Modification of VTMS hybrid monolith via thiol-ene click chemistry for capillary electrochromatography

An n-octadecanethiol (C18)/3-mercapto-1-propane-sulfonate (MPS) modified organic–inorganic hybrid silica monolithic column possessing vinyl ligands through thiol-ene click chemistry for capillary electrochromatography (CEC) is described. The proposed column is prepared via the sol–gel process by in situ co-condensation using vinyltrimethoxysilane (VTMS) and tetra-methoxysilane (TMOS) as precursors. Examination by SEM shows that the capillary has homogenous macroporous morphology and is well attached to the inner wall of the capillary. The obtained C18-MPS-VTMS silica hybrid monolithic column demonstrated an enhanced hydrophilic property and could be applied as a reversed-phase stationary phase in CEC directly. Compared with unmodified VTMS silica hybrid monolithic column, stronger EOF was observed using this monolithic column. VTMS/TOMS ratios in the reaction mixture were varied and 1:3 was found to be optimum. Good separations of benzenes, aromatic amines, acids and peptides were achieved, the lowest plate height of ∼3 μm was obtained, the peak symmetry range from 0.98 to 1.29. The resulting C18-MPS-VTMS silica hybrid monolithic column can be used in different separation modes, including reversed phase mode and ion exchange mode.