Group IV metal oxide monolithic materials: Synthesis and applications
Rivera, Jose Gil
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Monoliths are a new generation of chromatographic media with very attractive chromatographic characteristics. Monolithic columns reduce the pressure requirements to drive the mobile phase through the column, leading to the use of higher than usual mobile phase velocities while maintaining chromatographic performance. Using sol-gel processing, we have synthesized a new type of monolithic structures with potential applications in HPLC column technology. The monolithic materials are based on zirconium and hafnium oxides (i.e., zirconia and hafnia). These materials provide excellent chemical and physical stability, compared to chromatographic materials based on organic polymers and/or silica. The work presented in this dissertation includes the synthetic approach to obtaining hafnia and zirconia monolithic materials, the evaluation of their physical characteristics such as surface area, porosity and crystallinity, along with initial studies on the development of hafnia and zirconia monolithic columns for chromatographic applications. Group IV metal oxides (e.g. titania, zirconia) have exhibited great applicability for the preconcentration of phosphorylated peptides in the proteomics field. Such materials have provided improved phosphopeptide enrichment capabilities as compared to more conventional technology. The usefulness of hafnia as an enrichment material for phosphorylated compounds, had not been explored until this work. Hafnia materials were tested for the enrichment and preconcentration of phosphorylated peptides, prior to mass spectrometry analyses. The findings indicate that hafnia is a suitable adsorbent material for the isolation/enrichment of phosphorylated compounds, complementing titania and zirconia materials. HPLC and capillary electrophoresis (CE) studies have been for performed for the analysis of surfactant protein B in lung surfactant mixtures. SP-B is a highly hydrophobic protein that is indispensable for optimal functioning in the lung. Gradient elution chromatography in the reverse phase mode, coupled to charged aerosol detection provided to be a suitable separation and detection system for the analysis of SP-B in calf lung surfactant extract (CLSE) and the therapeutic drug Infasurf. CE conditions have been identified for the analysis of SP-B in calf lung surfactant extract. Background electrolyte additives such as sodium dodecyl sulphate and/or acetonitrile were found to be necessary in the separation of SP-B from CLSE. These preliminary investigations should set a starting point for the assessment of SP-B in pulmonary surfactants.