The synthesis of a new perfluorinated stationary phase based on silica hydride using a hydrosilation reaction was investigated. The material was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy and (13) C cross-polarization magic-angle spinning NMR spectroscopy. The retention properties of this new material were tested in the reversed-phase and normal-phase mode. Variable buffer strength experiments at two pH conditions for selected polar compounds were used to compare the new phase to hydrophilic interaction liquid chromatography retention. These results and previous data reported in the literature were used to postulate differences in the retention mechanism between hydrophilic interaction liquid chromatography and silica hydride-based stationary phases.
SYNTHESIS, CHARACTERIZATION, AND EVALUATION OF SILICA HYDRIDE-BASED PERFLUORINATED STATIONARY PHASE by Harshada Natekar Silica hydride based stationary phases have demonstrated unique selectivity and specificity for small sized polar molecules. The weakly hydrophobic nature of silica hydride is thought to be the key reason for its remarkable retention capabilities. Traditional stationary phases bonded with fluorine moieties have also exhibited enhanced retention of small polar molecules. In this research, a perfluorinated silica hydride stationary phase was synthesized by hydrosilation and silanization procedures. Chromatographic characterization of the newly packed column was carried out by a large number of retention studies. The separation capabilities of the column were evaluated in both the aqueous normal-phase (ANP) and reversed-phase (RP) modes. The perfluorinated silica hydride based column showed remarkable retention ability for RP and ANP modes of separation. Hydrophilic molecules were strongly retained in the ANP mode and hydrophobic molecules were retained in the RP mode. Effect of varying pH of mobile phase on the retention time was summarized. Use of acetone as non-polar solvent was demonstrated. In the conclusion, silica hydride based perfluorinated stationary phase successfully exhibited dual retention capability for polar and non-polar analytes. v ACKNOWLEDGEMENTS First and foremost, I would like to express my sincere gratitude to my research advisor Dr. J. J. Pesek for accepting me to work in his research group. I would take this opportunity to thank him for his continuous support and guidance throughout my project, for being flexible and providing freedom of experimenting, and sharing his great expertise in the field of chromatographic separations. I would also like to express my deepest thanks to Dr. Maria Matyska-Pesek for training me in instrumental techniques, for instilling laboratory discipline in me, and for being there in the lab whenever I had difficulty in proceeding. Besides my advisor, I am thankful to my committee members Prof. Bradley Stone and Prof. Roger Terrill for their encouragement, insightful questions, and sparing some time from their busy schedules for evaluating my research work. I would like to thank my fellow lab mate and a dear friend Kathleen Talbott for having fruitful and brainstorming discussions, which surely helped me in my research. Finally, I would like to thank my husband, Suyog, for his unconditional support and tremendous understanding throughout my research work. Also, I'm immensely grateful to the rest of my family back home to India, for their constant encouragement. vi TABLE OF CONTENTS LIST OF TABLES .
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