Key WordsColumn liquid chromatography Silica bonded phases Solvatochromic characterization Hydrogen bond acidity and basicity Dipolarity Summary UV-visible reflectance spectra of solvatochromic dyes and mobile phases with compositions in the ranges from 100 to 5 % (v/v) acetonitrile and methanol in water have been used to characterize octadecyl-, octyl-, phenyl-, cyano-, amino-, and diol-bonded silica stationary phases. Dipolarity/polarizability (re*), hydrogen-bond (HB) donor acidity (c0, and HB acceptor basicity (fi) of the stationary phases were determined in the mobile phases. Interaction properties of the stationary phases are affected both by the types of bonded moiety and by the composition of the mobile phase.

Column liquid chromatography Interaction of mobile and stationary phases Linear solvation energy relationships Triethylamine SummaryThe effect of triethylamine (TEA) in the mobile phase on the RPLC retention behavior of small organic solutes has been studied on a conventional polymeric octadecylsilica (ODS) and on a horizontally polymerized ODS. Retention factors for a set of solutes were measured on the two phases with methanol-water mobile phases containing triethylamine at different concentrations and analyzed by use of linear solvation energy relationships (LSER). Variation of the resulting LSER coefficients -v (hydrophobicity), r (polarizability), s (dipolarity), b (hydrogen-bond (HB) donating acidity), and a (HB accepting strength) -were examined to see how TEA affects the intermolecular interaction properties of the mobile and stationary phases and hence the retention of the solutes. Addition of TEA to the mobile phase changes the interaction properties of both conventionally polymerized and horizontally polymerized ODS; the effect is greater for the conventional phase. The HB donating acidity (b) of conventional polymeric ODS is significantly reduced by addition of TEA. For the mobile phases studied the magnitudes of the b and v coefficients for the horizontally polymerized ODS phase are greater than for the conventional phase. The different interaction properties of the two polymeric phases arise mainly as a result of differential adsorption of TEA, because of the very different amounts of surface silanol groups present on the two phases.