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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Instrumentation Science and Technology

  • Publisher: Taylor and Francis
  • FAD Code: ISST
  • CODEN: ISCTEF
  • ISSN: 1073-9149
  • Abbreviation: Instrum. Sci. Technol.
  • DOI Prefix: 10.1080/10739149
  • Other Name(s): Analytical Instrumentation
  • Language: English
  • Comments: Fulltext from 1968 V1. Continues Analytical Instrumentation ISSN 0743-5797 from 1994

Citations 36

"Flow Injection Chemiluminescence Analysis Of Diphenhydramine Hydrochloride And Chlorpheniramine Maleate"
Instrum. Sci. Technol. 2006 Volume 34, Issue 5 Pages 529-536
Chunling Yu; Yuhai Tang; Xiaonian Han; Shijie Wu

Abstract: A new chemiluminescence (CL) method, using flow injection, is described for the determination of diphenhydramine hydrochloride and chlorpheniramine maleate. The method is based on the restraining effects on the CL reaction of luminol-potassium ferricyanide in alkaline solutions. The various experimental parameters affecting the chemiluminescence intensity were studied carefully and incorporated into the procedure. The method allows the determination of 1.0-100 g mL -1 diphenhydramine hydrochloride and 0.1-10.0 g mL -1 chlorpheniramine maleate. The detection limits of the method are 0.3 g mL -1 for diphenhydramine hydrochloride and 0.02 g mL -1 for chlorpheniramine maleate. The method was successfully applied to the determination of diphenhydramine hydrochloride and chlorpheniramine maleate in pharmaceutical preparations.

"Inductively Coupled Plasma Optical Emission Spectrometric Determination Of Gadolinium In Urine Using Flow Injection On-line Sorption Preconcentration In A Knotted Reactor"
Instrum. Sci. Technol. 2006 Volume 34, Issue 3 Pages 305-316
J. A. Salonia; J. A. Gásquez; L. D. Martinez; S. Cerutti; M. Kaplan; R. A. Olsina

Abstract: An on-line gadolinium pre-concentration and determination system, implemented with ultrasonic nebulization coupled to inductively coupled plasma optical emission spectrometry (ICP-OES), associated with flow injection (FI) was studied. Gadolinium was retained as Gd-2-(5-bromo-2-pyridilazo)-5- diethylaminophenol complex (Gd-5-Br-PADAP) at pH 9.0, on the inner walls of the knotted reactor (KR). The collected analyte complexes were quantitatively eluted from the 200 cm KR with 30% (v/v) nitric acid. An enhancement factor of 255-fold was obtained (17 for KR and 15 for USN). The detection limit (DL) value for the pre-concentration of 15 mL of sample was 4.0 ng L -1 . The relative standard deviation (RSD) was 3.5%, calculated from the peak heights obtained. The calibration graph using the pre-concentration system for gadolinium was linear, with a correlation coefficient of 0.9996 at levels near the detection limit up to at least 200 g L -1 . The method was successfully applied to the determination of gadolinium in urine samples.

"On-Line Preconcentration Of Cadmium In Commercial Tea Samples Using Polyurethane Foam As Filter Associated With Ultrasonic Nebulization-Inductively Coupled Plasma Optical Emission Spectrometric Detection"
Instrum. Sci. Technol. 2005 Volume 33, Issue 4 Pages 449-459
P. F. Marchisio, A. Sales, S. Cerutti, E. Marchevsky, L. D. Martinez

Abstract: Tea is the most popular beverage, next to water, consumed by over two-thirds of the world's population. The present paper proposes an on-line pre-concentration procedure for cadmium determination in tea samples (Camellia sinensis) by ultrasonic nebulization associated with inductively coupled plasma optical emission spectrometry (USN-ICP-OES). It is based on the precipitation of cadmium(II) ion onto a conical minicolumn packed with polyurethane foam using 2-(5-bromo-2-pyridilazo)-5-diethylaminophenol (5-Br-PADAP) as precipitating reagent. The collected analyte precipitate was quantitatively eluted from the minicolumn with 20% (v/v) nitric acid. An enhancement factor of 240-fold (20 for pre-concentration and 12 for USN) was obtained. The detection limit (DL) value for the pre-concentration of 10.0 mL of sample was 4.0 ng L-1. The precision for 10 replicate determinations at 0.1 µg L-1 cadmium levels was 3.2% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the pre-concentration system for cadmium was linear with a correlation coefficient of 0.9998, at levels near the detection limits up to at least 500 µg L-1. The pre-concentration procedure was successfully applied to the determination of cadmium in tea samples.

