Chiral separation of ofloxacin enantiomers by ligand exchange chromatography

The enantioseparation conditions of ligand exchange chromatography were examined using ofloxacin enantiomers. A C₁₈ column was used with the mobile phase consisting of a methanol-water solution (containing different concentrations of l-isoleucine and copper sulfate) at flow rate of 0.5 cm ³ min^-1. The effect of different kinds and concentrations of ligands, bivalent ligand ions, and organic modifier, and temperature on enantioseparation were evaluated; the results showed that enantioselectivity was strongly affected by the ligand concentration of the mobile phase. Under the optimum conditions (methanol/water 20:80 v/v, containing 2.5 mmol dm ^-3 l-isoleucine and 0.6 mmol dm^-3 Cu²⁺, room temperature), baseline separation of the two enantiomers was obtained with resolution of 1.32 in less than 30 min. The separation method was used to analyze the ofloxacin enantiomers in different commercial medicines.