In high performance liquid chromatography (HPLC), monolithic columns allow for the use of higher flow rates and resulting faster analysis due to the highly porous nature of the stationary phase. Hybrid monoliths possess a unique combination of both inorganic and organic functionalities on the pore surface. In this study, thermally-polymerized organo-silica parent monoliths were modified using thiolene click chemistry with the purpose of increasing surface hydrophobicity. Initially, the parent monoliths were prepared by polymerization of a monomer, 3-(trimethoxysilyl)propyl methacrylate (MPTMS), an aqueous hydrochloric acid catalyst, an initiator azobisisobutyronitrile (AIBN), and porogen, toluene directly inside of a 100 �.m. I.D. UV-transparent fused silica capillaries at 80 �C. Subsequent was the on-column reaction of 1-octadecanethiol dissolved in toluene with exposed and easily accessible methacrylate functional groups at 80 �C on the pore surface of the organo-silica hybrid monolith. The reaction time was varied from 3 to 24 hours. The retention of benzene was used to monitor the changes in the surface hydrophobicity. The retention factor was calculated using retention time of benzene and unretained marker (thiourea). The mixture containing both analytes was separated under isocratic conditions using a mobile phase of 50% aqueous acetonitrile at a flow rate of 0.5 �L/min. The trend of an increased retention factor with extended reaction time has been observed until steady value was achieved. This proves successful pore surface modification and suggests the resulting application towards better retention of nonpolar analytes in reversed-phase chromatography.

Pore surface modification of organo-silica hybrid monolithic columns through thiolene chemistry for application in micro-flow liquid chromatography

247th National Meeting (2014)

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