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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Apparatus

Classification: Manifold component -> Apparatus

Citations 466

"Determination Of Morphine, Oripavine And Pseudomorphine Using Capillary Electrophoresis With Acidic Potassium Permanganate Chemiluminescence Detection"
Analyst 2000 Volume 125, Issue 1 Pages 91-95
Neil W. Barnett, Benjamin J. Hindson and Simon W. Lewis

Abstract: A simple and robust capillary electrophoresis chemiluminescence detection system for the determination of morphine, oripavine and pseudomorphine is described, based upon the reaction of these analytes with acidic potassium permanganate in the presence of sodium polyphosphate. The reagent solution was contained in a quartz detection cell which also held both the capillary and the anode. The resultant chemiluminescence was monitored directly using a photomultiplier tube mounted flush against the base of the detection cell. To ensure that no migration of the permanganate anion occurred, the anode was placed at the detector end whilst the electroosmotic flow was reversed by the addition of hexadimethrine bromide (0.001% m/v) to the electrolyte. The three analytes were separated counter to the electroosmotic flow via their interaction with α-cyclodextrin. The methodology realised detection limits (3 x S/N) of 2.5 x 10^-7 M for both morphine and oripavine and 5 x 10^-7 M for pseudomorphine. The relative standard deviations of the migration times and the peak heights for the three analytes ranged from 0.6 up to 0.8% and from 1.5 up to 2.1%, respectively.

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

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

"Highly-sensitive Flow Injection Determination Of Hydrogen Peroxide With A Peroxidase-immobilized Electrode And Its Application To Clinical Chemistry"
Anal. Chim. Acta 2000 Volume 406, Issue 2 Pages 201-207
Keiko Yamamoto, Takanori Ohgaru, Masaki Torimura, Hideaki Kinoshita, Kenji Kano and Tokuji Ikeda

Abstract: A flow injection system for determination of hydrogen peroxide was constructed using a peroxidase/ferrocene-embedded carbon paste (POD-Fc-CP) electrode covered with a membrane. H2O2 was reduced bioelectrocatalytically at 100 mV (versus Ag/AgCl/sat. KCl). A Nafion(R)-coated cellulose acetate membrane prepared on the surface of water proved to be suitable for the covering membrane. The detection limit (signal :noise = 6) for H2O2 was 200 fmol (10 nM x 20 µl) and the response linearity was retained at least up to 25 µM. The relative standard deviation was 4.4% for 1.0 µM water (n = 7). The flow injection system was successfully applied to the determination of glucose and urate in serum by using the corresponding oxidase-immobilized pre-column. The detection limits were 1.5 pmol for glucose and 2 pmol for urate.
Hydrogen peroxide Glucose Urate Blood Serum Electrode Electrode Amperometry

"Development Of A Highly Sensitive Chemiluminescence Flow Injection Analysis Sensor For Phosphate-ion Detection Using Maltose Phosphorylase"
J. Biotechnol. 1999 Volume 75, Issue 2-3 Pages 127-133
Hideaki Nakamura, Mami Hasegawa, Yoko Nomura, Yoshiko Arikawa, Ritsuko Matsukawa, Kazunori Ikebukuro and Isao Karube

Abstract: A chemiluminescence flow injection analysis biosensor has been constructed for phosphate-ion detection. This system is coenzymeless and employs a maltose phosphorylase, mutarotase, and glucose-oxidase (MP-MUT-GOD) reaction system combined with an Arthromyces ramosus peroxidase-luminol reaction system. The system consists of a column packed with MP-MUT-GOD immobilized on N-hydroxysuccinimide beads, a mixing joint for the chemiluminescence reaction, and a photomultiplier. The response provided by this system was linear, with a wide range between 10 nM and 30 µM phosphate ion, and a measuring time of 3 min per sample. Under the optimal condition, the sensor was able to detect 1.0 µM phosphate ion for at least 2 weeks. For a practical application, the determination of phosphate ion in river water was examined using ethylenediaminetetraacetic acid, and the results were estimated by comparing with the molybdenum-blue method.

"Glucose And Choline On-line Biosensors Based On Electropolymerized Meldolas Blue"
Talanta 2000 Volume 51, Issue 1 Pages 187-195
Lanqun Mao and Katsunobu Yamamoto

Abstract: Electropolymerized film of Meldolas blue (MB) was prepared and demonstrated as electron shuttle between the immobilized horse peroxidase (HRP) and glassy carbon electrode (GCE) for sensing hydrogen peroxide (H2O2) produced by enzyme catalytical reactions. Electrochemical polymerization of Meldolas blue was carried out by cyclic voltammetry (CV) in a phosphate buffer solution (pH 7.00) in a potential window from - 0.60 to + 1.30 V. The pH of the electropolymerization solution was found to be closely related to the resulted polymeric MB and the best polymeric film was obtained in a pH 7.00 phosphate buffer. The polymeric MB was demonstrated to shuttle the electron transfer between the immobilized HRP and GCE and utilized as a mediator for HRP immobilized biosensor for biocatalytical reduction of H2O2 at a potential of - 0.30 V (versus AgCl/Ag). The H2O2 sensing system was applied to construct glucose and choline on-line sensors by wiring H2O2 produced by enzyme oxidase catalytical reaction. The possibility of these sensors as on-line detectors for on-line and continuous measurement was explored off-line. The operating potential, interference, and lifetime of these sensors were also examined.
Glucose Choline Voltammetry Electrode Amperometry Sensor

"Determination Of Salicylate In Blood Serum Using An Amperometric Biosensor Based On Salicylate Hydroxylase Immobilized In A Polypyrrole-glutaraldehyde Matrix"
Talanta 2000 Volume 51, Issue 3 Pages 547-557
Laércio Rover Júnior, Graciliano de Oliveira Neto, João Roberto Fernandes and Lauro Tatsuo Kubota

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

"The Development And Applications Of Thermal Biosensors For Bioprocess Monitoring"
Trends Biotechnol. 1999 Volume 17, Issue 12 Pages 499-505
Kumaran Ramanathan, Morten Rank, Juraj Svitel, Anatoli Dzgoev and Bengt Danielsson

Abstract: Enzyme thermistors are biosensors that use thermal resistors to measure the heat change caused by an enzymatic reaction. They combine the selectivity of enzymes with the sensitivity of biosensors and allow continuous analysis in a flow injection mode. They can be used to monitor fermentation systems, biocatalysis, enzyme-catalyzed synthesis and clinical and food technology. This article gives an overview of the general principles of enzyme thermistors, the sampling process and the ongoing developments in the field of bioprocess monitoring.

"A Disposable Protein A-based Immunosensor For Flow Injection Assay With Electrochemical Detection"
Anal. Chim. Acta 2000 Volume 404, Issue 2 Pages 187-194
Christophe Valat, Benoit Limoges, Denis Huet and Jean-Louis Romette

Abstract: Low-cost disposable immunosensors were produced by covalent binding of Protein A or G on graphite-polystyrene screen-printed electrodes, and they were used in a fully automated flow injection analysis (FIA) system, allowing the kinetics of IgG binding to Protein A or G to be improved by forced convection. The displacement of rabbit IgG bound to Protein A or G by mouse IgG isotypes (IgG(1) or IgG(2a)) was studied. A FIA immunoassay of mouse IgG(2a) was performed at a Protein A-based immunosensor with a good sensibility (down to 0.02 µg ml-1) and a total assay time of 19 min. It was shown that the immunosensor combines the advantages of being reusable for more than 30 assay cycles in flow injection analysis, and disposable when necessary.
Immunoglobulin G, mouse Potentiometry Electrode Electrode Immunoassay Sensor

"A Flow Injection Flow Cytometry System For Online Monitoring Of Bioreactors"
Biotechnol. Bioeng. 1999 Volume 62, Issue 5 Pages 609-617
Rui Zhao, Arvind Natarajan, Friedrich Srienc

Abstract: For direct and online study of the physiological states of cell cultures, a robust flow injection system has been designed and interfaced with flow cytometry (FI-FCM). The core of the flow injection system includes a microchamber designed for sample processing. The design of this microchamber allows not only an accurate online dilution but also online cell fixation, staining, and washing. The flow injection part of the system was tested by monitoring the optical density of a growing E.coli culture online using a spectrophotometer. The en tire growth curve, from lag phase to stationary phase, was obtained with frequent sampling. The performance of the entire FI-FCM system is demonstrated in three applications. The first is the monitoring of green fluorescent protein fluorophore formation kinetics in E.coli by visualizing the fluorescence evolution after protein synthesis is inhibited. The data revealed a subpopulation of cells that do not become fluorescent. In addition, the data show that single-cell fluorescence is distributed over a wide range and that the fluorescent population contains cells that are capable of reaching significantly higher expression levels than that indicated by the population average. The second application is the detailed flow cytometric evaluation of the batch growth dynamics of E.coli expressing Gfp. The collected single-cell data visualize the batch growth phases and it is shown that a state of balanced growth is never reached by the culture. The third application is the determination of distribution of DNA content of a S. cerevisiae population by automatically staining cells using a DNA-specific stain. Reproducibility of the online staining reaction shows that the system is not restricted to measuring the native properties of cells; rather, a wider range of cellular components could be monitored after appropriate sample processing. The system is thus particularly useful because it operates automatically without direct operator supervision for extended time periods.

"Multi-enzymatic Electrochemical Sensor: Field Measurements And Their Optimisation"
Anal. Chim. Acta 1999 Volume 385, Issue 1-3 Pages 461-466
N. F. Starodub, N. I. Kanjuk, A. L. Kukla and Yu. M. Shirshov

Abstract: Using such enzymes as cholinesterases, urease and glucose oxidase, and electrolyte-insulator-semiconductor (EIS)-structures with silicon nitride ion-sensitive layers as transducers investigations have been performed on the determination of heavy metal ions and phosphororganic pesticides in solutions. The content of toxic elements indicated above was determined by estimation of the residual activity of enzymatic membranes after the injection of analyzed samples, The optimal conditions were chosen for analysis of heavy metal ions and phosphororganic pesticides in potato and cabbage saps. It was shown that multienzyme analysis followed by mathematical processing is one of the effective approaches to develop computer-controlled sensor arrays for toxic substrates,
Metals, heavy Pesticides, organophosphorus Vegetable Vegetable Sensor

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

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

"Sensor For Amperometric Determination Of Ammonia And Ammonia-forming Enzyme Reactions"
Anal. Chim. Acta 2000 Volume 403, Issue 1-2 Pages 11-23
B. Strehlitz, B. Gründig and H. Kopinke

Abstract: The amperometric ammonia determination by use of a polyaniline-modified screen printed Pt-C electrode at 0.3 V (versus Ag/AgCl on the strip) is shown. The electrochemical pulse polarization method is used for the modification. The effects of basic electrode material, applied potential, pH of buffer solution and possible interferences of other ions were studied. The polyaniline-modified Pt-C electrode measures (NH4)(2)SO4 with a detection limit of 5 µM, a linear range up to 1 mM and a sensitivity of 40±20 µA cm-2 mM-1. A new generation of enzyme sensors arises from the immobilization of ammonia-forming enzymes in a poly(carbamoyl)sulphonate hydrogel matrix on the working electrode as it is shown for urease to detect urea.
Ammonia Enzyme, urease Amperometry Electrode Electrode Electrode Sensor

"A New Sample-injection/sample-dilution System For The Flow Injection Analytical Technique"
Anal. Chim. Acta 1999 Volume 381, Issue 2-3 Pages 287-295
Milko Novic, Iñaki Berregi, Angel Ríos and Miguel Valcárcel

Abstract: A new sample-injection/sample-dilution system for the flow injection analytical technique is proposed. The system is based on two variable-speed computer-controlled peristaltic pumps and a specially designed commutator located at the merging point. One of the pumps delivers a sample and the other a carrier solution. The pumps are run in such a way that the total flow rate after the merging point remains permanently constant. The volume of the injected sample is determined by the time the sample delivering pump is on, whilst the dilution of the sample is determined by relative flow rates of sample and carrier solutions. Two additional possibilities are offered by the proposed system. Firstly, the volume of the injected sample plug can be varied in a simple way, and secondly, for the first time, the injection of a sample plug having an exactly predetermined concentration profile for the measured analyte at the merging point can be carried out. By introducing a third pump delivering a standard solution of the measured species, the system is able to perform a quantitative determination of an analyte, either by the standard addition method or by forming a calibration curve using only one standard solution.
Spectrophotometry

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

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

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

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

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

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

"Development Of A Generic Microelectrode Array Biosensing System"
Anal. Chim. Acta 2000 Volume 421, Issue 2 Pages 175-187
Shanqing Zhang, Huijun Zhao and Richard John

Abstract: A new type of electrochemical cell has been developed for use in biosensor applications. Utilising a random array of platinum microdiscs as the working electrode, it incorporates a Ag/AgCl reference electrode and platinum auxiliary electrode into the tip of a polished glassy Teflon probe. Immobilisation of the biochemical moiety onto the surface of the probe is achieved using a mixture of polyurethane (PU) and polyethylene oxide (PEO). Enclosing the tip of the probe within a dialysis membrane completes the electrochemical cell. The hydrophilic nature of the PU-PEO mixture ensures the biochemical moiety is trapped in a stable, hydrophilic environment. The result is an all in one generic electrochemical sensor that can be used in a wide range of biosensor applications in both batch or flow injection modes. The unique features of this system are demonstrated in this paper using the glucose - glucose oxidase (GOD) system. Parameters affecting sensor performance were investigated in both batch and flow injection modes. In terms of sensitivity, reproducibility, equilibration time and linear dynamic range, the performance of the microdisc based sensing system was superior to similar macroelectrode versions. Practical detection limits (0.1 µM) were four-five orders of magnitude better for this system compared with a conventional electrode system. The advantages of using this system in flow injection mode, particularly in terms of increased linear range, were also addressed. The overall linear range of our system (0.1 µM-60 mM) is three-four orders of magnitude greater than the conventional electrode system.
Glucose Sensor Electrode

"Flow Injection Analysis. 7. Use Of Ion-selective Electrodes For Rapid Analysis Of Soil Extracts And Blood Serum. Determination Of Potassium, Sodium And Nitrate"
Anal. Chim. Acta 1977 Volume 88, Issue 1 Pages 1-16
J. Ruzicka, E. H. Hansen and E. A. Zagatto

Abstract: The flow injection principle is used with novel design of a flow cell, in which the ion-selective an reference electrode are incorporated. The reproducible mixing of the sample with the carrier stream of electrolyte and the precise timing of potentiometric measurements in the continuously moving stream are the most important parameters influencing the quality of direct potentiometric measurements. Methods for the determination of NO3- and K in soil extracts, and Na and K in blood serum are described. At sampling rates of 125 determinations per hour, a standard deviation of only 0.8% is typical. Simultaneous measurements of two ions on one stream are described; advantages and drawbacks of the use of ion-selective electrodes in continuous-flow measurements are discussed; and the new possibilities which the flow injection method offers are contemplated.
Nitrate Potassium Sodium Blood Serum Environmental Clinical analysis Electrode Electrode Electrode Sample preparation

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

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

"A New Device For Improving Sensitivity And Stabilization In Flow Injection Analysis"
Anal. Chim. Acta 1978 Volume 97, Issue 2 Pages 427-431
H. Bergamin F, B. F. Reis and E. A. G. Zagatto

Abstract: In flow injection anal., an aqueous sample is injected into a continuous moving carrier stream of reagent. If the sample injection is done by forcing the liquid into the carrier stream, the regularity of the flow is disturbed momentarily. There is a temporary difference in mixing ratios at those points in the manifold where 2 streams meet. This can cause a change in the blank values. To minimize these changes, while increasing sensitivity, a confluence manifold was used for the spectrophotometric and/or turbidimetric determination of NO2-, SO42-, and Cl- in natural waters. An injection pulse dampener is described and is recommended when flow injection confluence systems are employed for anal. of very dilute samples.
Chloride Chlorine Chlorate ion Perchlorate Nitrite Sulfate Environmental Environmental Waste Spectrophotometry Turbidimetry

"Extraction Based On The Flow Injection Principle. 1. Description Of The Extraction System"
Anal. Chim. Acta 1978 Volume 98, Issue 1 Pages 1-7
Bo Karlberg and Sidsel Thelander

Abstract: An extraction system was developed, essentially consisting of a pump, a rotary valve, and a spectrophotmeter. The sample, 12-25 µL was introduced via the rotary valve into an aqueous stream (flow injection). The aqueous stream, containing the sample plug, was divided into small segments by an organic phase and led into a Teflon coil so that a regular pattern of the 2 phases was obtained. No air bubbles should be present. Separation of the 2 phases was achieved in a specially constructed fitting and the absorbance of the organic phase was measured. The construction and performance of the system are illustrated by determination of caffeine. Up to 100 samples/h can be analyzed with a relative precision of better than 1%
Caffeic acid Caffeine Pharmaceutical Spectrophotometry Sample preparation

"Merging Zones In Flow Injection Analysis. 1. Double Proportional Injector And Reagent Consumption"
Anal. Chim. Acta 1978 Volume 101, Issue 1 Pages 17-23
H. Bergamin F°, E. A. G. Zagatto, F. J. Krug and B. F. Reis

Abstract: A double proportional injector is described, and an improvement of the continuous-flow injection method is discussed. Sample and reagent are both injected into an inert carrier stream; the reagent is consumed only in the presence of the sample and can otherwise be recovered continuously. The main characteristics of the flow injection system, e.g. high sampling rate and good accuracy, precision, and sensitivity, are maintained. The proposed system is compared with other flow injection systems suggested earlier. The determination of phosphate in plant material by the molybdenum blue flow injection method was chosen to demonstrate the feasibility of the system; the consumption of ascorbic acid is only 9% of that in the original method.
Phosphate Phosphates Plant Spectrophotometry

"Construction And Behavior Of A Micro Flow-through Copper(II)-selective Electrode"
Anal. Chim. Acta 1978 Volume 101, Issue 2 Pages 419-422
W. E. Van Der Linden and R. Oostervink

Abstract: Two flow-through Cu2+-selective electrodes (the dismountable and disposable electrodes) were described for the continuous and flow injection determination of Cu2+. The 2 electrodes contain Cu sulfide pellets. The pellet was embedded in Polypol PS 230 polymer by using a polyethylene mould, and the polymer was hardened at 60°C. The dismountable electrode showed a fast response (90% of the max. response value in 6 s). The disposable electrode showed much slower response (90% of the max. response in ~50 s). The disposable electrode was used to monitor Cu in tap water. The determination of 10^-5 M Cu was not affected by the presence of 10^-4 M Co2+, Ni2+, Zn2+, Pb2+, and Cd2+. Fe3+ 10^-4 M showed an interference of <10%.
Copper(II) Water Electrode Electrode

"Flow Injection Analysis For Monitoring Chemiluminescent Reactions"
Anal. Chim. Acta 1980 Volume 114, Issue 1 Pages 209-214
J. L. Burguera and Alan Townshend, S. Greenfield

Abstract: Various coiled flow cells are tested for monitoring the chemiluminescence produced by the Co-catalyzed oxidation of luminol by H2O2 and the fluorescence-sensitized oxidation of sulfide by NaOCl. When a 6-coil cell is used, 10^-3-100 ng of Co2+ and 1-1000 ng S2- can be determined in 10- and 100 µL samples, respectively.
Cobalt(II) Sulfide Bioluminescence Chemiluminescence

"A Microprocessor Control System For Automated Multiple Flow Injection Analysis"
Anal. Chim. Acta 1980 Volume 114, Issue 1 Pages 119-127
K. K. Stewart, J. P. Brown and B. M. Golden*

Abstract: A microprocessor control system is reported for automated multiple flow injection analysis. The control system consists of an IMSAI-8048 microprocessor, some associated electronic interfacing and a control computer command language. The system can be programmed to control any of three versions of automated multiple flow injection analyzer.s. This control system is relatively inexpensive and is suitable for use by inexperienced personnel.

"Controlled Dynamic Titrator"
Anal. Chim. Acta 1980 Volume 114, Issue 1 Pages 247-256
S. M. Abicht*

Abstract: The controlled dynamic titrator described operates with constant titrant flow and time-proportional sample flow; sample and titrant are mixed in a microcell and the equivalence point is reached when the products of the normalities and flow rates of the titrant and the sample are equal. Titration times are measured and printed out. The concentration of the sample is inversely proportional to the titration time. The automatic titrator is discontinuous and suitable for on-line and off-line use. The cycle time of the motor-driven programmer is 2 min. Flow-through detectors for potentiometric, photometric or voltammetric indication can be used for a selection of acid-base and redox titrations. With this equipment, titration of large series of liquid samples with similar contents is simple.
Potentiometry Spectrophotometry Voltammetry

"Amperometric Flow-through Wire Detector: A Practical Design With High Sensitivity"
Anal. Chim. Acta 1980 Volume 116, Issue 1 Pages 33-39
Jean A. Lown, Ross Koile and Dennis C. Johnson

Abstract: A flow-through detector is described which is easily constructed at low cost for application to flow-injection analysis, liquid chromatography and continuous stream analysis. The platinum wire indicating electrode is stretched through a narrow channel cut in a glass-filled teflon block, which also holds the reference and auxiliary electrodes. The response of the detector to ~10^-5 M iodide and arsenic(III) solutions is compared with theoretical predictions for an annular flow cell under laminar fluid dynamics.
Arsenate ion Arsenic Iodide Amperometry HPLC

"Ion Exchange In Flow Injection Analysis. Determination Of Ammonium Ions At The µg/l Level In Natural Waters With Pulsed Nessler Reagent"
Anal. Chim. Acta 1980 Volume 117, Issue 1 Pages 81-89
H. Bergamin F, B. F. Reis, A. O. Jacintho and E. A. G. Zagatto

Abstract: Ion exchange was incorporated in flow injection analysis using a resin column in the sample loop of an electronically operated proportional injector. Effects of sample aspiration rate, sampling time, eluting agent concentration, pumping rate of the sample carrier stream, resin column size and sample acidity, were determined to develop a pre-concentration. procedure for NH4+ determination in natural waters at the µg/L level with pulsed Nessler reagent. Sample buffering before the adsorption step was done with a precision of ~2%, a sampling rate of ~40 samples/h, and a reagent consumption of 40 µL/sample, and is almost free of interferences. Recoveries of 95-105% were achieved with rain-water samples with NH4+ contents of <200 µg/L. Alternative flow diagrams and the injector command unit are discussed.
Ammonia Ammonium Rain Ion exchange Spectrophotometry

"Extraction Based On The Flow Injection Principle. 5. Assessment With A Membrane Phase Separator For Different Organic Solvents"
Anal. Chim. Acta 1980 Volume 118, Issue 2 Pages 285-292
Lage Nord, Bo Karlberg

Abstract: Several membrane phase separators have been designed and tested for use in a flow-injection extraction manifold. The membrane is sandwiched between two pieces of perspex with grooves facing the membrane. A PTFE membrane with polyethylene backing proved to be most suitable. With this type of phase separator the total dispersion in the extraction system is less than that obtained with the conventional T-piece separator. Alcohols, alkanes, chlorinated hydrocarbons and aromatic solvents pumped at a flow rate of 0.5-1.0 mL min-1 can be segmented with aqueous phase and later separated from it with a recovery of up to 95%. The organic phase passing through the detector flow cell is not contaminated by the aqueous phase to any measurable extent.
Solvents, organic Spectrophotometry Sample preparation

"Theoretical Considerations On The Performance Of Electrochemical Flow-through Detectors"
Anal. Chim. Acta 1980 Volume 121, Issue 1 Pages 13-22
H. B. Hanekamp and H. J. Van Nieuwkerk

Abstract: A survey of the equations on the limiting current in electrochemical flow-through cells is presented. For voltammetric detectors, a generalized equation for the limiting current is given. The conditions to be considered in designing an electrochemical flow-through detector for optimal signal-to-noise ratios are outlined for tubular, thin-layer, wall-jet and disk electrodes.
Potentiometry Voltammetry

"Characteristics Of An Amperometric Flow-through Detector With A Renewable Stationary Mercury Electrode"
Anal. Chim. Acta 1981 Volume 123, Issue 1 Pages 107-114
U. Baltensperger, R. Eggli

Abstract: The construction of the detector is described and its performance is assessed for 1,4-benzoquinone by flow-injection analysis. The detection limit is 0.5 ng and the relative standard deviation of the peak current is 0.4% for a 102 ng sample. The peak current is highly sensitive to temperature changes of the mercury electrode system. The relative temperature coefficient is 15% K-1, whereas the corresponding value with respect to the mobile phase is 0.6% K-1. The dependence of the peak current on the volume flow rate is described and explained by appropriate models.
Benzoquinone Electrode Amperometry

"Evaluation Of Kel-F - Graphite Electrodes As Detectors For Continuous-flow Systems"
Anal. Chim. Acta 1981 Volume 124, Issue 2 Pages 321-331
David J. Chesney, James L. Anderson, Duane E. Weisshaar and Dennis E. Tallman

Abstract: A new electrode material, fabricated from Kel-F powder and graphite powder by pressing at 250°C and 1000 p.s.i., is applied as a detector in a thin-layer, flow-through cell, for applications to continuous flow streams. The detector is useful in a wide range of solvents for a wide range of species. Applications are described for 1,1'-bis(hydroxymethyl) ferrocene (BHMF), ascorbic acid, ferrocene, phenol, and hydroquinone, using various aqueous and methanolic solvent/electrolyte compositions. Detection limits range from 800 pg for BHMF to less than 20 pg for phenol. Background current fluctuations are used to estimate flow rate stability, which is the dominant factor in setting detection limits.
Electrode

"Flow Injection Spectrophotometric Determination Of Boron In Plant Material With Azomethine-H"
Anal. Chim. Acta 1981 Volume 125, Issue 1 Pages 29-35
F. J. Krug, J. Mortatti, L. C. R. Pessenda, E. A. G. Zagatto and H. Bergamin

Abstract: A simple, fast method for the determination of boron in plant extracts is described. The method utilizes injection of 1.0 mL of an acid plant digest into a 0.1 M hydrochloric acid stream, with further addition of a buffer-masking solution and azomethine-H as the color-forming reagent. Effects of pH, kinetics of color reaction development, sample volume, reagent composition and interferences are described. The proposed method allows the analysis of plant extracts with boron contents in the range 0.1-6.0 ppm at a rate of 60 determinations per hour, with a reagent consumption of 2 mg of azomethine-H per sample. The precision is good (RSD < 1%) and the results agree with those obtained by the curcumin method.
Boron Plant Spectrophotometry

"Merging Zones In Flow Injection Analysis. 5. Simultaneous Determination Of Aluminum And Iron In Plant Digests By A Zone-sampling Approach"
Anal. Chim. Acta 1981 Volume 125, Issue 1 Pages 37-43
E. A. G. Zagatto, A. O. Jacintho, L. C. R. Pessenda, F. J. Krug, B. F. Reis and H. Bergamin F

Abstract: A flow injection procedure is proposed for the simultaneous determination of aluminium and iron in plant material. The method is based on a flow configuration involving zone sampling and merging zones. Aluminium is determined spectrophotometrically with eriochrome cyanine R as reagent and iron by atomic absorption spectrometry. The advantages of this method over other procedures already reported are discussed. The effects of reagent composition for the aluminium determination are described in detail. The zone-sampling approach permits an easier pH control in the aluminium determinations so interferences caused by variations in sample acidity are avoided without the need for very concentrated buffers. The merging zones configuration greatly reduces the consumption of reagents. The proposed method permits the analysis of about 120 samples (240 determinations) per hour, with good precision (RSD < 2%) in both the aluminium and iron channels. The results agree with those obtained by inductively-coupled argon plasma spectrometry.
Iron Aluminum Plant Sample preparation Spectrophotometry

"Synchronization Of Signal Sampling With Liquid Pulsation In Systems With Peristaltic Pumps"
Anal. Chim. Acta 1981 Volume 127, Issue 1 Pages 239-243
F. Opekar and A. Troj&aacute;nek

Abstract: Method and electronic circuitry are described for synchronization of analytical signal sampling with pulsation of liquid flow in systems with a peristaltic pump. The technique is illustrated for cathodic stripping voltammetry of manganese.
Manganese Voltammetry

"An Electrochemical Reactivation Method For Solid Electrodes Used In Electrochemical Detectors For High Performance Liquid Chromatography And Flow Injection Analysis"
Anal. Chim. Acta 1981 Volume 130, Issue 1 Pages 9-22
H. W. Van Rooijen and H. Poppe

Abstract: An electrochemical reactivation method for solid electrodes used in electrochemical detectors is optimized for glassy carbon electrodes. Application of a voltage pulse train for 5 min is effective in restoring the response of the electrode after deactivation by organic compounds. Potassium hexacyanoferrate(II) and DL-synephrine were used to test the reactivation of electrodes; 2,6-dihydroxybenzoic acid and urine served to deactivate them. The effects of the amplitude, DC level, and frequency of the applied voltage pulse train, as well as the mode of termination, are discussed.
HPLC Electrode Potentiometry

"Flow Injection Systems With Inductively-coupled Argon Plasma Atomic Emission Spectrometry. 1. Fundamental Considerations"
Anal. Chim. Acta 1981 Volume 130, Issue 2 Pages 243-255
A. O. Jacintho, E. A. G. Zagatto, H. Bergamin F, F. J. Krug and B. F. ReisR. E. BrunsB. R. Kowalski

Abstract: Flow injection systems with inductively-coupled argon plasma atomic emission spectromeiry are proposed. Effects of flow rates, injected volumes and mixing Coil lengths are investigated and conditions for the measurement of the flow injection transient signal are discussed. The peak profile measured with the spectrometer corresponds well with the estimate of the true sample zone distribution near the inlet of the spectrometer made by a zone-sampling process; thus the plasma is not a limiting factor in the proposed systems. For plant analysis, the system provides nearly zero sample dispersion and so the inherent sensitivity of the spectrometric method is preserved. The results obtained for 10 elements in the NBS Orchard Leaves reference material (SRM 1571) are in good agreement with the certified values. For determinations of calcium and magnesium in dolomitic limestones, cadmium is used as internal standard and so the merging zones configuration is employed. The proposed system provides medium sample dispersion and permits about 100 samples to be analyzed per hour. Relative standard deviations of 1.34% and 1.23% were calculated for the calcium and magnesium data, respectively. The analytical results compare favorably with those obtained by normal i.c.p. spectrometry with pneumatic sample aspiration, after manual sample dilution.
Calcium Magnesium Plant Spectrophotometry

"Merging Zones In Flow Injection Analysis. 6. Determination Of Calcium In Natural Waters, Soil And Plant Materials With Glyoxal-bis(2-hydroxanil)"
Anal. Chim. Acta 1981 Volume 130, Issue 2 Pages 361-368
A. O. Jacintho, E. A. G. Zagatto, B. F. Reis, L. C. R. Pessenda and F. J. Krug

Abstract: A flow injection procedure is proposed for the spectrophotometric determination of calcium in natural waters, soil extracts and plant digests, employing glyoxal bis(2-hydroxyanil) as the color-forming reagent. The necessary dissociation of this reagent, which is rather slow, proceeds outside the analytical path, and the merging-zones approach is used for reagent addition. Composition of reagents, dissociation time of the colorforming reagent, ethanol content in the carrier streams and interferences are described. In the analysis of plant and soil materials, zone sampling is required for initial sample dilution. The proposed systems are very stable and permit a sampling rate of 180 determinations per hour. Relative standard deviations are less than 1%. The results compare well with those obtained by inductively-coupled argon-plasma atomic emission spectrometry.
Calcium Environmental Environmental Plant Spectrophotometry

"Spectrophotometric Flow Injection Determination Of Chloride In Ethanol"
Anal. Chim. Acta 1981 Volume 130, Issue 2 Pages 409-413
F. J. Krug, L. C. R. Pessenda, E. A. G. Zagatto, A. O. Jacintho and B. F. Reis

Abstract: A flow injection procedure is described for the spectrophotometric determination of chloride in ethanol, based on the mercury(II) thiocyanate-iron(III) reaction. Effects of reagent composition and ethanol content of the sample are investigated in detail. The proposed system can analyze 120 samples of ethanol (94-100% v/v) per hour, with a relative standard deviation lower than 1%, when the chloride content ranges from 0.1-6.0 ppm. Recoveries of ~96% are found.
Chloride Organic compound Spectrophotometry

"Flow Injection Analyzer For Students, Teaching And Research. Spectrophotometric Methods"
Anal. Chim. Acta 1982 Volume 134, Issue 1 Pages 55-71
J. Rika, E. H. Hansen and A. U. Ramsing

Abstract: The flow streams in simple manifolds are propelled by controlled gas pressure; ancillary equipment consists of a small spectrophotometer or colorimeter and a chart recorder. The analytical result is available in less than 20 s after sample injection, with a reproducibility better than 1%, using microlitre volumes of sample and less than millilitre volumes of reagent per assay. These are the performance data of a simple, robust and inexpensive flow injection analyzer designed for use with a wide range of detectors. The application spectrophotometry is illustrated by five exercises aimed at teaching instrumental analysis and intended for those who wish to introduce flow injection analysis in their laboratories.
Calcium Chloride Chromium(VI) Fluorescence Luminescence Potentiometry Spectrophotometry

"The Performance Of Some Liquid Phase Flow-through Detectors"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 17-26
H. Poppe

Abstract: Miniaturization of flow-through analytical systems such as flow injection analysis and liquid chromatography is necessary to achieve higher rates of sample throughput and smaller absolute detection limits. During this miniaturization, however, it is essential to preserve the concentration detection limits of the devices used. Some principles for liquid phase flow-through detection, u.v.-visible absorption photometry, fluorimetry and electrochemical detection, are discussed from this point of view. It appears that, although technical difficulties will be large, there are good prospects of detecting concentrations of about 1 ng mL-1, while keeping the peak broaadening down to values of about 1 nl.
Electrode Fluorescence Spectrophotometry

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

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

"Performance And Characteristics Of The Fluoride-selective Electrode In A Flow Injection System"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 207-212
P. Van Den Winkel and G. De Backer, M. Vandeputte, N. Mertens, L. Dryon and D. L. Massart

Abstract: A simple, inexpensive home-made timer for coupling cam-controlled samplers to injectors for flow injection analysis is presented. Experimental conditions and a flow diagram are described for the determination of fluoride by means of a fluoride-selective electrode in the concentration range 0.3-10 ppm, with a sample rate up to 120 hr-1.
Fluoride Urine Environmental Electrode

"The Vibrating Wire Electrode As An Amperometric Detector For Flow Injection Systems"
Anal. Chim. Acta 1983 Volume 148, Issue 1 Pages 87-101
Kenneth W. Pratt, Jr. and Dennis C. Johnson

Abstract: The application of vibrating wire electrodes for amperometric detection in flow-injection systems is reported. Equations of response for these electrodes in a flow-through cell are derived and verified experimentally. The applicability of the equation for other convective detectors in flow-through cells is discussed. A detection limit of 5 x 10^-10 M iodide and a linear dynamic range of 6.3 decades were obtained for a platinum vibrating wire electrode.
Iodine Inorganic compound Amperometry Electrode

"Flow Electrolysis At A Porous Tubular Electrode With Internal Stirring"
Anal. Chim. Acta 1983 Volume 151, Issue 1 Pages 109-116
Joseph Wang and Bassam A. Freiha

Abstract: The design and properties of a porous tubular electrode, in which effective mass transport is ensured by a stirrer rotating inside the tube, are described. High currents are possible owing to the high surface area and mass transport rates. The dependence of the limiting current and the degree of conversion on stirring and flow rate and on electrode length are described. A hydrodynamic modulation mode, based on measuring the current difference while switching the stirrer on and off, is used to correct for background. The cell was used for the determination of caffeic acid, paracetamol, dopamine and Fe(CN)64- in flow injection and continuous-flow analyzes, with detection limits at the nM level.
4-Acetylaminophenol Caffeic acid Dopamine Hexacyanoferrate(II) Electrode Electrode Electrode Voltammetry Hydrodynamic modulation

"Bipolar-pulse Conductometric Monitoring Of Ion-selective Electrodes. 3. Studies With Calcium And Fluoride Electrodes In A Continuous-flow System"
Anal. Chim. Acta 1983 Volume 152, Issue 1 Pages 173-190
Charles R. Powley and Timothy A. Nieman

Abstract: The use is described of bipolar-pulse conductometric monitoring of a Ca(II)-selective electrode in a computer-controlled unsegmented continuous-flow system (flow rate 20 mL min-1) with a PTFE cell (volume ~300 µL) defined by two end plates separated by a spacer (1.6 mm thick). One end plate is drilled to take the ion-selective electrode (a polished brass rod coated with a Ca(II)-selective membrane) and a stainless-steel counter-electrode. The other end plate is drilled to take two stainless-steel counter-electrodes and to provide inlet and outlet for carrier solution (0.1 M KCl). The location and composition of the counter-electrodes are critical. For conductometric measurements (cf. Parts I and II, Anal. Abstr., 1983, 44, 2B36, 2B123), a rapid series of current measurements is made at various pulse heights, and the rectilinear current - voltage plot obtained is extrapolated to 0.0 V. No reference electrode is necessary. The detection limit (at I >1 mM) is ~1 µM Ca, and the precision is better than in static solution Drifts observed previously (loc. cit.) are much less in the proposed system. The effects of interfering species on response time are discussed. A similar system is used for the determination of F-.
Calcium Fluoride Electrode Electrode Conductometry

"A Simple Procedure For Standard Additions In Flow Injection Analysis. Spectrophotometric Determination Of Nitrate In Plant Extracts"
Anal. Chim. Acta 1983 Volume 155, Issue 1 Pages 131-138
M. F. Gin&eacute;, B. F. Reis, E. A. G. Zaatto, F. J. Krug and A. O. Jacintho

Abstract: A standard solution of NO3- is injected into water as carrier, creating a zone that undergoes continuous dispersion as it is carried through a coil. After a pre-selected time interval, Δt, a segment of the dispersed zone is introduced into a second water carrier stream and, simultaneously, the sample is injected into its carrier stream. The two established zones merge and undergo all the required physico-chemical steps before reaching the detector. The amount of standard added is determined by the value of Δt, so that several standard additions can be made by varying Δt. Application of the method is illustrated by the spectrophotometric determination of NO3- in extracts of plant leaves. Results on seven samples (12 additions per sample) agreed well with those by the corresponding manual procedure.
Nitrate Plant Sample preparation Spectrophotometry

"Integrated Microconduits For Flow Injection Analysis"
Anal. Chim. Acta 1984 Volume 161, Issue 1 Pages 1-25
Jaromir Rika and Elo H. Hansen

Abstract: The novel continuous-flow arrangement described is little larger than a credit card, and the channels linking the injection unit, mixing coils, dialysis or diffusion units and detectors are fabricated by impression or engraving into a block (7 cm x 4.5 cm x 1.0 cm) of transparent PVC. Connections to one or more detectors are provided. The versatility of the arrangement is demonstrated for a number of flow injection systems with integrated potentiometric or optical detectors and with integrated gas diffusion or ion-exchange units.
Calcium pH Ion exchange Potentiometry Spectrophotometry

"A Swept-potential Electrochemical Detector For Flow Streams"
Anal. Chim. Acta 1984 Volume 162, Issue 1 Pages 175-187
Patricia A. Reardon, Gerald E. O'Brien and Peter E. Sturrock

Abstract: The detector described (cf. Scanlon et al., Anal. Abstr., 1984, 46, 12C32), which is essentially a computer-controlled potentiostat, has been primarily operated in the rapid-sweep square-wave voltammetric mode for use in HPLC, flow injection analysis and ion chromatography. Programs are available for offline data processing and for visual display of any voltammogram or current vs. time plot; any real-time alphanumeric or graphics display can be copied on a dot-matrix printer. A simplified diagram of the potentiostat and a block diagram of the whole detection system linked to a HPLC system are presented. Detection limits of <1 nM (for Pb and Cd) have been attained with this potentiostat.
Cadmium Lead HPIC HPLC Potentiometry Voltammetry

"Evaluation Of A Dialysis Probe For Continuous Sampling In Fermentors And In Complex Media"
Anal. Chim. Acta 1984 Volume 163, Issue 1 Pages 135-141
C. F. Mandenius, B. Danielsson and B. Mattiasson

Abstract: The steam-sterilizable probe described yields samples suitable for, e.g., HPLC, flow injection analysis or enzyme calorimetry. The analyte is transferred from the sample to a flowing stream by passage through a dialysis membrane that is protected from fouling by the sample mixture by means of a magnetic stirring-bar rotating close to the membrane surface.
Fermentation broth Milk Waste

"Simultaneous Determination Of Hypoxanthine, Inosine, Inosine-5'-phosphate And Adenosine-5'-phosphate With A Multielectrode Enzyme Sensor"
Anal. Chim. Acta 1984 Volume 164, Issue 1 Pages 139-146
Etsuo Watanabe, Shunsuke Tokimatsu and Kenzo Toyama, Isao Karube, Hideaki Matsuoka and Shuichi Suzuki

Abstract: A multielectrode enzyme sensor for the simultaneous determination of adenosine-5'-phosphate (AMP), inosine-5'-phosphate (IMP), inosine (HXR) and hypoxanthine (HX)in fish meat was developed by assembling four enzyme sensors for AMP, IMP, HXR and HX in a flow cell. These compounds were determined from oxygen consumption according to the following reactions: AMP→IMP→HXR→HX→Uric acid where AD is AMP deaminase, NT is 5'-nucleotidase, NP is nucleoside phosphorylase and XO is xanthine oxidase. Enzymes were covalently bound to a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane and glutaraldehyde. Sensors for HX, HXR, IMP and AMP were prepared by attaching membranes of XO, XO---NP, XO--- NP---NT, and of XO---NP---NT and AD, respectively, to four oxygen electrodes. Samples extracted from sea bass, bream, flounder, abalone and arkshell were analyzed within 5 min, from the simultaneous response curves of the four electrodes. Results obtained by the multisensor system were in good agreement with those determined by each single electrode.
Food Electrode Sensor

"Spectroelectrochemical Detector For Flow Injection Systems And Liquid Chromatography"
Anal. Chim. Acta 1984 Volume 166, Issue 1 Pages 163-170
Howard D. Dewald and Joseph Wang

