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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.

An automated system for on-line monitoring of trace uranium, based on a flow-through adsorptive stripping operation, is described. The on-line formation of the uranium-oxine complex is followed by its adsorptive accumulation and voltammetric quantitation at the downstream working electrode. About 10–60 runs can be made every hour with high reproducibility (RSD of 3–5%) and a detection limit of 0.7 μg/L. The dependence of the peak current on different experimental variables is reported. The sequence of events involved in the adsorptive stripping voltammetric cycle is controlled by a computer. Analogous on-line monitoring of chromium (VI) are also reported with 36 runs/h (2.1% RSD), and detection limit of 1.5 μg/L. The system holds great promise for field-based operation.