Determination of Platinum and Rhodium by Stripping Voltammetry

Abstract

We studied the determination of platinum(IV) and rhodium(III) without separating them in solution by stripping voltammetry using the peak of the selective electrooxidation of lead from a lead–platinum–rhodium electrolytic deposit at a potential of –0.3 V. Lead, platinum, and rhodium were electrodeposited in situ on a graphite electrode surface from 1 M HCl. In an electrolytic deposit, platinum and rhodium did not form solid solutions but formed intermetallic compounds (IMCs) with lead. The selective electrooxidation of lead from the PtPb IMC and rhodium from the Pb₂Rh IMC occurred at –0.3 V. Platinum(IV) and rhodium(III) can be determined without separation using the standard addition method. The lower limit of determination for platinum(IV) by the peak of the selective electrooxidation of lead from the PbPt IMC is 0.86 mg/L. The lower limit of determination for rhodium(III) by the peak of the selective electrooxidation of lead from the Pb₂Rh IMC is 0.0046 mg/L.