Determination of ultra-trace mercury(II) by flow-injection/anodic stripping voltammetry using a track-etched microporous membrane electrode.

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.

A dual-electrode flow sensor fabricated using track-etched microporous membranes.

A new dual-electrode flow sensor has been fabricated by piling the microporous membrane electrodes which have 7-10µm thickness. The electrode was prepared by sputtering of platinum onto both sides of the membrane filter which contain a smooth flat surface as well as cylindrical pores with uniform diameters. The electrolysis is performed when the sample solution flows through the membrane electrode, and a generated analyte on the first working electrode is instantaneously transported to the surface of second working electrode which is located at the downstream of the first one. In this case, the sample solution surely flows through the pores of the membrane filters. As the result, highly efficient electrolysis was achieved at each electrode, and the collection efficiency values as high as 100% were obtained in the wide range of flow rate. Good responses to the injections of sample solutions were also confirmed in the FIA system.