Chiral analysis of UV nonabsorbing compounds by capillary electrophoresis using macrocyclic antibiotics: 1. Separation of aspartic and glutamic acid enantiomers

Glycopeptide antibiotics, namely vancomycin or teicoplanin, were evaluated in capillary electrophoresis for the analysis of UV nonabsorbing compounds such as aspartic and glutamic acid enantiomers. Electrophoretic runs were p erformed in laboratory-made polyacrylamide-coated capillaries using the par tial filling-counter current method in order to avoid the presence on the d etector path of the absorbing chiral selector. The background electrolyte c onsisted of an aqueous or aqueous-organic buffer in the pH range of 4.5-6.5 of sorbic acid/histidine and the appropriate concentration of chiral selec tor. Several experimental parameters such as antibiotic concentration and t ype, buffer pH, organic modifier, type and concentration of absorbing co-io n (for the indirect UV detection) were studied in order to find the optimum conditions for the chiral resolution of the two underivatized amino acids in their enantiomers. Among the two investigated chiral selectors, vancomyc in resulted to be the most useful chiral selector allowing relatively high chiral resolution of the studied compounds even at low concentration. The o ptimized method (10 mM sorbic acid/histidine, pH 5, and 10 mM of vancomycin ) was used for the analysis of real samples such as teeth dentine and beer.