Trace determination of chromium by square-wave adsorptive stripping voltammetry on bismuth film electrodes

This works reports the use of adsorptive stripping voltammetry (AdSV) for the trace determination of chromium on a rotating-disk bismuth-film electrode (BFE). During the reductive accumulation step, all the chromium species in the sample were reduced to Cr(III) which was complexed with cupferron and the complex was accumulated by adsorption on the surface of a preplated BFE. The stripping step was carried out by using a square-wave (SW) potential-time voltammetric signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements in the presence of dissolved oxygen. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3sigma limit of detection for chromium was 100 ng L-1 (for 120 s of preconcentration) and the relative standard deviation was 3.6% at the 2 mug L-1 level (n = 8). Finally, the method was applied to the determination of chromium in real samples with satisfactory results.