CYCLIC AND STRIPPING VOLTAMMETRY OF TIN IN THE PRESENCE OF LEAD IN PYROGALLOL MEDIUM AT HANGING AND FILM MERCURY-ELECTRODES

The influence of pyrogallol on the determination of traces of tin(IV) in the presence of lead was investigated by cyclic and stripping voltammetric technique at hanging drop and thin film mercury electrodes. The electroreduction of tin(IV) proceeds through an adsorption step; at more negative potentials, the adsorption process becomes limited and reduction ceases, particularly in stirred solutions. Such effects may decrease the sensitivity obtained for tin in anodic stripping voltammetry. Two methods are proposed for the determination of traces of tin(IV) in the presence of lead. In one, a silver-based mercury film electrode is used in a solution containing pyrogallol and oxalic acid; the peaks are thus separated by 90 mV, and the detection limit for tin, with a 10-fold amount of lead, is 2 × 10-8 mol l-1. In the second less-sensitive method, a HMDE is used in a solution containing pyrogallol and perchloric acid; the separation of the stripping peaks for tin and lead is then poor but tin(IV) can be determined from the peak corresponding to oxidation of tin(II) to tin(IV). © 1979.