Differential pulse voltammetric determination of U(VI)-Tc(VII) and U(VI)-Cr(VI) in alkaline solutions

Differential pulse voltammetric (DPV) technique has been developed for the simultaneous determination of the elements in Tc(VII)-U(VI) and U(VI)-Cr(VI) mixtures in alkaline solutions. The method gave a precision of about 14% to 2% in the range of 1 x 10-7-1 x 10-4 for Cr(VI) and Tc(VII) and 1 x 10-6-1 x 10-4 for U(VI). The detection limits are 8 x 10-8 mol l-1 for Tc(VII) and 3 x 10-7 mol l-1 for Cr(VI), and 8 x 10-7 for U(VI). It has been established that Tc(VII) could be determined in the presence of about 350 excess fold U(VI). The reduction of Tc(VII) with hydrazine has been suggested to eliminate the effect of Tc(VII) ions on the U(VI) determination. U(VI) has been determined in the presence of Cr(VI) up to molar concentration ratio U(VI)/Cr(VI) = 1 : 1, while Cr(VI) could be determined in the presence of U(VI) in the solutions with up to molar concentration ratio Cr(VI)/U(VI) = 1 : 15. The reliability of the determination of the elements of Tc(VII)-U(VI) and U(VI)-Cr(VI) mixtures in alkaline solution has been tested by a standard addition method. (orig.)