SEPARATION OF ENANTIOMERIC AMINES AND ACIDS USING CHIRAL ION-PAIR CHROMATOGRAPHY ON POROUS GRAPHITIC CARBON

The application of porous graphitic carbon as adsorbing phase for direct separation of enantiomeric acids and amines using chiral ion-pair chromatography is described. The enantiomeric amines were separated as diastereomeric ion pairs with N-benzyloxycarbonylglycyl-L-proline, N-benzyloxycarbonylglycylglycyl-L-proline, or captopril as the chiral counterion. High enantioselectivities were obtained for amines having a hydrogen bonding function in the vicinity of the asymmetrical carbon atom. Quinine was the chiral counterion used to separate the enantiomeric acids. The strongly UV-absorbing quinine improved detection of solutes having low UV-absorbing properties, e.g., (RS)-2-chloropropionic acid, by "indirect detection." Retention and stereoselectivity of enantiomeric acids were regulated by the quinine concentration and by the addition of carboxylic acids as well as polar modifiers, e.g., methanol and 2-propanol, to the mobile phase.