Investigation of the enantioselectivity of tetramethylammonium-lactobionate chiral ionic liquid based dual selector systems toward basic drugs in capillary electrophoresis

Recently, chiral ionic liquids (CILs) have received increasing interest in chiral separation by CE. Nevertheless, the lack of deep perception of the specific mechanism about CILs in CE for enantioseparation still perplexes a legion of researchers, despite the strenuous efforts. In this paper, a lactobionic acid based ionic liquid, tetramethylammonium-lactobionate (TMA-LA) was applied for the first time in CE to establish dual selector system with clindamycin phosphate (CP) for enantiomeric separation. Compared to single CP system or single TMA-LA system significantly improved separations of seven tested rameric drugs (propranolol, nefopam, citalopram, chlorphenamine, metoprolol, bisoprolol, and esmolol) were observed in the dual selector systems. Several crucial parameters such as type and proportion of organic modifier, buffer composition and pH, and concentration of TMA-LA/CP were systematically investigated to achieve satisfied enantioseparation. Meanwhile, molecular modeling was applied to demonstrate the chiral recognition mechanism of the TMA-LA/CP dual-selector separation system using the molecular docking software Autodock, which well supported the experimental results. The existence of TMA-LA/CP complex may give rise to a higher discriminatory ability against the enantiomers, indicating the reason of improved separation in TMA-LA/CP system. All the influence factors evaluated by means of Statistical Product and Service Solutions (SPSS) to research the influences on the chiral separation system.