Abstract: Details are given for the construction of two spectroelectrochemical flow-cells (with diagrams). The cells have a rectangular flow channel (15 mm x 5 mm for flow injection and 12 mm x 2 mm for HPLC) with a reticulated vitreous-carbon working electrode and an open optical window; the total dead volume of the cells is 27 µL (HPLC) and 80 µL (flow injection). Absorption spectra were recorded with 2-s response and 2-nm manual slit width, and potential measurements were made vs. a silver - AgCl (3 M NaCl) reference electrode, the stainless-steel tube of which acted as an auxiliary electrode. For flow injection systems, components in binary mixtures can be determined; for HPLC, simultaneous absorbance and electrochemical chromatograms allow more compounds to be identified and quantified. Mixtures of nitro- and chloro-phenols have been used to illustrate this simultaneous profiling of spectral and redox properties.
HPLC Electrode Electrode Spectrophotometry Spectroelectrochemistry

"Simple Multifunctional Valve For Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 169, Issue 1 Pages 51-57
S. Storgaard J&oslash;rgensen, Katrine Maria Petersen and Lone Anette Hansen

Abstract: The construction and use of a versatile, simple, pneumatically operated two-layer rotary valve are described for the simultaneous introduction of samples and diversion of analytical streams in flow injection analysis. Examples are presented of the determination of Fe by the 1,10-phenanthroline method with use of the valve in the time-controlled or loop-controlled sampling mode and of its use for pre-concentration on an ion-exchange column.
Iron(2+) Ion exchange Spectrophotometry

"Design And Evaluation Of A New Phase Separator For Liquid-liquid Extraction In Flow Systems"
Anal. Chim. Acta 1985 Volume 169, Issue 1 Pages 43-49
Kenneth B&auml;ckstr&ouml;m, Lars-G&ouml;ran Danielsson and Lage Nord

Abstract: A modified phase separator incorporating a supported teflon membrane is described. The separator has very high phase-separation efficiency even under extreme conditions of phase-volume ratio and total flow rate. The use of appropriate support is shown to give much better endurance to the membrane. Even pressures high enough to make water penetrate the membrane did not cause any damage, which makes the system much easier to handle. The long-term stability of the separator was found to be good and very little of the aqueous phase penetrated the membrane.
Sample preparation

"A Submersible Flow Analysis System"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 245-257
Kenneth S. Johnson, Carl L. Beehler and Carole M. Sakamoto-Arnold

Abstract: A submersible chemical analyzer. (SCANNER) that is capable of virtually an in situ spectrophotometric determination in seawater has been applied to the determination of silicate by the molybdenum blue method and of S2- by the methylene blue procedure. The coefficient of variation for 0.1 mM silicate and 25 µM-S2- are 0.6 and 0.5%, respectively, in laboratory tests; results are similar for in situ analysis of seawater at a depth of 2500 m. Detection limits are ~0.1 µM.
Silicate Sulfide Sea Spectrophotometry

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

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

"A Simple Injection Valve For Flow Injection Analysis"
Anal. Chim. Acta 1986 Volume 181, Issue 1 Pages 283-285
J. R. Chipperfield and P. J. Worsfold

Abstract: Sketches and a description are give of a maintenance-free, all-glass sample introduction valve, based on a modified syringe with ground-glass contact. Samples (>1.4 µL) can be injected manually or driven with a 12-V solenoid. The coefficient of variation (n = 11) of the peak height of the detector response was 1% for a sampling rate of 90 h-1 during a simple test by spectrophotometric monitoring of injections of aqueous methyl orange (0.06 g l-1).
Methyl orange Spectrophotometry

"Instrumental Configurations For The Determination Of Sub-micromolar Concentrations Of Electroactive Species With Carbon, Gold And Platinum Micro-disc Electrodes In Static And Flow-through Cells"
Anal. Chim. Acta 1986 Volume 187, Issue 1 Pages 67-77
J. W. Bixler, A. M. Bond, P. A. Lay, W. Thormann and P. van den Bosch, M. Fleischmann, B. S. Pons

Abstract: Methods are described for preparing platinum, gold and carbon micro-disc electrodes, with diameter of 1 to 60 µm, for use in both stationary and continuous-flow configurations. For both dilute solution of analytes and micro-disc electrodes with diameter <10 µm, simple instrumentation comprising a computer-based function generator and data acquisition system and a pico- or femto-ammeter (as current amplifier), used in a two-electrode configuration, is preferred to the usual potentiostatic three-electrode configuration. However, commercial pico- or femto-ammeters have large time constants (>1 ms) and measurements are therefore restricted to slow scan rates, large pulse widths and low frequencies.
Voltammetry Electrode Electrode Electrode

"Photo-cured Polymers In Ion-selective Electrode Membranes. 3. A Potassium Electrode For Flow Injection Analysis"
Anal. Chim. Acta 1988 Volume 204, Issue 1-2 Pages 329-332
T. J. Cardwell, R. W. Cattrall and P. J. Iles, I. C. Hamilton

Abstract: The preparation is described of a K-selective electrode based on a photo-cured polymer membrane containing valinomycin. The response characteristics are similar to those of a PVC-based electrode containing the same neutral carrier. The electrode is suitable for use in flow injection systems due to its fast initial response and the hardness and mechanical strength of the membrane. Response was near-Nernstian from 0.1 M to 0.1 mM K+.
Potassium Electrode Electrode

"Simple Antilog Converter For Conventional And Flow Injection Measurements With Ion-selective Electrodes"
Anal. Chim. Acta 1988 Volume 207, Issue 1-2 Pages 325-330
Marek Trojanowicz and Tadeusz Krawczyski vel Krawczyk, Wodzimierz Augustyniak

Abstract: A simple antilog. converter based on an antilog. amplifier is described. In potentiometric measurements it produced an output voltage which depended rectilinearly on the concentration. of the sensed species over two orders of magnitude. Signals obtained in measurements with Cl-, F-, K+ and Cu(II) ion-selective electrodes ranged from 1.0 to 10.0 V. The converter was used for flow injection potentiometry within one concentration. decade, but its sensitivity depended on the dispersion in the flow system.
Chloride Copper(II) Fluoride Potassium Electrode Electrode Electrode Electrode Potentiometry

"Anodic Amperometry And Kinetics Of 2 To 4-carbon Glycols At The Nickel Electrode"
Anal. Chim. Acta 1988 Volume 208, Issue 1-2 Pages 247-254
Nader Botros and Calvin O. Huber

Abstract: Anodic amperometry of nine C3 and C4 alcohols and diols, plus ethanediol and glycerol, was studied at +0.55 V (vs. the SCE) in 0.1 M NaOH containing suspended Ni(OH)2 (from adding 10 mM NiSO4). The flow injection cell contained a 10-mm Ni-wire (0.64 mm diameter) working electrode and a 20-mm Pt-wire auxiliary electrode. The upper limit of rectilinearity (peak current vs. concentration.) was ~0.25 mM and the lower detection limit was 0.2 µM (propane-1,3-diol). Primary alcohols yielded larger current sensitivities than secondary alcohols.
Alcohols, primary Alcohols, secondary Butanol, 1- 2-Propanol 1-Propanol Diols 1,1-Ethanediol Glycerol Amperometry Electrode

"Initial Studies Of Large-bore Flow Injection Systems"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 391-396
K. A. McGowan and G. E. Pacey

Abstract: The effects were studied of increasing the i.d. of coiled tubing for flow injection analysis; two systems were investigated as examples, viz, bromothymol blue dye with Na2B4O7 buffer (used to evaluate the physical dispersion coefficient of flow injection manifolds) and the determination of NO3- with sulfanilamide and N-(1-naphthyl)ethylenediamine. Results indicated that the essential characteristics of dispersion were maintained with tubing diameter up to 1.3 mm when the chemical reaction was slow or if stopped-flow conditions were used.
Bromothymol blue Spectrophotometry Turbidimetry

"Dual-electrode Configurations With A Plant Tissue As Generator Reactor"
Anal. Chim. Acta 1989 Volume 218, Issue 2 Pages 281-290
Joseph Wang and Meng-Shan Lin

Abstract: One electrode design was of the thin-layer type used in LC - electrochemistry; it had two circular cavities (2.5 mm diameter; 2 mm deep) in series containing disc-shaped slices of tissue (upstream) and carbon paste (downstream), and incorporated a Ag - AgCl (3 M NaCl) reference electrode positioned downstream. The other was a rotating ring - disc design, having a tissue disc and a carbon paste ring, separated by a PTFE tube, assembled in a Plexiglas tip; it was used in conjunction with a Pt-wire auxiliary electrode and a Ag - AgCl (3 M NaCl) reference electrode in a Pyrex cell. A 0.05 M phosphate buffer of pH 7.4 was used as sample medium and carrier solution for batch and flow injection analyzes, and contained o-phenylenediamine when H2O2 was to be detected. Amperometric detection at -0.2 V was used throughout. Mushroom, horse-radish root or banana tissue was used as tissue generator; the tyrosinase, peroxidase or catechol oxidase in the respective tissue allowed the determination of 25 µM-catechol, -H2O2 or -dopamine, respectively. With the banana tissue, the detection limit for dopamine was 1.9 µM. Response times (to reach 90% of the max. signal) ranged from 3 to 11 s, and 45 to 60 samples h-1 could be injected. Response was rectilinear up to 0.1 mM or better; for flow injection measurement at this level, coefficient of variation were 2.3% (n = 10) with the series-flow detector.
Hydrogen peroxide Dopamine Catechol Sensor Electrode

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

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

"Simultaneous Spectrophotometric Determination Of Lanthanum And Calcium With An Automated Flow Injection Analyser"
Anal. Chim. Acta 1989 Volume 222, Issue 1 Pages 205-209
Danhua Chen, Ruxiu Cai and Yun'e Zeng

Abstract: Lanthanum and total lanthanum plus calcium were determined by flow injection analysis (apparatus described and illustrated) with use of 2-(2-arsenophenylazo)-7-(2,4,6-trichlorophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid and 7-(4-fluoriphenylazo)-2-(2-phosphono-4-chlorophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate, respectively; Ca was determined by calculation. Calibration graphs were rectilinear for 0.2 to 1.6 µg mL-1 of Ca and La. The injection rate was 90 h-1, and coefficient of variation were generally 5% (n = 5). Magnesium, Cu(II), Fe(II) and Mn(II) interfered significantly with the determination of calcium. Interference from Fe(III) in the determination of La could be eliminated by addition of 1% ascorbic acid solution
Lanthanum Calcium Spectrophotometry

"Comparative Study Of First-generation, Second-generation And Third-generation Amperometric Glucose Enzyme Electrodes In Continuous-flow Analysis Of Undiluted Whole-blood"
Anal. Chim. Acta 1990 Volume 234, Issue 2 Pages 321-330
Hari Gunasingham and Chin-Huat Tan, Tar-Choon Aw

Abstract: First-, second- and third-generation amperometric glucose enzyme electrodes were compared under flow injection and steady-state conditions for the monitoring of undiluted whole blood. Measurements were made in a large volume wall-jet cell (illustrated) with a four-way manual injection value, a sample loop of 25 µL or 200 µL for flow injection and steady-state modes, respectively, and a graphite counter electrode vs. Ag - AgCl. Use of first-generation electrodes, based on H2O2 detection at a Pt electrode, was limited by their instability. Second-generation electrodes in which re-oxidation of glucose oxidase occurs by a mediator are more suitable for blood analysis however the choice of mediator is important. With regard to the rectilinearity and stability, tetrathiafulvalene achieves better results than dimethyl ferrocene. Third-generatin electrodes based on tetrathiafulvaleine - teracyanoquinodimethane where direct oxidation of glucose oxidase occurs, were also useful, but display lower stability and a smaller dynamic range than second-generation devices. The calibration graphs for first, second and third-generation electrodes were rectilinear up to 10, 35 and 25 mM for steady-state analysis and 25, 80 and 60 mM for flow injection analysis, respectively.
Glucose Whole Amperometry Electrode Electrode Electrode

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

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

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

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

"Design Of A Multi-channel Dropping Segmenter For Liquid Liquid Extraction Continuous-flow Injection Analysis"
Anal. Chim. Acta 1991 Volume 245, Issue 2 Pages 251-257
Vlastimil Kuban and Folke Ingman

Abstract: A simple dual-channel dropping segmenter was used for the simultaneous introduction of aqueous solutions of a sample and an organic analytical reagent directly into a continuous flow of an immiscible organic solvent. Droplets of precisely defined volume of the homogeneous reaction mixture are formed at the junction of the inlet capillary system. Reaction and extraction take place simultaneously in the individual segments of the aqueous phase during the transport through the reaction/extraction coil. An analytical signal is measured by an 'on-tube' fast-reading spectrophotometric detector and processed mathematically. The applicability of the method is demonstrated with the determination of Cu(II) ions with tetramethylene-dithiocarbamate in neutral medium in 0.1 M ammonium acetate buffer.
Sample preparation

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

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

"Exploiting Stopped-flow Injection Methods For Quantitative Chemical Assays"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 11-21
Gary D. Christian* and Jaromir Rika

Abstract: In this review, the advantages of stopped-flow flow injection techniques are illustrated by a range of analyzes developed in the author's laboratory. These include enzymatic measurements for monitoring biological processes, monitoring of enzyme reactions on solid surfaces (e.g., membranes or C18 silica particles), membrane pre-concentration. and FTIR spectrometry. The sequential injection technique and means of controlling flow are also discussed. (57 references). Advantages of the stopped-flow injection techniques are emphasized and illustrated by examples of assays developed in the authors' lab., including enzymatic measurements for bioprocess monitoring, the monitoring of enzyme reactions on solid surfaces, the determination of reaction rate constants, membrane pre-concentration. of mol. species, flow injection Fourier transform IR measurements and a novel type of flow injection coulometric titration Sequential injection anal., a next generation of stopped-flow injection methodologies, is discussed together with new ways of propelling and controlling flows, including novel syringe-based devices.
Spectrophotometry

"Potentiometric Flow Analysis Device Using Membrane-coated Carbon-rod Ion-selective Electrode Detectors"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 399-404
Enju Wang and Satsuo Kamata*

Abstract: To prepare an ion-selective electrode for Cu2+, a carbon rod (7 cm x 4 mm) with a polished tip was coated with a composition containing (by wt.) 3% of tetraisobutylthiuram disulfide, 0.7% of K tetrakis-(4-chlorophenylborate), 63.1% of 2-nitrophenyl octyl ether (I) and 33.2% of PVC; for anions the composition contained 3.3% of propane-1,2-diylbis(diphenylphosphine), 66.7% of I and 30% of PVC. Either electrode was conditioned in 1 mM Cu2+ before use as detector in the PTFE cell of a simple flow system. For the determination of anions, the filtered and diluted sample (30 to 100 µL) was injected into 0.01 M NaH2PO4 as carrier. The peak potential of the electrode was rectilinearly related the log. concentration. of SCN-, ClO4-, NO3- or Cl- over approximately three decades of concentration. For Cu2+, a continuous-flow system was used with the sample stream buffered at pH 6 with 0.01 M acetate. The rectilinear pCu range was 2 to 5.5. Recoveries of Cu2+ or ClO4- were 97% at 50 µM. The flow injection method was successfully applied to the determination of Cl- in seawater and urine. The electrodes could be used continuously for 2 weeks; the carbon rod could then be cleaned and re-coated. A flow-through anal. system that utilizes a membrane-coated carbon rod ion-selective electrode was investigated. Electrodes for Cu2+ based on a thiuram disulfide neutral carrier and for ClO4-, SCN-, NO3- and Cl- based on a bis(diphenylphosphino)propane-copper complex as ion exchanger exhibited satisfactory performance in a continuous-flow system. The response of the anion electrodes in a flow injection system was near Nernstian in the concentration. range 10^-2-10-4 or 10^-5M. Highly reproducible measurements were obtained with sample volumes of 30-100 µL and a sample injection rate of up to 400 h-1. The chloride electrode was suitable for the FIA determination of Cl- in seawater and urine.
Chloride Sea Urine Electrode Electrode Electrode Potentiometry

"Application Of Three Chromogenic Reagents To The Determination Of Palladium Using A Laboratory-made Optical-fibre Detector For Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 262, Issue 1 Pages 97-102
Yanjun Xu, Xingguo Chen, Mancang Liu and Zhide Hu

Abstract: The design and operation of an optical-fiber detector are presented. Palladium in refined ores was determined with 3-(4-chloro-2-phosphonophenylazo)-6-(6,8-disulfo-2-naphthylazo)chromotropic acid (I), 3-(4-chloro-2-phosphonophenylazo)-6-(4-sulfamoylphenylazo)chromotropic acid (II) or N-~4-[7-(4-chloro-2-phosphonophenylazo)-1,8-dihydroxy-3,6-disulfo-2-naphthylazo]benzoyl~glycine (III) as chromogenic reagent. All measurements were made at 90°C and in acidic (H2SO4) medium. The system was optimized in respect of concentration. of the chromogenic reagent, acidity and temperature Results were obtained from calibration graphs, which obeyed Beer's law in the ranges 1 to 3, 1 to 4 and 1 to 5 µg mL-1 for I, II and III, respectively; the corresponding ε values were 4.3 x 10^4 (650 nm), 3.0 x 10^4 (640 nm) and 3.4 x 10^4 (630 nm). In each instance the limit of detection was 0.5 µg mL-1. Recoveries were >90% and there was no interference from co-existing noble-metal ions. Results were compared with those obtained with a spectrophotometric detector. Palladium in ores was determined by a method in which an optical fiber detector is connected to a flow injection analysis system and using three chromogenic reagents, i.e., 1,8-dihydroxy-2-(4-chloro-2-phosphonophenylazo)-7-(6,8- disulfonaphthylazo)naphthalene (I), 1,8-dihydroxy-2-(4-chloro-2- phosphonophenylazo)-7-(4-sulfonamidophenylazo)-3,6- disulfonaphthalene (II) and 1,8-dihydroxy-2-(4-chloro-2- phosphonophenylazo)-7-(p-hippuric acid azo)-3,6-disulfonaphthalene (III). The methods are simple, rapid and selective. In the Pd-I system, the molar absorptivity is 4.3 x 10^4 L mol-1 cm-1 at 650 nm and Beer's law is obeyed in the range 1-3 µg Pd mL-1. In the Pd-II system, the molar absorptivity is 3.0 x 10^4 L mol-1 cm-1 at 640 nm and Beer's law is obeyed in the range 1-4 µg Pd mL-1. In the Pd-III system, the molar absorptivity is 3.4 x 10^4 L mol-1 cm-1 at 630 nm and Beer's law is obeyed in the range 1-5 µg Pd mL-1. Coexisting noble metal ions do not interfere. An optical fiber detection cell for flow injection analysis and an optical fiber-spectrophotometer were designed and constructed in house.
Palladium Refined Spectrophotometry

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

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

"Simultaneous Determination Of Nitrate And Chloride By Means Of Flow Injection Amperometry At The Membrane-stabilized Water - Nitrobenzene Interface"
Anal. Chim. Acta 1992 Volume 268, Issue 2 Pages 285-292
Stefan Wilke*, Halka Franzke and Helmut M&uuml;ller

Abstract: Sample solution (16 µL) was injected into a carrier stream of water which merged with a supporting electrolyte of aqueous 10 mM Na2SO4; the flow rate of each stream was 1 mL min-1. The flow-through electrochemical detector cell (illustrated) contained a hydrophilic membrane filter of regenerated celullose (RC 58, Schleicher and Schuell) to stabilize the interface between the aqueous solution and an organic phase of 10 mM µ-nitridobis(triphenylphosphorus) dicarbollylcobaltate in nitrobenzene. Two Ag wires in the organic phase were used as reference and auxiliary electrodes while in the aqueous phase a Ag - AgCl electrode and the stainless-steel cell body were used. The electrodes were connected to a potentiostat (cf. Wilke, J. Electroanal. Chem., 1991, 301, 67), the filtered output from which was recorded. The results obtained for NO3- agreed well with those obtained by ion chromatography. The detector was ~11 times more sensitive to NO3- than to Cl-, and measurements of Cl- were thus only possible at high concentration. The technique was used to determine NO3- and Cl- in river water. An amperometric flow-through electrode based on ion transfer across the interface of 2 immiscible electrolyte solutions was developed. A hydrophilic cellulose membrane was utilized to stabilize the interface between the flowing aqueous solution and the stationary organic phase. The detector developed was applied in a flow injection system for the simultaneous determination of NO3- and Cl- in river water. Advantage was taken of the potential-dependent response of the amperometric detector and the sufficiently separated half-wave potentials of the transfer of NO3- and Cl- across the interface. The results obtained in the amperometric determination of NO3- agreed well with those from ion chromatography measurements. Because of the comparatively poor selectivity of the detector for Cl-, the amperometric determination can be used only when the Cl- concentration. of the sample is sufficiently high.
Nitrate Chloride River Amperometry Electrode

"Thickness-shear-mode Acoustic Wave Sensors And Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 269, Issue 2 Pages 167-175
Mengsu Yang and Michael Thompson*

Abstract: The feasibility of coupling a thickness-shear-mode (TSM) quartz-crystal sensor to a flow injection system was evaluated using network analysis. The flow injection analysis system (diagram given) consisted of a four-channel EVA-Pump Model 1000 peristaltic pump combined with a EVA-Valve Model 2000 injector valve. The PTFE tubing for the sample loop had an i.d. of 0.5 mm and all other tubing had an i.d. of 0.8 m. The 9 MHz AT-cut quartz piezoelectric crystals were coated with either Au or Ag electrodes. The quartz crystal was characterized using an HP 4195A Network/Spectrum Analyser. Flow injection analysis provided a method to relate the hydrodynamic response of the sensor to the concentration profile of the analyte produced by the dispersion behavior of sample zones. Network analysis of the thickness-shear mode sensor provided data on the bulk properties of the liquid sample and surface properties at the liquid - solid interface. A feasibility study of the combination of the flow injection analysis (FIA) technique with the piezoelec. acoustic wave sensor (thickness-shear mode, TSM) is described. Flow -injection systems provide a method to relate the hydrodynamic response of the sensor to the concentration.-time profile of the analyte produced by the dispersion behavior of sample zones. Network anal. of the TSM sensor generates multi-dimensional information on the bulk properties of the liquid sample and surface properties at the liquid/solid interface. The relationship between acoustic energy transmission and the interfacial structure, viscosity, density and dielectric constant of the analyte is discussed. The FIA-TSM system provides a rapid, reproducible detection method with enhanced sensitivity and scope.
Sensor Piezoelectric crystal

"Cobalt-based Glassy-carbon Chemically Modified Electrode For Constant-potential Amperometric Detection Of Carbohydrates In Flow Injection Analysis And Liquid Chromatography"
Anal. Chim. Acta 1992 Volume 270, Issue 1 Pages 161-171
Tommaso R. I. Cataldi*, Innocenzo G. Casella, Elio Desimoni and Taddeo Rotunno

Abstract: The electrode was prepared by casting 50 mM Co(NO3)2 solution on a clean glassy C surface, drying the electrode at 60°C for 30 min and rinsing with water. X-ray photoelectron spectroscopy measurements indicated that Co(IV) was present on the electrode surface during the cyclic voltammetry of mono-, di- and tri-saccharides in alkaline medium. The electrodes were used as an amperometric detector for these carbohydrates after anion-exchange LC on a Carbopac PA1 column (25 cm x 4 mm), operated at 22°C, with 0.20 M NaOH as the mobile phase (1.0 mL min-1). The operating potential was 0.50 V vs. Ag - AgCl. The detectors were also used in a flow injection system for the detection of glucose in a 0.20 M NaOH carrier stream. The response was rectilinear over a dynamic range from 0.5 µM to 0.5 mM glucose. The average peak current was 2.23 µA and coefficient of variation (n = 14) was 1.6%. A cobalt-based glassy carbon (Co/GC) chemical modified electrode (CME) is described for use as an amperometric detector in the flow anal. of mono-, di- and trisaccharides. The preparation of the electrode is very easy and rapid. As with copper- and nickel-based glassy carbon electrodes, the Co/GC CME allows the electrocatalytic oxidation of scarcely electroactive compounds without recourse to pulsed waveform potentials. Hence, constant-potential amperometric detection is feasible and it has been applied successfully to reducing and nonreducing sugars. The chemical nature of cobalt species on glassy carbon was investigated using XPS and the results indicate that a Co(III) oxide hydroxide is present on the glassy carbon surface. However, electrochemical detection in an alkaline mobile phase of aliph. organic compounds seems to take place through mediation of Co(IV) species produced from the oxidation of Co(III) during anodic polarization. Carbohydrates and related polyhydroxy compounds were determined at the micromolar level with an operating potential of 0.50 V vs. Ag/AgCl after anion-exchange chromatography separation The detector responds linearly to an increase in glucose concentration with a linear dynamic range that extends over three orders of magnitude (0.5 µM-0.5 mM).
Carbohydrates Monosaccharides Disaccharides Trisaccharides Glucose Electrode Electrode Amperometry HPIC

"Characteristics Of Potassium Ion-doped Glass Slab Optical Waveguide As An Absorption Cell And Its Application To The Spectrophotometric Detection Of Methylene Blue"
Anal. Chim. Acta 1993 Volume 276, Issue 1 Pages 133-139
Kin-ichi Tsunoda*, Hiromitsu Itabashi and Hideo Akaiwa

Abstract: The characteristics of the K+-doped glass-slab optical waveguide are discussed in terms of effective path length and relative sensitivity. The waveguide was coated with octadecylsilane and used in the spectrophotometric detection of methylene blue (C. I. Basic Blue 9) by FIA. The coated waveguide could be used for the detection of methylene blue when an ion pair was formed with dodecyl sulfate.
Methylene blue Spectrophotometry

"Flow Injection Analysis Of Glucose At An Amperometric Glucose Sensor Based On Electrochemical Codeposition Of Palladium And Glucose Oxidase On A Glassy Carbon Electrode"
Anal. Chim. Acta 1993 Volume 278, Issue 1 Pages 17-23
Qijin Chi and Shaojun Dong*

Abstract: The amperometric glucose sensor is based on the detection of H2O2 produced by the enzymatic oxidation of glucose. The working electrode was prepared by potentiostatic codeposition of glucose oxidase and Pd at a potential of -0.9 V for 15 min onto a polished vitreous C electrode, coated with a thin layer of Nafion and used with a SCE reference and a Pt wire auxiliary electrode. At an operating potential of +0.3 V the calibration graph was rectilinear for 0.1-2.5 mM glucose. The response time and detection limit were 5 s and 50 µM, respectively. When the sensor was used in a flow injection system the optimum pH and flow rate were 7.2 and 0.7 ml/min, respectively. Under these conditions the response to glucose was rectilinear for 0.001-8 mM and the detection limit was 0.1 µM. The sensor did not respond to ascorbic or uric acids.
Glucose Amperometry Electrode Electrode Sensor

"Fumed-silica-containing Carbon-paste Dehydrogenase Biosensors"
Anal. Chim. Acta 1993 Volume 284, Issue 2 Pages 385-391
Joseph Wang* and Jie Liu

Abstract: Modified C-paste electrodes were prepared by mixing 20 mg of alcohol dehydrogenase (or 12 mg of L-lactate dehydrogenase) with 25 mg of NAD+, 120 mg of graphite powder and 80 mg of mineral oil. Re-hydrated fumed silica (particle size 7 nm, specific area 400 m2/g) was added (to 20%) and the resulting paste was packed into the end of a glass tube (3 mm i.d.), the inner end of which was connected to a Cu wire. Amperometric determination of 2 mM ethanol was performed at 0.8 V vs. Ag/AgCl in 0.05 M phosphate buffer of pH 7.4 using a Pt-wire auxiliary electrode. Silica modification produced a seven-fold enhancement in sensor response and a lowering of operating potential, without any loss in response time. Maximum enhancement was achieved with 15% silica and the detection limit was 0.08 mM ethanol; the electrode response decreased by 20% over one day. Silica modification also enhanced the sensitivity in the determination of 2 mM lactate. The calibration graphs for ethanol and lactate are shown. The electrode was also used in flow injection mode (1 ml/min flow rate); the calibration graphs are shown and the detection limits were ~0.1 mM ethanol or lactate.
Ethanol Lactate Electrode Electrode Amperometry Sensor

"Multi-site Detection In Flow Analysis. 3. Periodate Tubular Electrode With Low Inner Volume As A Relocatable Detector"
Anal. Chim. Acta 1994 Volume 285, Issue 3 Pages 293-299
Jos&eacute; A. Gomez Neto, Ana Rita A. Nogueira, H. Bergamin Filho and Elias A. G. Zagatto*, Jos&eacute; L. F. Costa Lima and Concei&ccedil;&atilde;o B. S. M. Montenegro

Abstract: The membrane sensor comprised 30% PVC, 63% o-nitrophenyl octyl ether and 7% tetra-octylammonium periodate, with an inner volume of 45 µL. Its position could be changed with use of an electronic commutator, to which were attached the working and Ag/AgCl reference electrodes. Two configurations are described. In one, used for the determination of glycerol, the sensor could be moved to either of two identical channels. Glycerol solution (30 µL) were injected into a reagent carrier of 3 mM NaIO4, 0.5 M Na2SO4, 0.1 M acetic acid and 0.1 M sodium acetate (0.5 ml/min). The carrier passed through a coiled reactor (1 m x 0.7 mm i.d.) to the sensor, where unconsumed periodate was measured. Calibration graphs were linear for 0.05-0.2% glycerol. The commutator was switched to the parallel channel a few s after the peak maximum was reached, thus the sampling rate of 100/h was not affected by the wash-out time. For sucrose, the sensor was moved to a position downstream in the same channel. Calibration graphs were linear for 0.1-0.5% sucrose. Glycerol was determined in soaps and detergents, and sucrose was determined in sugar cane juice and syrups.
Glycerol Sucrose Commercial product Juice Syrup Electrode Sensor

"Tubular Detectors For Flow Injection Potentiometric Determination Of Tetrafluoroborate In Electroplating Baths"
Anal. Chim. Acta 1994 Volume 293, Issue 1-2 Pages 35-41
A. N. Ara&uacute;jo, M. B. Etxebarria, J. L. F. C. Lima, M. C. B. S. M. Montenegro,* and R. P&eacute;rez Olmos

Abstract: A tubular detector for the determination of tetrafluoroborate was evaluated in a single line FIA system. The detector was described previously by Lapa et. al., (Il Farmaco, 1990, 45, 901), and consisted of an active PVC membrane containing immobilized tetra-octylammonia (as the ion exchanger) and 2-nitrophenyl octyl ether (as the mediator solvent.). The detector exhibited a linear response from 4 µM to 10 M tetrafluoroborate from pH 2.7-11.5 and the detection limit was 2.3 µM. The standard deviation (n = 22) of the analytical signal was 1 mV within the calibration range. The response time was short and enabled a sampling rate of 360/h and the detector life was 36 months. The detector was used in a high dispersion FIA system for the analysis of plating baths. The FIA system allowed a 7 µL volume of plating bath solution to be dispersed in a water carrier stream (8.5 ml/min). The resulting stream was merged with 33 mM sodium sulfate/10 µM-sodium tetrafluoroborate (0.45 ml/min) and passed through the detector cell. The response was linear for 1-6 M tetrafluoroborate. The mean recovery (n = 7) was 98.8% and a RSD of 1.9%.
Tetrafluoroborate Industrial Electrode Electrode Potentiometry

"A Fast, Highly Efficient, Continuous Degassing Device And Its Application To Oxygen Removal In Flow Injection Analysis With Amperometric Detection"
Anal. Chim. Acta 1994 Volume 298, Issue 3 Pages 393-399
Jairo J. Pedrotti, L&uacute;cio Angnes and Ivano G. R. Gutz

Abstract: A new continuous degassing device, based on the permeation of gases dissolved in a liquid through the walls of a narrow-bore polymeric tube, is described. The key innovation, responsible for the superior efficiency in relation to other designs, consists in maintaining a reduced pressure of an inert gas (N2, ~1600 Pascal) in the degassing chamber that contains the coiled polymeric tube wandered by the solution. When applied to the continuous removal of oxygen from an electrolyte in flow-injection analysis, FIA, with amperometric detection (flow of 1.0 ml/min, 34 s residence time), a decrease of at least 99.97% in the oxygen reduction current is experienced. Routine determination of 80 samples per hour of heavy metals like cadmium is afforded with a detection limit of about 10 ppb (1.8 x 10^-12 mol of Cd(II) for 20 µL injections), by using a sessile drop mercury electrode. FIA with pre-concentration followed by voltammetric stripping extends the detection limit to the sub-ppb level, as illustrated by monitoring lead and cadmium in samples of drinking water.
Amperometry

"Microbiosensor Based On An Integrated Thermopile"
Anal. Chim. Acta 1994 Volume 299, Issue 2 Pages 165-170
Bin Xie, Michael Mecklenburg, Bengt Danielsson, Ove &Ouml;hman and Fredrik Winquist

Abstract: A microbiosensor based on an integrated thermopile was designed and fabricated on a quartz chip. The thermopile, which was manufactured by doping boron in polysilicon together with aluminium, provided a potential output of ~2 mV/K. A silicone rubber membrane was used to form and seal the microchannel. The total column volume was 20 µL. Glucose oxidase and catalase were co-immobilized on spherical CPG beads (controlled pore glass) and in turn charged into the microchannel. Using 1 µL sample volumes, a linear range of 2 to 25 mM glucose was obtained using a flow rate of 105 µl/min. The relative standard deviation for 100 glucose samples (10 mM) was 5%.

"Flow-through Type Calcium Ion Selective Optodes Based On Novel Neutral Ionophores And A Lipophilic Anionic Dye"
Anal. Chim. Acta 1994 Volume 299, Issue 2 Pages 179-187
Hideaki Hisamoto, Kazuhiko Watanabe, Eriko Nakagawa, Dwi Siswanta, Yushi Shichi and Koji Suzuki

Abstract: Flow-through type calcium ion selective optodes based on novel neutral ionophores and a lipophilic anionic dye were developed. The novel calcium ion selective neutral ionophores designed and synthesized were double-armed diazacrown ether compounds possessing glycolic amides as the binding arms. Cation sensing material was prepared by coating pellicular-type ODS (octadecylsilica) beads with a lipophilic organic liquid which incorporates a novel neutral calcium ionophore and a lipophilic anionic dye of the diphenyl amine type. These beads were packed in a flow-through optical cell, and the Ca2+ measurement was performed to measure the absorbance change of the sensing beads at 516 nm. The best optode tested exhibited a good response to calcium ions in the concentration range from 10^-7 M to 10^-1 M with 0.05 M Tris-HCl of pH 7.0 as the flowing buffer solution. This optode showed excellent Ca2+ selectivity of over 10^-4 in selectivity coefficient values (ki,jopt.; I = primary ion (Ca2+); J = interfering ion) against Na+, K+ and Mg2+ which are primary interferents for human serum analysis. Sensor response theory, response time, selectivity, and application to the determination of calcium ion concentration in human serum were also discussed together with experimental results.
Calcium Electrode

"Thermo-optical Flow Injection Determination For Hydrogen Peroxide Based On An Enzymic Reaction Heat-induced Optical Beam Deflection"
Anal. Chim. Acta 1995 Volume 299, Issue 3 Pages 333-336
Xing-Zheng Wu*, Hiroaki Shindoh and Toshiyuki Hobo

Abstract: A reaction cell was fabricated from a 6 mm i.d. glass tube having a thin Au film carrying immobilized catalase mounted at one end. The cell was immersed in a CCl4 phase, having a water phase above to prevent evaporation, and a probe beam from a He-Ne laser at 632.8 nm was passed 1 mm from the Au film. Sodium phosphate buffer (0.01M) of pH 7.4 was pumped through the cell at 1.6 ml/min and H2O2 solution was introduced using a 40 µL injector. The heat of the decomposition reaction catalyzed by the enzyme induced a deflection in the probe beam which was measured by a knife-edge and a photodiode detection system. The immobilization of catalase by crosslinking with BSA was optimized to obtain a maximum deflection signal. This signal was linear over the concentration range 0.025-0.5 M of peroxide and the detection limit was 0.025M. The RSD for 0.5 M H2O2 solution (n = 20) was 0.93% and the enzyme activity was stable for at least two weeks.
Hydrogen peroxide Spectrometry

"Application Of The Glass Slab Optical Waveguide To The Spectrophotometric Determination Of The Iron(II)-1,10-phenanthroline Complex By Flow Analysis"
Anal. Chim. Acta 1995 Volume 299, Issue 3 Pages 327-332
Kin-ichi Tsunoda*, Hiromitsu Itabashi and Hideo Akaiwa

Abstract: An Fe(III) solution (25 ml, 0.04-0.32 mM), 1 mL of 10% hydroxylamine solution, 10 mL of 10% sodium acetate solution and 10 mL of 0.1% 1,10-phenanthroline (phen) solution were mixed, allowed to stand for 5 min and the mixture was diluted to 100 mL. A 0.5 mL portion of the color-developed [Fe(phen)3]2+ solution was introduced into a carrier stream of water and 0.2 mM sodium dodecylbenzene sulfate, and an ion pair was formed in a mixing coil. This was absorbed on a glass slab optical waveguide and caused the attenuation of light from a green He-Ne laser at 543.5 nm or an Ar ion laser at 488 and 515 nm. The fabrication of K+-doped and r.f.-sputtered glass slab optical waveguides is described. The waveguide made by r.f. sputtering of Corning 7059 glass and the Ar laser as light source gave the best sensitivity, which was 9.5 times higher than that obtained with a conventional spectrophotometer for a 0.5 mL sample.
Iron(2+) Spectrophotometry Sample preparation

"Electrochemical Characteristics Of Conductive Carbon Cement As Matrix For Chemically Modified Electrodes"
Anal. Chim. Acta 1995 Volume 300, Issue 1-3 Pages 5-14
Xinjian Huang, J. J. Pot and W. Th. Kok*

Abstract: Conductive carbon cement (CCC) was evaluated as matrix material for the preparation of electrodes bulk-modified with electrocatalysts. For pure CCC electrodes the background current characteristics were examined. In acidic or neutral phosphate buffers the useful electrode potential range was from -0.3 to + 1.0 V vs. SCE, while in 0.1 mol 1-1 NaOH it was from -0.3 to + 0.7 V. The electrochemical reversibility of CCC electrodes was examined by measuring the standard rate constants for the reduction of hexacyanoferrate (III) and the oxidation of hydroquinone, using cyclic voltammetry (CV) and rotating disk experiments. The reversibility of a CCC electrode was comparable with that of a freshly polished glassy carbon electrode and better than that of carbon paste electrodes. CCC was used as matrix for the preparation of electrodes bulk-modified with cuprous oxide and cobalt phthalocyanine (CoPC). With a Cu2O-CCC electrode the oxidation potential of glucose, which shows sluggish kinetics at unmodified carbon electrodes, was strongly reduced. The kinetics of the mediated glucose oxidation has been studied with a rotating disk electrode. It was shown that at glucose concentrations higher than approximately 1 mmol L-1 the electrochemical regeneration of the catalyst becomes rate-determining. The Cu2O-CCC modified electrode has been applied with a constant potential in flow-injection analysis for the determination of glucose. The long-term stability of the electrode was studied; repeated injections of a glucose solution during a period of 6 h yielded a relative standard deviation of the peak height of 1.8% (n = 57). In CV experiments the electrocatalytic activity of CoPC was shown for the oxidation of various compounds such as penicillamine, hydrazine and bile acids. Application of the CoPC-CCC electrode for the detection of bile acids in flow-through detection with a constant or pulsed potential failed, due to a rapid deactivation of the electrode.
Acids, bile Carbohydrates Hexacyanoferrate(II) Hydroquinone Electrode Electrode Voltammetry

"Aldose Dehydrogenase-modified Carbon Paste Electrodes As Amperometric Aldose Sensors"
Anal. Chim. Acta 1995 Volume 302, Issue 2-3 Pages 233-240
Maria Smolander*, Gy&ouml;rgy Marko-Varga and Lo Gorton

Abstract: A solution of aldose 1-dehydrogenase in 10 mM sodium acetate of pH 5 containing 0.1% of Triton X-100 was applied to the polished tip (diameter 1.7 mm) of a carbon paste electrode; results were less satisfactory when the enzyme was first mixed with the carbon paste. Incorporation of 2% (relative to graphite) of dimethylferrocene in the paste led to high catalytic response. The prepared electrode was coated with Eastman AQ-29D from aqueous 0.5% solution; this improved stability and minimized non-specific responses. Amperometric measurements with the electrode were made at +200 mV vs. Ag/AgCl (Pt counter electrode) in a flow injection system with 50 mM sodium phosphate buffer of pH 6.5 as carrier at 0.7 ml/min. Solutions of glucose and xylose standards and aldose samples were prepared in the same buffer. Xylose from a yeast fermenter was separated by LC on an Aminex HPX-87P column (30 cm x 7.8 mm i.d.) in Pb(II) form. The enzyme was active mainly towards the β-anomer of glucose. Response was linear up to 100 mM xylose and 10 mM glucose.
Aldoses Glucose Xylose Fermentation broth Sensor Amperometry Electrode Electrode

"Highly Selective Biosensing Of Lactate At Lactate Oxidase-containing Rhodium-dispersed Carbon-paste Electrodes"
Anal. Chim. Acta 1995 Volume 304, Issue 1 Pages 41-46
Joseph Wang*, Qiang Chen and Maria Pedrero

Abstract: A mixture of 2.5 mg lactate oxidase (40 iu), 1 mg polyethylenimine and 100 mg 5% rhodium-carbon/mineral oil (2:3) was packed into the 1 mm electrode cavity of a PTFE sleeve to form a lactate bioelectrode. The amperometric response was measured with three electrodes, a Ag/AgCl reference electrode and a Pt wire counter electrode and a supporting electrolyte of 0.05 M phosphate buffer pH 7.4. Calibration graphs were linear from -0.2 to 0.5 V and steady-state currents were produced in 8 s and ~e;2 min at -0.2 V and 0.0 V, respectively. The detection limit was ~e;15 µM-lactate. The bioelectrode was mounted in a flow injection system with 0.5 M phosphate buffer pH 7.4 as the carrier stream (0.5 ml/min) and an electrode potential of 0.0 V. The calibration graph was linear up to 2 mM lactate; RSD was 2.8% for 2 mM lactate (n = 60). The sample throughput was 60 samples/h.
Lactate Sensor Amperometry Electrode

"Electrochemical Detection With Microelectrodes In Capillary Flow Systems"
Anal. Chim. Acta 1995 Volume 305, Issue 1-3 Pages 114-120
Frank-Michael Matysik*, Antje Meister and Gerhard Werner

