A new sensitive method for the determination of trace mercury by differential pulse polarography: Application to raw salt sample

A new indirect differential pulse polarographic (DPP) method is established for the trace determination of mercury(II). Because of its toxic effects on human health, trace determination of mercury is very important. An indirect method had to be used since no polarographic peak is observed in its direct determination. According to the standard potentials, the reaction between Sn(II) and Hg(II) was found suitable. The peak of Sn(II) at about ?0.40 V is sharp, high and very reproducible, which enables the determination of low concentrations of Hg(II). For this purpose, to a known amount of Sn(II) present in the polarographic cell (acetic acid, HAc, pH 1–2), the unknown Hg(II) sample is added and the quantitative reaction takes place directly in the cell. The Hg(II) concentration is calculated simply from the decrease of the Sn(II) peak. The limit of detection (LOD) was found as 2 × 10^?7 M for S/N = 3. Interferences of some common cations, such as Fe, Cd, Cu, Zn and Pb and anions have been investigated. Only Pb had an overlapping peak with Sn(II). This peak overlap was eliminated simply by working at pH 2 (HAc electrolyte), because of the shift of the Pb peak in the Ac complex to ?0.7 V. This method was successfully applied to synthetic samples and raw salt sample taken from a salt lake in Turkey.