Abstract

An accurate, inexpensive and less laborious controlled adsorptive accumulation of uranium(VI)-arsenazo-III on a hanging mercury drop electrode (HMDE) has been developed for uranium(VI) determination. The method is based upon the collection of uranium(VI)-arsenazo-III complex at pH 5–6 at the HMDE and subsequent direct stripping measurement of the element in the nanomolar concentration level. The cathodic peak current (i_p,c) of the adsorbed complex ions of uranium(VI) was measured at −0.35 V vs. Ag/AgCl reference electrode by differential pulse cathodic stripping voltammetry (DP-CSV), proceeded by an accumulation period of 150s2.5 in Britton–Robinson buffer of pH 5. The plot of the resulting i_p,c vs. uranium(VI) concentration was linear in the range 2.1×10⁻⁹ to 9.60×10⁻⁷ mol L⁻¹ uranium(VI) and tended to level off at above 9.6×10⁻⁷ mol L⁻¹. The limits of detection and quantification of uranium(VI) were found to be 4.7×10⁻¹⁰ and 1.5×10⁻⁹ mol L⁻¹, respectively. A relative standard deviation of ±2.39% (n=5) at 8.5×10⁻⁷ mol L⁻¹ uranium(VI) was obtained. The method was validated by comparing the results with that obtained by ICP–MS method with RSD less than ±3.3%. The method was applied successfully for the analysis of uranium in certified reference material (IAEA soil-7), and in phosphate fertilizers.