Abstract: A novel electrochemical cell for capillary electrophoresis with end-column amperometric detection is described. A platinum microdisk electrode (dPt = 25 m) facing the capillary outlet served as sensing electrode. The problem of interference of the high voltage electrical field with the microelectrode circuit has been solved by the construction of a glass sleeve/Nafion joint for 100 m i.d. capillaries. With 25 m i.d. capillaries end-column detection could be performed without the use of an electrical-field decoupler arrangement. The analytical performance of the detector was characterized applying capillary zone electrophoresis and micellar electrokinetic capillary chromatography to separate various ferrocene derivatives. In addition, the same detector cell configuration has been used for amperometric detection in conjunction with capillary flow injection analysis.
Ferrocene Electrophoresis Amperometry Electrode Electrode

"Development Of A Computer Controlled Multichannel Potentiostat For Applications With Flowing Solution Analysis"
Anal. Chim. Acta 1995 Volume 305, Issue 1-3 Pages 347-358
Tang Fang, Michael McGrath, Dermot Diamond* and Malcolm R. Smyth

Abstract: A 4-channel computer controlled potentiostat has been designed (expandable to 16 channels) for use with an amperometric array for analysis in flowing streams. The instrumentation developed to date has been used with both linear and radial flow cell configurations. Analogue and digital circuits for the independent control of 4 working electrodes have been fabricated, tested and integrated successfully to give an amperometric array. The design is based on the utilisation of common reference and counter electrodes to reduce the complexity of the electrode arrangement. Control of the purpose built instrumentation is effected with a 486-33 MHz personal computer and Analog Devices RTI815 and RTI817 data acquisition/control cards which are responsible for hardware control functions and data acquisition via digital and analogue control lines. Software for instrumentation control, data display (2- or 3-dimensional formats), on-line and post-run data processing and storage has been developed using the QuickBASIC software environment. The user interface utilises a Windows style display to achieve user friendliness with an on-line help facility. Data is stored in a spreadsheet compatible format (ASCII with ',' column delimiter) to facilitate post-run processing with standard applications packages such as Microsoft EXCEL. The system has been applied to the determination of well characterized electroactive compounds using flow-injection analysis. Linearity over the range 10^-2-10^-7 M has been obtained with a detection limit of 2 x 10^-7 M (S/N = 3.0) for potassium hexacyanoferrate(III). The simultaneous measurement of both oxidation and reduction flow injection currents of hexacyanoferrate(III) and hydroquinone is demonstrated.
Amperometry

"Use Of A Stopped-flow/T-format Spectrofluorimeter For Simultaneous Kinetic Analyses"
Anal. Chim. Acta 1995 Volume 310, Issue 3 Pages 453-459
B. Gala, A. G&oacute;mez-Hens and D. P&eacute;rez-Bendito*

Abstract: The potential of the joint use of a T-format spectrofluorimeter and the stopped-flow mixing technique in simultaneous kinetic determinations was studied. For this purpose, the direct resolution of a mixture of two analytes (neomycin and promethazine), by use of a condensation and an oxidation reaction that yield reaction products with similar maximum excitation wavelengths but different emission wavelengths was chosen. The determination was readily accomplished in a few seconds by simultaneously measuring the respective initial rates in the corresponding emission channels. Mixtures of neomycin and promethazine in ratios between 8:1 and 1:9 were thus satisfactorily resolved. The relative standard deviation was 1.0-1.8%. The proposed method was applied to the analysis of a commercially available pharmaceutical preparation, with a recovery of 99.3-102.0% for neomycin and 88.8-93.0% for promethazine.
Fluorescence

"A Flowing Electrolytic Hydride Generator For Continuous Sample Introduction In Atomic Spectrometry"
Anal. Chim. Acta 1995 Volume 316, Issue 2 Pages 129-144
Dennis M. Hueber and James D. Winefordner*

Abstract: Hydride generation is a useful technique for sample introduction in atomic spectrometry. Apparatus utilizing the chemical reduction of aqueous As, Se, Sb, Te and Pb are in common use and commercially available. An alternate method of hydride generation is electrolytic reduction. This method requires fewer reagents, reducing the potential risk of sample contamination. In this study, the construction and evaluation of a new flowing electrolytic hydride generator for sample introduction in atomic spectrometry is described. The effectiveness of several possible cathode materials and electrolytes is compared. Flame atomic absorption spectrometry was used to detect As, Se and Sb in aqueous solutions after conversion to AsH3, H2Se and SbH3. Sensitivity increases of 11-18 times over pneumatic solution nebulization were realized. Also, inductively coupled plasma atomic emission spectrometry (ICP-AES) was combined with this new type of hydride generator for the detection and quantitation of As and Se in aqueous solutions. Detection limits by ICP-AES were 0.7 µg/ml and 3 µg/ml for As and Se, respectively. In addition, the effects of several possible concomitants on the production of H2Se and AsH3 were examined.
Spectrophotometry

"Characterization And Application Of An Online Flow Injection Analysis/wall-jet Electrode System For Glucose Monitoring During Fermentation"
Anal. Chim. Acta 1995 Volume 317, Issue 1-3 Pages 223-232
Yu Liang Huanga, Titus J. Foellmera, Koon Chye Anga, Soo Beng Khoob,* and Miranda G. S. Yapa

Abstract: An online system for glucose monitoring during fermentation was developed. The system employed flow injection analysis coupled with a wall-jet electrode. Glucose was converted enzymatically in a tubular reactor packed with controlled pore glass beads containing immobilized glucose oxidase. The hydrogen peroxide produced was detected amperometrically. A filtration/sampling module operated by a peristaltic pump enabled sample withdrawal from the fermenter. The system was interfaced to a programmable language controller which was in turn linked to a microcomputer. The dual injection valve of the flow system was operated in a novel configuration to achieve sample dilution, by dispersion, and standardization simultaneously. The developed system was characterized for dilution factor, stability and linearity of response. After conditioning of the reactor, sample peak heights were found to have a precision of 1.07% (RSD, 25 determinations) when the glucose concentration was 1.32 g l-1. Under the conditions studied, linear response to glucose concentration from 0.062 to 4.0 g L-1 was obtained. Sample throughput was about 7 per hour. Interferences from the fermentation media were negligible after filtration through the sampling module and dilution. The online system was applied to glucose monitoring during E. coli fermentation. Good results were obtained as shown by the high cell density (OD6-00 nm = 168 in 9 h fermentation), constant specific growth rate (µ= 0.66) and lower acetate accumulation (less than 2 g L-1 when OD-600 nm was over 50). (18 References)
Glucose Fermentation broth Electrode

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

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

"Approaches To Inline Removal Of Dissolved Oxygen In Flow Systems For Process Analysis"
Anal. Chim. Acta 1996 Volume 332, Issue 1 Pages 31-38
Xin-Sheng Chai and Lars-G&ouml;ran Danielsson*

Abstract: Two methods were proposed for removing dissolved oxygen from analytical flow streams. Method A involved adding N2 at 10 ml/min to the liquid stream (1 ml/min) to form a two phase system which was separated by a gas-liquid separator. Method B involved passing the liquid stream through a 80 cm length of microporous PTFE tubing (1 mm i.d., Poreflon TB 21) immersed in a water bath at 100°C. The two methods were compared by a flow injection spectrophotometric method in which 5 µL 0.5 mM pyrogallol was injected into a 0.1 M NaOH stream when it emerged from the deoxygenation device. The absorbance was measured at 354 nm. Mixtures of 'oxygen free' 0.1 M NaOH (purged with N2) and air-saturated 0.1 M NaOH were used for calibration. The graph was linear for 0.009-8 mg O2/l. Both methods removed 98% of the oxygen originally present.
Pyrogallol Spectrophotometry

"Enzyme-modified Amperometric Sensors For Choline And Acetylcholine With Tetrathiafulvalene Tetracyanoquinodimethane As The Electron-transfer Mediator"
Anal. Chim. Acta 1997 Volume 341, Issue 1 Pages 43-51
Quan Xin and R. Mark Wightman*

Abstract: Amperometric biosensors for choline and acetylcholine were prepared by immobilizing choline oxidase and choline oxidase/acetylcholinesterase, respectively, over tetrathiafulvalene tetracyanoquinodimethane crystals packed into a cavity at the tip of a carbon-fiber electrode (16.5 µm radius). The immobilization matrix consisted of dialdehyde starch/glutaraldehyde, and the sensors were covered with an outer Nafion membrane. The amperometric performance of the sensors was studied with use of an FIA system, an applied potential of +100 mV vs. SCE (Pt-wire auxiliary electrode) and a carrier flow rate of 1 ml/min. The choline and acetylcholine biosensors exhibited linear responses up to 100 µM and 50 µM, respectively, and the response times were ~8.2 s. The choline biosensor was implanted into a rat-brain slice (400 µm thickness) immersed in Krebs buffer and used to monitor the diffusion of choline into the tissue.
Choline Acetylcholine Brain Amperometry Electrode Electrode Sensor Electrode

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

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

"Design And Development Of A Miniaturized Total Chemical-analysis System For Online Lactate And Glucose Monitoring In Biological Samples"
Anal. Chim. Acta 1997 Volume 346, Issue 3 Pages 341-349
Eithne Dempsey*, Dermot Diamond, Malcolm R. Smyth, Gerald Urban, Gerhard Jobst, Isabella Moser, Elisabeth M. J. Verpoorte, Andreas Manz, H. Michael Widmer, Kai Rabenstein and Rosemarie Freaney

Abstract: A miniaturised Total chemical Analysis System (µTAS) for glucose and lactate measurement in biological samples constructed based on an integrated microdialysis sampling and detection system. The complete system incorporates a microdialysis probe for intravascular monitoring in an ex vivo mini-shunt arrangement, and a silicon micromachined stack with incorporated miniaturised flow cell/sensor array. The prototype device has been developed based on state-of-the-art membrane and printed circuit board technology. The flow-through detection system is based on a three-dimensional flow circuit incorporating silicon chips with stacked micromachined channels. An integrated biosensor array (comprising enzyme sensors specific for glucose and lactate) is placed at the base of the stack allowing the detector to be incorporated within the µTAS assembly. These glucose and lactate biosensors are prepared using photolithographic techniques, with measurement based on the detection of hydrogen peroxide at glucose oxidase and lactate oxidase modified platinum electrodes. The resulting amperometric current (at 500 mV vs. Ag/AgCl) is proportional to the concentration of analyte in the sample. All instrumentation is under computer control and the complete unit allows continuous online monitoring of glucose and lactate, with fast stable signals over the relevant physiological range for both analytes. The microdialysis system provides 100% sampling efficiency. Sensor performance studies undertaken include optimization of sensitivity, linearity, operational stability, background current, storage stability and hydration time. The total system (sampling and detection) response time is of the order of 4 min, with sensor sensitivity 1-5 nA mM-1 for glucose and lactate over the range 0.1-35 and 0.05-15 mM, respectively. 17 References
Lactate Glucose Sensor Electrode Electrode

"Dual-enzyme Fiber Optic Biosensor For Pyruvate"
Anal. Chim. Acta 1997 Volume 350, Issue 1-2 Pages 59-65
Wen Zhang, Haidong Chang and Garry A. Rechnitz*

Abstract: In this study, the response characteristics for a dual-enzyme fiber-optic biosensor for pyruvate are presented. An enzyme layer composed of lactate oxidase and lactate dehydrogenase (LDH) was fabricated at the tip of a sensing optrode. The biosensor is based on the luminescence detection of consumed reduced nicotinamide adenine dinucleotide (NADH) and the measured fluorescence intensity is related to the bulk concentration of pyruvate. Such a dual-enzyme optrode can not only retain the merits of fiber-optic biosensors, but can also take advantage of two enzyme-catalyzed reactions. The response sensitivity and detection limit of the proposed dual-enzyme sensors are improved by at least 8 and 5 times, respectively, compared to those of single-enzyme systems. 21 References
Pyruvate Fluorescence Sensor Optrode

"Micro-continuous-flow System For Wet Chemical Analysis"
Anal. Chim. Acta 1997 Volume 354, Issue 1-3 Pages 35-42
Karin Carlssona, Hans S. Jacobsenb, Anders Lynggaard Jensenc, Theiss Stenstr&oslash;mb and Bo Karlberga,*

Abstract: A new continuous flow system based on controlled pumping of exact volumes of sample and reagents into a microbore manifold has been designed. The piston type pumps are made of Al2O3 ceramics and driven by a stepper motor with 48 steps per rotation. One pump per liquid (sample, reagents) is used. For each complete rotation a repeatable and exact volume in the range 3-4 µl is delivered. Samples are introduced sequentially into the system without being separated by any rinsing or conditioning carrier solution. The mixing channels in the manifold are zigzagged in order to promote secondary flow and thereby efficient mixing through inertial effects. Several types of dedicated manifold have been manufactured with volumes in the range 10^-30 µl. Optical measurement is made vertically against the flow direction using a light emitting diode as the light source. The detection volume is 0.25 µl. When a new sample is introduced into the system, a signal level typical for the analyte concentration in the sample is rapidly obtained. The detector signal oscillates because of the short and stepwise movement of the liquids in the system. The chemical reactions occurring while the liquids are stationary in the system give rise to a signal change thereby contributing significantly to thr: oscillation. Data evaluation can be based on the average of the signal or by merely utilising the signal obtained during a full turn of the pumps, The developed technique is not sensitive to changes in viscosity (density, salt content) between samples. A typical sample throughput can reach 45 h-1 and the total reagent consumption is about 40 µl per sample (two reagents).

"Response Function And Analytical Parameters Of Nitrite-selective Optode Membranes In Absorbance And Fluorescence Mode"
Anal. Chim. Acta 1997 Volume 355, Issue 2-3 Pages 259-268
Caspar Demuth and Ursula E. Spichiger*

Abstract: Four different nitrite-selective optode membranes were studied. Each membrane consisted of a nitrite-selective ligand and four different H+-selective chromoionophores dissolved in a plasticized poly(vinyl chloride) bulk medium. The membranes' analytical parameters differ with respect to optical spectra, dynamic range and detection limit. The unique features of each membrane are discussed and the versatility of the optical sensors based on the membranes is evaluated. The response functions of the optical sensors, derived from the changes in the absorbance and/or fluorescence of the membranes with varying nitrite concentration, are described by a theoretical model based on coextraction equilibria. The dynamic range of the sensors extended from 0.5 to 5000 mg L-1 nitrite with a detection limit of 0.24 mg L-1. The response time, 95, of the membranes placed in a continuous flow measuring cell was 1.2 min when changing from 0.5 mg L-1 nitrite to 0.05 mg L-1, and 3.6 min in the opposite direction. The selectivity coefficients determined by the separate solution method were: 10^-3.3 for nitrate, 10^-3.7 for chloride, 10^-3.0 for bromide, 10^-3.8 for sulphate, and 10^-5.0 for phosphate. Various applications of these optode membranes are discussed.
Nitrite Fluorescence Spectrophotometry

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

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

"A Transient Enzymic Inhibition As An Efficient Tool For The Discriminating Bioluminescent Analysis Of Three Adenylic Nucleotides With A Fiber-optic Sensor Based On A Compartmentalized Tri-enzymic Sensing Layer"
Anal. Chim. Acta 1998 Volume 360, Issue 1-3 Pages 89-99
P. E. Michel, S. M. Gautier-Sauvign&eacute; and L. J. Blum*

Abstract: A fiber-optic biosensor was developed for the specific and alternate determination of ATP, ADP and AMP. The sensing layer is arranged by compartmentalizing the tri-enzyme sequence adenylate kinase - creatine kinase - firefly luciferase. The two kinases are covalently co-immobilized on a collagen membrane, whereas firefly luciferase is bound alone on a sep. one. For the specific determination of each adenylic nucleotide, three particular reaction media are needed with which flow injection analysis can be performed in the 2.5-2500 pmol for ATP, 10^-2500 pmol for ADP and 25-5000 pmol for AMP linear ranges. For ten consecutive injections of 100 pmol ATP, 100 and 250 pmol ADP, the relative standard deviation were 3.5, 2.0 and 2.2%, respectively. When the three nucleotides are present simultaneously in the same sample, the transient inhibition of adenylate-kinase activity by adenosine 5'-monosulfate enables their specific and alternate measurement.
Bioluminescence Sensor

"Glucose Oxidase Polyion Complex-bilayer Membrane For Elimination Of Electroactive Interferents In Amperometric Glucose Sensor"
Anal. Chim. Acta 1998 Volume 364, Issue 1-3 Pages 173-179
Fumio Mizutani*, Yukari Sato, Yoshiki Hirata, Takahiro Sawaguchi and Soichi Yabuki

Abstract: An amperometric glucose-sensing electrode was prepared by immobilizing glucose oxidase (GOx) on a polyion complex membrane. First, a monolayer of 3-mercaptopropionic acid (MPA) was made on the surface of a gold electrode by immersing it in an ethanol solution containing MPA. Aqueous solutions of poly-L-lysine and poly-4-styrenesulfonate were successively placed on the electrode surface and allowed to dry. A GOx layer was then formed on the poly-L-lysine/poly-4-styrenesulfonate-complex layer by crosslinking the enzyme by the addition of a glutaraldehyde solution. The polyion complex layer was effective for eliminating electrochemical interferents such as L-ascorbic acid, uric acid and acetaminophen. whereas the hydrogen peroxide produced through the GOx-catalyzed reaction permeated rapidly through the layer. This resulted in a rapid response (100% response in <5 s) with a low interference level (e.g., the ratio of response for L-ascorbic acid to that for the same concentration of glucose was 0.07). The electrode was applied to the assay of glucose in beverages and sera, and could be used for more than two months,
Glucose Beverage Blood Serum Amperometry Electrode Electrode Electrode

"A Thermistor As A Sensor In Gas Phase Flow Injection Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 5-10
Shan-Jun Liu and Matthieu Tubino*

Abstract: A flow injection thermometric procedure based on a flow-through thermometric detector for measuring the heat effects of a phys. mixing or a chemical reaction is described. For comparison the following heat delivering systems were studied: mixing of water/water; air/water or air/air; neutralization reaction of sulfuric acid with sodium hydroxide; and gas phase reaction of carbon dioxide with ammonia in the presence of water vapor. Emphasis was given to the evaluation of the influence of the introduction of a small sample volume into the flow systems and the effect of flow rate on the signal and the sampling frequency.
Thermistor

"Development Of A Potentiometric Procedure For Determination Of Glycerol And 2,3-butanediol In Wine By Sequential Injection Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 193-199
Gilmara C. Lucaa, Boaventura F. Reisb,*, Elias A. G. Zagattob, Maria Concei&ccedil;&atilde;o B. S. M. Montenegroc, Alberto N. Ara&uacute;joc and Jos&eacute; Luis F. C. Limac

Abstract: A flow sequential injection procedure with potentiometric detection for determination of glycerol and 2,3-butanediol in wine is described. The method was based on reaction of IO-4 ions with glycerol and 2,3-butanediol with the reagent consumption afterwards being continuously monitored by means of a PVC periodate ion selective electrode constructed with tubular configuration and without inner reference solution. The electrode membrane was based on bis(triphenylphosphoranylidene) ammonium periodate dissolved in 2-nitrophenyloctyl ether and immobilized in PVC. In the developed set-up, a 2.0 x 10^-2 mol L-1 sodium periodate solution was used as carrier. To minimize interferences caused by other reducing components in the samples, a mini column packed with the anionic Amberlite IRA 400 (20-50 mesh, OH- form) resin was coupled to a lateral port of the valve. The feasibility of the anal. proposal was ascertained by determining polyols as glycerol in a set of red and white wine. The accuracy of the proposed method was assessed by standard addition samples with glycerol. Recoveries within the 96.0-106.9% range were calculated A sample throughput of 33 per h, a reagent consumption of 9.4 mg of sodium periodate per determination and a relative standard deviation of results lower than 1% were obtained.
Glycerol 2,3-Butanediol Wine Red Wine White Potentiometry Electrode Electrode Electrode

"Low-budget Flow Injection Device For Teaching. A $10 Six-port Valve"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 217-221
Olaf Elsholz*

Abstract: A novel sample introduction valve, based on the tubing clamp operation principle, is described for teaching flow injection analysis It was developed to overcome the shortage of instrumentation in elementary instruction courses in anal. chemical at Fachhochschule Hamburg. The materials for one valve, which can be easily build-up by the students, is <10.

"Time-division Multiplex Technique For Producing Concentration Profiles In Flow Analysis"
Anal. Chim. Acta 1998 Volume 368, Issue 1-2 Pages 105-111
Xue D. Wanga, Terence J. Cardwella, Robert W. Cattralla,*, Robert P. Dysonb and Graeme E. Jenkinsc

Abstract: A technique is described that uses computer-controlled solenoid valves for creating concentration. profiles for various flow-based methods of anal. These profiles can be quickly selected through software and, similarly, parameters such as the volume of the sample, carrier, and reagents can be set and altered when required, with minimal changes to the hardware. The technique has been demonstrated for flow titration and flow injection but is equally applicable to other methods. In all these methods, only a single channel pump is required to draw the mixed solutions through the detector, and individual solutions are introduced into the flowing stream by selection through solenoid-operated valves. Results are presented for the determination in water samples of calcium using potentiometric titration and orthophosphate by flow injection using the molybdenum blue method. The technique uses only small volumes of solutions and is fully automated and so is ideal for use in portable instrumentation.
Calcium Phosphate Environmental Potentiometry Spectrophotometry

"Effect Of Mobile Phase Composition On The Electrochemical Cell Conversion Efficiency In Electrochemistry/mass Spectrometry"
Anal. Chim. Acta 1998 Volume 369, Issue 3 Pages 253-262
Merle Regino, Carol Weston and Anna Brajter-Toth*

Abstract: A new electrochemical flow-through cell has been recently developed and characterized for online EC/MS experiments with thermospray and particle beam LC-MS interfaces. It was discovered in this work that the mobile phase composition had a significant effect on the sensitivity in the online EC experiments with the new flow-through electrochemical cell. An application of hydrodynamic EC methods is illustrated in the optimization of EC/MS measurements using different mobile phases including aqueous, non-aqueous, and mixed mobile phases.
Mass spectrometry Mass spectrometry Electrochemical analysis

"Flow Injection Potentiometric Determination Of Free Cadmium Ions With A Cadmium Ion-selective Electrode"
Anal. Chim. Acta 1998 Volume 370, Issue 2-3 Pages 267-278
Marek Trojanowicza,*, Peter W. Alexander, b and D. Brynn Hibbertc

Abstract: The determination of free Cd ions with solid-state Cd ion-selective electrode can be performed in non-flow measurements in non-buffered solutions in a wide concentration range down to pCd 10. In Cd ion buffered solutions linear Nernstian response was obtained even down to pCd 12, which is lower, that expected based on calculation of Cd solubility from the conditional solubility product. Interferences of trace amounts of Fe(III), Cu(II) and Pb(II) commonly present in natural waters in larger concentrations than Cd(II) can be eliminated by reduction with hydroxylamine, complexation with Neocuproine and ion-exchange on anion-exchange resin in sulfate form, respectively The developed procedure might be suitable for the determination of activity of free Cd ions in natural water. A preliminary study on this subject is demonstrated for river water sample using stopped-flow flow injection system.
Cadmium(2+) River Electrode Potentiometry

"Room Temperature Phosphorescence Flow-through Biosensing Of Anionic Surfactants"
Anal. Chim. Acta 1998 Volume 371, Issue 1 Pages 73-80
R. Bad&iacute;a and M. E. D&iacute;az Garc&iacute;a*

Abstract: The first flow-through biosensor for anionic surfactant determination based on a sensitive room temperature phosphorescence phase (Al-Ferron) coated with bovine serum albumin was prepared, characterized and applied to the determination of sodium dodecylbenzenesulfonate in standard aqueous solution and in spiked water samples (lake, river and spring). The optosensor response to sodium dodecylbenzenesulfonate was linear from 5 x 10^-6 M to 5 x 10^-4 M which is a suitable range for the detection of anionic surfactant concentrations in polluted natural waters. The sample anal. was rapid (90% of the total response is reached in <30 s), convenient (no-sample pretreatment) and did not require organic reagents which are harmful to the environment. This work demonstrates the anal. potential of surfactant-protein interactions as a biorecognition mechanism using suitable luminescence probes.
Surfactants, anionic Lake River Spring Phosphorescence Sensor

"Characterization And Analytical Use Of A Polypyrrole Electrode Containing Anti-human Serum Albumin"
Anal. Chim. Acta 1998 Volume 371, Issue 1 Pages 39-48
J. N. Barisci, D. Hughes, A. Minett and G. G. Wallace*

Abstract: The direct incorporation of anti-human serum albumin (AHSA) into a polypyrrole (PP) film by galvanostatic polymn. is a simple method for the preparation of an electrochemical sensor. However, the reproducibility of this approach is an area that requires attention. The amt. of antibody incorporated during polymer formation increases with increasing AHSA concentration. and decreasing c.d. Binding of human serum albumin (HSA) to the polymer-confined AHSA occurs readily, but is accompanied by a relatively large proportion of nonspecific interactions. The presence of phosphate ions hinders to a certain extent the PP/AHSA-HSA binding. Detection of HSA by flow injection analysis is possible using the PP/AHSA electrode operated under pulsed amperometric conditions in a NaNO3 carrier solution Pretreatment of the electrode with a bovine serum albumin solution decreases the response due to nonspecific binding.
Albumin Serum Human Amperometry Sensor Electrode Electrode

"Flow Injection Potentiometry By Poly(vinyl Chloride)-membrane Electrodes With Substituted Azacrown Ionophores For The Determination Of Lead(II) And Mercury(II) Ions"
Anal. Chim. Acta 1998 Volume 372, Issue 3 Pages 387-398
Xinhao Yang, D. Brynn Hibbert* and Peter W. Alexander

Abstract: A flow cell with a poly(vinyl chloride) (PVC) neutral-ionophore liq.-membrane ion-selective electrode was developed for flow injection potentiometry (FIP). The flow system was optimized and five substituted azacrown ethers: 7,16-dithenoyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTODC), 7,16-di-(2-thiopheneacetyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTAODC), 7,16-dithenyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTDC), 1,10-dioxa-4,7,13,16-tetraazacyclooctadecane (TC) and 4,7,13,16-tetrathenoyl-1,10-dioxa-4,7,13,16-tetraazacyclooctadecane (TTOTC) synthesized and studied as the ionophores in Pb2+ (DTAODC, TTOTC) and Hg2+ (DTDC, DTODC, TC, TTOTC) selective electrodes. The short contact times between analyte and ionophore in FIP allow the measurement of a strongly complexing ion such as Hg2+ that sats. the electrodes in batch anal., or in continuous-flow anal. that comes to a steady state. For the mercury-selective electrodes with ionophores with amide functional groups (TTOTC and DTODC) a carrier of 10 mM potassium nitrate increases the speed of response and recovery to baseline. The linear calibration range for a DTAODC lead-selective electrode was pPb = 2.0 to 5.0 with a slope of 32.5 mV decade-1 and for a TTOTC mercury-selective electrode, pHg = 3.0 to 5.5 with a slope of 28.4 mV decade-1. Highly reproducible measurements were obtained (relative standard deviation <2%) at a flow rate of 3.0 mL min-1 giving a typical throughput of 40 samples h-1 for Pb2+ and 30 samples h-1 for Hg2+.
Lead(2+) Mercury(II) Potentiometry Electrode Electrode Electrode Electrode

"Amperometric Peroxide Sensor Based On Horseradish Peroxidase And Toluidine Blue O-acrylamide Polymer In Carbon Paste"
Anal. Chim. Acta 1998 Volume 373, Issue 2-3 Pages 241-251
Vijay Rajendrana, Elisabeth Cs&ouml;regib, Yoshi Okamotoc and Lo Gortona,*

Abstract: An amperometric enzyme electrode for monitoring hydrogen peroxide (H2O2) was constructed by co-immobilizing periodate oxidized horseradish peroxidase (HRP) and a redox polymer containing a covalently bound phenothiazine type mediator, toluidine blue O (TBO), in a carbon paste matrix. Two different carbon paste electrodes were designed using either paraffin oil or solid paraffin wax as binders. A new mode of preparing enzyme modified carbon-wax composites is presented based on dissolving the wax in n-pentane before mixing with the enzyme modified carbon powder excluding the necessity of melting the wax prior to mixing. The developed sensors were used in a flow injection system at an applied potential of -50 mV vs. Ag/AgCl. Both electrode configurations displayed superior storage and operational stability, compared with similarly prepared electrodes containing only native HRP, where the electrical communication was based on a direct electron transfer between the electrode and HRP. Detection limits (calculated as twice the signal to noise ratio) of 50 nM H2O2 were obtained for these electrodes.
Hydrogen peroxide Electrode Electrode Electrode

"Electrochemical Metalization Of Carbon Electrodes"
Anal. Chim. Acta 1998 Volume 373, Issue 2-3 Pages 261-270
P. J. O'Connell, C. K. O'Sullivan and G. G. Guilbault

Abstract: Transition metals were electrodeposited on glassy carbon electrodes using cyclic voltammetry. The resultant chemical modified electrodes were amperometrically tested for catalytic activity towards the oxidation and reduction of hydrogen peroxide (H2O2). Their behavior was characterized by plotting current response to H2O2 vs. the applied potential. An unusual property found in the case of both ruthenium and rhodium was their capacity to reduce hydrogen peroxide atpositive potentials. This leads to the possibility of measuring large reduction currents at lowpositive potentials. Other electroactive species gave low responses at these potentials. The main problem encountered with such metalized electrodes is the lack of stability of their catalytic properties. The modified electrode with the greatest stability is a codeposited ruthenium and rhodium surface. After an initial drop-off in response, the electrodes remained stable for over two months. Twenty replicate injections gave a response of 0.63 µA to 1 mM H2O2 at an applied voltage of 67 mV vs. Ag/AgCl and the relative standard deviation was 0.78%. The 3s limit of detection is 5 x 10^-8 M hydrogen peroxide.
Hydrogen peroxide Electrode Amperometry

"Multicommutation In Flow Analysis Exploiting A Multizone Trapping Approach: Spectrophotometric Determination Of Boron In Plants"
Anal. Chim. Acta 1998 Volume 374, Issue 1 Pages 53-59
Cristiane de Azevedo Tumanga, Gilmara Caseri de Lucaa, Ridvan Nunes Fernandesb, Boaventura F. Reisc,* and Francisco J. Krugc

Abstract: A flow system based on multicommutation to implement a sequential zone trapping approach to retain multiple sample zone into the anal. path during a previous preset time interval is proposed. This permits an increase of the sample residence time to improve sensitivity of spectrophotometric methods based on a relatively slow reaction. The flow network comprises a set of solenoid valves assembled in order to form three anal. pathways with equal length. With this configuration three sample zones could be sequentially loaded and trapped into the reaction coils to allow the chemical reaction to reach completeness. The flow system was controlled by means of a 486 microcomputer equipped with an electronic interface running software written in Quick BASIC 4.5. Feasibility of the proposed system was ascertained by the spectrophotometric determination of boron in a mineralized plant material using Azomethine-H as chromogenic reagent. The proposed system showed a linear response from 0.25 to 6.00 mg B L-1 and an anal. throughput of 35 determinations per h. Other favorable features such as a low relative standard deviation of 2.5% (n=9) and a consumption of only 0.5 mg Azomethine-H per determination were also obtained.
Boron Plant Spectrophotometry Sample preparation

"Determination Of Choline-containing Phospholipids In Serum With A Fiber-optic Biosensor"
Anal. Chim. Acta 1998 Volume 374, Issue 1 Pages 19-29
M. D. Marazuela and M. C. Moreno-Bondi*

Abstract: An optical fiber biosensor for choline-containing phospholipids monitoring in serum samples is described. Phospholipids are hydrolyzed by the enzyme phospholipase-D to choline which is analyzed with a fiber-optic biosensor based on choline oxidase and oxygen transduction. Several supports have been evaluated for enzyme immobilization. The optimum biosensing layer consists of the enzyme immobilized on a nylon membrane and placed onto an oxygen sensitive layer formed by a luminescent Ru(II) complex, tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II), dispersed in a silicone membrane. The performance of the biosensor has been optimized using a flow injection system. The linear dynamic range of the biosensing membranes is found to be 0.08-3.00 mg mL-1 phosphatidylcholine. Studies of the reproducibility, stability and interferences of the device, as well as the application of the sensor to measurements in serum samples, are reported.
Choline Phospholipids Blood Serum Sensor Sensor

"Observations On A Dropping-mercury Electrochemical Detector For Flow Injection Analysis And HPLC"
Talanta 1981 Volume 28, Issue 4 Pages 251-254
Samuel J. Lyle and M. Idris Saleh

Abstract: An electrochemical detector cell having a dropping-mercury working electrode and an Ag/ AgCl reference electrode is examined with reference to applications in flow-injection analysis and high-performance liquid chromatography. The working electrode, fed by a horizontal capillary, is capable of delivering mercury at fast dropping rates which can be varied by a control device in the cell. Examples of application to inorganic and organic electroreducible species are considered and advantages and limitations relative to other electrochemical detector devices are discussed.
Electrode HPLC Polarography

"A Porous-jet Flow-through Electrode"
Talanta 1982 Volume 29, Issue 6 Pages 453-456
Joseph Wang* and Howard D. Dewald

Abstract: An electrochemical flow detector, based on a jet of solution directed at a thin porous carbon electrode, is described, along with its electrochemical characteristics and analytical applications. The electrode has a volume of 19 µL and surface area of 1.26 cm2. The detector exhibits better sensitivity and detectability than a wall-jet detector. Dopamine and ferrocyanide were used as test systems to give detection limits at nanomolar concentration levels. Applications indicated include continuous-flow analysis (utilizing stopped-flow voltammetry) and flow-injection analysis.
Dopamine Ferrocyanide Electrode Voltammetry

"Flow Injection Analysis In Clinical Chemistry"
Talanta 1984 Volume 31, Issue 10B Pages 879-888
Clifford Riley, Bernard F. Rocks and Roy A. Sherwood

Abstract: The application of classical flow injection analysis (f.i.a.), in which the sample is injected as a discrete portion, in clinical chemistry is critically assessed. Sampling valves employed are often inappropriate as relatively high proportions of sample are wasted. An improved alternative is described, based on precise aspiration of the sample via a probe. Applications of f.i.a. to clinical analyzes are discussed with particular reference to this modification and numerous data are presented for the analyzes of clinical specimens.
Clinical analysis

"A Timed Solenoid Injector For Flow Analysis"
Talanta 1985 Volume 32, Issue 5 Pages 431-433
S. D. Rothwell and A. A. Woolf

Abstract: A timed solenoid valve is described, which can be easily constructed from readily available components, and which can be adapted for more complicated flow regimes. Samples can be reproducibility injected into flowing streams by timed switching of a sample stream with a miniature solenoid valve and timer circuit. The device is simpler to assemble and use than the standard rotary valve for which it was shown, by direct comparison of calibration data for the determination of P, to be an adequate alternative.
Phosphate Water Spectrophotometry

"FORTH Package For Computer-controlled Flow Injection Analysis"
Talanta 1986 Volume 33, Issue 2 Pages 107-110
F. T. M. Dohmen and P. C. Thijssen*

Abstract: The automated flow injection system described comprises a computer-controlled sample changer, injection device and digital photometer, for use with an Apple II microcomputer. The software is understandable (program given), flexible and adaptable to other computers which use FORTH computer language. The automated flow injection system described comprises a computer-controlled sample changer, injection device and digital photometer, for use with an Apple II microcomputer. The software is understandable (program given), flexible and adaptable to other computers which use FORTH computer language.
Chloride Spectrophotometry

"Comparison Of Segmentors For Liquid-liquid Extraction Flow Injection Analysis"
Talanta 1990 Volume 37, Issue 12 Pages 1169-1173
V. Kub&aacute;, L. -G. Danielsson and F. Ingman

Abstract: The segmentation of two immiscible solvents in a continuous liquid - liquid extraction flow system was studied with a computer-controlled photometric detection system with a resolution time of ~3 ms. Classical T-piece segmentors made of poly(vinylidene fluoride), glass A4-T fitting and a modified glass A8-T fitting were compared. The fluoriplastic segmentor is inexpensive and readily available, but the A8-T fitting gives more reproducible segmentation.
Spectrophotometry Sample preparation

"Amperometric Enzyme Electrodes For The Determination Of L-glutamate"
Talanta 1991 Volume 38, Issue 1 Pages 49-56
Rhodora L. Villarta, David D. Cunningham, and George G. Guilbault

Abstract: Electrodes for amperometric measurement of L-glutamate were prepared by immobilization of L-glutamate oxidase on an Immobilon-AV Affinity membrane and attachment to an oxygen/hydrogen peroxide sensor. The response of the hydrogen peroxide sensor was linear over the concentration range 5.0 times 10^-8-5.0 times 10^-4 M L-glutamate, with a limit of detection of 35 nM. Attachment of a size-exclusion membrane (cut-off for molecular weight gt 100) or of a hydrophobic oxygen membrane eliminated electro-oxidizable interferences, but the response was attenuated by a factor of 2-3. The response may be amplified 10-fold by co-immobilizing L-glutamate dehydrogenase with the L-glutamate oxidase. The electrode initially lost 25% of its activity but was then stable for more than 320 days and at least 200 assays. The electrode was successfully used to assay glutamate in a protein tablet and in several food products. A flow injection system was assembled for the continuous assay of L-glutamate.
l-Glutamate Pharmaceutical Amperometry

"Determination Of Aqueous Ozone For Potable Water Treatment Applications By Chemiluminescence Flow Injection Analysis. A Feasibility Study"
Talanta 1992 Volume 39, Issue 6 Pages 593-598
Hyung-Keun Chung, Harvey S. Bellamy and Purnendu K. Dasgupta*,

Abstract: An inexpensive method of generating O3 at concentration. suitable for drinking-water sterilization is presented, together with the use of flow injection chemiluminescence analysis for selective determination of O3. The system comprised a multi-channel peristaltic pump, a dual-loop sample-injection value (electropneumatically actuated) and a laboratory-built flow-through reaction cell positioned in front of a photomultiplier tube. All tubing (0.5 mm diameter) was of PTFE. A number of fluorescing organic compounds was evaluated for the determination of aqueous O3. The limit of detection by using indigotrisulfonate was 2 µg l-1, but chromotropic acid, Rhodamine B (C. I. Basic Violet 10) and eosin Y may be more sensitive. The feasibility of determining aqueous O3 by chemiluminescence (CL) flow injection analysis was studied for application in potable water treatment. The ozonated water sample is injected into a pure water carrier and mixed with a dye reagent in front of a photodetector. Many reagents undergo fast CL reactions with aqueous ozone. Most of these reactions display considerable selectivity for O3 over other oxidants of importance in water treatment. Even when there is steady-state response to another oxidant, significant discrimination against the interferents is possible by taking advantage of the much faster kinetics of the CL reaction with O3. The design of an O3 generator and preparation of standard O3 solutions are described.
Ozone Water Chemiluminescence

"Application Of The Slotted Quartz Tube In Flow Injection Flame Atomic Absorption Spectrometry"
Talanta 1992 Volume 39, Issue 6 Pages 581-587
Shukun Xu, Lijing Sun and Zhaolun Fang

Abstract: The feasibility and performance of a combination of a slotted quartz tube and flow injection in flame AAS was studied. A five- to six-fold improvement in tube life was observed relative to continuous aspiration. Flow-impact systems were not needed, so that it was possible to achieve larger enhancement factors without loss of precision. Sensitivity enhancement factors of 3.1, 5.5, 5.3 and 4.0 were obtained for 1.0 mg L-1 of Cu, 1.0 mg L-1 of Pb, 0.1 mg L-1 of Cd and 1.0 mg L-1 of Au with coefficient of variation of 1.3, 1.1, 1.6 and 1.7%, respectively. When the method was applied to the determination of heavy metals in urine, improved tolerance to matrix interference was observed. Recoveries obtained by treating urine samples with 0.1 mg L-1 of Cu and Pb and 0.01 mg L-1 of Cd were 100 to 102%. The slotted quartz tube has been applied to flow injection flame atomic-absorption spectrometry (FI-FAAS) showing several important advantages. The tube life was improved by a factor of 5-6 compared to conventional continuous aspiration. Flow impact systems were found not to be necessary in the applications so that larger enhancement factors may be achieved without sacrifice in precision. For 1.0 mg/L copper, 1.0 mg/L lead, 0.1 mg/L cadmium, and 1.0 mg/L gold sensitivity enhancement factors of 3.1, 5.5, 5.3 and 4.0 were obtained with precisions of 1.3%, 1.1%, 1.6% and 1.7% RSD (n = 11), respectively. Application of the slotted quartz tube FI-FAAS method to the determination of heavy metals in urine has shown improved tolerance to interfering matrixes. Recoveries obtained by spiking undiluted urine samples with 0.1 mg/L copper and lead, and 0.01 mg/L cadmium were in the range 100-102%.
Copper Lead Urine Spectrophotometry

"Flow-cell Optosensor For Lead Based On Immobilized Dithizone"
Talanta 1992 Volume 39, Issue 11 Pages 1499-1503
Walace A. de Oliveira and Ramaier Narayanaswamy*

Abstract: Dithizone immobilized on XAD-4 resin was studied as the sensing element of an optical sensor for Pb using a flow-cell. Measurements were made using two different procedures. In 'kinetic analysis', the standard Pb solution was allowed to flow at a constant rate and the analytical signal was recorded as a function of time, whereas in the 'concentration procedure' only the initial and final values of reflectance were recorded, the light path being blocked during the addition of Pb solution and the regeneration of the reagent phase to avoid any photodegradation. Measurements were expressed as the relative reflectance, defined as the reflectance of the Pb complex minus that of the immobilized dithiozone alone. Lead in solution was determined from 0.3 to 10 µM with a detection limit of 10 nM. The sensor response was reproducible and could be regenerated using 10 mM HCl followed by citate - hydroxylamine solution The method may be applied in flow injection analysis and online analysis, and is suitable for most environmental analyzes, including drinking water.
Lead Water Sensor

"Atropinium Scopolaminum Integrated Microconduits In A Potentiometric Analytical System"
Talanta 1993 Volume 40, Issue 9 Pages 1445-1448
Cui Hongbo

