Voltammetric trace determination of uranium and other transition metals in rock phosphate samples

Abstract

Convenient and accurate direct current and differential-pulse polarographic and differential-pulse anodic stripping voltammetric procedures were developed for the simultaneous trace determination of transition metals and uranium in rock phosphate samples. Water leaching followed by acid leaching of the finely powdered rock phosphate sample was used to prepare the analyte for analysis. The results indicated the presence of Cu, Cr, Tl, Te, Zn, Fe and U. Differential complexation with nitrilotriacetic acid was applied for better resolution of the polarographic waves. Uranium gave a well defined polarographic wave with E_½=–0.82 V versus SCE. The method of standard additions was used for quantitative analysis. The voltammetric results indicated that on average the rock phosphate sample contained Cu 215, Cr 363, Tl 80, Te 100, Zn 180, Fe 1750 and U 102.0 mg kg^–1. The proposed voltammetric methods are capable of giving both qualitative and quantitative analyses of rock phosphate for the reported metals in one run. The accuracy of the methods was verified by comparing the observed results with those observed using atomic absorption and X-ray fluorescence spectrometric techniques.