;rcel

Abstract: An indirect flow injection analysis - AAS method is described for determination of chlordiazepoxide (I). A portion of powdered tablets (15 to 20 mg of I) was dissolved in ethanol, with stirring, at 40°C to 50°C for 1 h. The solution was adjusted to pH 3.5 to 5.0 with 10 mM HCl and diluted to volume A portion (200 µL) was injected into a carrier stream (H2O), which was passed through a redox column (4.5 or 8.5 cm x 1.8 mm) of Cd or Zn granules (0.5 to 1.2 mm), Cu-coated Cd granules or amalgamated Zn granules. The metal in the eluate was determined by AAS, the peak being compared with that obtained by injecting a water blank (adjusted to the same pH as the sample). From 2 to 25 µg mL-1 of I could be determined, with coefficient of variation of 1.1 to 2.8%. The sampling rate was 150 h-1. Recoveries from commercial formulations were 97.3 to 102.1%.
Chlordiazepoxide Spectrophotometry

"Use Of Photochemical Reactions In Flow Injection: Determination Of Oxalate In Urine"
Analyst 1990 Volume 115, Issue 12 Pages 1549-1552
Luis E. Leon, Angel R&iacute;os, M. D. Luque de Castro and Miguel Valc&aacute;rcel

Abstract: The use of photochemical reactions in flow injection (FI) is reported. The irradiation of an FI reactor with a suitable source facilitates the development of the iron(III)-oxalate reaction, allowing the amperometric determination of the anion in the range 1.0-13.0 µg mL-1, with a relative standard deviation of 1.1% and a sampling frequency of 40 h-1. The proposed method was applied successfully to the determination of oxalate in urine samples. Urine (5 ml) was adjusted to pH 5.0 to 5.2 with acetic acid or aqueous NH3 solution, shaken with 0.7 M CaCl2 (2 ml) and kept at 4°C for 2 h, and the ppt. was collected, washed with saturated CaCl2 solution and dissolved in 0.1 M H2SO4. The solution was injected into a carrier stream of 0.1 M H2SO4 and mixed with a reagent stream of 0.1 M H2SO4 containing Fe(III) (both at 0.5 mL min-1) at 40°C in a reactor (1 m x 0.8 mm). The reaction mixture was irradiated before detection at a vitreous C electrode with an auxilliary electrode of the same material vs. Ag - AgCl. The calibration graph was rectilinear from 1 to 13 µg mL-1 of oxalate (I) and the detection limit was 0.64 µg mL-1. Recoveries were 93 to 98% and the coefficient of variation (n = 11) was 2.6 and 1.1% for 1.3 and 9.4 µg mL-1 of I. Citrate and tartrate interfered seriously; malate, picrate, salicylate, and barbituric and uric acids did not.
Oxalate Urine Amperometry Electrode

"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

"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

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

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

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

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

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

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

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

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

"Indomethacin Ion-selective Electrode Based On A Bis(triphenylphosphine)iminium - Indomethacin Complex"
Analyst 1991 Volume 116, Issue 8 Pages 811-814
Ralph Aubeck, Christoph Br&auml;uchle and Norbert Hampp

Abstract: For preparation of the cited electrode, a membrane was prepared (described) from a mixture containing 4.6% of indomethacin (I) - bis(triphenylphosphine)iminium complex, 67.1% of 2-nitrophenyl octyl ether and 28.3% of PVC dissolved in THF. The membrane was attached to a PVC electrode body containing an internal Ag - AgCl junction and 3 M NaCl as internal electrolyte. The electrode was used to determine I in a flow cell under continuous-flow conditions (1 mL min-1) at pH 7.0. The calibration graph was rectilinear from 50 µM to 1 mM I, with a detection limit of 6.4 µg mL-1 of I. There was strong interference by inorganic anions such as IO4- and ClO4- and the electrode could be used to determine from 1 µM to 0.01 M ClO4- (detection limit 0.6 µM-ClO4). Results compared well with those by spectrophotometry.
Indomethacin Electrode Electrode

"Amperometric Enzyme Electrode For Theophylline"
Analyst 1991 Volume 116, Issue 10 Pages 997-999
Joseph Wang, Eithne Dempsey, Mehmet Ozsoz and Malcolm R. Smyth

Abstract: An amperometric biosensor for theophylline, based on the recently isolated enzyme theophylline oxidase, is described. The enzyme is entrapped, together with a ferricytochrome C cofactor, within a polymeric (Nafion) coating. The anodic detection (at +0.4 V versus Ag-AgCl) is facilitated by the addition of a redox-mediating hexacyanoferrate(III) ion. The influence of various experimental variables is described. The limit of detection is 2 x 10^-6 mol L-1 theophylline, with linearity prevailing up to 3 x 10^-4 mol L-1. The fast response and wash times permit rapid flow injection measurements, with a frequency of 180 samples h-1 and a relative standard deviation of 3.0-4.0%. Prospects of using this electrode for clinical diagnostics are discussed. The cited enzyme electrode was prepared by applying a 5 µL portion of a 1% Nafion - theophylline oxidase - 30 µM-ferricytochrome C mixture (details given) to the surface of a Pt-disc electrode. The layer was dried at 35°C using a heat gun, a second 5 µL portion of the mixture was added and the resulting film was covered with 5 µL of ethanolic 1% Nafion solution Theophylline (I) was determined at +0.4 V vs. Ag - AgCl in the presence of 1 mM hexacyanoferrate(III) and at pH 5.4 to 6.9. The calibration graph was rectilinear for 0.3 mM I; the detection limit was 2 µM. Under flow injection conditions, the sample throughput was 180 h-1, the response was rectilinear for 3 mM I and the detection limit was 10 µM. Glucose, paracetamol and caffeine showed negligible interference.
Theophylline Amperometry Electrode Electrode Sensor

"Poly(vinyl Chloride) Matrix Membrane Electrodes For Manual And Flow Injection Determination Of Metal Azides"
Analyst 1992 Volume 117, Issue 11 Pages 1683-1689
Saad S. M. Hassan, Fatma M. El Zawawy, Sayed A. M. Marzouk and Eman M. Elnemma

Abstract: The cited electrodes using Fe(II) and Ni(II) bathophenanthroline - azide ion-pair complexes as ion exchangers and 2-nitrophenyl phenyl ether as plasticizing solvent mediator exhibited near-Nernstian response for 0.1 M to 35 µM N3-, a wide working pH range of 6 to 12, a fast response time (40 s), long-term stability (one month) and reasonable selectivity for N3- over many common anions. Interference from ClO4-, ClO3- and NO3- was tolerated by appropriate ion-exchange separation. Coefficients of variation of 0.4% and recoveries of 99.4% were achieved for 0.8 µg mL-1 of soluble azides. Insoluble metal azides were determined similarly after solubilization with alkaline EDTA solution. The effects of pH and foreign ions were also investigated. The results compared well with those obtained by other methods. The method was applied to the determination of the solubility products of some sparingly soluble salts and the monitoring of azides in primer mixtures. Novel poly(vinyl chloride) matrix membrane electrodes for the azide ion are developed, electrochemically evaluated and used for manual and flow injection determinations of soluble and insoluble metal azides. These electrodes incorporate iron(II) and nickel(II) bathophenanthroline-azide ion-pair complexes as ion exchangers and 2-nitrophenyl Ph ether as a plasticizing solvent mediator. The electrodes exhibit (i) near-Nernstian response for 1 x 10^-1 - 3.5 x 10^-5 mol L-1 N3- with an anionic slope of 56-57 mV decade-1 of concentration.; (ii) a wide working range of pH (6-12); (iii) a fast response time (<40 s); (iv) long-term stability (>1 mo); and (v) reasonable selectivity for N3- over many common anions. Interference caused by ClO4-, ClO3- and NO3- can be easily tolerated by appropriate ion-exchange separation Determination of as little as 0.8 µg mL-1 of soluble azides shows an average recovery of 99.4% and a mean standard deviation of 0.4%. Insoluble metal azides can be similarly determined after prior solubilization with alkaline EDTA solution Methods for measuring the solubility products of some sparingly soluble metal azides and for monitoring the concentration. level of azide in primer mixtures are described. Significant advantages in terms of simplicity, sensitivity, selectivity and accuracy are offered by these electrodes.
Azide ion Electrode

"Spectrophotometric Determination Of Tannin In Tanning Effluent With A Flow Injection System"
Analyst 1995 Volume 120, Issue 4 Pages 1185-1188
Valderi L. Dressler, Enio L. Machado and Ayrton F. Martins

Abstract: A 50 mL portion of tanning effluent was acidified with 5% HCl to pH 2, heated to boiling and allowed to cool. The pH of the solution was adjusted to 11 with 5% NaOH and the solution was re-boiled for 5 min, allowed to cool and filtered. The filtrate was adjusted to pH 6 with 5% HCl and diluted to 100 mL with water. A 200 µL portion of the resulting solution was injected into an aqueous carrier stream (6 ml/min) and merged with a stream (2 ml/min) of 2% NaOH and then with a stream (1 ml/min) of Folin-Ciocalteu reagent of pH 4-5 (1:4). The mixture passed through a 150 cm reaction coil and the absorbance was then measured at 670 nm. A diagram of the manifold used is given. The calibration graph was linear from 5-100 mg/l of tannin; the detection limit was 1.04 mg/l. The RSD (n = 10) was 2.9%. The throughput was 250 samples/h.
Tannins Polyphenols Process liquor Spectrophotometry

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

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

"Simultaneous Spectrophotometric Determination Of Calcium And Magnesium In Mineral Waters By Means Of Multivariate Partial Least-squares Regression"
Analyst 1997 Volume 122, Issue 7 Pages 639-643
F. Blasco, M. J. Medina-Hern&aacute;ndez, S. Sagrado and F. M. Fern&aacute;ndez

Abstract: The use of multivariate calibration methods in the simultaneous spectrophotometric determination of Ca and Mg was investigated. The determination was based on the reaction of Ca and Mg with Methylthymol Blue at pH 11. Both batch and flow injection modes were employed for the reaction. Partial least squares regression was used as the calibration method and was applied to the absorbance data obtained. The optimized method was applied to mineral water. The RSD (n = 7) were 1.6% for magnesium and 2.6% for calcium. The results obtained agreed with those obtained by complexometry and ICP-AES. A method for simultaneous spectrophotometric determination of calcium and magnesium in mineral waters using multivariate calibration methods is proposed. The method is based on the development of the reaction between the analytes and Methylthymol Blue at pH 11. Two operational modes were used: static (spectral information) and flow injection (FI) (spectral and kinetic information). The selection of variables was studied. A series of synthetic solutions containing different concentrations of calcium and magnesium were used to check the prediction ability of the partial least-squares models. The method was applied to the analysis of mineral waters and the results were compared with those obtained by complexometry. No significant differences at the 95% confidence level were found. The proposed method is simple, accurate and reproducible, and it could be easily adapted as a portable (static mode) or automatic (FI) method.
Calcium(2+) Magnesium(II) Mineral Spectrophotometry

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

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

"Simultaneous Determination Of Phosphate And Silicate In Waste Water By Sequential Injection Analysis"
Analyst 1997 Volume 122, Issue 10 Pages 1033-1038
F. Mas-Torres and V. Cerd&agrave;

Abstract: The method is based of the formation of yellow vanadomolybdophosphate and molybdosilicate, respectively, in addition to the use of large sample volumens. The mutual interference between both analytes was eliminated by selection of the appropriate acidity and by sample segmentation with oxalic acid. The calibration graph for phosphate and silicate is linear up to 12 mg L-1 P and 30 mg L-1 Si, respectively. The detection limits are 0.2 and 0.9 mg l-1. The method provides a throughput of 23 samples h-1 with a relative standard deviation of < 1.4% for phosphate and < 4% for silicate. The method was found suitable for the determination of these species in waste water samples. A sequential injection analysis system for the simultaneous determination of phosphate and silicate in waste water is proposed. The method is based on the formation of yellow vanadomolybdophosphate and molybdosilicate, respectively, in addition to the use of large sample volumes. The mutual interference between both analytes was eliminated by selection of the appropriate acidity and by sample segmentation with oxalic acid. The calibration graph for phosphate and silicate is linear up to 12 mg L-1 P and 30 mg L-1 Si, respectively. The detection limits are 0.2 mg L-1 P and 0.9 mg L-1 Si. The method provides a throughput of 23 samples h-1 with a relative standard deviation 1.4% for phosphate and 4% for silicate. The method was found to be suitable for the determination of these species in waste water samples.
Phosphate Silicate Waste Spectrophotometry

"Flow Injection Determination Of Anionic Surfactants With Cationic Dyes In Water Bodies Of Central India"
Analyst 1998 Volume 123, Issue 8 Pages 1691-1695
Rajmani Patel and Khageshwar Singh Patel

Abstract: A new, simple and specific flow injection analysis (FIA) procedure for the determination of anionic surfactants, viz., sodium lauryl sulfate (SLS), sodium dodecyl sulfonate, sodium hexadecyl sulfonate and sodium dodecyl benzenesulfonate, with cationic dyes, viz., Brilliant Green, Malachite Green, Methylene Blue, Ethyl violet and Crystal Violet, in water bodies, viz., ponds, tube wells, rivers and municipal wastes, of central India (east Madhya Pradesh) is described. It is based on the precipitation of the cationic dyes with the anionic surfactant due to formation of an ion-associated species within the pH range 5.5-8.0. The apparent molar absorptivity of the ion-associated species formed with various anionic surfactants and cationic dyes is in the range (0.60-1.50) x 104 L mol-1 cm-1 at λmax 590-665 nm. Among them, the pair BG+-LS- was selected for detailed investigation. The detection limit (amt. causing absorbance >3s) of the method with BG is 100 ppb SLS and the sample throughput is 50 h-1. Optimization of FIA and the anal. variables in the precipitation and determination of SLS with BG is described. The method is free from interferences from almost all ions which are commonly present with the surfactant. The proposed method was applied to the mapping of SLS pollution levels in the various water bodies. All surface waters and municipal waste waters and some ground waters lying near the sources were found to be contaminated with SLS beyond permissible limits.
Surfactants, anionic Sodium lauryl sulfate Sodium dodecyl sulfonate Sodium hexadecyl sulfonate Sodium dodecylbenzenesulfonate Ground Surface Pond Well River Waste Spectrophotometry

"Photochemically Induced Fluorimetric Detection Of Tianeptine And Some Of Its Metabolites. Application To Pharmaceutical Preparation"
Analyst 1998 Volume 123, Issue 11 Pages 2267-2270
Mihaela Bulaceanu-Mac Nair, Jean-Jacques Aaron, Patrice Prognon and Georges Mahuzier

Abstract: The photochem. induced fluorescence (PIF) properties of tianeptine and some of its metabolites were investigated in acidic (pH 2.3) water-alcohol mixtures at room temperature Two PIF methods were developed, including bulk solution and flow injection analysis (FIA). Linear calibration plots were established over a concentration. range of more than one order of magnitude. Limits of detection ranged from 15 ng mL-1 for FIA-PIF to 25 ng mL-1 in bulk solution The RSDs were between 3 and 5%. The PIF methods were applied to the determination of tianeptine in a pharmaceutical preparation with recoveries varying from 96 to 106% in bulk solutions and from 98 to 106% for FIA-PIF.
Tianeptine Tianeptine, metabolites Pharmaceutical Fluorescence

"Chelating Resins For Online Flow Injection Preconcentration With Inductively Coupled Plasma Atomic-emission Spectrometry"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 6 Pages 509-518
Xiarou Wang and Ramon M. Barnes

Abstract: A poly(dithiocarbamate) (PDTC) and a methylcarboxylated poly(ethylenimine) - poly(methylenepolyphenylene) isocyanate (CPPI) chelating resin were evaluated for the online pre-concentration. of 22 elements, with subsequent elution and detection by ICP-AES. The effect of pH on recovery of elements and of parameters, such as column length and diameter, which affect the dispersion of the analyte zone were studied. The PDTC resin works effectively at pH 8 to 10, whereas the CPPI resin chelated successfully at pH 5 to 6. Some elements could be pre-concentrated on one resin only. The PDTC resin was applied in the determination of Cu and Zn in natural and drinking water. Recovery of Cu was 98% at 20 and 50 ng mL-1, and the coefficient of variation (n = 11) was ~3% for 100 ng mL-1 of Cu.
Copper Zinc Environmental Water Spectrophotometry

"Flow Injection Online Sorption Separation And Preconcentration With A Knotted Reactor For Electrothermal Atomic Absorption Spectrometric Determination Of Lead In Biological And Environmental Samples"
J. Anal. At. Spectrom. 1997 Volume 12, Issue 4 Pages 459-464
XIU-PING YAN and FREDDY ADAMS

Abstract: Fish muscle was digested with 65% (w/w) HNO3, the digest was heated with 70% (w/w) HClO4 in a PTFE pressure vessel, the product was evaporated to near-dryness, and the residue was dissolved in water. Soil or sediment was digested with 40% (w/w) HF plus 65% HNO3, the digest was heated with 70% HClO4 in a PTFE pressure vessel, and the product was diluted with water. Diagrams of the flow injection manifold are presented; it incorporated a laboratory-made PTFE knotted reactor (100 cm x 0.5 mm i.d.) on the walls of which the Pb - diethyl phosphorodithioate complex was sorbed at pH 0.5-3.5 before elution with 35 µL of ethanol and transport to a pyrolytically coated GF without platform. The determination was carried out at the same time as the subsequent pre-concentration cycle. An enhancement factor of 125 was achieved, and the detection limit for Pb was 4.8 ng/l. The RSD (n = 11) at 0.5 µg/l of Pb was 2.1%. The results for standard reference materials agreed well with the certified values.
Lead Environmental Marine Environmental Sample preparation Spectrophotometry Sample preparation

"Determination Of Aqueous Fluoride With A Helium Microwave-induced Plasma And Flow Injection Analysis"
Anal. Chem. 1989 Volume 61, Issue 7 Pages 674-677
J. M. Gehlhausen and John W. Carnahan

Abstract: The sample solution is introduced directly or in 0.5 mL increments into a CETAC (Ames, IA) ultrasonic nebulizer, which supplies the He microwave-induced plasma (modified TM010 cavity; demountable silica torch; 500-W microwave generator at 2.45 GHz). The F emission is measured at the 685.6-nm (I) line. Although detection limits are 36 and 4 ppm for flow injection and direct nebulization, respectively, of test solution containing 1% of HNO3, flow injection is preferred because extended direct nebulization of aqueous F- causes memory effects. The calibration graph is curvilinear. The highest signals are obtained at pH~0.7. The F- signal is enhanced in the presence of Cu, Zn, K, Li and Na, and suppressed by Al; reasons for the effects are suggested. The determination of aqueous fluoride by flow injection analysis (FIA) with a helium microwave-induced plasma (He-MIP) is described. This system operates at 500 W and utilizes a modified TM010 resonator cavity with a demountable plasma torch. Both direct nebulization and FIA in conjunction with ultrasonic nebulization (USN) were investigated. FIA was found to be the most reliable method because extended nebulization of aqueous fluoride was found to cause memory effects. Detection limits for aqueous fluoride of 35 and 4 ppm were observed for FIA and direct USN, respectively. The interference effects of pH and selected elements were also studied.
Fluoride Spectrophotometry

"Flow Injection Analysis And Real-time Detection Of RNA Bases By Surface-enhanced Raman Spectroscopy"
Anal. Chem. 1990 Volume 62, Issue 18 Pages 1958-1963
Fan Ni, Rongsheng Sheng, and Therese M. Cotton

Abstract: Surface-enhanced Raman scattering (SERS) spectroscopy has been successfully interfaced with a flow injection analysis system to detect RNA bases in real time. Four of the major base components of RNA, uracil, cytosine, adenine, and guanine, were introduced into the flow injection system and were mixed with a Ag sol prior to SERS measurements. Several experimental parameters including pH, temperature, flow rate, and tubing materials were examined, and their impact on the SERS spectra is presented here. The feasibility of interfacing flow injection based SERS detection methods with liquid or high performance liquid chromatography for the detection of individual components in a complex mixture is also assessed.
Bases, RNA Raman HPLC

"Photometric Determination Of Acidity Constants By The Flow Gradient Technique Without PH Measurements"
Anal. Chem. 1990 Volume 62, Issue 20 Pages 2237-2241
Juliana Marcos, Angel Rios, and Miguel Valcarcel

Abstract: A simple photometric method for the determination of acidity constants without pH measurements is proposed. It is based on the establishment of a pH gradient in a flow system which is created by means of a flow gradient. The proposed method thus avoids other less accurate procedures for the establishment of pH gradients. Large pH gradients can be maintained over long periods. The acidity constants of various compounds were determined automatically from different parameters of the absorbance-time recordings. The proposed method allows more than one acidity constant for the same compound to be determined. The accuracy of the method is between 0.9% and 5.3%, in terms of relative standard deviation, and ±0.1 and ±0.4 in terms of confidence intervals.
Acidity, constants

