This paper describes a procedure for the determination of thallium by differential pulse anodic stripping voltammetry (DPASV) using a mercury film deposited on glassy carbon as the working electrode. The procedure has been optimized using experimental design methodology. The following results were obtained: deposition potential: -1000 mV, deposition time: 4 min, speed of the rotating disc electrode: 1000 rpm, pulse amplitude 80 mV. The response of the electrode towards thallium ions was then verified by establishing the calibration curve, which showed a good correlation coefficient of 0.9973 and the error between 5 successive determinations did not exceed 1.25%. The calculated limit of detection (LOD) is equal to 2.2 10-8 mol.L-1. A certified standard of thallium at 1 mg.L-1 is determined by the standard addition method and the recovery rate obtained is 99.14%. The remarkable electroanalytical performances of the glassy carbon/mercury thin film electrode make it amenable to employ it successfully as an electrochemical sensor for the determination of traces of thallium in environmental samples. Measurements carried out on the waters from wells and boreholes in the village of Yamtenga reveal thallium levels above the standard for some sources of water. These waters are therefore not recommended for use as drinking as drinking water.

Thallium, Mercury Film, Differential Pulse Anodic Stripping Voltammetry, Optimization