Investigation of enantioselective differences of chiral deep eutectic solvents based on natural organic acids with different configurations in capillary electrophoresis

Due to the unique physicochemical properties, deep eutectic solvents (DESs) have been becoming a promising alternative to conventional organic solvents and ionic liquids. DESs have attracted extensive attention in the field of chiral separation. At present, there are few reports on the enantioselective differences of DESs prepared by natural stereoisomers with different configurations in electrophoretic separation. In this work, the enantioselectivity differences of natural DESs prepared with choline chloride and different configurations of organic acids (D/L/DL-lactic acid, D/L/DL-malic acid) coupled with hydroxypropyl-beta-cyclodextrin as the chiral selectors have been studied in capillary electrophoresis with amperometric detection system for the first time. Four typical adrenergic drugs were selected as the model enantiomers. The relative standard deviations of the migration time, peak area, and resolution were within 7.8 % (n=5), and the limits of detection were 0.030∼0.18 μg·mL^-1 (S/N=3). This developed method has been successfully used for the analyses of chiral active or impurity components in pharmaceutical preparations, and the recoveries were in the range of 96.1∼112 %. It's worth mentioning that L-type organic acid-based DESs could provide better separation effect for (±)-isoproterenol, while D-type organic acids based DESs were more conducive to the enantioseparation of (±)-norepinephrine, (±)-adrenaline, and (±)- terbutaline. For the same enantiomers, the chiral DESs prepared with certain stereoisomeric organic acids can provide the same or better separation efficiency using less DES dosage than the achiral DESs. This provides a novel alternative for the design and preparation of more effective chiral DESs for electrophoretic enantioseparation of specific drugs.