Preparation And Evaluation Of Novel Organic-silica Hybrid Capillary Monoliths

Organic-silica hybrid monoliths have attracted great attention in recent years. Various merits of organic polymer monoliths and silica monoliths, including ease of preparation, good pH stability, good mechanical stability has been well involved in the silica hybrid monolith, and thus the drawbacks of the two above mentioned types are avoided effectively. Developing novel organic-silica hybrid monoliths has been an important direction in the field of monolithic columns.In this thesis, the key topic is about the prepration and evaluation of novel organic-silica hybrid monolithic columns. The main points are listed as following:In chapter 1, the basic theory of CEC and different kinds of capillary monolithic columns were introduced. The development of organic-silica hybrid monolithic columns was also presented, and thus the aim and experimental scheme of this thesis were put forward briefly.In chapter 2, a chloropropyl-functionalized organic-silica (CP-silica) hybrid monolith was prepared with sol-gel method by using tetramethoxysilane (TMOS) and (3-chloropropyl)-trimethoxysilane (CPTMS) as mixed precursors. Effects of PEG and urea on the sol-gel reaction and the interaction mechanism were discussed in detail. The influence of different contents of PEG and urea on the struction, pore size distribution, permeability and mechanical strength of the hybrid monolithic column was investigated. The mechanical stability, reproducibility and chromatographic retention mechanism of CP-silica hybrid monolithic column were also studied. Satisfactory characteristics including good mechanical stability, acceptable resistance to swelling was realized in the obtained CP-silica hybrid monolith, and hydrophobicity interaction and weak ion exchange mixed-mode mechanism was observed. Benzene, aniline compounds and benzoic acid derivatives were successfully separated on the CP-silica hybrid monolithic column.In chapter 3, by bonding quinine containing nitrogen heterocycles onto the CP-silica hybrid monolith by post-column derivatization, a novel immobilized quaternary ammonium type quinine functionalized hybrid monolithic column was formed. The derivatization condition of quinine was optimized, and the factors such as EOF, mechanical stability and reproducibility were investigated. In addition, pyridine and 6-methoxyquinoline were used to discuss the binding site and reaction mechanism of quinine with CP-silica monolith. Chromatographic performance of quinine functionalized hybrid monolithic column was studied and the results showed that multiple interactions including reversed phase retention, anion-exchange and π-π interactions were presented. An excellent separation of neutral and acidic pesticides, neutral environmental estrogens (EEs) and alkaline nicotinic compounds was achieved respectively by multiple separations in mixed-mode.