"Determination Of Sub-nanomolar Levels Of Iron(II) And Total Dissolved Iron In Seawater By Flow Injection Analysis With Chemiluminescence Detection"
Anal. Chem. 1991 Volume 63, Issue 9 Pages 893-898
Virginia A. Elrod, Kenneth S. Johnson, and Kenneth H. Coale

Abstract: The flow injection manifold used was similar to that described previously (Sakamoto-Arnold and Johnson, ibid., 1987, 59, 1789) for Co in seawater with the addition of a column containing 8-hydroxyquinoline (I) on Fractogel. Seawater was collected in acid-washed polyoxyethylene bottles and acidified to pH 5.5. The sample was drawn through a PTFE filter (0.45 µm) and pumped (1.1 mL min-1) on to the I column for 4 min. The injection valve was switched to the 'elute' position and the Fe was eluted from the column with 75 mM HCl (1.1 mL min-1) for 1 min. The eluate stream merged with the 1 mM brilliant sulfoflavin stream (pH 8.3; 2.3 mL min-1) and then with the 2% H2O2 straem (2.3 mL min-1) before entering the flow cell. The flow cell comprised a clear PVC tube (50-cm coil) in a grey PVC housing maintained at -20°C. Light generated by the chemiluminescent reaction was detected by a photomultiplier tube connected to a photometer and a computer. Other metals did not interfere at concentration. expected in seawater. Detector response was rectilinear from 1 to 1000 nM Fe(II). The detection limit was 0.45 nM Fe(II). Calibration graphs were rectilinear at 2.5 nM Fe(II) only if peak areas were measured. Results agreed well with the certified values for reference materials.
Iron(2+) Iron Sea Chemiluminescence

"Chemiluminescence From The Reaction Of Chloroauric Acid With Luminol In Reverse Micelles"
Anal. Chem. 1991 Volume 63, Issue 20 Pages 2348-2352
Imdadullah, Terufumi Fujiwara, and Takahiro Kumamaru

Abstract: A flow injection procedure for the determination of trace Au in CHCl3 was developed, based on the chemiluminescence reaction of tetrachloroaurate(III) (1 mg mL-1) with luminol in a reversed micellar system of aqueous 0.2 M Na2CO3 solution (pH 11.5) with 0.01 M hexadecyltrimethylammonium chloride in CHCl3 - cyclohexane (6:5). Sample (90 µL) and reagent solution (100 µL) were injected simultaneously into carrier and reagent streams of CHCl3 (2 mL min-1) for reaction in a coiled flow cell (70 µL) at 4 mL min-1 and luminescence detection. Black opaque tubing was used between the injection valve and the reaction flow cell. The detection limit was 10 pg mL-1 of Au. The calibration graph was rectilinear from the detection limit to 1 ng mL-1 and from 1 ng mL-1 to 1 µg mL-1. The coefficient of variation was 3%.
Gold Chemiluminescence

"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

"Role Of Electron-donating/withdrawing Character, PH And Stoichiometry On The Chemiluminescent Reaction Of Tris-(2,2'-bipyridyl)ruthenium(III) With Amino-acids"
Anal. Chem. 1992 Volume 64, Issue 2 Pages 166-170
Stephen N. Brune and Donald R. Bobbitt

Abstract: The post-column detection of amino-acids by their chemiluminescent reaction with electrogenerated tris-(2,2'-bipyridyl)ruthenium(II)I (I) is described. Separation is carried out on a column (25 cm x 4.6 mm) of Partisil 10 SCX connected to the detection cell via a mixing tee. The detection cell consists of a small glass coil to which I, generated at 0.89 V vs. Ag wire from tris-(2,2'-bipyridyl)ruthenium(II), is delivered. For application to gramicidin D digest, the mobile phase (1 mL min-1) was 1 mM Na2SO4 (pH 2.5) and this was adjusted post-column to pH 10 with 0.05 M boric acid. Response was rectilinear over two orders of magnitude for leucine. Detection limits for serine and leucine were 135 and 3 pmol, respectively. The presence of electron-withdrawing groups on the α-carbon of the amino-acid decreases chemiluminescence and electron-donating groups increase chemiluminescence. A post-column chemiluminescent technique for the detection of underivatized amino acids using electrogenerated tris(2,2'-bipyridyl)ruthenium(III) is described. The reaction chemical has been investigated, and it has been shown that the electron withdrawing/donating character of the R group attached to the α-carbon of the amine influences the chemiluminescent efficiency of the reaction. Stoichiometric studies conducted on four amines produced a mole ratio of 2:1, ruthenium:amine. At optimum reaction conditions the relative intensities of the primary amino acids tested varied by a factor of 55, with serine yielding the lowest chemiluminescence and leucine yielding the highest chemiluminescence. Detection limits for serine and leucine have been calculated to be 135 and 3 pmol, respectively, at a S/N ratio of 3. Linearity has been demonstrated over 2 orders of magnitude for Leu. The ability to implement this system for post-column chemiluminescence detection of amino acids following a protein digest has been demonstrated.
Amino Acids Serine Leucine HPLC Chemiluminescence

"Selective Determination Of Gases By Two-stage Membrane-differentiated Flow Injection Analysis. Determination Of Trace Hydrogen Cyanide In The Presence Of Large Concentrations Of Hydrogen Sulfide"
Anal. Chem. 1992 Volume 64, Issue 10 Pages 1106-1112
Vlastimil Kuban and Purnendu K. Dasgupta

Abstract: Sample gases were passed through the outside of a membrane tube (10 cm x 1 mm) of porous poly(vinylidene difluoride), through the inside of which 50 mM NaOH was flowing. After absorption of acidic gases, the pH of the solution was reduced to 9.6 by addition of a carbonate buffer. The solution then flowed along the outside of a membrane tube (18 cm x 0.4 mm) of silicone rubber, with 25 mM NaOH (in static mode) on the inside. Under these conditions, HCN but not H2S diffused into the alkaline receptor. The HCN was determined spectrophotometrically with use of an isonicotinic acid - 1-phenyl-2-pyrazolin-5-one reagent and measurement at 544 nm. The calibration graph was rectilinear for 0.1 to 1.5 ppm of HCN (by volume), with a detection limit of 35 ppb. The presence of several thousand ppm of H2S did not interfere. Hydrogen cyanide at low ppb (volume) levels is determined in the presence of several thousand ppm (volume) H2S. The gases diffuse through a porous poly(vinylidene difluoride) tubular membrane into an NaOH absorber; the pH is then adjusted to 9.5-10, and the liberated HCN is selectively permeated across a tubular silicone rubber membrane into an NaOH absorber. A limit of detection (LOD) of 35 ppb (volume) HCN is attainable with a pre-concentration time of 10 min (through-put rate of 5 samples h-1) and spectrophotometric determination of cyanide by the Koenig reaction with sodium isonicotinate and 3-methyl-1-phenyl-2- pyrazolin-5-one.
Hydrogen cyanide Spectrophotometry

"Immobilized Cyanobacteria For Online Trace Metal Enrichment By Flow Injection Atomic Absorption Spectrometry"
Anal. Chem. 1994 Volume 66, Issue 21 Pages 3632-3638
Angel Maquieira, Hayat A. M. Elmahadi, and Rosa Puchades

Abstract: Cyanobacteria (Spirulina platensis) immobilized on controlled pore glass pre-concentrate Cu(II), Zn(II), Cd(II), Pb(II), and Fe(III) from aqueous solution with high efficiency as ascertained using an online flow injection atomic absorption spectrometry system. The degree of metal binding depends on the pH of the solution. Quantitative retention of copper, zinc, and cadmium occurred at a wide range of pH values, while the retention for lead and iron was pH-dependent. The latter metals were adsorbed strongly only at pH 6 and 7, respectively. The breakthrough capacity was determined from the breakthrough curve, with values of 0.0035, 0.0008, 0.0011, 0.0028, and 0.0017 ng/mL for Cu, Zn, Cd, Pb, and Fe, respectively, being obtained. The analysis of a certified reference sample, sewage sludge of domestic origin (BCR No. 144), for cadmium and copper with a high accuracy ensures the feasibility of this technique for environmental analysis. Copyright 1994, American Chemical Society.
Copper Cadmium Lead Iron Sludge BCR 144 Spectrophotometry

"Flow Injection Amperometric Detection Of Hydrazine By Electrocatalytic Oxidation At A Perfluorisulfonated Ionomer/ruthenium Oxide Pyrochlore Chemically Modified Electrode"
Anal. Chem. 1995 Volume 67, Issue 1 Pages 208-211
Jyh-Myng Zen and Jen-Sen Tang

Abstract: To prepare the electrode, Nafion was spin-coated on to a vitreous carbon electrode, and ruthenium oxide pyrochlore particles were synthesized in the Nafion matrix by treatment of the Ru3+,Pb2+-exchanged polymer in alkaline aqueous solution with purging of O2 at 53°C for at least 1 day. The electrode was equilibrated in NH3/NH4Cl buffer (pH 8) containing hydrazine before measurements. The oxidation peak of hydrazine in the buffer as electrolyte was measured at +0.6 V vs. Ag/AgCl. Flow injection amperometry with the NH3 buffer as carrier and detection at +0.7 V gave linear response for 0.6-50 µM-hydrazinium sulfate and the limit of detection was 0.15 µM in a 20 µL sample. The electrode coating prevented interference by gelatin or albumin, and hydrazine could be determined without interference from oxalic acid. The RSD at 10 µM was 5% (n = 25). A Nafion/ruthenium oxide pyrochlore (Pb2Ru2-xPbxO7-y)-modified glassy carbon electrode exhibits excellent electrocatalytic activity in the oxidation of hydrazine in neutral media. The catalyst is synthesized directly inside the Nafion thin film matrix, which is spin coated onto a glassy carbon electrode. Hydrazine is detected by flow injection analysis at the modified electrode with excellent sensitivity. Linear calibration curves are obtained over the 5 10^-5-6 10^-7 M range with pH 8.0 ammonia-ammonium chloride buffer solution as the carrier. The detection limit is 0.048 ng. The practical analytical utility is illustrated by selective flow injection measurements of hydrazine in the presence of oxalic acid and surface-active materials. Copyright 1995, American Chemical Society.
Hydrazine Electrode Electrode Electrode Amperometry

"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

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

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

"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

"Application Of An Online Preconcentration System In Simultaneous ICP-AES"
Microchim. Acta 1992 Volume 106, Issue 3-6 Pages 191-201
Peter Schramel, Li -Qiang Xu, G&uuml;nter Knapp and Markus Michaelis

Abstract: A PC-controlled online pre-concentration system (TRACECON) was connected to a JY-70 Plus simultaneous inductively coupled plasma (ICP) spectrometer to pre-concentrate online seven trace elements (Cu, Fe, Zn, Cr, Ni, Mn, V) in biological and environmental samples. EDTrA-cellulose was used as column material. The elemental concentrations were determined by simultaneous ICP-AES. The effect of pH of the sample solution on the enrichment was studied. It was found that the recoveries of chromium and iron depend strongly on the pH of the sample solution. All the elements mentioned were recovered quantitatively at pH 4.0. The flow rates of sample solution and element solution were optimized. The enrichment factors for seven elements at 5 mL loading volume range from 3.9 for Cu to 7.9 for Zn. The detection limits of all seven elements were improved. The accuracy of the method was tested by the analysis of a number of CRMs of NIST, BCR and NIES. Most results are in good agreement with the certified values.
Copper Iron Zinc Chromium Nickel Manganese Vanadium Biological Environmental Spectrophotometry

"Acridinium Ester Chemiluminescence: PH-dependent Hydrolysis Of Reagents And Flow Injection Analysis Of Hydrogen Peroxide And Glutamate"
Microchim. Acta 1992 Volume 108, Issue 3-6 Pages 205-219
Maureen Stuever Kaltenbach, and Mark A. Arnold

Abstract: A flow injection system is described for the determination of H2O2 based on the chemiluminescent reaction with 10-methyl-9-phenoxycarbonylacridinium (I). The carrier stream is pumped at 4 mL min-1 and consists of a standard H2O2 solution in boric acid buffer solution of pH 9; the concentration. of the standard solution cover the range 0.1 µM to 1 mM H2O2. I reagent (20 µL) is injected into the carrier stream and the solution are mixed by passage through a coiled incubation tube. The chemiluminescence reaction is initiated by adding a base just before the sample passes in front of a photomultiplier tube. The detection limit is 0.25 µM. By coupling this system to an enzyme column it is possible to determine glutamate, the H2O2 formed as glutamate passes through a reaction column of L-glutamate oxidase being determined by the above procedure. The detection limit is 0.5 µM with a throughput of 300 samples h-1. An automated anal. system is described for the measurement of hydrogen peroxide based on a chemiluminescence reaction with Ph 10-methylacridinium-9-carboxylate (PMAC). A reversed FIA experimental arrangement is used to establish the operating conditions for the measurement of submicromolar levels of hydrogen peroxide. The carrier stream consists of hydrogen peroxide standards prepared in a pH 9.0, boric acid buffer and the flow rate for this carrier/sample stream is 4 mL/min. Twenty microliters of a 10 mM PMAC solution, prepared in a pH 3 phosphate buffer, are injected into the carrier/sample stream. Hydrogen peroxide mixes with the PMAC reagent in an incubation coil that is constructed by wrapping 107 cm of polyethylene tubing around a 1 cm o.d. plastic rod. The chemiluminescence reaction is then initiated by adding a base just before the sample passes in the front of a photomultiplier tube detector. The calculated limit of detection (S/N = 3) for hydrogen peroxide is 0.25 µM. In addition, the pH dependent hydrolysis of the PMAC reagent is characterized by an HPLC method which has been specifically developed for the separation and detection of the hydrolysis products of PMAC. Results indicate that a pH of 3.0 is required for long term stability of the PMAC reagent. Finally, this system has been successfully extended to the measurement of glutamate by coupling a bioreactor column of glutamate oxidase with the hydrogen peroxide detection scheme. A detection limit (S/N = 3) of 0.5 µM has been established for glutamate with a throughput of 200 samples per h.
Hydrogen peroxide Glutamate Chemiluminescence

"2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol As A New Analytical Reagent For Flow Injection Spectrophotometric Determination Of Trace Vanadium(V)"
Microchim. Acta 1998 Volume 130, Issue 1-2 Pages 111-115
Takeshi Yamane and Yuzuru Yamaguchi

Abstract: A flow injection method using 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (Nitro-PAPS) as a new chromogenic reagent is presented for sensitive and rapid determination of V. Nitro-PAPS reacts with V(V) in weakly acidic medium to form a water soluble complex of molar absorptivity of 8.0 x 10^4 L mol-1 cm-1 at 592 nm (max. absorption wavelength), which permits the straightforward application of a flow injection system to the sensitive determination of vanadium. Under the optimum conditions established, a linear calibration graph was obtained in the range 1-120 ng mL-1. The RSD for 60 ng mL-1 V was 2.2% (n = 5) and the limit of detection was 1 ng mL-1. The sample throughput is ≈40 h-1. Most inorganic and organic anions examined did not interfere even at concentrations of 3000-6000 times of vanadium. Interference from Co(II), Cu(II), and Ni(II) at 200 ng mL-1 levels can be overcome by the addition of N-(dithiocarboxy)sarcosine. The recoveries for each 20 and 10 ng mL-1 V added to the river water were 98 and 97%, respectively.
Vanadium(V) River Spectrophotometry

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

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

"Determination Of Promethazine Hydrochloride With Bromophenol Blue By A Turbidimetric Method And Flow Injection Analysis"
Microchem. J. 1992 Volume 45, Issue 2 Pages 129-136
J. Martinez Calatayud*, a,*, S. Navasquillo Sarriona, A. Sanchez Sampedrob and C. Gomez Benitob

Abstract: The drug was extracted from the tablets with water and a portion (91.8 µL) was injected into the carrier reagent stream (0.97 mL min-1) which consisted of a mixture of 1.16 mM bromophenol blue and 86 mM KCl which was adjusted to pH 1.20 with HCl. The reaction coils were Teflon tubes (0.5 mm i.d.) and the turbidity was measured in an 18 µL flow cell at 650 nm. The calibration graph (peak height) was rectilinear from 25 to 197 ppm of promethazine with a coefficient of variation (n = 30) of 1.3%; the sample injection rate was 32 h-1. The tolerance of this method to some foreign compounds is also reported. A flow injection analysis procedure for the turbidimetric determination of promethazine is proposed. The sample solution is injected directly into the carrier reagent stream, which is composed of 1.16 x 10^-3 M bromophenol blue at pH 1.20. The calibration graph is linear over the range 25-197 ppm of promethazine. The influence of some foreign substance was also investigated. The method was applied to promethazine determination in a pharmaceutical formulation.
Promethazine hydrochloride Pharmaceutical Turbidimetry

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

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

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

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

"Fluorometric Determination Of Urinary Kynurenic Acid By Flow Injection Analysis Equipped With A"
Anal. Biochem. 1990 Volume 190, Issue 1 Pages 88-91
Ken-ichi Mawatari, Fumio Iinuma and Mitsuo Watanabe

Abstract: A flow injection analysis involving a photochemical reaction and fluorometric detection has been developed for the determination of urinary kynurenic acid. Kynurenic acid was found to fluoresce on irradiation with ultraviolet light at pH 7.2 in the presence of hydrogen peroxide. This method was applied to flow injection analysis using a new procedure involving a 'bypass line' for the simultaneous determination of urinary kynurenic acid and background fluorescence. The calibration graph showed linearity over the range of 0.20 to 120 pmol. For pretreatment of urinary kynurenic acid, a PRE-SEP C18 cartridge was used. The mean recovery of kynurenic acid from urine was 94.5%. The content of urinary kynurenic acid was 13.0±2.68 µmol/day. There was good correlation (r = 0.9729) between values determined by flow injection analysis and high performance liquid chromatography. Urine, diluted 25-fold with 0.2 M Na2HPO4 - 0.1 M citric acid buffer (pH 3.2), was applied to a PRE-SEP C18 cartridge and kynurenic acid (I) was eluted with phosphate buffer solution (pH 7.2) containing 20% methanol. The eluate was subjected to flow injection analysis with 0.07 M phosphate buffer (pH 7.2) containing 25 mM H2O2 - methanol (8:2) as carrier solution (1.2 mL min-1). After injection into the carrier solution the stream was split; one part was passed through a photochemical reaction coil and the second part, for background correction, bypassed the reaction coil. Fluorescence detection was at 465 nm (excitation at 370 nm). The calibration graph was rectilinear for 0.20 to 120 pmol of I. Recovery was 94.5% and results correlated well (r = 0.973) with those by HPLC.
Kynurenic acid Urine HPLC Fluorescence

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

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

"Studies On The Rate And Control Of Antibody Oxidation By Periodate"
Anal. Biochem. 1995 Volume 231, Issue 1 Pages 123-130
Wolfe C. A. C. and Hage D. S.

Abstract: The oxidation of antibody carbohydrate residues by periodate is a common approach for the site-specific immobilization or modification of antibodies for use in various bioanalytical methods. This study examined the time dependence of this oxidation process under a variety of pH, temperature, and concentration conditions. Polyclonal rabbit immunoglobulin G (IgG)was used as the model system for these studies. Flow injection analysis and a hydrazide label (Lucifer yellow CH) were used to monitor the progress of the oxidation reaction. It was found that the number of oxidized sites that were available for labeling could be varied between one and eight groups per antibody by adjusting the time, pH, periodate concentration, or reaction temperature. In each case, most of these groups were produced during the first 30-60 min of the reaction. A comparison was made between these results and those of previous studies that have examined the effects of periodate treatment on amino acid residues and antibody activity. From this work, general guidelines were developed for the control and optimization of antibody oxidation for use with assays that require either high or low levels of antibody modification.
Immunoglobulin G Spectrophotometry

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

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

"Indirect-spectrophotometric Determination Of Vanadium(IV) By Flow Injection Analysis Based On The Redox Reaction With Copper(II) In The Presence Of Neocuproine"
Anal. Lett. 1991 Volume 24, Issue 7 Pages 1219-1230
Itabashi, H.;Umetsu, K.;Satoh, K.;Kawashima, T.

Abstract: Sample solution was injected into a carrier stream of water and mixed with 0.1 mM Cu (II) and 0.5 mM neocuproine at pH 5.6. The absorbance of the solution was measured at 454 nm. The calibration graph was rectilinear for 2 to 80 µM-V(IV) and the detection limit was 0.2 µM. The coefficient of variation was 0.2 to 8.9%. Fractional determination of Fe(II) and V(IV) was achieved with use of pyrophosphate.
Vanadium(IV) Spectrophotometry

"Separation Of Titanium And Iron In Brines By Solid Supported Liquid Membrane Using Tributyl Phosphate As Carrier"
Anal. Lett. 1991 Volume 24, Issue 10 Pages 1923-1934
Munoz, M.;Valiente, M.

