Synthesis and characterization of carnitine-based ionic liquids and their evaluation as additives in cyclodextrin-electrokinetic chromatography for the chiral separation of thiol amino acids

In this study, new chiral ionic liquids based on the non-protein amino acid L-carnitine as cationic chiral counterpart and several anions (bis(trifluoromethane)sulfonimide (NTf2 -), L-lactate- or Cl-) as counterions were synthesized. Moreover, three different salts based on L-carnitine were also synthesized and the other three were commercially acquired and used for comparison. The synthesized ionic liquids and salts were characterized by nuclear magnetic resonance, fourier transform infrared spectroscopy, highperformance liquid chromatography-mass spectrometry, and elemental analysis. Subsequently, they were used as additives to establish a gamma-CD-based dual system for the enantiomeric separation of cysteine and homocysteine (previously derivatized with fluorenylmethoxycarbonyl chloride) by capillary electrokinetic chromatography. The effect of the nature of the anionic counterions and the presence of different substituents on the L-carnitine molecule on the chiral separation of both amino acids was investigated. The enantioseparations obtained with each dual system studied were compared in terms of the enantiomer effective mobilities (mu eff) and the effective electrophoretic selectivity (alpha eff). Practically, all the dual systems evaluated exhibited substantially improved enantioseparations for the two amino acids compared with the single gamma-CD system. (c) 2022 The Authors. Published by Elsevier B.V.

Automated summary

In this study, new chiral ionic liquids and salts based on L-carnitine were synthesized and used as additives for enantiomeric separation of cysteine and homocysteine. The chiral separation was significantly improved compared to the single system.