people
|Faculty
|Stephen Weber
 |
Stephen Weber Department of Chemistry |
The Weber group studies a variety of problems in analytical chemistry and related areas. We use a broad array of techniques in the pursuit of a quantitative understanding of the systems that we develop. Separations and electrochemistry are generally our focus, but we own or share with another group a variety of spectroscopic instrumentation, e.g. fluorescence, spr, FTIR, and triple quadruple mass spectrometry. Students and postdocs who have left in the last few years have full-time positions at Pfizer, Arqule, Geneva College, Austin Peay State University, San Diego State University and Michigan Technological University.
We are developing molecularly selective microextractions using artificial receptors. This research promises to have a dramatic impact on analysis. Through the improved selectivity of extraction, fewer components of analytical systems will be introduced into separation/detection systems leading to better detection limits and higher speed analysis. This work is also green chemistry, as we use nonvolatile polymeric systems as the organic solvents for two-phase extractions from aqueous solution. These thin films are used in a procedure called Solid-Phase MicroExtraction or SPME. A former student, Shu Li, was the first to couple SPME to CE. Current work focuses on selective extraction of barbiturates followed by capillary electrophoretic (CE) separation of the drugs.
We are also developing novel and powerful separations based on molecular recognition, such as the interaction with lanthanides and oxygen-containing organic molecules. This has been used to separate neutral organic molecules in nonaqueous solvents by capillary electrophoresis.
In a new project just getting underway, we are collaborating with Professor Peter Wipf of this Department to develop chiral stationary phases using combinatorial chemistry.
Peptides have many important control functions in the body. The usual methods for their determination are simple, accurate and precise, but in order to apply these methods you have to know what you are looking for in order to determine it. What do you do if you want to hunt for new molecules that influence how we think, feel, and act? We are vigorously developing a chromatographic approach which is sensitive and selective. Even now, as the technique is under development, we are making advances that will have an impact in neurochemistry. We are basing the determination on the combination of liquid chromatography and electrochemical detection of copper complexes of peptides. The copper complexes of peptides that are three amino acids or longer are oxidizable (Cu(II)to Cu(III)), and it is this electrochemistry that we use for the detection. One current application we are pursuing is the hunt for acidic dipeptides in the brain. An unbelievably small amount of information is available on the distribution and concentrations of dipeptides in the brain, where as volumes have been written on the amino acids. Recent discoveries that we have made allow the determination of dipeptides at subpicomole levels.
In addition to separation and detection, we are working on sampling protocols. In one project, a collaboration with Professors Michael and Grabowski, we are using small tubes to pull minute quantities of fluid from brain. In another project with Prof. Owe Orwar at Chalmers in Sweden, we are trying to understand how to sample the contents of single, living cells.
The need to work with very small sample volumes requires making small separation and detection systems. We have recently developed novel construction techniques that allow us to mix reagents with chromatographic effluent without significant band spreading.
Our expertise in moving fluids in small volumes has led to research directed towards the discovery of new catalysts to organic reactions. This work, carried out with Professor Scott Nelson of this Department is just getting underway.
Awards
Visiting Scientist Fellow of the Swedish Medical Research Council, 1991-92.
Selected Publications
"A High-Throughput Method for Lipophilicity Measurement," Chen, Zhi; Weber, S. G., Anal. Chem., 2007, 79(3), 1043-1049
"Simultaneous maximization of cell permeabilization and viability in single cell electroporation using an electrolyte-filled capillary," Agarwal, A., Zudans, I., Orwar, O., Weber, S. G., Anal. Chem., 2007, 79(1), 161-167
"The Rotating Ring-Disk Electrochemistry of the Copper(II) Complex of Thyrotropin-releasing Hormone," Meng, R., Weber, S. G., J. Electroanal. Chem, 2007, 600, 325-334
"Optimization of post-column reactor radius in capillary high performance liquid chromatography. Effect of chromatographic column diameter and particle diameter," Xu, H., Weber, S. G., J. Chromatogr. A, 2006, 1113, 116-122
"A Screening Method for Chiral Selectors that Does Not Require Covalent Attachment," Chen, Z., Yang, Y., Werner, S., Wipf, P., Weber, S. G., J. Amer. Chem. Soc., 2006, 128(7), 2208-2209
"Capillary-based, serial-loading, parallel microreactor for catalyst screening," Shi, G., Hong, F., Liang, Q., Fang, H., Nelson, S., Weber, S. G., Anal. Chem., 2006, 78(6), 1972-1979
"Simultaneous determination of biogenic monoamines in rat brain dialysates using capillary high-performance liquid chromatography with photoluminescence following electron transfer," Jung, M.C., Shi, G., Borland, L., Michael, A.C., Weber, S.G., Anal. Chem., 2006, 78(6), 1755-1760
"Use of tris(2,2'-bipyridine)osmium as a photoluminescence-following electron-transfer reagent for postcolumn detection in capillary high-performance liquid chromatography," Jung, M.C., Munro, N., Shi, G., Michael, A.C., Weber, S.G., Anal. Chem., 2006, 78(6), 1761-1768
"Controlling the Electrochemically Active Area of Carbon Fiber Microelectrodes by the Electrodeposition and Selective Removal of an Insulating Photoresist," Lambie, B.A., Orwar, O., Weber, S.G., Anal. Chem, 2006, 78(14), 5165-5171
"Influence of Chemical Kinetics on Postcolumn Reaction in a Capillary Taylor Reactor with Catechol Analytes and Photoluminescence Following Electron Transfer," Jung, M.C., Weber, S. G., Anal. Chem., 2005, 77(4), 974-982