Investigations of a sol-gel derived stationary phase for open tubular capillary electrochromatography

Organic-inorganic hybrid glass composites were synthesized using sol-gel processing. These composites were cast onto the inner walls of fused silica capillaries and used as the stationary phase for open tubular capillary electrochromatography (OT-CEC). N-octyl sol-gel processed bonded phases were prepared using a mixture of n-octyltriethoxysilane and tetraethoxysilane (C₈-TEOS/TEOS). The synthesis of the sol-gel-processed composite incorporates the stationary phase into the glass formation process. This process consists of hydrolysis and condensation reactions of the C₈-TEOS/TEOS mixture. The chemical species present in solution during the sol-gel process, prior to column casting, dictates the characteristics of the final glass composite. Manipulation of the processing parameters allows control of the retentive properties of the sol-gel-derived phase. A correlation between the species present in solution at the time of column casting and chromatographic retention has been established. The column preparation procedure was optimized for the C₈-TEOS/TEOS hybrid system. A phase containing octadecyl (C₁₈) groups was also fabricated by sol-gel processing. Using a pressurized coating assembly improved the column-to-column reproducibility. The effect of silanizing the sol-gel-derived material was also studied. Such a silanization, however, did not cause appreciable changes on the performance of the capillary columns. Copyright (C) 1999 Elsevier Science B.V.