Separation of α‐hydroxy acid enantiomers by high performance capillary electrophoresis using copper(II)‐L‐amino acid and copper(II)‐aspartame complexes as chiral selectors in the background electrolyte

Abstract

Optical isomers of some α-hydroxy acids, namely 2-, 3-phenyllactic acid, mandelic, p-hydroxy-, m-hydroxy and 3,4-di-hydroxymandelic acid, were separated by means of capillary zone electrophoresis in free solution, using copper (II) complexes with L-amino acid or aspartame ligands in the background electrolyte. The concentration and the pH dependence of the enantiomer separations have been studied in the cases of different chiral ligands and/or analytes. With the use of L-proline as ligand only the optical isomers of 3-phenyllactic acid were resolvable, whereas using L-hydroxyproline the D and L forms of all compounds, except for 2-phenyllactic acid, were separated. Better results were obtained with aspartame as chiral ligand. 1 Part of this work was presented at the 5th International Symposium on High Performance Capillary Electrophoresis, January 25–28, 1993, Orlando, FL, USA.