"On‐Line Spectrophotometric System Based On Pseudo Liquid Drop And Handheld CCD Spectrometer For Monitoring Formaldehyde Level In Wastewater"
Instrum. Sci. Technol. 2005 Volume 33, Issue 3 Pages 297-307
Zaide Zhou, Guanping Zhong, Qing Tan, Yuan Li, Xiandeng Hou

Abstract: An on-line spectrophotometric system, based on a handheld CCD (charge coupled device) spectrometer and a liquid drop, was constructed for the purpose of monitoring of formaldehyde in wastewater. The liquid drop device was used as a reactor and optical cell for the spectrophotometric measurements to solve the problem of colored species stained onto a traditional quartz optical cell. To overcome the drawback of short optical path of a traditional liquid drop, a simple flow-through type optical cell with open ends was designed and used as a prolonged "liquid drop," i.e., a "pseudo" liquid drop. By using such a pseudo liquid drop, the advantages of a windowless optical cell of a liquid drop are retained, while the optical path is increased to over 7 times of that of a traditional liquid drop. The limits of detection for formaldehyde were found to be 0.05 µg/mL with the liquid drop, and 0.01 µg/mL with the pseudo liquid drop. The method was applied to the determination of formaldehyde in wastewater with satisfactory analytical results.
Formaldehyde Waste Spectrophotometry Flowcell Capillary

"On-Line Preconcentration System By Coprecipitation With Lanthanum Hydroxide Using Packed-Bed Filter For The Determination Of Tellurium In Water By ICP-OES With USN"
Instrum. Sci. Technol. 2004 Volume 32, Issue 4 Pages 423-431
M. Kaplan, S. Cerutti, S. Moyano, R. A. Olsina, L. D. Martinez, J. A. Gásquez

Abstract: A sensitive procedure for the determination of total tellurium traces in water samples is described, which combines an on-line analyte pre-concentration system coupled to inductively coupled plasma optical emission spectrometry (ICP-OES) associated with flow injection (FI) and ultrasonic nebulization (USN). Tellurium was pre-concentrated by co-precipitation at pH 9.1 with lanthanum hydroxide precipitate. The precipitate was quantitatively collected on a packed-bed filter with Amberlite XAD-4 resin and subsequently eluted with 5% (v/v) nitric acid. A total enhancement factor of 140-fold was obtained with respect to ICP-OES using pneumatic nebulization. The detection limit (3s) for the pre-concentration of 10 mL of aqueous solution (3s) was 0.15 µg L-1. The precision for 10 replicate determination at the 10 µg L-1 tellurium level was 2.6%, relative standard deviation (RSD), calculated with the peak heights obtained. The calibration graph using the pre-concentration system for tellurium was linear with a correlation coefficient of 0.9995 at levels near the detection limit up to at least 100 µg L-1. Satisfactory results were obtained for the analysis of tellurium in the standard reference material NIST 1643d 'Trace Elements in Water' and tap water.
Tellurium NIST 1643 Water Spectrophotometry Coprecipitation Amberlite Preconcentration Reference material

"On-Line Preconcentration System For Cobalt Determination In Bee Honey Using Flow Injection-Flame AAS"
Instrum. Sci. Technol. 2004 Volume 32, Issue 4 Pages 401-412
S. Cerutti, R. Fernandez Orsi, M. Kaplan, J. A. Gásquez, R. A. Olsina, L. D. Martinez

Abstract: A methodology for the on-line pre-concentration and determination of cobalt by flame atomic absorption spectrometry (FAAS) coupled with flow injection (FI) in bee honey samples is proposed. For the retention of cobalt, 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) complexing reagent, and Amberlite XAD-7 resin were used, at pH 9.5. The Co-(5-Br-PADAP) complexes were completely removed from the column with ethanol. An enrichment factor (EF) of 50 fold for a sample volume of 50 mL was obtained. The detection limit (DL) for the pre-concentration of 50 mL of aqueous solution was 0.18 µg L-1. The precision for 10 replicate determinations at the 10 µg L-1 cobalt levels was 3.6% relative standard deviation (RSD), calculated with peak heights obtained. The calibration graph using the pre-concentration system for cobalt was linear with a correlation coefficient of 0.9997 at levels near the DL, up to at least 300 µg L-1. The method was successfully applied to determination of total cobalt in honey samples.

"Miniaturized Capillary Electrophoresis System With Contactless Conductivity Detection And Flow Injection Sample Introduction"
Instrum. Sci. Technol. 2004 Volume 32, Issue 3 Pages 303-309
Lixin Wang and Chonggang Fu

Abstract: A miniaturized capillary electrophoresis (CE) system with contactless conductivity detection (CCD) and flow injection (FI) sample introduction was developed. It represents an ideal combination of high-resolution separation of CE with high throughput reproducible sample injection of FI, and universal and robust detection of CCD for the analysis of ionic species. Its design and fabrication method is described in detail. Performance tests of the system were performed for the analysis of surface water. It was found that complete separation of the cations studied (NH4+, K+, Ca2+, Na+, and Mg2+) could be obtained within 60 sec with peak height RSD better than 2.0%, thus achieving a sampling frequency of 60 hr-1. Detection limits were in the order of low µmolarity.
Ammonium Potassium Calcium Sodium Magnesium Surface Electrophoresis Conductometry Injection technique

"Solvent Extraction With Electrokinetic Multicommutation Analysis System"
Instrum. Sci. Technol. 2003 Volume 31, Issue 3 Pages 269-282
Long-Quan Li, Li Fang, You-zhao He

