Gas-liquid chromatographic study of the solution thermodynamics of hydroxylic derivatives in selected polymeric liquids

Applications of gas chromatography have been enhanced through conversion of many chemical compounds to derivatives with suitable reagents. This study measured retention volumes of a number of hydroxylic derivatives in polymeric stationary phases. A number of alkanes and aromatics were included in the study for comparison with the derivatives. The stationary phases include a poly(dimethylsiloxane), a poly(methylphenylsiloxane), a poly [methyl(trifluoropropyl)siloxane], and a methoxy poly(ethylene oxide). The selected derivatives were acetates, trimethylsilyl ethers, trifluroroacetates, and pentafluoropropionates. The hydroxylic compounds included butyl alcohol, cyclohexanol, and m- and p-methylphenols; n-butyl tert-butyl ether was included for comparison with n-butyl trimethylsilyl ether. The effects of derivatizing groups on the interaction parameter were considered as a summation of hydrocarbon core and derivative groups. Linear free energy relationships were identified for n-alkanes, aromatics, and n-butyl derivatives. Some thermodynamic results could be interpreted in terms of molecular structure of molecules and specific solute-solvent interactions. Results here support an approach to selecting derivatives for separations matched to column liquid phases.