Studies of retention and stability of a horizontally polymerized bonded phase for reversed-phase liquid chromatography

We have studied the novel horizontally polymerized mixed trichloropropyl–trichlorooctadecyl silane bonded phase described by Wirth. These materials can be reproducibly prepared and give very high bonded phase density (>7.5 μmol m−2). They show significantly improved alkaline stability and chromatographic selectivity towards PAHs similar to conventional monomeric phases. Study of retention by the Linear Solvation Energy Relationship approach as well as measurement of dead volume and retention of methanol indicate that less mobile phase is sorbed by a horizontally polymerized phase than by conventional phases. Silanophilic interaction of amines are decidedly weaker on a silica modified by horizontal polymerization compared to a conventionally modified phase. In addition, this work provides additional support for the “partition-like” retention mechanism of bonded phase RPLC.