DETERMINATION OF VANADIUM IN SEA-WATER BY CATALYTIC ADSORPTIVE CATHODIC STRIPPING VOLTAMMETRY

The sensitivity of adsorptive cathodic stripping voltammetry (CSV) to vanadium is much improved by inclusion of a catalytic effect. The deposition step is based on the adsorptive accumulation of complex species with catechol on a hanging mercury drop electrode. The reduction current of the adsorbed complex is catalytically enhanced by addition of bromate. This effect is utilised to develop a sensitive method to determine vanadium in natural waters including sea water. Optimum response was obtained at pH 6.6 in the presence of 20 mM bromate and 0.1 mM catechol; the deposition potential was -0.1 V and the square-wave modulation (50 Hz) was used. The limit of detection was 0.07 nM vanadium using a deposition time of 120 s and 0.6 nM at a deposition time of 15 s.