Separation of positional isomers on polymeric calix[4]arene-siloxane stationary phases in capillary GC

Poly(p-tert-butyldimethoxydipropyloxycalix[4] arene-tetramethyldisiloxane) (TBCX-TMDS) and poly(dimethoxydipropyloxycalix[4] arene-tetramethyldisiloxa ne) (CX-TMDS), have been prepared and used as stationary phases for isother mal capillary gas chromatographic separations of positional isomers. Retent ion factors and separation factors for the isomers were measured. The isome rs investigated were well-resolved on the two phases. Retention of all the solutes investigated is greater on TBCX-TMDS than on CX-TMDS, probably beca use of extra dispersive interactions of the solutes with the tert-butyl gro ups of the phase. Separation factors for closely-eluting isomer pairs are s imilar on the two phases. This seems to indicate either that the solutes ar e retained by non-inclusion processes or that if the isomer molecules do en ter the cavity of the calixarene, i.e. the solute is retained by inclusion, the tert-butyl groups do not play a role in discriminating between the iso mers.