Based on chiral ligand exchange, the distribution behavior of ofloxacin enantiomers in the two-phase system containing copper(Ⅱ) ion (Cu²⁺) and N-n-dodecyl-L-proline (L) was studied.At different pH, the partition of Cu²⁺ in the two-phase system containing N-n-dodecyl-L-proline, was investigated.The influence of pH, concentrations of Cu²⁺ and chiral ligand on partition coefficients (K) and separation factors (α) was discussed.The experimental results show that L forms more stable ternary complex with R-ofloxacin enantiomer than with S-enantiomer.There is a large influence of pH on K and α.At low pH values (3.5), formation of binary complexes is thermodynamically unfavourable.K and α are the best when pH values are above 3.5 and the molar ratio of chiral ligand to Cu²⁺ is 2:1.The concentration ratio of S to R (1.72) was obtained in the aqueous phase by 2×1 hollow fiber membrane extraction.

Key words: ligand exchange, extraction, chiral separation, ofloxacin enantiomer