Determination of Cr(VI) by Catalytic Adsorptive Stripping Voltammetry with Application of Nitrilotriacetic Acid 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 catalytic adsorptive stripping voltammetry is presented. For minimization of Cr(III) interference nitrilotriacetic acid was used as a masking agent. The determinations were performed in a flow system. The calibration plot was linear from 1×10^?10 to 1×10^?8 mol L^?1 for accumulation time 60 s. The relative standard deviation for 3×10^?9 mol L^?1 Cr(VI) was 4.1% (n=5). The detection limit for an accumulation time of 60 s was 4×10^?11 mol L^?1. The influence of common foreign ions is also presented. The performance of the method was verified by analysis of certified reference material for Cr(VI) and comparing the results of analyses of natural water samples with those obtained by another accepted electrochemical method.