Analytical Sciences

Determination of Ultra-trace Mercury(II) by Flow-injection/Anodic Stripping Voltammetry Using a Track-etched Microporous Membrane Electrode

Hitoshi MIZUGUCHI,* Kentaro NUMATA,* Chiaki MONMA,* Masamitsu IIYAMA,** Kazuhiro TACHIBANA,* Tatsuo NISHINA,* and Junichi SHIDA*

*Graduate School of Science and Engineering, Yamagata University, Yonezawa 992-8510, Japan
**Nomura Micro Science Co., Ltd., 2-4-37 Okada, Atsugi, Kanagawa 243-0021, Japan

A new flow-injection/anodic stripping voltammetry has been demonstrated to assess ultra-trace mercury(II) using track-etched microporous membrane electrodes. The electrodes were prepared by the sputtering of gold or platinum onto both sides of a membrane filter with a smooth flat surface and with cylindrical pores having uniform diameter. The deposition of mercury from a mercury(II) solution was performed while the sample solution flowed through the membrane electrodes. After the deposition step, an anodic stripping voltammogram was obtained by sweeping the potential from 0 to +0.8 V vs. Ag/AgCl. In this case, the sample solution flowed through the pores of the 10-μm-thick membrane filters. Efficient electrolysis occurred during passage of the sample solution through the electrode, of which the pore size was 0.4 μm. In this study, the voltammetry described above was demonstrated using an FIA system. The continuous-flow mode showed a detection limit of 0.04 μg L⁻¹ when the experimental conditions of the flow rate and the deposition time were set at 0.5 mL min⁻¹ and 180 s. In the sample-injection mode equipped with a 1-mL sample loop, a linear relation was found for 0.5 – 4.0 μg L⁻¹ of a mercury(II) standard solution (r = 0.995). The detection limit was 0.05 μg L⁻¹. This method was applied to the ultra-trace determination of mercury(II) in river-water samples.

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