FACTORS AFFECTING THE SEPARATION OF MANDELIC-ACID ENANTIOMERS BY CAPILLARY ELECTROPHORESIS

The separation of the optical isomers of mandelic acid by capillary el ectrophoresis using gamma-cyclodextrin as a chiral selector is present ed. The mobility of the enantiomers can be regulated by adjustment of the pH, the concentration of the chiral selector and by the molarity a nd the temperature of the buffer. Different organic modifiers can eith er increase or decrease resolution. The importance of the nature of th e electrolyte is evidenced by the fact that acceptable enantioseparati on has only been achieved using phosphate buffer. The factors affectin g the mobility are discussed. A simple equation describing the apparen t mobility of the analytes in buffers containing cyclodextrins is pres ented. The equilibrium constant for the inclusion complex formation of mandelic acid with gamma-cyclodextrin was found to be 2.8 M(-1) for D -mandelic acid and 2.4 M(-1) for the L-enantiomer.