Research Interests:
Research in the Coym lab is focused on understanding the fundamental processes of reversed-phase, high performance liquid chromatography (RP-HPLC). RP-HPLC is the method of choice for the separation of non-volatile analytes. This technology is heavily employed in the pharmaceutical industry, in environmental analysis, in forensics, and in biochemical analysis (proteomics/metabolomics). Although RPLC is known to work well for the separation of non-volatile analytes, the mechanism responsible for retention and separation in RP-HPLC is still the subject of debate.
In the HPLC experiment, a mixture containing several analytes is injected into a column. The column is packed with micron-size, surface-derivatized silica particles—these are known as the stationary phase. The solute mixture is pushed through the column by a solvent, known as the mobile phase. In reversed-phase HPLC, the mobile phase is polar, typically a mixture of water and a polar organic solvent like methanol or acetonitrile. The stationary phase is nonpolar—typically, alkyl ligands are used to derivatize the surface of the silica particles. As solutes travel through the column, different solutes “stick” to the stationary phase to different extents. As a result, some solutes spend more time in the column than others. It is this differential migration that causes separation in HPLC.
We investigate processes that occur in the separation column. These include examination of retention mechanism—is retention by adsorption, partitioning, or a combination of these? What types of interactions occur between a solute, the stationary phase, and the mobile phase? How does changing experimental variables, such as temperature, stationary phase type, or mobile phase type, affect solute retention or separation selectivity? We employ van’t Hoff analysis to elucidate the thermodynamics of the retention process, as well as linear solvation energy relationships to examine the types of intermolecular interactions occurring when a solute is retained. Knowledge of the exact retention mechanism in RP-HPLC will aid in developing methods for the analysis of different compounds. Of particular interest are polar-embedded and polar-endcapped stationary phases. These are alkyl phases that have a polar group either embedded in the alkyl ligand, or bound to the silica surface.
Our lab is well-equipped to carry out HPLC research. We have a dedicated isocratic HPLC system with extended-range column temperature control for examining retention thermodynamics. In addition, we share a fully-automated, gradient HPLC system with Dr. Sandra Stenson’s group.
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