Abstract: The feasibility of solvent extraction with an electrokinetic flow analysis (EKFA) system should be investigated further because of its non-aqueous condition. As an example, the pre-concentration and determination of copper, including on-line color reaction, solvent extraction, and spectrometric determination were carried out by an electrokinetic multicommutation analysis system in this work. The proposed system consisted of one electroosmotic pump, four solenoid valves which were controlled by a personal computer, and a spectrometric detector. With the electroosmotic pump, sample and reagent solutions were aspirated into the system's color reaction section in small plugs, alternately, and were reacted sufficiently. Then, a plug of chloroform was inserted into the colored zone. The proposed system carried out solvent extraction by moving the sandwiched zone back and forth along its short extraction coil. After phase separation with a T-shape separator, organic phase was determined in a flow detection cell of the spectrophotometer. The electroosmotic pump is a liquid delivery device with the merits of non-pulsed and stable flow rate, simple pump structure, high driving efficiency, and facile flow control. Ethanol solution, a relatively high permittivity and innocuous solvent, was adopted as the pump carrier. In this paper, carrier additives were investigated further in order to improve the pump stability and efficiency (3.9 mL min-1 mA-1). The detection limit for copper was 0.03 mg L-1 (K=3, n=11) and its recoveries were in the range of 92-96% with a relative standard deviation of 5.2% (n=3). The proposed method can provide a throughput of 20 samples per hour.
Copper Spectrophotometry Solvent extraction Multicommutation Phase separator Instrumentation

"Simple Laboratory Made Automated Sequential Injection Analysis (SIA) Device. II. SIA Operational Software Based On LabVIEW (R) Programming Language"
Instrum. Sci. Technol. 2002 Volume 30, Issue 3 Pages 353-360
Hana Sklenarova, Antonin Svoboda, Petr Solich, Miroslav Polasek, Rolf Karlicek

Abstract: esented deals with the development of an automated computer-aided sequential injection analysis (SIA) system and its application to laboratory automation. In Part I, hardware and technical parameters of the SIA system were described. Part II introduces original lab-developed operational software (FaFSIA), enabling one to control the cited SIA system and to process experimental data, including their presentation. The software, based on graphic programming language LabVIEW is described in detail.

"Evaluation And Optimization Of A Laboratory-constructed Flow Chamber For On-line Immunomagnetic Separation"
Instrum. Sci. Technol. 2002 Volume 30, Issue 3 Pages 295-309
Z. Tang; H. Thomas Karnes

Abstract: Immunomagnetic separation (IMS) uses magnetic beads to facilitate separation of antibody-bound labeled antigens from free antigens in solution. Off-line immunomagnetic separation is time consuming due to the requirement of washing the magnetizable beads between assays and the multiple steps involved in the separation process. On-line IMS, in the flow injection mode, can overcome the disadvantages of off-line IMS, such as multiple washing steps. The purpose of this work is to develop, optimize, and validate an on-line magnetic separation flow chamber in the flow injection mode, suitable for post-column immunoreaction detection. The ends of the flow chamber were connected to the flow injection system. The on-line magnetic flow chamber was constructed using 1.0 I.D. x 1.58 O.D.mm Teflon tubing that was attached to an electromagnet. The electromagnet was constructed by wrapping a 305 x 25 x 40 mm block of hard steel with fine copper wire which was supplied with direct current (dc). The magnetic field was applied and released by switching the power on and off. The electromagnet was designed to have three terminals with 750 turns (yellow), 1000 turns (blue) and 1250 turns (red), respectively, to generate three different electromagnetic fields. A cooling tube was wound among the copper wire and ice water was used to cool down the core of the electromagnet. Water was pumped into the cooling tube using a VWR peristaltic pump and circulated in a forty-gallon container full of ice water. Various orientations and volumes of the flow chamber, various flow rates, and currents were investigated to obtain the maximum magnetic trapping efficiency. Digoxin was selected as a model analyte and a competitive format was used for immunoassay. Digoxigenin was labeled with R-phycoerythrin (PE-D) as a competing labeled antigen and anti-digoxin antibodies covalently linked biotin through streptavidin coated magnetic beads were used for magnetic separation. The immunoassay mixture was injected into the flow chamber after immunoreaction and immunomagnetic complexes were captured on the wall of the flow chamber using the electromagnet. The maximum trapping efficiency obtained was 98% using a five-fold straight flow chamber at a flow rate of 0.5 mL/min and a current of 1.5 amperes (A). The on-line magnetic separation immunoassay of digoxin in spiked phosphate buffer demonstrated a dynamic range of 0.5-15 ng/mL. A quadratic fit was found to provide the best fit to the data (r = 0.9937). The precision for two controls, 4.0 and 12 ng/mL, were 14.05% RSD and 10.75% RSD (n = 6) and the accuracy was 5.8% and 3.31% (n = 6), respectively. The limit of detection was calculated to be 0.44 ng/mL.

