Determination of trace thorium using catalytic-adsorptive stripping voltammetry of the thorium-cupferron complex

A sensitive stripping voltammetric procedure for trace measurement of thorium, based on the catalytic-adsorptive peak of the thorium—cupferron complex, is reported. Optimal experimental conditions include the use of 1mM BES buffer solution (pH 5.5), containing 20μM cupferron, an accumulation potential of −0.80 V (vs. Ag/AgCl), and a differential pulse potential scan. The resulting stripping procedure offers improved sensitivity over a previous stripping scheme for thorium. The limit of detection after 5 min preconcentration is 50 ng/l. (2 × 10−10M), the response is linear up to 8 × 10−8M, and the relative standard deviation at the 2.1 × 10−8M level is 4.4%. Possible interferences are evaluated.