Abstract
The solvation parameter model is used to characterize the solvent properties of 12 poly(siloxane) stationary phases of varied structure. Selectivity differences are explained in terms of differences in the cohesive energy of the solvents and their capacity for dispersion, dipole‐type, hydrogen bonding, and electron pair complexation interactions. None of the poly(siloxane) stationary phases exhibited significant hydrogen‐bond acid character. Principal component analysis indicates that replacing a methyl group by a phenyl group in the poly(siloxane) backbone predominantly produces incremental increases in the capacity of the stationary phase for dipole‐type interactions (up to about 50 mol% phenyl groups with only small changes at higher phenyl composition). The poly(methylphenylsiloxanes), however, only span a small sector of the selectivity space and provide limited opportunities for selectivity optimization. OV—275 and QF‐1 are identified as important phases with unique characteristics—OV‐275 because of its high cohesive energy and great capacity for dipole‐type and solvent hydrogen‐bond base interactions and QF‐1 because of its unusually small hydrogen‐bond basicity for a phase with an intermediate capacity for dipole‐type interactions as well as a low capacity for n‐ and π‐electron complexation interactions. From these studies it is possible to speculate on the needs for new phases to explore the full selectivity potential of gas chromatography and to address the issue of temperature and its relationship to selectivity. © 1995 John Wiley & Sons, Inc.