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

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. Part of this work was presented at the 5th International Symposium on High Performance Capillary Electrophoresis, January 25–28, 1993, Orlando, FL, USA.