"Flow System From Analytical Calibration By The Integrated Method"
Instrum. Sci. Technol. 2002 Volume 30, Issue 3 Pages 251-266
Pawe&#; Koscielniak, Joanna Kozak, Ma&#;gorzata Herman

Abstract: The flow system has been designed for the purpose of performing analytical determinations according to the integrated calibration method. The system is equipped with a fully rotary valve which serves in preparation of the set of standard solutions from a single stock solution. A standard is exposed to measurements in two forms: by itself, and as a mixture with a sample. Each of the two solutions is able to be propelled to the detector at two different flow rates. As a consequence, the measurement information gathered during a single calibration run permits calculation of several estimations of an analytical result, in both the interpolative and extrapolative manner. Since some estimations are independent of each other, the final result is reliable in terms of accuracy, more than if using a conventional calibration approach. Owing to the instrumental simplicity and analytical efficiency, the system is expected to be useful for routine analysis.
Calibration

"On-line Monitoring Of R-captopril Using An Amperometric Biosensor/sequential Injection Analysis System"
Instrum. Sci. Technol. 2002 Volume 30, Issue 3 Pages 243-250
Raluca-Ioana Stefan, Jacobus (Koos) F. van Staden, Hassan Y. Aboul-Enein

Abstract: An automated system for the on-line monitoring of R-captopril, based on the concept of sequential injection analysis with an amperometric biosensor (based on D-amino acid oxidase) as detector, is described. The sampling rate is 80 samples per hour with an RSD < 0.22% in the linear range between 0.2 and 1.0 µmol/L. The detection limit is 160 nmol/L.
Automation

"Multi-sugar Analysis System Using A Novel Glucose-3-dehydrogenase Electrode"
Instrum. Sci. Technol. 2002 Volume 30, Issue 1 Pages 97-105
T. Hamafuji; Y. Takano; W. Tsugawa; K. Sode

Abstract: A flavoenzyme, glucose-3-dehydrogenase (G3DH) from Halomonas sp. ?-15 strain, possessed broad substrate specificity and site-specific reaction against various sugars. We constructed an amperometric enzyme electrode employing G3DH and also developed a multi-sugar analysis system combined with the G3DH sensor and sugar analysis chromatography. This system can discriminate the 4 components of sugar, i.e., glucose, 1,5-anhydro-D-glucitol, trehalose, and N-carbamoyl-?-D-glucopyranosylamine mixture and it can determine each concentration from 2 mM to 10 mM.

"Simple Laboratory-made Automated Sequential Injection Analysis (SIA) Device. 1. Design And Testing Of The Hardware Component"
Instrum. Sci. Technol. 2002 Volume 30, Issue 1 Pages 13-20
Petr Solich, Antonin Svoboda, Hana Sklenarova, Miroslav Polasek, Rolf Karlicek

Abstract: UFL

"AN AUTOMATED SPECIATION ANALYSER OF ORGANOMETALLIC COMPOUND CONTENT"
Instrum. Sci. Technol. 2001 Volume 29, Issue 5 Pages 393-405
Andrzej Wasik, Ryszard Lobinski, Jacek Namiesnik

Abstract: This paper presents the design of an automated measurement device developed for speciation studies of organometallic compounds in samples of a complex and varying composition matrix. The instrument automates three essential steps in a typical speciation analysis procedure: isolation of analytes, their enrichment, and time-resolved introduction into a detector. Analytes are extracted by purging from post-sample dissolution/digestion mixture, in the form of volatile derivatives, with their simultaneous enrichment on a capillary cryotrap. Before introduction into a detector, they are rapidly (ca. 0.5 min.) separated on a multi-capillary gas chromatographic column operating in isothermal mode. The construction of the automated speciation analyzer. (ASA) makes it practically independent of a kind of the detector used (it was tested with MIP-AED,[1] ICP-MS,[2] and AAS detectors) and gives the freedom of choice of sample preparation procedure. The only requirement to the latter is that analytes should be in a form of volatile compound in an aqueous matrix.

"Super Serpentine Reactors In SIA. A Comparative Response And Precision Study"
Instrum. Sci. Technol. 2001 Volume 29, Issue 2 Pages 77-89
E. B. Naidoo, J. F. van Staden

Abstract: Dispersion and zone overlapping play a very important role in SIA. Its control is the key to both the development of a methodology and its optimization. A tiron-iron (III) complex was used to investigate the influence super Serpentine reactors have on these two parameters using sensitivity and precision as the two measurement criteria with a spectrophotometer as detector. The SIA manifold is simple and the complexation reaction between tiron and iron (III) is fast enough such that dispersion and zone overlapping are the major role players contributing to the concentration gradient between the sample and reagent. Six different reactor types - a straight tube, a helically coiled tube and four super Serpentines I, II, III, and IV of four different lengths with an i.d. of 0.76 mm - were compared.

