Cyclodextrins with heterocyclic substitution as GC stationary phases

Abstract

SummaryTwo new cyclodextrin (CD) derivatives, heptakis{2,6-di-were synthesized and coated on fused-silica capillary columns. Their chromatographic characteristics, including column efficiency, polarity, selectivity and phase transition were studied and compared with similar I~-CD stationary phases. It was found that the heterocycle group has a significant effect on the selectivity of the CD stationary phases. Both stationary phases can be successfully used to separate many di-and trisubstituted benzene positional isomers and show stronger separation ability in separating low-polarity benzene positional isomers than other ~-CD stationary phases.

Capillary GC using pyridyl β‐cyclodextrin stationary phase

“…[19], and so on [18,20]. As for other aromatic positional isomers, such as xylene, the separation efficiency is also better than other b-CD stationary phases although the peak orders of these were different [13,20]. This might be attributed to the action of the pyridyl group, which not only has a stronger induction effect but also stronger p-p interaction with aromatic compounds.…”

“…Because a p-p conjugated system exists in the pyridine structure, the polarizable ability of the stationary phase is also enhanced, as can be deduced from the increasing DI of benzene and pyridine. It should be mentioned that the polarity of the pyridyl b-CD derivative is lower than that of other heterocyclic b-CD derivatives in terms of the difference in substituted group on the 3-positions of b-CD [13].…”

“…It shows that the stationary phase has relatively moderate polarity, and is suitable for the separation of polar and easily polarizable compounds. By comparison of DI between the prepared stationary phase and heptakis (2,3,6-tri-O-pentyl)-b-CD (II are listed) [13], the most important variations can be noticed from 1-butanol (D = 111) and 2-pentanone (D = -28). Retention behaviors of these two probes are related to the hydrogen bonding ability and the dipolar character of the stationary phase, respectively.…”

“…However, there are only two reports, at present, concerning the exploration of a b-CD derivative with heterocyclic groups. Fu et al [13] firstly prepared two kinds of isoxazolyl b-CD derivatives as stationary phases in capillary GC. Although they showed stronger separation ability to benzene positional isomers, there was no attempt to further study the enantioselectivity.…”

Investigation on five novel substituted β-cyclodextrins used as GC stationary phases

“…Heptakis-(2,6-di-O-pentyl-13-CD) were synthesized according to the method previously used [7]. Synthesis of heptakis[2,6-di-O-pentyl-3-O-(4-nitrobenzyl)]-13-CD (CD-I).…”