Characterization of various reversed-phase columns using the linear free energy relationship II.: Evaluation of selectivity

Using the database presented in Part I of this series [J. Chromatogr. A, 818 (1998) 1] selectivity factors for various solute pairs with known linear free energy relationship (LFER) solvation parameters have been studied. Selectivity factors of selected solute pairs have been used to characterize hydrophobic properties and different types of molecular interactions of widely different reversed-phase columns. For reversed-phase packings evaluated under the same mobile phase composition differences in chromatographic selectivity can be attributed to the structure and characteristics of the stationary phase. Significant correlations have been found between the regression coefficients of the LFER equation and the different types of selectivity, as hydrophobic selectivity and polar selectivities. It has been established that hydrophobic selectivity is not identical to the hydrophobic strength of the column and depends on the structure and polarity of the homologous series used for calculation. Polar selectivity for different types of compounds depends on the propensity of the stationary phase to enter into polar (mainly hydrogen-bond donor and hydrogen-bond acceptor) interactions with the compounds investigated. (C) 1998 Elsevier Science B.V. All rights reserved.