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A novel electrochemical sensor for trace (μg/L) Uranium, based on adsorptive stripping potentiometry, is described. The sensor operation relies on the adsorptive accumulation of the uranium-cupferron complex onto a mercury-coated screen-printed carbon electrode. The disposable nature of these electrodes makes them very attractive for on-site characterization of nuclear energy sites. Various variables affecting the potentiometric stripping response were characterized and optimized to yield low-detection limit (e.g., 0.5 μg/L following a 5 minute adsorption) and good precision (relative standard deviation (RSD) = 1.4% for n = 15, 25 μg/L uranium). Convenient measurements can be carried out in nondeaerated and quiescent solutions. Applicability to the quantitation of uranium in groundwater samples is demonstrated.

A very sensitive stripping procedure for trace measurements of bismuth, based on the adsorptive accumulation of the bismuth-cupferron complex onto the mercury working electrode, is described. The optimized conditions include a sulfuric acid (5 × 10−4 M) medium, containing 2.5 × 10−5 M cupferron, and an accumulation potential of −0.10 V. Both voltammetric and potentiometric stripping modes can be employed to probe the reduction of the accumulated complex. The limit of detection after 10 minutes preconcentration is 6 ng L−1 (3 × 10−11 M), and the relative standard deviation at the 2 × 10−8 M level is 1.6%. Most cations, including antimony, do not interfere in the determination of bismuth. Simultaneous measurements of bismuth, titanium, and uranium are illustrated.

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 (subnanomolar) 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 quantitation of uranium in ground water samples is demonstrated.