Chiral calixarenes as potential enantiospecific stationary phases in capillary gas chromatography

Abstract

The ability of a chiral calix(4)arene to participate in host-guest interactions could ultimately lead to new types of stationary phases for performing enantiomeric separations in capillary gas chromatography. For this work, chirality was introduced into p-tertbutylcalix(4)arene via addition of L-phenylalanine to the hydroxyl groups located at the bottom of the cup-like structure. The amino-acid derived p-tertbutylcalix(4)arene was absorbed into the polymeric coating of a non-polar siloxane AT-1 stationary phase using evaporation under reduced pressure. Solute retention times were plotted versus the number of alkyl chain carbon atoms in a homologous series of alkyl benzenes. Deviations in the linearity of this plot suggested some type of contribution to solute retention was resulting, possibly from inclusion of the component(s) into the calixarene cavity. Indications of possible host-guest interactions between the amino acid-derived stationary phase with various analytes were apparent from the band broadening due to the slow kinetics, which are typically observed with host-guest interaction. The ability of this newly derived stationary phase to selectively interact with analytes based on their relative polarity was also determined.