Simultaneous Determination of Chromium(III) and Chromium(VI) in Aqueous Solution by Capillary Electrophoresis with On-Column UV-VIS Detection

Chromium(III) and Chromium(VI) have been speciated by capillary electrophoresis(CE) with on-column UV-Vis detection at 254 nm and a negative potential. Chromium(III) has been converted to an anionic complex using ethylenediaminetetraacetate (EDTA) to be detected simultaneously with Cr(VI) by CE. A cationic surfactant, cetyltrimethylammonium bromide (CTAB), was added to a buffer solution of 10 mM phosphate in order to reverse the electroosmotic flow (EOF) in the capillary. This results in a short analysis time and better peak shapes. The effect of the buffer pH over the range of 6 to 11 on the separation of each species has been observed. Nitrate and chromate have been nicely separated at a higher pH. Linear calibrations for chromate and a chromic EDTA complex were established over the concentration range of 50–200 pg/nl with detection limits of 1. 5 pg/nl and 5 pg/nl, respectively, using a 10 mM phosphate buffer and a 0. 5 mM CTAB solution.