Cyclodextrin And Its Derivatives In The Chiral Separation In Capillary Electrophoresis Study

Cyclodextrins are cyclic oligosaccharides consisting of at least six glucopyranose units which are joined byα(1â†'4)linkages. The oligosaccharide ring form a truncated cone with the primary hydroxyl groups of the glucose residues lying on the narrow end of the truncated cone and the secondary hydroxyl groups are located on the wide end. Therefore the cyclodextrins have a relatively hydrophobic interior and hydrophilic exterior. Cyclodextrins are ideal as chiral selector in CE because of their ability to form host-guest complexes with a variety of compounds. All kinds of native cyclodextrins and cyclodextrins derivatized by charged or uncharged groups are used. Among those modified cyclodextrins 2-hydroxypropyl-β- cyclodextrins and 6-sulphobutyl ether-β- cyclodextrins are the best chiral selector. Nowadays, someβ- cyclodextrins polymers are studied in host-guest chemistry. In this paper we synthesized six kinds of β- cyclodextrins polymers and used in enantiomeric separation of amino acid by capillary electrophoresis. The effect of the organic modifier of the buffer also studied .As a resultβ- cyclodextrins polymers are more effect than 2-hydroxypropyl-β- cyclodextrins, hetrakis(2,6-methyl) β- cyclodextrins and hetrakis(2,3,6-methyl) β- cyclodextrins. The length and the structure of the link also plays an important role in separation. We think this is because of the cooperative interaction of the cyclodextrins' cavities and the link spaces lead to the larger binding constant Kb of cyclodextrins polymers to the guest molecule. Furthermore, if the link of the polymer too long ,it will enter the cavity of cyclodextrins or decrease the cooperation interaction of the cyclodextrins.As a result the polymer not so useful in chiral separation.