"AN APPROACH TO FLOW IMMUNOVOLTAMMETRIC ASSAYS ON HANGING MERCURY ELECTRODES"
Instrum. Sci. Technol. 2001 Volume 29, Issue 2 Pages 65-75
Cecilia Fern&aacute;ndez Bobes; M. Teresa Fern&aacute;ndez Abedul; Agust&iacute;n Costa Garc&iacute;a

Abstract: The electroanalytical behavior of DNP-albumin in a flow system, with the aim of developing immuno-polarographic assays is studied. A thin layer flow cell that includes a hanging mercury drop electrode is employed and differential pulse voltammograms are recorded. The influence of parameters such as drop size, flow rate, loop volume, pulse amplitude, cleaning, and stopped-flow times on the analytical signal is investigated. A flow system is designed for carrying out the recirculation of DNP-albumin; its interaction with specific antibodies is discussed.

"Molecularly Imprinted Polymer Library On A Microtiter Plate. High-throughput Synthesis And Assessment Of Cinchona Alkaloid-imprinted Polymers"
Instrum. Sci. Technol. 2001 Volume 29, Issue 1 Pages 1-9
Toshifumi Takeuchi; Akinobu Seko; Jun Matsui; Takashi Mukawa

Abstract: A molecularly imprinted polymer library was prepared on a 96-well microtiter plate, using a liquid-handing equipment that was programmed to prepare various breeds of cinchonidine-imprinted polymers. The resultant polymers, immobilized on the bottom surface of the wells, were screened for the binding capacity by fluorescence measurement, using a microplate reader. Comparison with a conventional assessment by FIA (flow injection analysis) demonstrated the reliability and the high-throughput performance of the microtiter plate-based combinatorial molecular imprinting.

"Influence Of Single Bead String Reactors On Zone Penetration And The Isodispersion Point In Sequential Injection Analysis"
Instrum. Sci. Technol. 1999 Volume 27, Issue 3 Pages 167-180
J. F. Van Staden; T. McCormack

Abstract: A non-reactive dye was used to investigate the effect, that a single bead string reactor (SBSR) has upon the isodispersion point and the degree of zone penetration of the sample and reagent zones in a simple sequential injection system. The length of SBSR, the pump speed (flow rate) and the volume ratios of both the sample and reagent zones in a total constant volume were parameters that were studied with the SBSR at one of two positions, either before the detector or between the selection valve, and the holding coil.
Optimization Dispersion Enzyme

"A Novel Immobilized Enzyme Flow Injection System For Urea With A Bulk Acoustic Wave Impedance Sensor As Detector"
Instrum. Sci. Technol. 1999 Volume 27, Issue 1 Pages 31-43
Xiao-Li Su; Hu-Wei Tan; Li-Li Bao; Wan-Zhi Wei; Shou-Zhuo Yao

Abstract: The urea-urease system was chosen as a model system to explore the suitability for the use of a bulk acoustic wave impedance sensor (BAWIS) as a detector in an immobilized enzyme FIA system. In the proposed FIA sysem, the urea in samples was hydrolyzed into ammonium and bicarbonate under the catalysis of the immobilized urease. The ammonium formed was converted into ammonia in an alkaline stream, and the ammonia diffused across a gas-permeable membrane into a recipient solution of dilute hydrochloric acid. The conductance change caused by the trapped ammonia was followed by a BAWIS detector. The system was applied to the analysis of urea in blood and urine samples. It exhibited a linear frequency response up to 10 mM urea with a detection limit of 10 µM. The through-put was 50 hr-1, and the relative standard deviation of the peak heights (n=6) ranged between 0.63-1.97%. The effects of several factors, including those affecting the enzymatic reaction, detector performance, and gas-diffusion process, were also investigated. Compared with those conventional enzymatic methods for urea determination, the proposed immobilized urease FIA/BAWIS system is characterized by its rapid throughput, high reproducibility, low-cost apparatus, and easy manipulation.

"Determination Of Reaction Stoichiometries By Using The Sequential Injection Analysis Technique"
Instrum. Sci. Technol. 1999 Volume 27, Issue 1 Pages 1-11
J. F. Van Staden; H. du Plessis; R. E. Taljaard

Abstract: A simple and reliable sequential injection analysis system is proposed to determine the reaction stoichiometries of different complexes. In this study, the Fe(III)/Tiron complex as 1:1 complex and the Fe(II)/1,10-phenanthroline complex as 1:3 complex were evaluated. The importance of the correct reagent order, as well as the need for thorough mixing, is highlighted.

