title: Radiation immobilization of poly(methyloctylsiloxane) on silica for use in HPLC: a uniform layer model.
abstract: Poly(methyloctylsiloxane) (PMOS) was sorbed into the pores of HPLC silica by a solvent evaporation procedure, then irradiated with gamma rays from a cobalt-60 source to absorbed doses in the range from 0 to 200 kGy (1Gy = 1J kg-1). Non-irradiated and irradiated samples were characterized by solvent extraction, specific surface area determination, infrared spectroscopy and reversed-phase column performance. Solvent extraction data reveal that about 40% of the PMOS is not extractable prior to irradiation and this increases to about 75% with radiation doses of 50 kGy or higher. Column performance was improved by the radiation treatment, reaching a maximum efficiency in the dose range of 80-140 kGy while the peak symmetry changed from As = 1.7 to 1.1. The improvement is attributed to the increased mass of polymer immobilized by the radiation treatment and to a more uniform distribution of the immobilized polymer in the silica pore system. A multi-layer stationary-phase model is presented in which the first layer consists of an adsorbed monolayer of PMOS and the second layer is immobilized by gamma radiation.
authors.affiliation: Instituto de Química, Universidade Estadual de Campinas-UNICAMP, SP, Brazil. icsfj@iqm.unicamp.br
authors.forename: I C
authors.initials: IC
authors.lastname: Jardim
authors.forename: K E
authors.initials: KE
authors.lastname: Collins
authors.forename: T A
authors.initials: TA
authors.lastname: Anazawa
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005720:Gamma Rays; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry; D011827:Radiation; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry* / Q000528:radiation effects; D012833:Siloxanes / Q000737:chemistry / Q000528:radiation effects
chemical_list: D012833:Siloxanes; D058428:Silica Gel; D012822:Silicon Dioxide; D010100:Oxygen