VOLTAMMETRIC DETECTION OF SILVER(I) USING A CARBON-PASTE ELECTRODE MODIFIED WITH KERATIN

The voltammetric detection of silver(I) was carried out at a carbon pa ste electrode (CPE) modified with keratin. Silver(I) was selectively a ccumulated on the electrode on the basis of its interaction with the t hiol and disulfide groups of keratin in 0.1 mol dm(-3) acetate buffer (pH 6.7) + 0.1 mol dm(-3) NaClO4. After reduction of silver(I) had bee n carried out, the reoxidation wave of silver(0) appeared at 0.14 V (v ersus Ag/AgCl) on scanning the potential in the positive direction in 0.1 mol dm(-3) acetate buffer (pH 6.7). The detection limit of silver( I) was 2 x 10(-8) mol dm(-3) when the accumulation time was 10 min. In terference from co-existing substances was slight in the voltammetric measurement because of the interaction with sulfur atoms and the excha nge of the medium. The proposed method was applied to the determinatio n of silver(I) in a photographic developer.