COMPARISON OF VARIOUS BULK FLUIDS AND MODIFIERS AS NEAR-CRITICAL MOBILE PHASES ON A POLYMERIC COLUMN USING LINEAR SOLVATION ENERGY RELATIONSHIPS

Linear solvation energy relationships (LSERS) were used to quantitativ ely compare the relative contributions of dipolarity/polarizability, h ydrogen bonding, and other types of intermolecular interactions to ret ention and selectivity using various bulk mobile phase components. Usi ng experimental conditions which differ only by the composition of the bulk mobile phase component, the factors which cause selectivity to d iffer between HPLC, subcritical fluid chromatography and supercritical fluid chromatography were deconvoluted, Heptane-based HPLC mobile pha ses showed superior selectivities towards analytes which differ in hyd rogen bond donating ability, gas-to-hexadecane partition coefficient a nd dipolarity/polarizability, Subcritical fluid chromatography with HF C-134a (1, 1, 1,2-tetrafluoroethane) as the bulk fluid produced superi or selectivities for analytes which differ in hydrogen bond accepting ability and excess molar refraction properties. Many of these factors showed temperature dependences which act to attenuate or accentuate th e particular intermolecular interaction.