Electrocatalysis in Stripping Voltammetry of Sulfur Compounds

This contribution reviews some applications of electrocatalysis in indirect stripping voltammetry of electrochemically inactive sulfur compounds, that are not amenable to the detection by direct electron transfer reactions. As a first example, ligand-catalyzed metal ion reduction on a mercury electrode will be dealt with . Electrocatalysis of Ni(II) or Co(II) reduction by compounds like cysteine and its derivatives as well as other thiol derivatives (penicillamine, mercaptopurine derivatives) enables the sensitive detection of the ligand itself. The analyte can be accumulated either as an adsorbed nickel complex or as a sparingly soluble mercury salt, according to the accumulation potential and the stability of the nickel complex. The occurrenceof two different accumulation mechanisms enables much flexibility when dealing with interferences. Second, catalytic hydrogen evolution in the presence of Co(II) and sulfide ion will be approached, with a focus on the determination of sulfide ion atthe trace level a. The same electrode process can be employed for the determination of sulfur organic derivatives that generate sulfide ions by a chemical reaction during the pre-concentration step on a mercury electrode.