Selective determination of trace uranium by stripping voltammetry following adsorptive accumulation of the uranium-cupferron complex

Trace levels of uranium can be determined by stripping voltammetry after controlled adsorptive preconcentration of the uranium-cupferron complex on the mercury electrode. The resulting procedure greatly improves the selectivity over previously reported adsorptive stripping schemes, while offering similar sub-nanomolar detection limits. In addition, the use of cupferron eliminates interference from dissolved oxygen, extends the linear range, and offers a wider useful pH range. Both potentiometric and voltammetric stripping approaches are used to follow the reduction of the adsorbed complex. The effect of various experimental parameters is explored. Adaptation to flow-through cells permits on-line monitoring of trace levels of uranium at rates of 30-60 samples h-1, with relative standard deviations of 2.7-4.1%. Applicability to the quantisation of uranium in ground water samples is demonstrated. (author). 10 refs.; 7 figs