Research Interest

CHEMICAL SEPARATIONS AND MEASUREMENTS
Our research interests lie in all aspects of chemical separations and measurements—especially liquid chromatography, electrodriven separations such as capillary electrophoresis and electrochromatography, and supercritical fluid chromatography— and in the application of these methods to important biomedical and environmental problems. Separation techniques are the necessary evil for most real analyses, as most samples are far too complex to be analyzed by a direct method. The basic thesis underlying our research efforts is to better understand the chemistry of the separation process, and to use that understanding for the solution of practical problems facing analytical chemists. The understanding of the chemistry of the separation process also allows the chromatographic process to be used to acquire other important physicochemical partitioning data, such as those which control biopartitioning or environmental transport.

One long-range goal of our research is the development of a sound, fundamental theoretical basis for prediction of retention in reversed-phase liquid chromatography. We collaborate on this problem with theoreticians who are interested in molecular dynamics simulations of the chromatographic stationary phase. This problem requires synthesis of stationary phase materials and careful measurement of partitioning of selected molecules between the mobile and stationary phases. In studying this problem we have also become interested in the synthetic process for making stationary phases, in studying gradient elution techniques and applications, and in applying our understanding of the partitioning process to the measurement and prediction of bio- and environmental uptake of compounds. One very important practical question which we are addressing is that of “column equivalence”; that is, how can you predict the differences or similarities among the hundreds of commercially available chromatographic stationary phases?

Electrodriven separations methods offer a different approach to the analysis of complex mixtures than do traditional pressure-driven chromatographic systems. Electrodriven separations may rely on electrophoresis, the transport of charged species through a medium by an applied electric field, or may rely on electrodriven mobile phases to provide a true chromatographic separation. We are interested in the fundamental aspects of these methods as well, and are currently studying unique gels as a medium for electrophoresis and are working toward the development of practical capillary electrochromatography.

Supercritical fluid chromatography uses as a mobile phase a fluid above its critical point, where it will not condense to a liquid. These fluids have solvating powers close to liquids, but diffusion coefficients and viscosities between those of liquids and gases, making them very attractive candidates for chromatographic mobile phases. We collaborate on these investigations with Dr. Thomas Chester, Procter & Gamble Company, and are again interested in studying fundamental aspects of these separations, which will lead us to the solution of important practical problems.