On-line determination of chromium by adsorptive cathodic stripping voltammetry

To date, the application of adsorptive cathodic stripping voltammetry (ACSV) to chromium determination has commonly involved static systems in a batch approach. The use of ACSV in a dynamic system is reported here. The on-line system is described and optimization of the experimental parameters discussed. The metal ions were complexed with diethylenetriaminepentaacetic acid and the complex was absorbed, from the flowing stream, onto the surface of a glassy carbon electrode, which was pre-plated, on-line, with mercury. Reduction of the complex, in the presence of nitrate, produced a catalytically enhanced reduction current at –1.27 V (Ag–AgCl). The working limit of quantification was 0.2 ng ml–1 of CrVI(for 60 s deposition), with a relative standard deviation of typically 2–3% at the 2 ng ml–1 level and a determination time of less than 3 min sample–1.