Use of MDL63246 (Hepta-Tyr) antibiotic in capillary zone electrophoresis -II. Chiral resolution of alpha-hydroxy acids

The glycopeptide antibiotic MDL 63 246 (Hepta-Tyr), belonging to the teicop lanin family, has been adopted for the separation of several cr-hydroxy aci d enantiomers by capillary zone electrophoresis (CZE). A polyacrylamide coa ted capillary was employed for the electrophoretic runs in order to suppres s/minimize both the electroosmotic flow (EOF) and the antibiotic adsorption . The experiments were carried out using a background electrolyte (BGE) (aq ueous-organic buffer) in the pH range 1-6 that allowed the analytes to reac h the detector, as negatively charged species, in a relatively short time w hile the antibiotic moved in the opposite direction (positively charged). T he chiral selector, dissolved in the BGE at relatively low concentration, f illed only part of the capillary (partial filling-counter current method) a llowing the detection of analytes with good sensitivity and short analysis time (5-8 min). Experimental parameters influencing the enantioresolution s uch as antibiotic concentration, buffer pH, organic modifier type and conce ntration and capillary temperature were investigated. Hepta-Tyr antibiotic exhibited a high enantiorecognition capability towards mandelic acid and th eir hydroxy and chloro derivatives even at very low concentration (1 mg/ml) using a background electrolyte (BGE) at pH 4 containing 20% (v/v) of metha nol. On the other hand 2- and 3-phenyllactic acids were baseline resolved i n their enantiomers with the same BGE containing acetonitrile and 4 mg/ml o f chiral selector. (C) 1999 Elsevier Science B.V. All rights reserved.