We are interested in using ion mobility spectrometry (IMS) for chiral separations and environmental analysis. IMS gives much faster separations (millisecond time scale) than conventional chromatography. In IMS, gas-phase ions are separated using an electric field in the presence of a counter-flow of a neutral drift gas. The resulting separation is on the basis of both ion charge and size. Interfacing with mass spectrometry gives further information about species identification.
Chiral ion mobility:
All chiral separations require the presence of another chiral species to form - at least transiently - diastereomers with different properties. In chiral ion mobility, this is accomplished by adding a neutral chiral species (called a chiral modifier) to the counter-flow of drift gas.
Our lab is currently working on characterizing the gas-phase interactions that occur, in order to optimize the separation between stereoisomers. Parameters include modifier identity, concentration, and gas temperature.
Many pesticides are chiral, and the vast majority of chiral pesticides are applied as a racemic mixture of stereoisomers. This is despite evidence that (desired) toxicity and biodegradation are often very stereoselective. We are working on methods to apply chiral ion mobility spectrometry to the analysis of contaminated waters and soils - both for detection and identification of pesticides, and for the determination of their chiral composition. This research also involves interfacing environmental sampling techniques to ion mobility spectrometry. While development of chiral ion mobility spectrometry is ongoing, we are using chiral liquid chromatography as a tool to investigate the biodegradation of pesticides by bacteria.
2. Beetle secretions
Recent work in our lab has shown that the defensive secretions of forked fungus beetles varied with their fungal food source and that the secretions of the ground beetle, Chlaenius cordicollis varied with geographic origin. This research was completed with solid phase microextraction interfaced with gas chromatography-mass spectrometry.
- Excellims chiral ion mobility spectrometer-
mass spectrometer (in-lab)
- Excellims ion mobility spectrometer (in-lab)
- Varian HPLC with diode array detector
- Varian GC-MS
- David E. Clemmer, Indiana University (proline cluster analysis)
- Vince Formica, University of Virginia (forked fungus beetles)
- Neil Holliday, University of Manitoba (Chlaenius cordicollis)
- Amy Vollmer, Swarthmore College (chiral biodegradation of triazole fungicides)
Our research would not be possible without the support of
- Research Corporation Cottrell College Science Award
- National Science Foundation, Small Business Innovation Research (SBIR), sub-contract with Excellims Corporation
- HHMI-supported summer research fellowship for Faye Walker (summer '08), Hannah Rose (summer '10), Daniel Pak (summer '11) and Travis Mattingly (summer '12)
- Swarthmore Start-up Fund
- Swarthmore Research Fund for 2007-2009, 2009-2011, 2011-2013