Metal complex separation with on-line sample preconcentration in micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) using a cationic surfactant as a pseudostationary phase was examined to separate anionic metal cyclohexane-1,2-diaminetetraacetic acid (CDTA) complexes. Cetyltrimethylammonium chloride (CTAC) was employed as the cationic surfactant micelle, its addition leading to EOF reversal. Cu(II), Co(II), Zn(II), Mn(II) and Pb(II) were used as test analytes, and the complete separation was obtained by MEKC. On-line sample preconcentration by sweeping was also examined to improve the detection sensitivity. From 15- to 42-fold increases in the detection sensitivity in terms of the peak heights were obtained by sweeping with a cationic micelle in the presence of high EOF. The limits of detection were in the range (0.6 - 1.8) x 10(-6) M with UV detection without any off-line preconcentration step.