Simultaneous determination of osmium, ruthenium, copper and lead by electrocatalytic voltammetry. Application to superficial waters

The present work describes and discusses the possible problems of interference that can occur when Cu(II) and Pb(II) are present during simultaneous voltammetric determination of Os(VIII) and Ru(III) at ultra-trace concentrations. The method is based on the voltammetric catalytic current of the Os(VIII) and Ru(III)-bromate systems and uses a conventional three-electrode cell and 0.5 mol L-1 acetate buffer pH 4.9 + 5.7x10-2 mol L-1 NaBrO3 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, accuracy - expressed as relative error e % - was satisfactory (lower than 6%) while precision as repeatability - expressed as relative standard deviation sr % - was generally lower than 5%. Once set up using the standard reference materials, the analytical procedure was transferred and applied to superficial water samples drawn in proximity to a superhighway and in the area of the mouth of the Po River.