The general chemically bonded phase uses silica gel as a carrier, which has a partitioning effect and a certain adsorption effect. The size of the adsorption depends on the bonding coverage.
The residual silanol groups on the surface of the support are removed by chemical reaction, which is called end capping, capping or covering. The bonded phase formed is called a tail-type bonded phase. The fully encapsulated bonded phase has no adsorption, but strong hydrophobicity is a disadvantage.
The silica-bonded phase is classified into Si-O-C and Si-O-C (siloxane) type according to the type of chemical bond in which the functional group is combined with the carrier. The Si-O-C type bonded phase is damaged due to hydrolysis and has been eliminated. At present, silicone-type bonded phases are often used, and they can be classified into non-polar, medium-polar and polar types according to their polarities.
The octadecyl bonded phase is the most commonly used non-polar bonded phase. The octadecyl chlorosilane reagent and the silanol group on the surface of the silica gel are subjected to a multi-step reaction to produce an ODS bonded phase. Adsorption or partitioning depends on the ODS bonded phase coverage.
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