| The emergence of Ultra-High Pressure Liquid Chromatography (UHPLC) as a viable technique for the achievement of high efficiencies in complex separations has made it an increasingly popular field of research. As UHPLC enters the development stages for a possible presence in commercial instrumentation, there is a growing need to explore more of the fundamental aspects of chromatography at ultra-high pressures.; An important prerequisite for these types of studies is the availability of an adequate stationary phase support material. An ideal support for UHPLC would have, among other qualities, a rigid structure with high mechanical and chemical stability, monodisperse size distribution, and sufficient surface area to allow for the loading of enough sample for adequate detection without overloading the column. This report details our research into the development of superficially porous spheres for use as a stationary phase support in UHPLC.; Past research in our lab has established that reversed-phase liquid chromatography (RPLC) experiences tremendous gains in efficiency with the use of small particles and ultra-high pressures. However, no systematic studies have been performed on any of the other common modes of chromatography. Ion exchange chromatography has obvious utility in the realm of biological separations, and is therefore one of the prime candidates for the next phase of fundamental studies in UHPLC.; Prevailing theories of ion exchange suggest that the limiting factors in separation efficiency are related to diffusion and mass transfer of the analyte.{09}The ion exchange reaction, it is claimed, is essentially instantaneous and is not an issue. If true, this would suggest that the use of small particles and UHPLC, which dramatically reduces analyte diffusion and resistance to mass transfer, would provide a gain in separation efficiency similar to that seen with RPLC.; A strong cation exchange system was developed for the investigation of ion exchange processes in UHPLC. This system consistently produced efficiencies that were much poorer than theory would predict if mass transfer were the predominant kinetic feature. Evidence is provided which indicates that the adsorption and desorption of analyte at the particle surface is the limiting factor in ion exchange kinetics, not mass transfer. |