Abstract: Use of a supported liquid membrane to separate mixtures of Ti(V) and Fe(III) in highly concentrated aqueous chloride is described. TBP was used as the extracting agent with solution containing Mg(NO3)2 and HCl as the stripping phase. The supporting liquid membrane was prepared by impregnating the microporous laminar support with the organic solution containing the extractant. The transport of Ti and Fe through the liquid membrane was monitored by online colorimetry using flow injection analysis. The effects of hydrodynamic conditions, membrane area, metal concentration, extractant concentration, pH and chloride concentration in the feed solution was investigated. A model was presented to describe the liquid membrane system.
Iron Titanium Environmental Sample preparation

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

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

"Potentiometric Biosensing Of Penicillins Using A Flow-through Reactor With Penicillinase Or Penicillin Amidase Immobilized By γ-irradiation"
Anal. Lett. 1995 Volume 28, Issue 10 Pages 1735-1749
Macca, C.;Solda, L.;Palma, G.

Abstract: A mixture of 2-hydroxyethyl methacrylate, NN'-methylene-bis-acrylamide and penicillinase or penicillin amidase in phosphate buffer was added dropwise to n-hexane cooled to -78°C. The suspension of frozen droplets was irradiated at 0.4 Gy/s for 5 h with 60Co γ-rays. The resulting polymer spheres (~0.5 mm diameter) were packed into a column (50 or 100 mm x 4.6 mm i.d.) to form a reactor for FIA of penicillins. Samples (20 µL) were injected into a phosphate buffer carrier stream, and after passing through the reactor they were carried to a wall-jet flow cell (Ramos et al., Anal. Chem., 1994, 66, 1931) with a pH sensor (Galiatsatos et al., Biosens. Bioelectron., 1990, 5, 47). Linear or logarithmic responses to penicillins were obtained for both enzymes depending on the carrier buffer capacity and flow rate (details given). The optimal pH range was 5.8-6.8. Sensitivity increased as buffer concentration decreased but the dynamic range was narrower.
Penicillins Electrode Potentiometry

"Chemiluminescence Flow Injection System For Rapid Detection Of Red Tide Phytoplankton, Chattonella Antiqua"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2279-2288
Ryoichi Asai; Ritsuko Matsukawa; Kazunori Ikebukuro; Isao Karube

Abstract: A chemiluminescent flow injection analysis (FIA) system to detect the red tide phytoplankton, Chattonella antiqua, was developed based on a Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-α]-pyrazin-3-one (MCLA), which strongly emits light at 465 nm in the presence of superoxide. The system consists of a 2-reagent feeding stream, a sample injector, a joint for mixing MCLA and sample, a chemiluminescence (CL) reaction cell, a CL detector, and a recorder unit. Response time is ~1 min/measurement cycle. The FIA system has an optimum pH of 10.7. Calibration curves for C. antiqua displayed linearity from 2 x 103 to 2 x 104 cells/mL. When used to measure C. antiqua, sensitivity of the FIA system was ~10 times higher than that of the cytochrome c method. The FIA system is a rapid, practical method to detect C. antiqua.
Phytoplankton, chattonella antiqua, red tide Sea Chemiluminescence

"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

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

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

"Electrocatalysis And Flow Detection At A Glassy-carbon Electrode Modified With A Thin Film Of Oxymanganese Species"
Electroanalysis 1991 Volume 3, Issue 3 Pages 215-219
Ziad Taha, Joseph Wang

Abstract: A vitreous-carbon electrode was modified by cycling the potential between -0.5 and +0.4 V vs. Ag - AgCl in 27 mM MnCl2 - 1.4 M NaOH medium. The electrode was shown to reduce greatly the overvoltage for the oxidation of hydrazine, methylhydrazine or H2O2, thereby facilitating amperometric detection of these compounds in flowing streams. Effects of pH, flow rate, operating potential, film thickness, concentration. and other variables on the catalytic response of the electrode were studied; the response was very stable. Detection limits at the fmol and pmol levels and coefficient of variation of 1.3% in flow injection analysis are reported.
Amperometry Electrode Electrode Electrode

"Determination Of Sulfur Dioxide In White Wines By Flow Injection With Electrochemical Detection"
Electroanalysis 1991 Volume 3, Issue 8 Pages 859-863
Terence J. Cardwell, Robert W. Cattrall, Chen Guo Nan, Peter J. Iles, Ian C. Hamilton, Geoffrey R. Scollary

Abstract: Wine samples were injected directly without pre-treatment into a carrier stream of 0.01 M H2SO4 (2.0 mL min-1). Sample solution were cleaned up by pre-electrolysis in a stainless-steel tube packed with graphite felt before amperometric detection of SO2 at +1 V vs. Ag - AgCl. Ascorbic and gallic acids were completely oxidized at +0.8 V thus eliminating interference. The concentration. of free SO2 was derived from a calibration plot. Total SO2 was measured by adjusting the pH of the sample to 12 with 0.5 M NaOH followed by dilution. The calibration graph was rectilinear up to 60 mg L-1 of SO2. Results agreed with those by the standard aspiration - oxidation method.
Sulfur dioxide Wine White Amperometry Electrochemical analysis

"Flow Injection Determination Of Methionine With Amperometric Detection At A Stable Modified Electrode"
Electroanalysis 1991 Volume 3, Issue 3 Pages 239-242
James A. Cox, Ewa Dabek-Zlotorzynska

Abstract: A vitreous-carbon electrode was polished with alumina, rinsed in an ultrasonic bath and modified by cycling in 2 mM RuCl3 - 2 mM K4Ru(CN)6 - 0.5 M KCl medium (adjusted to pH 2 with HCl) between 500 and 1100 mV vs. Ag - AgCl at 50 mV s-1 for 40 cycles. The cell was filled with carrier solution and stored on open circuit when not in use. The electrode catalyzed the oxidation of methionine at 0.92 V vs. Ag - AgCl. A rectilinear calibration graph was obtained for flow injection amperometry over the range 0.6 to 180 µM with 0.2 M K2SO4 as carrier at pH 2, a 7.5 µL sample volume, and a flow rate of 1 mL min-1. The sensitivity was 0.05 µM nA-1 at a 0.07-cm2 electrode. After a single surface preparation, the sensitivity remained constant over >3 weeks with daily use.
Methionine Amperometry Electrode

"Electrocatalytic Reduction Of Haemoglobin At A Chemically Modified Electrode Containing Riboflavin"
Electroanalysis 1997 Volume 9, Issue 2 Pages 115-119
Wenliang Sun, Jilie Kong, And Jiaqi Deng

Abstract: The electrode was constructed from the end face of a 5 mm diameter graphite rod enclosed in a Plexiglass tube. The exposed rod face was polished with emery paper, rinsed with water, sonicated successively in 1:1 HNO3, acetone and water and immersed for 6 h in 0.1 mM riboflavin (I) in buffer of pH 6.1. Cyclic voltammograms of the electrode in KH2PO4/Na2HPO4 buffer of pH 6.8 showed two symmetrical I reduction and oxidation peaks with E1/2 -0.37 V vs. a saturated Ag/AgCl reference electrode. A Pt-wire auxiliary electrode was used and solutions were deaerated with N2 for 15 min before voltammetry. After 30 min continuous use at pH 6.8 the electrode activity was 60% of the original value. In the presence of haemoglobin (II) the I reduction and oxidation peak heights were increased and decreased, respectively, because of electron transfer between I and II. Calibration graphs obtained at scan rate of 50 mV/s were linear for 30-480 µM-II. The effect of pH on electrode catalytic activity was studied. The electrodes may be useful for FIA and analyzing other proteins.
Hemoglobin Voltammetry Electrode Electrode

"Solid-state Ion-selective Electrode Arrays"
Electroanalysis 1998 Volume 10, Issue 16 Pages 1096-1100
Aoga'n Lynch, Dermot Diamond *, Patrick Lemoine, Jim McLaughlin, Matt Leader

Abstract: Variable pressure scanning electron microscopy is demonstrated to be a powerful method for directly studying swelling processes occurring during conditioning of PVC-membrane ion-selective electrodes containing a salt-doped hydrogel layer between the PVC and the internal Ag/AgCl reference electrode. Using an in-house developed virtual instrument interface and a portable PC fitted with a PCMCIA data acquisition card, it is relatively easy to adapt arrays manufactured for blood-gas analysis for other applications which involve the determination of mixtures of inorganic ions. The simultaneous analysis of sodium and chloride over concentration ranges associated with the diagnosis of cystic fibrosis (CF) in sweat is demonstrated as an example.
Sodium Chloride Electrode Electrode Electrode

"Electrocatalysis With A Dirhodium-substituted Polyoxometalate Anchored In A Xerogel-based Composite. Application To The Oxidation Of Methionine And Cystine At Physiological PH"
Electroanalysis 1998 Volume 10, Issue 18 Pages 1237-1240
Mark E. Tess, James A. Cox

Abstract: Replacing a tungsten oxide group of phosphotungstic acid with a Rh(II) acetate dimer yielded a species, Rh2POM, that catalyzed the electrochemical oxidation of L-methionine (L-Met), L-cystine, and As(III). The electrocatalytic activity of Rh2POM was greater than that of the simple Rh(II) acetate dimer in homogeneous solution A conducting carbon-composite electrode (CCE) comprising Rh2POM and carbon powder in a SiO2 matrix prepared by sol-gel chemical was catalytically active over the pH range 2-10. The CCEs produced voltammetric responses toward L-Met and L-cystine that were pH independent over the above range and were stable for at least 4 mo under dry storage. If passivated, the catalytic activity was generated by polishing. For example, a RSD of 2.9% (5 points) was obtained when the surface was polished between cyclic voltammetric experiments on 5.0 mM L-Met at pH 7.4. A least squares fit of flow injection amperometric data obtained over the range 5-156 µM L-Met (7 points) yielded the following: slope 0.85 µA mM 1; intercept 0.05 µA; and r = 0.995. The detection limit was 2.3 µM.
l-Methionine Amperometry Electrode Sensor

"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

"Simultaneous Determination Of Biogenic Amines By Reversed-phase High Performance Liquid Chromatography"
J. Chromatogr. A 1990 Volume 508, Issue 1 Pages 225-228
Satoru Suzuki, Kentaro Kobayashi, Junko Noda, Tetsuya Suzuki and Kozo Takama

Abstract: The method of Gamoh and Fujita (Shimadzu Rev., 1987, 44, 237) was modified for the determination of histamine and five other biogenic amines in herring muscle. Dried herring (5 g) was homogenised with 10% trichloroacetate acid (2 x 20 ml), centrifuged at 550 g for 20 min, and the combined extracts were diluted to 50 mL. A portion (5 µL) of the solution was analyzed by HPLC on a column (15 cm x 6 mm) of Shim-Pak CLC-ODS operated at 50°C with gradient elution (1.1 mL min-1) with (i) 0.01 M Na hexanesulfonate in 0.1 M NaClO4 (pH 4.0) and (ii) a mixture of (i) - methanol (1:3) adjusted to pH 3.0 (details given). After post-column o-phthalaldehyde derivatization fluorimetric detection was at 455 nm (excitation at 345 nm). The method can also be applied in clinical analyzes.
Amines, biogenic Histamine Muscle Clinical analysis HPLC Fluorescence Sample preparation

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

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

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

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

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

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

"Determination Of Dissolved Hexavalent Chromium In Industrial Waste Water Effluents By Ion Chromatography And Post-column Derivatization With Diphenylcarbazide"
J. Chromatogr. A 1991 Volume 546, Issue 1 Pages 335-340
Elizabeth J. Arar and John D. Pfaff

Abstract: A previously described method ('Dionex Technical Note', No 26, Dionex Corp., Sunnyvale, CA, 1990) for the ion-chromatographic determination of Cr(VI) as its complex with diphenylcarbazide was applied to industrial effluents. All samples were stored on ice and analyzed within 4 h of collection and again the next day. Aqueous samples were filtered and adjusted to pH 9 to 9.5 (optimum) before analysis. The method was not applicable to solid wastes. For waste water, recoveries were quantitative and no oxidation of Cr(III) and Cr(VI) occurred.
Chromium(VI) Industrial Waste HPIC

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

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

"Reversed-phase Separation Of Transition Metals, Lanthanoids And Actinoids By Elution With Mandelic Acid"
J. Chromatogr. A 1991 Volume 558, Issue 1 Pages 197-207
Steve Elchuk, Kerry I. Burns, Richard M. Cassidy and Charles A. Lucy

Abstract: A gradient concentration of 0.14 M to 0.50 M mandelic acid during 15 min was used in a mobile phase (1.0 mL min-1) of 0.01 M Na octanesulfonate at pH 4.0 for separation of lanthanoids in a column (10 cm x 4 mm) of Spherisorb C18 (3 µm), with post-column derivatization with arsenazo III for detection at 685 nm. The same column was used for separation of six actinoids in a mobile phase of 0.5 M mandelic acid in aqueous 5% acetonitrile (pH 3.2; no octanesulfonate) with similar derivatization and detection. Suitable operating concentration. were 1 mg L-1 for lanthanoids or 0.3 (Am) or 3.0 mg L-1 (others) for actinoids. Specimen chromatograms are presented and results are discussed.
Metals, actinides Metals, lanthanides Metals, transition HPLC Spectrophotometry

"Displacement Post-column Detection Reagents Based On The Fluorescent Magnesium 8-hydroxyquinoline-5-sulfonic Acid Complex"
J. Chromatogr. A 1994 Volume 671, Issue 1-2 Pages 121-129
Charles A. Lucy* and Liwen Ye

Abstract: A non-specific reagent for the post-column detection of metal ions was obtained by displacement of Mg2+ from Mg(CDTA)2- and reaction of the liberated Mg2+ with 8-hydroxyquinoline-5-sulfonic acid (I) to form a fluorescent complex. The kinetics and equilibria of the reaction and the effects of sequential and simultaneous addition of Mg-CDTA and I are discussed. Most experiments were conducted using an HPLC system in the FIA mode, with detection at excitation and emission wavelengths of 360 and 500 nm, respectively. The optimum sensitivity was obtained at pH 8. For simultaneous addition of the reagents, alkaline earth metals gave a positive response, but there was no response for transition metals. Addition of Mg(CDTA)2- followed by I2- gave a positive response for Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Cu2+, Ni2+ and Co2+. The response for Mn2+ was linear for 25-2500 pmol.
Magnesium(II) Calcium(2+) Strontium(II) Barium(2+) Manganese(II) Copper(II) Nickel(II) Cobalt(II) HPLC Fluorescence

"Reversed-phase High Performance Liquid Chromatographic Method For The Measurement Of Polyamine Oxidase Activity"
J. Chromatogr. B 1990 Volume 533, Issue 1 Pages 187-194
Allan G. Halline and Thomas A. Brasitus

Abstract: Cytosolic fractions of small intestinal or colonic mucosa was incubated at 37°C for up to 60 min with glycine, dithiothreitol, N'-acetylspermidine, aminoguanidine and pargyline. The reaction was stopped by addition of trichloroacetic acid and the mixture was filtered and subjected to HPLC on an Ultrasphere ion-pair column (25 cm x 4.6 mm) with a Guard-Pak pre-column module and a Waters C18 cartridge. Gradient elution (1 mL min-1) was from 65 to 100% of 0.2 M Na acetate of pH 4.5 (I) - acetonitrile (10:3) containing 10 mM octanesulfonic acid (II) in 0.1 M I containing 10 mM II. Post-column derivatization was with o-phthalaldehyde and fluorescence detection at 455 nm (excitation at 340 nm). Rapid and efficient separation of N'-acetylspermidine and putrescine (reaction product).
Enzyme, polyamine oxidase HPLC

"Determination Of 2-mercaptopropionylglycine And Its Metabolite, 2-mercaptopropionic Acid, In Plasma By Ion-pair Reversed-phase High Performance Liquid Chromatography With Post-column Derivatization"
J. Chromatogr. B 1991 Volume 564, Issue 1 Pages 258-265
Pierre Leroy, Alain Nicolas*, Catherine Gavriloff and Muriel Matt, Patrick Netter and Bernard Bannwarth, Bernard Hercelin and Michel Mazza

Abstract: Plasma (1 ml) was heated at 50°C for 30 min with 0.2 M phosphate buffer of pH 8 (0.2 ml) and 10% tributylphosphine in CHCl3 (0.2 ml), and proteins were precipitated by addition of ethanol to the mixture and cooling in an ice-bath. The filtrate was centrifuged, and a 50 µL portion of the supernatant was analyzed on a column (12.5 cm x 4 mm) of LiChrospher RP-18e (5 µm), fitted with a guard column (4 mm x 4 mm) of the same material, with acetonitrile - 0.01 M phosphate buffer of pH 7.0 (1:3) containing 5 mM cetrimonium bromide. After derivatization with pyrene maleimide, the fluorescence of the derivatives was measured at 370 nm (excitation at 260 nm). The calibration graphs were rectilinear from 0.2 to 10 and from 0.2 to 5 µg mL-1 of 2-mercaptopropionylglycine (tiopronin; I) and 2-mercaptopropionic acid (II), with coefficient of variation (n = 5) of 6.2 and 9.9% for 0.2 µg mL-1 of I and II, respectively. Recoveries were 95% and the limit of detection were 0.05 µg mL-1 of analyte. Sampling rate was 5 to 6 h-1.
2-Mercaptopropionylglycine 2-Mercaptopropionic acid Blood Plasma HPLC Fluorescence

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

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

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

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

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

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

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

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

"FIA - Fluorimetric Determination Of Thiamine"
J. Pharm. Biomed. Anal. 1990 Volume 8, Issue 8-12 Pages 667-670
J. Martinez Calatayuda,*, C. Gomez Benitob and D. Gaspar Gimeneza

Abstract: Sample solution (137.3 µL) was injected into a carrier stream (0.74 mL min-1) of Na2CO3 - boric acid (pH 10) into a coil column (225 cm length) containing immobilized hexacyanoferrate on an ion-exchange resin (cf., Calatayud and Sagrado Vives, Ibid., 1989, 7, 1165) and the fluoresence of the eluate was measured at 440 nm (excitation at 368 nm). Calibration graphs were rectilinear from 0.1 to 4.0 ppm of thiamine. Coefficient of variation was 1.8%. Sample throughput was 28 h-1. Other vitamins, e.g. riboflavin, nicotinamide, pyridoxin, and certain other substances, e.g. caffeine, gave errors of up to 4.3%. A flow injection fluorimetric determination of thiamine is reported. The procedure is based on the oxidation of the analyte with potassium hexacyanoferrate(III) immobilized on an anionic exchange resin; the fluorescence is monitored in aqueous basic solution. Concentrations of the vitamin of 0.1-4 ppm have been determined; the relative standard deviation was 1.8%. The injection rate was 28 samples/h. The influence of other substances and the determination of the drug in a pharmaceutical formulation are also reported.
Thiamine Pharmaceutical Fluorescence Ion exchange

"Indirect Continuous Automatic Determination Of Pharmaceuticals By Atomic Absorption Spectroscopy"
J. Pharm. Biomed. Anal. 1990 Volume 8, Issue 8-12 Pages 655-661
M. Valc&aacute;rcel*, M. Gallego and R. Montero

Abstract: The implementation of continuous separation techniques such as precipitation, liquid-liquid and solid-liquid extraction in FIA manifolds coupled online with an atomic absorption spectrometer for the determination of active components (sulfonamides, local anaesthetics, amphetamines, benzodiazepines, chloramphenicol and methadone) in pharmaceuticals and biological fluids is systematically described. The basic features of the analytical methodologies described (sensitivity, selectivity, precision and rapidity) are also discussed and critically compared. The use is described of continuous separation techniques such as, precipitation, liquid - liquid and solid - liquid extraction in flow injection analysis manifolds coupled online to an AA spectrometer for the determination of active components in pharmaceuticals and biological fluids. Sulfonamides were pptd. with Cu standard solution (more selective) or Ag ions at pH 6 to 7, filtered and the filtrate was measured by AAS. Anaesthetics were pptd. with Co ions. Recoveries were quantitative. The continuous liquid-liquid extraction technique was based on the method described by Nord and Karlberg (Anal. Chim. Acta, 1981, 125, 199) and was applied in the determination of amphetamines and bromazepam. Solid-phase redox columns were used for those compounds with potentially reducible groups, e.g. sulfone, N-oxide groups. The basic features (sensitivity, selectivity, precision and rapidity) of the analytical methods described are discussed.
Bromazepam Amphetamines Anaesthetics Pharmaceutical Biological fluid Spectrophotometry Sample preparation

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

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

"An Online Immunoassay Method For Theophylline Using A Protein A Immunoreactor"
J. Pharm. Biomed. Anal. 1991 Volume 9, Issue 10-12 Pages 1121-1123
Pilar Fernandez-Hernando and James N. Miller

