Dissertation
High Accuracy Ion Mobility Spectrometry to Reduce False Alarm Rates in National Security Technology
Doctor of Philosophy (PhD), Washington State University
01/2016
Handle:
https://hdl.handle.net/2376/111929
Abstract
Ion mobility spectrometry (IMS) is the preferred analytical technique for detecting chemical warfare agents, narcotics, and explosives in the field. The compounds of interest are identified based on their reduced mobility (K0) values. When the IMS instrument is calibrated using K0 values from the current literature, detection windows with an error of ± 2% are produced. False positives are triggered when an interferent has a K0 value that falls within this wide detection window. More accurate K0 values for use in calibration will reduce the width of the detection windows and thereby decrease rates of false positives.
The following dissertation describes the steps taken to measure accurate K0 values, which included building an accurate IMS instrument that accurately measured and controlled the variables affecting K0 values (chapter 5). During this work a previously unreported relationship between K0 value and the E/N ratio of the IMS instrument was discovered during the construction of a first instrument (chapter 3). This phenomenon was characterized to determine its validity and that it was not a product of a systematic error (chapter 4). An initial database of accurate K0 values has been assembled for six ions species at multiple drift gas temperatures, drift gas water contents, and electric field strengths (chapter 6), and a method for indirectly quantifying the water content of a drift gas was also developed (chapter 2).
The major findings of these studies were that the ammoniated monomer and ammonium-bound dimer of DMMP can be used to empirically measure the water content of a drift gas using the ratio of K0 values of the monomer:dimer. The K0 value of an ion decreases by less than 1% as a function of E/N in a second-degree polynomial fashion until approaching an apparent asymptote at approximately 4 Td. The K0 values of ions can be measured to better than ± 0.2% accuracy. The overall impact of this work will be to reduce the false alarm rates of IMS field instruments by referencing the accurate K0 values produced on the accurate IMS instrument.
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Details
- Title
- High Accuracy Ion Mobility Spectrometry to Reduce False Alarm Rates in National Security Technology
- Creators
- Brian Christopher Hauck
- Contributors
- Herbert H Hill (Advisor)William F Siems (Committee Member)Peter T. A. Reilly (Committee Member)Charles S. Harden (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Chemistry, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 210
- Identifiers
- 99900581635201842
- Language
- English
- Resource Type
- Dissertation