Inspection of the reversal of enantiomer migration order in ligand exchange micellar electrokinetic capillary chromatography

Enantiometers of D,L-phenylalanine were separated by capillary electrophore sis based on the principle of ligand exchange. Copper (II) complex of 4-hyd roxy-L-proline was used as chiral selector. The separation and the migratio n order of D- and L-phenylalanine were strongly affected by adding an anion surfactant sodium dodecylsulfate (SDS). Without SDS in the electrolyte, th e separation was also carried out but the resolution was very small. With S DS added into the electrolyte, the resolution decreased with increasing con centration of SDS until 5.0 mM. When the concentration of SIDS in the elect rolyte was over 5.0 mM I, inversion of the migration order of DL-phenylalan ine was observed and the resolution was also increased with increasing conc entration up to 20 mM. It was interesting to find that the inversion of the migration order took place not only in the enantioseparation but also in t he positional isomers. A family of a fluorinated amino acid, o-, m- and p-f luoro-D.L-phenylalanine was separated and the inversion of the migration or der is discussed. Copyright (C) 2001 John Wiley & Sons, Ltd.