Abstract: Some underivatized DL-amino acid enantiomers were separated on L-isoleucine-type chiral-ligand-exchange stationary phase (EILE). The effects of contents of copper ion and methanol in mobile phase, temperature of column and flow rate of eluent on the efficiency and resolution of DL-amino acids were investigated in detail. The results showed that Cu(Ⅱ) ion played an important role in the separation. When there was no Cu(Ⅱ) ion in mobile phase, the DL- amino acids could not be enantio-separated, while the content of Cu(Ⅱ) increased from 0.3 mmol/L to 1.2 mmol/L, the efficiency of resolution and retention time decreased. The increases of the content of methanol and column temperature are in favor of the resolution for most of DL-amino acids. The flow rate also affected the resolution results. Good results could be obtained in reducing flow rate but it prolongs the retention time. The mechanisms of different chiral separation results on the new stationary phase under different conditions were also investigated.

Key words: enantiomeric separation , chiral stationary phase, DL-amino acids, L-isoleucine, chiral-ligand-exchange chromatography