MECHANISM OF GAS-LIQUID-CHROMATOGRAPHIC SEPARATION OF DISUBSTITUTED BENZENE ISOMERS USING NEMATIC LIQUID-PHASES

From measurement and analysis of specific retention volumes of four pairs of meta and para isomers at four well controlled temperatures in the liquid-crystalline stationary phase p,p′-dihexoxyazoxybenzene, precise solute free energy, enthalpy and entropy parameters are obtained. It is found that the para isomer is more soluble and is retained longer, due to its more favorable excess enthalpy and enthalpy of solution. This behavior is interpreted in the light of current theories of nematic solutions, and a plausible separation mechanism is proposed. The extent to which this mechanism may be extended to other geometric isomers is discussed. © 1979.