Adsorptive stripping square-wave voltammetry of Bi(III) in chloride media. Influence of triton X-100

Abstract

Chloride induced adsorption of bismuth(III) ions in submicromolar concentrations is analysed by square-wave voltammetry in the cathodic stripping mode. The application of this method for the qualitative metal speciation at interfaces is demonstrated. By the separation of diffusive and adsorptive current components, the adsorption constant of the surface active complex BiCl 4 − is estimated as β 4Γ BiCl 4,max ≈ 8 × 10 −3 cm. The lowest concentration of Bi(III) ions detectable by adsorptive stripping square-wave voltammetry is 10 −7. Under the influence of Triton X-100, the neutral complex BiCl 3 is adsorbed predominantly at a mercury electrode surface, instead of BiCl 4 −. This suggests that the variation of the potential of zero charge may cause a change of the charge of surface active species, i.e. the number of ligand ions in the complex which adsorbs at a certain potential depends on the charge of the electrode surface.