Separation of hydroxy acid enantiomers by ligand exchange-micellar electrokinetic chromatography

Hydroxy acid enantiomers have specific bioactivity. Much attention has been paid to their analytical separation. This work investigated their separation and behavior by ligand exchange-micellar electrokinetic chromatography using Cu(II)-L-OH-proline complexes as chiral selectors. Previous work showed that D-amino acid enantiomers migrated faster than L-analogues when Cu(II)-L-proline complexes were used as chiral selectors. The enantiomer migration orders (EMO) of amino acids were reversed by introducing the SDS micellar phase. In the case of hydroxy acid enantiomers, however, it was observed that L-enantiomers migrated faster than the D-forms in both cases of without and with the SDS micellar phase. When CTAB was added to running electrolytes, D-enantiomers migrated as the first peak. Further, when the ligands were changed, different EMOs were observed. The resolution condition, mechanism and behaviors are discussed in this paper.