Systematic modification of the separation selectivity of cyclodextrin-based gas chromatographic stationary phases by varying the size of the 6-O-substituents

Several heptakis(2,3-di-O-methyl)-beta-cyclodextrin derivatives were synthesized in which the size of the primary 6-O-substituent was varied systematically from deoxy-fluoro, through methyl, iz-pentyl, n-propyldimethylsilyl, tert.-butyldimethylsilyl, to triisopropylsilyl. The resulting solid cyclodextrin derivatives were dissolved at identical molal concentrations in OV-1701-vi to form useful gas chromatographic stationary phases for enantiomer separations. It was found that while all phases could be operated at temperatures as high as 250 degrees C, the lower operating temperatures decreased greatly as the size of the substituent increased. Chiral selectivity also varied significantly with the size of the substituent: for almost all of the test compounds chiral selectivity had a local maximum when the substituent was the tert.-butyldimethylsilyl group.