Catalytic-adsorptive stripping voltammetric determination of ultra-trace iridium(III). Application to fresh- and sea-water

An extremely sensitive stripping voltammetric procedure for ultra-trace determination of iridium(III) is reported. The method is based on the interfacial accumulation of the iridium(III)-CTAB complex onto the glassy carbon electrode, followed by the catalytic reduction of the adsorbed complex in the presence of bromate. 0.3 mol L-1 acetate buffer pH 4.7 + 6.9x10-2 mol L-1 NaBrO3 + 2.7x10-5 mol L-1 cetyltrimethylammonium bromide (CTAB) + 0.2 mol L-1 KCl was employed as the supporting electrolyte. The analytical procedure was verified by the analysis of the standard reference materials: Sea Water BCR-CRM 403 and Fresh Water NIST-SRM 1643d. For all the elements, the accuracy, expressed as relative error e %, was satisfactory, being lower than 6%, while precision as repeatability, expressed as relative standard deviation sr %, was generally lower than 5%. Once set up on the standard reference materials, the analytical procedure was transferred and applied to superficial water sampled in proximity to superhighway and in the Po river mouth area.