Combining the enantioselectivity of a cyclodextrin and a diamide selector in a mixed binary gas-chromatographic chiral stationary phase

The present work reports on the investigation of a mixed binary chiral stationary phase (CSP) prepared by simultaneous attachment of permethylated‐β‐cyclodextrin (D selector) and resorcinarene with pendant l‐ or d‐valine diamide groups (L′ and D′ selectors, respectively) to a polysiloxane matrix via platinum‐catalyzed hydrosilylation. The gas‐chromatographic investigation of a number of racemates on the four different CSPs (D, D′, DD′, and DL′) showed that the enantioselectivity of the individual chiral selectors was retained in the mixed binary CSPs. As a consequence, hydrocarbons, underivatized alcohols, ketones, and almost all proteinogenic amino acid derivatives could be separated simultaneously on each of the mixed CSPs. Matched and mismatched cases of enantioseparation on the mixed binary CSPs were observed but turned out to be of minor importance for enantiomeric separation. In general, more racemates were separated with α ≥ 1.02 on the mixed phases as compared to the single phases. In order to analyze the influence of the presence of the diamide selector on the enantioselectivity of the cyclodextrin selector, a mixed ternary CSP containing the selector D and a racemic mixture of the selectors D′ and L′ [D(D′L′)] was prepared and investigated. Merits and limitations of the approach of mixed binary CSPs are discussed. © 2005 Wiley‐Liss, Inc. Chirality