COMPARISON OF 2 FREE-ENERGY OF SOLVATION MODELS FOR CHARACTERIZING SELECTIVITY OF STATIONARY PHASES USED IN GAS-LIQUID-CHROMATOGRAPHY

Two solvation energy models, developed independently for the characterization of the solvent properties of gas-liquid chromatographic stationary phases, are compared using accurately determined gas-liquid partition coefficients for 30 test solutes on 25 stationary phases at a common reference temperature. Remarkably good agreement between the regression model of Abraham and the free energy model proposed by Poole is demonstrated for the contributions to retention characterized by cavity formation, nonpolar interactions and polar interactions. Exceptional behavior for the liquid organic salts is explained by the differences between the experimental and predicted gas-liquid partition coefficients for the n-alkanes used in the two models. In addition, both models conclusively demonstrate that at the measurement temperature, 121.4-degrees-C, none of the stationary phases behave as significant hydrogen-bond acid solvents, contrary to commonly held beliefs.