Determination of Cr(III) and Cr(VI) by Ion Chromatography

Abstract

Simultaneous separation and determination of Cr(III) and Cr(VI) was carried out on a multifunctional ion-exchange column Dionex IonPac CS5A in the anion-exchange mode. Cr(III) cations were converted to negatively charged complexes by pre-column derivatization with cyclohexane-1,2-diamine-N,N,N',N'-tetraacetic acid (CDTA) prior to separation. The mobile phase contained 100 mmol l⁻¹ ammonium acetate, 10 mmol l⁻¹ sodium perchlorate and 2 mmol l⁻¹ CDTA. Post-column derivatization with diphenylcarbazide was employed for photometric detection of Cr(VI). The proposed method allows to determine Cr(III) at a level of 10⁻¹ mg l⁻¹ and Cr(VI) at 10⁻³ mg l⁻¹ with high precision. Relative standard deviations of repeatability ranged from 0.6 to 3.9 % in dependence on the analyte concentration. The procedure was used for analyses of various industrial (plating baths) as well as environmental samples.