Preparation and characterization of a polymer-modified mercury film electrode for selenium(IV)

A polymer-modified mercury film electrode to be used in voltammetric determination of selenium (IV) was prepared and characterised. The anion-exchanger (quaternary phosphonium exchange-sites) polymer film was obtained by physical deposition onto a glassy carbon electrode which was mercury plated (potentiostatically at -0.6 V). Before use, the electrode was suitably conditioned. The electrode was characterised (influence of the most important experimental parameters on the electrode response) by both cyclic and linear sweep cathodic stripping voltammetry. The linear sweep cathodic stripping voltammetric signal (180 s of accumulation time at 0.0 V) is linear versus selenium concentration from 2 10(-8) to 1 10(-6) mol l(-1), thanks to the enhancing effect exploited by Cr (VI) (1 10(-6) mol l(-1)) added to the sample. The precision at 7 10(-7) mol l(-1) of selenium, is +/- 4% (five runs). The interference of several metals and surfactants was also evaluated and the electrode tested in actual water samples.