Stereoselective D- and L-amino acid analysis by high-performance liquid chromatography

This paper describes a gradient system for separating D- and L-isomers of Dns-amino acids by mixed chelate complexation through the addition of histidine methyl ester and copper sulfate to the mobile phase. Most of the biologically important amino acids were separated in a single analysis. With a simple solvent gradient consisting of increasing concentrations of acetonitrile in L-histidine methyl ester buffer all the common amino acids were resolved except cysteine and all optical isomers were resolved except those of threonine, alanine and proline. Analysis time was 90 min. Use of this system for determining non-protein amino acids in human cerebrospinal fluid showed the amino acids to be L-isomers, as expected. The pattern in fluid from a patient with bacterial meningitis was different from that of most of the others.