Abstract: A heterogeneous fluorescence immunoassay for theophylline has been automated using a flow injection analysis system containing a protein A solid phase reactor to separate antibody-bound and unbound fluorescein-theophylline. For each sample the antibody-protein A reaction takes place at near neutral pH, and the complexes are eluted at acid pH. The antibody-binding capacity of the reaction greatly exceeds the antibody level in each sample incubation mixture, and a single reactor can be repeatedly cycled between neutral and acid pHs. Experimental variations such as reactor size, flow rate, pH values, and reactant concentrations have been studied. Theophylline could readily be determined at the µg mL-1 level with online incubation with antibodies. Sheep anti-theophylline antiserum, serum sample and fluorescein isothiocyanate-theophylline were injected into a carrier stream of 50 mM Tris - HCl buffer of pH 8.8 containing 0.1 M NaCl. The mixture passed through a column (5 cm x 3 mm) of protein A immobilized on controlled pore glass particles; elution was effected by the injection of 0.5 M citrate buffer of pH 3.5 containing 0.1 M NaCl. The eluate was detected fluorimetrically at 525 nm (excitation at 495 nm). The flow rate was 0.2 mL min-1 throughout. Recoveries of theophylline were 80.5 to 94.8% and the within- and between-day coefficient of variation (n = 10) were both 7.9%.
Theophylline Fluorescence Immunoassay

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

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

"Determination Of Some Rare Earth Elements In Seawater By Inductively Coupled Plasma Mass Spectrometry Using Flow Injection Preconcentration"
Spectrochim. Acta B 1998 Volume 53, Issue 9 Pages 1281-1287
O. Vicente, a, A. Padr&oacute;a, L. Martineza,*, R. Olsinab and E. Marchevskyb

Abstract: An online Eu, Tb, Ho, Tm and Lu pre-concentration and determination system implemented with inductively coupled plasma mass spectrometry associated to a flow injection method was studied. Quinolin-8-ol and Amberlite XAD-7 were used for the retention of Eu, Tb, Ho, Tm and Lu, at pH 10.0. The rare earth elements were re-extd. from the microcolumn with nitric acid. The detection limits for the pre-concentration of 100 mL of aqueous solution of Eu, Tb, Ho, Tm and Lu were 0.016, 0.0023, 0.0017, 0.0035 and 0.0015 pg/mL, respectively, with a relative standard deviation of ~2.0%. The calibration graphs obtained using the pre-concentration system for Eu, Tb, Ho, Tm and Lu were linear at levels near the detection limits up to at least 1 ng/mL. The method was applied to the determination of Eu, Tb, Ho, Tm and Lu in seawater samples.
Metals, rare earth Europium Terbium Holmium Lutetium Sea Mass spectrometry

"Flow Injection Determination Of Selenium By Successive Retention Of Se(IV) And Tetrahydroborate(III) On An Anion-exchange Resin And Hydride Generation Electrothermal Atomization Atomic Absorption Spectrometry With In-atomizer Trapping. 1. Method Development And Investigation Of Interferences"
Spectrochim. Acta B 1998 Volume 53, Issue 14 Pages 1931-1943
Pablo E. Carrero and Julian F. Tyson*

Abstract: A sample solution was passed at 20 mL min-1 through a column (150 x 4 mm2) of Amberlite IRA-410 Strong anion-exchange resin for 60 s. After washing, a solution of 0.1% sodium borohydride was passed through the column for 60 s at 5.1 mL min-1. Following a 2nd wash, a solution of 8 mol/L hydrochloric acid was passed at 5.1 mL min-1 for 45 s. The hydrogen selenide was stripped from the eluent solution by the addition of an argon flow at 150 mL min-1 and the bulk phases were separated by a glass gas-liq. separator containing glass beads. The gas stream was dried by passing through a Nafion.RTM. dryer and fed, via a quartz capillary tube, into the dosing hole of a transversely heated graphite cuvette containing an integrated L'vov platform which had been pretreated with 120 µg of iridium as trapping agent. The furnace was held at a temperature of 250°C during this trapping stage and then stepped to 2000°C for atomization. The calibration was performed with aqueous standards solution of selenium (selenite, SeO2-3) with quantification by peak area. A number of experimental parameters, including reagent flow rates and composition, nature of the gas-liq. separator, nature of the anion-exchange resin, column dimensions, argon flow rate and sample pH, were optimized. The effects of a number of possible interferents, both anionic and cationic were studies for a solution of 500 ng/L of selenium. The most severe depressions were caused by iron (III) and mercury (II) for which concentrations. of 20 and 10 mg/L caused a 5% depression on the selenium signal. For the other cations (cadmium, cobalt, copper, lead, magnesium, and nickel) concentrations. of 50-70 mg/L could be tolerated. Arsenate interfered at a concentration. of 3 mg-1, whereas concentrations. of chloride, bromide, iodide, perchlorate, and sulfate of 500-900 mg/L could be tolerated. A linear response was obtained between the detection limit of 4 ng/L, with a characteristic mass of 130 pg. The RSDs for solutions containing 100 and 200 ng/L selenium were 2.3% and 1.5%, respectively.
Selenite Ion exchange Spectrophotometry

"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

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

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

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

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

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

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

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

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

"Preconcentration, Separation And Multi-elements Determination In Seawater Using A Cellulose-zinc Hydroxide System With Inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Sci. 1992 Volume 8, Issue 1 Pages 45-50
I. M. M. KENAWY

Abstract: The use of a cellulose-Zn(OH)2 mixture for the determination of traces of Cd(II), Cr(III), Cu(II), Fe(III), Hg(II), La(III), Ni(II), Pd(II), Sn(IV), and vanadate ion in seawater at different pH's was carried out employing the ICP technique. The effects of the concentration. of Zn(II), mass of the cellulose, shaking time, and pH on the pre-concentration were studied. The method is simple and applicable to the trace determination of 10 heavy metals at the ppb level. The effect of alkali and alkaline earth cations on the pre-concentration of the tested metal ions was examined The distribution coefficient Kd is in the range 102.86-106.31 mL/g.
Cadmium(2+) Chromium(III) Copper(3+) Iron(III) Mercury(II) Lanthanum(3+) Nickel(II) Palladium(II) Tin(IV) Sea Spectrophotometry

"Recent Development In Flow Injection Analysis. Determination Of Bismuth, Thorium And Copper With Pyrocatechol Violet By Exploitation Of PH"
Anal. Proc. 1980 Volume 17, Issue 12 Pages 535-537
S. Baban

Abstract: Bi, Th, and Cu were spectrophotometrically determined by using flow injection analysis after complexation with pyrocatechol violet at pH 3-4. The sensitivity of the method was 3 105-10-4 M for each metal.
Bismuth Copper Thorium-232 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

"Novel Preconcentration Technique For The Determination Of Trace Elements In Fine Chemicals"
Anal. Proc. 1989 Volume 26, Issue 11 Pages 377-379
Andrea J. Ambrose, Les Ebdon, Philip Jones

Abstract: The trace elements are pre-concentrated as chelates with Chrome Azurol S (I) on to activated carbon. Thus, to a solution of Cu, Fe and Mg in water or aqueous KNO3 (20%), glucose (30%) or sucrose (20%) is added 10 mg of I and the pH is adjusted to 3. Activated carbon (0.5 g; 8 µm) was added, and the pH was increased gradually to 10 by adding dilute aqueous NH3. After agitating the mixture for ~20 min, the sorbent was separated by vacuum filtration, oven dried, scraped off the filter and mixed to a slurry with aqueous 1% Triton- x 100. The elements were then determined by flow injection slurry atomization - ICP-AES. Recoveries were complete for each analyte, but blank values were high.
Metals Copper Iron Magnesium Spectrophotometry

"Field Sampling Technique For Mercury Speciation"
Anal. Proc. 1991 Volume 28, Issue 9 Pages 293-294
Wei Jian, C. W. McLeod

Abstract: Water (2 to 10 ml) was adjusted to pH 3 to 4 with concentrated HCl and passed through a micro-column (5 cm x 1.5 mm) of sulfydryl cotton. The column was inserted into a flow injection atomic fluorescence spectrometry system (illustrated). The analytical procedure consisted of injection of 0.5 mL of 3 M HCl to elute the retained organomercury species which were then converted into inorganic Hg species by a bromide - bromate reagent. The inorganic Hg was merged with tin chloride before detection by cold vapor AFS.
Mercury Fluorescence Spectrophotometry

"Elaboration Of A Method For Electroenzymatic Flow Injection Analysis Of Glucose"
Analusis 1991 Volume 19, Issue 1 Pages 31-36
Le Marrec, J.H.;Lesgards, G.

Abstract: The thin-layer amperometric cell used is illustrated. The glucose oxidase was covalently attached (by the glutaraldehyde method) to a Nytal HC 48 (nylon 6) membrane, which was fitted in a cell. A three-electrode assembly was used, with a platinum indicator electrode, at +0.7 V vs. the Ag/AgCl reference electrode, and a stainless-steel counter electrode (part of the cell block). The buffer, 0.1 M phosphate, pH 6, was pumped at 1 mL min-1 at 30°C and samples of 150 µL were injected at 66 h-1. Under these conditions, the detector response was rectilinear for 28 ng to 27 µg of glucose injected. For 1 mM glucose standard solution, the coefficient of variation (n = 7) was 8.6%. The indicator electrode required electrochemical treatment after 8 h use, due to passivation. There was minor interference from maltose and mannose and significant interference from the oxidation of ascorbate at +0.7 V.
Glucose Amperometry Electrode

"Thermospray Liquid Chromatography - Mass Spectrometry Of Polar β-blocking Drugs: Preliminary Results"
Biol. Mass Spectrom. 1991 Volume 20, Issue 10 Pages 647-649
M. S. Leloux, W. M. A. Niessen, R. A. M. van der Hoeven

Abstract: The influence of either vaporizer temperature (90 to 120°C) or repeller potential on analyte signals and mass spectra of five β-blocking drugs was investigated by delivering the compounds (200 ng) to a thermospray interface to a triple quadrupole mass spectrometer using flow injection analysis in a stream (1.2 mL min-1) of methanol - 50 mM ammonium acetate (1:1) adjusted to pH 3.0 with formic acid. The fragmentation patterns were strongly dependent on the instrumental parameters which were optimized at 100°C and 50 V for vaporizer temperature and repeller potential, respectively. For LC - MS studies aqueous solution of atenolol (0.2 to 200 ng) and propafenone (200 ng), used as internal standard, were delivered to the interface by HPLC on a column (10 cm) packed with Nova-Pak CN-HP (4 µm) and operated with the same mobile phase but in the ratio 2:3. Absolute detection limits for atenolol were 0.2 ng using selected ion monitoring of m/e 267 or 2 ng for full-scan analysis. The calibration curve was rectilinear over the range 0.2 to 200 ng and the coefficient of variation (n = 8) for the injection of propafenone was 9.6%. Acebutolol, administered orally to subjects, was detected in urine together with its major metabolite diacetolol.
Drugs Urine HPLC Mass spectrometry

"A New Method For The High Performance Liquid Chromatographic Determination Of TA-870, A Dopamine Prodrug"
Biomed. Chromatogr. 1990 Volume 4, Issue 5 Pages 181-187
Masayoshi Yoshikawa, Hiroshi Endo, Kumiko Hoshino, Yoichi Sugawara, Osasi Takaiti, Susumu Kanda, Kazuhiro Imai

Abstract: A new method for the high performance liquid chromatographic (HPLC) determination of N-(N-acetyl-L-methionyl)-O,O-bis(et hoxycarbonyl)dopamine (TA-870), a dopamine prodrug, in biological fluid has been developed. In order to measure with an electrochemical detector (ECD), TA-870 was passed first through an immobilized carboxylesterase column to be converted to the electrochemically active deethoxycarbonylated TA-870 (DEC-TA-870). The properties of this carboxylesterase immobilized on Sepharose 4B were examined by this flow injection system. Hydrolysis of TA-870 with this immobilized carboxylesterase was a maximum at pH 7-8 and 50°C, and the activity decreased in the presence of organic solvent such as acetonitrile. For the determination of TA-870 in biological fluids, an HPLC-immobilized enzyme-ECD system using a column-switching technique was developed. The blood was deproteinized with ethanol, and TA-870 in the ethanol extracts was adsorbed in Bond Elut C18. The dichloromethane eluate from Bond Elut C18 was injected into the HPLC system. The HPLC apparatus was composed of three pumps, two separation columns (LiChrosorb Si 60 and µBondasphere), a trap column (Bond Elut), an enzyme column, ECD and the column-switching system. The calibration curve for TA-870 in blood was linear in the range from 2 to 200 ng/mL. This new assay method might be useful also for the determination of other catechol ester compounds.
Drugs N-(N-acetyl-L-methionyl)-O,O-bis(ethoxycarbonyl)dopamine Blood HPLC

"Determination Of Aspartame In Dietary Food Products By A FIA Biosensor"
Biosens. Bioelectron. 1991 Volume 6, Issue 2 Pages 117-123
K. B. Male, J. H. T. Luong* and A. Mulchandani

Abstract: A flow injection analysis (FIA) biosensor system was developed for the determination of the artificial sweetener aspartame (N-L-α-aspartyl-L-phenylalanine methyl ester). The system consisted of two enzyme columns, containing purified peptidase and aspartate aminotransferase respectively, immobilized on activated aminopropyl glass beads and an enzyme electrode connected in series. The dipeptide bond of aspartame was cleaved by immobilized peptidase to release aspartic acid which was in turn transaminated by aspartate aminotransferase. The glutamate produced by transamination was monitored by the enzyme electrode which used L-glutamate oxidase immobilized on a nylon membrane in combination with a hydrogen peroxide electrode. The response of the FIA biosensor was linear up to 1 mM aspartame with a lower detection limit of 20 micromole and had good reproducibility (RSD2.2%). The FIA biosensor was stable for at least 30 h of continuous use at room temperature and the immobilized enzymes were stable for at least 1 month when stored in buffer at 4°C. Each assay takes ~7-8 min giving a sample through put of 8 h-1. When applied to aspartame measurements in dietary food products, the results obtained agreed well with those reported by the product manufacturer. The flow injection analysis system described contains two enzyme columns, containing purified peptidase and aspartate aminotransferase, respectively, immobilized on activated aminopropyl glass beads, and an enzyme electrode of L-glutamate oxidase immobilized on a nylon membrane in combination with a H2O2 electrode. The immobilization of the enzymes and the purification of the aspartame peptide-bond-cleaving enzyme are detailed. The effects of pH, flow rate, α-ketoglutarate and column length on the flow injection analysis response were measured. The calibration graph was rectilinear up to 1 mM aspartame, with a detection limit of 20 µM and a coefficient of variation (n=8) of 2.2%. The biosensor was stable for at least 30 h of continuous use at room temperature and the immobilized enzymes were stable for at least 1 month when stored in buffer at 4°C. Each assay takes 7-8 min. The method was applied to dietary food products.
Aspartame Food Electrode Sensor

"Electrochemistry And Detection Of Some Organic And Biological Molecules At Conducting Poly(3-methylthiophene) Electrodes"
Biosens. Bioelectron. 1991 Volume 6, Issue 4 Pages 333-341
Nada F. Atta, Ahmed Galal, A. Ersin Karag&ouml;zler, George C. Russell, Hans Zimmer and Harry B. Mark, Jr*

Abstract: Electrodes modified by the electrodeposition of poly(3-methylthiophene) were used as chemical sensors for some organic and biological molecules of industrial and medicinal interest. The electrochemical behaviors of ferri/ferrocyanide, catechol, ascorbic acid, hydroquinone, dopamine, epinephrine, acetaminophen, p-aminophenol and NADH were examined by cyclic voltammetry. The results showed that the proposed modified surface catalyzes the oxidation of these compounds. Differential pulse and square wave techniques were used for the analysis of binary mixture of ascorbic acid with catechol, NADH, dopamine and p-aminophenol. Voltammetric peak resolution was also demonstrated for a ternary mixture of ascorbic acid, catechol and p-aminophenol. Polymer coated electrode was also used in an amperometric detector for flow injection analysis of most of the aforementioned compounds. The responses of the polymer electrode were 4-10 times larger as compared to those of platinum. The modified electrode displayed excellent response stability for successive injections and detection limits were 10 ppb for catechol, dopamine, epinephrine, NADH and p-aminophenol, 1 ppb for acetaminophen and 100 ppb for ascorbic acid. Voltammetric peak positions were affected by the nature of the electrolyte and its pH. Also, film thicknesses were shown to be a factor affecting both the current magnitudes and oxidation peak potential of NADH.
Acetaminophen Ascorbic acid Catechol Dopamine Epinephrine Ferricyanide Ferrocyanide Hydroquinone Nicotinamide adenine dinucleotide oxidized 4-Aminophenol Amperometry Amperometry Electrode Voltammetry Sensor

"Electrostatically Immobilized Hexacyanoferrate Ions As Redox Mediators In Biochemical Sensing: Controlled Release And Cyclic Voltammetric Behaviour"
Biosens. Bioelectron. 1991 Volume 6, Issue 7 Pages 589-594
Dale W. Harak and Horacio A. Mottola*

Abstract: The release rate of Fe(CN)63-, immobilized on the anion exchangers poly-(4-vinylpyridine) (I), Dowex 1-X8 and QAE-Toyopearl-550 c, into the carrier solution in continuous-flow systems was investigated. After 1 h, >65% of the Fe(CN)63- 'bleeding' from I initially observed was still maintained, and the concentration. in the carrier solution was ~10 µM; for the other two ion exchangers the Fe(CN)63- concentration. in the carrier at this stage was in the range 0.2 to 0.3 µM. The ease of electron transfer from and to the immobilized redox mediator was also investigated by examining the cyclic voltammetric behavior of Fe(CN)63- immobilized on the three materials. A modified carbon-paste working electrode containing 70% of graphite, 25% of mineral oil and 5% of immobilized material was used, and the supporting electrolyte was 0.01 M phosphate buffer containing 0.05 M KCl. For mediation at low pH, the QAE-Toyopearl support was preferable, but for release from a solid reservoir at pH ~7, I was preferred.
Hexacyanoferrate(III) Electrode Sensor Voltammetry

"Assay Of β-galactosidase Activity By Flow Injection Analysis"
Biotechnol. Techniq. 1991 Volume 5, Issue 5 Pages 389-392
J. Cair&oacute;, M. Vidal, A. Villaverde, F. Valero, F. J. Lafuente and C. Sol&agrave;

Abstract: A novel method to analyze β-galactosidase by Flow Injection Analysis is presented with a linear working range extended to at least 2150 U/mL, being the detection limit 25 U/mL with 55 samples per hour frequency and a RSD of 0.54% versus 2.4% obtained by manual assay. The method was tested with optimal results with samples from Escherichia coli cultures producing β-galactosidase.
Enzyme, galactosidase Fermentation broth Spectrophotometry

"Spectrophotometric Flow Injection Analysis Measurement Of Ethanol Content In Distilled Alcoholic Beverages Using Sulfonazo-III-barium Complex"
Bunseki Kagaku 1990 Volume 39, Issue 10 Pages 597-599
Zenki, M.;Sakita, E.;Hironaka, T.;Toei, K.

Abstract: Sample solution (180 µL) was injected into a carrier stream (0.5 mL min-1) of water and reacted with a reagent solution (0.5 mL min-1) of 0.01 M acetate buffer (pH 3.5) containing 0.1 mM sulfonazo III and 40 µM of Ba2+ with detection at 640 nm. The calibration graph was rectilinear up to 50% of ethanol. Coefficients of variation (n = 5) for 10 and 30% ethanol were 0.51 and 0.87%, respectively. The results obtained agreed well with certified values.
Ethanol Beverage Spectrophotometry

"Simultaneous Determination Of L-malate And Ethanol In Wine By A Sensor Based On Oxygen Consumption Including Parallel Configuration Of Enzyme Columns"
Bunseki Kagaku 1990 Volume 39, Issue 11 Pages 723-727
Ukeda, H.;Nakada, Y.;Matsumoto, K.;Osajima, Y.

Abstract: A flow injection analysis system (illustrated) was developed consisting of two parallel enzyme reactors with a single O electrode. L-Malate (I) was determined by injecting sample solution into a carrier stream of 0.05 M pyrophosphate buffer (pH 9.0) saturated with vitamin K3 (0.5 mL min-1). The stream was mixed with NAD solution and the mixture was passed through a malate dehydrogenase - diaphorase enzyme reactor. Ethanol (II) was determined by injecting sample solution into a stream of 0.05 M phosphate buffer (pH 8.0; 1.0 mL min-1) and the mixture was passed through an alcohol oxidase enzyme reactor. Sample solution was injected simultaneously into both reactors. Calibration graphs were rectilinear from 90 to 900 µM I and from 18 to 50 mM II. The method was applied in the simultaneous determination of I and II in wine. Results were compared with those by HPLC and the F-kit method.
l-Malate Ethanol Wine Electrode HPLC Sensor

"Determination Of Saponification Value Of Oils By FIA"
Bunseki Kagaku 1991 Volume 40, Issue 1 Pages 49-52
Katafuchi, A.;Imato, T.;Yagi, J.;Takahara, K.;Ishibashi, N.

