Simultaneous measurements of trace chromium and uranium using mixed ligand adsorptive stripping analysis

Simultaneous adsorptive–stripping voltammetric measurements of trace chromium and uranium, based on the use of a mixed-ligand solution, are described. Both metals can be readily determined in a single scan in the presence of propyl gallate (PG) and diethylenetriaminepentaacetic acid (DTPA). Variables affecting the response, including the concentration of both ligands, pH, adsorption potential or time, are assessed and optimized. The performance is not compromised (in comparison to the individual ligand protocols), with detection limits of 15(Cr) and 200 (U) ng l−1 (5 min adsorption), good reproducibility (RSDs of 5.1–6.0%; n=15), and suitable linear ranges (up to 3- and 80 μg l−1 Cr and U (one min adsorption)). The procedure offers high selectivity, with the presence of DTPA masking some metal ions that commonly affect the single-ligand uranium-PG procedure. Applicability to the simultaneous measurements of uranium and chromium in a groundwater sample is illustrated, and prospects for on-site environmental analysis are discussed.