The Cogent Phenyl Hydride phase is a 4 carbon chain with a phenyl group at the end attached directly to the silica hydride surface with a single, direct silicon-carbon bond.

With bonds in traditional silica B based materials, the organo-silane starting material is Si-O-Si-C4-Phenyl and this reagent is reacted with the silica to form the final stationary phase which includes a Si-O-Si-C4-Phenyl ligand.

This is in contrast with the TYPE-C phases in that the Si-C bond is formed directly as part of the reaction resulting in Si-C4-Phenyl without the oxygen in the link which is very susceptible to hydrolysis.

More information on Phenyl Hydride HPLC Columns