Background: Chiral selectors play a vital role in the separation efficiency for chiral separation
techniques. Recently much attention has been devoted to chiral ionic liquids (CILs) derived from
natural sources, which could be used as chiral selectors in chiral discrimination.
Objective: In this study, chiral ionic liquids with L-phenylalanine ester as cations (L-phenylalanine
ethyl ester bis (trifluoromethanesulphonyl) imide) were synthesized and applied as novel chiral ligand
for chiral separation.
Method: Ligand exchange chromatography with L-phenylalanine ethyl ester bis (trifluoromethanesulphonyl)
imide as chiral selector was used to separate ofloxacin enantiomers. The effects of copper ion concentration, Lphenylalanine
ethyl ester bis(trifluoromethanesulphonyl)imide concentration, organic modifier ratio, pH of the mobile
phase as well as temperature on efficiency of chiral separation were investigated and evaluated.
Results: Optimal separation conditions were obtained, where 8 mmol/L this chiral ionic liquids and 4 mmol/L Cu2+ were
dissolved in methanol/water (12:88, v/v) with pH 4.8. Under the optimum conditions, well enantioseparation of ofloxacin
enantiomers could be observed with the resolution of 1.84.
Conclusion: The results demonstrated the good applicability of the chiral ionic liquids with amino acid ester as cations to
separate ofloxacin enantiomers in ligand exchange chromatography. It also exhibited the potential for the separation and
determination of other chiral medicines by an ionic liquid-assisted ligand-exchange method, and would extend the application
of chiral ionic liquids in separation science.