Adsorptive stripping voltammetric measurements of trace uranium at the bismuth film electrode

Bismuth-coated carbon-fiber electrodes have been successfully applied for adsorptive stripping voltammetric measurements of trace uranium in the presence of cupferron. The new protocol is based on the accumulation of the uranium-cupferron complex at a preplated bismuth film electrode held at -0.30 V (versus Ag/AgCl), followed by a negatively-sweeping square-wave voltammetric waveform. Factors influencing the stripping performance, including the film preparation, solution pH, cupferron concentration, adsorption potential and time have been optimized. The resulting performance compares well with that observed for analogous measurements at mercury film electrodes. A detection limit of 0.3 μg/L is obtained in connection to a 10 min adsorption time. The response is linear up to 50 μg/L and the relative standard deviation at 50 μg/L uranium is 3.8% (n = 15; 2 min adsorption). Potential interferences are examined. Applicability to seawater samples is demonstrated. The attractive behavior of the new 'mercury-free' uranium sensor holds great promise for on-site environmental and industrial monitoring of uranium.