Sammendrag
Microelectrodes of silver-copper alloys have been evaluated for use in voltammetric analyses. Increased overpotential towards the hydrogen overvoltage reaction (HER) was found as function of increased copper amount in the silver. A study of oxidizing products by cyclic voltammetry (CV) in NaOH solution showed ten anodic and eight cathodic peaks which are described in the present paper. It was found that these alloy electrodes behave somewhat between pure silver and pure copper electrodes. Differential pulse anodic stripping voltammetry (DPASV) was used to measure zinc, cadmium and lead in ultrapure water only (18 M), and good linearity was found for all metals (r2=0.998) in the range of 0.5 to 5 ppb with 600 to 1200 s plating time. It was additionally found that cadmium and lead were better separated on the alloy electrodes compared to pure silver electrodes. Measurements of nickel were carried out on alloy electrodes by use of adsorptive differential pulse cathodic stripping voltammetry (Ad-DPCSV), and good linearity (r2=1.000) was found in the range of 0.5 to 5 ppb with an adsorption time of 30 s. The alloy electrodes was also found to be sensitive to nitrate, and a good linearity (r2=0.997) was found in the range of 1 mg/L 100 mg/L using differential pulse voltammetry (DPV) scanning from -450 mV to -1500 mV. Addition of nitrate in ultrapure water exhibit two different peaks related to the successive reductions of nitrate and nitrite. In ammonium buffer solution (pH 8.6) only one peak resulting from reduction of nitrate was observed. Further, the use of alloy electrodes containing 17 % Cu was tested in real samples, by installing it in a voltammetric system for a monitoring of zinc and lead in a polluted river, Deûle, near the town of Douai in northern France. Results were found to be in agreement with parallel measurements carried out by ICP-MS.
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