Chiral separation of newly synthesized arylpropionic acids by capillary electrophoresis using cyclodextrins or a glycopeptide antibiotic as chiral selectors

The chiral separation of two newly synthesized arylpropionic acids of pharmaceutical interest, namely 2-[(5'-benzoil-2'-hydroxy)phenyl]-propionic acid (DF-1738y) and 2-[(4'-benzoiloxy-2'-hydroxy)phenyl]-propionic acid (DF-1770y),was performed by Capillary Zone Electrophoresis (CZE) using either cyclodextrins or antibiotics as chiral selectors in coated capillary. In order to optimize the separation, the effect on the migration time and resolution of type and concentration of the the chiral selector, the buffer pH and the capillary temperature were studied. Several cyclodextrins, namely the charged 6(A)-monomethylamino-beta -cyclodextrin (MeNH-beta -CD) and the neutral methyl-beta -cyclodextrins (M-beta -CD) and heptakis-2,3,6-tri-O-methyl-beta -cycloclextrin (TM-beta -CD), were tested for the enantiomeric separation of aryl propionic acids (APAs) compounds. Of these TM-beta -CD provided the highest enantiomeric resolution at pH 5, however only DF-1738y optical isomers were baseline resolved. Using background electrolytes (BGEs) at higher pHs (pH = 6 - 7) supported with the above listed CDs, an enantioresolution increase was recognized only for compound DF-1738y. In contrast DF-1770y exhibited the highest resolution a[ the lowest pH value studied (pH 4). The macrocyclic antibiotic vancomycin was therefore added to the BGE and tested as chiral selector using the partial filling counter current mode in order to obtain a sensitive analysis, high resolution and reduced antibiotic adsorption on the capillary wall. 5 mM vancomycin dissolved in the BGE at pH 5 and 25 degreesC provided relatively high enantiomeric resolution (RDF-1738y = 3-4, RDF-1770y = 2.22) of both compounds.