Increased sensitivity of anodic stripping voltammetry at the hanging mercury drop electrode by ultracathodic deposition

An improved approach to the anodic stripping voltammetric (ASV) determination of heavy metals, using the hanging mercury drop electrode (HMDE), is reported. It was discovered that using very cathodic accumulation potentials, at which the solvent reduction occurs (overpotential deposition), the voltammetric signals of zinc(II), cadmium(II), lead(II) and copper(II) increase. When compared with the classical methodology a 5 to 10-fold signal increase is obtained. This effect is likely due to both mercury drop oscillation at such cathodic potentials and added local convection at the mercury drop surface caused by the evolution of hydrogen bubbles.

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► At very cathodic accumulation potentials (overpotential deposition) the voltammetric signals of Zn2+, Cd2+, Pb2+ and Cu2+ increase.
► 5 to 10-fold signal increase is obtained.
► This effect is likely due to mercury drop oscillation at such cathodic potentials.
► This effect is also likely due to added local convection at the mercury drop surface caused by the evolution of hydrogen bubbles.