Voltammetric Determination of Bismuth in Water and Nickel Metal Samples with a Sodium Montmorillonite (SWy-2) Modified Carbon Paste Electrode

Abstract.

A simple and reliable electrochemical method for the determination of bismuth in water and nickel metal samples using a sodium montmorillonite (SWy-2) modified carbon paste electrode was described. Due to its strong cation-exchange ability and adsorptive characteristics, SWy-2 significantly enhances the sensitivity of determination for Bi³⁺. Bi³⁺ is firstly preconcentrated and then reduced on the modified electrode surface at −0.50 V. After that, reduced bismuth is stripped from the electrode surface during the positive potential sweep of −0.50 V to 0.20 V, and a well-defined stripping peak at −0.12 V appears. The stripping peak current is proportional to the concentration of Bi³⁺ from 4 × 10⁻⁹ mol L⁻¹ to 1 × 10⁻⁶ mol L⁻¹. The detection limit (signal-to-noise=3) is 1 × 10⁻¹⁰ mol L⁻¹ after 5 min. accumulation. The proposed method was successfully applied to the determination of bismuth in water and nickel metal samples.