Controlled-potential-coulometric determination of uranium at a platinum electrode

A controlled-potential-coulometric method has been developed for determining uranium at a solid electrode which features high specificity and a precision of 0.1% relative standard deviation at the 5 mg uranium level. Uranium and added iron, necessary for the electrolytic oxidation of uranium, are reduced to U(IV) and Fe(II) with excess Cr(II). At a sequence of controlled potentials, the excess Cr(II) is oxidized to Cr(III), Fe(II) and U(IV) are oxidized to Fe(III) and U(VI), then the Fe(III) is reduced to Fe(II). The difference in the measured number of coulombs for the oxidation of Fe(II) and U(IV) and for the reduction of Fe(III) to Fe(II) is proportional to the quantity of uranium