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Investigation and characterization of the Direct Analysis in Real Time helium metastable beam open-air ion source: Mechanism of ionization, fluid dynamic visualization, and applications
Date of Award
Dissertation - Pacific Access Restricted
Doctor of Philosophy (Ph.D.)
Pharmaceutical and Chemical Sciences
Patrick R. Jones
First Committee Member
Robert B. Cody
Second Committee Member
Andreas H. Franz
Third Committee Member
Fourth Committee Member
O. David Sparkman
Fifth Committee Member
The DART ion source was introduced in 2005 at the ASMS Sanibel Conference and immediately afterward Professor Sparkman was contemplating of a way to get our lab this revolutionary mass spectrometry ionization technique. It did not take long because it was delivered to the Pacific Mass Spectrometry Facility in August 2006 and I was able to being using and learning the technique. The ion source creates excited state helium metastables (2 3 S) with an ionization potential of 19.8 eV are created by a glow discharge at atmospheric pressure. The metastables are sent through an optional heater, to aid in desorption, enter the open-air to directly ionize your sample or ionize reagent species to react with the analyte molecules. The most observed ionization mechanism is the formation of protonated molecules from a proton-transfer reaction between the analyte and protonated water clusters. The limited to no sample preparation with the "soft" ionization provide very quick identification of intact organic ions in or on various types of matrices. When the DART is coupled to a high resolving power instrument, such as the JEOL AccuTOF, accurate masses and accurate isotope ratios are assigned to aid in the determination of unknown elemental compositions. This research discusses the formation of the metastable species and how they are used to produce analyte and reagent ions within the open-air sample gap of the DART-mass spectrometer interface. A description of the fundamentals on the operation including real time visualization of the fluid dynamics and confirmation of the formation of a hydroxyl radical in the proposed formation of the protonated water clusters, along with applications developed in the Pacific Mass Spectrometry Facility will also be discussed. These include cleavage, desorption, and ionization of solid-phase peptides, desorption of aqueous metal ions using a heated wire filament and the increased ion transmission with the Vapur interface using metal coated glass tube for the transfer tube.
Curtis, Matthew Earl. (2013). Investigation and characterization of the Direct Analysis in Real Time helium metastable beam open-air ion source: Mechanism of ionization, fluid dynamic visualization, and applications. University of the Pacific, Dissertation - Pacific Access Restricted. https://scholarlycommons.pacific.edu/uop_etds/146
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