Separation of Enantiomers Using a γ-Cyclodextrin Liquid Chromatographic Bonded Phase

A γ-cyclodextrin bonded phase was used for the enantiomeric separation of various compounds including several chiral crown ethers and dansylated amino acids. Methanol/buffer solutions were used as the mobile phase. Earlier studies of enantiomeric separations on β-cyclodextrin bonded phases have shown that enantiomers in which the chiral center was the α substituent on a naphthyl ring were unresolved on the β-cyclodextrin bonded phase. In contrast, several enantiomeric pairs of this type were readily resolved on the γ-cyclodextrin bonded phase. In addition, the γ-cyclodextrin bonded phase was able to resolve several enantiomeric pairs in which the optical activity was the result of an axis of dysymmetry rather than a stereogenic atom. Differences in the previously reported selectivity on β-cyclodextrin and the results reported here for the γ-cyclodextrin bonded phase are examined and discussed in terms of the overall retention mechanism.