Silica packing materials, represented by octadecylsilyl (ODS-) silica and octylsilyl silica, have numerous features such as excellent pressure resistance and solvent resistance, high separation performance, wide sample range, and low column cost.
However, with the progress in studies of proteins, peptides, and other components and the research of pharmaceutical metabolism accompanying the recent development of biotechnology, several problems have surfaced, such as peak tailing and recovery deterioration due to the irreversible adsorption of components, especially basic compounds.
After ODS bonding, non-reacted silanol groups (Si-OH) are generally processed (end capped) using a trimethylsilyl agent to resolve the adsorption problem and improve durability. Even after the end capping process, however, it is known that C18 groups are hydolyzed in basic environments, and that silica itself dissolved into basic liquid. Therefore, conventional ODS columns' mobile phase were limited to acidic or neutral.
Meanwhile, porous-polymer packing material features a wide pH range and high sample loadability but it has the disadvantage of low separation efficiency, low pressure resistance, and limitation for organic content because of polymer's inherent swelling and contracting nature, and the column cost is high. Polymer gels are now being developed to improve the pressure resistance and to reduce the swelling and contraction rate by raising the degree of crosslinking.
Under these circumstances, Shiseido developed a silica packing material with basic resistance and improved durability as well as excellent pressure resistance, chemical stability, and separation performance over conventional ODS silica.
By applying surface treatment technology that is cultivated in the research of powdery materials used for cosmetics, Shiseido successfully developed a novel polymer-coated packing material (capsule) in 1985 (received the Chemical Technology Award from the Chemical Society of Japan).
This technology features:
(1) Polymer coating of a uniform thickness along the pores of silica
(2) Accurate control of the film thickness
(3) Excellent chemical stability by polymer coating
(4) Stable chemical bonding of a silicone polymer layer with C18 or C8