Photopolymerized organo-silica hybrid monolithic columns: characterization of their performance in capillary liquid...

Porous hybrid organo-silica monoliths have been prepared inside pretreated 100 μm id UV transparent fused-silica capillaries using simultaneous sol-gel transition and polymerization of 3-(methacryloyloxy)propyl trimethoxysilane in the presence of toluene as a porogen. The sol-gel reaction was catalyzed by hydrochloric acid while various photoinitiators including azobisisobutyronitrile, 2,2-dimethoxy-2-phenylacetophenone, and Irgacure 819 were used for the photopolymerization carried out under irradiation with UV light at a wavelength of 254 or 365 nm. The chromatographic performance of photopolymerized monolithic columns in RP liquid chromatographic mode was assessed with respect to the following metrics: column efficiency, methylene and steric selectivity, effect of silanol groups, van Deemter plot, permeability, and pore size distribution. Columns with an efficiency of up to 77 000 plates/m for benzene has been achieved at a flow velocity of 0.47 mm/s. The performance of photopolymerized hybrid monolithic column was compared to the performance of columns prepared via thermally initiated polymerization.