Silica Hydride Surfaces: Versatile Separation Media for Chromatographic and Electrophoretic Analyses

Abstract

Silica hydride, where Si‐H groups replace 95% of the silanols on the surface, is rapidly being developed as a chromatographic support material for HPLC. This chemical structure results in changes of fundamental properties compared to ordinary silica, as well as the bonded stationary phases produced by the further modification of the hydride surface. Several unique chromatographic capabilities of hydride based phases are described, as well as some general application areas where these bonded materials may be used in preference to, or have advantages not available from current commercial stationary phases. The fabrication, properties and applications of etched chemically modified capillaries for electrophoretic analysis are also reviewed. The etching process creates a surface that is fundamentally different in comparison to a bare fused silica capillary. The new surface matrix produces altered electroosmotic flow properties and is more compatible with basic and biological compounds. After chemical modification of the surface, the bonded organic moiety (stationary phase) contributes to the control of migration of solutes in the capillary. Both electrophoretic and chromatographic processes take place in the etched, chemically modified capillaries leading to a variety of experimental variables that can be used to optimize separations. Representative examples of separations on these capillaries are described.

Keywords:

• Silanization/hydrosilation
• Aqueous normal phase
• Etched capillaries

Acknowledgments

The financial support of the National Institutes of Health (NIH MBRS Grant 0819210‐21) and the National Science Foundation (CHE 0094983) is gratefully acknowledged. One of the authors (JJP) would like to acknowledge the support of the Camille and Henry Dreyfus Foundation through a Scholar Award.