In-column preparation of a brush-type chiral stationary phase using click chemistry and a silica monolith

Brush-type chiral stationary phases (CSP) have been prepared both from a silica monolith and, separately, from 10 μm porous silica beads via a process of in-column modification including attachment of the chiral selector via copper-catalyzed azide-alkyne cycloaddition. Azide functionalities were first introduced on the pore surface of each type of support by reaction with 3-(azidopropyl)trimethoxysilane, followed by immobilization of a proline-derived chiral selector containing an alkyne moiety. This functionalization reaction was carried out in dimethylformamide (DMF) in the presence of catalytic amounts of copper (I) iodide. The separation performance of these triazole linked stationary phases was demonstrated in enantioseparations of four model analytes, which afforded separation factors as high as 11.4.