Determination of sulfur contents of SO32-, S2O32- and S2- based on the electrocatalytic interaction with homogeneous mediator tris(2,2 '-bipyridyl)Ru(II)

摘要

A sensitive voltammetric method has been developed for the determination of total or single species of sulfur anions containing sulfide, sulfite and) thiosulfate. The method is based on the catalytic effect of tris(2,2'-bipyridyl)Rutheniuin(II) (Ru(bpy)(2)(+2)) as a homogeneous mediator on the oxidation of those anions at the surface of a glassy carbon electrode. A reversible redox couple of Ru(II)/Ru(III) were observed as a solute in aqueous solution. Cyclic voltammetry study showed that the catalytic current of the system depends on the concentration of the anions. Optimum pH values for voltammetric determination of sulfite, thiosulfate and sulfide has been found to be 5.6, 10.0 and 10.0, respectively. Under the optimized conditions the calibration curves been obtained linear in the concentration ranges of 0.8-500.0, 0.4-1000.0 and 0.5-5000.0 mu mol L-1 of SO32-, S2O32- and S2- respectively. The limits have been calculated to be 0.40, 0.17 and 0.33 mu mol L-1 for SO32-, S2O32- and S2-, respectively. The diffusion coefficients of sulfite and thiosulfate have been estimated using chronoamperometry. The chronoamperometric method also has been used to determine the catalytic rate constant for catalytic reaction of the Ru(bpy)(2)(+2) with sul fite and thiosul fate. Finally the proposed method has been used for the deten-nination of total sulfur contents in real samples of water and wastewater. Moreover the sulfite content in sugar and sulfur dioxide in air has been determined with satisfactory results. (C) 2008 Elsevier B.V. All fights reserved.