Abstract: The preparation of the flow-through tubular atropinium and scopolaminum electrodes and assemblage of the integrated microconduit potentiometric analytical system with tubular ISEs, microvalve, manifold, electrostatic and pulse inhibitors are described. Electrochemical characteristics of new atropinium scopolaminum integrated microconduit FIA-ISEs were studied, The contents of atropine and scopolamine in drugs could be determined at almost equilibrium state at sampling rates of 120/hr. The standard deviation over the linear range was about 0.1 mV (N = 11). A FIA-ISE manifold for the determination of atropine and scopolamine in drugs is described based on flow-through tubular atropinium and scopolaminum electrodes. The tubular electrodes were prepared by replacing a small part of the wall of PVC tubing (0.5 mm i.d., 1.5 mm o.d.) with 0.25 mm2 of the corresponding sensor membrane (prepared from 1% atropimium-tetraphenylboron or scopolaminum-tetraphenylboron, 68% dibutyl phthalate, 31% PVC). The PVC tube was then mounted in a Perspex housing and surrounded with 0.1 M NaCl/10 mM atropinium or scopolaminum saturated with AgCl into which a Ag/AgCl wire was inserted. This tube acted as the detector and the potential was recorded vs. a Ag/AgCl placed in a side channel also fed by a stream of carrier solution of 0.05 M magnesium acetate. The flow-rate through the detector and reference channel are 1.2 and 0.24 ml/min, respectively. The response of the electrodes was linear for 0.02-100 mM for atropine and scopolamine with a response time of 15 sec and a sampling rate of ~120/h. The detection limits are 2 µM atropine and 4 µM scopolamine with recoveries of 98-102%.
Atropinium Scopolamine Pharmaceutical Potentiometry Electrode Electrode Electrode

"Electrocatalytic Oxidation And Flow Detection Of Cysteine At An Aquocobalamin Adsorbed Glassy Carbon Electrode"
Talanta 1995 Volume 42, Issue 7 Pages 885-890
Huimei Li, Tao Li and Erkang Wang*,

Abstract: The vitreous-carbon electrode was polished successively using 1, 0.3 and 0.05 µm alumina powder suspension, ultrasonicated several times and rinsed with water. The chemically modified electrode was prepared by applying 10 µL 1 mM aquocobalomin solution onto the dried electrode surface. The electrode was left to dry in air. Voltammetric experiments were performed using a saturated Ag/AgCl reference electrode and a Pt wire auxiliary electrode. The modified electrode catalyzed the electro-oxidation of cysteine, and the sulfhydryl oxidation occurred at 0.54-0.88 V vs. Ag/AgCl depending on pH value (3-10). When used as the sensing electrode in flow injection amperometric detection, the electrode permitted detection of cysteine at 0.8 V. the calibration graph was linear from 1.7 pM (detection limit) to 1.16 nM. The RSD (n = 10) was 4.2%.
Cysteine Amperometry Electrode

"Development Of An Amperometric Biosensor Based On Acetylcholine Esterase Covalently Bound To A New Support Material"
Talanta 1998 Volume 45, Issue 3 Pages 557-563
Masoud Khayyami, Maria Teresa P&eacute;rez Pita, Nuria Pe&ntilde;a Garcia, Gillis Johansson, Bengt Danielssona and Per-Olof Larsson*

Abstract: A new type of amperometric biosensor based on immobilized acetylcholine esterase was designed and constructed. The enzyme was immobilized on a flow-through working electrode, which was prepared from reticulated vitreous carbon (RVC) or from a composite material consisting of RVC and superporous agarose. The sensor was operated in FIA mode using acetylthiocholine as a substrate. The sensor responded to inhibitors such as paraoxon; 10^-9 mol was detected by the sensor in a non-optimized configuration. The practical lifetime of the sensor was at least 1 mo.
Pesticides Paraoxon Amperometry Sensor Electrode Electrode

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

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

"Flow Injection Analysis Of Potassium Using An All-solid-state Potassium-selective Electrode As A Detector"
Talanta 1998 Volume 46, Issue 6 Pages 1293-1297
Shinichi Komaba, Junko Arakawa, Michiko Seyama, Tetsuya Osaka*, Ikuo Satoh and Sadako Nakamura

Abstract: The concentration. of potassium was determined by a combination of flow injection analysis (FIA) with an all-solid-state potassium sensor detection. The all-solid-state potassium-selective electrode possessing long-term potential stability was fabricated by coating an electroactive polypyrrole/poly(4-styrenesulfonate) film electrode with a plasticized poly(vinyl chloride) membrane containing valinomycin. The simple FIA system developed in this lab. demonstrated sensitivity identical to that in the batch system and achieved considerably rapid assay (150 samples h-1). Analyses of soy sauce and control serum samples by this FIA system yielded results in good agreement with those obtained by conventional measurements.
Potassium Food Blood Serum Electrode Electrode

"Amperometric Detection With Microelectrodes In Flow Injection Analysis: Theoretical Aspects And Application In The Determination Of Nitrite In Saliva"
Talanta 1998 Volume 47, Issue 3 Pages 651-658
V&acirc;nia Mori and Mauro Bertotti*

Abstract: The construction of a wall-jet cell with amperometric detection using a set of disc electrodes whose radii ranged from 5 to 750 gm has been proposed. The influence of some experimental parameters like flow rate and electrode radius on hydrodynamic voltammograms recorded for a 0.5 mmol L-1 potassium ferrocyanide solution also containing 0.1 mol L-1 KCl has been discussed. Some considerations regarding the current signals obtained from flow injection experiments using both a 5- and a 750-µm radius platinum electrode were carried out in order to achieve the lowest limit of detection, a value of 0.03 µmol L-1 ferrocyanide being calculated by using the 5-µm radius microelectrode as amperometric detector. The wall-jet cell has been used in the determination of nitrite in saliva by quantifying the triiodide formed in the reaction of the analyte with excess iodide in acidic medium. A 12.5-µm platinum disk microelectrode maintained at + 0.2 V vs. Ag/AgCl was used as amperometric detector. Peaks obtained in diagrams after injection of diluted saliva to the carrier stream containing 0.1 mol L-1 sulfuric acid and 20 mmol L-1 potassium iodide were compared to an anal. curve obtained in the same conditions (τ2 = 0.997) for a nitrite concentration. in the range 1-10 µmol L-1. The concentration. of nitrite in the saliva sample after the appropriate correction for dilution was found to be 2.3 ppm (0.05 mmol L-1), in a good agreement with results obtained by using a standard spectrophotometric procedure (2.5 ppm). The limit of detection of the method was calculated as 0.2 µmol L-1, and the reproducibility was checked by measuring the peak current for 19 injections of 10 µM nitrite, the standard deviation being 3.7%.
Nitrite Saliva Amperometry Electrode Electrode

"Flow Injection Analysis Of Environmental Samples For Nitrate Using An Ion Selective Electrode"
Analyst 1977 Volume 102, Issue 1219 Pages 705-713
E. H. Hansen, Animesh K. Ghose and J. Ruzicka

Abstract: NO3- in soil extracts, wastewater, and fertilizer solutions was determined by addition of a pH 9.5 buffer of 10^-2 M Na tetraborate + 10^-2 M NaOH and measuring the peak max. value in a flow injection system with a NO3--selective electrode. Aqueous extracts of particulate NO3- in air were analyzed without pretreatment. The electrode consisted of tetraoctylammonium bromide in di-Bu phthalate and was calibrated at 10^-5 - 10^-2 M NO3-. For injection of 0.3 mL samples the anal. rate was 90 samples/h. The standard deviation was typically 0.2-0.5 mV, equivalent to 1-2%. The electrode lifetime was 2-3 months. A method is proposed for identifying and correcting for the presence of interferents by observing the shape of each peak and determining its negative elevation. Based on the flow injection principle and employing a nitrate electrode situated in a flow-through cell, a simple, reliable and sensitive method for the automated determination of nitrate and its use for analyzing soil extracts, waste waters, fertiliser solutions and air samples are described. At a sampling rate of 90 samples per hour a standard deviation of only 1-2% is typical. A new approach to identifying and correcting for the presence of interfering species in potentiometric measurements is discussed.
Nitrate Environmental Commercial product Geological Environmental Waste Electrode

"A Highly Sensitive Flow-through Phototransducer For Unsegmented Continuous-flow Analysis Demonstrating High-speed Spectrophotometry At The Ppb Level And A New Method Of Refractometric Determinations"
Analyst 1978 Volume 103, Issue 1230 Pages 897-908
D. Betteridge, E. L. Dagless, B. Fields and N. F. Graves

Abstract: A simple photometric detector is described which, because of the high stability of the light source, permits determinations of metal ions at the parts per 109 level with 4-(2-pyridylazo)resorcinol as the spectrophotometric reagent. By virtue of the design of the transducer it also functions as a refractometer capable of determinations of solutions of organic and inorganic compounds down to a lower limit of approximately 0.01%m/m. The theory of this function is discussed.A gallium phosphide light-emitting diode and a silicon phototransistor act as light source and sensor, respectively. The output current from the phototransistor is converted into voltage by the current to voltage converter described.The transducer is designed as a flow-through cell which, when used in conjunction with standard unsegmented continuous-flow apparatus, is capable of sampling rates of up to 300 per hour with a relative standard deviation of the result of 1.5%. At slower flow-rates, with a sampling rate of 160 per hour, the relative standard deviation is less than 1%.
Cobalt Copper Spectrophotometry Refractometry

"Determination Of Iron In Natural Waters And Plant Material With 1,10-phenanthroline By Flow Injection Analysis"
Analyst 1982 Volume 107, Issue 1275 Pages 659-663
J. Mortatti, F. J. Krug, L. C. R. Pessenda, E. A. G. Zagatto and S. Storgaard J&oslash;rgensen

Abstract: A flow injection analysis procedure for the determination of total iron in natural waters and plant digests by the 1,10-phenanthroline method is described. Effects of mixing-coil lengths, sample volume, flow-rates, reagent concentrations and interfering species were investigated. The proposed procedure allows the determination of iron concentrations in the range 0.1-30 ppm at a rate of up to 180 samples per hour with a relative standard deviation of lower than 1%. The results agree with those obtained by atomic absorption spectrometry, and an iron concentration identical with the certified value was found by analysis of an NBS standard reference material.
Iron Plant Environmental Spectrophotometry

"Online Diluter For Atomic Absorption Spectrophotometry"
Analyst 1982 Volume 107, Issue 1271 Pages 232-234
Michael H. Ramsey and Michael Thompson

Abstract: The short calibration range of atomic-absorption spectrophotometers and the widely varying sensitivities available for various elements tend to complicate the analysis of environmental materials. The complication stems from (a) the wide range of analyte concentrations found, which requires extra dilution for sporadic samples, and (b) the systematic dilution of every sample solution needed when combinations of certain elements are determined. For example, in the analysis of soils for cadmium and zinc, different dilutions are required for the two elements because of their very different abundances, and the absence of medium-sensitivity lines for zinc. These complications do not constitute a problem for small analytical loads. However, in long runs, and especially when automatic systems are employed, the retrospective replacement of out-of-range measurements and the use of two separate dilutions for different elements add substantially to the workload. There are a number of discrete dilution systems available commercially, although we are aware of no previous examples of an on-line continuous dilution system for atomic absorption. Here we describe an on-line diluter that can obviate manual intervention. If a test solution is found to have a concentration above the useful range the flow can be immediately diverted through the diluter to supply a fixed-ratio dilution to the nebuliser. The device described here is hand operated, but could readily be adapted to automatic control. The mixing chamber produces turbulent mixing with minimum flow resistance, which are the conditions required for this application.
Spectrophotometry

"Automated Viscometer Based On High-precision Flow Injection Analysis. 1. Apparatus For High-precision Flow, Injection Analysis"
Analyst 1983 Volume 108, Issue 1282 Pages 1-16
D. Betteridge, W. C. Cheng, E. L. Dagless, P. David, T. B. Goad, D. R. Deans, D. A. Newton and T. B. Pierce

Abstract: An automated viscometer was developed by modifying an Ostwald viscometer in which the sample (~50 µL) was injected into a carrier stream flowing along a narrow-bore tube. The time taken for the sample to travel a fixed distance was directly proportional to the viscosity. The measurement took ~30 s and gave a precision of 0.2 to 0.3% for viscosities ranging from 0.2 to 190 cP. The system could also be used for continuous monitoring of a carrier stream of unknown viscosity by injecting a sample of known viscosity. The use of refractometric, spectrophotometric, photometric, dielectric and conductometric detectors was evaluated and several microcomputer systems were investigated. The temperature had to be controlled to within 0.02°C
Conductometry Refractometry Spectrophotometry Viscosimetry

"Simple Wall-jet Cell Holding Either A Solid Electrode Or A Sessile Mercury-drop Electrode And An Illustration Of Its Use In The Oxidation And Reduction Flow Injection Voltammetric Determination Of Food Coloring Matters"
Analyst 1984 Volume 109, Issue 8 Pages 1029-1034
Arnold G. Fogg and Abdulhadi M. Summan

Abstract: The construction of a simple wall-jet detector cell, which can be used either with a solid electrode or with a sessile mercury-drop electrode, is described. The cell consists of two interlocking parts that hold separately the working electrode and the eluent inlet. The detector is used partly immersed in electrolyte solution to give contact with a counter and a reference electrode. Use of the cell is illustrated by determination of permitted synthetic food coloring matters at the 0.1 µg ml-1 level with both electrodes.
Food, coloring Electrochemical analysis Electrode Electrode Electrode Voltammetry

"Determination Of Nitrazepam And Flunitrazepam By Flow Injection Analysis Using A Voltammetric Detector"
Analyst 1987 Volume 112, Issue 5 Pages 697-699
Elisa Ruiz, Manuel Hern&aacute;ndez Blanco, Encarna Lorenzo Abad and Lucas Hern&aacute;ndez

Abstract: Sample solution (200 µL), containing 5.6 to 28.1 µg mL-1 of nitrazepam(I) or 6.3 to 31.3 µg mL-1 of flunitrazepam(II), was injected into a carrier stream of 0.1 M phosphate buffer (pH 7.0) containing 10% of methanol. I and II were determined by reduction at a vitreous-carbon electrode at -0.9 V vs. silver - AgCl - KCl. A reaction coil (70 cm x 0.5 mm) was incorporated before the detector. The flow rate was 4 mL min-1 and the sampling frequency was 100 h-1. The detection limits were 1.8 and 1.3 µg mL-1 for I and II, respectively. The procedure was used to determine 5 mg of I and 2 mg of II in tablets.
Nitrazepam Flunitrazepam Pharmaceutical Electrode Voltammetry

"Determination Of Ionic Surfactants By Flow Injection Pseudo Titration"
Analyst 1988 Volume 113, Issue 1 Pages 117-119
Chris J. Dowle, Brian G. Cooksey, (the late) John M. Ottaway and W. C. Campbell

Abstract: The construction is described of two flow-through surfactant-selective electrodes based on internally PVC-coated graphite tubes. The PVC coating contains 0.1% of tetrabutylammonium dodecyl sulfate for the cationic surfactant-selective electrode or 0.1% of hexadecyltrimethylammonium pentane-1-sulfonate for the anionic surfactant-selective electrode. The electrodes were incorporated in a flow injection system (described) for the titrimetric determination of surfactants (cf. Stewart and Rosenfield, Anal. Chem., 1982, 54, 2638). Optimum conditions were a flow rate of 0.9 mL min-1, a 70 µL injection volume and 1 µM-titrant (Na dodecyl sulfate or Hyamine 1622) as carrier stream. The lifetimes of the electrodes are of the order of 2 to 4 weeks. The precision of the method could be improved by elimination of manual peak-width measurement and spurious cell potential variations.
Surfactants, anionic Surfactants, cationic Electrode Electrode

"Platinum-dispersed Nafion-modified Glassy Carbon Electrode For The Determination Of Hydrogen Peroxide In A Flow Injection System"
Analyst 1988 Volume 113, Issue 4 Pages 617-620
Boon-Tat Tay, Kok-Peng Ang and Haritharan Gunasingham

Abstract: The cited electrode was prepared by electro-deposition of Pt particles into Nafion-coated vitreous carbon, by potential cycling between +0.7 and -0.15 V in acidic K2PtCl6 solution at a scan rate of 50 mV s-1. Compared with Pt, vitreous carbon and Pt-modified vitreous carbon electrodes, the Nafion - vitreous carbon system displayed increased stability. Linear-sweep voltammograms of 10 mM H2O2 in 0.1 M phosphate buffer (pH 7.4) at the various electrodes were obtained; at Pt loading levels 150 µg cm-2 the Pt - Nafion - vitreous carbon electrode showed a higher response than the Pt electrode. An application of the cited electrode to the flow injection analysis - electrochemical detection of H2O2 is described. Generally the rectilinear working range was from 1 µM to ~50 mM H2O2.
Hydrogen peroxide Electrode Voltammetry

"Oxidative Flow Injection Amperometric Determination Of Nitrite At An Electrochemically Pre-treated Glassy Carbon Electrode"
Analyst 1988 Volume 113, Issue 11 Pages 1723-1727
Antoine Y. Chamsi and Arnold G. Fogg

Abstract: The effects were studied of pre-treating the vitreous-carbon electrode online with H2SO4, phosphate buffer, KNO3 or Na2CO3 in a flow injection system for determination of NO2-. Pre-treatment of the electrode allowed determinations to be made at slightly less positive potentials and resulted in signals of max. height that were highly reproducible. Slightly better results were achieved with 0.1 M H2SO4, but 0.1 M phosphate buffer (pH 7) was preferred because of the low stability of NO2- in H2SO4. When the electrode was pre-treated anodically at +1.75 V for 5 min with phosphate buffer and the electrode was operated at +1.0 V vs. a SCE, response was rectilinear over several orders of magnitude and the detection limit was 3 ppb.
Nitrite Amperometry Electrode

"Chemically Immobilized Enzyme Electrodes For Hydrogen Peroxide Determination"
Analyst 1988 Volume 113, Issue 12 Pages 1811-1815
M. Cosgrove, G. J. Moody and J. D. R. Thomas

Abstract: The electrodes were prepared by immobilizing peroxidase(I) or catalase(II) on activated nylon by the method of Mascini et al. (Anal. Chim. Acta, 1983, 146, 135). The modified net was placed over a Pt electrode for I and O electrode for II. The I-immobilized electrode was applied in a flow injection system for determination of H2O2 in which sample solution (pH 7) was injected into a carrier stream (2.0 mL min-1) of 0.1 M phosphate buffer (pH 7) and 10 mM K4Fe(CN)6 and determined at -0.1 V vs. a Ag - AgCl reference electrode. The calibration graph was rectilinear from 5.25 µM to 1.75 mM H2O2. For 17.5 and 175 µM-H2O2, the coefficient of variation were 1% (n = 10). Several compounds at concentration. of 0.1%, e.g., ethanol, acetic acid and phenol did not interfere, but formaldehyde and ascorbic acid did. The II-immobilized electrode was applied in the dip-type mode to determine H2O2 in 0.1 M Tris buffer (pH 10). The calibration graph was rectilinear from 6.96 µM to 2.63 mM H2O2, and at 700 µM the coefficient of variation was 3% (n = 12). The storage and lifetime of the electrodes are discussed, and industrial and environmental applications are proposed.
Hydrogen peroxide Environmental Industrial Amperometry Electrode

"Platinum-dispersed Nafion-film-modified Glassy Carbon As An Electrocatalytic Surface For An Amperometric Glucose Enzyme Electrode"
Analyst 1989 Volume 114, Issue 6 Pages 695-698
Hari Gunasingham and Chee Beng Tan

Abstract: A Nafion film was coated on an electrochemically pre-treated vitreous-carbon electrode, and Pt particles were deposited on the film by potential cycling between +0.7 and -0.15 V. Glucose oxidase was subsequently immobilized on the electrode with use of bovine serum albumin and glutaraldehyde and covered with a polycarbonate membrane. The electrode was incorporated in a flow injection system containing a large-volume wall-jet detector with a Ag - AgCl reference electrode. The electrode exhibited better stability and selectivity than did a solid Pt electrode, and showed comparable sensitivity. The calibration graph was rectilinear up to 30 mM glucose. The electrode was applied to determine glucose in blood; results agreed with those obtained with a Boehringer Refolux monitor.
Glucose Blood Electrode Electrode Amperometry

"Metal-oxide-catalyst-membrane Electrodes For The Determination Of Hydrogen Peroxide"
Analyst 1989 Volume 114, Issue 12 Pages 1627-1632
Martin Cosgrove, G. J. Moody and J. D. R. Thomas

Abstract: Electrodes were prepared by entrapping MnO2, PbO2, Co2O3 or Ra2O3 on a Yellow Springs Instruments model 57390 electrode. Membranes were prepared containing the catalysts by membrane precipitation or by powder entrapment. That based on MnO2 was most sensitive (1 µM) at high pH in the dip mode. The calibration graph was slightly curvilinear from 1.75 µM to 5.28 mM H2O2 in 0.1 M Trisma buffer (pH 10). The response time was 30 s, and there was no change in response after 14 days. The electrode was used in a flow injection system.
Hydrogen peroxide Electrode

"Automated Flow Injection Measurement Of Photographic Dyes In Gelatin At Elevated Temperatures"
Analyst 1990 Volume 115, Issue 11 Pages 1407-1410
Richard H. Taylor, Gregory D. Clark, Jaromir Ruzicka and Gary D. Christian

Abstract: Photographic dyes in a gelatin matrix were determined by automated flow injection analysis, by using the split zone - gradient chamber dilution technique (Clark et al., Anal. Chem., 1989, 61, 1773), DMSO as carrier solvent and direct spectrophotometric detection (at 553 nm for a magenta dye and 459 nm for a yellow dye). The matrix was kept liquid by placing the apparatus in an incubator oven at 41°C to 44°C. With dilution times of 60 and 30 s for the magenta and yellow dyes, respectively, calibration graphs were rectilinear for 60 and 100 g l-1, respectively. The coefficient of variation was 2% for dilutions of 2000-fold. Results agreed to within 5% with those of a manual method.
Dyes, photographic Organic compound Spectrophotometry

"Direct Reductive Amperometric Determination Of Nitrate At A Copper Electrode Formed Insitu In A Capillary-fill Sensor Device"
Analyst 1991 Volume 116, Issue 6 Pages 573-579
Arnold G. Fogg, S. Paul Scullion, Tony E. Edmonds and Brian J. Birch

Abstract: A method has been developed for determining nitrate amperometrically by direct reduction at a freshly deposited copper electrode surface in a capillary-fill device (CFD). Copper(II) is added to the nitrate sample which is then taken up into the device. The potential of the screen-printed carbon electrode is held at -0.75 V versus the screen-printed silver reference electrode. At this potential, copper is plated onto the carbon electrode forming a freshly prepared copper electrode. At the same time dissolved oxygen is reduced. The potential is then scanned to more negative potentials and the signal at -0.90 V, due to the reduction of the nitrate, is measured. The method for determining nitrate given here is preliminary to the production of CFDs in which chemical reagents, copper sulphate and potassium hydrogen sulphate (used to produce the acidity), are screen-printed or otherwise coated onto the upper plate within the device.
Nitrate Amperometry Electrode Electrode Electrode Voltammetry Sensor

"High Performance Modular Spectrophotometric Flow Cell"
Analyst 1991 Volume 116, Issue 9 Pages 905-907
Jo&atilde;o Carlos de Andrade, Kenneth E. Collins and M&ocirc;nica Ferreira

Abstract: A high performance modular flow cell was developed which could be used in photometric or spectrophotometric detector systems for low-pressure LC, flow injection and similar techniques. The flow cell consisted of an inner absorption cell unit sandwiched between two rugged supports. A series of different flow cell volumes, pathlengths and fluid flow patterns could be obtained by replacing one inner piece with another. The cell used optical-fiber bundles to transmit the light beam to the optical path of the cell and then to the detector. Problems with gas bubbles were eliminated and rapid cell clearance was obtained. The performance of flow cells (1.5 mm i.d., optical path lengths of 5 mm and 10 mm) was tested by using a single-line flow injection manifold.
LC Spectrophotometry

"Flow Injection Amperometric Determination Of Nitrite At A Carbon Fiber Electrode Modified With The Polymer"
Analyst 1992 Volume 117, Issue 8 Pages 1259-1263
Michael M. Malone, Andrew P. Doherty, Malcolm R. Smyth and Johannes G. Vos

Abstract: The determination of NO2- in meat was carried out using a C-fiber micro-electrode modified by chemisorption (described) with the cited electrocatalytic polymer. Cyclic voltammetry in 0.1 M H2SO4 was used to optimize the coating procedure. At a detection potential of -0.15 V and an electrolyte flow-rate of 0.2 mL min-1, the calibration graph for NO2- standards was rectilinear from 0 to 400 µg mL-1 and the detection limit was 0.1 µg mL-1. The coefficient of variation was 2.2% for all concentration. examined (n = 20). The electrode had good long-term stability with no surface fouling. It was used to determine NO2- in extracts of processed ham (5 g), which were diluted with 0.2 M Na2SO4 (1:1) prior to injection of 20 µL portions. The results agreed with those using the spectrophotometric reference method. Ascorbic acid did not interfere and up to 30 samples h-1 could be handled. The development of C fiber electrodes modified with the polymer [Os(bipy)2(PVP)20Cl]Cl, where bipy = 2,2'-bipyridyl and PVP = poly(4-vinylpyridine, for the flow amperometric determination of nitrite is described. This Os polymer modifier greatly enhanced the kinetics of nitrite reduction compared with the reaction at bare C electrodes. Various electrode characteristics were optimized by using both cyclic voltammetry and flow injection. The calibration graph yielded a slope of 0.197 nA mL/µg over the linear range 0-400 µg/mL with a limit of detection of 0.1 µg/mL. The modified electrode had good short-term reproducibility, with a relative standard deviation of 2.15% (n = 20). After 3 wk of monitoring, involving 240 standard injections and 30 meat extract injections, the electrode continued to function with no significant change in sensitivity. The electrode was used to analyze a processed meat sample for nitrite content, and the results compared favorably with those obtained with a standar reference spectrophotometric method. Even a 10-fold excess of ascorbic acid did not interfere in nitrite determination.
Nitrite Meat Amperometry Electrode Electrode

"Inverted Poly(vinyl Chloride)-liquid Membrane Ion-selective Electrodes For High-speed Batch-injection Potentiometric Analysis"
Analyst 1993 Volume 118, Issue 9 Pages 1131-1135
Jianmin Lu, Qiang Chen, Dermot Diamond and Joseph Wang

Abstract: Sodium and potassium ISE based on the ionophores valinomycin and tetramethyl-p-t-butylcalix[4]arene tetra-acetate immobilized in a PVC membrane were fabricated for use in an inverted configuration for batch injection. Injections (usually 100 µL) were made using a micro-pipette placed 2 mm from the ISE membrane; 0.1 M LiCl was used as an ionic strength adjustment buffer. Two Ag/AgCl reference electrodes were used for potentiometric measurements. Amperometric measurements were made using a BAS vitreous carbon electrode with a Pt wire auxiliary electrode and a Ag/AgCl reference electrode. All the amperometric measurements were obtained using a working electrode potential of +0.8 V vs. the Ag/AgCl reference electrode. The calibration graph was linear from 10^-4.5-0.1 M NaCl. The limit of detection was 10 µM-Na+. Peak shapes obtained under fast and zero stirring conditions were contrasted with those obtained using flow injection. The method was applied to the determination of sodium in mineral water samples.
Sodium Mineral Potentiometry Electrode Electrode Electrode Electrode Amperometry

"Electrocatalytic Oxidation And Flow Injection Determination Of Reduced Nicotinamide Coenzyme At A Glassy Carbon Electrode Modified By A Polymer Thin Film"
Analyst 1994 Volume 119, Issue 5 Pages 1063-1066
Quijin Chi and Shaojun Dong

Abstract: The cited modified electrode was prepared by electrochemical copolymerization of pyrrole and Methylene Blue (MB; Basic Blue 9) on to a vitreous carbon electrode using cyclic voltammetry in a solution (bubbled with N2) containing 0.5 mM of MB and 1 mM of pyrrole. The resulting modified electrode was incorporated in a flow injection system (diagram given) and used for the determination of NADPH and NADH. A solution of NADPH or NADH (10 µL) was injected into a carrier stream (0.6 ml/min) of 0.1 M phosphate buffer of pH 6 and the analyte was detected by the pyrrole/MB modified electrode at an applied potential of +0.25 V vs. SCE. Calibration graphs were linear over 4 orders of magnitude for both NADPH and NADH. The detection limits were 25 and 40 nM for NADPH and NADH, respectively. The RSD (n = 15) for 1 mM of NADPH was 2.7%. The electrode response was stable for over 20 h.
Nicotinamide adenine dinucleotide reduced Nicotinamide adenine dinucleotide phosphate reduced Electrode Electrode Electrode

"Evaluation Of A Split-type Flow Cell For A Polarized Spectrophotometric Detector"
Analyst 1995 Volume 120, Issue 4 Pages 1137-1139
Atsushi Yamamoto, Akinobu Matsunaga, Eiichi Mizukami, Kazuichi Hayakawa, Motoichi Miyazaki, Masayuki Nishimura, Mitsuo Kitaoka and Tomio Fujita

Abstract: A split-type flow cell for a polarized spectrophotometric detector (PPD), in which the column effluent is simultaneously passed through both the sample and reference sides, is described. The improvement in detection sensitivity in PPD with the use of this cell is discussed. Its utility as a universal polarimetric detector for HPLC for the detection of colored amino acid-copper(II) complexes is shown. A new possibility for this cell in the gradient elution separation of glucose syrup is demonstrated.
HPLC Polarimetry Spectrophotometry

"Automatic Determination Of Optimum Dilution Levels For Laser-enhanced Ionization Detection Of Matrix-interfered Sample By Flow Injection"
Analyst 1995 Volume 120, Issue 10 Pages 2593-2599
Shau-Chun Wang and King-Chuen Lin

Abstract: A flow injection (FI) system was interfaced to a laser-enhanced ionization (LEI) apparatus in order to reduce electrical interference in the latter. The technique involved the injection of a water plug into a carrier stream of the sample solution. The concentration gradient generated significantly reduced the electrical interference induced by the sample matrix and enabled a LEI signal to be obtained for the analyte. The use of FI also allowed the automatic determination of the optimum dilution levels for maximum LEI signal enhancement. The theoretical basis of the FI-LEI technique was also studied. Equations were derived that enabled the relative intensity of the FI-LEI signal, as a function of the sample matrix concentration, to be predicted. The method was illustreated with the detection of 4 ppm In in a solution containing an Na-matrix concentration greater than the threshold level (4-10 ppm under optimum conditions) at which no conventional LEI signal is detectable.
Indium Spectrometry

"Development And Operating Characteristics Of Micro-flow Injection Analysis Systems Based On Electro-osmotic Flow. A Review"
Analyst 1997 Volume 122, Issue 1 Pages 1R-10R
S. J. Haswell

Abstract: A review is presented of the concepts and methodologies involved in the development of micro-FIA systems based on electro-osmotic flow. Aspects considered include the fabrication of such systems and also pump, injector, reactor and detector design. (98 references).

"Microfabricated Flow Chamber For Fluorescence-based Chemistries And Stopped-flow Injection Cytometry"
Analyst 1997 Volume 122, Issue 9 Pages 883-887
Peter S. Hodder, Gert Blankenstein and Jaromir Ruzick

Abstract: A microfabricated flow chamber (MFC) suitable for performing liquid- based fluorimetric assays is introduced. Precision delivery of microliter volumes of sample and reagent to the MFC is accomplished by a double-syringe-pump flow injection analysis (FIA) apparatus. The FIA- MFC system also combines the 'sheath flow' technique (traditionally used in flow cytometry) and stopped-flow FIA as a way to allow sample and reagent streams to be mixed reproducibly. The applicability of this FIA-MFC system to bioanalytical assays is demonstrated by performing an enzymatic assay with an artificial fluorigenic substrate to determine the activity of Savinase, a proteolytic enzyme. When coupled to a fluorescence microscope platform, quantitative analysis of the reaction product is possible. Experiments showed that the FIA-MFC system was capable of performing the assay with good reproducibility of injection (1.5%), and linearity of response (r2 = 0.9997) in activity ranges of analytical interest. Owing to the incorporation of flow cytometry sheath flow principles into an FIA format, the FIA-MFC system is a suitable tool for cytometric studies.
Enzyme, savinase Fluorescence Flow cytometry

"Surface Enhanced Raman Spectroscopy As A Molecular Specific Detection System In Aqueous Flow-through Systems"
Analyst 1998 Volume 123, Issue 5 Pages 1057-1060
N. Wei&szlig;enbacher, B. Lendl, J. Frank, H. D. Wanzenb&ouml;ck and R. Kellner

Abstract: Surface enhanced Raman scattering (SERS) is proposed as a mol. specific technique for direct measurements of organic molecules in aqueous solutions An FT-Raman spectrometer was interfaced with a flow injection manifold operated in the stopped-flow mode enabling reproducible collection of SERS spectra due to the automation of the anal. procedure. For SERS a solid state substrate placed in a newly developed flow-cell was used. Multiple measurements on one single SERS substrate were achieved by rinsing the substrate with reagents such as 3 M KCl or 0.1 M NaOH solutions prior to the next measurements to remove retained analytes from the surface of the SERS substrate. This procedure allowed for improved precision as compared with a conventional batch approach. Quant. aspects were studied by establishing a calibration curve for nicotinic acid which was used as a model analyte. A linear dependence of the recorded SERS intensities from the logarithm of the analyte concentration. was obtained throughout the whole studied concentration. range (0.001-0.1 M, correlation coefficient r2 = 0.97). The standard deviation of the method sx0 is 0.122 mM and detection limit 1.7 mM, respectively. The results demonstrate the potential of SERS spectroscopy to be used as a molecular specific detector in aqueous flow systems such as flow injection anal.
Nicotinic acid Raman Raman

"Electrooxidation Of Thiocyanate On Copper-modified Gold Electrode And Its Amperometric Determination By Ion Chromatography"
Analyst 1998 Volume 123, Issue 6 Pages 1359-1363
Innocenzo G. Casella*, Maria R. Guascito and Giuseppe E. De Benedetto

Abstract: Cyclic voltammetry was used to study the electrochemical behavior of an Au/Cu electrode towards the electrooxidn. of thiocyanate ion in alkaline medium. The effects of pH, Cu loading, scan rate and applied potential on the electrocatalytic oxidation of thiocyanate were studied. Flow injection experiments and ion-chromatography (IC) were performed to characterize the electrode as an amperometric sensor for the thiocyanate determination The effects of carbonate concentration. and common interferents on the retention time were also estimated. The electrode stability, precision, limit of detection and linear range were evaluated at a constant applied potential of 0.7 V vs. Ag/AgCl. Calibration plots, obtained in IC, were linear from 1.0 to 195 µM (correlation coefficient of 0.9984). The detection limit (LOD) was 0.5 µM (29 ppb) in a 50 µL injection. An example of anal. application, which includes the IC separation and detection of thiocyanate ion present in human urine, is given.
Thiocyanate ion Urine Electrode Voltammetry HPIC Amperometry

"Novel Polypyrrole Based All-solid-state Potassium-selective Microelectrodes"
Analyst 1998 Volume 123, Issue 6 Pages 1339-1344
R&oacute;bert E. Gyurcs&aacute;nyi, Ann-Sofi Nyb&auml;ck, Kl&aacute;ra T&oacute;th, G&eacute;za Nagy and Ari Ivaska

Abstract: Potassium-selective potentiometric microelectrodes with a polypyrrole solid internal contact were fabricated by the application of a K-selective bis-crown ether ligand based, plasticized poly(vinyl chloride) (PVC) membrane to the surface of conducting polymer modified Pt, Au or C µdisk electrodes. The selectivity and sensitivity of the new type of potentiometric K microelectrode are comparable with those of the conventional macro ion-selective electrodes and of the micropipet type microelectrodes based on the same ionophore. The ease of preparation and robustness are the main advantages of this new electrode design, which can replace the classical micropipet type microelectrodes in many applications. The microelectrodes showed good dynamic characteristics and were used successfully in a wall-jet cell incorporated flow injection analysis system and as a measuring tip in scanning electrochemical microscopy. The polypyrrole modified substrate electrodes can be made selective for different ions just by changing the ionophore in the plasticized PVC membrane, which can extend their use to a wide range of applications.
Potassium Electrode Electrode Electrode Potentiometry

"Flow Injection Potentiometric Determination Of Phosphate In Waste Waters And Fertilizers Using A Cobalt Wire Ion-selective Electrode"
Analyst 1998 Volume 123, Issue 7 Pages 1635-1640
Roland De Marco, Bobby Pejcic and Zuliang Chen

Abstract: Flow injection potentiometric (FIP) determinations of dihydrogen phosphate (H2PO4-) in fertilizers and waste waters were undertaken using a cobalt wire phosphate ion selective electrode (ISE). The Co wire electrode was used in the FIP determination of phosphate in a carrier containing 4 x 10^-2 mol L-1 potassium hydrogen phthalate (KHP) at pH 5. The FIP technique was validated for fertilizer and waste water samples against standard spectrophotometric methods of anal. FIP is a highly selective and accurate technique for the determination of phosphate in fertilizers [i.e., the FIP and spectrophotometric data compare to within a few percent (relative)]. A significant chloride interference occurs in waste water samples; however, this problem can be eradicated by using the chloride selectivity coefficient, chloride concentrations determined independently using ion-selective electrode potentiometry. The discrepancy between correlated FIP and spectrophotometric data for phosphate in waste waters is generally ±5% (relative). X-ray photoelectron spectroscopic and electrochemical impedance spectroscopic (EIS) results suggest that the Co oxide surface film of the electrode is dissolved in phosphate media, facilitating the corrosion process that regulates the response of the Co wire electrode. The EIS response of the Co wire electrode is dependent on both the pH and phosphate content of the solution A charge-transfer reaction mechanism, and accompanying Nernst equation, probably explain the phosphate response of the Co wire electrode.
Phosphate Waste Commercial product Electrode Electrode Potentiometry

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

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

"Performance Of A Modular Thermospray Interface For Signal Enhancement In Flame Atomic Absorption Spectrometry Coupled Online To Flow Injection [analysis] Or Liquid Chromatography"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 4 Pages 659-664
Erik H. Larsen and Jean-Simon Blais

Abstract: A simple and inexpensive thermospray interface is described that was connected to a flame AAS system without modification of the nebulizer and burner assembly. Details are provided of its construction and performance characteristics. The interface provided improved signal-noise and signal enhancement in a flow injection - AAS system with rectilinear calibration and detection limits of 1.9 ng of Cd, 8.5 ng of Cu and 27 ng of Pb. The use of the interface to couple HPLC to AAS was demonstrated for the determination of metallothioneins in biological samples.
Cadmium Copper Lead Biological Spectrophotometry

"Examination Of Separation Efficiencies Of Mercury Vapor For Different Gas - Liquid Separators In Flow Injection Cold Vapor Atomic Absorption Spectrometry With Amalgam Preconcentration"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 4 Pages 585-590
C. P. Hanna, P. E. Haigh, J. F. Tyson and S. McIntosh

Abstract: Three designs of gas - liquid separator were compared in a flow injection (FI) manifold for the determination of Hg by cold vapor AAS. In each case, the manifold device was optimized for max. sensitivity by studying the effects of reagent flow rate, Ar purge flow rate, injection time and post-injection purge time. A significant difference was found between the performance (in terms of peak height and integrated signal sensitivity) of a miniature design and two larger designs, though no difference in precision was observed. For the miniature design, no differences were found in peak height sensitivity using Sn(II) or tetrahydroborate reductants, but for the latter reductant the integrated signal sensitivity was 36% lower. Efficiency of separation was measured by comparison of the signal from a known mass of Hg vapor with the signal from a known mass of Hg in solution, and found to be 101 ± 4% and 103 ± 6%, respectively, for peak height and integrated signal.
Mercury Spectrophotometry

"Continuous Determination Of Ascorbic Acid By Photobleaching Of Methylene Blue"
Anal. Chem. 1972 Volume 44, Issue 7 Pages 1267-1269
Vance R. White and J. M. Fitzgerald

Abstract: An apparatus for the determination of ascorbic acid, via the photobleaching of the methylene blue carrier stream, was discussed and the appropriate diagram presented. The signal was measured by an Atomic Absorption (AA) spectrophotometer and a major advantage to the system is its ability to regenerate the methylene blue carrier stream via the oxidation of methylene blue by diatomic oxygen. Day to day reproducibility was very good and a discussion of interferences (mostly from aromatic components) is presented along with a table outlining the various interference levels. A discussion of the results for the analysis of orange juice, water, and vitamin C tablets are presented.
Ascorbic acid Water Juice Pharmaceutical Spectrophotometry

"Kinetic Study Of The Fluoride Electrode In Fast Flow And Automatic Systems"
Anal. Chem. 1976 Volume 48, Issue 2 Pages 272-277
John Mertens, Pierre Van den Winkel, and Desire L. Massart

Abstract: The kinetics of the fluoride [16984-48-8] ion-sensitive electrode were investigated by the fast flow injection method and in systems for automatic anal. The kinetics observed in injection experiments do not fit in with the equations proposed by Rechnitz, Johansson, and Pungor for glass and some other ion-selective electrodes. When t90 (time to reach 90% of equilibrium. potential) is ≤2 sec, a hyperbolic relation is observed No simple equation is able to describe the response when it is slower. There is a discrepancy between the dynamic responses measured in the injection method and that observed in auto-analyzers. It is proposed that the rate-limiting step in the latter case is film diffusion. The slowing-down effect can be considerably decreased by using internally stirred electrode cells. Responses allowing sample rates up to 60/hr can then be expected. With a discontinuous system, in which very high flow rates are applied, sample rates of 100/hr are possible.
Fluoride Electrode

"Sub-microliter Flow-through Cuvette For Fluorescence Monitoring Of High Performance Liquid Chromatographic Effluents"
Anal. Chem. 1979 Volume 51, Issue 9 Pages 1444-1446
L. W. Hershberger, J. B. Callis, and G. D. Christian

Abstract: A new sub µL flow-through cuvette suitable for monitoring liquid chromatographic effluents has been developed and tested. The cuvette is based on the sheath flow principle, in which the chromatographic effluent is injected into the center of an ensheathing solvent stream but does not mix with it because laminar flow conditions are maintained. The optical volume of the cuvette is easily varied by adjusting the relative flow rates of sheath and sample. The cuvette has been tested for stability, reproducibility, and dynamic range using porphyrins as test compounds. The detection limit for mesoporphyrin IX dimethyl ester was 8 X lo-'' M when the cuvette was operated with an effective detection volume of 53 nL.
Mesoporphyrin IX dimethyl ester HPLC Fluorescence

"Symmetrical Two-electrode Pulsed-flow Detector For Liquid Chromatography"
Anal. Chem. 1981 Volume 53, Issue 1 Pages 78-80
J. Blaedel and Joseph Wang

Abstract: An electrochemical flow detector with two carbon electrodes in a thin-layer configuration is described. The elimination of the conventional reference electrode results in minimal potential (IR) drop and very simple design. The cell is evaluated for amperometric measurements by using the sensitive pulsed-flow technique. Well-defined current-potential curves are obtainable. The low pulsed-flow background current permits measurements at the nanomolar concentration level. Applications are indicated for continuous flow analysis, liquid chromatography, and flow injection analysis.
HPLC Electrochemical analysis Electrode

"Fluorimeter For Flow Injection Analysis With Application To Oxidase Enzyme Dependent Reactions"
Anal. Chem. 1981 Volume 53, Issue 13 Pages 2110-2114
Tim A. Kelly and Gary D. Christian

Abstract: A simple effective flow fluorometer has been assembled and operated in conjunction with a flow injection analysls (FIA) system. A submicroliter capillary sheath flow cell Is used for fluorescence detection with a laser source. The Instrument has been tested for stability, precision, accuracy, sensitivity, dynamic range, and speed. Rhodamine 6G was used as a standard fluorophore. Application was also made to the clinical analysis of oxidase enzyme dependent reactions by reacting H2O2 with leucodlacetyldlchlorofluorescein to produce fluorescent dichlorofluorescein. Thls produced dye is excited at 488 nm with the argon laser. Concentrations of 10-^10 M hydrogen peroxide could be detected when injecting 25 µL aliquots.
Glucose Hydrogen peroxide Clinical analysis Fluorescence

"Continuous-flow High-field Nuclear Magnetic Resonance Detector For Liquid Chromatographic Analysis Of Fuel Samples"
Anal. Chem. 1981 Volume 53, Issue 14 Pages 2327-2332
James F. Haw, T. E. Glass, and H. C. Dorn

Abstract: The design and characterization of a continuous flow probe insert for a 200-MHz 1H nuclear magnetic resonance (NMR) detector for high-performance liquid chromatography (HPLC) are described. Modern superconducting magnet based systems present different requirements for flow probe design, but a considerable improvement over older spectrometers is readily achieved. Improvements in both spectroscoplc and chromatographic resolution are shown to enhance the analytical utility of LC-1H NMR. Spectral resolution is 2 Hz or 4 Hz with optimum sensitivity. Injection volumes of 10^-25 pL provide detection limits of 10 kg. The LC-1H NMR analyzes of a model mixture and two experimental petroleum based fuel samples are presented. A LC-IH NMR based method for calculating the average degree of substitution of aromatic ring systems is discussed in detail.
Oil Nuclear magnetic resonance HPLC

"Evaluation Of N-app For The Underpotential Deposition Of Mercury On Gold By Flow Injection Coulometry"
Anal. Chem. 1981 Volume 53, Issue 12 Pages 1855-1857
Timothy R. Lindstrom and Dennis C. Johnson

Abstract: A coulometric (100%) flow-through electrode was applied to a study of the underpotential deposition of Hg(I1) at a gold electrode. The deposition of a quantity of mercury significantly less than the equivalent of one monolayer occurs with an apparent number of electrons equal to 1.60 eq. mol-1. A closest-packed model for the deposition is proposed in which Hg(I) is co-adsorbed with Hg(0) in an atomic ratio of 1:2.
Mercury Coulometry Electrode Electrode Voltammetry

"Optically Discriminating Flow-through Cuvette"
Anal. Chem. 1982 Volume 54, Issue 3 Pages 596-598
Wolfgang Vogt, Siegmund Lorenz Braun, Siegfried Wilhelm, and Helmut Schwab

Abstract: n continuous flow anal. 2 different methods are commonly used to measure photometrically the air-bubble-segmented fluid stream. Either the air bubbles are removed by mech. venting previous to the measurement or the undesired signals of the multiple uncontrolled reflections of the light beam on the surface of the bubbles are suppressed electronically. Another possibility is described which uses a special optically discriminating cuvette. The passing of air bubbles through this quartz cuvette will result in total reflection of the light beam. Thus the absorbance signal from the photometer reaches values close to infinity. The total volume is ~60 µL, the optical volume is 10 µL for the air-filled, 30 µL for the fluid-filled flowcell. The length of the light path is 5 mm. The signal from the photometer can be recorded directly or fed onto a specially developed absorbance discriminator. The practical application of this system is demonstrated.