Abstract: An ester solution (200 µL) was injected into an ethanol carrier stream (0.25 mL min-1) and merged with an ethanol stream containing 0.1 M tetrabutylammonium hydroxide (0.25 mL min-1). After mixing at 100°C in a 50-m reaction coil the stream was merged with 0.1 M butyric acid - ethanol containing 0.1 M LiCl and 0.2 µM-methyl red (0.5 mL min-1). The pH or absorbance of the mixed stream was measured at a glass electrode and/or at 490 nm. Calibration graphs were rectilinear from 0.02 to 0.1 M lauric acid ethyl ester; coefficient of variation was 1.3%. The sampling rate was ~20 samples h-1. The method was applied in the analysis of butter.
Fatty acids Food Electrode

"Spectrophotometric Determination Of Copper In Solutions Of High Salt Concentration By A Reversed Flow Injection Method"
Bunseki Kagaku 1991 Volume 40, Issue 10 Pages T179-T182
Sayama, Y.;Hayashibe, Y.;Takeya, M.

Abstract: Zinc electrolyte (containing 150 g L-1 of Zn) was introduced into a flow injection system at 0.3 mL min-1, diluted six-fold with 0.25 M H2SO4 (1.5 mL min-1) and adjusted to pH 5 with 2 M ammonium acetate - 0.5 M ammonium citrate buffer. The resulting solution was merged with 0.05% sodium 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline disulfonate - 10% L-ascorbic acid solution and passed through a reaction coil (1 m x 2 mm) before the absorbance of the mixture was measured at 525 nm. Results agreed well with those obtained by ICP-AES. The coefficient of variation for determination of 0.5 µg mL-1 of Cu was 2.0%; the detection limit was 0.1 µg mL-1 of Cu. Sample throughput was 50 h-1.
Copper Spectrophotometry

"Determination Of Beryllium In Aluminum Metals With 2-hydroxy-1-naphthaldehyde And Methylamine By Flow Injection Fluorimetry"
Bunseki Kagaku 1995 Volume 44, Issue 8 Pages 633-639
Watanabe, K.;Ikai, T.;Itagaki, M.

Abstract: The sample solution (0.4 ml), containing fluoride and hexasodium triethylenetetramine-NNN'N''N'''N'''-hexaacetate, is injected into a carrier stream of water (1.6 ml/min) that then merges with streams (each 0.2 ml/min) of 2.5 mM 2-hydroxy-1-naphthaldehyde in 1,4-dioxane and aqueous 1.5 M methylamine, and after passage through a 0.5 m reaction coil the fluorescence intensity of the merged streams (pH 11.0) is measured at 435 nm in a 27 µL flow cell (excitation at 365 nm). Concentrations of Be >1.8 ppm in aluminum can be determined.
Beryllium Metal Fluorescence

"Spectrophotometric Determination Of Peroxydisulfate With O-dianisidine By Flow Injection"
Can. J. Chem. 1990 Volume 68, Issue 10 Pages 1750-1756
Paul M. Shiundu, Adrian P. Wade, and S.B. Jonnalagadda

Abstract: The method is based on the Cu(II)-catalyzed oxidation of o-dianisidine (I) by S2O82- (II) in the flow injection system of Wentzell et al. (J. Autom. Chem., 1989, 11, 227) to give a product with λmax = 450 nm. The sample (e.g., 100 µL) was injected into a stream of 0.5 mM Cu(II) (1.5 mL min-1) and mixed with a stream of 10 mM I (0.5 mL min-1) in aqueous 40% acetone in a 50-cm coil before being mixed with a stream of 0.1 M 3,3-dimethylglutaric acid (0.5 mL min-1) in 1 M NaCl (pH adjusted to 7.0 with NaOH) in a further 50-cm coil. The manifold was constructed from PTFE tubing (i.d. 0.5 mm). Calibration graphs based on the absorbance at λmax were rectilinear for 25 to 750 µM-II; the detection limit was 0.5 µM. In the determination of 25 µM-II the coefficient of variation was 1.5% (n = 10). There was little interference from 2.5 M methanol, 1.0 M ethanol or 0.25 M prop-2-en-1-ol, some interference from 0.25 M prop-2-enyl acetate and 0.5 M ethyl acetate and serious interference from formaldehyde.
Peroxydisulfate Polymer Spectrophotometry

"Hydroxylaminolysis Of β-lactams And Its Use For The Determination Of Penicillins By Flow Injection Analysis"
Cesk. Farm. 1990 Volume 39, Issue 2 Pages 77-79
Karlicek, R.;Solich, P.

Abstract: A three-stream (0.6 mL min-1 each) system was used, containing three coils in series, of length 25, 50 and 100 cm (A, B and C, respectively). A sample (85 µL) was injected into a stream of reagent solution of pH 6.2 composed of 0.1 M hydroxylammonium chloride and 0.15% Brij-35 in aqueous 25% ethanol, the mixture was passed through reaction coil A (for hydrolysis of β-lactam rings), then acidified to pH ~1 by mixing with a stream of 0.5 M H2SO4 in coil B, merged with solution comprising 12.8 g of (NH4)2Fe(SO4)2 and 1 mL of 15% Brij-35 in 100 mL of 0.05 M H2SO4 - ethanol (3:1), and passed through coil C. The absorbance of the colored complex formed with Fe(III) was measured at 505 nm. Calibration graphs were rectilinear for 0.25 to 3 mg mL-1 of ampicillin, benzylpenicillin, procaine penicillin or phenoxymethylpenicillin, and the detection limits were ~0.1 mg mL-1. The coefficient of variation (n = 6 to 10) were 1.5% for ~1 mg mL-1 of individual penicillins. The method is suitable for analysis of pharmaceuticals; throughput is 50 h-1.
Penicillins Ampicillin Benzylpenicillin Penicillin procaine Phenoxymethylpenicillin Pharmaceutical Spectrophotometry

"An Automated Glucose Isomerase Reactor System With Online Flow Injection Analyzers For Monitoring Of PH, Glucose And Fructose Concentrations"
Chem. Eng. Sci. 1990 Volume 45, Issue 4 Pages 1031-1042
Jens Gram and Michael de Bang, John Villadsen*

Abstract: The literature on glucose isomerization with immobilized glucose isomerase has been reviewed with respect to thermodynamics and kinetics of the reaction and the industrial process layout. A laboratory scale fixed-bed reactor for isomerization of glucose with immobilized glucose isomerase has been constructed. A system for sample withdrawal and three flow injection analyzers-measuring glucose, fructose and pH-has been developed, automated and used to monitor the process. The equipment is controlled by a personal computer with interface expansion boards. The isomerization process has been monitored in steady-state operation as well as in pH transients. Using a commercial immobilized glucose isomerase (Sweetzyme Q from NOVO Industri A/S), the isomerization process has been studied with respect to equilibrium conversion, composition of the feed syrup, film diffusion resistance, enzyme deactivation and buffering effect of the immobilized enzyme. The experience from computerization of the equipment and the use of flow injection analyzers is summed up and the potential of such analyzers for monitoring biotechnological processes is discussed.
pH Glucose Fructose

"Amberlite XAD-2 Resin Microcolumn Coupled Online To A Flow Injection Approach For The Preconcentration, Cleanup And Determination Of Trace Phenols In Waters"
Gaodeng Xuexiao Huaxue Xuebao 1997 Volume 18, Issue 10 Pages 1621-1623
Song, W.L.;Wang, L.S.;Zhi, Z.L.

Abstract: A novel and expeditious approach for direct determination of phenols in water and waste water based on solid-phase extraction coupled to a flow injection analysis (FIA) manifold is described. The method employs online pre-concentration of phenols using a 3 cm X 3 mm column packed with Amberlite XAD-2 resin. The phenols are subsequently eluted from the resin into a flowing system with an alkaline solution and quantified spectrophotometrically as the products of reaction with 4-aminoantipyrine (4-AAP) system. The sensitivity offered by the procedure was higher by a factor of pH=13 than that provided by a conventional FIA method. 5 References
Phenols Waste Spectrophotometry Sample preparation

"Chemiluminescence Of Tryptophan With Electrogenerated Tris(2,2'-bipyridine)ruthenium(III)"
Chem. Lett. 1991 Volume 20, Issue 8 Pages 1373-1376
Kazuo Uchikura and Makoto Kirisawa

Abstract: Determination of tryptophan (I) and its related compounds was carried out in a two-channel FIA system equipped with a chemiluminescence detector. The method was based on the electrochemical oxidation of 0.24 M tris(2,2'-bipyridine)ruthenium(III) in 10 mM H2SO4 by reaction with I. The carrier solution consisted of a mixture of 10 mM H3PO4 - acetonitrile (1:1) to which a current of 80 µA was applied. The resulting orange chemiluminescence was measured. The effect of pH, flow rate and concentration. of reagent on the intensity was investigated. The detection limit of I was 0.1 pM; calibration graphs were rectilinear up to 200 pM. The method was also applied in the determination of other substituted indoles, but with inferior sensitivities.
Tryptophan Chemiluminescence

"Basic Principles Of Optical-fiber Biosensors And Their Application In Determination Of D-glucose"
Chem. Listy 1996 Volume 90, Issue 5 Pages 295-306
Chudobova, I.;Vrbova, E.

Abstract: A review concerns basic concepts of fiber optic biosensors and presents them on the examples of glucose biosensors. Glucose biosensors can serve as the model system and the source of inspiration for construction of fiber optics biosensors focused on less common analytes. Typical arrangement of an optical system, specific features of an optical fiber, and basic procedures used for immobilization of specific biological systems are discussed. Further, the detection of D-glucose is described and examples of both biocatalytic and affinity biosensors are shown. Biocatalytic glucose sensors are based mainly based on the enzyme reaction of glucose oxidase, less frequently on glucose dehydrogenase. Affinity glucose sensors use interaction of concanavalin A with different saccharides. Advantages and disadvantages of optical fiber biosensors and their fields of application are also mentioned.
Glucose Sensor Sensor

"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

"Study On Multiple-enzyme Electrode For Sucrose Determination"
Shengwu Gongcheng Xuebao 1991 Volume 7, Issue 4 Pages 339-344
Hu W, Zhang X, Zhang X, Hu S.

Abstract: Invertase (INV), mutarotase (MUT), glucose oxidase (GOD) and BSA were coimmobilized via glutaraldehyde-bridged covalent bonding, and directly absorbed on the teflon membrane. This membrane was covered with a nylon mesh and placed over an oxygen electrode. An enzyme electrode for flow injection analysis system (EFIA) was adopted. The optimum enzyme composition (IU) for immobilization on the teflon membrane of INV-MUT-GOD was found to be in the ratio 72:48:2.4, with a recovery activity INV-MUT of more than 42.9%. pH 5.8-6.5 was the most suitable range of acidity for the sensor activity. The optimum temperature was 35-45°C. The system exhibited good linearity in the range of 5 x 10^-4 approximately 10^-1 M sucrose (kinetic method) and 10^-5 approximately 2 x 10^-3 M sucrose (steady state method), in short response time (20 seconds for kinetic method, 2 minutes for steady state method), CV = 1.7% (kinetic method). The sensor had been used for determining sucrose concentration in fermentation broth, with an average recovery rate of 98%. The interference caused by the presence of glucose derived from decomposition of sucrose was eliminated by calibration with a GOD sensor. No significant loss of the enzyme electrode activity was observed after 120 hours of the continuous-flow of fresh 1 mM sucrose. The multiple-enzyme membrane showed a relatively long lifetime (compared with 14 hours as reported previously) and good storage stability (30 days, stored in distilled water at 4°C).
Sucrose Fermentation broth Electrode

"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

"Chromatographic Quantitation Of Free Amino-acids: S-methylmethionine, Methionine And Lysine In Corn"
Commun. Soil Sci. Plant Anal. 1991 Volume 22, Issue 17-18 Pages 1873-1882
Grunau, J.A.;Swiader, J.M.

Abstract: Dried, powdered corn kernels (500 mg) were extracted with 3.5% sulfosalicylic acid for 15 to 20 min at room temperature The mixture was centrifuged, the supernatant (3.0 ml) was combined with 20 mM canavanine as internal standard and 7 M NaOH to give pH 2.2, and the solution was pre-filtered then ultra-filtered. The extract was diluted 1:1 with Pickering Lithium Diluent (pH 2.20). The amino-acids and other ninhydrin-positive substances were analyzed on a modified HP1090 liquid chromatograph at 43°C, with gradient elution using Li citrate of pH 2.75 and 7.50 (0.30 mL min-1), post-column derivatization at 130°C with ninhydrin (0.3 mL min-1) and detection at 570 nm. The detection limit was 20 pM of S-methylmethionine (1 µM for a 20 µL injection). Free methionine and lysine were also measured.
Amino Acids Lysine Methionine S-Methylmethionine Maize HPLC

"Ion-chromatographic Analysis Of Alkali- And Alkaline-earth-metal Contents In Wine"
Dtsch. Lebensm. Rundsch. 1990 Volume 86, Issue 6 Pages 178-182
SCHAPER H.-H. ; SCHWEDT G.

Abstract: To determine Na or K, the sample was diluted 1:40 or 1:500, respectively (for Na, the sample was boiled with 30% H2O2 before dilution) and analyzed on a Dionex HPIC-CS1 - HPIC-CG1 column system with 5 mM HCl as mobile phase (2 mL min-1) and use of a hollow-fiber membrane suppressor. To determine Ca or Mg, the sample was diluted 1:20 to 1:50 and analyzed on a Partisil SCX (10 µm) column with 2.5 mM oxalic acid - 2 mM ethylenediamine (pH adjusted to 3.5 with HCl) as mobile phase (1 mL min-1) and photometric detection at 490 nm after post-column derivatization with Zn - EDTA - 4-(2-pyridylazo)resorcinol at pH 11.0. A determination by either method takes ~15 min. The simultaneous determination of all four cations can be achieved in 40 min on a LiChrospher RP-18 column with 2 mM hexylsuccinic acid - 1 mM oxalic acid as mobile phase and conductometric detection. The concentration. of Na, K, Ca and Mg found in wine were 3 to 20, 800 to 1500, 60 to 140 and 70 to 100 mg l-1, respectively.
Metals, alkaline earth Metals, alkali Magnesium Sodium Potassium Calcium Wine HPIC Spectrophotometry

"Continuous-flow Method For Simultaneous Determination Of Monochloramine, Dichloramine, And Free Chlorine: Application To A Water Purification Plant"
Environ. Sci. Technol. 1989 Volume 23, Issue 1 Pages 46-50
Toyoaki Aoki

Abstract: A continuous-flow system is described and illustrated, for simultaneous determination of chloramide (I), chlorimide (II) and free Cl in water, which incorporates three double-tube separation units, each consisting of a PTFE outer tube and an inner tube of micro-porous PTFE. The three tubes were used for determination of I, I plus II, and I, II and Cl, respectively, by reaction with I- and absorbance measurement at 288 nm. Optimum pH and reagent concentration. for each reaction are given. Calibration graphs covered the ranges from 0.1, 0.02 and 0.02 mg L-1 of Cl for I, II and free Cl, respectively, to 71 mg L-1 for all Cl species. Within- and between-run coefficient of variation were 3.3% (n = 5) and 10% (n = 8), respectively. The method was applied in monitoring of I and II in water purification plants.
Chloramide Chlorimide Chlorine, free Water Spectrophotometry

"Sequential Determination Of Residual Chlorine And Chloride In Tap-water By Spectrophotometric Flow Injection Analysis"
Fenxi Huaxue 1989 Volume 17, Issue 3 Pages 242-244
Ma, C.;Yang, J.;Zhao, Z.;Wang, J.;Wang, Q.

Abstract: To determine residual Cl, a water sample (320 to 400 µL) is injected into a carrier stream of water (6 mL min-1) to react with a stream (2.4 mL min-1) of 0.086% o-toluidine solution (containing a little HCl) in a 30-cm reaction tube; detection is at 438 nm. For subsequent determination of Cl-, the reagent stream is composed of 0.63 g of Hg(SCN)2, 30.3 g of Fe(NO3)3, 3.4 mL of HNO3, 15 mL of methanol and water to 1 l; otherwise, the same conditions are used. The method is simple, rapid and convenient and gives satisfactory results. To suppress decomposition of residual Cl, the sample should have a high pH (e.g., 9).
Chlorine Chloride Water Spectrophotometry

"Rapid Determination Of Trace Zinc In Tea By Flow Injection Micelle-modified Spectrophotometry"
Fenxi Huaxue 1990 Volume 18, Issue 4 Pages 362-365
Qi, W.;Chen, X.G.

Abstract: The flow injection analysis equipment is described in detail. It was used to determine trace Zn in the Zn - 1-(2-pyridylazo)-2-naphthol (I) - Triton X-100 system. The carrier stream was NH3 - NH4Cl buffer solution (pH 8.8) at 3 mL min-1, and this was mixed with the reagent stream of ethanolic 0.05% I - 10% Triton X-100 (50 ml) at 1.25 mL min-1. The masking agents, sodium hexametaphosphate, sodium citrate and ammonium aminoisopropionate were used to avoid interference by Mn(II), Cu(II) and Co(II). Flow injection analysis can be used to determine Zn in tea, which contains high concentration. of Mg and Mn, without pre-separation. The sampling rate is 180 h-1, and the coefficient of variation was 1.6%.
Zinc Plant 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

"Flow Injection Differential-kinetic Determination Of Lead With Meso-tetrakis(4-trimethylammoniumphenyl)porphyrin"
Fenxi Huaxue 1990 Volume 18, Issue 10 Pages 952-954
Mao, Q.K.;Zhang, C.;Cheng, J.K.

Abstract: Sample solution (170 µL) is mixed with 170 µL of the cited reagent (3 mM; I) each in carrier streams (1 mL min-1) of Na2B4O7 buffer solution (pH 10) in a reaction tube (15 m x 0.5 mm). The complex formed is detected at 465 nm vs. water. The working range was rectilinear up to 4 µg of Pb(II); the coefficient of variation was 0.3% for 1 µg of Pb and the sampling rate was 60 h-1. Tolerance levels of common ions are listed; there was little interference from Cd(II), Hg(II), Fe(III), Co(II), Ni(II), Zn(II), Cu(II) and Mn(II). The method was applied to the soaking extract of pottery and porcelain, and human hair.
Lead Hair Ceramic Ceramic Spectrophotometry Sample preparation

"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

"Flow Injection Analysis Of Amantadine With Use Of An Amantadine Flow-through Electrode"
Fenxi Huaxue 1991 Volume 19, Issue 2 Pages 200-202
Liu, W.Z.;Gao, J.Q.;Zhou, X.

Abstract: An electrode is described which consists of amantidine (I)-sensitive tropine - tetraphenylborate - PVC tubular membrane, with 1 mM I and 0.01 M NaCl filling solution and a Ag - AgCl electrode (illustrated). Sample (300 µL; adjusted to pH 3 to 8 with citric acid - Na2HPO4 - NaNO3 buffer) is injected into a carrier stream of 0.1 M NaCl - 1 µM-I (2 mL min-1) for detection at the electrode. The calibration graph was rectilinear from 10 µM to 0.1 M I. The method was applied to pharmaceutical preparations, with recoveries of 94.3 to 99.6% and coefficient of variation of 1.1%. Clonidine and benzalkonium bromide interfered. Results are compared with those obtained by argentometry.
Amantadine Pharmaceutical Electrode Electrode Electrode

"Chemiluminescence Determination Of Ammoniacal Nitrogen In Natural Waters By Flow Injection Analysis"
Fenxi Huaxue 1991 Volume 19, Issue 3 Pages 350-352
Liu Daojie, Liu Renmin

Abstract: The method is based on the chemiluminescent reaction between ClO- and luminol in Na2CO3 - NaHCO3 buffer solution (pH 10.8). Ammonia reacts with the ClO- to form monochloramine which decreases the luminescence intensity. A flow injection - chemiluminescence analysis system (diagram given) is described and analytical conditions are optimized. The method was successfully used to determine ammoniacal N in natural water; recoveries ranged from 86 to 95%. For determination of 10 µM-NH3, 100 mM NaCl and -KCl, 10 mM MgCl2 and -CaCl2, 5 µM-Ni2+, -Mn2+, -Fe3+ and -Fe2+ and 1 µM-Cu2+ were tolerated.
Nitrogen, ammonia Environmental Chemiluminescence

"Merging Zone Flow Injection Analysis Of Trace Copper - Catalytic System Of Iron(III) - Thiosulfate - Copper(II)"
Fenxi Huaxue 1991 Volume 19, Issue 4 Pages 468-470
Yuan, Y.;Wang, P.;Wang, Y.

