Electrochemical Determination of Methyltin Compounds

Abstract

The electrochemical behaviour of monomethyltin, dimethyltin and trimethyltin compounds in 20% (V/V) methanol/water solution, 0.05 mol/L in tetraethylammonium perchlorate at pH 2.5, has been investigated by differential pulse polarography and differential pulse anodic stripping voltammetry. In differential pulse polarography, dimethyltin and trimethyltin gave one reversible wave with peak potentials at −0.70 V and −1.07 V, respectively. Detection limits were 6.6 × 10−7 mol/L for dimethyltin and 4.1 × 10−6 mol/L for trimethyltin. The electrochemistry of monomethyltin was found to be more complex. By differential pulse anodic stripping voltammetry, monomethyltin, dimethyltin and trimethyltin produced distinct stripping peaks (−0.39 V, −0.75 V and −1.14 V, respectively), which allow to determine these compounds at trace levels. Using this new method, detection limits were: 1.2 × 10−7 mol/L for monomethyltin, 1.7 × 10−7 mol/L for dimethyltin and 1.4 × 10−6 mol/ L for trimethyltin. For monomethyltin, a second peak (Ep = −0.60 V), less sensitive (detection limit of 2.5 × 10−6 mol/L), was also observed at concentrations above 4.2 × 10−7 mol/L.