Chiral separation of monoterpenes using mixtures of sulfated beta-cyclodextrins and alpha-cyclodextrin as chiral additives in the reversed-polarity capillary electrophoresis mode

The use of mixtures of sulfated beta-cyclodextrins and native alpha-cyclodextrin as chiral additives in capillary electrophoresis was evaluated for the chiral resolution of neutral, cyclic and bicyclic monoterpenes, including alpha-pinene, beta-pinene, camphene and limonene. Binding properties of sulfated beta-cyclodextrins towards these monoterpenes were studied. It was found that there was no enantioresolution of these terpenoids over the concentration range studied. However, the addition of alpha-cyclodextrin to the running electrolyte in addition to 6.5 mM sulfated beta-cyclodextrins, imparted differences in the mobilities of the terpenoid enantiomers and resulted in remarkable enantiomeric separations of alpha-pinene (R(s)=25), beta-pinene (R(s)=12), camphene (R(s)=12) and limonene (R(s)=4). The role of both alpha-cyclodextrin and sulfated beta-cyclodextrins in these separations is discussed.