Silica Based Stationary Phases for High Performance Liquid Chromatography

High performance liquid chromatography is not only a useful analytical technique, hut also an effective preparation method. 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. The silica microspheres are synthesized by various methods, including spray drying, sol-gel, polymerization induced colloid aggregation and templating methods. In recent years, atypical types of silica are prepared and applied in HPLC, such as sub-2 mu m silica particles, superficially porous silica particles, bimodal silica particles, mesoporous silica particles, organic/silica hybrid particles, etc. As a result, unique separation properties that enlarge the capabilities of HPLC methods have been achieved, such as ultrahigh-pressure liquid chromatography based on sub-2 mu m silica particles, fast liquid chromatography based on superficially porous silica particles, high temperature liquid chromatography based on organic/silica hybrid particles. Moreover, novel stationary phase can be obtained by chemical bonding or polymer modification of silica surface, such as chiral stationary phase, temperature-responsive stationary phase and restricted access materials. In this paper, the preparation methods and modification modes of silica particles are introduced, as well as the characterization methods of HPLC stationary phase. The applications of silica packing material in HPLC and its developing trends are also outlined.