The identification and quantitation of individual compounds in very complex sample matrices presents a challenging analytical problem that demands continual improvement of existing methodology and instrumentation. This demand has been the primary motivation for the development of high-efficiency separation methods, such as gas, liquid, and supercritical fluid chromatography, as well as high-voltage capillary electrophoresis. Our research goals include the advancement of these high-resolution separation techniques and their application to the analysis of complex samples of environmental and biochemical origin. Our research is currently directed in three areas: chromatographic column development, detector development, and analytical applications.
Column Development. Although high-efficiency columns have been used routinely in gas chromatography for many years, only recently have they been available for condensed mobile phases. We are interested in the development of novel columns for liquid chromatography and electrophoresis, such as narrow-bore packed columns, semipermeable packed capillaries, and open tubular capillaries. These microcolumns are capable of achieving very high chromatographic efficiencies (105 - 106 theoretical plates), and concurrently reduce the consumption of both sample and solvent. Our initial studies of new column technology involve the optimization of physical parameters, such as inner diameter, length, particle size, pore size, and other factors. The hydrodynamic performance of the microcolumn is then evaluated and compared with theoretical models. The chemical performance of the microcolumn is then established through detailed analyses of solute-solvent and solute-sorbent interactions. The goal of these fundamental studies is to improve our physical and chemical understanding of separation processes in order to develop columns that more nearly approach the theoretical limits of chromatographic efficiency.
Detector Development. Because of the small dimensions and low flowrates characteristic of microcolumns, very sensitive, low-volume detectors are required. Conventional detection techniques for chromatography and electrophoresis, such as UV-absorbance, fluorescence, and electrochemical measurements, cannot adequately detect solutes present at the nano- to femtogram level in complex samples of nanoliter volume. Consequently, we are interested in the development of other detection techniques that better fulfill the rigorous requirements of microcolumns. In previous work, flame-based detectors that are commonly used in gas chromatography were modified to permit application with microcolumn liquid chromatography. Flame ionization detection was used for non-selective detection of organic molecules, while flame emission and thermionic detection provided element-specific detection of phosphorus, sulfur, and nitrogen in organic molecules. Currently, we are pursuing the development of laser-based detectors for fluorescence, photoionization, and refractive index measurements of the chromatographic effluent. The high sensitivity and selectivity of these detection techniques make them highly promising for microcolumn liquid and supercritical fluid chromatography.
Analytical Applications. Our final research goal involves the application of the improved separation and detection technology developed in our laboratory to problems of environmental and biochemical significance. Flame emission and thermionic detection have been employed for the selective analysis of organophosphorus pesticides and their degradation products in water samples, as well as for the determination of phosphatidic acids and phospholipids in biological matrices. Laser-induced fluorescence detection has been applied to the analysis of polynuclear aromatic hydrocarbons present in coal and fuel oil samples. In addition, many molecules that are not detectable may be chemically modified to incorporate a label that can be selectively detected with the flame- and laser-based detectors. For example, phosphorus and sulfur can be readily incorporated into organic hydroxyl and amine compounds to render them detectable by flame emission or thermionic detection. Fluorescent labels, such as dansyl chloride and substituted coumarin dyes, have proven very successful for the derivatization of such biogenic molecules as amino acids, bile acids, fatty acids, and prostaglandins. The high separation efficiency of microcolumn liquid and supercritical fluid chromatography, when coupled with highly sensitive and selective detection techniques, provides a powerful analytical system for complex clinical and environmental samples.
A complete list of publications for Victoria McGuffin can be found here.
This page last updated June 18, 2001.