Enantioseparation of dipeptides by capillary electrochromatography on a teicoplanin aglycone chiral stationary phase

This work deals with investigations on the enantioseparation of glycyl-dipeptides by capillary electrochromatography (CEC) on a capillary packed with teicoplanin aglycone immobilized on 3.5 μm silica gel. The results were compared to those obtained with micro-HPLC using the same chiral stationary phase. Polar organic and reversed-phase mode were checked, whereby the latter showed better results. Out of 12 glycyldipetides investigated, all compounds showed baseline separation with Rs values up to 20. Plate numbers were in the range of 10 000–300 000/m. The choice of organic modifier was found to be crucial. While methanol increased retention time, acetonitrile reduced it. A ternary mixture of ethanol–acetonitrile–aqueous triethylamine acetate solution pH 4.1 was found to be a useful compromise, providing excellent resolution with retention times less than 25 min. Efficiency and resolution were generally found to be higher in CEC than with micro-HPLC.