Evaluation of ionic liquids-coated carbon nanotubes modified chiral separation system with chondroitin sulfate E as chiral selector in capillary electrophoresis

Nanoparticles (NPs) and ionic liquids (ILs) have been extensively studied and have aroused considerable interest in separation science; however, the employment of ILs-dispersed NPs as buffer modifiers for CE chiral separation has not been previously studied. In this work, we describe a new CE method using ILs dispersed multi-walled carbon nanotubes (ILs-MWNTs) as a modifier for enantioseparation with a polysaccharide, chondroitin sulfate E (CSE), as the chiral selector. As observed, significantly improved separations, including better enantioselectivity and improved peak shapes, were obtained in the ILs-MWNTs modified separation system for all drug enantiomers compared to the single CSE system. Several parameters affecting the enantioseparation, such as the choice of ILs and carbon nanoparticles, ILs-MWNTs concentration, chiral selector concentration, buffer pH and applied voltage, were systematically investigated. Satisfactory separations were achieved when 2.4 μg/mL ILs-MWNTs were introduced into the 20 mM Tris/H3PO4 buffer solution containing 2.5% CSE at pH 2.8-3.4 with a 15 kV applied voltage. A brief mechanism of the enhanced enantioseparation capability of the ILs-MWNTs modified chiral separation system was also discussed.