"A Converging Wall-jet Instrument For Ion Selective Electrode Dynamic Response Studies"
Instrum. Sci. Technol. 1998 Volume 26, Issue 5 Pages 461-472
Michael L. Clay; Russell E. Pierce; Vaneica Y. Young; Steve Hoke

Abstract: Ion selective electrodes are used to conduct real-time measurements of gaseous thermal degradation products from halon replacement experiments. Response characteristics of these ion selective electrodes are needed to address potential interferences and surface poisoning experienced under field conditions. The design and the fabrication of an in situ, converging wall-jet instrument for the measurement of the dynamic responses of ion selective electrodes are described. Various time delays associated with the generation and detection of ion activity steps have been quantitatively determined. Dynamic response measurements for iodide steps on a Corning iodide/cyanide ion selective electrode are comparable to those obtained on the best of the earlier instrument designs, the in situ, switched wall-jet instrument. The advantages of the converging wall-jet instrument over the switched wall-jet instrument are identified.
Bromide Nitrate Electrode

"Development Of A Four-channel Potentiostat For Amperometric Detection In Flow Injection Analysis"
Instrum. Sci. Technol. 1998 Volume 26, Issue 5 Pages 451-459
Renato C. Matos; Lucio Angnes; Claudimir do Lago

Abstract: A four-channel multipotentiostat was developed for simultaneous voltammetric measurements with microelectrode arrays. To reduce the complexity of electrochemical cell, only one reference and one auxiliary electrode were used. The potential ranges of the four working electrodes may be independently controlled, but they are synchronously scanned by only one DAC. This is accomplished through a microcomputer interfaced with a PCL-711B data acquisition board, which allows the continuous monitoring of the currents and actual potentials of the working electrodes. The system was applied to the simultaneous determination of ascorbic and uric acids in synthetic samples. The measurements were carried out with gold microelectrodes modified by deposition of noble metals, which enhance the electrocatalysis and provide an anticipation and a better definition of the oxidation potentials. Recuperation of 98.2% and 97.8% for ascorbic and uric acids, respectically, was obtained by using amperometry.
Ascorbic acid Uric acid Amperometry Voltammetry Electrode Electrode Simultaneous analysis Apparatus Detector Computer

"Determination Of Diffusion Coefficients Of Proteins By Flow Injection Analysis And Its Application To Estimation Of Molecular Masses Of Proteins"
Instrum. Sci. Technol. 1998 Volume 26, Issue 4 Pages 333-341
Mohammed Ibrahim; Zou Gongwei; Zhu Junjie

Abstract: A flow injection analysis (FIA) method for determination of molecular diffusion coefficients (Dm) of proteins, in a helically coiled tube, was reported. The coiling effect of the tube that causes secondary flow was avoided through using a Taylor-Aris and Golay's dispersion equation, modified by the velocity profile factor, K, and the modified equation was used for direct determination of diffusion coefficients. The experimental values of Dm were comparable with the literature values. The linear relationship between the Relative Molecular Mass (RMM, Mr) and the Molecular Diffusion Coefficients (Dm) was verified and a two-point calibration FIA method for estimation of Relative Molecular Masses of proteins was suggested. Relative molecular masses of two protein samples, Hb and glucose oxidase were then estimated by this method. The values of RMM were 6.88 x 10^4 for Hb and 16.0 x 10^4 for glucose oxidase.
Protein, diffusion coefficient Enzyme, glucose oxidase Theory Diffusion coefficients

"SIRE-technology. 2. Glucose Tolerance Monitoring, After A Peroral Intake, Employing Small Volume Whole Blood Measurement With An Amperometric Biosensor"
Instrum. Sci. Technol. 1998 Volume 26, Issue 1 Pages 59-67
K. A. Johnson; D. Kriz

Abstract: A biosensor based on the flow injection of the recognition element (glucose oxidase) was applied to small volume (30 l) whole blood samples for the determination of glucose (I). The SIRE (sensors with injectable recognition elements) exhibited a linear response up to 12 mM I. The repeatability was 5.1% (n = 11) and the reproducibility (n = 4) was 8% for standard I solutions. The results obtained by the SIRE biosensor compared well with those obtained using a commercial device (Medisense, USA). Multi-analyte analysis is possible with the SIRE by simply sequentially injecting several different enzymes.
Glucose Whole Human Amperometry Sensor

"SIRE-technology. 1. Amperometric Biosensor Based On Flow Injection Of The Recognition Element And Differential Measurements"
Instrum. Sci. Technol. 1998 Volume 26, Issue 1 Pages 45-57
D. Kriz; C. Berggren; A. Johansson; R. J. Ansell

Abstract: An amperometric biosensor with injection of the recognition element (SIRE) is described. An oxidase enzyme is injected into the measuring chamber, separated from the sample by a semi-permeable membrane. It is possible to make measurements in the presence and absence of enzyme and subtract the background current. This differential measuring technique has been difficult with previous sensors because it is very difficult to match two sensors. The versatility of the biosensor was demonstrated by determination of several different metabolites (glucose, lactate, Ph alanine, and galactose). The system was not optimized for the individual analytes, but showed a linear response for each up to approximately 10 mM. For glucose, a detection limit of approximately 2 µM was achieved. By using the differential measuring technique, glucose could be determined by direct measurement in a urine sample with the standard addition method. The repeatability was found to be lower than 3.7 % (n=5) over the range 0.3-5.0 mM for glucose, and the reproducibility better than 5 % (n=5). The biosensor showed no decrease in response at temps. up to 60°C and could easily be cleaned with a solution of hydrogen peroxide and by sweeping of the potential. Thus, this amperometric biosensor was found to have several advantages compared to conventional ones.
Glucose Lactate Phenylalanine Galactose Urine Amperometry Sensor Membrane Standard additions calibration Differential detection Apparatus

