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
Website: @unf

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Classification: Electrode -> graphite -> paste

Citations 10

"Graphite Paste Based Enzymatic Glucose Electrode For Flow Injection Analysis"
Analyst 1988 Volume 113, Issue 5 Pages 735-738

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Wojciech Matuszewski and Marek Trojanowicz

Abstract: The electrode was prepared from a mixture of graphite powder, silicone oil and glucose oxidase, and was used with a wall-jet flow-through cell at +0.9 V vs. Ag - AgCl. Response was rectilinear up to 30 mM glucose (40 µL injection) with a detection limit, for 750 µL injections, of 20 µM in 0.1 M phosphate buffer (pH 6.5) at 1 mL min-1. In the analysis of soft drinks, recoveries of glucose added at the 2 to 20 mM level were between 91.8 and 105.1%. Up to 120 samples h-1 could be analyzed.
Glucose Soft drink Calibration Optimization

"Reactive Electrode (reactrode) For The Voltammetric Determination Of Heavy Metals In Laboratories And For Use As A Passive Monitor In Remote Analysis"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 237-241

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I. Helms and F. Scholz

Abstract: The electrode was prepared by heating a mixture of graphite powder (0.45 g), HYPHAN cellulose (0.25 g) and paraffin (0.45 g) and pressing the resulting paste into rods of diameter 0.5 mm. In the batch analysis technique, the metal ions were accumulated from a medium of pH 6 at open-circuit potential for 15 min. The electrode was transferred to an electrochemical cell containing 0.1 M KNO3/0.1 M acetic acid (20:1). A potential of -1.2 V (vs. Ag/AgCl) was applied for 250 s. Anodic stripping was effected by differential pulse voltammetry using a pulse amplitude of 50 mV. Detection limits for Pb, Hg and Cu were 0.11 µM, 50 nM and 0.24 µM, respectively. Of the cations investigated, only Fe(III) interfered. The method was also applied for FIA systems.
Metals, heavy Environmental Environmental Interferences Remote instrument

"An Amperometric Flow Injection Analysis Biosensor For Glucose Based On Graphite Paste Modified With Tetracyanoquinodimethane"
Anal. Biochem. 1993 Volume 214, Issue 1 Pages 233-237

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Pandey P. C., Glazier S. and Weetall H. H.

Abstract: A biosensor system using flow injection analysis (FIA) has been developed for the analysis of glucose in human serum. The system consists of the enzyme glucose oxidase incorporated into graphite paste modified with the electroactive material tetracyanoquinodimethane (TCNQ). TCNQ acts as an efficient mediator for oxidation of the reduced enzyme at 200 mV vs Ag/AgCl. The flow injection assay described has detection limits of 2 mM glucose using a 100 µL sample injection through a 250 µL sample loop. Data are presented to show the effect of sample injection volume and flow rate on the response of the FIA sensor. The biosensor exhibited excellent reproducibility for 800 injections. The loss of response after 800 injections was due to leaching of TCNQ from the graphite paste. Each assay takes 3 min giving a sample throughput of 20 per hour at a flow rate of 30 ml/h. The sensor was applied to the determination of glucose in human serum. The glucose measurements are in good agreement with those of a commercially available spectrophotometric method. Data showing the effect of interfering substances, ascorbic acid and acetaminophen, on the response of the sensor are also reported. A biosensor system was developed comprising glucose oxidase incorporated into a graphite paste modified with tetracyanoquinodimethane which acted as an efficient mediator for the oxidation of the reduced enzyme at 200 mV vs. Ag/AgCl. Serum (100 µL) was injected into a stream of 0.1 M phosphate buffer of pH 7 (30 ml/h) in a flow cell and the enzyme electrode was maintained at 200 mV vs. Ag/AgCl. The calibration graph was linear up to 200 mM glucose with a detection limit of 2 mM glucose. Total time for the procedure was 3 h with a sample throughput of 20/h.
Glucose Serum Human Method comparison Redox Interferences

"Tetracyanoquinodimethane-mediated Flow Injection Analysis Electrochemical Sensor For NADH Coupled With Dehydrogenase Enzymes"
Anal. Biochem. 1994 Volume 221, Issue 2 Pages 392-396

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Pandey P. C.

