| Chromatographic column is known as the core of the high performance liquid chromatography system. The availability of a variety of stationary phases for column has been a key factor in the development of HPLC as a major scientific tool. With the most desirable compromise of properties that provide for effective and reproducible separations, silica has been the most widely used HPLC packing material. It can be used in different separation modes, such as reversed-phase, normal-phase, ion chromatography, etc. Silica made by different methods vary widely in both physical and chemical characteristics and chromatographic properties, so research on preparation of monodisperse silica has been significant to establishment and development of HPLC methods. The purpose of this study was to study the preparation methods of silica and research the properties of silica prepared by different methods.In this paper, silica microparticles were synthesized by various methods, including one-step sol-gel method, two-step sol-gel method, templating method, polymerization induced colloid aggregation method, as well as sol-gel coupled with polymerization induced colloid aggregation method. The effects of reaction conditions on physical parameters and chromatographic characteristics of silica particles were discussed in detail. Also, a gel permeation chromatography method and an ion chromatography method were established to monitor the preparation process of silica particles.Silica particles prepared by one-step sol-gel via seed particle growth method were monodisperse and nonporous, with good mechanical strength. Mesoporous silica particles with a narrow pore size were prepared by two-step catalytic sol-gel method. Results showed that silica particles were mostly regular-ball and no particle agglomeration, but particle size distribution width relatively higher than commodity silica particles. Result of normal-phase chromatography showed that the standard substances could be separated on this silica. Using triblock copolymer Pluronic P123as template,1,3,5-trimethylbenzene as cosurfactant, mesoporous SBA-15silica particles were synthesized by templating method. With good permeability, this mesoporous silica might be used to separate protein, polypeptide, and so on.Mesoporous silica particles with good monodispersity were prepared by PICA method. The result of normal-phase chromatography showed that the standard substances were separated very well. Also, C18bonded silica stationary phase with good chromatographic performance was synthesized. This phase was used for successful separation of amino acids mixture, and so on. Because of high content of total metal in commodity silica gel, metal at the surface of silica bonded phase caused tailing chromatographic peaks for chelating reagents. Therefore, a new sol-gel coupled with PICA method was developed to produce high purity porous silica microspheres. Nanometer-sized silica gel was produced by sol-gel process, and then micrometer silica particles were synthesized by PICA reaction. As total metal content in microspheres prepared from this method was extremely low, tailing chromatographic peaks for chelating reagents was eliminated.A GPC method was established for the determination of molecular weight of TES40and the intermediate product PES during silica microspheres synthesis process by a two-step catalytic sol-gel method. The molecular weight distribution of TES40and PES could be monitored by GPC during silica microspheres preparation process, so that reproducibility of preparation process could be realized more easily with control of PES molecular weight. An IC method was established for the determination of metal cations in raw materials and silica particles synthesized by PICA method and sol-gel coupled with PICA method. The sources of metal could be monitored by IC during silica particles preparation process, so that synthesis of high purity silica particles could be realized more facilely with control of metal content. |
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