Cathodic stripping mechanism of an insoluble salt coupled with a homogenous chemical reaction is considered both theoretically and experimentally under conditions of square-wave voltammetry. For the mercury electrode in aqueous solution, the electrode reaction is described as L(aq) + Hg(l) = HgL(s) + 2e À , where L(aq) is the reactive ligand that forms a sparingly soluble compound HgL(s). The electrode reaction is coupled with a homogenous, first-order chemical reaction, A(aq) = L(aq). Theoretical predictions are confirmed by experiments with 6-mercaptopurine-9-driboside in the presence of nickel(II) ions.