Chemical modification of silica-based packing materials for high-performance liquid chromatography

Silica gel is the most widely used as a packing material for HPLC. It posse sses the advantages of high mechanical strength, a large number of theoreti cal plates, ease of chemical modification of the surface and availability; at a relatively low price. The demand for further improvements in the perfo rmance of silica-based packing materials has been increasing. In this study , improvements of reversed phase packing materials, restricted access media (RAM) and child stationary phases were achieved through the development of new methods for silica surface modification. Art end-capping method using high-temperature silylation was developed, which produced octadecylsilylate d silica gel (ODS) without and undesirable effects of residual silanol grou ps. In a study on RAM, glycerylalkylsilylated silica gels with alkyl moiety ranging from C-3 to C-6 were prepared as a new type of RAM. These packing materials did not adsorb proteins, but could retain small molecules, such a s drugs, in direct injection analysis of serum samples. This is one of the simplest methods for preparing RAM. In the addition, a low-temperature plas ma treatment was applied to the preparation of RAM. The plasma more easily removed octadecyl groups on the external surface of ODS; to produce silanol groups than those on the internal surface. The silanol groups were glycery lpropylsilylated to produce RAM. Furthermore, some novel chiral stationary phases were prepared by covalently bonding chiral binaphthol and its deriva tives to silica gels. These stationary phases showed enantioselectivity mai nly basic compounds. The hydroxyl groups of binaphthol played a dominant ro le in chiral recognition and retention.