title: Detection of explosives using a hollow cathode discharge ion source.
abstract: BACKGROUND
  For public security and safety, it is highly desirable to develop an ion source for the detection of explosives that is highly sensitive, compact in size, robust, and does not use any special carrier gases such as helium. In this work, a hollow cathode discharge (HCD) ion source was developed for the detection of explosives using ambient air as a carrier gas.
  
  
  METHODS
  To detect nonvolatile and thermally unstable explosives with high sensitivities, a new HCD ion source was designed and coupled with an ion trap mass spectrometer.
  
  
  RESULTS
  Five explosives--hexamethylene triperoxide diamine (HMTD), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), pentaerythritol tetranitrate (PETN), nitroglycerin (NG) and trinitrotoluene (TNT)--were detected with limits of detection of lower than ng. The intensities of the NO3(-) adduct ions with RDX, PETN, and NG showed a marked increase with increase in ion source pressure in the range of 1-28 Torr.
  
  
  CONCLUSIONS
  Because the major NOx(-) ions (x = 2, 3) produced in the plasma act as reagent ions in ion-molecule reactions of explosives, air is best suited as a carrier gas for the detection of explosives. It is proposed that the NOx(-) (x = 2, 3) and O3 contributed to the formation of [TNT-H](-) and [TNT-NO](-) ions, via the reactions NOx(-) + TNT → [TNT-H](-) + HNOx and [TNT](-) + O3 → [TNT-NO](-) + NO2 + O2.
authors.affiliation: Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, 400-8511, Japan.|Department of Chemistry, University of Dhaka, Dhaka, 1000, Bangladesh.
authors.forename: Ahsan
authors.initials: A
authors.lastname: Habib
authors.affiliation: Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, 400-8511, Japan.
authors.forename: Lee Chuin
authors.initials: LC
authors.lastname: Chen
authors.affiliation: Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, 400-8511, Japan.|Institute of Ion-Plasma and Laser Technologies, Durmon Yoli 33, 100125, Tashkent, Uzbekistan.
authors.forename: Dilshadbek T
authors.initials: DT
authors.lastname: Usmanov
authors.affiliation: Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, 400-8511, Japan.|School of Chemical and Life Sciences, Shenyang Normal University, 253 Huanghe Street, Shenyang, Liaoning, 110034, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi, 400-8511, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hiraoka