Adsorptive Voltammetric Study of Thorium?Alizarin Complexon Complex at a Carbon Paste Electrode

Abstract

A new sensitive adsorptive voltammetric procedure is described for trace measurement of thorium. It is based on the cathodic stripping peak of the thorium–alizarin complexon (ALC) complex at a carbon paste electrode (CPE). The complex of Th(IV) with alizarin is adsorbed at a CPE in a mixed buffer solution (pH 5.0) which consists of 0.1 mol·L−1 sodium acetate and 0.04 mol·L−1 potassium biphthalate, yielding a sensitive cathodic voltammetric peak corresponding to the reduction of alizarin in the complex at −0.57 V (vs. SCE). The second-order derivative peak current of the complex is linearly dependent upon the concentration of Th(IV) over the range of 3.0×10−9 ∼8.0×10−7 mol·L−1. The detection limit is 1.0×10−9 mol·L−1 for 180 s accumulation. The molar ratio of each component in the complex was estimated as nTh(IV):nALC=1:1 by a continuous variation method. The electrode processes of the Th(IV)–alizarin complex at a CPE were investigated. The procedure was successfully applied to the trace determination of thorium in ore and clay samples.