Abstract
The behaviour of the Se(+4)−Se(0)−Se(−2) system was studied by cyclic and stripping voltammetry using several kinds of graphite and glassy carbon electrodes in the pH range from 0 to 8. Well-defined curves of Se(+4) reduction were obtained with a very soft graphite electrode, whereas poorly defined curves were recorded with glassy carbon electrodes. The reduction of Se(+4) in acid solution led to the formation of two forms of elemental selenium. One was formed in a direct electroreduction and the other in a subsequent chemical reaction between Se(+4) and Se(−2). These two forms of Se(0) gave separate reduction and oxidation peaks. Hydrogen selenide was anodically oxidized stepwise to elemental selenium and selenous acid. With an increase of pH the extent of Se(+4) reduction decreased and the extent of Se(−2) oxidation increased. The cathodic and anodic stripping peaks of elemental selenium cannot be used for the determination of traces of Se(+4) because they appear only in solutions with Se(+4) concentrations >1×10 −5 mol 1 −1.
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