Dopant-Assisted Negative Photoionization Ion Mobility Spectrometry for Sensitive Detection of Explosives

Abstract

Ion mobility spectrometry (IMS) is a key trace detection technique for explosives and the development of a simple, stable, and efficient nonradioactive ionization source is highly demanded. A dopant-assisted negative photoionization (DANP) source has been developed for IMS, which uses a commercial VUV krypton lamp to ionize acetone as the source of electrons to produce negative reactant ions in air. With 20 ppm of acetone as the dopant, a stable current of reactant ions of 1.35 nA was achieved. The reactant ions were identified to be CO 3by atmospheric pressure time-of-flight mass spectrometry, while the reactant ions in 63 Ni source were O 2. Finally, its capabilities for detection of common explosives including ammonium nitrate fuel oil (ANFO), 2,4,6-trinitrotoluene (TNT), N-nitrobis(2-hydroxyethyl)amine dinitrate (DINA), and pentaerythritol tetranitrate (PETN) were evaluated, and the limits of detection of 10 pg (ANFO), 80 pg (TNT), and 100 pg (DINA) with a linear range of 2 orders of magnitude were achieved. The time-of-flight mass spectra obtained with use of DANP source clearly indicated that PETN and DINA can be directly ionized by the ion-association reaction of CO 3 − to form PETN·CO 3 − and DINA·CO 3 − adduct ions, which result in good sensitivity for the DANP source. The excellent stability, good sensitivity, and especially the better separation between the reactant and product ion peaks make the DANP a potential nonradioactive ionization source for IMS.

Dopants and gas modifiers in ion mobility spectrometry

“…In addition to the sources containing radioactive isotopes or sets of electrodes for a corona discharge, another ionization method commonly used in IMS is photoionization with ultraviolet (UV) radiation [79,80]. The earliest report on the use of photoionization ion mobility spectrometry appeared in 1983 [81].…”

“…The mechanism of the production of the reactant ions for this case can be described by the following series of reactions [79]: …”

“…Therefore, in many analytical applications, it is necessary to ensure the stability of the concentration of the admixture. Permeation standards constructed from vials covered by membranes are often used as sources of dopants [79,86].…”

Electrochemical Sensor for Explosives Precursors’ Detection in Water

“…Spectroscopic approaches have been the most widely explored [2][3][4][5][6][7], but quartz crystal microbalance (QCM), ion chromatography [8], capillary electrophoresis [9], surface-enhanced Raman scattering (SERS) [10], nanotechnology based-methods (using molecularly imprinted polymers [11], nanotubes, or nanoparticles), and sensor techniques [12][13][14][15][16] have also been largely described. Amongst the different types of sensors developed to address this need, the electrochemical sensors [17][18][19] present the advantages of being fast, inexpensive, and adapted to miniaturization.…”

Fluorescent Nanofilms for Nitroaromatic Explosives Detection-Promises and Challenges

“…A crucial example is the detection of trace amount of 2,4,6-trinitrotoluene (TNT), which is a typical nitro-aromatic explosives [4][5][6][7][8]. Various TNT detection methods are currently available, such as, the fluorescence quenching method, micromechanical sensors based on micro cantilever, the electrochemical method, ion mobility s pectroscopy (IMS), the surface-enhanced Raman spectroscopy ( SERS) and semiconductor based gas sensors [7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Among t he above-mentioned methods used for TNT detection, the fluorescence quenching method is considered to be the most effective tool for sensing nitro-aromatic explosives in recent years owing to its high sensitivity, convenience, easy visualization, and short response t ime for detection [24].…”