Determination of Cr(VI) in the presence of high excess of a Cr(III) by adsorptive stripping voltammetry

A sensitive and highly selective adsorptive stripping voltammetric procedure for determination of traces of Cr(VI) is presented. Cr(III) interference was minimized due to (a) partial adsorption of this form of chromium from the sample on aluminum oxide and (b) using as a detection method adsorptive stripping voltammetry, which allows for selective determination of Cr(VI) in the presence of a 100-fold excess of Cr(III). The procedure can be used for determination of Cr(VI) even in the presence of a 10,000-fold excess of Cr(III). Conditions of Cr(III) adsorption on aluminum oxide were optimized while conditions of Cr(VI) determination were based on literature data. The calibration graph for Cr(VI) for an accumulation time of 30 s was linear from 1 × 10−9 to 4 × 10−8 mol L−1. The detection limit was 7 × 10−10 mol L−1. The proposed procedure was applied for Cr(VI) determination in a river water sample.