Abstract: A flow injection analysis (FIA) sensor for the oxidation of NADH is reported. The system utilizes a graphite paste electrode modified with the electroactive material tetracyanoquinodimethane (TCNQ). TCNQ acts as an efficient mediator for the oxidation of NADH to biologically active NAD+. Alcohol dehydrogenase/lactate dehydrogenase and NAD+ were coimmobilized in TCNQ-modified graphite paste using polyethylenimine to develop a FIA sensor for ethanol/lactate. The system responded rapidly with wide linearity. Response curves for ethanol/lactate and NADH are reported.
Nicotinamide adenine dinucleotide reduced Biological Redox Immobilized enzyme

"Peroxidase- And Tetracyanoquinodimethane-modified Graphite Paste Electrode For The Measurement Of Glucose/lactate/glutamate Using Enzyme-packed Bed Reactor"
Anal. Biochem. 1995 Volume 224, Issue 1 Pages 428-433

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Pandey P. C. and Weetall H. H.

Abstract: A flow injection analysis sensor for the measurement of glucose/lactate/glutamate is reported. The glucose oxidase/glutamate oxidase/lactate oxidase was immobilized on silanized controlled pore glass particles and packed into a Teflon column (i.d., 1.2 mm; length, 40 mm) to give a bed for glucose/lactate/glutamate. The hydrogen peroxide formed by the enzymatic reaction in the packed bed was monitored by a horseradish peroxidase- and tetracyanoquinodimethane (TCNQ)- modified graphite paste electrode at 50 mV vs Ag/AgCl. The glucose oxidase/lactate oxidase/glutamate oxidase were regenerated in the packed bed, whereas peroxidase was regenerated in the TCNQ-mediated graphite paste electrode by the oxidation of TCNQ. The oxidized TCNQ was electrochemically reduced at 50 mV vs Ag/AgCl. The cathodic current obtained by the reduction of TCNQ determined the concentration of the injected analytes in the packed bed. The system showed very rapid response. Response curves for the analysis of peroxide, glucose, lactate, and glutamate are reported.
Glucose Lactate Glutamate Immobilized enzyme Controlled pore glass Column

"Catalytic Oxidation Of NADH At A Methylene-green Chemically Modified Electrode And FIA Applications"
Anal. Lett. 1995 Volume 28, Issue 9 Pages 1579-1591

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Chen, H.Y.;Yu, A.M.;Han, J.L.;Mi, Y.Z.

Abstract: Graphite powder (0.98 g) was mixed with 0.02 g Methylene Green in 5 mL ethanol, the solvent was evaporated off and a portion (0.5 g) of the resulting powder was mixed with 0.3 mL Nujol oil. The resulting modified C paste was packed into an electrode body to form the NADH sensor. For FIA, the sensor was incorporated into an electrochemical thin-layer cell comprising two plexiglass blocks tightly compressing a 50 µm PTFE film with a 13 x 5 mm channel. Samples (20 µL) were injected into a stream (2 ml/min) of 0.1 M phosphate buffer of pH 7 and Pt wire counter and SCE references electrodes were used for the measurements. At a potential of 0.2 V, the calibration graph was linear for 5-1000 µM-NADH and the detection limit was 1 pmol. The RSD were 1% (n = 10).
Nicotinamide adenine dinucleotide reduced

"Horse-radish-root-modified Carbon Paste Bioelectrode"
Electroanalysis 1989 Volume 1, Issue 1 Pages 43-48

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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 Apparatus Detector Buffer Interferences

"Multi-enzyme-containing Tissue-based And Ferrocene-mediated Bioelectrode For The Determination Of Polyamines"
Electroanalysis 1992 Volume 4, Issue 5 Pages 521-525

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Meng Shan Lin, Minoru Hare, Garry A. Rechnitz

