ADSORPTIVE STRIPPING VOLTAMMETRIC MEASUREMENTS OF TRACE AMOUNTS OF PLATINUM(II) AND RUTHENIUM(III) IN THE PRESENCE OF 1-(2-PYRIDYLAZO)-2-NAPHTHOL

An extremely sensitive stripping voltammetric procedure for low level measurements of platinum (II, IV) or ruthenium (III, IV) is reported. The method is based on the interfacial accumulation of the platinum (I I) or ruthenium (III)-1-(2-pyridylazo)-2-naphthol complex on the surfa ce of a hanging mercury drop electrode, followed by the reduction of t he adsorbed complex during the cathodic scan. The peak potential was f ound to be -0.8 V vs. Ag/AgCl electrode and the reduction current of t he adsorbed complex ions of platinum (II) or ruthenium (III) was measu red by differential pulse cathodic stripping voltammetry. The optimum experimental conditions were: 1.5 x 10(-7) mol/l of 1-(2-pyridylazo)-2 -naphthol solution of pH 9.3, preconcentration potential of -0.2 V, ac cumulation time of 3 min and pulse amplitude of 50 mV with 4 mV s-1 sc an rate in the presence of ethanol-water (30% v/v) - sodium sulphate ( 0.5 mol/l). Linear response up to 6.4 x 10(-8) and 5.1 x 10(-8) mol/l and a relative standard deviation (at 1.2 x 10(-8) mol/l) of 2.4 and 1 .6% (n = 5) for platinum (II) and ruthenium (III) respectively were ob tained. The detection limits of platinum and ruthenium were 3.2 x 10(- 10) and 4.1 x 10(-10) mol/l, respectively. The electronic spectra of t he Pt(II) - PAN and Ru(III) - PAN complexes were measured at pH 9.3 an d the stoichiometric ratios of the complexes formed were obtained by t he molar ratio method. The effects of some interfering ions on the pro posed procedure were critically investigated. The method was found sui table for the sub-microdetermination of ruthenium (IV) and platinum (I V) after their reduction to ruthenium (III) and platinum (II) with sul phur dioxide in acid media. The applicability of the method for the an alysis of binary mixtures of ruthenium (III) and (IV) or platinum (II) and (IV) has also been carried out successfully. The method is simple , rapid, precise, and promising for the determination of the tested me tal ions at micromolar concentration level.