Dissertation
Buffer gas modifiers in ion mobility spectrometry
Washington State University
Doctor of Philosophy (PhD), Washington State University
08/2009
DOI:
https://doi.org/10.7273/000005994
Abstract
Liquid dopants (modifiers) were vaporized into the buffer gas of an ion mobility spectrometer to change ion mobilities. In this investigation, ion mobilities varied to different extent depending on the structure and size of ions, and the concentration of the buffer gas modifier. Steric hindrance and intramolecular bridges produced low responsiveness of ions to modifiers by inhibiting clustering. The mobilities of several chemical standards for ion mobility spectrometry (IMS) decreased when modifiers were introduced into the buffer gas to simulate contamination. The order of reduction in mobility with contamination in the buffer gas was: tetraalkylammonium ions <DTBP <2,4-lutidine H"analytes. These different responses of analytes and chemical standards would make the calculation of reduced mobilities, K0, using chemical standards inaccurate when contamination is present in the buffer gas. Therefore, a new calibration procedure is recommended for IMS that uses two classes of chemical standards, an "instrument standard" and a "mobility standard". Instrument standards calibrate the instrumental parameters. Mobility standards determine the degree of contamination in the buffer gas. An instrument standard should be insensitive to contamination in the buffer gas and a mobility standard should be sensitive to this contamination. DTBP was confirmed as a good instrument standard and 2,4-lutidine as a good mobility standard. Tetraalkylammonium ions are recommended over DTBP as instrument standards for electrospray ionization (ESI) IMS. Finally, ESI-IMS was used for the analysis of a set of beverages and over-the-counter drugs. Analysis times below one minute were obtained for IMS after a simple dissolution step, and 12 new reduced mobilities values were reported. Fast analysis times, sensitivity, high resolution, easy operation, inexpensive maintenance, and low cost of IMS instruments make IMS an attractive alternative to slow and expensive methods, such as chromatography, for the qualitative analysis of over-the-counter drugs and beverages
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Details
- Title
- Buffer gas modifiers in ion mobility spectrometry
- Creators
- Roberto Fernandez-Maestre
- Contributors
- Herbert H. Hill (Chair)William F Siems (Committee Member) - Washington State University, Department of ChemistryKen Nash (Committee Member) - Washington State University, Department of Chemistry
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Chemistry
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 230
- Identifiers
- 99901055135501842
- Language
- English
- Resource Type
- Dissertation