Titanized silicas, modified by C18, as promising stationary phases for high pH separations

To enhance the high pH stability of silica based reversed phases, chemically bonded octadecyl phases were prepared through silanization of titanized silica particles containing approximately 14% titanium oxide on the surface. The present work describes some spectroscopic characterizations using infrared, solid-state 13C and 29Si nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy (XAS). Chromatographic characterizations for the titanized phase as well as for a conventional C18 phase, based on the same silica support without titanization, are also described using three different test mixtures containing neutral, polar and basic compounds. After an artificial stability test at pH 10, the titanized phase was again characterized by elemental and X-ray fluorescence analyses to determine the remaining carbon and titanium contents. As an application to real world samples, the separation of some herbicides and highly basic drugs using buffered mobile phases are also shown.