Surface Modification On Hybrid Monolithic Column For Capillary Electrochromatrography Based On Thiol-ene Click Chemistry

Monolithic column technology has been widely for micro-separation field used in proteomics, metabolomics and medicinal botany, due to its excellent separation efficiency and efficient mass transfer performance. Monolithic column can be mainly classified into silica-based monolithic column and organic monolithic column. Silica-based monolithic column has a stable column bed, but poor in selectivity of monolith types due the limitation of silane. On the contrary, organic column is easy swell by the solvent. Thus, it is compulsary to improve the technology of preparing monolithic column. Recently, organic-inorganic hybrid monolithic column (such as the VTMS monolithic column, y-MAPS monolithic column and MPTS monolithic column) has been emerged to solve the problem. However, click chemistry is seldom reported for surface modification of monolithic column. Based on the situation mentioned above, we focus on the surface modification of organic-inorganic monolithic column using thiol-ene click chemistry.The main work of this thesis is summarized as follows:1. An n-octadecanethiol (C]8)/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 tested and1:3was found to be optimal. The resulting C18-MPS-VTMS silica hybrid monolithic column can be used in different separation modes, including reversed phase mode and ion exchange mode.2. In order to improve the reactivity of the vinyl linkage on monolith surface, we tried to replace the silane reagent as precursor. Compared to the VTMS silica hybrid monolithic column, the y-MAPS silica hybrid monolithic column has a higher reactivity vinyl linkage on the surface of monolith. Thus it is easier to connect vinyl bond with other sulfhydryl-containing compounds through thiol-ene click chemistry under milder conditions. So we developed a y-MAPS silica hybrid monolithic column, and decorated the monolith surface with cysteamine based on thiol-ene click chemistry. The results show that the y-MAPS silica hybrid monolithic column has a lower temperature of deriviation than VTMS silica hybrid monolithic column, and the prepared monolithic column can give a baseline separation of the organic acids.3. We achieved surface modification of hybrid silica monolithic column based on thiol-ene click chemistry. Using MPTS and TMOS as precursor we prepared a MPTS silica hybrid monolith column with thiol on the monolith surface. Then the MODAB, which has a longer carbon chain, was derivated to the surface of monolithic column using the thiol-ene click reaction. The CEC results showed that the prepared MODAB-MPTS hybrid monolithic column demonstrated a reverse phase chromatography, which means that the long carbon chain is modificated on the monolith surface successfully.