Abstract: A flow injection system (diagram given) is described for the determination of trace Cu, based on the reaction of Fe3+ and S2O32- in the presence of Cu2+ as catalyst. Optimum sensitivity was achieved at 36°C to 38°C, pH 2 to 3 and with use of 0.025 M Fe3+ and 0.15 M Na2S2O3. The absorbance of the reaction solution was measured at 540 nm. The calibration graph was rectilinear up to 0.35 µg mL-1 of Cu; the detection limit was 0.01 µg mL-1. The coefficient of variation (n = 7) was 1.7% for the determination of 0.1 µg mL-1 of Cu. The method was applied in the analysis of seawater with recoveries of 95 to 103%. Up to 500-fold of Pb(II), Mn(II), Co(II), Ni(II), Zn(II), Cd(II) and Fe(II) did not interfere. Analysis time was 100 samples h-1.
Copper Sea

"Air-segmented Flow Injection Determination Of Trace Copper(II) By Catalytic Kinetic Reaction"
Fenxi Huaxue 1991 Volume 19, Issue 10 Pages 1173-1175
Zhi, Z.L.;Tian, L.C.;Wu, Q.

Abstract: Sample (0.1 g) was treated with HCl and HO3, the pH of the solution was adjusted to 1 to 2 by 1 M NaOH and 1 M HCl and the mixture was heated at 90°C for 5 min with 0.2% hydrazine sulfate. The mixture was diluted to 25 mL with water and a portion (60 µL) of the solution was carried by a stream of water (0.8 mL min-1) to react with 1 mM Fe(III) sulfosalicyclate and 7.5 mM Na2S2O3 (both at 0.3 mL min-1) at 40°C for 2.2 min with detection at 505 nm. The calibration graph was rectilinear up to 4 µg mL-1 of Cu. Recovery was 97 to 106% with a coefficient of variation of 1.5% and a detection limit of 0.1 µg mL-1. Little interference was observed. Results are compared with those of flame AAS. The method was applied in the determination of copper in some ores.
Copper(II) Geological Spectrophotometry

"Determination Of Free Cyanide In Mineral Leachates By Flow Injection-spectrophotometry"
Fenxi Huaxue 1998 Volume 26, Issue 3 Pages 314-316
Wang, J.W.;Lu, A.J.;Wu, H.L.;He, Y.

Abstract: In the medium of NaOH, free cyanide is reacted with Na picrate to form a rose-colored salt. The color-producing condition is optimized. Because the reaction is slow, two-line manifold system is set up and the temperature is controlled to improve reactive condition. Peak shape of two-manifold system is normal and smooth and may effectively forsake the formation of humped peak in comparison with single line manifold. The detection wavelength is 510 nm and the linear range of determination is 4.0-40.0 mmol/L. The sampling rate is 130 samples/h. The method was successfully applied to the determination of CN- in mineral leachates on the spot.
Cyanide, free Geological Sample preparation Spectrophotometry

"Coupled Flow Injection And High Performance Capillary Electrophoresis In The Analysis Of Traditional Chinese Medicine Cortex Magnoliae Officinalis"
Fenxi Shiyanshi 1998 Volume 17, Issue 2 Pages 1-4
Shen, Q.;Fang, Z.L.

Abstract: A FI-HPCE method was developed for traditional Chinese medicines. A new flow injection sample introduction interface was proposed for capillary electrophoresis. Using the FI-HPCE system, buffer concentration, pH, voltage and percentage of methanol were optimized to sep. magnolol and honokiol from other constituents in Cortex Magnolial Officinalis and their medicinal preparations The sample throughput was 10/h, the relative standard deviation at 138 µg/mL magnolol was 2.1% (n=6) and the recoveries were in the range of 96%~102.9%.
Magnolol Honokiol Chinese Electrophoresis

"Automation Of Iron And Copper Determination In Milks Using FIA Systems And Colorimetric Detection"
Food Chem. 1998 Volume 62, Issue 1 Pages 117-121
Jos&eacute; L. F. C. Lima, Cristina Delerue-Matos* and M. Carmo V. F. Vaz

Abstract: This paper describes a flow injection manifold with a colorimetric detection system that enables the determination of iron and copper in different types of milks, namely cow milk and infant formula powd. milks. The methodology used is based on the formation of colored complexes produced by the reaction of iron (II) with 1,10-phenanthroline and copper(II) with 1,5-diphenylcarbazide. The samples were digested with nitric and sulfuric concentrated acids and inserted in the FIA system without additional treatment. The pH adjustment was carried out inside the manifold including the addition of the reagents needed to form the absorbing species. The sample rate of both species was never lower than 120 determinations h-1. The results obtained were compared with those given by the reference methods, and the relative deviation was less than 5 and 4% for the determinations of iron and copper respectively. The precision of the results evaluated by the relative standard deviation (RSD%) was less than 0.5% for iron and 2% for copper determinations
Iron(2+) Copper(II) Cows Milk Powder Spectrophotometry Sample preparation

"Flow Injection Spectrofluorimetric Determination Of Terbium(III) With Ethylenediamine Bis-(o-hydroxyphenylacetic Acid)"
Fukuoka Joshi Daigaku Kaseigakubu Kiyo 1989 Volume 20, Issue 1 Pages 29-33
Aihara, M.;Kobayakawa, M.;Taketatsu, T.

Abstract: Sample solution (100 µL) containing 0.1 to 10 µM Tb(III) were injected at 40 h-1 into a stream (0.8 mL min-1) of 0.1 mM HCl and mixed with 0.6 mM ethylenediaminebis(o-hydroxyphenylacetic acid) (pH 7.7) in a reaction coil (2 m x 0.5 mm) and the chelate formed was determined fluorimetrically at 545 nm (excitaion at 295 nm). Equimolar amounts of other rare-earth ions did not interfere. The coefficient of variation was 1.2%.
Terbium(III) Fluorescence

"Simultaneous Determination Of Trace Amounts Of Mercury, Cadmium And Zinc By Ion Chromatography Using M-tetrakis(4-sulfophenyl)porphyrin [TPPS4] As Post-column Derivatization Agent"
Gaodeng Xuexiao Huaxue Xuebao 1990 Volume 11, Issue 2 Pages 136-139
Yan, D.;Zhang, J.;Schwedt, G.

Abstract: The cited determination was carried out with use of TPPS4 as derivatization agent, 4-(2-pyridylazo)resorcinol in Na2B4O7 - NaOH buffer (pH 10.3 to 12) containing NaCl as the derivatization catalyst and tartaric acid - NaCl as mobile phase. A chemically bonded silica gel cation-exchanger was used as the stationary phase and the separation was completed in 10 min. The method was applied to the analysis of waste water, silicate and corn samples.
Mercury Cadmium Zinc Waste Silicate Corn HPIC

"The Kinetics Of Dissolution Of UO2 Under Reducing Conditions And The Influence Of An Oxidized Surface Layer (UO2+x) - Application Of A Continuous-flow-through Reactor"
Geochim. Cosmochim. Acta 1991 Volume 55, Issue 3 Pages 647-658
Jordi Bruno*, Ignasi Casas

Abstract: We have studied the kinetics of dissolution of uranium dioxide, UO2(s), under strongly reducing conditions (H2(g)/Pd). We have investigated the dependence of the rate of dissolution as a function of critical geochemical parameters: pH, pCO2, and carbonate concentration. By using a stirred batch reactor, the kinetics of dissolution of an UO2+x surface layer and the subsequent precipitation of UO2 have also been studied. Although the initial UO2 is pretreated before starting the experiments, it seems to be very difficult to avoid the formation of the oxidized surface layer. For this reason we have developed a thin layer continuous flow-through reactor in order to study the kinetics of dissolution of pure UO2(s). The dependence of the rate of dissolution of these solids on the proton concentration of the solution may be expressed according to the following equations: rdiss(UO2)(mol sec-;1 m-;2) = 1.4(±0.3) x 10^-8[H+]0.53 ± 0.08 (3 less-than-or-equals, slant pH less-than-or-equals, slant 7)rdiss(UO2)(mol sec-;1 m-;2) = 1.9(±0.8) x 10^-12 (7less-than-or-equals, slant pH ≤ 11)rdiss(UO2+x)(mol sec-;1 m-;2) = 1.1(±0.3) x 10^-12 [H+]-;0.30 ± 0.02 (3 ≤ pH ≤ 9) mechanism of dissolution of these solids is surface controlled. rate of dissolution of UO2 in acidic solutions may be described in terms of an integer dependence on the activity of the protonated surface complexes: rdiss(UO2)(mol sec-;1 m-;2) = 1.11 x 1013 {>UOH2+}+ (2 ≤ pH ≤ 6)
Uraninite

"Determination Of Cobalt In Serum By Flow Injection Chemiluminescence Analysis"
Guangpuxue Yu Guangpu Fenxi 1991 Volume 11, Issue 1 Pages 21-23
Liang, G.Y.;Liu, Y.;Xiao, C.;Zhou, Y.K.

Abstract: The cited determination was completed with use of 0.03 M luminol and 0.04 M H2O2 (pH 9 to 11) and a GJ-II faint-light meter for light intensity measurements. The calibration graph was rectilinear for 0.0004 to 50 µg mL-1 of Co2+ and the detection limit was 0.1 ppb. No interference was observed from K+, Na+, Ca2+, Mg2+, SO42-, PO43- and Cl- but a 10-fold excess of Cu2+, Cr3+, Zn2+ and Fe3+, did interfere. A 0.05 M citric acid solution was used as masking reagent for Cu2+, Fe3+ and Zn2+ in serum. The recovery was 98.6%, with a coefficient of variation of 2.7%.
Cobalt Blood Serum Chemiluminescence

"Comparison Of Active Aluminum Species In Coniferous Forest Soils Of Different Districts"
Huanjing Huaxue 1992 Volume 11, Issue 3 Pages 48-54
Ma Huichang, Feng Jianzhang, Wu Hua, Pang Shuwei

Abstract: Active Al species were leached from the cited soils with four different extractants before determination by flow injection analysis. The acidity of the soil had a significant effect on the amount of Al leached; the effect of chemical species on the determination was also evaluated.
Aluminum, labile Environmental Sample preparation

"Study On A Chemiluminescence System Of Luminol - Sodium Perchlorate - Potassium Iodide - Hydroxide Ions For Determination Of Platinum"
Huaxue Shiji 1991 Volume 13, Issue 1 Pages 50-52
Li Qingyi,and Liu Yingjin

Abstract: Platinum was determined by flow injection chemiluminescence with use of a reagent solution (comprising 8 mL of 1 M luminol solution in 0.1 M KOH, 20 mL of 1 mM KOH and water to 100 ml) and a test solution (containing 5 mL of KH phthalate - KOH buffer solution of pH 5.5, 2.5 mL of 0.2 M NaClO4, 1 mL of 50 mM KI, Pt(IV) solution and water to 25 ml). Under optimum conditions, the calibration graph was rectilinear from 0.04 to 2.4 and from 0.8 to 8.0 µg of Pt. The detection limit was 27 ng and the coefficient of variation (n = 9) was 1.9%. The effects of 28 common ions on the determination of Pt were investigated. The method was used to determine trace Pt(IV) in catalysts; recoveries were 99.2 to 100.6%.
Platinum Industrial Chemiluminescence

"Sensitive And Selective Fluorescence Detection Of Phenoxy-acid Herbicides By Liquid Chromatography With Online Ion-pair Extraction"
Int. J. Environ. Anal. Chem. 1991 Volume 43, Issue 2-3 Pages 79-90
C. De Ruiter; W. A. Minnaard; H. Lingeman; E. M. Kirk; U. A. Th. Brinkman; R. R. Otten

Abstract: Optimization of an online ion-pair extraction system for phenoxy herbicides was carried out using a flow injection system. Aqueous sample solution was subjected to LC on a column (15 cm x 3.1 mm) of Hypersil MOS (3 µm) with aqueous 55% methanol (pH 2.5) as mobile phase (0.6 mL min-1). The eluate was merged sequentially with a reagent stream (0.6 mL min-1) comprising 12.5 µM-quaternary ammonium analogue of naphthalene-2,3-dicarboxaldehyde (prep. described) in 10 mM sodium phosphate buffer of pH 8 containing 2.5% methanol and an extraction solvent (1 mL min-1) of CHCl3 - butan-1-ol (4:1). The fluorescence intensity of the resulting extract was monitored at 470 nm (excitation at 260 nm). Calibration graphs were rectilinear for 1 to 100 ng of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid; the detection limit for both analytes was 400 pg. The method was applied to drinking water.
Herbicides, phenoxy acids Water LC Fluorescence Sample preparation

"Inline Alkalinity Measurement In Lime Milk By A FIA Technique"
Int. Sugar J. 1991 Volume 93, Issue 1115 Pages 238-240
Bengtsson, M.

Abstract: The design and operation of a flow injection analysis system is described. Samples of limed sugar juice were titrated with a pH buffer (0.3 M Tris and 0.3 M glycine), the pH changes having a linear response to alkali addition. The sensitivity of the system is dependent on the buffer concentration. and can be increased or decreased by using a lower or higher concentration, respectively; NaCl was added to maintain constant I. Samples (40 µL) were injected into the flowing buffer solution and monitored using a detector cell with a pH electrode. Results were obtained from a calibration graph prepared from peak height measurements of NaOH standards. Results were compared with those obtained by manual titration.
Alkalinity Juice Electrode

"Flow Injection Analysis Of MWC Fly Ash Leaching Characteristics"
J. Air Waste Manage. Assoc. 1995 Volume 45, Issue 11 Pages 871-876
Willemin, J.A.;Nesbitt, C.C.;Dewey, G.R.

Abstract: A completely mixed batch reactor leaching method utilizing flow injection analysis (the CMBR-FIA method) was developed to study the lead leaching characteristics of municipal waste combustor fly ash. Flow injection analysis coupled with atomic absorption spectrophotometry enabled the determination of lead concentrations at one minute intervals. The pH and oxidation-reduction potential of the solution were continuously monitored to characterize the leaching conditions. Automatic titration was used to alter the solution pH to defined endpoints. The CMBR-FIA method offers the ability to immediately observe alterations to the leaching solution, and grants the freedom to study a number of parameters concurrently. The CMBR-FIA method is a rapid and reliable means to investigate leaching characteristics. This paper describes the method and demonstrates its use to monitor the leaching of lead from municipal solid waste combustor fly ash as a function of pH. Soluble lead concentrations are shown to increase quickly with decreasing pH. A maximum of 50% of the total lead concentration was available in solution at pH 2. This value gradually decreased with time to over 35% of the total. (16 references)
Lead Coal Fly ash Spectrophotometry

"Determination Of Free (pH 2.2) Sulfite In Wines By Flow Injection Analysis: Collaborative Study"
J. AOAC Int. 1990 Volume 73, Issue 2 Pages 223-226
Sullivan, J.J.;Hollingworth, T.A.;Wekell, M.M.;Meo, V.A.;Etemad Moghadam, A.;Phillips, J.G.;Gump, B.H.

Abstract: A method for the determination of free sulfite in wine by flow injection analysis (FIA) is described. The method involves liberation of sulfur dioxide from the wine at pH 2.2, with detection by decolorization of a malachite green solution. The method was collaboratively studied, and the results indicated an average reproducibility of 12% for white wine samples (average level 12.1 ppm SO2) and 26% for red wine samples (average level 3.1 ppm). When the FIA method was compared to an aeration/oxidation method, the results indicated a high degree of correlation between the 2 methods. The FIA method has been adopted by AOAC official first action. Red or white wine was injected into a flow injection analysis (FIA) system and mixed with 0.5 M citric acid reagent (pH ~2). The SO2 produced diffused across a PTFE membrane in a gas diffusion cell into a flowing stream of malachite green solution. The degree of decolorization, which was proportional to the amount of SO2, was measured spectrophotometrically. Data from 7 laboratories indicated an average reproducibility of 12% for white wine (mean 12.2 ppm SO2) and 26% for red wine (mean 3.1 ppm). The results agreed with those from an aeration/oxidation method. It is recommended that the FIA method be adopted official first action, with the note that the method measures both free SO3-2 and any combined SO3-2 that is labile under the conditions used.
Sulfite Wine Red Wine White Spectrophotometry

"Polyvinyl Chloride Matrix Membrane Electrodes For Manual And Flow Injection Analysis Of Chloroquine In Pharmaceutical Preparations"
J. AOAC Int. 1991 Volume 74, Issue 6 Pages 900-905
Hassan SS, Ahmed MA.

Abstract: Two types of polyvinyl chloride (PVC) matrix membrane electrodes responsive to the antimalarial drug chloroquine have been constructed, electrochemically evaluated, compared and used in pharmaceutical analysis. Type 1 is the classic PVC model with chloroquine-tetraphenylborate (TPB) sensor; Type 2 is a coated silver disk without internal filling solution. Both electrode types exhibited rapid linear potentiometric response to the logarithmic concentration of diprotonated chloroquine cation in the 10^-1 - 10^-6 M range with calibration slopes 28-30 mV/concentration decade over the pH range 1.8-6.2. These electrodes were sensitive enough to permit determination of chloroquine phosphate at concentrations as low as 5µg/mL with good accuracy and precision. Determination of chloroquine in various pharmaceutical preparations using direct potentiometry and potentiometric titration with NaTPB gave an average recovery of 98.8% of the nominal values (SD 0.5%). The Type 2 electrode was also assessed in a flow-through sandwich cell for flow injection analysis. Results were compared with data obtained by the U.S. Pharmacopeia method. Two membrane electrodes are described, both incorporating a PVC membrane plasticized with dioctyl phthalate and containing the chloroquine (I) - tetraphenylborate ion-pair complex: a conventional membrane electrode with 5 mM chloroquine phosphate - 5 mM KCl as filling solution, and a membrane-coated Ag-disc all-solid-state electrode. Both electrodes gave rectilinear response from 1 µM to 0.1 M I at pH 1.8 to 6.2 with a slope of 28 to 30 mV per decade. The limit of determination was 5 µg mL-1, and accuracy and precision were good. The all-solid-state electrode was also assessed in a flow injection cell.
Chloroquine Pharmaceutical Electrode Electrode Potentiometry

"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

"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

"Novel Approach To Non-segmented Flow Analysis. 4. Aluminum In River Waters"
J. Autom. Methods Manag. Chem. 1991 Volume 13, Issue 4 Pages 147-151
D. J. MALCOLME-LAWES and K. H. WONG

Abstract: Aluminum was determined in natural water with use of a flow analyzer. as described by Malcolme-Lawes and Pasquini (ibid., 1988, 10, 192) and a combined reagent system of Chrome azurol S (C. I. Mordant Blue 29) - hexadecylpyridinium chloride - ethanol at pH 5.0. The detection limit was 18 ppb of Al(III); the coefficient of variation was 1.8%. The effect of interfering ions was discussed.
Aluminum River

"Flow Injection Chemiluminescent Determination Of Glycerol-3-phosphate And Glycerophosphorylcholine Using Immobilized Enzymes"
J. Biolumin. Chemilumin. 1997 Volume 12, Issue 1 Pages 1-5
M. Yaqoob, A. Nabi, M. Masoom-Yasinzai

Abstract: To determine glycerol-3-phosphate (I, glycerol 1-phosphate), sample (30 µL) was injected into a stream (0.7 ml/min) of 0.1 M succinate buffer of pH 6 and passed through a column (3 cm x 2.5 mm i.d.) at 30°C containing glycerol-3-phosphate oxidase immobilized on controlled pore glass. The eluate merged with a stream (0.7 ml/min) of 0.1 M carbonate buffer of pH 10.5 containing 10 µM-luminol and 10 µM-Co(II), and after travelling 2.2 cm the flow passed through a glass coil (10 cm x 1 mm i.d.) in front of a photomultiplier tube where the chemiluminescence was measured. To determine glycerophosphorylcholine (II; α-glycerophosphorylcholine) offline conversion to I using phospholipase-D was carried out in 0.1 M succinate buffer of pH 6 at 30°C for 10 min. The detection limits were 0.5 µM-I and 1 µM-II and the RSD were M and 20-100 µM, respectively. Sample throughput was 40/h. Flow injection procedures with immobilized enzyme mini-columns are described for the determination of glycerol-3-phosphate, and glycerophosphorylcholine with chemiluminescent detection. The hydrogen peroxide produced on-line is coupled with a luminol (5-amino-2,3,-dihydro-1,4-phthalazinedione) peroxidation chemiluminescent system. The detection limits for glycerol-3-phosphate and glycerophosphorylcholine are 5 x 10^-7 M and 1 x 10^-6 M respectively with RSD < 2%. The sample throughput is 40/h. The immobilized enzyme columns did not show any deterioration in activity after usage for 3 months.
3-Phosphoglyceric acid glycerophosphorylcholine Chemiluminescence

"Dissolved Oxygen Determination By Electrocatalysed Chemiluminescence With Inline Solid Phase Media"
J. Biolumin. Chemilumin. 1998 Volume 13, Issue 3 Pages 125-130
James E. Atwater*, Jeffrey DeHart, Richard R. Wheeler Jr

Abstract: Dissolved elemental oxygen is determined in a flowing aqueous stream using glucose oxidase to catalyse the reaction between D-glucose and O-2 to produce hydrogen peroxide. The revels of the resulting H2O2 are detected and quantified by luminol chemiluminescence using inline solid phase media for pH adjustment of the reagent stream and for controlled release of the luminophore. The reaction is initiated by electrochemical catalysis. By the use of excess D-glucose in the reagent flow stream, the intensity of chemiluminescence is rendered proportional only to fluctuations in the dissolved O-2 concentration. The methodology provides a means for the detection of aqueous O-2 in the range 0-10 mg/L.
Oxygen Chemiluminescence

"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

"Online Determination Of Glucose Concentration Throughout Animal Cell Cultures Based On Chemiluminescent Detection Of Hydrogen Peroxide Coupled With Flow Injection Analysis"
J. Biotechnol. 1991 Volume 18, Issue 1-2 Pages 161-172
Y. L. Huang*, S. Y. Li, B. A. A. Dremel, U. Bilitewski and R. D. Schmid

Abstract: A flow injection analysis (FIA) system for the online determination of glucose in animal cell cultures is described. The system is based on immobilized glucose oxidase (GOD). The hydrogen peroxide generated in the enzyme reaction is determined via a highly sensitive chemiluminescent reaction with luminol. Based on the measurement of the maximum emitted light intensity, the system was able to analyze hydrogen peroxide over the concentration range of 10^-7 to 10^-2 M. For glucose determination, the system has a linear range of 10^-5 to 5 x 10^-2 M glucose, with an RSD of 3% at the 1 mM level (5 measurements). The influence of luminol and buffer concentrations, pH and temperature on the chemiluminescent reaction were investigated. The enzyme reactor used was stable for more than 4 weeks in continuous operation, and it was possible to analyze up to 20 samples per h. The system has been successfully applied to online monitoring of glucose concentration during an animal cell culture, designed for the production of human antithrombin III factor. Results obtained with the FIA system were compared with off-line results, obtained with a Yellow Springs Instrument Company Model 27 (YSI).
Glucose Fermentation broth Chemiluminescence

"Comparative Study Of Different Methods For Sulfide Determination When Adopted To Flow System"
J. Chem. Soc. Pak. 1991 Volume 13, Issue 1 Pages 32-38
Yaqoob, M.;Rishi, L.;Masoom, M.

