Selectivity equivalence of poly(ethylene glycol) stationary phases for gaschromatography

The solvation parameter model is used to study differences in selectivity f or poly(ethylene glycol) stationary phases for packed column (Carbowax 20M) and fused-silica, open-tubular column (HP-20M, AT-Wax, HP-INNOWax and DB-F FAP) gas chromatography. All phases are dipolar, strongly hydrogen-bond bas ic with no hydrogen-bond acidity and of moderate cohesion. No two phases ar e exactly alike, however, and selectivity differences identified with cavit y formation and dispersion interactions, n- and pi -electron pair interacti ons, dipole-type interactions and hydrogen-bond interactions are quantified by differences in the system constants at a fixed temperature where retent ion occurs solely by gas-liquid partitioning. The system constants vary lin early with temperature over the range 60-140 degreesC (except for n- and pi -electron pair interactions which are temperature invariant) facilitating a general comparison of the importance of temperature on selectivity differ ences for compared phases. From a mechanistic point of view it is demonstra ted that selectivity differences can result from chemical differences betwe en the poly(ethylene glycol) stationary phases and from differences in the relative contribution of interfacial adsorption to the retention mechanism. The latter depends on both system properties and solute characteristics. ( C) 2000 Elsevier Science B.V. All rights reserved.