Characterization and stability of silanized and polymercoated octadecyl reversed phases

Three different reversed phases for high-performance liquid chromatography obtained with monofunctional octadecylsilane or with cross-linked polymethyloctadecylsiloxane with and without trimethylsilane precapping of the substrate were synthesized on the same batch of Nucleosil silica. After extensive characterization, these phases were subjected to artificial ageing under simulated routine conditions. Changes in properties of the bonded-phase packings were quantified with chromatographic techniques, solid-state 29Si NMR and elemental analysis. These changes are correlated with lipophilic and polar selectivity, accessibility of silanol groups at the surface, loss of silanes/siloxanes, separation performance and silica degradation of the stationary phases