ΔR _M as the Parameter Characterizing Chromatographic Properties of Polar Bonded Stationary Phases in Isoeluotropic Systems

Abstract

Eluent strengths of binary eluents consisting of nonpolar diluent (nheptane) and polar modifiers from various selectivity groups were used to obtain comparable eluent strengths in relation to monofunctional solutes: phenol, aniline, and quinoline on the layers of polar bonded stationary phases. In such optimised isoeluotropic eluents, retention factors of para-substitued phenols, aromatic amines, and some quinolines (with omitted 8-and 2-derivatives to eliminate effect ortho-) were measured chromatographically using plates precoated with NH 2 -silica, diol-silica, and CN-silica. Differences in eluent strengths of polar modifiers (2-propanol, ethyl acetate, dioxane, tetrahydrofuran, acetone, methyl ORDER REPRINTS ethyl ketone, dichloromethane, and diisopropyl ether) depend on the electron-donor character of solute and type of stationary phase. Selectivity of separation was analysed by DR M values and by R M spectra. For the separation of phenols and aromatic amines, the most selective were aminopropyl phases for quinolines and cyanopropyl phases. Chromatographic properties of polar bonded stationary phases were analysed by means of DR M I vs. DR M II correlations.