Development of New Fluorous Stationary Phase Technologies for Improved Analytical Separations
Daley, Adam Bruce
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Applications taking advantage of fluorine-fluorine interactions for separations are a recent analytical trend, with benefits in terms of cost, ease of use and specificity cited as advantages of these so-called “fluorous” techniques. While most current fluorous separations employ columns packed with microspheres, columns based on entrapped microspheres, porous polymer monoliths (PPMs) and open tubes all represent viable alternatives to conventional packed capillaries. In this thesis, the design, optimization and implementation of fluorous stationary phases based on all three of these new technologies are explored. Development of methods and techniques using these systems are presented, with factors affecting their performance being examined. Doing this, the specificity of the fluorous interaction can also be explored, and potential applications for these new materials can be discussed. For the work with entrapped microspheres, the columns that were formed did not prove to have an advantage over those that were unentrapped. Although affixing spheres within a matrix is known to have benefits in terms of bed stability over repeated use, the inclusion of a polymer coating proved to represent a greater concern for the availability of the bead-based stationary phases. Layers of polymer forming over the surface were shown to limit the access of analytes to the entrapped microspheres, restricting the usefulness of these materials. The work with fluorous monoliths proved the most successful, providing clear evidence of improved selectivity when compared to analogs made without fluorination. Fluorous retention specificity was also effectively examined, with secondary effects probed and compared to those that had been discussed for commercially-available fluorous microspheres. Results showed that the monoliths were very much in-line with what had already been seen for sphere-based systems, with residual substrate character providing only a slight contribution to the observed separations. Finally, development of open-tubular columns based on microstructured optical fibers was the most speculative of the projects discussed here. The introduction of a fluorous stationary phase through silanization was demonstrated to be an effective method for imparting chromatographic selectivity into these columns, and controllable factors such as treatment protocol and silane character were shown to affect the performance of the resulting materials.