Enantioseparation of amino acid derivatives by capillary zone electrophoresis using vancomycin as chiral selector

The separation of racemic derivatized amino acids (N-acetyl) in their enantiomers was achieved using capillary zone electrophoresis employing vancomycin as a chiral selector. Due to the strong absorption properties of the chiral selector at the low wavelengths used, the partial filling- counter current method was adopted in order to improve the method sensitivity. In the separation system experimented the chiral selector filled only a part of the capillary and, due to the appropriate selection of the pH, was moving in the opposite direction of the analytes keeping the detector free of absorbing compounds. The effect of several experimental parameters on enantioresolution of analytes was studied, e.g., vancomycin concentration (0-5 mM), pH of the background electrolyte (pH 4-7), capillary temperature (15-35 °C) and presence of an organic modifier into the run buffer (methanol or ethanol or n-propanol). N-acetyl glutamic acid, serine, cystine, tyrosine and proline were all baseline resolved in their enantiomers and the enantioresolution factor (Rs) increased by raising the vancomycin concentration. pH 4 allowed the baseline resolution of the 5 studied analytes in presence of 2.5 mM of chiral selector and an increase of pH caused a decrease of (Rs).