Abstract: Three different flow injection spectrophotometric methods for S2- determination were compared and the effects of reagent concentration, flow rate, pH, mixing coil length and interfering species were studied. Organic Hg compounds formed complexes with thiourea, alkylxanthates and thiols in the presence of sodium nitroprusside and the absorbance was measured at 545 nm. The reaction between cacotheline and S2- in acetate buffer solution was monitored by measuring the absorbance at 510 nm. A mini-column containing an ion-exchange resin in the SCN- form was used to produce a red Fe(III) complex, and the absorbance was measured at 455 nm. Detection limits of 80, 1.0 and 0.5 ppm with sampling rates of 120, 30 and 44 h-1 and coefficient of variation 0.96, 1.8 and 0.4% were obtained for the three methods, respectively. The first two methods were selective, sensitive and free from common interfering ions, but the third method was subject to serious interference.
Sulfide Ion exchange Spectrophotometry

"Spectrophotometric Flow Injection Determination Of Nitrate And Nitrite In Potable Water Using 8-hydroxyquinoline"
J. Chem. Soc. Pak. 1991 Volume 13, Issue 4 Pages 248-252
Yaqoob, M.;Siddiqui, M.A.;Masoom, M.

Abstract: A method based on flow injection analysis is described for the determination of NO3- and NO2-. A mini-column of copperized Ca was used to reduce NO3- to NO2- which was in turn diazotized with 4-aminobenzoic acid and 8-hydroxyquinoline before determination at 485 nm. Sample throughput was 60 h-1. The coefficient of variation was 0.8% for NO3- and 1.0% for NO2-. Sample (25 µL) was injected into a stream of 10 mM Tris buffer of pH 7 (0.5 mL min-1). For NO2- only, the stream was mixed with 25 mM 4-aminobenzoic acid of pH 2, then with 3 mM quinolin-8-ol of pH 12, both pumped at 0.5 mL min-1. After passage through a 60-cm coil the absorbance was measured at 485 nm. For NO2- plus NO3-, the buffer stream was passed through a reduction column (4 cm x 2 mm) packed with copperized cadmium (prep. described) before mixing with the reagents. Calibration graphs were rectilinear for 1 to 9 ppm of NO3- and 0.5 to 4.5 ppm of NO2-, with detection limits of 0.3 and 0.1 ppm, respectively. The sampling rate was 60 h-1. In the above ranges, the mean coefficient of variation were 0.8% for NO3- and 1% for NO2-. The results from a sample of city water agreed with those obtained by the 4-hydroxybenzene-1,3-disulfonic acid method for NO3- and the 4-aminosalicylic acid method for NO2-.
Nitrate Nitrite Water Spectrophotometry

"Fluorescence Derivatization Approaches For Quantitative High Performance Liquid Chromatography Of Peptides"
J. Controlled Release 1990 Volume 13, Issue 2 Pages 121-128
Gerald R. Rhodes*, Venkata K. Boppana and Marc J. Rubenfield

Abstract: Peptides were isolated from plasma by solid-phase extraction before analysis. For determination of disulfide-containing peptides, the sample was treated with 100 mM borate buffer (pH 8) containing 10 mM dithiothreitol at 50°C for 30 min, followed by 40 mM ammonium 4-chloro-7-sulfobenzofurazan at 60°C for 2 h. After solid-phase extraction, the sample was subjected to HPLC on a 2-mm i.d. column with gradient elution (described) and fluorescence detection at 470 nm (excitation at 380 nm). For determination of arginine-containing peptides, the sample was subjected to HPLC, at 60°C, with gradient elution (described), followed by post-column derivatization with 0.4 M NaOH and 0.05% ninhydrin at 70°C and fluorescence detection at 470 nm (excitation at 390 nm). The method was applied in the analysis of disulfide- and arginine-containing drugs; the calibration graphs were rectilinear for 0.46 to 185 pmol mL-1 of SKF 101926 and for 0.5 to 100 pmol mL-1 of SKF 105494.
Drugs Peptides Blood Plasma 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

"Determination Of Neutral Fat In Milk By Amperometric Flow Injection Analysis With Immobilized Enzyme Reaction"
J. Flow Injection Anal. 1991 Volume 8, Issue 2 Pages 136-147
Seiichi Higuchi, Kiyoshi Matsumoto and Yutaka Osajima

Abstract: The method is based on hydrolyis of neutral fat by triacylglycerol lipase (I) - carboxylesterase (II) and glycerol dehydrogenase (III)-catalyzed oxidation of glycerol, after which the NADH produced is monitored amperometrically. The cited sensor is made from I and II co-immobilized on aminopropyl-substituted controlled-pore glass and from III immobilized on Amino-Cellulofine. For application, an emulsion of milk in 6% bovine serum albumin solution is diluted with buffer solution prepared from 0.125 M carbonate buffer of pH 9.5 containing 30 mM (NH4)2SO4 and 1% of Triton X-100, and a portion is injected into the analyzer. (diagram given) for the determination of neutral fat at 25°C with the above-mentioned buffer as carrier stream at 1 mL min-1. When determining triolein, the relationship between response and concentration. is rectilinear for 0.0128 to 0.0853%; the coefficient of variation was 0.87%. Results were comparable with those obtained by the Wako triglyceride G-test method.
Triolein Fatty acids Milk Amperometry

"Simultaneous Determination Of Cyanide And Sulfide By Reversed Flow Injection Analysis"
J. Flow Injection Anal. 1994 Volume 11, Issue 1 Pages 58-67
Huiliang, M.;Jingfu, L.;Jianzhang, F.;Yue, G.

Abstract: A diagram of the optimized manifold is given. Sample was mixed with a stream of EDTA/HCl solution (0.4 ml/min) to form the donor stream which was heated to 60°C whilst passing through a PTFE coil (1 m x 0.7 mm i.d.) in the thermostat. Liberated HCN diffused through the PTFE membrane and was adsorbed by 5 mM NaOH acceptor solution the acceptor solution was then mixed with chloroamine-T/phosphate buffer solution Pyridine-barbiturate reagent was injected and the absorbance was measured at 494 nm for the separated cyanide (I). Alternatively, the donor stream was adjusted to pH 4.7 by mixing with a sodium acetate solution and then with an Fe(III) (1,10-phenanthroline chromogenic reagent. The absorbance was measured at 505 nm for sulfide (II). The detection limits of I and II were 0.2 and 0.4 mg/;, respectively. The corresponding RSD (n = 11) were 0.5 and 0.7% at 3 and 10 mg/l, respectively. Carbonate, nitrate, formaldehyde, iodide, thiocyanate and bromide did not interfere.
Cyanide Sulfides Environmental Spectrophotometry

"Determination Of Free Amino-acids In Cheese By Flow Injection Analysis With An Enzymatic Reactor And Chemiluminescence Detector"
J. Food Sci. 1990 Volume 55, Issue 6 Pages 1555-1558
Puchades, R.;Lemieux, L.;Simard, R.E.

Abstract: L-Amino-acid oxidase solution (3 ml) was added to 0.3 mg of glutaraldehyde-treated glass beads at 4°C and the mixture was set aside for 2.5 h. After washing with water and phosphate buffer solution the beads were packed into a glass column (7.5 cm x 1.7 mm). Freeze-dried extracts of cheese (~30 mg) were sonicated with 0.1 M phosphate buffer solution (pH 7.5) and filtered through a 0.45 µm membrane and a Sep-Pak C18 cartridge before being passed through the immobilized enzyme with 0.1 M phosphate buffer solution (pH 7.5) - 1 mM EDTA as carrier (1 mL min-1). The generated H2O2 was mixed with 1.5 mM luminol solution in 0.1 M Na2CO3 buffer solution (pH 10.5) and 8 mM aqueous K3Fe(CN)6 at 1.5 mL min-1 and the chemiluminescence was detected by a photomultiplier. The log. - log. calibration graphs for L-leucine (I) were rectilinear from 0.025 to 1.0 mM; coefficient of variation (n = 10) were 1.4 and 0.3% for 0.1 and 0.8 mM of I, respectively.
Amino acids, free Food Chemiluminescence

"Stopped-flow Kinetic Investigation Of The Oxidation Of Ascorbic Acid By Iron (III) Benzohydroxamic Acid"
J. Inorg. Biochem. 1996 Volume 61, Issue 3 Pages 155-163
S. Lakshmi, D. Saravanan, R. Renganathan* and M. Velusamy

Abstract: The fast oxidation of ascorbic acid by Fe(III)benzohydroxamic acid complex [Fe(BHA)3] has been investigated by the stopped-flow technique in aqueous ethanol medium at three pH values (4.6, 7.0, and 9.0). The reaction exhibits a first-order dependence of rate each on [ascorbic acid] and [Fe(BHA)3], obeying Michaelis-Menton kinetics. The rate of the reaction was found to be pH-dependent.
Ascorbic acid Spectrophotometry

"Ultramicro Analysis Of Reducing And Non-reducing Sugars By Liquid Chromatography"
J. Liq. Chromatogr. Relat. Technol. 1991 Volume 14, Issue 10 Pages 1929-1938
T. Kinoshita; Y. Kamitani; J. Yoshida; T. Urano; N. Nimura; T. Hanai

Abstract: A sugar mixture was separated by HPLC in (i) a stainless-steel column (25 cm x 4.6 mm) of Hitachi 3013N anion-exchange resin (5 µm) with a gradient mobile phase (1.0 mL min-1) of 0 (held 13 min) to 0.1% Na acetate in 7 min in 0.1 M NaOH at 40°C or (ii) a column (25 cm x 4.6 mm) of Asahipak NH2 P-50 [polyamine-bonded poly(vinyl alcohol)] with a mobile phase (1.0 mL min-1) of aqueous 75% acetonitrile at 30°C. Post-column reaction was in a stainless-steel coil (10 m x 0.5 mm) with 20 mM taurocyamine with (for non-reducing sugars) or without (for reducing sugars) 1 mM NaIO4 in 0.2 M K2B4O7 at pH 11.5 in system (i) followed by a cooling coil (1.5 m x 0.5 mm); in system (ii) the pH was 10.5 and NaIO4 was not used. Fluorimetry was at 420 nm (excitation at 325 nm). The lower detection limit for reducing sugars was 10 pmol; relative sensitivities are tabulated for 26 sugars vs. glucose.
Sugars, nonreducing Sugars, reducing HPLC Fluorescence

"Chemical Sensors For Water Quality Analysis"
Kogyo Yosui 1991 Volume 395, Issue 1 Pages 80-89
Asano, Y.;Itoh, S.

Abstract: A review is presented, with 12 references, with discussion of pH, redox and ion electrodes, BOD sensors and flow injection analysis using chemical sensors.
Water Electrode Sensor

"Flow-through Atomic Absorption Determination Of Metals After Enrichment"
Magy. Kem. Foly. 1992 Volume 98, Issue 8 Pages 323-329
Graf Harsanyi, E.;Feher, Z.

Abstract: Mini-columns (3 cm x 2.5 mm) packed with 40 mg of silica gel (30 to 50 µm; pore diameter 10 nm) containing quinolin-8-ol were used for off-line enrichment of Pb, Cd and Cu in aqueous solution at pH 4 to 6. A 100-fold concentration. of Pb was possible in 20 min with 5% HNO3 as eluent (3.8 mL min-1) . The flow injection apparatus described gave rectilinear calibration graphs from for 0.01 to 0.1 µg mL-1 of Pb and 0.005 to 0.05 µg mL-1 of Cd and Cu; the coefficient of variation was 5.1%.
Lead Cadmium Copper Spectrophotometry

"Direct Determination Of Urinary Oxalate By A Continuous-flow Method"
Med. Lab. Sci. 1990 Volume 47, Issue 2 Pages 73-79
Goldsack K, Ginman RF, Wright JM

Abstract: The sample, in water as carrier, is mixed with succinate buffer of pH 5.6 and passed through a reactor containing ascorbate oxidase (to oxidize ascorbate, which otherwise interferes) immobilized (method described) on the inner surface of O-alkylated nylon tubing. The stream is then mixed with succinate buffer of pH 2.0 before passage through a reactor containing immobilized oxalate oxidase, and 3,5-dichloro-2-hydroxybenzenesulfonic acid - peroxidase reagent is added to react with the H2O2 thus formed. The absorbance of the product is measured at 510 nm. Response is rectilinear for up to 0.5 mM oxalate. The method shows good selectivity. At 0.3 mM oxalate, the within- and between-batch coefficient of variation were 1.4 and 1.7%, respectively (n = 10). Recovery of added oxalate was >91%. Results were well correlated with those of an enzymatic 3-methylbenzothiazolin-2-one hydrazone method.
Oxalate Urine Spectrophotometry

"Determination Of Hydrogen Peroxide In Rain-water By Flow Injection Analysis With Titanium(IV) - 4-(2-pyridylazo)resorcinol Reagent"
Nippon Kagaku Kaishi 1991 Volume 1991, Issue 5 Pages 430-432
Matsubara, C.;Sakai, K.;Takamura, K.

Abstract: A 100 µL sample is flow-injected into a carrier stream of water to the pre-column filled with Amberlite IR-120B before mixing with 0.24 mM Ti - 4-(2-pyridylazo)resorcinol (I) reagent (pH 2.1) and with 0.1 M ammonium buffer of pH 10.7; both mixing coils (130 cm x 0.5 mm) were heated in a thermostat bath at 60°C (all flow-rates were 0.2 mL min-1). Spectrophotometric detection of Ti(IV) - I - H2O2 was by measurement at 508 nm (ε = 36,000). By standard-additions method, recovery was 95.9 to 101.4% and coefficient of variation was 0.8%. Determination range was 1.36 (detection limit) to 1360 ppb of H2O2.
Hydrogen peroxide Rain Spectrophotometry

"Quantification Of Imipenem's Primary Metabolite In Plasma By Post-column Chemical Rearrangement And UV Detection"
Pharm. Res. 1991 Volume 8, Issue 1 Pages 33-39
Donald G. Musson, Richard Hajdu, William F. Bayne and John D. Rogers

Abstract: Pre-treated samples (prep. described) were subjected to HPLC on a column (10 cm x 8 mm) of Resolve C18 Radial-PAK equipped with a column of RCSS Guard PAK C18 with a mobile phase of tetrabutylammonium hydrogen sulfate - H3PO4 - water, adjusted to pH 6.85 with 1 M KOH. The eluate was diluted with 0.426 M H3PO4 (0.6 mL min-1, passed through a column (25 cm x 4.6 mm) packed with 40 µm glass beads and the absorbance was measured at 295 and 320 nm. Calibration graphs were rectilinear for 1 to 100 µg mL-1 of the cited metabolite (I) in plasma and dialysate and for 5 to 100 µg mL-1 in urine . Coefficients of variation were 10%.
Imipenem, N-Formimidoyl thienamycin Blood Plasma Urine HPLC Spectrophotometry

"FIA Spectrophotometric Assay Of N-acetylcysteine By O-phthalaldehyde Derivatization"
Pharmazie 1990 Volume 45, Issue 10 Pages 745-747
Medina Hernandez, M.J.;Garcia Alvarez Coque, M.C.;Bonet Domingo, E.;Villanueva Camanas, R.M.

Abstract: A flow injection spectrophotometric procedure is proposed for the determination of N-acetylcysteine (NAC). The procedure is based on the rapid reaction of the thiol group with o-phthalaldehyde and isoleucine at pH 9.5 to give an 1-alkylthio-2-alkyl-substituted isoindole which shows maximum absorbance at 335 nm. The linear dynamic range is 16-160 µg/ml, with a 0.6% relative standard deviation for 100 µg/ml. The sampling rate is 126 samples/h. The method is applied successfully to the evaluation of NAC in commercial formulations. Portions (120 µL) of standard N-acetylcysteine (I) or aqueous dilution of I formulations were injected into a flowing stream of a mixture of borate buffer (pH 9.5) - ethanolic 50 mM 2-phthalaldehyde (4:1) and mixed in a 2.2 m coil; 10 mM isoleucine in 1 M HCl was introduced at a T-junction and further mixed in an 80-cm coil. The absorbances were measured at 335 nm. The calibration graph was rectilinear for 16 to 160 µg mL-1. The coefficient of variation for a 100 µg mL-1 of I was 0.6%. Results for four formulations agreed within 7% of the labelled values and also agreed with the results by batchwise analysis with the same method, iodimetric titration and oxidation with Fe(III) in the presence of 1,10-phenanthroline.
N-acetylcysteine Pharmaceutical Spectrophotometry

"Studies In Flow Injection Analysis"
Proc. Anal. Div. Chem. Soc. 1979 Volume 16, Issue 1 Pages 4-7
B. Fields, L. Dajer de Torrijos, E. J. Greenhow, Aileen M. Prescott, Michael Cooke, Samuel J. Lyle, Saber Tehrani, P. J. Barlow, D. R. Crump, A. K. Khera, D. G. Wibberley, D. S. Macintyre, B. G. Cooksey, J. M. Ottaway, J. F. Alder, R. M. Bombelka and G. F

Abstract: The application of flow injection analysis to the simultaneous spectrophotometric determination of two metals in a sample is described and a novel phototransducer which improved peak detection is discussed. Thus, an aqueous HCl sample containing Pb(II) and V(V) at pH 2 was injected into a stream 10^-3 M in 4-(2-pyridylazo)resorcinol (I) buffered in NH3 at pH 9.9. The changes with time in the peaks owing to the V-I complex, formed at pH 2, and the Pb-I complex, formed at pH 9, were observed Pb was determined with 1-2% relative standard deviation in the presence of varying amounts of V but V could be determined with only limited precision in the presence of a constant amt. of Pb. The use of refractometry to measure peaks in flow injection analysis was also discussed with reference to some examples with aqueous NaCl. With the phototransducer, 100 ppb Co(II) could be detected with a relative standard deviation of ~1%.
Lead(2+) Vanadium(V) Cobalt(II) Refractometry Spectrophotometry

"Diode-array Detectors In Flow Injection Analysis. Simultaneous Determination Of Thorium(IV) And Lanthanum(III) With Arsenazo(III) By Multivariate Calibration"
Quim. Anal. 1989 Volume 8, Issue 2 Pages 223-230
Blanco, M.;Coello, J.;Gene, J.;Iturriaga, H.;Maspoch, S.