"Phase Separator For Flow Injection Analysis"
Anal. Chem. 1982 Volume 54, Issue 12 Pages 2127-2129
Koreharu Ogata, Kiyomi Taguchi, and Toshio Imanari

Abstract: A new phase separator with a polyethylene-backed porous polytetrafluoroethylene [9002-84-0] membrane was superior to that of existing systems causing smaller dispersion of peaks at larger-fraction volumes in bromocresol green and caffeine sample in flow injection anal.
Sample preparation

"Microsample-filtering Device For Liquid Chromatography Or Flow Injection Analysis"
Anal. Chem. 1982 Volume 54, Issue 12 Pages 2129-2130
Wayne S. Gardner and Henry A. Vanderploeg

Abstract: A micro-filtering device was interfaced with a loop injector to filter small (1 mL) samples before liquid chromatography or flow-injection anal. The device has an active filtering area of 3 mm2 and an internal dead volume of 0.04 mL. The filter holder was designed for convenient filter changing between sample injections.
HPLC

"Automatic Dialyzing-injection System For Liquid Chromatography Of Ions And Small Molecules"
Anal. Chem. 1982 Volume 54, Issue 14 Pages 2605-2607
Francis R. Nordmeyer and Lee D. Hansen

Abstract: A chromatography injection system that incorporates a hollow-fiber dialysis membrane is described. A sample is dialyzed against a small volume of recipient liquid which is delivered to the chromatograph. Dialysis serves to eliminate soluble polymeric materials, e.g., proteins, which would foul the chromatography column. Also the dialysis can serve to retain the polymer-bound portion of analyte and deliver only the free analyte to the chromatograph in which case the concentration. of free analyte is measured. Delivery of the dialyzate to the eluent stream of the chromatograph and rinsing of the dialyzer between samples are completely automated operations. Dialysis of simple inorganic ions requires ~1 min. Sample volumes may be as small as 40 µL. The injection system is demonstrated by measuring free Ca2+ in human blood serum. The precision of the injection system corresponds to relative standard deviation of ≤1%. This injection system should be useful for determination of ions and small molecules in blood, soil extracts, and in polymer-containing pharmaceuticals.
HPLC

"Continuous-flow Reducing Vessel In Determination Of Mercuric Compounds By Liquid Chromatography - Cold Vapor Atomic Absorption Spectrometry"
Anal. Chem. 1983 Volume 55, Issue 3 Pages 454-457
Masahiko Fujita and Elgo Takabatake

Abstract: A reducing vessel which couples liquid chromatography (LC) with cold vapor atomic absorption spectrometry (CVAAS) described for determination of mercuric compounds. The reducing vessel continuously reduces mercuric compounds, which are separated by LC, and the volatilized mercury is swept Into the CVAAS spectrometer with a continuous flow of air, where the atomic absorption is measured at 253.7 nm. Thus, CVAAS works effectively as a continuous detector for mercury In the effluent from LC. When stannous chloride Is used as reductant, mercury alkane thiolates are monitored. For the detection of Inorganic, methyl, and ethyl mercuric compounds, sodium borohydride Is used. The system Is demonstrated to detect mercury with high sensitivity and specificlty partly due to less matrix interference than In UV absorption detection.
Mercury HPLC Spectrophotometry

"Oscillometric Flow Cell For Measurement Of Conductivity And Permittivity"
Anal. Chem. 1983 Volume 55, Issue 11 Pages 1728-1731
Erno Pungor, Ferenc Pal, and Klara Toth

Abstract: A flow-through cell of concentric design with a body of PTFE (volume adjustable from 10 to 50 µL by altering the size of the electrodes), operating by the h.f. (42 MHz) conductance principle, is described (with diagrams); there is no galvanic contact between the electrodes (brass, coated with PTFE) and the solution being examined; as a result, the electrode surface layer is stable and measurements have good reproducibility.The calibration graph of conductivity vs. concentration. of aqueous KCl passing through the cell is rectilinear in the range 5 µM to 5 mM, and the signal is independent of flow rate (from 20 to 200 mL h-1).The cell has been applied in the determination of glucose by flow injection analysis (20 µL injection volume; water as carrier; amount detected ~100 ng of glucose).For permittivity measurements, the cell is calibrated with aqueous dioxan mixtures.
Glucose Conductometry Permittivity Electrode

"Comparison Of Sample Injection Systems For Flow Injection Analysis"
Anal. Chem. 1983 Volume 55, Issue 14 Pages 2461-2464
Jeffrey J. Harrow and Jiri Janata

Abstract: In flow-injection anal. the technol. for injection can be improved by using a system based on 4 solenoid pinch valves, which is very inexpensive, precise, and compatible with either pumps or gas propulsion. The system was evaluated and compared to other methods for sample injection.
pH Water Conductometry Electrode Field effect transistor

"Direct Liquid Sample Introduction For Flow Injection Analysis And Liquid Chromatography With Inductively Coupled Argon Plasma Spectrometric Detection"
Anal. Chem. 1984 Volume 56, Issue 2 Pages 289-292
Kimberly E. Lawrence, Gary W. Rice, and Velmer A. Fassel

Abstract: A micro-concentric nebulizer is described, use of which enables the solution from a flow injection analysis system, or the eluent from a HPLC column, to be analyzed directly by ICP-AES Detection limits by flow injection analysis - ICP ranged from 0.32 ppb for Mg to 140 ppb for Se, these being poorer, by factors ranging from 1.1 to 4.6, than those obtained by continuous nebulization with a cross-flow nebulizer. When Cr and As species were determined by HPLC - ICP, detection limits (ppm) were Cr(III) 0.44, Cr(VI) 0.43, As(V) 1.8 and As, as methanearsonic acid, 0.64. The very high linear velocity of the nebulizing gas and the excessive solvent loading were responsible for the poorer detection limits, and improvements to the nebulizer design are being investigated.
Arsenic(5+) Chromium(III) Chromium(VI) Magnesium methanearsonic acid Selenium HPLC Spectrophotometry

"Single-laser/crossed-beam Thermal Lens Detection For Short Path Length Samples And Flow Injection Analysis"
Anal. Chem. 1984 Volume 56, Issue 14 Pages 3002-3004
Yen Yang and Robin E. Hairrell

Abstract: The optical configuration described previously (Ibid., 1984, 56, 2336) is potentially useful for detection in liquid chromatography as well as for the cited applications. A 4-mW randomly polarized beam at 632.8 nm from a He - Ne laser is split by a polarizing beam splitter (Oriel model 2630) into a 2-mW pump beam, which is modulated, usually at 70 Hz, and a probe beam, which remains unchopped. Both beams are focused, and crossed at the centre of a 0.1-cm-pathlength flow-cell; under these conditions, the entire length of the thermal lens created by the pump radiation inside the cell defocuses the probe beam. The system has been used to detect bromophenol blue in a flow injection stream of ethanol. Its advantages over other configurations are discussed.
Bromophenol blue HPLC Spectrometry

"Liquid Core Optical Fiber Total Reflection Cell As A Colorimetric Detector For Flow Injection Analysis"
Anal. Chem. 1985 Volume 57, Issue 6 Pages 1012-1016
Kitao Fujiwara and Keiichiro Fuwa

Abstract: The construction is described of a long capillary cell in which a sample solution (in CS2 to provide total reflection) constitutes the core of an optical fiber. With use of a funnel-shaped glass to focus the light entering the cell, a low-power tungsten lamp was suitable as source. The cell was incorporated into a flow injection system for the determination of I- at 540 nm after oxidation to iodine by NaNO2. With use of a 5-m cell, a detection limit of 0.1 µg mL-1 was attained.
Iodine Iodide Spectrophotometry

"Pulsed Amperometric Detection Of Electroinactive Adsorbates At Platinum Electrodes In A Flow Injection System"
Anal. Chem. 1985 Volume 57, Issue 7 Pages 1373-1376
John A. Polta and Dennis C. Johnson

Abstract: The study of the effect of various adsorbates on the current - time response of platinum electrodes on application of a positive detection pulse (cf. Austin et al., Anal. Abstr., 1985, 47, 3J141) has been extended. Adsorbed electroinactive species, e.g., Cl- and CN-, alter the rate of surface oxide formation following the positive potential step so that triple step wave forms similar to those used for electroactive adsorbates can be applied to detection of electroinactive adsorbates injected into a stream of electrolyte. Both positive and negative peak response and both modes of detection are, for Cl-, reproducible to within 3% with a sensitivity of 0.2 ng. Calibration graphs are consistent with adsorption according to the Langmuir isotherm.
Chloride Cyanide Amperometry Electrode

"Two-valve Injector To Minimize Nebulizer Memory For Flow Injection Atomic Absorption Spectrometry"
Anal. Chem. 1985 Volume 57, Issue 9 Pages 2015-2016
James M. Harnly and Gary R. Beecher

Abstract: A single-line flow injection system for flame AAS with use of a pneumatic nebulizer has been modified to include three pumps and a second six-port rotary value (to reduce memory effects). The system was applied to the determination of K, Mg, Na and Zn in urine at a flow rate of 1.6 mL min-1. The blank signal returned to its starting value after two atomizations, and a 10-fold reduction of the nebulizer memory over the previous system was achieved.
Potassium Magnesium Sodium Zinc Urine Spectrophotometry

"Double-beam Thermal Lens Spectrometry"
Anal. Chem. 1985 Volume 57, Issue 13 Pages 2434-2436
K. L. Jansen and J. M. Harris

Abstract: The construction of a double-beam configuration for thermal-lens absorption measurements is reported, in which a single laser beam is split into two, only one beam being passed through the sample. Continuous modulation and lock-in amplification of the signal produced by subtraction of the beam intensities allow application of the system to real-time monitoring, such as flow injection analysis or HPLC. Double-beam thermal-lens detection was evaluated for the flow injection analysis of trace levels of iodine in CCl4.
Iodine Organic compound Spectrometry

"Sub-picolitre Detection With The Sheath-flow Cuvette"
Anal. Chem. 1985 Volume 57, Issue 13 Pages 2690-2692
Fahimeh Zarrin and Norman J. Dovichi

Abstract: The cuvette (illustrated) consists of a square-bore flow chamber (250 µm) with thick (1.5 mm) silica windows. The sample stream (e.g., an aqueous suspension of polystyrene latex spheres) is introduced into the centre of a flowing sheath stream and illuminated with a polarized He - Ne laser beam of 10 µm spot size; the scattered light is collected with a microscope. The detection volume of the system can be reduced to 5 fl provided a tightly focused laser beam is used. The system can be applied in liquid chromatography and flow injection analysis.

"Multifunction Valve For Flow Injection Analysis"
Anal. Chem. 1986 Volume 58, Issue 11 Pages 2348-2350
Junichi Toei and Nobuyuki Baba

Abstract: A simple injector that permits the introduction of the sample or sample and reagent into the flow stream is described and illustrated. The system is tested at flow rates of 0.5 and 1.0 mL min-1 with aqueous 0.1% acetone as sample solution and detection at 254 nm. The coefficient of variation are between 0.46 and 1.09% (n = 7).
Acetone Spectrophotometry

"Thermospray Interfacing For Flow Injection Analysis With Inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Chem. 1986 Volume 58, Issue 12 Pages 2558-2561
J. A. Koropchak and D. H. Winn

Abstract: Details and a diagram are given of a thermospray device for interfacing between the flow injection system and the ICP torch. Operating conditions (specified) were selected for optimizing signal-to-noise ratios for the continuous introduction of standards with the cross-flow nebulizer. The system gives improved detection limits compared with a concentric nebulizer, and affords adequate detection for low levels in small sample volume The effects of increasing the liquid sample flow rate are discussed.
Spectrophotometry

"Amperometric Detection Of Picomole Samples In A Microdisk Electrochemical Flow-jet-cell With Dilute Supporting Electrolyte"
Anal. Chem. 1986 Volume 58, Issue 13 Pages 2859-2863
John W. Bixler and Alan M. Bond

Abstract: The properties of 5 µm diameter carbon and 50 µm diameter platinum micro-disc electrodes in a wall-jet electrochemical cell have been examined during operation in flow injection mode with µM supporting-electrolyte concentration. The advantages of using a low-noise, low-resistance, battery-operated voltage offset device in series with a femtoammeter in the two-electrode mode for the determination of 10 to 100 nM concentration. with very small micro-electrodes are described and contrasted with those for potentiostat-based instrumentation. Signal-to-noise ratios are enhanced and these micro-sensors function well in highly resistive media (dilute electrolyte and organic solvents), providing the prospect for applications in HPLC and flow injection analysis with electrochemical detection.
Amperometry Electrode Electrode

"Properties And Applications Of The Concentration Gradient Sensor To Detection Of Flowing Samples"
Anal. Chem. 1986 Volume 58, Issue 14 Pages 3207-3215
Janusz Pawliszyn

Abstract: An optical sensor is described for the monitoring of concentration. gradient by measurement of the refractive-index gradient with use of a non-absorbed light beam as probe in the detector volume. Light-beam deflection measurement (Schlieren optics) has been used to monitor analyte concentration. in flowing streams. For sucrose the rectilinear dynamic range extends from 5 µM to around 0.1M. The sensor can differentiate between sharp and broad peaks, and peak broadening can be avoided by the sheath-flow method. Response is rectilinear in the non-selective mode. The detector was tested alongside a standard refractive-index detector (Waters R400) and its applicability in flow injection analysis and HPLC systems is demonstrated.
HPLC Refractometry Sensor

"Versatile Instrument For Pulse Width Measurement"
Anal. Chem. 1986 Volume 58, Issue 2 Pages 507-509
Purnendu K. Dasgupta and Ellis L. Loree

Abstract: The design and operation of a counter for measuring the width of a signal pulse, as encountered in chromatography or flow-injection analysis, is described. The counter can be used for counting up to a maximum elapsed time of 999.99 s with 200 µs accuracy and 10 ms readability and audibly alerts the operator at the completion of counting. The threshold voltages to begin and stop counting (on the leading and trailing edges of the pulse, respectively) are both individually adjustable at 0-1 V. The counter can be reset automatically at the completion of counting, or manually at any time, or by an external device. Data ready signal, external reset, and parallel BCD output are provided for an external data acquisition device. Counter status and overflow conditions are indicated on the counter display.

"Coulostatic Electrochemical Detection In Flow Injection Analysis"
Anal. Chem. 1987 Volume 59, Issue 2 Pages 244-247
Susan R. Mikkelsen and William C. Purdy

Abstract: The design and construction of a coulostatic electrochemical detection system is described and illustrated and an expression relating the peak area to analyte concentration, flow cell geometry and mobile phase is derived. The method is demonstrated, e.g., by the determination of ferrocene in acetonitrile containing tetrabutylammonium tetrafluoroborate(I) as the supporting electrolyte. A rectilinear relationship is obtained between peak area and concentration. for 5 to 20 µM-ferrocene in a mobile phase containing 0.18 µM-I. The coefficient of variation (n = 5) at the 1 µM level are 4.5% for peak height and 6.1% for peak area measurements. The detection limit for 2-aminophenol in 0.5 M phosphate buffer is 5 pmol. The method is applied to HPLC and flow injection analysis.
Ferrocene 2-Aminophenol Coulometry

"Applications Of A Versatile Injection Valve For Flow Injection Analysis"
Anal. Chem. 1987 Volume 59, Issue 8 Pages 1246-1248
Brice C. Erickson, Bruce R. Kowalski, and Jaromir Ruzicka

Abstract: The valve design reported has six ports on the front rotor, which are individually accessible giving a total of 12 ports which provide a wide range of options in its configuration. Numerous diagrams are given. Different arrangements in the load and inject positions are given, allowing alternate sample injection, simultaneous injection, gradient injection and double sample injection.

"Dual Porous Electrode Membrane Cell For Detection Of Non-electroactive Species In Flowing Streams"
Anal. Chem. 1987 Volume 59, Issue 18 Pages 2260-2263
Antonin Trojanek and Stanley Bruckenstein

Abstract: A dual electrode detector capable of being used in flowing streams is described. One electrode generates a volatile reagent from a constituent present In the flowing stream, which then reacts with a dissolved analyte also present In the flowing stream. Excess volatile reagent diffuses through a non-wetting porous membrane to a second electrode at which the unreacted volatile reagent Is determined by constant potential electrolysis. The utility of this detector Is demonstrated by the determination of allyl alcohol with electrogenerated bromine In the range 23-697 ng of allyl alcohol.
Allyl alcohol Water Amperometry Electrode

"Gas Diffusion Unit With Tubular Microporous Poly(tetrafluoro-ethylene) Membrane For Flow Injection Determination Of Carbon Dioxide"
Anal. Chem. 1987 Volume 59, Issue 24 Pages 2930-2932
Shoji Motomizu, Kyoji Toei, Tohru Kuwaki, and Mitsuko Oshima

Abstract: A gas diffusion unit was constructed, without the use of glue, from two T-connectors linked by double tubing consisting of a micro-porous PTFE membrane inner tube (1 mm i.d. x 1.8 mm o.d.) and an outer PTFE tube (2 mm i.d.). The tubing was fixed to the connectors by a flange-type union. A carrier stream (0.8 mL min-1) of 0.18 M H2SO4 flowed through the outer tube and a cresol red color reagent solution (0.8 mL min-1) flowed through the inner tube. Standard solution (140 µL) of NaHCO3 and river water samples were injected into the carrier solution and absorbance changes were measured at 410 nm. Results agreed with those obtained by indirect photometric ion chromatography.
Carbon dioxide River Spectrophotometry

"Thin-layer Spectroelectrochemical Cuvette Cells With Long Optical Path Lengths"
Anal. Chem. 1988 Volume 60, Issue 15 Pages 1645-1648
Yupeng Gui, Steven A. Soper, and Theodore Kuwana

Abstract: The construction and properties are described of thin-layer transmission spectroelectrochemical cells that can be used in a continuous-flow system. For the first cell, a vitreous-carbon block (~2.8 cm x 9.8 mm x 1.7 mm) was placed within a standard spectrophotometric vitreous-silica cell to form the working electrode. Two strips of 125 µm thick PTFE film were fused to the block along the top edges of the cell to provide seals, and a small hole was made in the base of the cell. Surface area of solution contact was ~5.46 cm2. For the second cell, a 1-cm pathlength vitreous-silica cell was used, fitted with Pt-foil working and counter electrodes (each 1 cm x 0.5 cm, 0.1 mm thick) which were bonded to a press-fitted PTFE plug within the cell that defined the effective pathlength (cf. Simone et al., Anal. Abstr., 1983, 45, 1J107). Diagrams are presented to show cell construction and solution flow. Specimen cyclic voltammograms and flow injection analysis response graphs (electrochemical and optical transmission) are presented.
Ferricyanide Ferrocyanide Electrode Spectroelectrochemistry Spectrophotometry Voltammetry

"Cobalt Phthalocyanine/cellulose Acetate Chemically Modified Electrodes For Electrochemical Detection In Flowing Streams"
Anal. Chem. 1988 Volume 60, Issue 15 Pages 1642-1645
Joseph Wang, Teresa Golden, and Ruiliang Li

Abstract: The detector electrode was formed by the attachment to a carbon-paste electrode of a vitreous-carbon disc (3 mm diameter) coated with cellulose acetate - cobalt phthalocyanine (500:3) co-deposited by solvent evaporation from a solution in acetone - cyclohexanone and hydrolyzed in 0.07 M KOH after deposition to adjust permeability. The multi-functional character of the coating enhanced amperometric detection. Examples of cyclic and hydrodynamic voltammograms of oxalic acid (0.2 and 0.1 mM, respectively) and a hydrodynamic voltammogram of 0.1 mM hydrazine sulphate are presented.
Amperometry Electrode Electrode

"Pulsed Coulometric Detection With Automatic Rejection Of Background Signal In Surface-oxide-catalyzed Anodic Detection's At Gold Electrodes In Flow-through Cells"
Anal. Chem. 1988 Volume 60, Issue 20 Pages 2288-2293
Glen G. Neuburger and Dennis C. Johnson

Abstract: With use of a Dionex thin-layer flow-through cell fitted with a gold electrode and a SCE, a variant of coulometric detection was applied in which the detection potential in the pulsed waveform was varied cyclically (in potential-step or -sweep mode) during current integration. Requirements for background rejection in such a system are described. The technique was applied in the flow injection determination of thiourea as a model for S compounds that undergo surface-catalyzed anodic reaction with formation of surface oxide. Slightly greater peak-height response and appreciably lower background were obtained for 100 µM-thiourea in 0.25 M NH4NO3 than by conventional pulsed coulometric or pulsed amperometric detection. Baseline was unchanged over two units of pH, and the detector should be applicable in pH-gradient chromatography. However, the technique is thought unlikely to give improved detectability for carbohydrates.
Thiourea Amperometry Electrode

"Nanoliter Volume Sequential Differential Concentration Gradient Detector"
Anal. Chem. 1988 Volume 60, Issue 24 Pages 2796-2801
Janusz Pawliszyn

Abstract: A simple optical detection system is described and illustrated that has a detection volume of 2 nl. It comprises a He - Ne laser, means of generating two focused beams propagating close to each other, and a single photodiode sensor. The output signal from the sensor is proportional to concentration. over four orders of magnitude, and the refractive-index gradient detection limit is 2 x 10 -4 refractive index unit m-1 (equivalent to 0.7 µm-sucrose). The system has been applied in flow injection analysis and capillary zone electrophoresis.
Electrophoresis Spectrophotometry

"Characterization Of An Ion-selective-electrode Wall-jet Detector For Flow Injection Analysis"
Anal. Chem. 1989 Volume 61, Issue 8 Pages 922-924
James G. Douglas

Abstract: A simply constructed detector of the cited type incorporating a flat-membrane F--selective or pH electrode is described. The effects of flow rate, jet-nozzle - electrode distance, jet-orifice diameter and sample size were studied.
Fluoride pH Electrode Electrode Electrode

"Comparison Of Paraffin Oil And Poly(chlorotrifluoriethylene) Oil Carbon-paste Electrodes In High-organic-content Solvents"
Anal. Chem. 1989 Volume 61, Issue 22 Pages 2585-2588
Neil D. Danielson, Julie Wangsa, and Margaret A. Targove

Abstract: A carbon-paste electrode prepared with use of Kel-F oil [a poly(chlorotrifluoriethylene)oil] as mulling liquid showed an enhanced response over the standard Nujol carbon-paste electrodes, for amperometric detection in flow injection analysis with mobile phases of both low and high acetonitrile content. The response of both types of electrode were dependent on the polarity of the organic solvent in the mobile phase.
Electrode Amperometry

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

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

"Electrocatalysis And Amperometric Detection Using An Electrode Made Of Copper Oxide And Carbon Paste"
Anal. Chem. 1991 Volume 63, Issue 17 Pages 1714-1719
Youqin Xie and Calvin O. Huber

Abstract: Copper oxide - carbon paste (1:4) electrodes were applied in the amperometric determination of carbohydrates, amino-acids, alcohols and amines in flow systems. With detection at +0.55 V vs. Ag - AgCl in 0.1 M NaOH as supporting electrolyte, calibration graphs were rectilinear over ~2 orders of magnitude for ethanol and ~5 orders of magnitude for the other compounds. Detection limits (tabulated) were 0.1 to 3.2, 0.4 to 4, 2 to 4, 0.2 to 0.3 and 0.2 to 28 ng for carbohydrates, amino-acids, diols, amines and 'other' compounds (ethanol, glycerol and Triton X-100), respectively.
Alcohols Amines Amino Acids Carbohydrates Ethanol Glycerol Triton X-100 Amperometry Electrode Electrode

"Multi-channel Electrochemical Detection With A Micro-electrode Array In Flowing Streams"
Anal. Chem. 1992 Volume 64, Issue 1 Pages 44-49
Atsushi Aoki, Tomokazu Matsue, and Isamu Uchida

Abstract: A 16-channel microelectrode array was used to develop a multi-channel electrochemical detection system for flow injection analysis (FIA) and HPLC. Current responses at 16 micro-band electrodes held at different potentials (controlled by a multi-potentiostat) were collected to provide three-dimensional results of time, current and potential. The calibration graph was rectilinear from 10 nM (detection limit) to 1 mM of (ferrocenylmethyl)trimethylammonium. A 5-step potential staircase of 10 mV step height was applied to the 16 electrodes to give 80-channel detection, and this system was applied to FIA and HPLC of a mixture of ferrocene derivatives, ascorbic acid, uric acid and catecholamines. Eighty data points could be obtained in 0.26 s. The detection of uric acid and ascorbic acid in blood and urine was demonstrated.
Ascorbic acid Uric acid Catecholamines Blood Urine Electrode

"Pulsed Sample Introduction Interface For Combining Flow Injection Analysis With Multi-photon-ionization Time-of-flight Mass Spectrometry"
Anal. Chem. 1992 Volume 64, Issue 7 Pages 769-775
Alan P. L. Wang and Liang Li

Abstract: Sample molecules carried by a liquid carrier (e.g., methanol at 0.5 mL min-1) were vaporized by passage through a heated capillary tube to form aerosol droplets which were entrained in the sample vaporizer of a high-temp. pulsed nozzle. The vapor was injected into the time-of-flight mass spectrometer at a repetition rate determined by the ionization source. The interface described was used to detect both volatile and non-volatile compounds, including those of environmental and biological significance. The average coefficient of variation was 4 to 8%. There were no memory effects or severe peak tailing, and cluster formation during supersonic jet expansion was not a problem. The detection limits for aniline, tryptamine and indole-3-acetic acid were 3, 4 and 140 ng, respectively. The calibration graphs were rectilinear over two-orders of magnitude of analytical range. A pulsed sample introduction (PSI) interface is developed to combine flow injection analysis with a time-of-flight mass spectrometer. In PSI, sample molecules carried by a liquid carrier such as methanol at a flow rate of 0.5 mL/min are vaporized by passing through a heated capillary tube and then through a sample vaporizer of a high-temp. pulsed nozzle. The resulting sample vapors are introduced into the mass spectrometer in a pulsed form and ionized by laser-induced multiphoton ionization. The applicability of this interface for the detection of volatile and nonvolatile compounds is studied. It is found that a variety of chemicals including molecules with environmental or biological significance can be studied by this method. Preliminary studies of the performance of this interface are reported. It is shown that reproducible results from repeated injection of the same concentration. of samples can be readily obtained. The average relative standard deviation is in the range of 4-8%. No memory effects and severe peak tailing are found with this PSI interface. The detection limits of the present technique are compound dependent. For aniline, tryptamine, and indole-3-acetic acid, the detection limits are found to be 3, 140, and 4 ng, respectively. Excellent linearity over two orders of magnitude of analytical range can be obtained for quantitation. It is also shown that cluster formation during the supersonic expansion is not a major problem in this technique.
Methanol Environmental Biological Mass spectrometry

"The Fountain Cell: A Tool For Flow-based Spectroscopies"
Anal. Chem. 1992 Volume 64, Issue 21 Pages 2657-2660
Kurt M. Scudder, Cy H. Pollema, and Jaromir Ruzicka

Abstract: The cited flow cell (described with diagrams) is constructed of a PTFE or Plexiglas cylinder with a top consisting of a microscope cover slip separated from the cell body by a PTFE spacer. The inlet and outlet tubes are at the centre and bottom, respectively, of a ring-shaped well having i.d., o.d. and depth of 16, 20 and 2 mm, respectively. Fluid enters the cell, moves outward through the thin flow path between the cell body and the cover slip, collects in the ring-shaped well and exits through the outlet tube. A new cell design for flow injection anal., the fountain cell, is introduced that exploits radial flow to produce a thin disk-shaped detection volume with a large surface area. It is potentially suitable for reflectance, fluorescence, chemiluminescence, and radiometric measurements. Its use as a perfusion chamber for observing dynamic responses of living cells to fast perfusate changes by fluorescence microscopy is presented.
Chemiluminescence Fluorescence Spectrophotometry

"Amperometric Monitoring Of Chemical Secretions From Individual Pancreatic β-cells"
Anal. Chem. 1993 Volume 65, Issue 14 Pages 1882-1887
Robert T. Kennedy, Lan Huang, Mark A. Atkinson, and Paula Dush

Abstract: A glass-encased carbon fiber micro-electrode was modified with a polynuclear RuO/CN-Ru film by dipping the micro-electrode in a solution of 0.1 M KCl, 2 mM RuCl3.H2O and 2 mM K4Ru(CN)6 adjusted to pH 2 with HCl. The electrode potential was cycled between +0.47 and +1.07 V at 50 mV/s for 25 min, then the electrode was rinsed and dried. Measurements using a flow injection apparatus in various electrolytes at pH 2 gave a detection limit of 0.1 µM-insulin (I). In physiological buffer, with the electrode periodically held at +0.4 V, the detection limit was 0.5 µM-I. Secretion from a single β cell that had been stimulated with K+ or glucose was measured by placing the electrode 1 µm away. The recordings consisted of a series of current spikes averaging 38 ms fwhm, which decreased in height and increased in width as the electrode was moved away from the cell. The results supported the hypothesis that the spikes represent rapid changes in I concentration. at the electrode surface resulting from its secretion by exocytosis.
Cell Amperometry Electrode Electrode

"High-precision Liquid Chromatography-combustion Isotope Ratio Mass Spectrometry"
Anal. Chem. 1993 Volume 65, Issue 23 Pages 3497-3500
Richard J. Caimi and J. Thomas Brenna

Abstract: The HPLC eluate was applied to a stainless steel wire moving at 12 cm/s, which then passed through an oven at 150°C operated with counterflow of He before entering a furnace (15 cm x 5 mm) containing two 8 cm Cu wires and an 8 cm Pt wire of 0.003 in. diameter and maintained at 850°C; before use, the furnace was kept at 650°C with passage of O2 for 15 h to oxidize the Cu to CuO. Helium was passed through the furnace to sweep the CO2 formed by combustion of organic compounds via a water trap to a mass spectrometer for measurement of the ratio of 13C to 12C. The wire was subsequently cleaned in a furnace at 800°C. The technique was used in conjunction with the HPLC of carbohydrates on a column (12.5 cm x 4.6 mm i.d.) of Partisphere 5 Pac with aqueous 80% acetonitrile as mobile phase (1.2 ml/min) and in the detection of fatty acids applied to the wire after direct injection in hexane as carrier solvent. The routine precision of δ13C was 0.5% in the range -28 < δ13C < 83% in flow injection mode, or 1% in LC mode owing to limitations of sample size applied to the wire.
Mass spectrometry HPLC

"Computer-controlled Micropump Suitable For Precise Microlitre Delivery And Complete Inline Mixing"
Anal. Chem. 1994 Volume 66, Issue 1 Pages 73-78
Takashi Korenaga, Xiaojing Zhou, Tosio Moriwake, Hideki Muraki, Tameo Naito, and Sannosuke Sanuki

Abstract: A computer-controlled micropump for use in flow analyzes is described (diagram and details given). The pump allows precise microlitre delivery and complete inline mixing. The instrument is particularly suitable for heterogenous flow analysis and flow analysis based on slow reactions, as it provides a large interface between immiscible phases or miscible streams just after merging and hence promotes mass transfer in radial directions, leading to an increase in sampling rate and sensitivity. The pump can be used in process analysis over long periods of time and was successfully applied to the determination of COD.

"Application Of Photochemical Reaction In Electrochemical Detection Of DNA Intercalation"
Anal. Chem. 1994 Volume 66, Issue 8 Pages 1236-1241
P. C. Pandey and H. H. Weetall

Abstract: Portions (20 µL) of 0.2 µM-9,10-anthraquinone-2,6-disulfonic acid (I) were injected into a carrier stream of 0.1 M phosphate buffer of pH 7.5 and 20 mM glucose which was passed over the surface of a UV lamp (λmax = 366 nm) through a network of PTFE tubing (10 m x 0.3 mm i.d.) at 30 ml/h. The reduced form of I was oxidized at the surface of a tetracyanoquinodimethane (TCNQ)-modified graphite paste electrode (preparation described) covered with a Nucleopore membrane in a flow cell. Preliminary [photo]voltammetric experiments (described) were performed with I or 9,10-anthraquinone-2-sulfonic acid (II) and glucose in 0.1 M phosphate buffer of pH 7 containing 0.1 M NaCl. A calibration graph of FIA response (µA) was linear for 0.014-0.121 µmol of I. Intercalation between DNA and I or II was established and there was a linear relation between the decrease in electrochemical response and DNA concentration at a constant substituted anthraquinone concentration. Intercalated anthraquinone molecules were completely replaced by molecules such as ethidium bromide which were more strongly intercalated within DNA. A flow injection analysis (FIA) system for the detection of the compounds that intercalate within DNA is reported. A derivative of 9,10- anthraquinone has been used as the reference compound for photoelectrochemical detection. The sodium salts of 9,10-anthraquinone- 2,6-disulfonic acid and 9,10-anthraquinone-2-sulfonic acid are photochemically activated and then reduced in the presence of an electron donor (glucose). The electrochemical signal is based on the measurement of the anodic current resulting from the oxidation of the reduced form of 9,10-anthraquinone. The reduced form of the 9,10- anthraquinone is oxidized through a mediated mechanism at the surface of a tetracyanoquinodimethane-(TCNQ)-modified graphite paste electrode covered by a Nucleopore membrane. TCNQ acts as an efficient mediator for the oxidation of reduced 9,10-anthraquinone. Cyclic voltammetry, photocyclic voltammetry, and the photoelectrochemical FIA response of 9,10-anthraquinone are reported. Experimental results show that these anthraquinones can be intercalated within the helix of double-stranded calf thymus DNA. The anthraquinone molecules that are intercalated within DNA cannot be oxidized due to their limited transport to the modified electrode surface. This results in a decrease in the anodic current at a constant concentration of anthraquinone after intercalation. There is a linear relation between the decrease in electrochemical response and the DNA concentration at a constant concentration of anthraquinone. The intercalated anthraquinone molecules can be completely replaced by another intercalating agent (i.e., ethidium bromide) that is more strongly intercalated within DNA, thereby regenerating the electrochemical response.
9,10-Anthraquinone-2,6-disulfonic acid 9,10-Anthraquinone-2-sulfonic acid Glucose Spectrophotometry Voltammetry Electrode

"Amperometric Determination Of N-nitrosamines In Aqueous Solution At An Electrode Coated With A Ruthenium-based Inorganic Polymer"
Anal. Chem. 1994 Volume 66, Issue 17 Pages 2771-2774
Waldemar Gorski and James A. Cox

Abstract: A new electrode is described for the determination of N-nitrosamines by HPLC or FIA. Vitreous carbon electrodes were coated by electrodeposition with a thin film of mixed-valent oxo-bridged Ru stabilized by cyano cross-links to give a O/Ru/CN ratio of 3:5:12 in the film. The electrodes were initially polished with alumina (1, 0.3 and 0.05 µm), washed with water and electroplated by cyclic voltammetry for 30 cycles from 0.5-1.1 V vs. Ag/AgCl at 50 mV/s in 2 mM RuCl3/2 mM K4Ru(CN)6/0.5 M KCl at pH 2. The electrodes were conditioned by cycling from 0.5-1.13 V in phosphate buffer. Samples of N-nitrosodimethylamine, N-nitrosodi-n-propylamine and 4-nitroso-NN-diethylaniline were analyzed on a column (15 cm x 4.6 mm i.d.) of Shim-pack CLC-ODS (5 µm) with 0.1 M phosphate buffer of pH 1.5 as mobile phase (1 ml/min) and a three-electrode flow cell with the above electrode, Pt wire counter electrode and Ag/AgCl reference electrode. For FIA the analytical column was eliminated and the flow rate was 1.2 ml/min. The calibration graph was linear for 0.05-1 µM for the three nitrosamines with detection limits of 10 nM.
N-Nitrosamines HPLC Electrode Voltammetry Amperometry

"Flow Injection Techniques For Water Monitoring"
Anal. Chem. 1994 Volume 66, Issue 18 Pages 916A-922A
Kevin N. Andrew, Nicholas J. Blundell, David Price, Paul J. Worsfold

Abstract: The basic features of FIA that make it useful in laboratory and process analysis are outlined and its application to the in situ monitoring of natural and polluted waters is discussed. The instrumentation available for fresh water, marine and ground water monitoring is considered.
Ground Sea River Spectrophotometry

"Flow Injection Analysis With High-sensitivity Optical Rotation Detection"
Anal. Chem. 1994 Volume 66, Issue 19 Pages 3093-3101
Charles A. Goss, Douglas C. Wilson, and William E. Weiser

Abstract: The construction and characterization of a flow injection analysis system with high-sensitivity, laser-based (488 nm), optical rotation detection (FIA-OR) is described. Baseline noise is reduced to - 10 µdeg by addition of a pressure pulsation damper between the pump and the autosampler. Sensitivity is increased 100-fold compared to a high-quality conventional polarimeter, and detection of a 43 ng sample of sucrose (25-pdeg rotation) is demonstrated. The instrument response is linear over a 500-fold range of concentration to 21 pg of sucrose injected, with the upper limit set by laser beam distortion caused by sample refractive index effects. Specific rotation values at 488 nm for 11 organic molecules are measured by FIA-OR with good precision and agree with values obtained by a conventional polarimeter. FIA-OR analysis of enantiomeric purity of (1S2R)-(+)-ephedrie is found to be more discriminating than conventional polarimetry for the analysis of solutions with high enantiomeric excess.
Polarimetry

"Ferrocene-conjugated Polyaniline-modified Enzyme Electrodes For The Determination Of Peroxides In Organic Media"
Anal. Chem. 1995 Volume 67, Issue 6 Pages 1109-1114
Chia-Lin Wang and Ashok Mulchandani

