Speciation of Cr(III) and Cr(VI) and separation of common anions by ion pair chromatography with trans-1,2-diaminecyclohexane-N,N,N',N'-tetraacetic acid

A reversed phase ion pair chromatographic method for the simultaneous determination of Cr species and common anions on a C(18)-bonded stationary phase was developed by using acetonitrile-water (2:98 v/v) containing 1.0 mM tetrabutylammonium hydroxide and 0.5 mM trans-1,2-diaminecyclohexane-N,N,N',N'-tetraacetic acid (DCTA) at pH 6.5 as mobile phase and UV-detection at 210 nm. Chromatographic parameters were optimized for separation of Cr(III)-DCTA complex, chromate and other anions. The detection limits were found as 8 ng/ml for Cr(III) and 35 ng/ml for Cr(VI). Under the optimum conditions, most other ions did not interfere. The method can be applied to separate a number of common anions simultaneously with the separation of Cr(III) and Cr(VI).