Abstract: Ground oat seedling tissue (which contains polyamine oxidase and peroxidase) was mixed with 2 to 9% (w/w) of graphite - mineral oil (3:2) paste containing 2% of ferrocene, and the mixture was firmly packed into the cavity of a flow cell electrochemical detector or, for steady-state experiments, into the end of a tubular electrode (3 mm i.d.). The electrode tip was smoothed on paper. Polyamine oxidase catalyses the oxidation of polyamines, O as co-substrate is reduced to H2O2, and the peroxidase then oxidizes ferrocene to ferricinium at the expense of H2O2; the signal is monitored reductively at 0.0 V vs. Ag - AgCl. Steady-state amperometric and cyclic voltammetric experiments were carried out in conjunction with a Pt-wire counter electrode; for a working electrode containing 7% of oat seedling tissue, response to spermidine or spermine in 0.1 M phosphate buffer of pH 7 was rectilinear up to 15 or 7.5 µM, respectively, and the corresponding detection limits were 0.19 and 1.15 µM. In the flow injection analyzes, carried out with the same buffer, the Ag - AgCl reference electrode was placed in a compartment downstream of the flow cell, with a stainless steel auxiliary electrode downstream of this, and PTFE tubing was used. Response to spermidine or spermine was rectilinear up to 20 or 15 µM, respectively. The electrodes did not respond to injections of 0.1 µM-ascorbic acid, uric acid, histamine, 4-aminobutyric acid or agmatine.
Amines, poly Spermidine Spermine Interferences

"An Amperometric Flow Injection Analysis Enzyme Sensor For Sucrose Using A Tetracyanoquinodimethane Modified Graphite-paste Electrode"
Biosens. Bioelectron. 1996 Volume 11, Issue 8 Pages 719-723

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J. L. Lima Filho, P. C. Pandey*, H. H. Weetall

Abstract: FIA systems for the determination of sucrose are described in which (i) invertase and µarotase were immobilized on to controlled pore glass beads in an enzyme reactor and the C-paste detection electrode was modified with glucose oxidase (I) and tetracyanoquinodimethane (II) as electron transfer mediator or (ii) invertase was incorporated into the C-paste electrode together with I and II (an enzyme reactor was not used). Both systems were operated with 0.1 M phosphate buffer of pH 7 as the carrier stream (30 ml/h) and a 250 µL sample loop. The amperometric response was measured at 200 mV vs. Ag/AgCl. The detection range was 0.025-200 mM for i and up to 2 M for ii.
Sucrose Controlled pore glass

"A Graphite Paste Electrode Containing Peroxidase And Its Application"
Bunseki Kagaku 1993 Volume 42, Issue 7 Pages 411-415

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Yao, T.;Haga, K.;Wasa, T.

Abstract: A mediator-less enzyme electrode for the detection of hydrogen peroxide was made up by packing {one end of a glass tube (5 mm diameter)} with a graphite paste composed of 0.3 g of graphite powder, 0. 18 mL of liquid paraffin, 6 mg of horse radish peroxidase (HRP) and 45 µL of glutaraldehyde (20 % solution). This electrode responded to hydrogen peroxide at 0 V (vs. Ag/AgCl) in the absence of a mediator such as hexacyanoferrate(II). The current response was found to be based on a direct electron transfer between the bound cofactor (ferriprotoporphyrin IX) in the immobilized HRP molecule and graphite particle. A logarithmic plot of the current response vs. the hydrogen peroxide concentration gave a straight line with a slope of 0.84 over the range of 2 X 10^-6 approximately 2 X 10^-4 M. Similarly, enzyme electrodes for glucose and uric acid were prepared by co-immobilizing HRP in the paste along with glucose oxidase and uricase, respectively, both of which were hydrogen peroxide-producing oxidases. Each of these electrodes responded to glucose or uric acid at 0 V. The current response was linearly related to the glucose or uric acid concentration, in the range of 2 X 10^-6 approximately 2 X 10^-3 M or 1 X 10^-5 approximately 2 X 10^-3 M. [References: 11]
Glucose Uric acid Immobilized enzyme