Enhanced enantioselectivity of native α-cyclodextrins by the synergy of chiral ionic liquids in capillary electrophoresis.

In the cyclodextrins family, the native α-cyclodextrin has almost been abandoned in capillary electrophoresis chiral separation due to its much weaker enantioselectivity compared with β-cyclodextrin and their derivatives. In this work, several amino acid chiral ionic liquids were selected to establish synergistic enantioseparation systems with native α-cyclodextrin. Enhanced enantioselectivities were observed in the chiral ionic liquids/α-cyclodextrin synergistic systems compared with single α-cyclodextrin system. A series of comparison experiments were performed to demonstrate the superiority of the synergistic systems. Primary parameters affecting the enantioseparation were systematically optimized, including the type and concentration of chiral ionic liquids, α-cyclodextrin concentration, buffer pH, and applied voltage. Best separations of the model enantiomers were obtained in a 20 mM Tris/H3 PO4 buffer at pH 2.5 containing 3% (m/v) α-cyclodextrin and 30 mM tetramethylammonium-l-arginine. The results show that the α-cyclodextrin is also worth our attention when selecting chiral selectors for capillary electrophoresis enantioseparation of specific racemic compound.