Voltammetric determination of Cr(VI) in the presence of Cr(III) with application of CDTA as a masking agent

A selective and sensitive method for determination of traces of Cr(VI) in the presence of a large excess of Cr(III) by differential pulse adsorptive stripping voltammetry is presented. For minimization of Cr(III) interference cyclohexanediaminetetraacetic acid (CDTA) was used as a masking agent. The determinations were performed in a flow system. The calibration graph is linear from 5 x 10(-10) to 2 x 10(-8) mol l(-1) for accumulation time 60 s. The relative standard deviation for 1 x 10(-8) mol l(-1) Cr(VI) is 5.8% (n = 5). The detection limit for an accumulation time of 60 s is 2 x 10(-10) mol l(-1). The influence of common foreign ions is also presented. The validation of the method was made by comparing the analytical results for water and soil samples with those obtained by reference methods and by a recovery test for river water.