Characterization of silica-based octyl phases of different bonding density - Part I. Thermal stability studies

Chemically bonded phases for reversed-phase chromatography are often produced via reaction of silica gel with appropriate organosilane. Although this reaction is commonly used and well-documented in literature, little attention has been paid so far to study the postreaction curing process. In the current paper the effect of the curing process on the thermal stability of the synthesized octyl phases has been investigated by means of thermogravimetry and solid-state NMR techniques. The study shows that the postreaction isothermal equilibration of the samples dramatically improves their thermal stability without a substantial mass loss due to thermodesorption of silane. Curing process promotes condensation reaction of surface hydroxyls with hydrolyzed silane molecules increasing surface coverage of the synthesized chemically bonded phases. (C) 1998 Elsevier Science B.V. All rights reserved.