Preparation and Retention Behavior of Cyclodextrin-Bonded Stationary Phases on a Silica Support without an Unreacted Spacer Chain

Cyclodextrin-bonded stationary phases on a silica support without an unreacted spacer chain for liquid chromatography were prepared by the reaction of hydride-modified silica with monoallyloxyethylated β- and γ-cyclodextrins, Both cyclodextrins were coupled to 3-(2-tosyloxyethoxy)propyl silica to produce stationary phases with an unreacted spacer chain. The cyclodextrin units in these four stationary phases were connected to the silica surface with the same linkage. The enantiomeric separation ability of these cyclodextrin stationary phases was investigated using eleven dansylamino acids. Both β-cyclodextrin stationary phases exhibited a comparable enantioselectivity, except for dansyl-DL-aspartic and -glutamic acids. However, the β-cyclodextrin stationary phase without an unreacted spacer chain gave a higher column efficiency, compared with the β-cyclodextrin stationary phase with an unreacted spacer chain. On the other hand, the γ-cyclodextrin stationary phase without an unreacted spacer chain was more enantioselective than that with an unreacted spacer chain. The effect of silanization of unreacted silanol groups on the silica surface is discussed.