Abstract: The development and characteristics of a reagentless amperometric organic phase enzyme electrode (OPEE) employing covalently attached horseradish peroxidase and an electrochemically deposited ferrocene-modified polyaniline film on a glassy carbon electrode is reported. The covalent attachment of ferrocene to an electrochemically deposited insoluble polymer film provided a mechanism of preventing the leaching of ferrocene into the predominantly organic solvents, required for construction of reagentless OPEE. Hydrodynamic voltammetry studies showed that the response of the OPEE to hydrogen peroxides increased at higher cathodic potentials; however, interference due to molecular oxygen also increased. Interference of molecular oxygen was minimized when the OPEE was operated at an applied potential of -50 mV (or less negative) vs Ag/AgCl. The cathodic response of the OPEE was found to increase steeply when the aqueous buffer content of the acetonitrile was increased from 0 to 5 and then plateau with no further increase when the buffer content was increased to 30. The dynamic properties of this enzyme electrode were exploited for the detection of micromolar concentrations of different peroxides in flow injection analysis where the sensitivity trend was lauroyl peroxide > hydrogen peroxide > 2-butanone peroxide > cumene hydroperoxide > tert-butyl hydroperoxide. Applicability of the enzyme electrode for measurement of peroxide in real sample was demonstrated. Copyright 1995, American Chemical Society.
Lauroylperoxide Hydrogen peroxide 2-Butanoneperoxide Cumylhydroperoxide t-Butylhydroperoxide Commercial product Sensor Voltammetry Amperometry Electrode Electrode

"A Coaxial Jet Mixer For Rapid Kinetic Analysis In Flow Injection And Flow Injection Cytometry"
Anal. Chem. 1995 Volume 67, Issue 17 Pages 2743-2749
L. D. Scampavia, G. Blankenstein, J. Ruzicka, and G. D. Christian

Abstract: The construction and evaluation of a simple coaxial jet mixer for rapid confluent mixing under laminar flow conditions are described. The flow in the outer annular capillary is greater than that in the inner capillary to create shear forces at the point of confluence. The features of the mixer include complete mixing of two solutions within 55 ms, sample analysis in 100 ms on a FACS Analyzer cytometer (60 µL/min flow), temporal resolution of kinetic events at 14-28 ms intervals and variable timing of reagent addition in the range 100 ms to 3 min. Potential spectral distortions due to core flow variations are eliminated. The application of the mixer in cytometry and FIA of rapid kinetic events is discussed. A simple coaxial jet mixer for rapid and efficient confluent mixing under laminar flow conditions (Re <5) is described. This device demonstrates exceptional control of mixing between two laminar streams by creating shear forces due to variable flow velocities at the point of confluence. It is suitable for flow injection and cytometric analyzes of rapid kinetic events which require contact mixing of two solutions and subsecond measurements of the evolving reaction. This apparatus was devised for flow injection cytometry as performed on a Becton Dickinson FACS Analyzer. Under normal cytometric conditions and at a sample introduction rate of 60 ml/min, the laminar jet mixer is capable of complete mixing of two solutions within 55 ms. Kinetic measurements can be performed on the FACS Analyzer in a variable time range of 100 ms to 3 min with 14-30 ms temporal resolution of the studied event. Since no boost in core flow is required, potential spectral distortions due to core flow variations are eliminated. This coaxial jet mixer can be easily constructed and employed on a variety of cytometers as well as conventional flow injection analysis systems, since it is an effective mixer under most flow conditions. Copyright 1995, American Chemical Society.
Flow cytometry

"Phosphate Determination By Flow Injection Analysis With Geometrically Deformed Open Tubes"
Fresenius J. Anal. Chem. 1984 Volume 317, Issue 6 Pages 671-671
H. Engelhardt und R. Klinkner

Abstract: UFL
Phosphate Spectrophotometry

"Properties Of The Bubble-electrode, A New Electrochemical Flow-through Detector"
Fresenius J. Anal. Chem. 1984 Volume 318, Issue 5 Pages 352-353
Fritz Scholz and G&uuml;nter Henrion

Abstract: UFL
Electrode Electrode

"Determination Of Phosphate By Flow Injection Analysis Using Geometrically Deformed Open Tubes"
Fresenius J. Anal. Chem. 1984 Volume 319, Issue 3 Pages 277-281
H. Engelhardt und R. Klinkner

Abstract: The use of geometrically deformed open tubes ('knitted capillaries') for the rapid determination of PO43- in flow injection systems is described. By using the method of Eibl and Lands (Anal. Abstr., 1970, 19, 2190), a capillary tube (250 cm x 0.25 mm) at 70°C permitted the determination of PO43- with a reaction time of 4 s. The detection limit was 0.2 ppm, and the method enabled 300 determinations to be performed hourly. The use of a cyclone mixing chamber allowed thorough mixing of sample and reagent.
Phosphate Spectrophotometry

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

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

"Some Applications Of Enthalpimetric Detection In Flow Injection Analysis"
Fresenius J. Anal. Chem. 1987 Volume 329, Issue 4 Pages 440-443
W. E. van der Linden Contact Information, M. Bos, H. H. Heskamp and H. Wilms

Abstract: A flow-through arrangement of thermistors for detecting heat changes due to chemical reactions was included in a flow injection system. Changes of 0.001°C could be measured reproducibly. Working ranges of analyte concentration. depended on reaction enthalpy and varied from 1 mM to 10 M for acids and bases and 10 to 1000 ppm for, e.g., alkylhydroperoxides. Typical signals are presented for NaOH (reaction with HCl), Ca(II) (EDTA determination), H2O2, t-butyl hydroperoxide and cumyl hydroperoxide (SO2 reduction in presence of amine).
Sodium hydroxide Calcium(2+) Hydrogen peroxide t-Butylhydroperoxide Cumylhydroperoxide Enthalpimetry Thermistor

"A New Microdialysis Unit For Flow Injection Analysis"
Fresenius J. Anal. Chem. 1988 Volume 329, Issue 6 Pages 688-690
Ulf Sundqvist

Abstract: The unit contains a dialysis cell and a manifold for reagent addition and reaction in a single module. Its use is illustrated by the colorimetric determination of Cl- in a three-line manifold for streams of donor (H2O, 1.5 mL min-1), acceptor (H2O, 1.5 mL min-1) and reagent [Hg(SCN)2 + Fe(NO3)3, 1.2 mL min-1]. An Elkay type C membrane was used for dialysis. Sample solution (100 µL) was injected into the donor stream, which flowed to waste after dialysis, and detection was at 465 nm. Under these conditions, the dialysis efficiency was ~11% and the dilution-loss factor ~9. Sample throughput was 90 h-1 with reproducibility of 1.0 to 1.5%. The unit is still under development.
Chloride Spectrophotometry

"New Flow Injection Analysis Methods For The Determination Of Ions. 2. Sulfate, Sulfite And Nitrate, Nitrite"
Fresenius J. Anal. Chem. 1988 Volume 330, Issue 6 Pages 494-497
N. Almhofer und F. Frenzel

Abstract: The apparatus described previously (see Part I, later in this section) is used, with measuring electrodes of Pb - PbSO4 for SO42-, Pb for SO32-, Sn for NO3-, and Sb for NO2-. Measurement is potentiometric for SO42-, otherwise amperometric. The measurement ranges are 50 µM to 10 mM for SO42- and NO3-, 10 µM to 10 mM for SO32-, and 0.1 to 10 mM for NO2-. Results for various waters are given, showing a typical coefficient of variation of 1.5% for SO42- and SO32- and 2.5% for NO3- and NO2-. Selectivity coefficient are quoted and instructions are given for electrode preparation. The measurement and calibration procedures are as described previously, except that the carrier stream consists of 100 mL of 0.1 mM Na2SO4 plus 200 mL of ion buffer (10 mM NaClO4 - 10 mM HClO4) diluted to 1 l, and cations (especially Ca) must be exchanged for Na beforehand. Results for analysis of waters are presented.
Sulfate Sulfite Nitrate Nitrite Environmental Amperometry Electrode Potentiometry

"Preparation And Performance Of A Coated Tubular Solid-state Cadmium-selective Electrode In Flow Injection Analysis"
Fresenius J. Anal. Chem. 1988 Volume 331, Issue 6 Pages 594-598
Jacobus F. van Staden

Abstract: The cited electrode contained a Cd tube (8 mm x 1 mm) joined by its ends to Tygon tubes (2 cm x 0.5 mm) and wrapped around with the inner wire of a shielded cable to ensure electrical contact with an Orion Research (model 901) microprocessor Ionalyzer, and the unit was isolated with epoxy-resin. After cleaning the Cd tube internally with concentrated HNO3 and water, a Cd - CdS membrane was formed and activated by electro-deposition of CdS on to its inner wall from 0.1 M Na2S at 2 mL min-1 and 20 mA cm-2. The electrode was conditioned in 1 mM Cd(NO3)2 at pH 3 for 24 h. When used with an Orion 90-02 double-junction reference electrode with aqueous 10% KNO3 in the outer chamber in a described flow injection analysis system to analyze 30 µL samples at a rate of 60 h-1, the electrode showed rectilinear response from 0.25 to 10 g L-1 of Cd(II). There was no interference from Fe(II) or from up to 5 g L-1 of Cl- or SO42- or 1 g L-1 of NO3-; Ag, Hg(II), Cu(II) and Fe(III) interfered at 1 mg l-1, and I-, S2-, Pb(II) and Br- interfered at 5, 10, >100 and >100 mg l-1, respectively.
Cadmium Electrode Electrode Potentiometry

"Preparation And Performance Of A Coated Tubular Solid-state Lead(II)-selective Electrode In Flow Injection Analysis"
Fresenius J. Anal. Chem. 1989 Volume 333, Issue 3 Pages 226-230
Jacobus F. van Staden

Abstract: The electrode was constructed from a Pb tube (5 mm x 1.5 mm i.d.) connected at each end to Tygon tubing and having the inner wire of a shielded cable wound around the outside to permit electrical contact with an Orion Ionalyzer instrument. The internal wall of the Pb tube was cleaned with 12 M HNO3 and then with water, and was activated by anodic deposition at 20 mA cm-2 of PbS on the inner wall while 0.1 M Na2S was passed through at 2 mL min-1. The activated electrode was conditioned by storage for 24 h in 1 mM Pb(NO3)2 (pH 3). The electrode was used with an Orion 90-02 double-junction reference electrode in a flow injection system to determine 250 mg L-1 of Pb(II) at a sampling rate of 40 h-1. Silver, Hg(II), Cu, Fe(III), I-, S2-, Br-, SO42- and phosphate interfered.
Lead(2+) Electrode Electrode Ion exchange Electrode

"Determination Of Lead In Copper-based Alloys Using A Modified Quartz Atom Trap And Flow Injection Flame Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1989 Volume 335, Issue 6 Pages 566-567
D. Thorburn Burns, N. Chimpalee and M. Harriott

Abstract: Copper alloy (0.1 to 0.5 g) is dissolved in 4 mL of concentrated HCl and 2 mL of concentrated HNO3 and the solution is diluted to 100 mL with water. A 250 µL aliquot of solution is injected into a flow of water (7.2 mL min-1) via a mixing coil (10 cm x 0.8 mm) into the described apparatus (Anal. Abstr., 1989, 51, 1B96) and aspirated at 6.9 mL min-1 into an air - acetylene flame; the absorbance is measured at 283.3 nm. The calibration graph is rectilinear up to 10 µg mL-1 of Pb. No interference is observed. The method is less sensitive (detection limit 0.13 vs. 0.09 µg mL-1) than the conventional direct aspiration method, but is faster (200 vs. 50 samples h-1), the life of the quartz tube atom trap is extended, and the necessity of cleaning of the trap is reduced.
Lead Alloy Spectrophotometry

"Design And Characterization Of Flow-through Coulometric Cells With Porous Working Electrodes Made Of Crushed Vitreous Carbon"
Fresenius J. Anal. Chem. 1992 Volume 343, Issue 7 Pages 566-575
E. Beinrohr, M. N&eacute;meth, P. Tsch&ouml;pel and G. T&ouml;lg

Abstract: Three designs (A to C) of cited cell were tested by hydrodynamic and cyclic voltammetry with 10 µM-K4[Fe(CN)6] in KCl solution Nernstian behavior and electrochemical yields of up to 100% were obtained for flow rates of 1 to 7 mL min-1. Cell A involved the Ag - AgCl reference electrode being directly merged into the flowing electrolyte, but required samples and the supporting electrolyte to have similar Cl- concentration. for reliable function. This drawback was removed in cell B, since the reference electrode was separated from the electrolyte by a porous graphite diaphragm. This cell can be used as a detector for flow injection analysis and LC and for pre-concentration. of trace metals. In cell C the counter compartment was hydrodynamically separated from the flowing electrolyte by a non-permeable, electrically conducting cation-exchange membrane (MC 3470). This cell is versatile and its potential uses include the continuous cleaning of electrolytes and electrochemical synthesis. By coating the working electrodes with Hg and removing of dissolved O the background current is reduced, especially in the cathodic region.
Ferricyanide Coulometry Electrode Electrode Voltammetry Voltammetry

"A Microwave Plasma Cavity Assembly For Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 623-625
H. Matusiewicz

Abstract: Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading echelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.
Spectrophotometry

"A Simple Procedure For The Chromatographic Analysis Of Nanoliter Samples"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 2 Pages 260-262
Rosanna Toniolo, Alan Valentino, G. Bontempelli, Gilberto Schiavon

Abstract: A simple method for the analysis of nanoliter droplets is proposed, which is profitable when larger samples cannot be collected as, for instance, in the case of several biological fluids and particularly in clinical chemistry a glass capillary associated to a micromanipulator is used to collect sub-microliter volumes which are partially transferred into transparent polymeric tubings with known internal diameters (120-178 µm), where the volumes sampled are measured by meniscus collimations with a collimator microscope at suitable magnification. Both ends of these tubings are preliminarily equipped with ferrules and fittings, so as to make them suitable for connection a the loop to a conventional high-pressure injection valve. The reliability of this procedure has been tested for the anal. of Na+, K+, and Ca2+ present in minute synthetic standard samples (10-200 nL) by a conventional ion-chromatography instrumentation. Relative standard deviations in peak area measurements (5-6%) are discussed in terms of the whole approximation affecting volume measurements, which depends on both the inconstancy of the inner diameter of the polymeric tubings employed and the uncertainty characterizing meniscus collimations. The proposed procedure can be easily extended to the determination of any organic or inorganic species present in very small samples, provided that their detection can be achieved by any chromatography approach or, more generally, by flow injection analysis.
Sodium Potassium Calcium Biological fluid

"Determination Of N-acetyl-L-cysteine By Flow Injection Potentiometry"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 6 Pages 675-678
Nj. Radi&#cacute; and J. Komljenovi&#cacute;

Abstract: A multi-purpose tubular flow-through sensor was constructed with an AgI-based membrane. The membrane was prepared by pressing silver salts (AgI, Ag2S) and powd. Teflon. This membrane was incorporated in the tubular flow-through sensor body. A 2-mm diameter hole was drilled through the center of the tubular sensor and the membrane, thus determining the active sensor volume of about 4 µL. The tubular sensor with reference electrode was placed into a complex flow injection system and used for the flow-through determination of N-acetyl-L-cysteine, (NAC), in perchloric acid medium, pH = 1. Linear dependence was established between the recorded signal height and the concentration of NAC in the injected sample. The recorded change in potential for a decade change in concentration, 62 mV {p (NAC)}-1, in the concentration range from 1 x 10^-4 to 1 x 10^-1 mol L-1, was based on the formation mechanism of the sparingly soluble deposit between silver and NAC on the surface of the sensitive part of the membrane.
N-Acetyl-L-cysteine Potentiometry Electrode Electrode

"Sequential Determination Of Tin, Arsenic, Bismuth And Antimony In Marine Sediment Material By Inductively Coupled Plasma Atomic Emission Spectrometry Using A Small Concentric Hydride Generator And L-cysteine As Prereductant"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 2 Pages 155-157
Y.-L. Feng A, H.-Y. Chen A, H.-W. Chen A, Li-Ching Tian

Abstract: A hydride generation system using a small concentric hydride generator combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) was established to determine tin, arsenic, bismuth and antimony in a marine sediment material with L-cysteine as a pre-reductant. Influences of concentrations of three kinds of acids (HCl, HNO3 and HClO4), L-cysteine, and sodium tetrahydroborate(III) as well as sodium hydroxide were investigated. The interferences from transition ions were found to be insignificant for determination of the four elements in presence of L-cysteine. Under optimized conditions the detection limits were 0.6 ng/mL for arsenic(III), 0.8 ng/mL for antimony(III), 1.7 ng/mL for tin(IV), and 1.2 ng/mL for bismuth(III). The method was applied to determine the four elements in standard marine sediment materials and the results were in agreement with certified values.
Tin Arsenic Bismuth Antimony Marine Mass spectrometry

"Amperometric Determination Of Hydrogen Peroxide With A Manganese Dioxide Film-modified Screen Printed Carbon Electrode"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 2 Pages 194-200
Klemens Schachl, Hailemichael Alemu, K. Kalcher, Helmut Moderegger, Ivan Svancara, Karel Vytras

Abstract: A carbon thick film electrode modified with an MnO2-film was investigated as an amperometric detector for H2O2 in flow injection analysis (FIA). At an operating potential of +0.48 V vs. Ag/AgCl catalytic oxidation of the analyte was exploited for amperometric monitoring. Experimental parameters, such as pH of the carrier, working potential, flow rate, and injection volume were optimized. The amperometric signals were linearly proportional to the concentration. of H2O2 in the range from 0.005-10 mg/L, showing a detection limit (3s) of 2.3 µg/L. The method was applied to the determination of H2O2 in rainwater and to a simple assay to quantify glucose in human plasma.
Hydrogen peroxide Glucose Plasma Human Rain Amperometry Electrode Electrode Electrode Sensor

"Semi-automatic Microliter Sample Injection Into An Inductively Coupled Plasma For Simultaneous Multielement Analysis"
Microchim. Acta 1982 Volume 77, Issue 5-6 Pages 423-431
Tetsumasa Ito, Eiji Nakagawa, Hiroshi Kawaguchi Contact Information and Atsushi Mizuike

Abstract: A semi-automatic microliter sample injector with an 8-way motor-driven rotary valve was constructed for a conventional pneumatic nebulizer. After a 40 mgrl sample was injected into an injection tee with a micro-syringe, nebulization and flushing the sample pathway with water followed by argon were automatically executed. An automatic peak detector/integrator was employed in each channel of a three-channel spectrometer for simultaneous multielement analysis. The relative standard deviation of the peak height for 1 µg Zr/ml was 1.7% and measuring time of one sample was about 1 min. Detection limits were 2 to 6 times higher than those in continuous feeding.
Spectrophotometry

"Photometric Flow Injection Measurements With Flow-cell Employing Light-emitting Diodes"
Microchim. Acta 1984 Volume 83, Issue 1-2 Pages 17-25
M. Trojanowicz, W. Augustyniak and A. Hulanicki

Abstract: A flow-through cell is described in which the light-emitting diode and phototransistor detector can be easily replaced according to the wavelength of measurement. The system is demonstrated by the measurement of Bi(III) as the xylenol orange complex with a diode emitting radiation at 560 nm, and by the determination of PO43- as reduced molybdophosphate with a diode emitting red light.
Bismuth Phosphate Spectrophotometry

"Laser-based Refractive-index Detection Using The Sheath-flow Cuvette"
Microchim. Acta 1986 Volume 90, Issue 5-6 Pages 351-357
Yung-Fong Cheng and Norman J. Dovichi

Abstract: Light (632.8 nm) from a linearly polarized 2-mW He - Ne laser was focused by a 2.5-cm-focal length lens to traverse an Ortho model 300-051100 sheath-flow cuvette in which the sample stream was injected along the axis of a sheath stream under laminar-flow conditions, and was detected by a 1-mm2 Si photodiode connected through a current-to-voltage converter to a digital voltmeter. The cuvette was located ~1.5 cm past the beam waist (waist spot size ~15 µm) and near the centre of the beam axis. A set of diffraction fringes was formed at the extremities of the field by interaction of the beam with the body of the cuvette, the intensity at the centre of the fringe system being markedly perturbed by the presence of the sample stream. The detection limit for a 20 µm-radius sample stream corresponded to a refractive index difference of 3 x 10^-6, i.e., ~15 pg for glycerol. Application to flow injection analysis and gradient-elution HPLC is envisaged.
Water HPLC Refractometry

"Study On Cobalt-PTFE Composite-plated Electrode And Its Electrochemical Properties"
Microchem. J. 1996 Volume 53, Issue 4 Pages 385-394
Hongding Xu, Mingzhu Zou, Qinhua Ru and Yunjing Luo

Abstract: A Ni disc electrode and a Co plate (0.196 cm2) were placed in an electroplating bath of pH 4-4.2 and 62±1°C. For the Co layer deposition, the bath contained 10.8 g CuSO4/NaCl/boric acid (10:1:1) in 40 mL water at 40 mA/cm2 and 9°C. For the Co-PTFE layer, the bath was 9.525 g CuSO4/NaCl/boric acid (3:10:1) in 30 mL water at 30 mA/cm2 and 1.5 C. The electroplating was carried out using a PAR173/179 potentiostat-coulometer. The resulting electrode surface was characterized by XPS and scanning electron microscopy. The chronoamperometric responses of this electrode to alcohols were studied. The electrode was also used in an FIA system with Ag and Pt wire reference and auxiliary electrodes, respectively. The responses to vitamins, amino-acids and monosaccharides were studied. The method was also applied to drug tablet analysis. The surfaces of the composite-plated electrode were smooth and uniform with PTFE particles embedded in the plated layer. The linear calibration graphs for fatty alcohols are given; detection limits were 1-10 mM. Calibration graphs were linear for the several biochemical compounds tested (ranges given); detection limits were from 1 µM-0.1 mM; RSD were 0.12-1.78%. Recoveries were from 95-105% vitamin B2 (riboflavine) in tablets.
Riboflavine Pharmaceutical Potentiometry Electrode

"Continuous-flow Detector For Cytochrome P-450 And Cytochrome P-420"
Anal. Biochem. 1983 Volume 132, Issue 1 Pages 26-33
R. F. Bonner, P. M. Bungay, L. R. Pohl and R. V. Branchflower

Abstract: The detector (illustrated and fully described) samples eluate from an h.p.l.c column, reduces haem proteins by reaction with S2O42-, then splits the reduced stream into two parts, one of which is caused to react with CO; the difference in absorbance between the resulting streams is measured every 5 s at 420, 450 and 490 nm. Results are calculated and recorded automatically. The detection limit for cytochrome P-450 and its degradation product (cytochrome P-420) is 30 pmol mL-1. Advantages of the method over manual methods are listed.
Cytochrome P-450 Cytochrome P-420 Blood HPLC Spectrophotometry

"A Combined Cellobiose Oxidase/glucose Oxidase Biosensor For HPLC Determination Online Of Glucose And Soluble Cellodextrines"
Anal. Biochem. 1993 Volume 214, Issue 2 Pages 389-396
Nordling M., Elmgren M., Stahlberg J., Pettersson G. and Lindquist S. E.

Abstract: Highly specific biosensors can be prepared by immobilizing flavin-containing oxidases in a redox polymer on an electrode surface. By combining one glucose oxidase and one cellobiose oxidase electrode in a flow cell we have made a sensor for flow injection analysis, or post-column quantification, of glucose, cellobiose, and higher cellodextrines in an HPLC system. Samples of different concentrations of glucose and cellobiose, separately or mixed, were injected into the mobile phase and the current response was recorded simultaneously from both electrodes. The recorded response peak heights could be used for calibration curves. The usable measuring ranges were roughly 50 µM - 50 mM for glucose and 5 µM - 80 mM for cellobiose. Soluble cellodextrines, Glc1-6, could be separated on a C18 column by isocratic elution and detected by the sensor.
Cellobiose Cellotriose Cellotetraose Cellopentaose Cellohexaose HPLC Sensor Electrode

"A Microprocessor Controlled Potentiometric Detection System"
Anal. Lett. 1982 Volume 15, Issue 12 Pages 1001-1008
Sam A. McClintock; William C. Purdy

Abstract: A potentiometric detection system is described which carries out digital signal processing, with 12-bit resolution, under microprocessor control.
HPLC Potentiometry

"Flow-through Sandwich PVC Matrix Membrane Electrode For Flow Injection Analysis"
Anal. Lett. 1985 Volume 18, Issue 18 Pages 2291-2303
S. Alegret; J. Alonso; J. Bartroli; J. L. F. C. Lima; A. A. S. C. Machado; J. M. Paulis

Abstract: A new potentiometric cell assembly is reported, in which a PVC membrane sensor is applied on a conductive silver - epoxy support. It allows simple replacement of the membrane when exhausted or substitution of the sensor system and has good mechanical and electrical stability. The sensor can be incorporated in a block with a location for the reference electrode (two examples are presented). The device was fitted with the Orion 92-07-02 NO3- sensor and its performance in flow injection analysis was studied. Results of a comparative evaluation of this sensor system in flow injection analysis and a static system involving an all-solid-state NO3--selective electrode constructed by a similar technique are included. The advantages of the proposed configuration over the usual cascade arrangement and over a tubular flow-through electrode are discussed.
Electrode Electrode Potentiometry

"Multifunction Valve For Flow Injection Analysis"
Anal. Lett. 1987 Volume 20, Issue 12 Pages 1951-1976
Jun'Ichi Toei

Abstract: A multi-function valve with six injection modes is described and illustrated. It is partly constructed from stainless steel and can be used in high-pressure analysis. The valve has the capability for simultaneous injection of sample and reagents, thus increasing utilization efficiency of materials and time. It is applied in the determination of Ca with o-cresolphthalein at 254 nm with water as carrier. The precisions obtained in various injection modes are tabulated. Generally, the coefficient of variation are <2.5% (n = 5 to 7). The valve is also suitable for use in HPLC.
Calcium o-Cresolphthalein Spectrophotometry

"Evaluation Of An Enzymic Method For Determination Of Glucose In Whole Blood Using Flow Injection Analysis With Detection By Chemiluminescence"
Anal. Lett. 1989 Volume 22, Issue 1 Pages 83-100
Petersson, B.A.

Abstract: A flow injection manifold is described and illustrated that comprises an injection valve and detection and dialysis units. Particulate matter in samples was removed by a dialysis system containing a cellulose nitrate membrane. Glucose oxidase was immobilized on spherical glass beads (75 to 125 µm diameter; pore size 0.7 µm), which were then packed into a PVC column. The H2O2 formed was detected from the chemiluminescence produced by its reaction with alkaline 1 mM luminol in the presence of K3Fe(CN)6. The optimum reaction conditions used were as previously described (Ibid., 1986, 19, 649). A home-built luminometer with two photodiodes directly facing the flow channel of the flow-through cell was used. The calibration graph was rectilinear for 0.1 to 41 mM glucose, the sampling rate was 95 h-1, and the coefficient of variation was 1.5%. The system cannot be applied satisfactorily to blood owing to sensitivity of the response to the haematocrit level. A further problem is that the pressure drop over the enzyme reactor increases with time, thereby reducing the rate of glucose transfer across the dialysis membrane.
Glucose Whole Chemiluminescence

"Development And Application Of An Immobilized Enzyme Electrode For The Determination Of Sulfite In Foods And Feeds"
Anal. Lett. 1991 Volume 24, Issue 4 Pages 551-555
Nabirahni, M.A.;Vaid, R.R.

Abstract: An electrode incorporating sulphite oxidase immobilized (by the bovine serum albumin - glutaraldehyde method) on pig intestine was developed for determining SO32-; the method involved amperometric detection of H2O2 formed in the oxidation reaction. Optimum assay conditions comprised 25 mM Tris buffer of pH 8.76 at 35°C. The linear dynamic range of the electrode was 5.5 to 500 M SO32- for the initial-rate method and 5.2 M to 1.0 mM for the steady-state method. Nitrite interfered in the determination of SO32-; relative to SO32-, the responses to HSO3- and S2O52- were 68 and 110%, respectively. Results with the electrode were well correlated (r = 0.952) with those by the reference Monier - Williams method.
Sulfite Feed Food HPIC Electrode

"Potentiometric Flow Injection Detection Of Copper(II) With A Graphite Carbon Electrode"
Anal. Lett. 1998 Volume 31, Issue 1 Pages 13-25
ZuLiang Chen; Peter W. Alexander

Abstract: A graphite C electrode was evaluated in a potentiometric flow injection system for the detection of Cu2+. The electrode response characteristics were studied by both cyclic voltammetry and potentiometry, and probably the electrode potential change results in the adsorption of Cu2+ at the electrode surface. The C electrode was used for the flow injection potentiometric detection of Cu2+ in 0.05 mol/L NaOAc-0.2 mol/L NaCl at pH of 6.0 carrier solution A linear response in concentration. range of 1 x 10^-5-1 x 10^-2 mol/L was obtained with a detection limit of 5 x 10^-5 mol/L. The electrode described in this paper is simple and low cost.
Copper(II) Sea Electrode Potentiometry

"Direct Electrochemistry Of Hemoglobin At Silver Electrode Modified By Lipoic Acid Monolayer"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2159-2171
Song Zhang; Wen-liang Sun; Wen Zhang; Katsunobu Yamamoto; Shuguang Tao; Jiye Jin

Abstract: The direct electrochemistry of Hb was studied by cyclic voltammetry (CV) and flow injection analysis (FIA) on a silver electrode modified by a self-assembled monolayer of lipoic acid (LA). Lipoic acid molecules can strongly absorb onto the Ag electrode surface through the cleavage of the S-H bond and the formation of the Ag-S bond. The observed adsorption coverage of LA demonstrates that the LA molecules spontaneously form a self-assembled monolayer. Experimental data show that LA can promote the redox process of Hb at the modified electrode surface. This chemical modified electrode (CME) exhibits good stability in the CV and FIA. Linear sweep voltammetric measurement of Hb at the CME reveals a linear relationship between the oxidative peak current and the concentration of Hb in the range of 5.0 x 10^-7 - 1.5 x 10^-5 mol/L. The relative standard derivation (RSD) for six replicate measurements of 5.0 x 10^-6 mol/L Hb in FIA is 2.8%. The detection limit is 2.0 x 10^-7 mol/L. The reaction mechanism involves the hydrogen bond/salt bridge formation between the carboxylate of LA and the protonated lysine residues of Hb that can enhance the electron transfer reaction. It can be used to detect Hb in real examples.
Hemoglobin Voltammetry Electrode Electrode

"A Simple Optical Flow Injection Ammonia Sensor"
Anal. Lett. 1998 Volume 31, Issue 3 Pages 395-410
B. Kuswandi; R. Narayanaswamy

Abstract: The optical system consisted of a 100-W quartz halogen lamp light source, modulated by an optical chopper and focussed by means of a lens onto one branch of a bifurcated optical fiber, the end of which was positioned near the surface of a non-bleeding cellulose-immobilized pH indicator strip; the other arm of the bifurcated optical fiber served to lead the reflected light to a photomultiplier tube, coupled to a current amplifier and a lock-in amplifier. The indicator strip was mounted in a flow cell equipped with a hydrophobic gas membrane to permit diffusion of the analyte. The system was used as a detector for a FIA system for the assay of ammonia, using a water carrier stream (0.75 ml/min) and a 10 mM NaOH reagent stream (0.75 ml/min). The sample solution containing ammonia was merged with the reagent stream and a 150-l portion of the mixture was injected into the carrier stream and pumped through the flow cell. The ammonia present in the mixture diffused through the gas membrane, resulting in a color change of the indicator strip; this change was monitored at 620 nm by the photomultiplier tube. Response was linear for the range 1-7 mM ammonia. The method was also applied for the assay of urea using 0.06% urease in 20 M Tris-HCl buffer of pH 7 as the carrier solution. Response was linear for 2-10 mM.
Ammonia Sensor

"Ion Transfer Across Water - Solidified Nitrobenzene Interface As Amperometric Flow Detector"
Electroanalysis 1989 Volume 1, Issue 1 Pages 75-80
Erkang Wang*, Huamin Ji

Abstract: A three-electrode thin-layer flow-through cell is described that incorporates nitrobenzene solidified by means of PVC and agar to act as the working electrode (area 7.07 mm2). The nitrobenzene phase contains also 50 mM tetrabutylammonium tetraphenylborate in order to make contact with a Ag - AgCl electrode (in aqueous solution solidified by agar containing 50 mM tetrabutylammonium chloride). Reference and auxiliary electrodes are positioned downstream of the working electrode. By using this detector, flow injection analysis was carried out to determine cations (choline, acetylcholine, tetramethylammonium, tetrabutylammonium and Cs+) and anions (ClO4-, IO4- and ReO4-). Calibration graphs were rectilinear over two orders of magnitude of concentration. (injection volume 20 µL), and detection limits ranged from 4 to 40 ng; coefficient of variation were 3.1% (n = 5, 7 or 12). The method was applied in detecting choline and acetylcholine separated on a C18 column.
Choline Acetylcholine Cesium Perchlorate Periodate Perrhenate HPLC Amperometry Electrode

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

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

"Flow Cell Based On Glucose Oxidase-modified Carbon-fibre Ultra-micro-electrode"
Electroanalysis 1989 Volume 1, Issue 2 Pages 151-154
Joseph Wang*, Ruiliang Li, Meng-Shan Lin

Abstract: Five 7 µm diameter carbon fibers were aspirated into the tip of a borosilicate-glass capillary tube (1.2 mm i.d.) and sealed with epoxy-resin; electrical contact was made by Hg and Cu wire. The electrode was modified by potentiostatic platinization (at -0.18 V vs. Ag - AgCl for 15 min) in 5 mL of solution containing hydrated H2PtCl6 (165 mg), glucose oxidase (7.5 mg) and Pb(NO3)2 (3 mg); the pH was adjusted to 3.5 with NaOH. After the co-deposition of glucose oxidase and Pt particles, the electrode was dipped for 1 h in 0.1 M phosphate buffer (pH 6.8) with stirring, and then inserted into one arm of a glass T-piece that formed the flow cell (constructional details given), with a PTFE tube as solution inlet in the other arm. The cell outlet was dipped into a downstream reservoir containing the reference and auxiliary (Pt wire) electrodes, and measurements were made 30 to 40 min after the working potential (+0.80 or +0.85 V) was applied. In flow injection analysis, the calibration graph for glucose was rectilinear from 0.1 to 1 mM, and the detection limit was 13 µM (230 ng in a 100 µL injection); the coefficient of variation (n = 40) was 3%. The electrode remained active over a 20-day period.
Glucose Electrode Electrode Electrode

"Carbon Paste Electrode Chemically Modified By Direct Admixing Of Tris-(4,7-diphenyl-1,10-phenanthroline)iron(II)"
Electroanalysis 1989 Volume 1, Issue 2 Pages 155-160
Christopher J. Hynes, Mojtaba Bonakdar, Horacio A. Mottola*

Abstract: The electrodes (radius 3 mm) were prepared by mixing tris-(4,7-diphenyl-1,10-phenanthroline)iron(II) perchlorate (I) with graphite and acetone and then adding light mineral oil. A typical paste contained 10% of I, 56% of graphite and 34% of oil. Cyclic voltammetry at the electrode with use of a BAS-100 electrochemical analyzer gave one stable Fe(III)-reduction peak at ~+1.0 V vs. Ag - AgCl and one oxidation peak at ~+1.2 V, which disappeared with successive cycling; both peaks were almost independent of pH in the range 1 to 5. The electrode (which has a low rate of loss of I by leaching) was applied in the determination of NO2 from its electrocatalytic oxidation of I in a continuous-flow system; typical coefficient of variation (n = 10) at 15 ppb (v/v) of NO2 in air were ~5%.
Nitrogen dioxide Environmental Electrode Electrode Voltammetry

"Dynamic Response Characteristics Of An Impinging-jet Amperometric Detector"
Electroanalysis 1990 Volume 2, Issue 6 Pages 463-469
Francis E. Powell, Arnold G. Fogg*

Abstract: By use of [Fe(CN)6]4- as test species an investigation was carried out to determine the dynamic response characteristics of the impinging-jet electrode described previously [cf Fogg and Summan, Analyst (London), 1984, 109, 1029]. Laminar flow from a straight delivery tube was modified by mixing stages in the electrode channel and its connections. The effective detection volume was ~7 µL and therefore the detector would not be expected to contribute significantly to overall dispersion in practical flow injection systems.
Iron(2+) hexacyanide Amperometry Electrode

"Instrument For Alternating-current Voltammetry Featuring A Digital Phase-sensitive Detector - Application To Flow Injection Analysis Using AC Amperometry"
Electroanalysis 1990 Volume 2, Issue 6 Pages 435-442
David J. Curran*, Mark B. Gelbert, Edward D. Kingsley

Abstract: The design, construction and operation are described of an instrument for a.c. electrochemical measurements on solution containing low concentration. of analyte. The unit incorporates a lock-in amplifier based on a digital phase-sensitive detector. The phase angle resolution and signal capture ratios were better than 0.01°C and as high as 80,000, respectively. Application of the instrument is demonstrated in the determination of 6 nM-o-dianisidine by flow injection a.c. amperometry.
1,2-Dianisidine Amperometry Voltammetry

"An XPS Investigation Of The Influence Of Bromide And Iodide Solutions On The Surface Of Silver Chloride Coated Ion-selective Electrodes"
Electroanalysis 1991 Volume 3, Issue 3 Pages 197-202
C. A. Strydom, J. F. van Staden, H. J. Strydom

Abstract: X-Ray photoelectron spectroscopic (XPS) data of AgCl-coated, ion-selective electrodes exposed to solutions containing high concentrations of bromide and iodide ions revealed that the surface properties of the original electrode changed. The mixed phases, AgBrsCl1-s and AgIsCl1-s, seem to form initially on the electrode surface, with the existence of the AgICl phase much shorter than that of the AgBrCl phase. This indicates that the formation of the Agl surface layer is kinetically faster than the formation of the AgBr layer. In both cases XPS data showed the ultimate formation of AgBr and AgI layers on top of the original AgCl-coated, ion-selective electrode surface after being subjected to solutions containing either bromide or iodide ions. The conversion of the crystalline-coated, chloride-selective electrode surfaces to AgBr and AgI layers, however, transformed the chloride-selective electrodes into bromide- or iodide-selective electrodes with electrode properties different from those of the original electrode.
Electrode

"Convection-independent Detection With Voltammetric Single Micro-disc Electrodes"
Electroanalysis 1992 Volume 4, Issue 4 Pages 501-506
Frank-Michael Matysik, Hendrik Emons

Abstract: The design and construction are described of a new electrochemical flow cell incorporating a Pt micro-disc electrode that is positioned inside a narrow tube facing into the flowing stream. In experiments with ferrocene as model analyte and 0.1 M tetrapropylammonium perchlorate in acetonitrile as supporting electrolyte, it was shown that the flow rate dependence of the voltammetric signal was reduced as the electrode diameter was decreased from 114 µm, the limiting case being obtained at an electrode diameter of 0.7 µm. However, limits of detection were higher at electrodes smaller than 38 and 8 µm in diameter for continuous-flow and flow injection conditions, respectively. It is concluded that the optimum electrode size needs to be selected with respect to the analytical demands, i.e., the concentration. range of interest and convective characteristics of the experimental system.
Ferrocene Voltammetry Electrode Electrode

"A Solid Polymer Electrolyte Amperometric Detector For FIA And HPLC With Mobile Phases Of Low Conductivity"
Electroanalysis 1992 Volume 4, Issue 4 Pages 447-451
Luk&aacute;s Loub, Frantisek Opekar, Vera Pac&aacute;kov&aacute;, Karel Stul&iacute;k

Abstract: The design, construction and operation are described of a flow-through amperometric cell with a small Pt-wire working electrode and sub µL geometric volume and wherein the counter, working and reference electrodes are electrolytically connected by means of a Nafion solid polymer electrolyte. The cell was tested in a flow injection system with use of quinolin-8-ol (I), 4-methylcatechol (II) and K4Fe(CN)6 as model analytes. Calibration graphs were rectilinear from 0.2 to 0.6 µM up to 100 µM. In the determination of I at the 10 and 100 µM levels the coefficient of variation were 4.3 and 1.1% respectively (n = 10). Electrode activity decreased by 10 to 15% during a day's use but this could be restored by cyclic polarization of the working electrode between +1.6 and -0.2 V (vs. Ag - AgCl) for 15 min at 50 mV s-1. The detector has been applied in the HPLC determination of I, catechol and II on a Separon SGX C-18 column (15 cm x 3 mm) with aqueous 4% dioxan as mobile phase. AB An amperometric cell with a small platinum wire working electrode, a submicroliter geometric volume, and a solid polymer electrolyte (Nafion) was constructed and tested. The cell permits sensitive and reliable detection even in mobile phases of negligible elec. conductivity, (e.g., distilled water or nonpolar organic solvents). The sensitivity is substantially higher than that attained with similar cells containing large-area working electrodes; typical limits of detection amt. to analyte concentrations. between 10^-7 and 10^-6 mol/L, corresponding to subnanogram amounts in common HPLC sample volumes The detector response exhibits satisfactory linearity, a linear dynamic range of at least three concentration. decades, and a good precision, with relative standard deviations of 1 to 5%. This cell substantially widens the possibilities of amperometric detection, permitting direct application, for example, to normal-phase HPLC or to methods with programmed composition of the mobile phase (gradient elution).
8-Quinolinol 4-Methylcatechol Ferricyanide Amperometry Electrode HPLC

"A Reticulated Vitreous Carbon Spectroelectrochemical Detector For Flow Injection Analysis And Liquid Chromatography"
Electroanalysis 1992 Volume 4, Issue 4 Pages 487-493
Janet Weiss Sorrels, Howard D. Dewald

Abstract: The design, construction and operation are described of a spectroelectrochemical detector, with a 1 cm optical path length, that incorporates an optically transparent reticular vitreous-carbon working electrode (cf. Dewald and Wang, Anal. Chim. Acta, 1984, 166, 163) which can easily be replaced in the event of electrode fouling. In the determination of [Fe(CN)6]3- by a flow injection procedure, with spectrophotometry at 410 nm, the calibration graph was rectilinear in the range 4 to 100 µM and the limit of detection was ~2 µM. Application of the detector in LC is exemplified by the analysis of a mixture of phenol, chlorophenols and nitrophenols. A spectroelectrochemical detector for flow injection and liquid chromatography is described. The detector design has dimensions of a standard 1 cm sample cuvette with a replaceable reticulated vitreous carbon working electrode. No special cell holder or modifications to the spectrophotometer are required to use the detector. Chronocoulometry is used to indicate a trend from thin-layer behavior toward semi-infinite diffusion behavior as the electrode pore size increases. Ferro-/ferricyanide solutions were used to evaluate the flow injection characteristics of the detector. A sampling rate of 180 injections per h was used. Linear calibration curves in the micromolar range were achieved with a reproducibility of 2-7%. A mixture of phenol, chlorophenols, and nitrophenols was used to investigate the simultaneous electrochemistry and optical response for liquid chromatography
Phenols Phenols, chloro Phenols, nitro Spectroelectrochemistry Electrode

