Determination of trace tin by catalytic adsorptive cathodic stripping voltammetry

A highly sensitive and selective catalytic adsorptive cathodic striping procedure for the determination of trace tin is presented. The method is based on adsorptive accumulation of the Sn(IV)-3,4-dihydroxybenzoic acid (DHBA) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species. The reduction current is enhanced catalytically by vanadium(IV). The optimal experimental conditions include the use of 0.10 M formate buffer (pH 3.1), 8.0 × 10−5 M DHBA, 3.0 × 10−3 M V(IV), an accumulation potential of −0.30 V (versus SCE), an accumulation time of 60 s, a scan rate of 200 mV/s and a second-order derivative linear scan mode. The peak current is proportional to the concentration of tin over the range of 0.01-40 μg/L, and the detection limit is 0.005 μg/L for a 60 s adsorption time. The proposed method was applied to the determination of tin in canned food, human hair and waste water samples with satisfactory results.