For example pentylation of the 2 and 6 hydroxyl groups followed by the trifluoroacetylation of the 3 position allows strong dispersive interactions with the pentyl group and/or strong polar interactions with the fluoroacetyl group. Thus, any enantiomer that will fit more closely to the chiral cyclodextrin structure will also be able to interact either by dispersive (hydrophobic) or by polar (hydrophilic) forces preferentially to its complimentary enantiomer. This derivatization procedure has been applied to a, b and g cyclodextrins and it has been shown that the g derivative provides more chiral selectivity than the b derivative. As already discussed, the fluoroacetyl group can be easily removed in the presence of water by hydrolysis so all analyses must be carried out under strictly anhydrous conditions.

The simple dipentylation of the cyclodextrins produces a very dispersive (hydrophobic) environment around the chiral centers of the cyclodextrin and, thus, the enantiomer that fits closest to the structure will be more strongly held by dispersive(hydrophobic) forces and, thus, preferentially retained. The selectivity will depend on the size and shape of the analyte as well as the functional groups present.

The substitution of the hydroxyl groups of a cyclodextrin with pure "S" hydroxypropyl groups followed by permethylation yields a polar (hydrophilic) surface that will afford polar interactions with the closest fitting enantiomer and, thus, provide selective retention. All three cyclodextrins can be treated in this way but it has been shown that the b derivative is significantly more selective than either the a or the g derivatives. These stationary phases can be used isothermally up to 200 C and can be programmed up to 220 C.

The permethylated b cyclodextrin has been shown to have broad chiral selectivity, based largely on polar (hydrophilic) interactions and in some cases inclusion/size selectivity. This material is thermally stable up to temperatures of 230 C-250 C and appears to have the potential to separate over 30% of the GC chiral separations published to date.

The dimethyl derivatives of b cyclodextrins have similar temperature stability to the permethyleated products and also exhibit broad chiral selectivity. There is some size selectivity but dispersive (hydrophobic) interactions appear to dominate the retention mechanism.

The stationary phases described above represent the more popular types presently used in chiral GC. There is, however, still a wide range of alternative cyclodextrin derivatives to be synthesized and evaluated and it is certain that many more stationary phases based on the chiral selectivity of cyclodextrin will be developed in the future. Nevertheless, the stationary phases mentioned above will serve to separate most chiral mixtures albeit some analysis times may be long and some may need very high efficiencies to achieve the separation.