Research with Dr. Coym
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 intermolecular 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 retention mechanisms on polar-group-containing reversed-phase stationary phases, as well as the use of novel mobile phase systems to vary retention and selectivity. In addition to our work with fundamental chromatography, we are working on developing methods for the analysis of traps and lures used to monitor invasive insects.
Our lab is well-equipped to carry out HPLC research. We have two dedicated HPLC systems (one isocratic and one gradient). In addition, we share a fully-automated, gradient HPLC system with Dr. Sandra Stenson’s group. Our research has been funded by a variety of internal University grants, as well as externally via support from the National Science Foundation (CHE-0910474) and the United States Department of Agriculture (USDA).
Recent Publications & Collaborations:
Knight, C. C, Mockel, W. D., Coym J. W., Forbes, D. C., & Battiste, D. R. (2012) Chalcographus Beetle Lure: Extraction and Quantitative Analysis [Abstract]. 19th Annual University of South Alabama Research Forum, Mobile, AL, United States, March 27-30, 2012.
Coym, J. W., Armstrong, A. S., & Charlton, S. A. (2012). The use of methyl-b-cyclodextrin as a mobile phase additive for the reversed phase chromatography of pharmaceutically-relevant compounds. [Abstract]. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Orlando, FL, United States, March 12-16, 2170-1.
Hashmi, O. I. & Coym, J. W. (2012) Solvent strength linearity and pure-water retention estimation using “bio-inspired” reversed-phase stationary phases. [Abstract]. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Orlando, FL, United States, March 12-16, 875-20.
Charlton, S. A. & Coym, J. W. (2012) The use of methyl-b-cyclodextrin to improve the solubility of cholesterol in HPLC mobile phases. [Abstract].
Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Orlando, FL, United States, March 12-16, 875-19.
Ogden, P. B., Coym, J. W. (2011). Retention mechanism of a cholesterol-coated C18 stationary phase: van’t Hoff and Linear Solvation Energy Relationships (LSER) approaches. Journal of Chromatography A, 1218, 2936-2943.