Improving ion mobility mass spectrometry (IMMS) for national security threat detection.

摘要

Ion mobility spectrometry has been used to detect explosives, chemical warfare agents (CWAs), and other target analytes of interest to national security researchers for over 30 years. Recently, hybrid ion mobility mass spectrometers (IMMS), which provide both mass and mobility information, have been used to detect national security threats. However, a review of mass spectrometry (MS) and IMS/IMMS methods to detect these target chemicals revealed that little work had been conducted to identify the ion species produced by IMS analyses of these compounds.;The following dissertation describes the accurate and reproducible determination of mass-correlated mobility values for IMS chemical standards and CWA simulants (chapter three), explosives (chapters five and six), and uranyl compounds (chapter eight). As a result of these studies, a new IMS was built and interfaced to a time-of-flight mass spectrometer (TOFMS); this instrument was built to obtain more accurate and reproducible mobility values by better control and measurement of the drift gas temperature (chapter four). Another study compared the reactant and analyte ions produced by three ion sources for explosives detection (chapter five). Mass and mobility interferences were also identified for explosives from complex mixtures of common household products (chapter seven).;The major findings of these studies were: Proposed chemical standards for IMS must be characterized for their dependence on drift gas temperature and water content; as a result of these studies, temperature-dependent reduced mobility values should be quoted in the literature for these compounds instead of using a single K0 value for a compound. A DT-IMS, with enhanced temperature control system, can serve as a test-bed for further accurate and precise determinations of mobility values. SESI should be considered as an alternative ion source for 63Ni to conduct trace explosives detection with IMS. 63Ni-IM-TOFMS should be used in future black powder analyses. IMMS data clearly distinguished an explosive compound from an interferent at the same nominal m/z value. ESI-IM-TOFMS can be used for initial chemical analyses of uranyl salt samples.