Differential pulse cathodic stripping voltammetric determination of uranium with arsenazo-III at the hanging mercury dropping electrode

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.