Determination of trace amounts of thorium by electroanalytical techniques

Trace amounts of thorium have been determined in the presence of uranyl nitrate and ammonium diuranate (as interferents) by cyclic voltammetry, differential-pulse polarography, differential-pulse voltammetry, square-wave voltammetry and anodic-stripping voltammetry. The determination is based on the substitution of thorium for copper, lead and cadmium in their EDTA complexes and voltammetric measurement of the displaced metal ion. The detection limits ranged between 2 x 10-7 and 1 x 10-6M (r.s.d. 2-7%) for solutions free from the uranium compounds, and between 8 x 10-7 and 5 x 10-6M (r.s.d. 3.5%) in the presence of the uranium compounds at concentrations up to about 1000 times that of thorium. The detection limits depend on both the particular technique and the EDTA complex employed. Anodic-stripping voltammetry gave detection limits of 8 x 10-8 and 10-7M in the absence and presence of uranium respectively. (author)