Separation of D and L Amino Acids by Liquid Chromatography: Use of Chiral Eluants

An aqueous eluant containing a chiral copper-proline complex effects the separation of underivatized amino acid enantiomers on an ion-exchange column. The stereoselectivity is ascribed to differences in stability of the diastereomeric amino acid-copper complexes formed in solution. A simple change in the chirality of the eluant reverses the order of the enantiomer elution. For detection and quantification of picomole amounts of amino acids, the eluant is monitored for fluorescence after reaction with o-phthalaldehyde, a reagent insensitive to proline but highly sensitive for amino acids containing a primary amino group.