Get access

A novel discharge source of hydronium ions for proton transfer reaction ionization: design, characterization, and performance

Authors

  • Satoshi Inomata,

    Corresponding author
    1. Atmospheric Environment Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
    • Atmospheric Environment Division, National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
    Search for more papers by this author
  • Hiroshi Tanimoto,

    1. Atmospheric Environment Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
    Search for more papers by this author
  • Nobuyuki Aoki,

    1. Atmospheric Environment Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
    Search for more papers by this author
  • Jun Hirokawa,

    1. Faculty of Environmental Earth Science, Hokkaido University, Kita 10 Nishi 5, Sapporo, Hokkaido 060-0810, Japan
    Search for more papers by this author
  • Yasuhiro Sadanaga

    1. Atmospheric Environment Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
    Current affiliation:
    1. Department of Applied Chemistry, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan.
    Search for more papers by this author

Abstract

A novel ion source based on direct current (d.c.) discharge has been developed for proton transfer reaction ionization operated at relatively high ion drift tube pressure. The shape and geometry of the ion source are designed to maximize overall ion intensity and to minimize interference from sample air. The initial performance of the technique, including speciation and intensity of reagent ions, their stability, and the impact of artifact signals, is evaluated by means of a proton transfer reaction time-of-flight mass spectrometer (PTR-TOFMS) newly built in our laboratory. Intensities of the hydronium (H3O+) ions are typically (5–7) × 105 counts for a 1-min integration time with a duty cycle of ∼1%. The fluctuations of the ion signals over a period of hours are within 4%. Although the formation of artifact ions from sample air (NO+ and Omath image), which react with volatile organic compounds (VOCs) and subsequently cause fragmentation, is observed as background signals in addition to hydronium and mono- and di-hydrate H3O+ ions, intensities of both NO+ and Omath image ions are only ∼0.5% of those of H3O+ ions. Using our PTR-TOFMS system at a drift tube pressure of ∼5 Torr, the detection sensitivities are significantly improved and the detection limits for propene, acetaldehyde, acetone, isoprene, benzene, toluene, and p-xylene are estimated to be at the sub-ppbv level for 1-min integration. Copyright © 2006 John Wiley & Sons, Ltd.

Get access to the full text of this article

Ancillary