"Amperometric Response Of Mediating Layers On Electrode Surfaces To Gaussian Concentration Profiles In Flowing Streams"
Electroanalysis 1992 Volume 4, Issue 8 Pages 751-756
John F. Cassidy, William Breen, Anthony McGee, Johannes G. Vos, Michael E. G. Lyons

Abstract: A model is presented for a semi-porous layer containing catalytic sites, coated on an electrode and used for the mediation of analytes. The coated electrodes are applicable as detectors in flow injection analysis or HPLC. Thin layers with high catalyst loading and high rates of electron exchange led to rectilinear graphs of peak current vs. concentration. for chemically modified electrodes in flowing streams. A model for a layer, containing catalytic centers, coated on an electrode and used for the mediation of analyte in a flowing stream is proposed and solved. The model applies to a situation of a Gaussian concentration. profile of analyte impinging on the outer edge of the mediating layer. The important parameters that limit the current magnitude are the diffusion coefficient of the analyte through the layer, the effective electron diffusion coefficient through the layer, and the rate of reaction between the mediator and the analyte. Literature data showed that layers, high catalyst loading, and high rates of electron exchange lead to linear peak current height vs. concentration. plots.
Electrode Electrode Amperometry

"Kinetic Studies On Membraneless Amperometric Biosensors Prepared From Xanthine Oxidase, Organic Conducting Salt, And Silicone Oil"
Electroanalysis 1994 Volume 6, Issue 4 Pages 305-315
Ulrich Korell, Ursula E. Spichiger

Abstract: A rotating disc electrode (4 mm diameter) based on Kel-F tubing filled with a tetrathiafulvalene-p-tetracyanoquinodimethane (TTF-TCNQ)/Si oil paste (5:8) mixed with xanthine oxidase (15:1), was combined with a Ag/AgCl reference electrode and a Pt wire counter electrode to form an amperometric biosensor. The response to hypoxanthine in pyrophosphate buffer was described by the enzyme-kinetic Michaelis-Menton formalism with good correlation from -100 to +300 mV at pH 6.1-8.8. Xanthine oxidase was oxidized by at least-two mediator species by a homogenous mechanism. The sensor could be operated in air-saturated solution, and operation in flow analysis systems is recommended. The calibration graphs were linear for up to 3 µM-hypoxanthine and the detection limit was ~10 nM. The response time was ~10 s. Ascorbate did not interfere for measurements made at 9 Hz, -75 mV and pH 6.7. The sensor paste was stable for 3 months at -30°C.
Hypoxanthine Sensor Electrode Electrode Amperometry

"Amperometric Biosensors For Detection Of L- And D-amino-acids Based On Co-immobilized Peroxidase And L- And D-amino-acid Oxidases In Carbon-paste Electrodes"
Electroanalysis 1994 Volume 6, Issue 5-6 Pages 381-390
V. Kacaniklic, K. Johansson, G. Marko-Varga, L. Gorton, G. J&ouml;nsson-Pettersson, E. Cs&ouml;regi

Abstract: Graphite powder (0.1 g), previously heated at 700°C for 15 s and cooled, was added to a solution of 1 mg each of horse-radish peroxidase and an L- or D-amino-acid oxidase in 0.1 M phosphate buffer of pH 7.0 to which a 0.1% volume of aqueous PEI was then added. The mixture was set aside at 4°C for 2 h and then dried under reduced pressure for 4.5 h, and a paste was formed by addition of 40 µL of paraffin oil and packed to a depth of 3-4 mm in the tip of a 1 mL plastic syringe barrel otherwise filled with non-enzyme-containing carbon paste. The resulting biosensors were used (-50 mV vs. Ag/AgCl) in a flow injection system with 0.1 M phosphate buffer of pH 8.0 as carrier (0.6 ml/min); the responses relative to that for phenylalanine are tabulated for 18 common L-amino-acids. Calibration graphs are also shown, that for H2O2 being slightly curvilinear up to 0.5 mM and those for L-tryptophan, -leucine, -isoleucine, -tyrosine and -phenylalanine up to 5 mM (injection volume 50 µL). Results for analogous D-amino-acid biosensors are also presented.
Amino acids, L Amino acids, D l-Tryptophan l-Leucine l-Isoleucine Tyrosine l-Phenylalanine Sensor Amperometry Electrode

"Flow Characteristics Of A Versatile Wall-jet Or Radial-flow Thin-layer Large-volume Cell For Electrochemical Detection In Flow-through Analytical Systems"
Electroanalysis 1997 Volume 9, Issue 1 Pages 32-39
Beno&icirc;t Soucaze-Guillous, Wodzimierz Kutner

Abstract: Several previously used cell designs were incorporated into the cited 35 mL amperometric or voltammetric cell (diagram and description given). The cell had an interchangeable disc, ring-disc and microdisc working electrodes, a NaCl-saturated Ag/AgCl reference electrode, a Pt wire auxiliary electrode, interchangeable flat and conical inlet capillary nozzles and a micrometer screw for adjusting the distance between the inlet and working electrode (>=10 µm). The operating mode of the cell (radial-flow, wall-jet or wall-tube) was chosen by inserting an appropriate working electrode and inlet nozzle, and adjusting the gap between the nozzle and the working electrode. The flow characteristics of the cell were studied using a 4 mm diameter Ag, a 10 µm diameter Pt and a Au-Au ring-disc working electrode. The cell was used to detect nitrophenol and aniline isomers after analytical and microbore HPLC and for the electrocatalytic FIA detection of benzyl alcohol (conditions given). The cell may also be useful in the wall-jet configuration for HPLC post-column derivatization and detection. The advantages and some other possible uses of the cell are discussed.
Aniline Phenols, nitro Alcohols HPLC Amperometry Voltammetry Electrode

"Evaluation Of A New Wall-jet Flow-through Cell For Commercial Ion-selective Electrodes In Flow Injection Potentiometry"
Electroanalysis 1997 Volume 9, Issue 2 Pages 179-182
Lucy Tina Di Benedetto, Telis Dimitrakopoulos*

Abstract: The cited poly(methyl methacrylate) cell (28 x 25 x 35 mm) which can accommodate commercial gas-sensing, liquid polymer membrane and solid-state-based ISE is described (diagram given). The cell contains a 1 mm i.d. Ag/AgCl wire reference electrode and the dead volume of the ISE compartment is 18 µL. Two separate inlets and flow channels are used to carry the sample and reference solutions to the ISE and reference electrode, respectively, after which the streams are merged and carried to waste. The analysis rate was up to 240 samples/h and injection volumes >=50 µL are recommended. An Orion 95-12 ammonia ISE was used in the cell with a sample injection volume of 100 µL and 1 M KOH/1 µM-NH4Cl and 1 M KCl as carrier and reference solutions, respectively, e.g., at total flow rate of 1.8 ml/min. Calibration graphs of potential vs. log. NH3 concentration were linear for 0.1-10 mM NH3 and peak height RSD were 0.4-3.5%. The flow cell was also used to determine Ca and iodide using appropriate ISE.
Ammonium Calcium(2+) Iodide Potentiometry Electrode Electrode

"Electrochemical Oxidation And Determination Of Heparin At Electrodes Modified With Ruthenium Oxide Or Copper Oxide"
Electroanalysis 1997 Volume 9, Issue 9 Pages 675-684
Krzysztof Lewinski, Yun Hu, Charles C. Griffin, James A. Cox

Abstract: The electrochemical oxidation of full-size heparin (13-15 kDa) is demonstrated in 1 M H-3PO-4 at a glassy carbon electrode coated with a ruthenium oxide film. The pathway apparently is analogous to chemical oxidation by periodate. By comparison to currents from inorganic species. it is apparent that only about 2 electrons per mole are involved. Flow injection analysis (FIA) allowed determinations down to 2 µM heparin, but the calibration plot was nonlinear. Low molecular weight heparin (5-6 kDa) was not electroactive with this system. In basic solution at a glassy carbon electrode that is modified with a film of Cu-2O, both full-size and low molecular weight heparin are oxidized. The pathways involved oxidative desulfation and attack on saccharide units with evolution of CO-2. Linear calibration plots which extended into the sub µM level were obtained by FIA. The detection limits, which were based on a value of 3 for the ratio of the signal to the standard deviation of replicates, were 9 nM for full-size and 20-30 nM for various low molecular weight heparin samples.
Heparin Electrode Electrode Potentiometry

"Graphite-Teflon-peroxidase Composite Electrodes"
Electroanalysis 1997 Volume 9, Issue 14 Pages 1113-1119
Maria Antonia del Cerro, Gabriela Cayuela, A. Julio Reviejo, Jose M. Pingarr&oacute;n *, Joseph Wang

Abstract: The performance of graphite-70% Teflon-peroxidase-ferrocene composite electrodes, fabricated by simple physical inclusion of the enzyme and the mediator into the bulk of a graphite-Teflon matrix, by using both batch and flow injection modes, is reported. The electrode responds very rapidly to changes in H2O2 concentration due to the absence of a membrane barrier on the electrode surface and of a covalent attachment of the enzyme to graphite. The composite enzyme electrode showed a long-term operation due to the renewability of its surface by polishing. Reproducible amperometric responses were achieved with different electrodes fabricated from different composite matrices, and no significant loss of the enzyme activity was observed after seven months of dry-storage at 4°C. A bienzymatic graphite-70% Teflon-peroxidase-glucose oxidase-ferrocene electrode has been developed, too, showing a rapid response to the changes in the glucose concentration. The stability of the bienzymatic composite electrode was similar to that of the peroxidase biosensor. This biosensor was applied to the determination of glucose in must and wine samples by batch amperometry and flow injection with amperometric detection modes.
Glucose Wine Must Amperometry Electrode Sensor Electrode Electrode

"Critical Comparison Of Paraffin Carbon Paste And Graphite-poly(tetrafluorethylene) Composite Electrodes Concerning The Electroanalytical Behavior Of Various Antioxidants Of Different Hydrophobicity"
Electroanalysis 1998 Volume 10, Issue 1 Pages 33-38
Emilia Diego, Lourdes Ag&uuml;i, Araceli Gonz&aacute;lez-Cort&eacute;s, Paloma Y&aacute;nez-Sedeno, Jos&eacute; M. Pingarro&oacute;n, Jean-Michel Kauffmann

Abstract: The voltammetric and flow injection amperometric behaviors of several substances used as antioxidants in the food and pharmaceutical industries at carbon paste electrodes, with paraffin as binding agent, and at graphite-40% PTFE composite electrodes were compared on the basis of the different hydrophobicity of the antioxidants. Aqueous solutions, alcohol-water mixtures and oil-in-water-emulsions were used as working media. No voltammetric or flow injection responses were obtained for high hydrophobic antioxidants (BHT, Irganox-1076 and Irganox-1010) at graphite-PTFE electrodes. On the contrary, carbon paste electrodes allowed the attainment of analytically useful signals for these compounds. A pulse amperometric detection (PAD) scheme should be applied in these cases for the cleaning of the electrode surface. The use of graphite-PTFE electrodes seems to be advantageous for the less hydrophobic antioxidants such us propyl gallate and TBHQ. An adsorption process for PG and a faster electrode kinetic in the case of TBHQ were shown to occur by cyclic voltammetry at the PTFE composite electrode. Furthermore, this electrode allows the use of lower potentials for the amperometric detection of these compounds than the carbon paste electrode. Good reproducibility of the successive amperometric responses was also observed. The mutual influence of the electrode surface composition and the lipophilic characteristics of the molecules tested is discussed.
Irganox 1076 Irganox 1010 Cresol, 4-, 2-6-di-tert-butyl Amperometry Electrode Electrode

"Microporous Gold Electrodes As Combined Biosensor/electrochemical Detectors In Flowing Streams"
Electroanalysis 1998 Volume 10, Issue 3 Pages 157-162
Michael W. Ducey Jr., Mark E. Meyerhoff

Abstract: Microporous gold electrodes are described for use as flow-through biosensor/electrochemical detectors in both flow injection analysis (FIA) as well as post-column detection in HPLC. Electrodes prepared by the covalent immobilization of tyrosinase onto the electrode surface (via a chemisorbed layer of thioctic acid and polylysine) are used to demonstrate the utility of the electrode. Such electrodes are shown to respond to a variety of substituted phenols under FIA conditions at applied potential of only -50 mV (vs. Ag/AgCl). Detection limits of 0.5 µM catechol and 3.4 µM phenol were achieved with a sample throughput rate of 38 samples/h. The electrode is shown to be stable for up to 14 days of use. The porous bioelectrode is shown to be useful as a post-column detector for substituted phenols following their separation by HPLC. Various techniques for immobilization of the enzyme onto the electrode surface (covalent and noncovalent) as well as factors affecting sensitivity and through-put (buffer ionic strength and addition of organic modifier) are discussed.
Electrode Sensor Electrode

"Electrostatically Assembled Films For Improving The Properties Of Tetraruthenated Porphyrin-modified Electrodes"
Electroanalysis 1998 Volume 10, Issue 7 Pages 467-471
Carla M.N. Azevedo, Koiti Araki, L&uacute;cio Angnes, Henrique E. Toma

Abstract: Modified electrodes, suitable for use in flow injection anal., were obtained by the electrostatic assembly of films constituted by 2 different porphyrins, namely, µ-meso(tetrapyridyl)porphyrinatecobalt(III)tetrakis[bis(bipyridine)(chloro)ruthenium(II)] and meso-tetra(4-sulfonatephenyl)porphyrinatezinc(II), forming alternating layers onto glassy carbon surfaces. The films were studied by cyclic voltammetry and proved to be strongly adherent and highly stable. They could be used for at least a week without loss of sensitivity. In addition, they exhibit an enhanced amperometric response and good protection against fouling, e.g., by phenol oxidation products. Their usefulness in flow injection analysis of NO2- and SO32- was demonstrated. Excellent signal to noise ratios were obtained for SO32- down to 10^-6 mol/L, and for NO2- down to 10^-7 mol/L.
Sulfite Nitrite Amperometry Electrode Electrode

"Use Of Prussian Blue/conducting Polymer Modified Electrodes For The Detection Of Cytochrome C"
Electroanalysis 1998 Volume 10, Issue 7 Pages 472-476
W. Lu, G.G. Wallace *, A.A. Karayakin

Abstract: The development and utilization of a Prussian blue/conducting polymer composite electrode was investigated. The introduction of a layer of conducting polymer (polypyrrole) enhanced the electroactivity of the outer Prussian blue film. This was used for improved signal generation for the redox protein cytochrome c. The effect of the thickness of these 2 film coatings and buffer solution pH was investigated. The anal. utility was demonstrated using flow injection anal.
Cytochrome C Electrode Electrode Sensor

"Determination Of Codeine In Human Plasma And Drug Formulation Using A Chemically Modified Electrode"
Electroanalysis 1998 Volume 10, Issue 8 Pages 536-540
Jyh-Myng Zen*, Ming-Ren Chang, Hsieh-Hsun Chung, Ying Shih

Abstract: Both flow injection methodology and square-wave voltammetry were developed and evaluated for determining codeine in human blood plasma and pharmaceutical formulations using a Nafion/Ru oxide pyrochlore chemical modified electrode. Combining the electrocatalytic function of the Ru oxide pyrochlore with charge-exclusion and the pre-concentration features of Nafion perform well in codeine detection. Compared to a bare glassy C electrode, the chemical modified electrode exhibits a shift of the oxidation potential in cathodic direction and a marked enhancement of the current response. A linear calibration plot is obtained over the 0-32 µM range in 0.05 M HClO4 solution with a detection limit (3s) of 10 nM in the square-wave voltammetric method. While, in flow injection anal., a linear calibration plot is obtained over the 0.5-40 µM range with a detection limit of 0.86 ng. Quant. anal. was performed by the standard addition method for codeine content in human plasma and a commercial available drug.
Codeine Plasma Human Pharmaceutical Electrode Electrode Voltammetry

"Selective Determination Of Methylmercury By Flow Injection Fast-scan Voltammetry"
Electroanalysis 1998 Volume 10, Issue 13 Pages 926-930
Rebecca Lai, Eva L. Huang, Feimeng Zhou *, David O. Wipf

Abstract: A simple flow injection system, suitable for solution flow rates at microliters-per-minute, was combined with fast-scan voltammetry for selective determination of MeHg+. A thin Hg film was formed at a Pt microelectrode prior to the measurement. Detection of MeHg+ is carried out by measuring the oxidation of MeHg radicals that were generated at the Hg microelectrode. At slow scan rates, the electrogenerated MeHg radicals undergo a follow-up dimerization reaction to form M2Hg2 (ErCi2 mechanism). At fast scan rates, MeHg radicals can be quantitatively reoxidized (reversible electron-transfer). Optimization of the experimental conditions of the system was performed based on studies of the relationship between the scan rate and the dimerization rate of the MeHg radical. Under optimized conditions, detection level of sub-nanomole was obtained with a sample consumption <10 µL, and the concentration. detection limit for MeHg+ at 50 V/s was estimated to be ~0.56 µM. To demonstrate the applicability of this method to automatic analysis, repetitive fast-scan cyclic voltammetry was conducted in conjunction with multiple sample injections. Determination of MeHg+ in the presence of excess inorganic Hg was also conducted. This approach to MeHg+ determination was successfully applied to the analysis of elevated dogfish muscle samples.
Methylmercury ion Dogfish Fish Tissue Voltammetry Electrode Electrode

"A Novel Assembly For Perfluorinated Ion-exchange Membrane-based Sensors Designed For Electroanalytical Measurements In Nonconducting Media"
Electroanalysis 1998 Volume 10, Issue 14 Pages 942-947
Rosanna Toniolo, Nicola Comisso, Gino Bontempelli *, Gilberto Schiavon, Stefano Sitran

Abstract: A perfluorinated ion-exchange membrane-based sensor suitable for electroanal. measurements in electrolyte-free media is described, which was assembled following a novel design enabling an easier preparation procedure. It was fabricated by inserting the terminal portion of a working Pt wire electrode into a Nafion tubing of suitable diameter and welding the wire thus wrapped to the bottom of a cell body by an insulating epoxy resin. The remainder upper part of the working electrode was covered by a Teflon tubing to avoid the elec. contact with the internal electrolyte introduced into the cell body, which was equipped with a counter and a reference electrode. As a result of this configuration, the actual working-electrode surface is the wire circumference contacted by the polyelectrolyte material at the bottom of the assembly which is exposed to the sample. The performance of this sensor was tested by cyclic voltammetry, amperometric monitoring and flow injection analysis for the electroanal. of a series of prototype analytes either dissolved in electrolyte-free water (H2O2, hydroquinone, ferricyanide, I- and Br-) or present in N2 atmospheres (triethylamine and O2). Detection limits for these analytes were estimated (s = 3), together with the corresponding ranges within which the responses display a linear dependence on the analyte concentration. The novel assembly is suitable only for the anal. in electrolyte-free liquid samples, while for the anal. of gaseous atmospheres, especially for flowing gases, ion-exchange membrane sensors prepared by the more usual procedure based on the use of working electrode materials embedded into a moist polyelectrolyte membrane should be preferred.
Hydrogen peroxide Hydroquinone Ferricyanide Iodide Bromide Triethylamine Oxygen, molecular Sensor Ion exchange 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

"Mytilus Edulis Adhesive Protein (MAP) As An Enzyme Immobilization Matrix In The Fabrication Of Enzyme-based Electrodes"
Electroanalysis 1998 Volume 10, Issue 17 Pages 1193-1199
Coralie Saby, John H.T. Luong

Abstract: A simple enzyme immobilization technique using an adhesive protein isolated from Mytilus edulis blue mussels was optimized for constructing a glucose oxidase (GOD) based electrode. Owing to the presence of 10^-15% of 3,4-dihydroxyphenylalanine residues, the mussel adhesive protein (MAP) was easily oxidized to form a stable protein film on Pt, Au, and glassy C electrodes. Covalent attachment of glucose oxidase to adhesive protein modified electrodes was attained since the oxidized form of the L-Dopa moieties was very reactive towards various compounds containing amino, alcohol, and thiol groups. Glucose detection was performed using MAP/GOD modified electrodes at +0.8 V in 0.1 M phosphate buffer, pH 5. Pt modified electrodes (Pt/MAP/GOD) exhibited a considerably higher sensitivity (1.28 µA/mM) in comparison to its Au (Au/ MAP/GOD, 2.92 nA/mM) or glassy carbon (GC/MAP/GOD, 2.62 nA/mM) counterparts. Tetrachloro-1,4-benzoquinone (TCBQ), an oxidation product of pentachlorophenol, was detected using MAP/GOD modified electrodes at +0.45 V, in a deaerated 0.1 M tartaric acid buffer, pH 3.5 containing 40 mM glucose. In steady state, the current response of the Au/MAP/GOD electrode was higher (6.62 nA nM-1 cm-2, t95≈83 s, 5 nM) than the GC/MAP/GOD electrode (3.78 nA nM-1 cm-2, 8 nM). In flow injection analysis, GC/MAP/GOD electrodes exhibited a linear response for TCBQ ranging from 10 nM to 1 µM (3.96 nA nM-1) with a detection limit of 10 nM. The modified glassy C enzyme based electrode retained 90% and 87% of its activity after 150 and 250 repeated injections.
tetrachloro-1,4-benzoquinone Electrode Electrode Electrode Electrode

"Electrocatalysis And Amperometric Detection At A Ruthenium-modified Indium-hexacyanoferrate Film Electrode"
Electroanalysis 1998 Volume 10, Issue 17 Pages 1163-1167
Tommaso R.I. Cataldi, Giuseppe E. De Benedetto, Alfonso Bianchini

Abstract: The electrocatalytic activity of a glassy carbon electrode modified with electrochemically deposited indium(III)-hexacyanoferrate (InHCF) film, which was subsequently cycled in a solution of Ru(III), is described. Although the resulting Ru-modified InHCF thin film electrode behaves in a manner analogous to the parent InHCF film, its stability was improved. Such a modified electrode was characterized, in acidic (pH 2) 0.5 M KCl solutions, by cyclic voltammetry, and FIA. It exhibits a high catalytic activity for the electrooxidation of some inorganic and organic compounds of anal. interest, such as As(III), S2O32-, cysteine, and 2-furaldehyde. The anal. applicability of this novel ruthenium-modified InHCF film electrode for the amperometric detection in flowing streams is discussed. Repetitive sample injections with amperometric detection of S2O32- at +0.8 V (vs. Ag/AgCl) as applied potential produced a stable response over 8 h of operation, making it very attractive for practical applications.
Arsenic(3+) Sulfite Cysteine 2-Furaldehyde Amperometry Electrode

"Horseradish Peroxidase Immobilized Electrode For Phenothiazine Analysis"
Electroanalysis 1998 Volume 10, Issue 18 Pages 1241-1248
Christine Petit, Kazuo Murakami, Arzum Erdem, Emrah Kilinc, Gemma Ortiz Borondo, Jean-Fran&ccedil;ois Liegeois, Jean-Michel Kauffmann

Abstract: A horseradish peroxidase (HRP) immobilized carbon composite electrode has been developed for the amperometric study of phenothiazine analogs. Flow injection analysis and batch experiments have been realized in acetate buffer in the presence of hydrogen peroxide. Cyclic voltammetry and amperometry using a thin-layer flow cell (dual configuration, serial mode) have permitted one to suggest the mechanisms governing the biosensor signal at -0.1 V (vs. Ag/Ag+), in the presence of hydrogen peroxide, by addition of a phenothiazine derivative It was inferred that electron transfer mediation by the phenothiazine occurred at HRP/graphite adsorbed sites, in addition to peroxidn. by dispersed HRP with substrate recycling at the graphite array-like structure of the biosensor. Thanks to these processes, high sensitivities were achieved especially in batch configurations, with amperometric detection capabilities down to 10^-8 M in acetate buffer pH 4.7. Application of the biosensor to the determination of phenothiazines in drug formulations were realized.
Drugs Phenothiazine Pharmaceutical Electrode Electrode Amperometry Sensor

"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

"Electrocatalytic Oxidation Of NADH In Flow Analysis By Graphite Electrode Modified With 2,6-dichlorophenolindophenol Salts"
Electroanalysis 1998 Volume 10, Issue 18 Pages 1261-1268
Ageliki B. Florou, Mamas I. Prodromidis, Miltiades I. Karayannis, Stella M. Tzouwara-Karayanni

Abstract: The preparation of a 2,6-dichlorophenolindophenol (DCPI) modified graphite electrode is described. DCPI was immobilized by physical adsorption onto a plain graphite electrode (DCPI-CME) and onto graphite electrodes pretreated with La(NO3)3 (DCPI-La-CME) or Th(NO3)4 (DCPI-Th-CME). The electrochemical behavior of DCPI-CME was extensively studied using cyclic voltammetry. The electrochemical redox reaction of DCPI was reversible at low coverage with E0 = 55 mV (vs. Ag/AgCl/3 M KCl) at pH 6.5. A pKa value of 5.8±0.1 for immobilized form of DCPI was determined from the intersection of the lines in the plot E0 vs. pH. The current Ip has a linear relationship with the scan rate ≤1200 mV s-1, which is indicative for very fast electron transfer kinetics. The calculated value of the standard rate constant is k0 = 18±4 s-1. No decrease of either the anodic or the cathodic current of the cyclic voltammogram was observed after 500 runs of successive sweeps. The influence of the morphology of the electrode surface on the electrochemical behavior of the DCPI-CME was studied and a mathematical model was proposed, which describes the dependence of the geometrical area of the electrode surface on the grit of the emery paper. The modified electrodes were mounted in a flow injection manifold, poised at +60 mV (vs. Ag/AgCl/3 M KCl) and a catalytic current due to the oxidation of NADH was observed reducing thus the oxidation overpotential of NADH for ≈400 mV. Interference from various reductive species present in real samples was investigated. RSD was 1.2% (n = 10 for 0.1 mM NADH). The possible biosensor showed good operational and storage stability.
Nicotinamide adenine dinucleotide oxidized Electrode Electrode Voltammetry

"Rapid Separation And Measurement Of Rat Urinary Kallikrein By High Performance Liquid Chromatography With A Continuous-flow Enzyme Detector"
J. Chromatogr. A 1983 Volume 264, Issue 2 Pages 249-257
Yoshihiko Funae, Hiroko Akiyama, Susumu Imaoka, Masanori Takaoka and Shiro Morimoto

Abstract: A prepared urine sample or the partially purified urinary enzyme was subjected to anion-exchange HPLC at 20°C to 25°C on a column (30 cm x 4 mm) of IEX-540 DEAE SIL (5±1 µm) with gradient elution by 1 M Na acetate in 0.02 M Tris - acetate (pH 7.5) at 0.7 mL min-1. The eluate was collected in a PTFE helical coil, and either the peptidase activity was continuously measured with use of N-(4-methylcoumarin-7-yl)prolylphenylalanylargininamide or the esterase activity was continuously measured with use of N2-tosyl-L-arginine methyl ester as substrate and fluorimetric detection. Gel-permeation HPLC on two columns of TSK-GEL G3000SW, with 0.05 M sodium phosphate buffer (pH 7.5) - 0.1 M NaCl as mobile phase (0.5 mL min-1) was also used to separate kallikrein before its activity was measured; confirmation of identity was by the inhibitory effect of aprotinin. The detection of peptidase activity was more sensitive than that of esterase activity.
Kallikrein Urine HPIC

"Novel Coulometric Detector For High Performance Liquid Chromatography"
J. Chromatogr. A 1983 Volume 281, Issue 1 Pages 59-71
Bunji Hagihara, Katsuyuki Kogoh, Makoto Saito, Setsuko Shiraishi, Tadao Hashimoto, Kunio Tagawa and Hiroshi Wada

Abstract: The detector consisted of a vitreous-carbon plate, mounted in a plastic block fitted with one inlet and two outlet tubes and separated from a porous glass plate by a spacer of polypropene film (30 µm), a portion of which was removed to allow the HPLC eluate to flow between the plates as a very thin layer. Above the glass plate, also mounted in a plastic block, was an electrolyte chamber containing reference and auxiliary electrodes. The detector was tested for catecholamines separated by HPLC on an ion-exchange column (6 µm IEX-510) with formate buffer solution of pH 4 (1 mL min-1) as mobile phase. The response was rectilinear in the range 0.01 pmol to 1 nmol of catecholamines injected, with detection limits of ~10 fmol. The detection limit was 1 fmol in a continuous-flow injection system. The detector was ~1000 times as sensitive as u.v. detection at 280 nm. Further improvement in sensitivity would be attained with a more uniform flow rate.
Catecholamines HPLC Electrode Coulometry

"Continuous-flow Nuclear Magnetic Resonance"
J. Chromatogr. A 1985 Volume 346, Issue 1 Pages 17-24
Klaus Albert, Michael Nieder, Ernst Bayer, and Manfred Spraul

Abstract: The effect of the volume of the detector flow cell upon peak broadening in HPLC with NMR detection was monitored by using a Biotronik fluorescence detector modified to allow different types of flow cell to be adjusted in the beam. The results of solvent-resonance suppression by using the 1331 hard-pulse suppression technique (Hore, J. Magn. Reson., 1983, 54, 539) are described and the possibility of obtaining 13C distortionless enhancement by polarization transfer spectra in the flow system is demonstrated.
HPLC Nuclear magnetic resonance

"Belt-speed Programming, A New Technique For Peak Compression In Liquid Chromatography - Mass Spectrometry And Supercritical-fluid Chromatography - Mass Spectrometry With Moving-belt Interfaces"
J. Chromatogr. A 1989 Volume 474, Issue 1 Pages 275-283
E. R. Verheij, G. F. La Vos, W. M. A. Niessen and U. R. Tjaden, J. van der Greef

Abstract: Belt-speed programming was applied for peak compression and to increase the analyte mass flow into the mass spectrometer. HPLC was carried out in flow injection mode without a chromatographic column. The mobile phase was methanol (0.2 mL min-1) with cholesterol as the test compound. SFC was carried out on a column (15 cm x 4.6 mm) of Rosil C18 (8 µm) with a mobile phase (2 mL min-1) of CO2 containing 2% of methanol. Diuron was used as a test compound. The belt speed was regulated between 1.0 and 4.5 cm s-1, and the spectrometer was used in the EI mode (70 eV). Sensitivity was improved.
Cholesterol Mass spectrometry SFC HPLC

"Trapping System For Trace Organic Volatiles"
J. Chromatogr. A 1991 Volume 586, Issue 2 Pages 315-322
Tom&aacute;s Jurs&iacute;k, Karel Str&aacute;nsk&yacute;* and Karel Ubik

Abstract: A technique is described for the collection and concentration of volatile compounds produced by plants, animals and other materials which is a modification of the continuous-flow system based on absorption of volatiles in a low amount of solvent at low temp (cf. 'Proceedings of a Conference on Insect Chemistry and Ecology Tabor, Aug 12-18, 1990', Hrdy (Ed.), Academia, Prague, 1991, p.327). The trapping device (illustrated) works offline and the concentrated analytes are analyzed by GC (details given). The method was evaluated in the analysis of C8 to C22 alkanes and subsequently applied in the analysis of coffee beans, spruce bark, black pepper, beer and PVC floor covering. Chromatographs are presented. The advantages and disadvantages of the trapping device are tabulated.
Organics, volatiles Food Food Spruce Bark Beer Commercial product GC

"Automatic Determination Of N-methylcarbamate Pesticides By Using A Liquid Liquid Extractor Derivatization Module Coupled Online To A Gas Chromatograph Equipped With A Flame Ionization Detector"
J. Chromatogr. A 1993 Volume 633, Issue 1-2 Pages 169-176
E. Ballesteros, M. Gallego and M. Valc&aacute;rcel

Abstract: A continuous extraction system for the continuous introduction of carbamate pesticide derivatives into a gas-liquid chromatograph was developed. The hydrolysis products of aryl N-methylcarbamates (phenols) were extracted with or without derivatization in a continuous fashion by using ethyl acetate or acetic anhydride in n-hexane, respectively. The acetylated phenolic portion of N-methylcarbamates is highly selective, which was taken advantage of to identify six pesticides (propoxur, carbofuran, carbaryl, aminocarb, benthiocarb and methiocarb). The chromatographic responses obtained were linear between 0.2 and 160 mg/l of the different N-methylcarbamates, and the relative standard deviation was 1.9-3.9%.
Carbamates, N-methyl Pesticides GC Sample preparation Flame ionization

"Electroinjection Analysis. Concept, Mathematical Model And Applications"
J. Chromatogr. A 1997 Volume 772, Issue 1-2 Pages 115-127
Victor P. Andreev*, Natalia B. Ilyina, Elena V. Lebedeva, Alexandr G. Kamenev and Nicolai S. Popov

Abstract: Mathematical models for the mutually complementary techniques of electroinjection analysis (EIA; a combination of FIA and CZE; Talanta, 1996, 43, 909) and electrophoretically mediated microanalysis (EMMA; Patterson et al., J. Chromatogr., A, 1996, 732, 119) are presented. EIA and EMMA are demonstrated by the determination of Cr(VI) and Co2+, respectively, in water (detection limits 1.4 and 1 ng/ml, respectively).
Cobalt(II) Chromium(VI) Water Electrophoresis

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

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

"Thin Layer Flow Cell With A Rotating Disk Electrode"
J. Electroanal. Chem. 1984 Volume 164, Issue 1 Pages 79-87
Joseph Wang and Bassam A. Freiha

Abstract: A channel-type electrochemical flow cell with a rotating disk electrode has been constructed and characterized. The work shows that the effect of rotation is to enhance the rate of mass transport. At rotation speeds higher than 900 rpm the response becomes independent of the flow rate and channel thickness. As a result, low flow rates can be used without sacrificing the sensitivity. Analytical advantages are demonstrated using liquid chromatography, stripping analysis, stopped rotation voltammetry and flow injection analysis.
Electrode Potentiometry Voltammetry

"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

"Novel Flow Injection Analysis Systems For Drug Analysis"
J. Pharm. Biomed. Anal. 1992 Volume 10, Issue 10-12 Pages 769-773
Gary D. Christian

Abstract: Principles of operation and advantages of a cam-driven sinusoidal-flow syringe pump are described for use in conventional FIA or sequential injection analysis (SIA). SIA is a modified flow method that allows most analyzes to be performed on a single line with only one syringe. The apparatus is relatively cheap, readily automated and easily adaptable to different chemical methods. Flow injection coulometric titration is described as a valuable technique for analysis of unstable reagents or standards. Acid-base, redox, precipitation and complexometric titrants can be generated electrochemically, as can unstable titrants such as Cu(I), Br, Cl and Cr(II). The techniques described have potential for automatic drug assays. A review with 32 references. Flow injection analysis (FIA) has become a versatile tool for rapid and automated analysis. As its capabilities have increased, so have the complexity and operation of the apparatus. Ways to simplify both the apparatus and the application of injection techniques are investigated. A novel cam-driven syringe pump and the development of sequential injection analysis (SIA) are discussed, and some applications presented. Flow injection coulometric titrations. are presented as a means to further alleviate reagent stability and calibration problems. These systems have potential for automatically carrying out many drug assays.
Drugs Pharmaceutical Coulometry

"Cefuroxime Selective Electrodes For Batch And FIA Determinations In Pharmaceutical Preparations"
J. Pharm. Biomed. Anal. 1998 Volume 18, Issue 1-2 Pages 93-103
J. L. F. C. Lima, M. C. B. S. M. Montenegro* and M. G. F. Sales

Abstract: Different cefuroxime selective electrodes, without internal reference solution and comprising PVC membranes, were constructed and evaluated. Membranes were prepared with cefuroxime tetraoctylammonium (A) or cefuroxime bis(triphenylphosphoranylidene)ammonium (B) as ion-exchanger, 2-nitrophenyl octyl ether (X) or bis(2-ethylhexyl)sebacate (Y) as plasticizing mediator solvent and 4-tert-octylphenol (TOP) as additive. From the comparative evaluation of the described electrodes, membranes comprising 2-nitrophenyl octyl ether, cefuroxime tetraoctylammonium and 4-tert-octylphenol presented better working characteristics. For these electrodes (type XA-TOP), with a lifetime >5 mo, a lower limit of linear range of 2.8 x 10^-4 M, a practical detection limit of 1.3 x 10^-4 M, a reproducibility of ~ ±0.6 mV day-1 and a slope of -50.4 mV decade-1, under H3PO4/NaH2PO4 solutions (pH 3.5; I = 0.1 M), were found. The presence of the additive on the membranes was of crucial importance for the electrodes good characteristics. Interference from sulfate, chloride, nitrate, iodide, cefaclor, cefadroxil, cefazolin and cephradine, on the electrodes behavior was evaluated. Only a slight interference from nitrate and iodide was recorded, being type XA-TOP electrodes the most selective units. Electrodes with a tubular configuration prepared with type XA-TOP membranes, aiming flow injection anal., were also constructed. When these tubular potentiometric detectors were evaluated in a double-channel flow injection manifold, with 3.5 pH and 0.1 M ionic strength conditions, significantly better working characteristics than those of the corresponding conventional electrodes, namely higher slopes (-54.6 mV decade-1) and better reproducibilities (±0.2 mV day-1), were found. Both conventional and tubular type XA-TOP electrodes were used for injections analyzes by batch and FIA, respectively, presenting low consumption of samples and reagents. Relative error deviations to the reference procedures <3.0% were found.
Cefuroxime Pharmaceutical Electrode Electrode Electrode Potentiometry

"Stacked Modules For Micro-flow Systems In Chemical Analysis: Concept And Studies Using An Enlarged Model"
Sens. Actuat. B 1993 Volume 17, Issue 1 Pages 19-25
J. C. Fettinger, A. Manz*, H. L&uuml;di and H. M. Widmer

Abstract: A valveless FIA system is described comprising a stacked series of 2 mm thick x 50 mm diameter polished Plexiglass elements. The elements have a 35 mm diameter ring of 11 or 12 evenly spaced 1 mm diameter holes with either a 1 cm, 10 cm or 20 cm central hole, a channel, a channel and central hole or no central hole, and are stacked to provide mixing T-pieces, mixing chambers etc. (diagrams given). The use of this modular system was demonstrated with the use of 2.5 mM C. I. Reactive Blue 2 (details given) for sample introduction and injection and was coupled to an optical detector. Samples retained 96-97% of their concentration and calibration graphs were linear with standard deviations of 1%.

