Catalytic-adsorptive stripping voltammetric determination of chromium in environmental materials

Trace levels of chromium in natural water, soil and plants can be determined directly after accumulation of the chromium(III)-2,2-bipyridine complex on a hanging mercury drop electrode, coupled with the catalytic effect of the adsorbed complex on the reduction of nitrite. The adsorptive-catalytic characteristic of the complex provides the needed sensitivity and selectivity for direct determination of ultratrace concentrations of chromium in environmental samples. The effect of various experimental parameters on the catalytic current was investigated. Under optimal conditions, the adsorptive-catalytic stripping voltammetric procedure produces a detection limit of 20 pM (1.0 ppt) chromium and a linear catalytic current-chromium concentration relationship up to 50 nM, following 5 s of accumulation. Most of the coexisting metals do not interfere with the measurements.