Determination of cadmium and lead at the «Ultra Trace» graphite electrode by anodic stripping voltammetry

Cadmium and lead can be determined in a range from 0.1 to 500 µg/L by means of anodic stripping voltammetry (ASV) using the «Ultra Trace» graphite electrode. The method is based on a preelectrolysis of the sample solution containing a small amount of mercury ions, followed by the stripping step of the metals from the electrode surface in the DP mode. Organic compounds interfere with the determination and have to be removed, for example, by UV digestion. Traces of Pt and other Pt group metals lead to hydrogen generation on the electrode surface and makes the determination of Cd and Pb in acidic media impossible. TI and In could interfere with Cd and Pb potentials. For this determination the 746 Trace Analyzer was used. This method has been developed for environmental matrices (drinking, sea, river and wastewater). Lead and cadmium can be concentrated on the graphite electrode simultaneously with the mercury (Hg film electrode in situ). Currents measured in the DP mode are proportional to the metal ion concentrations in the solution. The determination limit for both metals is 0.05 ppb.