New voltammetric procedure for the simultaneous determination of copper and mercury in environmental samples

Abstract

A new voltammetric procedure for the simultaneous determination of Cu and Hg down to the ng/l-range in environmental samples is described. Differential pulse anodic stripping voltammetry (DPASV) at a gold electrode is applied. There are two versions. For Hg-levels typically below 100 ng/l in presence of substantially higher Cu-concentrations (300 ng/l or more), e.g. in sea water, Hg has to be determined by the subtractive mode of DPASV at a twin gold electrode and programmed polarisation has to be applied during the cathodic deposition stage, while the usually higher Cu-levels can be determined by common DPASV at a normal gold electrode. For Hglevels above 100 ng/l the determination of Hg and Cu can be performed in the same run by common DPASV at a normal gold electrode. The application of the gold electrode always requires medium exchange to 0.1 M HClO4 plus 2.5×10−3 M HCl subsequent to the cathodic accumulation stage before stripping. The method has been successfully applied to natural waters and wine. The necessary sample pretreatment remains simple and consists just in UV-irradiation to release the trace metal amount bound to dissolved organic matter, which is performed with samples from natural waters after prior 0.45 μ-filtration to separate from suspended particulate material.