"Urea Potentiometric Biosensor Based On All-solid-state Technology"
Sens. Actuat. B 1993 Volume 16, Issue 1-3 Pages 448-452
D. Martorell, E. Mart&iacute;nez-F&aacute;bregas, J. Bartrol&iacute; and S. Alegret, C. Tran-Minh

Abstract: All-solid-state electrodes (without an internal contact solution), were constructed using a procedure which permitted the implementation of transducers in various configurations (cf., Biosensors Bioelectron. 1989, 4, 287). The transducers consisted of ammonium-selective PVC membranes applied directly on to conductive composite materials, e.g. graphite/epoxy composites. Urease was immobilized on to the PVC membranes, using the procedure of Kurmaran et al. (cf., Anal. Chem., 1991, 63, 1914) which allowed the deposition of an extremely thin layer of reticulated enzyme (1-2 µm) by means of an aerosol-spraying procedure. The resulting urea potentiometric biosensors exhibited a short response time (10 s) and a wide linear range (0.01-1 mM urea) with a sensitivity of 55 mV/decade. The lifetime of the sensor was ~40 days in periodical calibration use. A flow-through biosensor was also constructed using the same type of transducer and the same enzyme immobilization procedure for use in a FIA system. Using the flow-through sensor for the determination of 0.1 mM urea resulted in an RSD (n = 20) of 0.4%.
Urea Urine Potentiometry Electrode Sensor Electrode Electrode

"Modular Setup For A Miniaturized Chemical Analysis System"
Sens. Actuat. B 1993 Volume 15, Issue 1-3 Pages 211-213
Bart H. van der Schoot*, Sylvain Jeanneret, Albert van den Berg and Nico F. de Rooij

Abstract: The miniature FIA system described incorporates two piezoelectrically operated silicon micro-pumps (cf. Van Lintel et al., Sens. Actuators, 1988, 15, 153) and an ISFET-based flow-through cell for measuring ion concentrations.
Field effect transistor

"Response Characteristics And Application Of Chalcogenide Glass Cr(VI) Selective Electrode"
Sens. Actuat. B 1997 Volume 45, Issue 3 Pages 239-243
Jan H. Christensen, Philip Clemmesen, Gregers H. Hansen, Karin Liltorp and John Mortensen*

Abstract: A chalcogenide glass Cr(VI) selective electrode has been tested. The Nernst plot is S-shaped, and the slope of the mid linear portion is about 90 mV decade-1. An analytically useful potential change from about 10^-6-10^-3 M Cr(VI) results. The response is related to a surface sensing mechanism, which is of redox nature. The electrode is generally sensitive towards compounds with high oxidising and reducing powers but insensitive towards ions with poor oxidising or reducing capacities. The response is slow and depends on the reduction potential of the analyt compounds, the exposure time and the concentration level. Therefore a flow-Injection-Analyser-system (FIA) is developed for the determination of Cr(VI) in aqueous environments. For the reduction of response times thereby enhancing the performance of the electrode reducing agents or electrochemical reduction between FIA injections were successfully employed. It is concluded, that to a large extend the FIA-system can be optimized to aqueous environments with Cr(VI) concentrations down to 10^-6 M. Special applications is under development for on-line measurements of Cr(VI) for production control in the electroplating industries.
Chromium(VI) Electrode

"Enzymeless Approach For The Determination Of Some Biologically Important Species"
Sens. Actuat. B 1998 Volume 50, Issue 2 Pages 156-163
Sheela Berchmans, H. Gomathi* and G. Prabhakara Rao

Abstract: In a recent communication of ours we reported electrocatalytic properties of a glassy carbon (GC) electrode modified by Nickel hydroxide/Oxyhydroxide to various sugars and alcohols. The analytical utility of this redox system towards the estimation of a few biologically and clinically important compounds such as glucose, ascorbate, lactate and H2O2 is reported and in the present study details of these determinations based on amperometric detection, levels of these compounds detected and the interferences are discussed in this communication.
Glucose Alcohols Electrode

"Electrochemiluminescence Of Luminol For 2,4-D Optical Immunosensing In A Flow Injection Analysis System"
Sens. Actuat. B 1998 Volume 51, Issue 1-3 Pages 100-106
Christophe A. Marquette and Lo&iuml;c J. Blum*

Abstract: Luminol-labeled antibodies have been prepared using glutaraldehyde as a crosslinking agent and used in a 2,4-dichlorophenoxyacetic acid (2,4-D) competitive electrochemiluminescent immunosensor. 2,4-D was covalently immobilized at a glassy C electrode surface, via a C6 spacer arm, by a novel procedure giving stable immobilized antigens that could be then stored dry, used, and regenerated 50 times without loss of binding capacity. The luminol electrochemiluminescence detection was performed in a flow injection analysis system. The optimum conditions were an oxidation potential of +500 mV vs. a Pt pseudo-ref. electrode, in the presence of 600 µM H2O2. In these conditions, luminol could be detected in the range 5.5 fmol - 55 nmol. Luminol-labeled anti-2,4-D antibodies or peroxidase-labeled secondary antibodies were tested for the 2,4-D immunodetection. With both the corresponding electrochemiluminescent and chemiluminescent immunoassays it was possible to detect 0.2 µg free 2,4-D/L. The overall time of experiment was 50 min and a linear range of 0.2 µg/L - 200 mg/L was obtained with the peroxidase format, whereas the range was 0.2-200 µg/L with the luminol format.
2,4-dichlorophenoxyacetic acid Luminol Chemiluminescence Sensor Electrode Electrode

"Design And Application Of A New Phase Separator For Flow Injection Liquid-liquid Extraction"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1769-1775
Soulin Lin*, Qin Shuai, Haiou Qiu and Zhiyong Tang

Abstract: A diagram of the proposed all-glass separator is presented, together with diagrams of manifolds incorporating the separator for use with flame AAS, ICP-AES and spectrophotometry. It shows improved long-term stabi, robustness and degree of phase separation by comparison existing separators, and per integral in situ collection of the extract at different phase flow-rate ratios.
Spectrophotometry Sample preparation

"Separation And Preconcentration By Flow Injection Coupled To Tungsten-coil Electrothermal Atomic Absorption Spectrometry"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1925-1934
M&aacute;rcia M. Silva, Francisco J. Krug*, Pedro V. Oliveira, Joaquim A. N&oacute;brega, Boaventura F. Reis and Daniel A. G. Penteado

Abstract: Owing to the uncertain pyrolysis performance of the W-coil atomizer, a flow injection preseparation-pre-concentration system was developed, diagrams of which are presented. A 16 µL SPE microcolumn (Chelex-100) was mounted on the tip of the arm of a Perkin-Elmer GTA-96 ETAAS autosampler, which delivered 20 µL portions of the eluate (eluent 2 M HCl) to the W coil [protected by Ar/H2 (9:1)]. For Pb (model analyte) retained from sample solution flowing at 3 ml/min for 1 min, the enrichment factor was 64, the detection liwas 75 ng/l and the RSD (n = 10) at 2 µg/l was
Lead Spectrophotometry

"Low-consumption Thermospray Nebulizer With A Fused-silica Vaporizer For Inductively Coupled Plasma Atomic-emission Spectrometry"
Spectrochim. Acta B 1986 Volume 41, Issue 11 Pages 1217-1220
J. W. Elgersma and F. J. M. J. Maessen, W. M. A. Niessen

Abstract: The nebulizer was modified from that of Meyer et al. (ICP Inf. Newsl., 1985, 10, 955) in order for it to operate effectively at a liquid-uptake rate of 0.1 mL min-1 (i.e., compatible with the eluate flow rate in micro-column HPLC and with good sensitivity in flow injection ICP-AES). Although the detection limits were much the same as with conventional pneumatic nebulization, it is considered that they can be improved by increasing the thermospray head temperature provided that the concomitant clogging of the nebulizer is suppressed by use of larger diameter vaporizer tubing.
HPLC Spectrophotometry

"Characterization Of A Nebulizer Interface For Flame Atomic Absorption Spectroscopy"
Spectrochim. Acta B 1987 Volume 42, Issue 7 Pages 883-888
Anders Gustavsson, Olle Nygren

Abstract: A nebulizer interface is described (with diagram) for the coupling of low-flow-rate techniques (e.g., flow injection analysis and HPLC) with flame AAS. It consists of a concentric nebulizer, a heated aerosol chamber, a PTFE adapter and an SP9 burner head. The interface was connected to Varian model 1475 and Pye Unicam SP1900 flame AAS instruments with water, CHCl3 and aqueous methanol as test solution and simulated normal flow injection analysis and HPLC conditions.
Spectrophotometry

"Characterization Of An Interface For Sample Introduction Into An Inductively Coupled Plasma"
Spectrochim. Acta B 1987 Volume 42, Issue 1-2 Pages 111-118
Anders Gustavsson

Abstract: The interface, which is suitable for connecting an ICP as a concentration.-sensitive detector in HPLC or flow injection analysis, consists of a glass Meinhard concentric nebulizer, a heated aerosol-desolvation chamber, and a jet separator to remove most of the solvent vapor and nebulization gas. Analyte transport efficiencies of ~35% can be attained, with much enhanced aerosol analyte concentration. at acceptable plasma solvent loads by comparison with conventional nebulization systems.
Spectrophotometry

"Analytical Characteristics Of A High Efficiency Ion Transmission Interface (S Mode) Inductively Coupled Plasma Mass Spectrometer For Trace Element Determinations In Geological And Environmental Materials"
Spectrochim. Acta B 1998 Volume 53, Issue 6-8 Pages 1087-1107
I. B. Brenner*, M. Liezers, J. Godfrey, S. Nelms and J. Cantle

Abstract: The analytical performance of a high transmission interface (S mode), inductively coupled plasma-quadrupole mass spectrometer (the VGE Plasma Quad 3) was evaluated for multitrace element analysis of geological and environmental materials. The sensitivity, limits of detection (LODs), effect of Ca and Na and other major elements on mass response, background, percentage 156CeO+/140Ce+, 70Ce++/140Ce+, and long- and short-term variations were compared with those obtained with the conventional mode (normal mode). Normal mode sensitivities varied from 20 MCPS ppm-1 (millions of counts per s per ppm) for 9Be+, 70-80 MCPS ppm-1 for 59Co+, 90 for 115In+ and 40-50 MCPS ppm-1 for the heavy masses. S mode sensitivities were 180 MCPS ppm-1 for 59Co+, 350-380 for 115In+ and 140Ce+, 300 MCPS ppm-1 for 208Pb+, and 150 MCPS ppm-1 for 232Th+ and 238U+, i.e. enhancements amounting to 7. Three s normal and S mode LODs are mainly in the 1-2 and 0.1 ppt range, respectively. S mode LODs are enhanced relative to the normal mode, for masses >80 amu, by factors ranging from ~10 to 50. S mode LODs are depressed relative to normal mode LODs for masses <50 amu by a factor of 10, and the extent of depression is related linearly to mass. In the high- and mid-mass ranges, backgrounds were ~10. They were not affected by sample composition: at 8 amu the S mode background for real samples amounted to ~20, whereas at 220 amu it amounted to four counts. S and normal mode percentage 156CeO+/140Ce++ and percentage Ce++/Ce+ ratios were ~1.5%, and temporal variations were insignificant. The percentage RSDs of normal and S mode Sr+, Ag+ and Pb+ isotope ratios were ~0.1%, with the exception of S mode 208Pb+ and 208Pb+/206Pb+ ratios in the presence of NaCl, which were degraded by a factor of ~2. Normal and S mode long-term variations for continuous aspiration of 0.1% NaCl for periods of up to 13 h were mass dependent, varying from 2.5-4% for 7Li+ and 9Be+ to ~2% for the mid-mass range, increasing slightly to ~3% for high masses. Most of this variation occurred during the 1st 100-150 min of the anal. during cone priming. With compensation, normal and S mode long-term percentage RSDs and drift were reduced to 1-2%. These variations indicate that extended periods of S mode anal. can be conducted without periodic recalibration. A calibration procedure, based on spiked HNO3, was validated by analyzing spiked NaCl solutions, standard water and geological standard reference material (SRM) solutions with internal standardization using conventional solution delivery and flow injection. The agreement of the S mode data and the certified and literature values for ultratrace elements, including ppt levels of rare earth elements in the water standards, was satisfactory. An important conclusion is that ion sampling effects in the S mode are minimal and that the enhanced ion transmission interface is not only beneficial for microanalysis using laser ablation, but for geological and environmental type solutions as well. Sensitivity enhancements were preserved and matrix effects were approximately ±20% for solutions containing 0.1-0.2% total dissolved salt concentration. These variations were reduced to <5% with internal standards matched in mass and ionization potential.
Metals, rare earth Environmental Geological Mass spectrometry

"One-Shot Flow Injection Analysis With Immobilized Enzyme Columns: Clinical Applications"
Anal. Sci. 1987 Volume 3, Issue 3 Pages 277-278
M. OHYABU, M. FUJIMURA, K. TANIMIZU, Y. OKUNO, M. TABATA, M. TOTANI and T. MURACH

Abstract: A flow injection system is described (with diagrams) for the determination of glucose, lactic acid, uric acid and urea-N in serum, plasma or urine. Detection is by chemiluminescence at 425 nm after reaction of enzymatically formed H2O2 with luminol.
Glucose Lactic acid Uric acid Nitrogen, urea Blood Plasma Blood Serum Urine Clinical analysis Chemiluminescence

"A Computer-controlled Variable-volume Injector For Flow Injection Analysis"
Anal. Sci. 1995 Volume 11, Issue 3 Pages 401-404
H.-L. Wu, Y. HAYASHIBE, Y. SAYAMA, M. SHIBUKAWA and K. OGUMA

Abstract: A computer-controlled time-based variable-volume injector for the introduction of samples into a flow injection analysis system has been developed. A sixteen-port multifunctional valve, automatically controlled by a computer, was used for sample injection and switching of the flow path. A variable injection time with a precision of 1/2000 s was provided by the computer. The flow system (shown schematically) employed a Hitachi U-100 spectrophotometer as a detector. The injector was shown to deliver 8 µL to a few millilitres of sample solutions with good reproducibility and high precision for 0.4 mM methyl orange solutions.
Methyl orange Spectrophotometry

"Analytical Applications Of Modified Lead Dioxide Electrodes"
Anal. Sci. 1997 Volume 13, Issue suppl Pages 273-278
JOON-WOO LEE, YOON SUN LEE, and IN-HYEONG YEO

Abstract: Electrochemical activity and stability of pure lead dioxide(PbO2) and lead dioxide incorporated with metal ions (As5+, B3+, Cr3+, Fe3+ and Ni2+) were studied. Heterogeneous rate constants for oxidation of numerous inorganic and organic compounds at PbO2 were compared with those at mixed lead dioxide electrodes. Among the tested metal ions, it turns out that arsenic is one of the promising elements. The electrochemical stability of he mixed oxide electrode prepared in an optimum condition, i.e., As5+/Pb2+ in the deposition solution, was increased compared to that of PbO2. For the application of the electrode material to electroanalysis, detection of thiourea, for example, at PbO2, and As incorporated lead dioxide electrodes(As/PbO2) as working electrodes in a thin layer electrochemical cell for flow injection analysis(FIA) was investigated by a constant-potential amperometry. Sensitive detection of thiourea with a detection limit of 1.4 x 10^-7 M was achieved with PbO2 and As/PbO2 electrodes.
Thiourea Amperometry Electrode Electrode

"Flow Analysis With Electrochemical Detection"
Anal. Proc. 1983 Volume 20, Issue 11 Pages 562-565
E. Pungor, K. T&oacute;th

Abstract: Procedures developed in the authors' laboratory are discussed briefly. The construction of a flow-through micro-conductivity and permittivity detector cell is described. (12 references)
Conductometry Permittivity

"Advances In Flow Injection Analysis With Coated Tubular Ion-selective Electrode Units"
Anal. Proc. 1987 Volume 24, Issue 11 Pages 331-333
J. F. van Staden

Abstract: A review is presented of coated tubular ion-selective electrodes for flow injection analysis, including a discussion of their construction, preparation, conditioning, implementation, response ranges and times, and applications. (24 references).
Electrode Electrode

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

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

"Quantification And Enantiomeric Purity Of Pharmaceuticals In Dosage Forms Using Flow Injection Analysis With Dual Absorbance And Polarimetric Detection"
Anal. Proc. 1992 Volume 29, Issue 6 Pages 255-257
Gaoyuan Liu, David M. Goodall and John S. Loran

Abstract: The use of a flow injection system with a polarimetric detector in series with an UV detector to determine the amount and enantiomeric purity of a drug in dosage form is described (diagram given). Samples were extracted with CHCl3 before analysis. Calibration graphs obtained were rectilinear. Studies have shown that a laser-based polarimetric detector designed for HPLC can add a new dimension to the field of flow injection (FI) anal. This paper presents the 1st application of a polarimetric detector in series with an UV detector to determine the amt. and the enantiomeric purity of a drug in dosage form using FI. The absorbance detector quantifies the abs. amt. of the analyte, while the ratio of optical rotation to absorbance allows the enantiomer mole fraction to be determined.
Pharmaceutical Polarimetry Spectrophotometry Sample preparation

"Poly(vinyl Chloride) Matrix Membrane Ion-selective Electrode For The Analysis Of Procaine Drug"
Anal. Proc. 1993 Volume 30, Issue 3 Pages 146-147
M. A. Hamada, G. J. Moody, J. D. R. Thomas

Abstract: Procaine (I) flavianate (10 mg; prepared by precipitation from an equimolar mixture of I hydrochloride and flavianic acid) was mixed with PVC powder (150 mg), dioctyl phthalate (370 mg) and THF (4 ml), and used to produce membranes (3 cm diameter) from which discs were cut to prepare ion-selective electrodes. The electrodes were used in conjunction with a double-junction Ag - AgCl (KNO3) reference electrode for potentiometric determination of I hydrochloride at 25°C. Electrode response was rectilinear from 10 µM to 0.1 M I and the detection limit was 5.1 µM-I. The electrode was only slightly selective for I over atropine, quinine and ephedrine but was considered suitable for analyzing pharmaceutical preparations; results obtained on commercial procaine penicillin preparations agreed well with those obtained by flow injection analysis or by the British Pharmacopoeial (1980) method.
Procaine flavianate Pharmaceutical Electrode Electrode Potentiometry

"Development Of A Silicon Photodiode, Electrogenerated Chemiluminescence, Flow-through Detector"
Anal. Proc. 1995 Volume 32, Issue 4 Pages 125-127
Andrew W. Knight, Gillian M. Greenway and E. David Chesmore

Abstract: A solid-state Si photodiode detector was developed and incorporated into a flow cell with electrodes for electrogenerated chemiluminescence (cross-sectional diagram given). The system was applied to the electrochemiluminescent reaction of tris (2,2'-bipyridyl)ruthenium(II) [Ru(bpy)32+] and tripropylamine. A single positive potential was applied to the working electrode to produce the Ru(bpy)33+; oxidation products of the amine then react with water to form highly reducing intermediates that can reduce the Ru(bpy)33+ complex back to Ru(bpy)32+ in an excited state which emits light. The optimum experimental conditions were: 1.2 mM Ru(bpy)32+ in 0.05 M phosphate buffer of pH 6.5 at a flow-rate of 2 ml/min and voltage pulses from 0-1.35 V (vs. Ag) over 5 s. Sample injection was performed by either pre-mixing samples of tripropylamine and Ru(bpy)32+ reagent followed by injection or by pumping both solutions directly and continuously into the detection cell; the latter method is preferred as the analysis time is shortened, there is no inline dispersion and signal intensity and reproducibility are improved. The calibration graph was linear over 3 decades with a detection limit of 140 ppb. RSD (n = 5) ranged from 0.5-2.4%.
Tripropylamine Chemiluminescence

"Peptide Analysis By Capillary Liquid Chromatography-continuous-flow Liquid Secondary Ion Mass Spectrometry"
Adv. Mass Spectrom. 1998 Volume 14, Issue 1 Pages 1-19
Celma, A.

Abstract: We shall describe a micro-HPLC-UV-Cf-LSIMS system that allows to work in several modes, i.e., flow injection analysis using a µinjector, capillary HPLC injecting µvolumes. and sample pre-concentration on the top of the column using a standard injector and gradient elution. All these arrangements were tested employing Lanreotide (D-β-Nal-Cys-Try-D-Trp-Lys-Val-Cys-Thr-NH2) as a model peptide.
Lanreotide Mass spectrometry LC

"Use Of Segmented Micro-continuous-flow Analysis And FIA In Water Analysis"
Am. Environ. Lab. 1989 Volume 1, Issue 2 Pages 60-63
Straka, M.R.

Abstract: The complementary nature of the methodologies of macrosegmented and microsegmented continuous-flow and nonsegmented FIA is discussed. The relative advantages and disadvantages are highlighted and general guidelines for selection of one technique over another are suggested.
Environmental Water

"HPLC Sample Injection And Column Switching Using A Multifunctional Valve"
Am. Lab. 1981 Volume 13, Issue 4 Pages 151-157
Harvey, M.C.;Stearns, S.D.

Abstract: Sample injection and column switching was easily done with a single low dead volume 10-port HPLC (high-pressure liquid chromatography) valve (Valco Instruments). This valve has had several years of extensive field use at high pressures in a multiloop HPLC autosampler and maintains 7000 psi after thousands of switching operations. The valve body is Nitronic 60 stainless steel and the rotor is Valcon 'H' fluorocarbon polymer blend. The valve is switched with a Valco air actuator and digital valve sequence programmer. Three HPLC columns (Custom I.C, Inc.) were used in this study. The single column backflushing experiment used a 4.6 mm i.d. x 20 cm x 5 m Customsphere silica column with hexane as solvent. Sample injection followed by backflushing is the simplest exchange of HPLC column switching. Backflushing a properly packed 5-m spherical HPLC column will clean the column and inlet frit without disturbing the packing. This leads to better HPLC peak shape and longer column life. The model compounds hexadecane [544-76-3] and hexylbenzene [1077-16-3] were separated. (SFS)
HPLC

"Continuous-flow Device For Oxygen Extraction From Natural Waters And Conversion To Carbon Dioxide For Isotopic Analysis"
An. Acad. Bras. Cienc. 1981 Volume 53, Issue 1 Pages 57-60
Braathen, C., Rebello, A.L.

Abstract: Unopened sample bottles containing natural waters are subjected to a 2.3-L/h flow of purified N2 which flushes the dissolved O2 out of the water samples, into 2 water retention traps, and then, through a 400°C oven for quantitative conversion to CO2 over activated C and a Ni catalyst. The CO2 flows with the N2 carrier out of the oven and is collected in a liquid N trap. This extraction-conversion is efficient (systematically extracting ~4.5% more dissolved O2 from seawater than the Winkler Method) and yields a CO2 product for which the O isotope determinations are reproducible (0.16% standard deviation) and accurate. (SFS)
Oxygen Sea Mass spectrometry Sample preparation

"Flow Injection With Diaphragm Pump And Amperometric Detector"
Anal. Commun. 1996 Volume 33, Issue 2 Pages 75-77
Teiji Kakizaki, Kazunori Imai and Kiyoshi Hasebe

Abstract: A FIA system is described which has a diaphragm micropump with a moving section (actuator) and a pump section diaphragm). The actuator consists of two layers of piezoelectric elements of ceramic cemented together with three foil electrodes on the outer and inner surfaces. This vibrator is moulded in to rubber (diagram and details given). The driving source for the actuator was 0-100 V a.c., 50 Hz. Amperometric measurements were made with a Pt-disc, Ag/AgCl and Pt coil was working, reference and counter electrodes, respectively. This system enabled reliable amperometric measurements to be made in a FIA system with a carrier delivery system that gave a fluent constant flow of solutions without the use of pulse pumping devices. The method could be applied to the monitoring of ascorbic acid in soft drinks.
Ascorbic acid Soft drink Amperometry Electrode

"A Tungsten Oxide Coated Wire Electrode Used As A PH Sensor In Flow Injection Potentiometry"
Anal. Commun. 1998 Volume 35, Issue 12 Pages 395-398
Lucy T. Dimitrakopoulos, Telis Dimitrakopoulos, Peter W. Alexander, Dusan Logic and D. Brynn Hibbert

Abstract: A W oxide wire electrode is described for use as a pH electrode in a portable battery-powered flow injection analyzer described previously. The W oxide electrode exhibits a linear response of 44.8 ± 0.5 mV change per pH unit over a wide range, pH 2-11 in the steady-state mode. In the flow injection mode, the W oxide wire electrode exhibited a slope of 42.4 ± 0.9 mV per pH unit. The W oxide electrode was employed to determine the pH of various alcohol beverages and environmental water samples.
pH Beverage Environmental Potentiometry Electrode

"FTIR Microscopy As Novel Detection System In Micro Flow Injection Analysis"
Anal. Methods Instrum. 1995 Volume 2, Issue 1 Pages 52-54
Kellner, Robert; Lendl, Bernhard

Abstract: A Bruker 113v FTIR spectrometer was coupled with a Bruker IR microscope equipped with a HgCdTe detector. A flow-through cell was developed for this system comprising three parts; the central part of which was constructed of PVC with an inner volume of 1.6 µL and an optical pathlength of 500 µm. The windows consisted of two Si plates (diameter 5.5 mm, thickness 0.75 mm). As the IR beam is focused by the FTIR microscope down to 80 µm it was possible to probe volumes of 10 nl. IBMK was determined in hexane in the ppm range as a model substance. Possible future applications of the system as a µtotal analysis system are discussed.
Methyl isobutyl ketone Organic compound Microscopy

"Automated Determination Of Vitamin C In Food Stuffs And Biological Materials"
Analusis 1989 Volume 17, Issue 9 Pages 519-525
Bourgeois, C.F.;Chartois, H.R.;Coustans, M.F.;George, P.R.

Abstract: The sample (e.g., organ tissue, blood plasma, foodstuff) is extracted with aqueous 5% metaphosphoric acid and the extract is placed in an automated apparatus. Ascorbic acid is oxidized by iodine to dehyroascorbic acid, which is coupled with 4,5-dimethyl-1,2-phenylenediamine to give a fluorescent quinoxaline derivative. This compound is extracted into isoamyl alcohol, back-extracted into a basic aqueous solution where it forms a hydrophilic salt, and the fluorescence is measured against that of a borate buffer. Compared with conventional fluorimetric methods the measurement is carried out in an almost pure solution, thus minimizing matrix interferences. The mean recovery was 98.7%, the coefficient of variation was 1.4% and the sensitivity was 20 ng mL-1.
Ascorbic acid Biological tissue Blood Plasma Food Fluorescence Sample preparation

"Controlled Dispersion Flow Analysis Devices With Constant Flow For Flame Atomic Absorption Spectrometry"
Analusis 1994 Volume 22, Issue 9 Pages 453-457
DETCHEVA A. ; HAVEZOV I.

Abstract: The characteristics were compared of two controlled-dispersion flow systems [cf., Sherwood etal,Analyst (London), 1985, 110, 493] for providing a stable non-segmented flow for introducing samples into the nebulizer of a flame AAS instrument. Sample consumption was reduced by up to a factor of three compared to a conventional FIA system and the sample volume was easily varied from 50-600 l by altering the pump timing. The two systems were applied to the determination of Cu, Fe, Ni and Sr in fluorite.
Fluorite Spectrophotometry

"Some Aspects Of Design, Performance And Applications Of Electrochemical Detectors In HPLC And Flow Injection Analysis"
Ann. Chim. 1986 Volume 76, Issue 9-10 Pages 315-332
Stulik, K.;Pacakova, V.

Abstract: The authors review their experience with voltammetric and polarographic detectors in respect of selection of the working-electrode material, design of the cell, selection of operating parameters, measuring techniques and applications. (34 references).
HPLC Polarography Voltammetry Electrode

"Fibre-optic Biosensor Based On Fluorimetric Detection Using Confined Macromolecular Nicotinamide-adenine Dinucleotide Derivatives"
Biosens. Bioelectron. 1990 Volume 5, Issue 2 Pages 125-135
T. Scheper, A. F. B&uuml;ckmann

Abstract: Details are given of a flow injection system together with a measuring cell fitted with an optical fiber-based fluorescence probe (Ingold Messtechnik, Switzerland). A low-pressure Hg lamp is used as source, radiation (360 nm) from which is focused on a quartz fiber bundle guiding the light into the measuring chamber. The emitted fluorescence (460 nm) is collected by a concentric fiber bundle and guided to a photomultiplier. Appropriate enzymes and polyoxyethylene glycol - NAD+ are enclosed in the measuring compartment between an ultrafiltration membrane and the optical fiber tip. The apparatus is used with alcohol dehydrogenase and lactate dehydrogenase to determine alcohols or pyruvate and with glutamate - pyruvate aminotransferase and lactate dehydrogenase to determine lactate.
Sensor Fluorescence

"Electrocatalytic Properties Of Polypyrrole In Amperometric Electrodes"
Biosens. Bioelectron. 1991 Volume 6, Issue 8 Pages 689-698
Wolfgang Schuhmann, Roland Lammert, Martin H&auml;mmerle and Hanns-Ludwig Schmidt

Abstract: The electrocatalytic oxidation of NADH, ascorbate, urate, xanthine and H-2O-2 at different polypyrrole electrodes has been investigated. The conducting polymer was grown on platinum, glassy carbon, or graphite electrodes and modified by means of enclosed redox-active anions or other redox-active compounds covalently bound to either the N- or the β-position of the pyrrole. Copolymers of pyrrole and N-substituted pyrrole derivatives of chloranil or 2,3-dichloro-1,4-naphthoquinone showed outstanding electrocatalytic properties of the oxidation of NADH. The application of these electrodes in amperometric steady-state measurements or flow injection systems in combination with dehydrogenase reactions has been possible.
Ascorbate Xanthine Urate Nicotinamide adenine dinucleotide oxidized Sensor Electrode Electrode Electrode Electrode Amperometry

"Selectivity Of Conducting Polymer Electrodes And Their Application In Flow Injection Analysis Of Amino-acids"
Biosens. Bioelectron. 1993 Volume 8, Issue 1 Pages 65-74
J. C. Cooper*, M. H&auml;mmerle, W. Schuhmann and H. -L. Schmidt

Abstract: The permeability of conducting polymer-modified electrodes to electroactive amino-acids, the effects of deposited layer thickness, and the use of polyaniline and polypyrrole, were studied. Polyaniline was more effective than polypyrrole in supressing amino-acid oxidation (when the polymer layer was >100 mC cm-2, however, it was also less permeable to L-amino-acids than polypyrrole. Such electrodes were applied to the determination of H2O2 enzymatically produced from L-amino-acids in an L-amino-acid oxidase reactor by flow injection analysis. The amperometric response from from 0.01 to 1 mM phenylalanine, tryptophan, tyrosine and cysteine was recorded. Modification of electrodes with polyaniline may be important in reducing electrode fouling at conducting polymer electrodes where L-amino-acid oxidase is immobilized to, or entrapped within, the polymer.
Amino Acids Electrode

"Stable Mediated Amperometric Biosensors Using A Graphite Electrode Embedded With Tetrathiafulvalene In Silicone Oil"
Biosens. Bioelectron. 1993 Volume 8, Issue 9-10 Pages 483-491
Shishan Zhao and John H. T. Luong*

Abstract: A new method has been developed to incorporate the mediator, tetrathiafulvalene (TTF), to the electrode/solution interface of an amperometric biosensor. TTF was dissolved in methylphenyl polysiloxane (silicone oil) and embedded in a graphite disc electrode. The mediator was able to diffuse to the electrode surface at an electrocatalytically significant speed. The storage of TTF in the inert polysiloxane provided a long-lasting and stable mediator supply. TTF-silicone oil electrodes with immobilized glucose oxidase, xanthine oxidase, or amino acid oxidase exhibited sensitive, fast and reproducible responses. The glucose oxidase electrode was very stable for at least 2 months when stored at 4°C. Together with flow injection analysis (FIA), the enzyme electrodes were reused for at least 500 repeated analyzes during a 25 h operation without losing their initial activity.
Amperometry Sensor Electrode Electrode

"Electrochemiluminescence Flow Injection Immunoassay For Atrazine"
Biosens. Bioelectron. 1997 Volume 12, Issue 4 Pages 277-286
Robert Wilson*, Michael H. Barker, David J. Schiffrin and Ram Abuknesha

Abstract: Antibodies to atrazine were labelled with glucose oxidase and used in colorimetric enzyme linked immunosorbent assays. Transparent aminosilanized indium tin oxide coated glass electrodes were derivatized with aminodextran covalently modified with atrazine caproic acid. The labelled antibodies were used to investigate the derivatized electrodes colorimetrically and the electrodes were use in an electrochemiluminescence flow injection analyzer.. Electrochemiluminescence immunoassay for atrazine in the range 0-10 ppb showed that it was possible to detect less than 0.1 ppb, the precautionary limit for pesticides in drinking water recommended by the European Commission.
Atrazine Pesticides Water Chemiluminescence Immunoassay Electrode Electrode

"Amperometric Biosensor With A Composite Membrane Of Sol-gel Derived Enzyme Film And Electrochemically Generated Poly(1,2-diaminobenzene) Film"
Biosens. Bioelectron. 1998 Volume 13, Issue 1 Pages 67-73
Toshio Yao*,* and Kazuyoshi Takashima

Abstract: A sol-gel silicate-based biosensor for glucose was made by utilizing a composite membrane of sol-gel enzyme film and electrochemically generated poly(1,2-diaminobenzene) film to improve the selectivity of the sol-gel enzyme sensors. The stability of the sensor was improved by exposing the enzyme layer to glutaraldehyde vapor. The glucose sensor responded rapidly (ca. 15 s) to glucose at 0.6 V (versus Ag/AgCl), without any interferences from electroactive species such as L-ascorbate and urate below 0.2 mM. Reliable results were obtained in the assays of glucose in controlled human sera, with both the steady-state and flow injection measurements. Subsequently, the same sol-gel procedure was applied to the preparation of the sensors for galactose and cholesterol. The galactose and cholesterol sensors responded rapidly to galactose and cholesterol, respectively, although the sensitivity of these sensors was inferior to that of glucose sensor.
Glucose Galactose Cholesterol Serum Human Amperometry Sensor Electrode Electrode

"Estimation Of Soluble L-lactate In Dairy Products Using Screen-printed Sensors In A Flow Injection Analyzer"
Biosens. Bioelectron. 1998 Volume 13, Issue 2 Pages 219-225
W. A. Collier*, P. Lovejoy and A. L. Hart

Abstract: Screen-printed lactate sensors, with an outer membrane applied by an air-brush, were mounted in a flow injection analyzer. Dild. extracts of buttermilk and yoghurt were passed over the sensors. The lactate concentration. in the extracts was determined with a high degree of accuracy and precision (based on variation among sensors). Fresh sensors were used for each new buttermilk or yoghurt sample, but individual sensors were capable of giving repeatable results, with standard lactate solutions, over a large number of injections.
l-Lactate Food Food Electrode Electrode

"Characterization Of Immobilization Methods For African Swine Fever Virus Protein And Antibodies With A Piezoelectric Immunosensor"
Biosens. Bioelectron. 1998 Volume 13, Issue 12 Pages 1279-1286
Erich Uttenthaler*, Conrad K&ouml;&szlig;linger and Stephan Drost

Abstract: A direct piezoelec. flow injection analysis immunoassay for the detection of African Swine Fever virus and antibodies is presented. The peptide-specific monoclonal antibody 18BG3 and the virus protein 73 were used for detection with a quartz crystal microbalance. Accumulation of the analyte on the surface of this mass-sensitive biosensor resulted in a shift of the resonant frequency. Highly selective receptor layers were applied on the sensing electrode of the quartz crystal for detection of the complementary analyte. Different immobilization methods proved to be appropriate for coating of the monoclonal antibody 18BG3. A quartz crystal covalently coated with the antibody 18BG3 detected virus protein VP73 samples more than 20 times and was stable for more than 30 days. The coating of virus protein was performed by physisorption. A sensor with a virus protein receptor layer detected antibody 18BG3 samples 10 times within one day. The sensor device was able to perform one measurement cycle including blocking and regeneration within 30 min. With the help of a suitable carrier liq., measurements with serum samples were performed. The calibration curves for measurements in buffer and in serum could be determined and the detection limits for virus protein detection were 0.31 and 1 µg/mL, and for antibody detection 0.1 and 0.2 µg/mL, respectively.
African swine fever virus Protein Antibodies Blood Serum Sensor Immunoassay Microbalance

"Modular Concept Of A Laboratory On A Chip For Chemical And Biochemical Analysis"
Biosens. Bioelectron. 1998 Volume 13, Issue 3-4 Pages 427-438
Gert Blankenstein and Ulrik Darling Larsen

Abstract: A novel concept of a modular microchemical analysis system fabricated on silicon wafers using semiconductor technol. is presented. The strategy was to design and to develop single fluidic components with specific functions for sample handling, manipulation and measurement. All devices presented are based on monolithic structures manufactured with the same simple microfabrication techniques. The devices are designed to handle particle containing solutions allowing novel applications in biochemical and cytochemical analysis. Components have been developed for chemical anal. such as flow switches for valve-less sample injection and flow guiding, immobilization reactors, dialysis chambers, and filters, and for cell analysis and flow cytometry such as cell sorters and coulter counters. These single fluidic components are freely combinable, which enables the design of analyzers designed for a specific application. Additional, all fluid components can be equipped with integrated gold electrodes allowing conductivity measurements inside the microchannels. This opens up new application in chemical and biochemical analysis. A few examples in cell diagnostics such as flow cytometry on a chip and in micro-flow injection analysis are shown.
Conductometry Electrode

"Electropolymerization Of Pyrrole And Immobilization Of Glucose Oxidase In A Flow System: Influence Of The Operating Conditions On Analytical Performance"
Biosens. Bioelectron. 1998 Volume 13, Issue 3-4 Pages 371-682
Juan-C. Vidal*, Esperanza Garcia and Juan-R. Castillo

Abstract: The in situ potentiostatic electropolymerization of pyrrole (Py) on a Pt electrode in a thin-layer amperometric cell and the entrapment of the enzyme glucose oxidase (GOx) for the determination of glucose are reported. Polypyrrole (PPy) is directly formed by continuous passage of a buffered solution of the monomer (0.4 M) and enzyme (250 U mL-1) at pH 7 at a flow rate of 0.05-0.1 mL min-1 under a constant applied potential of +0.85 V vs Ag/AgCl decreases. The electrosynthesis of PPy by injection of 500 µL of a Py + GOx solution in a carrier electrolyte consisting of 0.05 M phosphate buffer and 0.1 M KCl at pH 7.0 was also assayed. The influence of the electropolymerization conditions on the analytical response of the sensor to glucose was investigated. The analytical performance of the PPy/GOx sensor was also studied in terms of durability and storage life, as well as selectivity against electroactive species such as ascorbic acid and uric acid as a function of the thickness of the polymer film formed.
Glucose Electrode Electrode

"High-throughput Flow Injection Analysis Of Glucose And Glutamate In Food And Biological Samples By Using Enzyme/polyion Complex-bilayer Membrane-based Electrodes As The Detectors"
Biosens. Bioelectron. 1998 Volume 13, Issue 7-8 Pages 809-815
Fumio Mizutani*, Yukari Sato, Yoshiki Hirata and Soichi Yabuki

Abstract: The concentration of glucose was determined by a combination of flow injection analysis (FIA) with amperometric enzyme sensor detection. The enzyme sensor was prepared by immobilizing glucose oxidase on an electrode coated with a polyion complex layer consisting of poly-L-lysine and poly(4-styrenesulfonate). The inner, polyion complex layer was useful for preventing electrochemical interferents (e.g., L-ascorbic acid, uric acid and acetaminophen) from reaching the electrode surface, which was effective for reducing the interferential responses upon the injections of biological and food samples. The sensor-based system could be used for the determination of glucose from 10 µM to 3 mM with the sampling rate of 180 h-1, and was stable for more than 2 mo. An FIA system for determining L-glutamic acid (3 µM-0.5 mM) was also prepared by using an enzyme electrode based on a glutamate oxidase/polyion complex-bilayer as the detector.
Glucose l-Glutamic acid Food Biological Amperometry Electrode Electrode

"Biosensors Based On Conducting Filled Polymer All-solid-state PVC Matrix Membrane Electrodes"
Biosensors 1989 Volume 4, Issue 5 Pages 287-297
Salvador Alegret and Esteve Mart&iacute;nez-F&agrave;bregas

Abstract: To construct solid-state sensors for NH4+, a layer (~7 mm) of epoxy-resin, rendered conductive by mixing it with twice its wt. of graphite powder, was applied to one end of an epoxy or PVC tube, and a shielded lead was fixed to this layer while it was soft. The resin was dried at 40°C for 24 h, then a flat cavity 0.3 mm deep was drilled in it from outside and layers of sensing material [nonactin - tris-(2-ethylhexyl) phosphate - PVC (1:15:4) in THF] were applied to the cavity and allowed to dry to form a convex membrane. The air-dried membrane was conditioned in aqueous 0.1 M NH4+. The sensors could be used in a conventional configuration or a flow-through sandwich arrangement (illustrated). Potentiometric urea sensors were produced by covering an NH4+ sensor with urease or Proteus vulgaris immobilized on nylon net or a polycarbonate filter, respectively. The sensors were evaluated under batch and flow injection conditions. For each, details of potential response, linear response range, response time, lifetime and electrode buffer solution are tabulated. Interference by K+ could be avoided by interposing a gas-permeable hydrophobic membrane between the biocatalytic and the NH4+-selective membranes. Advantages of the solid-state construction are stressed.
Ammonium Urea Polymer Sensor Electrode Electrode Electrode Electrode Potentiometry

"A Fluorescence-based Fiber Optic Biosensor For The Flow Injection Analysis Of Penicillin"
Biotechnol. Bioeng. 1992 Volume 39, Issue 11 Pages 1147-1150
Xiangfang Xie *, Ahmad A. Suleiman, George G. Guilbault

Abstract: A penicillin fiber optic sensor is described. The sensor is based on a co-immobilization of a pH indicator, fluorescein isothiocyanate (FITC), and penicillinase on a preactivated biodyne B membrane attached to the end of a bifurcated optical fiber. The characteristics of the sensor are investigated in conjunction with a flow injection analysis system. The proposed sensor is reversible and responds to penicillin in the concentration. range of 1 x 10^-4 to 5 x 10^-2 mol/L. The application of this sensor to penicillin anal. in some pharmaceutical samples is demonstrated.
Penicillin Pharmaceutical Fluorescence Sensor Sensor

"Laccase Electrode For The Continuous-flow Determination Of Phenolic Compounds"
Biotechnol. Techniq. 1994 Volume 8, Issue 7 Pages 503-508
Nabil Zouari, Jean-Loius Romette and Daniel Thomas

Abstract: Laccase from Botrytis cinerea (100 µL; 1-1.25 iu) was mixed with 900 µL of 5% 250 bloom gelatin in 0.02 M phosphate buffer of pH 6.8 at 40°C and applied to the polypropylene hydrophobic selective gas film (6 µm) of an amperometric O2 sensor. After drying at 25°C, copolymerization was achieved by treating with 1.25% glutaraldehyde for 5 min and the enzyme layer was covered with a Nucleopore polycarbonate membrane (0.03 µm). The resulting electrode was used in a continuous-flow system to determine phenolic substrates. The calibration graphs for 0-1.3 mM hydroquinone are shown. The RSD were 5%. Substrate specificity was studied using 10 mM substrate in 0.1 M phosphate/citrate buffer of pH 4. Results are tabulated; phenol and nitro- and chlorophenols were not oxidized by the laccase. The analysis time was ~1.5 min and the electrode response was stable for 800 assays using 0.25 mM hydroquinone.
Hydroquinone Amperometry Electrode

"Development Of A Sucrose Enzymic Biosensor"
Biotechnol. Techniq. 1998 Volume 12, Issue 4 Pages 305-307
A.M. Salgado, R.O.M. Folly, B. Valdman and F. Valero

Abstract: An enzymatic biosensor for sucrose determination was developed for online and continuous monitoring of sucrose concentration. The sensor was adapted to two different measurement schemes, one continuous and another injection sampling lines. The sensor adapted with the injection sampling line presented a linear measurement range of 5-20 g sucrose/1, good reproducibility, and a high versatility permitting the substitution of the immobilized enzymes when their activity decreased.
Sucrose Sensor Electrode

"Micro-enzyme Electrode As A High Performance Detector Of Flow Injection Analysis"
Bull. Chem. Soc. Jpn. 1989 Volume 62, Issue 6 Pages 1869-1874
Yoshihito Ikariyama,Shigeru Yamauchi,Tomoaki Yukiashi,Hiroo Ushioda and Masuo Aizawa

Abstract: The advantages of miniaturized enzyme electrode have been applied to flow injection analysis for the development of a rapid and selective method for the continuous determination of glucose. By assembling a micro-enzyme electrode having a diameter of 10 µm for an amperometric flow-through detector, at least 600 glucose samples can be determined in one hour. And micro-enzyme electrodes are satisfactorily stable for over 4 weeks even after 1000 glucose injections.
Glucose Electrode Electrode

"Apparatus For Measuring Chemical Oxygen Demand Based On Flow Injection Analysis"
Bunseki Kagaku 1980 Volume 29, Issue 3 Pages 222-223
KORENAGA Takashi

Abstract: A simple apparatus was developed for the rapid and continuous determination of chemical oxygen demand (COD) in environmental water samples based on the principle of flow injection-spectrophotometric analysis. A solution of 2.7 x 10^-4 M potassium permanganate in 3.3% sulfuric acid was pumped with a reciprocating pump into the manifold to which 20µl of sample (i.e. sodium oxalate solution) was also introduced by manual injection. After reaction, the mixture went through a quartz flow cell (10 mm light path, 18 µL volume) placed in a spectrophotometer operated at a wavelength of 525 nm. The manifold was made entirely of polytetrafluoroethylene tubing (0.5 mm inner diameter, 10 m length). The signal from the spectrophotometer was continuously recorded. When a pumping rate was chosen to be 1.9 mL min^-1 a residence time was 1 min. A sampling rate of 120 samples per hour was achieved and the apparent COD at a concentration range of 21-170 mg COD L^-1 was measured reproducibly. Chloride at 10 mg L-l level was suppressed by adding 0.1% silver nitrate in the flow injection system.
Chemical oxygen demand Environmental Water Spectrophotometry

"Analytical Chemistry And Microcomputers. 3. Uses: Flow Injection Analysis"