On-line determination of vanadium by adsorptive stripping voltammetry

An on-line electrochemical stripping procedure for trace determination of vanadium was developed combining the advantages of adsorptive stripping voltammetry with flow injection analysis. The vanadium formed a complex with cupferron in an acetate buffered solution which adsorbed onto the mercury film electrode. An amplification of the stripping current was attained by the catalytic reduction of the adsorbed complex in the presence of bromate. The complex was deposited at + 200 mV (vs. AgAgCl) then stripped using a differential pulse waveform with a scan rate of 10 mV s−1, the reduction peak occurring at +100 mV. Under optimized conditions a limit of detection of 8 ng I−1 and mid-range standard deviation of 2–3% were obtained. The response was linear up to 3.5 μg l−1 with a sensitivity of 0.1 mA l μg−1. Sample matrixes containing high salt concentrations had to be measured by anodic stripping, depositing the complex cathodically at 0.0 V and resuming with a scan to +150 mV to prevent calomel formation.