Octyl-functionalized hybrid silica monolithic column for reversed-phase capillary electrochromatography

Hybrid silica monolithic stationary phase functionalized with octyl groups was synthesized by a two-step acid/base-catalyzed hydrolysis/co-condensation of tetraethoxysilane (TEOS) and n-octyltriethoxysilane (C8-TEOS). The influences of determining factors in the sol–gel process such as the monomer ratio and water content on the monolith formation were systematically investigated. An increase in the TEOS/C8-TEOS ratio in the polymerization mixture shifted the pore size distribution towards smaller pore diameter with larger pore volume. The optimal TEOS/C8-TEOS volume ratio was found to be 90/50, under which condition the median pore diameter of the monolith was around 1.0 μm with pore volume of 3.25 cm3/g. The chromatographic characteristics of the monolithic column prepared with the optimized fabrication condition were studied. Some aromatic compounds including alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs) and phenols were successfully separated on the octyl-functionalized silica monolithic column with high column efficiency up to 180,000 plates/m.