The primary objective of the proposed project is to advance the capabilities of modern chromatographic methods through an enhanced understanding of silylated stationary phase surface structure and the subsequent development of improved bonded phase materials. Advances in biomedical research are closely tied to the selectivity and sensitivity limitations of chromatographic methods because of the chemical complexity of biological matrices and the necessity for sample separation prior to analysis. Developing support materials with improved chromatographic performance requires a clear understanding of stationary phase surface structure and the existence of problematic surface species. The research described in this proposal will ultimately contribute to the understanding of unmodified and silylated silica surface structure which will facilitate future advances in the performance of bonded phase supports. Specific goals of the research will be; 1) to study the effects of thermal treatment on porous silica gels having variable pore diameter, 2) to study the extent of surface silylation and how it is affected by different reagents (alkoxy, chloro, and organoaminosilanes), pore diameter, silane alkyl chain length, amine catalysts, surface adsorbed water, etc., and 3) to comparatively study the kinetics of the silylation reaction using silane reagents in both solution and gaseous phases. Characterization of the modified surfaces will be accomplished using variable-temperature diffuse reflectance FTIR spectroscopy (VT- DRIFTS) in conjunction with a heatable-evacuable sample chamber. Analysis by DRIFTS will insure that surface species are intact and unaltered by the sample preparation procedure. Use of the sample chamber will allow for in-situ environmentally controlled studies whereby probe molecules can interact with surface sites. Characterization studies will elucidate the structural nature and surface concentration of attached silanes, as well as the structural nature, concentration and relative acidity of surface silanol (SiOH) species.
