Differential pulse voltammetric determination of tin in the presence of noble metals.

A voltammetric method for the determination of tin is proposed to minimise interferences from noble metals that are commonly encountered with other analytical techniques. Strong distortions of voltammetric peaks are observed in the presence of platinum. On the basis of a full investigation, the formation of an intermediate Sn(II)-Pt mixed chloro-complex at the electrode surface is identified as being responsible for the platinum interference, as it competes with the normal Sn(IV)-->Sn(0)Hg reduction. The use of a higher scan rate prevents the relatively low reaction kinetics and thus gets rid of this interference. No problems are encountered with other noble metals such as Pd, Ir, Re, Rh and Ru when using the modified method, although a baseline subtraction is necessary for the latter one. The proposed method is validated with real Pt-Sn catalysts.