"Analyte Enrichment Using Sequential-injection Analysis"
Instrum. Sci. Technol. 1997 Volume 25, Issue 4 Pages 307-320
Graham D. Marshall; Jacobus F. van Staden

Abstract: Sequential-injection anal. (SIA) was developed as part of the drive to develop methods of automated anal. suitable for robust process anal. As such, it was envisaged that SIA should provide a means of sample manipulation for the automation of wet chemical procedures in the process environment. Of particular note, SIA was seen to offer the possibility of carrying out complex sample manipulation in a simple manifold. This paper demonstrates how the unit operation of trace enrichment is conveniently accommodated in a sequential-injection manifold. As test case, the familiar pre-concentration. of copper using sodium diethyldithiocarbamate on a polymeric support is described.
Copper Sequential injection Preconcentration Diethyldithiocarbamate

"Development Of A Three-electrode Cell Containing A Polypyrrole-coated Auxiliary Electrode"
Instrum. Sci. Technol. 1997 Volume 25, Issue 1 Pages 29-38
K. A. Johnson; D. Kriz

Abstract: The flow cell (construction described) comprised also a Pt working electrode and an Ag/AgCl reference electrode. When the cell was used in the flow injection determination of morphine (injection volume 0.5 ml; carrier stream 20 mM citrate buffer of pH 6.0), the working electrode was maintained at +500 mV. The range of linear response was increased to up to 8 mg/l as compared with up to only 2 mg/l in the absence of the polypyrrole coating, and the repeatability and reproducibility RSD (n = 5) were 1.9 and 6.1%, respectively. The presence of the polypyrrole layer permitted the size of the auxiliary electrode to be decreased.
Morphine Voltammetry Electrode Buffer

"Design Considerations For Capillary Flow Injection Systems"
Instrum. Sci. Technol. 1996 Volume 24, Issue 2 Pages 103-113
D. M. Spence; A. M. Sekelsky; S. R. Crouch

Abstract: Design considerations for performing capillary flow injection (CFI) with conventional peristaltic pumping are presented. A time based injection technique has been developed so that sample volumes in the sub nL to mL range can be used without internal or external injection loops. In addition, two flow cells have been designed and constructed in order to measure absorbances with such small sample volumes. Commercially available connectors for fused silica capillaries have also been used in a CFI system enabling the operation of multiple reagent systems.

"A Versatile Computer-controlled Amperometric Detector For High Performance Liquid Chromatography And Flow Injection Analysis"
Instrum. Sci. Technol. 1996 Volume 24, Issue 1 Pages 1-11
C. A. M. Lillo; M. R. Romero; J. M. Marioli

Abstract: The potentiostat (circuit diagram presented) is built from National Semiconductor LP324 micropower quad operational amplifiers, which are suitable for operation under battery power, as in the proposed system, to minimize source noise. The working electrode consists of a 1 mm diameter Ni/Cr (4:1) wire embedded in Kel-F, the auxiliary electrode is a stainless-steel block drilled for passage of the liquid stream, and an Ag/AgCl (3 M KCl) reference electrode is used. The potentiostat is connected through an eight bit analogue-to-digital/digital-to-analogue conversion card to a PC, which is programmed in Borland Turbo Pascal 7.0 to control the potentiostat (the potential can be set from -1 to +1 V in steps of 0.01 V) and in Turbo Pascal Graphix Toolbox 4.0 to display the current (sampled at four points per s) as a function of time. The screen is illustrated for the repetitive injection of 20 µL portions of 0.01 M glycine in FIA. The system can easily be upgraded (e.g., by substitution of a 12 bit conversion card).
HPLC Amperometry Computer

"Automated Titrations With An Alternate Flow: Linear Speed Variation System"
Instrum. Sci. Technol. 1995 Volume 23, Issue 2 Pages 91-102
Chaim N. Yarnitzky; Naphtali Klein; Orit Cohen

Abstract: The alternate-flow exponential speed-variation titrimeter described previously (Talanta, 1993, 40, 1937), which consists of two computer-controlled peristaltic pumps, two three-way valves, a mixing coil and a detector, can be operated in linear speed-variation mode. The rotation speed of the first (sample) pump decreases linearly with time while that of the second (reagent) pump increases likewise; the effects of deterioration of the tubing are eliminated by a reverse cycle effected by use of the valves. The system is suitable for rapid automated titrimetry; a complete titration takes <2 min. The accuracy depends on the mixing-coil delay and the time response of the detector, but at a fourfold sample-to-reagent concentration ratio the error is <0.5% and decreases as this ratio approaches unity. The performance of the system is demonstrated with acid-base and redox systems.
Titrations Flow reversal

"Multiplexed Four-channel Online Iodine Monitor"
Instrum. Sci. Technol. 1994 Volume 22, Issue 3 Pages 217-229
J. E. Atwater; R. R. Wheeler Jr.; R. L. Sauer; J. R. Schultz

