title: Selected Ion Flow-Drift Tube Mass Spectrometry: Quantification of Volatile Compounds in Air and Breath.
abstract: A selected ion flow-drift tube mass spectrometric analytical technique, SIFDT-MS, is described that extends the established selected ion flow tube mass spectrometry, SIFT-MS, by the inclusion of a static but variable E-field along the axis of the flow tube reactor in which the analytical ion-molecule chemistry occurs. The ion axial speed is increased in proportion to the reduced field strength E/N (N is the carrier gas number density), and the residence/reaction time, t, which is measured by Hadamard transform multiplexing, is correspondingly reduced. To ensure a proper understanding of the physics and ion chemistry underlying SIFDT-MS, ion diffusive loss to the walls of the flow-drift tube and the mobility of injected H3O(+) ions have been studied as a function of E/N. It is seen that the derived diffusion coefficient and mobility of H3O(+) ions are consistent with those previously reported. The rate coefficient has been determined at elevated E/N for the association reaction of the H3O(+) reagent ions with H2O molecules, which is the first step in the production of H3O(+)(H2O)1,2,3 reagent hydrate ions. The production of hydrated analyte ion was also experimentally investigated. The analytical performance of SIFDT-MS is demonstrated by the quantification of acetone and isoprene in exhaled breath. Finally, the essential features of SIFDT-MS and SIFT-MS are compared, notably pointing out that a much lower speed of the flow-drive pump is required for SIFDT-MS, which facilitates the development of smaller cost-effective analytical instruments for real time breath and fluid headspace analyses.
authors.affiliation: J. Heyrovsky Institute of Physical Chemistry, the Czech Academy of Sciences , Dolejškova 3, 18223 Prague 8, Czech Republic.|Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague , V Holešovičkách 2, 18000 Prague, Czech Republic.
authors.forename: Anatolii
authors.initials: A
authors.lastname: Spesyvyi
authors.affiliation: Institute for Science and Technology in Medicine, School of Medicine, Keele University , Thornburrow Drive, Hartshill, Stoke-on-Trent ST4 7QB, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Smith
authors.affiliation: J. Heyrovsky Institute of Physical Chemistry, the Czech Academy of Sciences , Dolejškova 3, 18223 Prague 8, Czech Republic.
authors.forename: Patrik
authors.initials: P
authors.lastname: Španěl
mesh_terms: D000388:Air / Q000032:analysis*; D001944:Breath Tests / Q000295:instrumentation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D055549:Volatile Organic Compounds / Q000032:analysis*; D014867:Water / Q000737:chemistry
chemical_list: D055549:Volatile Organic Compounds; D014867:Water