STUDIES ON THE VOLTAMMETRIC BEHAVIOR OF A 2-MERCAPTOIMIDAZOLE CONTAINING CARBON-PASTE ELECTRODE - DETERMINATION OF TRACES OF SILVER

The voltammetric behaviour of a 2-mercaptoimidazole (2-MI) containing carbon paste electrode was studied. When mixed to carbon paste as an electrode modifier, 2-MI can be reduced at negative potentials (- 1 V vs. SCE), but it does not give a response in the potentials range where Ag(0) is oxidized to Ag(I). Silver could be accumulated from 0.1 mol l-1 acetate buffer onto a 2-MI modified carbon paste electrode without a potential applied; after medium exchange, it was reduced at -1 V vs. SCE in 0.1 mol l-1 acetate buffer solution and determined by differential pulse anodic stripping voltammetry. With suitable preconcentration times, the detection limit was 0.1 mug l-1; a linear relation between current and concentration was found to exist within a range of 0.5 to 1000 mug l-1. In the presence of EDTA, common metal ions have no or only little effect on the voltammetric determination of silver.