Determination of Chromium (VI) and (III) by Adsorptive Stripping Voltammetry with Pyrocatechol Violet

A sensitive voltammetric stripping procedure for trace measurement of chromium (VI) and (III) in aqueous samples is reported. The method is based on the preconcentration of a chromium(VI)–pyrocatechol violet complex at HMDE from an acetate buffered solution. The adsorbed complex is then reduced, producing a well defined peak at a potential of −0.73 V. Total chromium was determined after oxidation of chromium (III) to chromium (VI) by UV irradiation in an oxygen-saturated solution. Therefore, total chromium was also determined as chromium (VI). Optimal conditions for the determination of chromium (VI) and total chromium at the nmol L−1level have been established. A preconcentration time of 1 min provided a detection limit of 3 nmol L−1.