Coulometric titration study of the redox behavior and precise determination of hexachloroiridate(IV) ion and its monoaquo-chloro complex with electrogenerated bi-intermediates Original Research Article

The redox behavior of IrCl62− and Ir(H2O)Cl5− ions is investigated. Based on the reversibility of the IrCl62−/IrCl63− couple, the reusable reduction and oxidation titrations of iridium(IV,III) can be realized in the same HCl solution with electrogenerated CuCln(n−1)− and Cl2 as bi-intermediates, using biamperometric end point detection. The first reduction titration among the determinations of IrCl62−can be used for precise coulometric analysis. For the determinations of 0.5–5.0 mg of iridium, the relative average errors of the results are ≤±0.06%, and the relative standard deviation (n=5–6) is 0.18–0.04%. The method is applied to the determination of iridium in the metal and its compounds.