STRUCTURAL CHARACTERISTICS OF PENDANT AND COPOLYMERIC CYCLODEXTRIN POLYSILOXANE STATIONARY PHASES AND THEIR INFLUENCE ON CHIRAL SELECTIVITY AND RESOLUTION IN CAPILLARY GAS-CHROMATOGRAPHY

The dependence of gas chromatographic properties on stationary phase structural characteristics was evaluated for three different types of cyclodextrin-bonded polysiloxanes: small-rim-tethered, large-rim-tethered, and copolymeric. Separation efficiency, chiral selectivity, and resolution were investigated as functions of stationary phase structural features such as length and chemical composition of the connecting arms, chemical composition of the substituent groups on the small rim of the cyclodextrin toroid, and the position(s) of connecting arm attachment(s) on the cyclodextrin rims. For all of the solutes and experimental conditions used in this study, the small-rim-tethered cyclodextrin phases were found to provide superior chromatographic performances compared to the other two types of cyclodextrin phases. The chiral selectivities of the investigated phases were found to depend both on chemical composition and length of the connecting arm(s). Shorter connecting arms were found to provide improved chiral selectivities. Stationary phases having a four-carbon connecting arm with an etheric oxygen linkage in the chain provided higher chiral selectivities compared to stationary phases with hydrocarbon or phenoxy group-containing connecting arm(s). The chiral selectivities of the studied phases did not change when the substituents at the C-6 positions were changed from -CH2OCH2 to -CH3. Efficiency values of up to 5,000 theoretical plates per meter were obtained using 200 mum i.d. columns. Column efficiency was found to be independent of structural features of the cyclodextrin toroid and the connecting arms.