Abstract: The zero-, first- and second-order derivative spectra were obtained of synthetic mixtures of La(III) and Th(IV) with 3 mM arsenazo III in 1 M acetate buffer (pH 4) over the range 620 to 720 nm. Multivariate calibration was used for resolution of the spectra of the individual metals. Use of the second-derivative spectra gave the best accuracy. The method can be applied over the ranges of 0.5 to 2.5 µg mL-1 of La(III) and 2.8 to 7.0 µg mL-1 of Th(IV). The throughput was 60 samples h-1.
Lanthanum(3+) Thorium(IV) Spectrophotometry Spectroscopy Spectroscopy

"Flow Injection Analysis Methods For The Determination Of Acetylcysteine"
Quim. Anal. 1990 Volume 9, Issue 2 Pages 205-213
Vinas, P.;Sanchez Prieto, J.A.;Hernandez Cordoba, M.

Abstract: A complex is formed between acetylcysteine (I) and Ni(II) and injected into a flow injection apparatus. The content of I may then be determined either by measurement of the peak height at 415 nm or by a peak - width method using a gradient tube, which extends the working range. Pharmaceutical products are first dissolved in water and brought to pH 2.6 with 1 M HCl.
N-acetylcysteine Pharmaceutical Spectrophotometry

"Response Characteristics Of Tubular Flow-through Potentiometric Sensors Selective To Ions With Acid - Base Properties"
Quim. Anal. 1991 Volume 10, Issue 4 Pages 355-365
Alonso, J.;Bartoli, J.;Lima, J.L.F.C.;Garcia Raurich, J.

Abstract: The influence of sample pH on the response of tubular electrodes, selective to species with acid - base properties and used as detectors in flow injection systems, was evaluated under different experimental conditions. Low-dispersion flow injection systems gave adequate conditioning of samples with extreme pH values. The flow system proposed allows the determination of the analyte at concentration. near to the lower limit of the linear response.
Potentiometry Electrode Electrode Sensor

"Immobilized Resins And Liquid Extractants For Potassium Extraction From Concentrated Brines"
React. Polym. 1991 Volume 14, Issue 1 Pages 81-84
S. Belfer and S. Binman, Y. Lati and S. Zolotov

Abstract: Potassium ions in concentrated chloride solution of alkali and alkaline-earth cations were extracted by solid - liquid or liquid - liquid extraction. For liquid - liquid extraction the organic phase consisted of a 10% solution of crown ether, Cyanex 301 [bis(2,4,4-trimethylpentyl)dithiophosphinic acid] or an equimolar mixture of the two, in toluene. The aqueous phase consisted of 0.2 M KCl, 2 M NaCl, 1.85 M MgCl2 and 0.5 M CaCl2. Equal volume (10 ml) of the organic and aqueous phases were equilibrated overnight and aliquots of both phases were withdrawn for anlaysis. The metal concentration. was measured by stripping the organic phase with 0.1N-HNO3. At pH 2 to 4 the main component in the organic phase is K; extraction was signifcantly improved by using the crown ether - Cyanex mixture. Solid - liquid extraction was carried out with use of a column of polystyrene resin impregnated with crown ether - Cyanex 301 (1:1). A mixture of 0.01 M NaCl and 0.01 M KCl (pH 10) was passed through the column (0.2 mL min-1) and elution was carried out with 0.1N-HNO3. Highly selective separation of K from Na was achieved in 0.01 M solution but the method is not suitable for concentrated brines due to the low capacity of the column.
Potassium Environmental Sample preparation

"Automatic Precipitation In Flow Injection Analysis With Online Dialysis - Indirect Determination Of Sulfate By Measurement Of The Unprecipitated, Excess Barium In The Dialysate Stream Of The Flow System"
South Afr. J. Chem. 1990 Volume 43, Issue 3-4 Pages 78-82
van Staden, J.F.; van Rensburg, A

Abstract: The method is based on a combination of the formation of a continuous solid - liquid interface (precipitation) and a continuous liquid - liquid interface (dialysis). Sulfate from a 30 µL sample is precipitated turbidimetrically with an excess of BaCl2 to form a suspended ppt. of BaSO4. Excess Ba2+ is transported with the carrier stream to the donor channel of the dialyser where it dialyses to the detector channel. The dialysate of Ba reacts with methylthymol blue to form a complex which is measured spectrophotometrically at 608 nm. The pH was kept relatively high with NaOH. The proposed flow injection procedure is suitable for the indirect determination of SO42- at a sampling rate of 60 samples h-1 with a coefficient of variation of 1.4%. The calibration graph was rectilinear in the range 100 to 1000 mg L-1 and the recovery was 98.8 to 100.5%.
Sulfate Turbidimetry

"Flow Injection Analysis Using Ion-sensitive Field Effect Transistors. A Model System For Discrete Assays And Continuous In Vitro Monitoring Of PH And PCa"
Scand. J. Clin. Lab. Invest. 1982 Volume 161, Issue 1 Pages 35-41
Ruzicka, J.;Ramsing, A.

Abstract: A miniaturized flow injection system yields an instant readout and requires microlitre volumes of sample and reagent solutions. Using electrode measurement as an example it is shown that the difference between discrete assays and continuous monitoring becomes so small that the same apparatus will eventually perform both functions.
Calcium pH Clinical analysis Field effect transistor Electrode

"Determination Of Amino-acids In The Rice Residue From A Gourmet Powder Factory By High Performance Liquid Chromatography"
Sepu 1991 Volume 9, Issue 3 Pages 207-208
Lin Quan

Abstract: Sample was dissolved in 6 M HCl,hydrolyzedat 110°C for 24 h and the pH was adjusted to 2.2. The amino-acids in the solution were analyzed by HPLC on a column (15 cm x 4 mm) of Shim-pack ISC-07/S1504 Li, operated at 38°C to 58°C with gradient elution (0.4 mL min-1) with Li citrate - 1,2-dimethoxyethane - HClO4 - H3BO3 - LiOH - water (details given) and post-column derivatization with reagent B (o-phthalaldehyde - ethanol - mercaptoethanol - Brij-35) in reagent A (NaOCl in Na2CO3 - H3BO3 - K2SO4 - water buffer of pH 10) at 55°C with detection at 450 nm (excitation at 350 nm). The coefficient of variation were 4.2%; the detection limit was 1 nM.
Amino Acids Rice HPLC

"Determination Of Glucose By An Enzyme Electrode Flow Injection Analysis System (EFIA)"
Zhongguo Shengwu Huaxue yu Fenzi Shengwu Xuebao 1990 Volume 6, Issue 4 Pages 294-300
Zhang, Xian-en; Zhang, Xing; Xia, Xiang-ming; Zhang, Ying-kuei; Hu, Guo-shou

Abstract: An EFIA system was developed for the determination of glucose in blood focusing on factors affecting the sensor response. Optimum pH was 5.8 to 6.5. Sodium citrate (3.5%) and saline (0.85%) enhanced response slightly. The linear range of the sensor was dependent on injection volume Recoveries were 96%. Results compared well with an o-toluidine method and an automatic analyzer..
Glucose Blood Electrode

"Continuous-flow Analysis. Determination Of Osmium Using A Catalytic Reaction Of P-phenylenediamine With Hydrogen Peroxide"
Vestn. Mosk. Univ. Khim. 1992 Volume 33, Issue 5 Pages 472-475
Rodionova, T.V.;Beklemishev, M.K.;Chigvintseva, E.V.;Zolotov, Y.A.

Abstract: An automatic continuous-flow system with flow segment is used for the determination of Os, based on its catalytic effect on the reaction of p-phenylenediamine and hydrogen peroxide. The reaction is performed in pH 7.0 solution The concentrations. of p-phenylenediamine and hydrogen peroxide should be higher than 5.0 x 10^-3 and 1M, respectively. The detection limit is 1 x 10^-5 µg/mL. The relative standard deviation is 0.06 at the low determination concentration. range. The productivity is 48 samples per h.
Osmium

"Rapid Determination Of Trace Cadmium In Waste Water By FIA - Fluorimetry"
Yankuang Ceshi 1991 Volume 10, Issue 3 Pages 200-202
Guo, J.;Zhao, H.;Duan, X.

Abstract: Industrial waste water adjusted to pH 7 by addition of ammonia, water and acetic acid flowed to react with a stream of 0.7 mM 8-hydroxyquinoline-5-sulfonic acid, 0.65 mM hexadecyltrimethylammonium bromide and ammonium acetate buffer of pH 7.18 in a 29.2-m reaction tube before measuring fluorescence intensity at 534 nm (excitation at 391.7 nm) in a 9.8-cm quantitation tube. Linear range was from 0 to 5 µg mL-1 of Cd. Recovery was 95.2 to 98.7%; coefficient of variation was 0.1%. The rate was up to 180 per h. Only Al3+, Fe3+, Hg2+, Zn2+, Cl-, F- and ClO4- interfered. Results were satisfactory and comparable with those of ICP-AES.
Cadmium Waste Fluorescence

"Study On The Systematic Analysis Of Squeezed Water From Soil By Flow Injection Analysis"
Yankuang Ceshi 1991 Volume 10, Issue 3 Pages 166-170
Lin, S.L.;Shuai, Q.;Qiu, H.O.

Abstract: Sample (2 to 5 ml) was systematically analyzed in the sequence of (i) conductivity, (ii) pH value, (iii) HCO3- by flow injection analysis (FIA) - gas diffusion method, (iv) K+, Na+, Ca2+ and Mg2+ by FIA - AAS, (v) Cl- by FIA - photometry and (vi) SO42- by FIA - turbidimetry. All required procedures were described (details illustrated) for the complete scheme and for the three FIA systems. These methods were time saving and highly reproducible. Results agreed well with calculated values of synthetic samples.
Water Water Conductometry Spectrophotometry Turbidimetry

"Construction And Application Of Atropine Flow-through Sensor In Flow Injection Analysis"
Yaoxue Xuebao 1990 Volume 25, Issue 6 Pages 451-456
Liu WZ, Wu PZ, Yan Z, Yang CH, Li AJ, Xu RZ

Abstract: A new kind of flow-through sensor for atropine has been studied. It exhibits Nernstian response for atropine with a slope of 54±1 mV/decade over the concentration range of 0.02-200 mmol/L at pH 5-8. The sensitivity coefficients of common compounds were determined. Only bromo-geramine, clonidine, strychnine and amantadine showed remarkable interference. Direct potentiometry for determination of atropine showed an average recovery of 99.2% and a relative standard deviation of 1.3%. It has been used in flow injection analysis (FIA) of atropine, anisodamine and scopolamine and belladonna preparations. Rate of analysis of as high as 60-100 samples/h was achieved.
Atropine Anisodamine Scopolamine Belladonna Potentiometry Sensor

"Berberine-electrochemical Detector For The Determination Of Berberine-type Alkaloids In Various Chinese Patent Medicines By Flow Injection Analysis"
Yaoxue Xuebao 1991 Volume 26, Issue 4 Pages 315-319
Liu WZ, Peng WB, Yang CH

Abstract: A description is given for the preparation of flow-through sensor and of the incorporation of the sensor into a flow injection analysis system. The parameters affecting the measurement are discussed. An accurate, convenient and rapid method is proposed for the determination of berberine-type alkaloids in various Chinese patent medicines (Coptis chinensis Franch., Phellodendron chinesis Schneid., xianglian wan, zuojin wan, ermiao wan and sanmiao wan). The slope is 54-60 mV/decade over the concentration range of 10^-3-3 x 10^-6 mol/L berberine at pH 2-9.5. Direct potentiometry determination of berberine in various samples showed an average recovery of 99.5-103.5% and a relative standard deviation of 1.3-3.5% at a sampling rate of 120/h. A flow-through sensor and its incorporation into a flow injection analysis system is described and a rapid convenient method for the determination of berberine-type alkaloids in Chinese traditional medicines is proposed. The slope was 54 to 60 mV per decade in the range 1 µM- to 3 mM berberine at pH 2 to 9.5. Recoveries were 99.5 to 103.5%, coefficient of variation were 1.3 to 3.5% and the sampling rate was 120 h-1.
Alkaloids Pharmaceutical Electrochemical analysis Potentiometry

"Determination Of Tetracyclines By Flow Injection Analysis"
Yaoxue Xuebao 1991 Volume 26, Issue 5 Pages 391-394
Liu WZ, Jiang H, Du AZ

Abstract: An accurate, convenient and fast method was proposed for the determination of tetracyclines (tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline) and their preparations by flow injection detector based on tetracycline flow-through sensor. The parameters affecting the measurement were discussed. The detector can respond to tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline, at the same time. Their slopes are 51-55 mV/decade over the concentration range of 10^-2-5 x 10^-5 mol/L at pH 1.5-3.5. The results obtained are in good agreement with those by biological assay (less than 3% deviation). One hundred samples can be determined in an hour. Tetracycline (I), chlortetracycline (II), oxytetracycline (III), doxycycline (IV) and methacycline (V) in pure form or in their preparations were determined by flow injection analysis with potentiometric detection. The flow injection analysis system and flow-though tetracycline sensor are described (diagram given). At pH 1.5 to 3.5, the relationship between response potential and concentration. was rectilinear up to 10 mM I, -II, -III, -IV and V. One hundred samples could be analyzed in 1 h and results agreed with those by a bioassay.
Tetracycline Potentiometry

"Flow Injection Ion-selective Electrode For Quinine"
Yaowu Fenxi Zazhi 1990 Volume 10, Issue 5 Pages 261-264
Liu, W.Z.;Yan, Z.

Abstract: A description is given of a flow-through sensor for the determination of quinine by flow injection analysis. The sensor exhibits Nernstian response over the range 10 µM to 10 mM quinine at pH 5 to 8; only benzalkonium bromide and diphenhydramine interfere seriously. For an injection volume of 300 µL and use of 0.1 M NaCl as carrier, the average recovery was 100.7% with a coefficient of variation of 1.2%. Results were comparable with those obtained by the method of the Chin. P. The analysis rate is up to 120 h-1.
Quinine Electrode

"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

"Miniature Enzyme-electrode Based On SKN Synthetic Coal For Amperometric Determination Of Glucose"
J. Anal. Chem. 1990 Volume 45, Issue 8 Pages 1580-1585
Levchenko, M.P.;Mikhalovskii, S.V.;Strelko, V.V.;Gorodyskii, A.V.

Abstract: The cited amperometric biosensor determines 20 mM glucose and consists of an enzyme electrode prepared by immobilizing (by adsorption) glucose oxidase on a single granule (~1 mm diameter) of SKN synthetic active coal. This electrode is operated at +0.5 V vs. Ag - AgCl electrode; the oxidation current of H2O2, produced by the enzymatic reaction at optimum pH 8.0 (with phosphate buffer in NaCl) is measured with use of a platinum auxiliary electrode. The response times are ~3 min for batch determinations, and 90 s for flow injection measurements; ~1% of sensor sensitivity is lost each day after measurements. The enzyme-electrode can be stored dry at ambient temperature without loss of activity.
Glucose Amperometry Electrode Electrode Sensor

"Study Of The Voltammetric Behaviour Of Metam And Its Application To An Amperometric Flow System"
Anal. Bioanal. Chem. 2005 Volume 383, Issue 5 Pages 880-885
M. F&aacute;tima Barroso, Paula Pa&iacute;ga, M. Carmo V. F. Vaz, Cristina Delerue-Matos

Abstract: The electrochemical behavior of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a linear response for 17-29 mg L-1. Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at -0.72 V vs AgCl/Ag, dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition -0.20 V for 10 s), calibration curves was measured in the concentration range 2.5 x 10^-1 to 1.0 mg L-1 using SWV. The electrochemical behavior of this compound facilitated the development of a flow injection analysis (FIA) system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection volume of 207 µL and an overall flow rate of 2.4 mL min-1. Real samples were analyzed via calibration curves over the concentration range 1.3 x 10^-2 to 1.3 mg L-1. Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations of one sample (1.0 mg L-1), and the value obtained was 1.5%.
Methylcarbamodithioic acid Environmental Electrode Electrode Electrode Voltammetry Voltammetry Electrochemical analysis Amperometry

"Use Of Multivariate Curve Resolution For Determination Of Chromium In Tanning Samples Using Sequential Injection Analysis"
Anal. Bioanal. Chem. 2005 Volume 382, Issue 2 Pages 328-334
V. G&oacute;mez, M. P. Callao

Abstract: We report a method for determining total chromium in tanning samples using sequential injection analysis (SIA) with a diode-array spectrophotometric detector. With a suitable analytical sequence CrO42- is converted to Cr2O72- inside the tubes of the SIA system, after total oxidation of chromium(III). A data matrix is obtained and analyzed by several chemometric techniques based on multivariate analysis: principal components analysis, simple-to-use interactive self-modelling mixture analysis, and multivariate curve resolution-alternating least-squares. We studied several samples from different stages of a tanning process. Two of these samples were easily oxidized but the others needed more extreme conditions. The analytical sequence prepared, which was based on obtaining a pH gradient and used H2SO4 as reagent, is valid and independent of the level of oxidation needed for the sample. We established a calibration model and evaluated the figures of merit. In some samples we found interferents. With this method the amounts of chromium in each sample were quantified and the results were statistically similar to those obtained by use of the reference method, atomic absorption spectrometry.
Chromium, total Chromium(III) Spectrophotometry

"Catalytically Enhanced Spectrophotometric Determination Of Manganese In Seawater By Flow-injection Analysis With A Commercially Available Resin For On-line Preconcentration"
Limnol. Oceanogr. Meth. 2006 Volume 4, Issue 1 Pages 105-113
Ana M. Aguilar-Islas, Joseph A. Resing, and Kenneth W. Bruland

Abstract: The sensitive, laboratory- and ship-based, flow-injection (FI) method for the determination of dissolved manganese in seawater developed by Resing and Mottl (Anal. Chem. 1992; 64:2682-2687) has been significantly modified and improved by incorporating five significant changes. The three major changes are the use of a commercially available iminodiacetate (IDA) resin (Toyopearl AF-chelate 650M) in place of 8-hydroxyquinoline for on-line pre-concentration of manganese and matrix removal, the addition of nitrilotriacetic acid as an activator ligand which increases sensitivity by a factor of 7 and decreases the limit of detection, and the on-line buffering of acidified samples before column loading. Two minor improvements include use of the more soluble sodium periodate in place of potassium periodate and elimination of Brij-35 surfactant. To accommodate these changes, the pH of samples was adjusted to 8.5 (vs. 7.8), a higher acid concentration was required to elute the Mn from the IDA resin, and stronger reaction buffer was required to neutralize the acid. The accuracy of the method was evaluated with the use of NASS-4 standard seawater and by a comparison study of samples from the California coast that were analyzed by this method and an FI method coupled to inductively coupled plasma sector field mass spectrometry detection. The detection limit and precision of the method depend on the amount of sample pre-concentrated onto the column. By pre-concentrating 1.6 mL of sample, a detection limit of 0.03 nM (3 times the standard deviation of a blank) and precision of 3.2% (as percent relative standard deviation) were obtained. The method was used on board ship to determine dissolved manganese in coastal waters off Oregon and Washington.

"Direct Determination Of Iron In Acidified (pH 1.7) Seawater Samples By Flow Injection Analysis With Catalytic Spectrophotometric Detection: Application And Intercomparison"
Limnol. Oceanogr. Meth. 2006 Volume 4, Issue 6 Pages 164-171
Maeve C. Lohan, Ana M. Aguilar-Islas, Kenneth W. Bruland

Abstract: A sensitive flow injection method for determining iron in seawater developed by Measures et al. (1995) has been substantially modified to allow the direct pre-concentration of dissolved iron in acidified seawater samples (pH 1.7) onto a nitrilotriacetic acid (NTA) chelating resin. This removed the need to adjust the pH and buffer samples prior to the pre-concentration step and the low pH eliminated the potential interference from the presence of strong iron-binding organic ligands. The precision and accuracy of this flow injection method with its pre-concentration step coupled with catalytic spectrophotometric detection with N,N-dimethyl-p-phenylenediamine dihydrochloride (FI-NTA-DPD) was investigated at sea as part of an international intercalibration exercise for the Sampling and Analysis of Fe (SAFe). Acidified seawater samples analyzed using FI-NTA-DPD were shown to be in excellent agreement with other ship and lab-based methods. The acidification of seawater samples to pH 1.7 is an important protocol if total dissolved iron in seawater is to be determined within hours of collection. A ship and lab-based analytical intercomparison of two flow injection methods (FI-NTA-DPD and FI-NTA-ICP-SFMS) for the determination of total dissolved iron in seawater was carried out on SAFe samples collected from both surface waters and at 1000 m depth from the North Pacific Ocean. For the two methods total dissolved iron concentrations in surface samples were 0.101 ± 0.009 and 0.098 ± 0.009 nM, respectively, while those collected at 1000 m were 0.93 ± 0.04 and 0.92 ± 0.08 nM, respectively. No statistical difference (P = 0.05) between the FI-NTA-DPD and FI-NTAICP- SFMS methods was observed.