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

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 –0.50V. After that, reduced bismuth is stripped from the electrode surface during the positive potential sweep of –0.50V to 0.20V, and a well-defined stripping peak at –0.12V appears. The stripping peak current is proportional to the concentration of Bi³⁺ from 4×10^–9molL^–1 to 1×10^–6molL^–1. The detection limit (signal-to-noise=3) is 1×10^–10molL^–1 after 5min. accumulation. The proposed method was successfully applied to the determination of bismuth in water and nickel metal samples.