Improvements in Drift Tube Reaction Mass Spectrometry

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Professors Eric P. Grimsrud and Walter B. Knighton are funded by the Analytical and Surface Chemistry program for work on drift tube reaction mass spectrometry. The PI's seek to improve the performance of mass spectrometry for rapid trace measurement of volatile components in the atmosphere. An effective strategy for creating ions of trace components without saturating the mass spectrometer with an oxygen or nitrogen gas signal is ionization with the hydronium cation in a flow or drift tube before the mass spectrometer. In this proton transfer gas phase reaction, most trace components can be selectively and quantitatively ionized. However, the hydronium cation ion source is not without problems, principally water cluster formation and excessive fragmentation of the trace component. For these reasons, additional work is proposed on interrelated instrument parameters of drift tube pressure, flow velocity, and pressure as well as reaction rate studies for proton transfer from the hydronium ion to various trace components. Drift tube reaction mass spectrometry is a general technique by which the volatile organic compounds present in ambient air or human breath can be directly determined in real time without the time lag associated with more conventional methods of analysis. Improved methods such as these are needed for applications ranging from medicine to national security.