Biphenylpropyl Modified Silica: An Interesting Choice for RP Chromatography

摘要

Alkyl especially octadecyl modified silicas are the workhorses in modern RP chromatography. Their retention mechanism is mainly due to hydrophobic van der Waals interactions. Steric or polar interactions tend to play a minor role. However, some separations are difficult or impossible to achieve with these stationary phases. Therefore, surface modifications with orthogonal selectivity are of great interest. Sorbents for reversed-phase chromatography must have sufficient hydrophobicity and they have to be chemically inert. These restrictions exclude many functionalities. However, aryl ligands as hydrocarbons are hydrophobic and chemically inert [1 ]. Their ability to undergo jt-jt interactions affects their selectivity over conventional alkyl phases [2,3]. Silicas modified with phenylpropyl or phenylhexyl silanes show lower hydrophobic interactions and thus shorter retention times compared to octadexyl modified silica. To increase the hydrophobicity of aryl modified silicas biphenylpropyl ligands have been chosen for surface modification. As expected this stationary phase shows enlarged retention times and different selectivities compared to octadecyl phases. They seem to be an interesting alternative to conventional alkyl modified silicas.