Comparative studies on the enantioseparation of hydrobenzoin and structurally related compounds by capillary zone electrophoresis with sulfated β-cyclodextrin as the chiral selector in the presence and absence of borate complexation

Comparative studies on the enantioseparations of racemic hydrobenzoin, together with benzoin and benzoin methyl ether, in capillary zone electrophoresis using sulfated β-cyclodextrin (S-β-CD) as a chiral selector in the presence and absence of borate complexation were investigated. The influences of S-β-CD concentration on the enantioseparation of benzoins in a borate buffer and a phosphate background electrolyte and the influences of the concentration and the pH of borate buffer containing S-β-CD on the enantioseparation of hydrobenzoin were examined. The results indicate that, depending on the degree of strong borate complexation and comparatively weak CD complexation, the selectivity of the enantiomers of hydrobenzoin can be greatly reduced in a buffer system containing borate ions. Enantioseparation of hydrobenzoin is mainly governed by the interaction between hydrobenzoin–borate complexes and S-β-CD in a borate buffer, whereas enantioseparation of benzoins is primarily determined by CD complexation in a phosphate background electrolyte. Effective enantioseparations of benzoins were simultaneously achieved with addition of S-β-CD at a concentration greater than 3.0% (w/v) in a borate buffer and at a concentration greater than 2.5% (w/v) in a phosphate background electrolyte at pH 9.0.