Cyclodextrins-based deep eutectic supramolecules as chiral selectors for enhanced enantioseparation in capillary...

The joint use of deep eutectic solvents (DESs) and cyclodextrins (CDs) has been well demonstrated to have a promoting effect on chiral separation in capillary electrophoresis (CE). These studies focused on constructing synergistic separation systems by adding DESs and CDs to the buffer solution respectively. In this work, for the first time, β-cyclodextrin (β-CD), methyl-β-cyclodextrin (M-β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD) were directly used as precursors to prepare several CDs-based deep eutectic supramolecules (DESUPs) by assembling with two organic acids (L-lactic acid and L-malic acid) in different ratios through a simple two-phase mixing. These CDs-based DESUPs were further employed as chiral selectors in CE to separate six racemic chiral drugs. Compared with the unmodified CDs systems, the separations of model drugs in the DESUPs separation systems were significantly improved. We calculated the binding constants of HP-β-CD with enantiomers before and after preparation as DESUPs, and investigated the chiral recognition mechanism of DESUPs chiral selectors using UV spectroscopy and nuclear magnetic resonance method. The enhanced enantioselectivity of CDs-based DESUPs was attributed to several factors. This study has opened up a new path for the exploration of high-performance chiral materials.