Electroreduction of uranium (VI) at a platinum electrode and its analytical applications

Under normal conditions, the reduction of uranium(VI) at a platinum electrode, in acid solutions, is masked by the reduction of the hydrogen ion. If the working electrode is subjected to hydrogen evolution (at a current density of about 7 A cm 2 for 90–120 min) the H ads on the platinum surface, acting as a bridge in the electron transfer, shifts the reduction wave of uranium(VI), in 1 M sulphuric acid solutions, to potentials ( E 1 2 ≅ − 0.03 V) less negative than that of the hydrogen discharge (about −0.25 V). The wave corresponding to the reduction of uranium(VI) to uranium(IV) is well shaped, diffusion-controlled, and can be used for the determination of uranium down to 2 × 10 −5 M or 3 × 10 −6 M if a rotating electrode is used. Interferences arise from those ions with similar E 1 2 [i.e., Cu(II) and Bi(III)], or from those such as permanganate and dichromate, which oxidize the H ads on the platinum electrode. Because of the time required for the electrode pretreatment, the determination is time-consuming but in some respects it appears a useful improvement over the DME.