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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Electrode

Classification: Electrode -> tungsten oxide

Citations 4

"Potentiometric Detection Of Carboxylic Acids By Flow Injection Analysis Using A Tungsten Oxide Electrode"
Anal. Chim. Acta 1996 Volume 332, Issue 2-3 Pages 187-192

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Zuliang Chen*, and Peter W. Alexander

Abstract: Carboxylic acids were determined by FIA with potentiometric detection at a tungsten oxide electrode (Ag/AgCl reference electrode). The optimum sensitivity was achieved with 0.5 mM phosphate buffer of pH 6.5 as the carrier stream (1 ml/min). Linear calibration graphs were obtained for 0.25-1.5 mM formic acid and 0.25-5 mM propionic acid and detection limits were 10 and 50 µM, respectively, with an injection volume of 20 µL. The RSD (n = 10) for the determination of 1 mM formic acid was 1.5%. The baseline potential did not exhibit any measurable drift.
Carboxylic acids Optimization Drift Buffer

"Flow Injection Potentiometric Detection Of Metal-ions Based On Tungsten-oxide Electrode"
Electroanalysis 1997 Volume 9, Issue 2 Pages 141-144

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Zuliang Chen, Peter W. Alexander

Abstract: The use of a tungsten oxide electrode for potentiometric flow injection analysis of transition metal ions is described. The effect of a variety of experimental conditions, including the carrier pH, the types of ligands and their concentrations, was studied. It was found that the best sensitivity for the ions tested was obtained using EDTA as a ligand. The electrode exhibited a linear response for Fe3+, Cu2+, Pb2+ and Ca2+ in the range of 2.5 x 10^-4 M to 2 x 10^-3 M using with 1 x 10^-3 M EDTA at pH 5.0 as carrier. The detection limits were found to be between 1 x 10^-5 to 5 x 10^-5 M. Reproducibility for Fe3+ was about 1.7% with a stable baseline potential. The method is based on the use of the FIA system of Alexander et al. (Anal. Lett., 1984, 17, 3 09) for the indirect determination of metals at a tungsten oxide wire electrode after complexation with EDTA. Sample (10 µL) was injected into a stream of 0.5 ml/min 1 mM EDTA with pH adjusted to 5 with 1 mM NaOH and Ag/AgCl as reference electrode. Calibration graphs were linear for 0.25-2 mM Fe3+, Cu2+, Pb2+ and Ca2+ with detection limits of 1, 50, 50 and 10 µM, respectively. In the determination of 1 mM Fe3+, the peak height RSD was 1.7% (n = 10). The effects of varying complexing agent molecule and concentration, carrier pH and flow rate on the determinations were studied. The results are compared with those obtained at a Cu electrode. 20 References
Calcium(2+) Copper(II) Iron(III) Lead(2+) EDTA Method comparison Optimization Complexation

"Potentiometric Detection Of Metal-ions Separated By Liquid-chromatography Using A Tungsten-oxide Electrode"
Electroanalysis 1997 Volume 9, Issue 11 Pages 818-821

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Zuliang Chen *, Peter W. Alexander

Abstract: The use of a tungsten oxide sensor for the potentiometric detection of metal ions separated by liquid chromatography is described. Separation of metal ions such as Fe3+, Fe2+. Cu2+ and Pb2+ was performed by ion chromatography using a mobile phase containing 25 mM sodium tartrate/2 mM ethylenediamine at pH 3.8. Calibration plots were linear in the range 0.5 to 3.5 mM. Potentiometric detection was also applied to ion-interaction chromatography. The results showed that separation of metal ions was improved and the detection limits for the test metals in the range of 0.5-5 nmol were obtained in the presence of sodium citrate/1-octanesulfonic acid at pH 3.0. The potentiometric detection described in this article is shown to base advantages in terms of low cost, simplicity and sensitivity. 23 References
Iron(III) Iron(2+) Copper(II) Lead(2+) Interferences

"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

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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 Apparatus Detector Remote instrument