Poly(alkylmethylsiloxanes) thermally immobilized on silica as stationary phases for high-performance liquid chromatography

Poly(methyloctylsiloxane) (PMOS) and poly(methyloctadecylsiloxane) (PMODS) were sorbed onto porous HPLC silica and thermally immobilized, in the absence of radical initiators, at temperatures in the range of 80 to 180°C. Following extraction of non-immobilized polymer the materials were packed into columns and their chromatographic properties evaluated. The shorter chain (PMOS) stationary phase showed good HPLC characteristics after thermal immobilizations up to 120°C while the longer chain (PMODS) phase gave satisfactory HPLC phases following thermal immobilizations at 80 and 100°C. Stability evaluation for the PMOS and PMODS columns immobilized at 100°C required 250 ml of pH 8.5 mobile phase at 60°C to significantly decrease efficiency, suggesting a long useful life time at neutral pH and ambient temperature.