Cyclocholates as chiral selectors for capillary gas chromatography - Effect of temperature conditioning on the chromatographic behavior of the stationary phase

The suitability of cyclocholates as chiral selectors in gas chromatography has been evaluated. We present the synthesis and characterization of two cy clocholates, viz. 3 alpha,7 alpha-diacetoxycyclo[3]cholate and 3 alpha,7 al pha-diacetoxycylo[4]cholate. Mixtures of these new selectors with polysilox anes were tested as chiral stationary phases in capillary gas chromatograph y. Several enantiomer separations of common racemates were achieved,with th e 3 alpha,7 alpha-diacetoxycyclo[3]cholate at 10% in OV-1701 (w/w). It was shown that column efficiency was strongly dependent on temperature and that enantioselectivity was very sensitive to column conditioning. This chromat ographic behavior suggested that cyclocholates were only dispersed in polys iloxane. Thus, it was assumed that chiral discrimination occurred aa enanti oselective adsorption interactions of enantiomers at the surface of the sol id chiral selector dispersed in the polysiloxane matrix OV-1701.