Phase-Selective Fundamental and Second Harmonic Alternating Current Voltammetry of Bismuth(III) and Lead(II) at a Continuously Mercury-Coated Rotating Platinum Disk Electrode

A continuously mercury-coated rotating platinum disk electrode was used with alternating current (ac) and direct current (dc) voltammetry to explore its effectiveness for low concentration analysis. Well-defined fundamental and second harmonic alternating current voltamograms were obtained in 2.5 μM BI(III) and Pb(II) in the presence of 100-fold excess of Hg₂²⁺. The height of the fundamental and second harmonic alternating current voltammogram of BI(III) was proportional to its concentration in the range 10 to 0.5 μM. Double layer charging effects Interfered at lower concentrations. Direct current voltammetry of BI(III) had a sensitivity limit of 0.25 μM. Fundamental and second harmonic ac voltammetry of Pb(II) had a sensitivity limit of 0.1 μM. as compared to 0.5 μM using the dc technique. Second harmonic ac voltammetry has a slightly higher sensitivity than fundamental ac voltammetry In the phase-selective mode.