engleski

What makes the anodic stripping voltammetry of mercury at a trace level possible?

For thermodynamic reasons it is impossible to describe the anodic stripping voltammetry (ASV) of mercury at concentrations below 10-7 mol/L as involving a simple deposition and dissolution of metallic mercury. That follows from the finite solubility of elemental mercury in water at ambient temperature. Instead, it is a more or less strong adsorption of mercury atoms on the electrode surface which makes ASV possible. At these low concentrations, the atomic mercury in the solution can no longer be neglected. A theoretical description for staircase cyclic voltammetry of the reaction (Hg)0,ads = (Hg)0,aq = (Hg)2+,aq + 2e- has been developed and it is discussed with respect to the ASV of mercury. The adsorption of atomic mercury is considered for the case of different electrode materials and adsorption constants have been estimated from underpotential deposition peaks. The distribution of the following mercury species is given for different electrode potentials and total mercury concentrations: (Hg2)2+, (Hg)2+, (Hg)0,aq., (Hg)0,ads. and (Hg)0,met.

mercury; analysis; adsorptive accumulation; anodic stripping voltammetry

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