Understanding and Development of New Materials for High Performance Liquid Chromatography and Electrophoresis

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My research group is active in analytical separations. High performance liquid chromatography (HPLC) is ubiquitous in chemistry, biochemistry, and industrial labs. Recent years have seen many innovations in the field of HPLC – ultrahigh performance LC, core-shell phases, and hydrophilic interaction chromatography to name but a few. The approach my group takes is to develop a fundamental physico-chemical understanding of the methodology. We then use that understanding to enhance and empower the analytical methods. Within this broad programmatic objective, the short term objective of this DG proposal is to develop and investigate novel polar surfaces for hydrophilic interaction liquid chromatography, normal phase liquid chromatography, and capillary electrophoresis, and to introduce polar modification to porous graphitic carbon to attenuate its strong reversed phase adsorption. Porous graphitic carbon is an attractive phase for HPLC due to its chemical stability and unique selectivity. Building on our past success, we will introduce polar functionalities including amide, catechol, saccharide and poly(oxyethylene) to the carbon surface using diazonium chemistry. This polar modification will enhance multiple modes of HPLC separation. In the ubiquitous reversed-phase liquid chromatography, our polar modifications will attenuate the excessive retention and peak tailing that limits the use of carbon HPLC particles. Hydrophilic interaction liquid chromatography is a rapidly growing mode of HPLC, but one that is restricted to pH 2-8 and <60°C. Our polar carbon phase will expand the separation conditions that can be used. Finally, normal-phase HPLC is current performed on silica and derivatized silica – whose retention character is dictated by the localized polarity of the underlying silica. Our polar carbon will provide stationary phases whose polar sites arise from a non-polar base – allowing purer control of retention in normal-phase liquid chromatography.  We will also investigate the facile modification of porous carbon HPLC particles using pi-pi adsorptive strategies that are popular for modification of carbon nanomaterials. Preliminary results with non-ionic surfactants on carbon indicate that the modification is robust under a range of solvents. Development of polar hydrophilic coatings for capillary electrophoresis will complement our studies of polar chromatographic phases, and provide training opportunities in a diversity of analytical separation methodologies. The above work will be interwoven with fundamental studies of the nature of polar interactions in liquid chromatography. We investigate the impact of: non-traditional solvents on hydrophilic interaction liquid chromatography; temperature on retention and selectivity; and localization of polar interactions in normal phase chromatography.