Determination of trace tin by stripping potentiostatic coulometry

On the basis of voltammetric and coulometric studies of the behavior of tin(II) in a 2 M HCl solution at a carbon-graphite bulky electrode made of fibrous porous felt (FPF), we have found the optimum conditions for the stripping potentiostatic coulometric determination of 10–1000 μg tin(II) by the reaction Sn(0)-ē ? Sn(I) after preconcentrating Sn(0) at the electrode surface. The relative standard deviation varied from 0.5 to 4%. The results of the coulometric determination of the number of electrons involved in the oxidation of Sn(0) suggest that the stripping Sn(0) from the surface of the FPF electrode proceeds in two stages. The first stage Sn(0) → Sn(I) was electrochemical, and the second stage Sn(I) → Sn(II) was chemical. The procedure was applied to the determination of ～1% tin in a jewelry alloy based on gold, silver, platinum, and copper.