Novel chiral surfactant for the separation of enantiomers by micellar electrokinetic capillary chromatography

A novel chiral surfactant was prepared as both enantiomeric forms, (R)- and (S)-N-dodecoxycarbonylvaline, and employed for the separation of enantiomeric mixtures by micellar electrokinetic capillary chromatography (MECC). The enantioselectivities (alpha) obtained for twelve typical pharmaceutical amines using the (S)-surfactant were compared to those obtained with (S)-N-dodecanoylvaline, a chiral surfactant described in the literature. Higher enantioselectivities were seen for ten of the twelve compounds using (S)-N-dodecoxycarbonylvaline. Furthermore, (S)-N-dodecoxycarbonylvaline had significantly less background absorbance in the low UV. It is shown that exact enantiomer migration order reversal can be obtained by individually employing both enantiomeric forms of the surfactant. For ionizable compounds like the amines examined here, enantioselectivity can be optimized by changing the pH of the MECC buffer. Partitioning is optimized through surfactant concentration, organic additives and pH. The ability to achieve fast chiral separations is shown. A separation of ephedrine enantiomers in urine is shown, with the only sample preparation being filtration.