Preparation Of Silica-Based Monolithic Stationary Phases And Their Applications

Recently, monolithic columns consisting of one piece of organic polymer and silica with flow through pores emerged as an attractive alternative to conventional columns packed with particles because of their better stability and, more importantly, higher performance. Monolithic silica rods are porous monoliths consisting of a silica skeleton with bimodal pore structures. The through-pores are responsible for the high permeability of the monolith while the mesopores, are necessary for high maximum sample loadability.Preparation of silica monolithic capillary columns based on hydrolysis and polymerization of sol-gel precursors has been attempted. The incorporation of urea into the polymerization mixture simplified the preparation procedures, however, it incurred the complicated reaction. The strategy with flushing the wet gel with aqueous urea solution and thereby generating alkaline solution for tailoring the mesopores of monolith seems to be a better one, for it promised to produce highly homogeneous monolithic silica structure with better performance.The native silica monolith has been successfully employed in the high-performance electrochromatographic separation ofβ-blockers and alkaloids extracted from traditional Chinese medicines (TCMs). Retention mechanisms including cation exchange, reversed-phase and normal-phase mechanisms are also discussed.