Electrochemical determination of thorium in aqueous medium

Thorium is radiologically and biologically toxic element and the exposure poses threats to human health. Inhalation of Th dust may cause lung, pancreas and bone cancer. Thus, it is of great importance to develop a sensitive method for trace level determination of Th to limit its exposure to aquatic and biological environments as well as to check the suitability of nuclear effluents to fall below the disposal limits. The most stable oxidation state of Th is Th⁴⁺ and electrochemical reduction of Th⁴⁺ in aqueous medium is extremely difficult. Therefore, it is very difficult to quantify Th in aqueous medium by voltammetry. The decrease in the peak-current density of UO₂²⁺ to UO₂ reduction on PEDOT-PSS/GC (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)- coated glassy carbon electrode) electrodes is selective for the presence of Th⁴⁺ and the decreasing trend of peak-current density may be correlated with Th concentration. The decrease in the peak-current of U(VI) to U(IV) reduction provides an indirect route for Th determination in aqueous medium which is otherwise very difficult by electrochemistry. The present study will widen the roots of voltammetry for determination of low level of Th in natural water. But the present approach needed the presence of U(VI) in solution for determination of Th(IV). (author)