Three β-cyclodextrin derivatives were prepared: heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)cyclomaltoheptaose (CD-2); heptakis(2,3-di-O-acetyl-6-O-tert-btyldimethylsilyl)cyclomaltoheptaose (CD-3); and heptakis(2-O-methyl-3,6-di-O-tert-butyldimehylsilyl)cyclomalfoheptaose (CD-5). All derivatives possess identical tert-butyldimethylsilyl substituents at the primary hydroxyls but different substituents at the secondary hydroxyls. Each derivative was used to prepare gas chromatographic stationary phases for enantiomer separations. Among the three derivatives studied, CD-2, containing small methyl substituents at the secondary hydroxyls, is the most versatile selector in terms of operating temperature range, enantioselectivity and compound classes that can be separated. CD-3 provides good enantioselectivity but is not suitable for alcohols, amines, and acids as peak tailing was observed. CD-5, with large and buiky substituents at the secondary hydroxyls, can be used in a limited temperature range but, unfortunately, shows no enantioselectivity towards any of tested solutes.
