Determination of inorganic ionic mercury down to 5×10⁻¹⁴ mol l⁻¹ by differential-pulse anodic stripping voltammetry

Abstract

A new method is described for the reliable and ultrasensitive determination of inorganic ionic mercury, using differential-pulse anodic stripping voltammetry on a glassy carbon electrode. It has been possible to determine mercury down to a concentration of 5×10⁻¹⁴ mol l^-1 (the lowest detection limit ever reported for a voltammetric method). This success was achieved by using a thiocyanate electrolyte and relatively long deposition times. The mercury ions are stabilized in the solution by the formation of strong thiocyanate complexes. This leads to a highly reproducible cathodic plating and anodic dissolution of mercury. A speciation analysis allowing to distinguish between dissolved atomic and ionic mercury in water is possible.