Separation of enantiomers of non-protein amino acids by high-performance liquid chromatography on a chiral ligand-exchange column

The HPLC separation of enantiomers of underivatized non-protein amino acids was investigated by using a column packed with octadecylsilanized silica coated with NS-diOCtyl-D-penicillamine as a chiral ligand-exchange phase (Sumichiral OA-5000). Good enantiomeric separations were achieved with a variety of alpha-amino acids carrying aliphatic or aromatic side chains, cyclic imino acids, and P-amino acids, together with alpha-methyl-alpha-amino acids, by optimizing the amount (0-20%, v/v) of 2-propanol as the organic component and the concentration (1-5 mM) of Cu2+ as the complexing metal ion in the aqueous-organic eluent.