Abstract: A PC controls four three-way PTFE solenoid valves (via an ACCESS IOD-24 buffered 24 bit digital I/O card that controls eight relays on an ACCESS ROB-8 board) to multiplex up to four sample streams into the flow cell of a diode-array spectrophotometer interfaced to the PC through an IEEE-488 parallel bus. The remaining four relays of the ROB-8 board multiplex K-type thermocouples in each of the streams to a digital thermometer that is connected to the PC through an RS 232 serial link. Iodine in drinking water for use on spacecraft, and also in, e.g., humidity condensate, urine distillate and reclaimed hygiene water, is determined at 464 nm after subtraction of the background absorbance at 600 nm. The response is linear for up to 10, 25 and 300 mg/l of I2 in all these matrices (calibration with aqueous standards prepared from refrigerated ethanol containing 1 g/l of I2) in flow cells of pathlengths 10, 5 and 1 cm, respectively. Separate failures of the deuterium lamp and its power supply and the necessity for replacement of two relays and three valves were the only causes of downtime during otherwise continuous operation for 18 months.
Iodine Water Urine Spectrophotometry

"Millisecond Time-scale UV-visible Spectrophotometer Based On A Double-diode Array Detector Coupled To A Stopped-flow Instrument"
Instrum. Sci. Technol. 1994 Volume 22, Issue 1 Pages 13-23
Achim Gerhard; Wolfgang Gaede; Anton Neubrand; Volker Zang; Rudi van Eldik; Peter Stanitzeck

Abstract: A UV-visible rapid-scan spectrometer consisting of a double-diode-array optical simultaneous multi-channel analyzer. (SI Spectroscopy Instruments GmbH, Gilching, Germany) coupled with a standard stopped-flow instrument was constructed (details given). The system enabled the direct recording of absorbance spectra on a real time base, with good optical resolution in the millisecond time range, as well as absorbance-time traces as a function of wavelength. Details are given of calibration procedures and a series of typical measurements of the electron transfer reaction between hexacyanoferrate(III) and L-ascorbic acid are presented to demonstrate the performance of the system. Results are discussed.
Hexacyanoferrate(III) Ascorbic acid Spectrophotometry Stopped-flow

"Computer-aided Flow Analysis For Laboratory Use And Process Analysis"
Instrum. Sci. Technol. 1992 Volume 20, Issue 1 Pages 79-100
Graham D. Marshall; Jacobus F. van Staden

Abstract: Sequential injection analysis is an automated flow system for mixing reagents and carrying them to a suitable detector. A software package which enables the easy automation of flow-based analysis systems is described. The structure of the Flowtek program, the method design and development, data acquisition and instrument control, control by procedures, calibration, diagnostics using the history option and system performance are outlined. Flow-based methods of anal. such as flow injection analysis and sequential injection analysis are being used increasingly in the automation of lab. methods and for process anal. Full exploitation of these techniques in automated modes of operation necessitates computer control and data acquisition. Although most commercial systems are microprocessor driven, flexibility is seldom built into the software, thereby severely limiting the ingenuity of the anal. in the use of these instruments in novel and imaginative applications. A software package is described which allows for easy automation of flow-based anal. systems. The emphasis in the design of this package has been on flexibility, with numerous user-selected options and a wide variety of features. Applications to lab. and plant analyzers are described.
Computer Process control Sequential injection

"Versatile Pump Controller For Continuous-flow Methods"
Instrum. Sci. Technol. 1990 Volume 19, Issue 4 Pages 167-180
Peter D. Wentzell; Nils G. Sundin

Abstract: A computer-driven pump controller capable of providing voltage, current and pulsed outputs for up to five pumps in analytical systems is described. The controller is ideal for situations which require remote control of speed and direction for many pumps of different types. The design is based on the Advanced Micro Devices 9513 system timer chip and provides 0-10 V, 0-25 mA and pulsed TTL outputs to control each pump. In addition, phase-locked loop circuitry allows feedback for speed regulation of certain pumps. For control of stop/start, direction or other functions, eight independently programmable TTL outputs are provided. The controller is inexpensive and designed to be driven from the parallel printer port of an IBM PC compatible computer for maximum portability. Other uses of the interface are also possible.
Computer

"Microcomputer-based Experiment Control And Detection System For Flow Injection Analysis"
Instrum. Sci. Technol. 1989 Volume 18, Issue 1 Pages 1-21
Gregory D. Clark; Gary D. Christian; Jaromir Ruzicka; Gary F. Anderson; James A. van Zee

Abstract: A modular flow injection analysis system is described with an optical fiber-based spectrophotometric detector. The circuit diagram for the linear gain amplifier and four-pole filter, details of the interface to an IBM XT PC, a dendrogram showing the most important computer subroutines and functions, and the data acquistion, experimental control, and data evaluation and storage procedures are given. The performance of the system was evaluated with bromocresol green as test analyte and 10 mM borate buffer as carrier solution; response was rectilinear from 5.75 to 23 µM.
Bromocresol green Spectrophotometry Optical fiber Detector Buffer Computer