Atmospheric pressure chemical ionization of explosives using alternating current corona discharge ion source

Abstract

The high-sensitive detection of explosives is of great importance for social security and safety. In this work, the ion source for atmospheric pressure chemical ionization/mass spectrometry using alternating current corona discharge was newly designed for the analysis of explosives. An electromolded fine capillary with 115 µm inner diameter and 12 mm long was used for the inlet of the mass spectrometer. The flow rate of air through this capillary was 41 ml/min. Stable corona discharge could be maintained with the position of the discharge needle tip as close as 1 mm to the inlet capillary without causing the arc discharge. Explosives dissolved in 0.5 µl methanol were injected to the ion source. The limits of detection for five explosives with 50 pg or lower were achieved. In the ion/molecule reactions of trinitrotoluene (TNT), the discharge products of NOx (-) (x = 2,3), O3 and HNO3 originating from plasma-excited air were suggested to contribute to the formation of [TNT - H](-) (m/z 226), [TNT - NO](-) (m/z 197) and [TNT - NO + HNO3 ](-) (m/z 260), respectively. Formation processes of these ions were traced by density functional theory calculations. Copyright © 2015 John Wiley & Sons, Ltd.

Explosive detection using a novel dielectric barrier discharge ionisation source for mass spectrometry

“…This evidence suggests a different ionisation mechanism to APCI which produces results similar to those presented in the literature . Unlike in APCI, using plasma in air results in an abundance of ozone, which in turn is responsible for the reduction in the proton abstraction reaction, suggesting a possible reason why, in the case of TNT, the [M − H] − ion is not the most abundant …”

“…Therefore, this latter precursor ion was chosen. This observation is different from APCI, where the 2 most dominants ions are [M] − and [M − H] − at m/z 227 and 226, although, in examples where the ionisation happens in open air, the precursor ion [M − NO + HNO 3 ] − at m/z 260 is common . The product ions of m/z 260 were the usual characteristic ions for TNT, [M − NO] − at m/z 197 and NO 2 − at m/z 46, as shown in Figure A.…”

Discontinuous atmospheric pressure interface for mass spectrometry using a solenoid pulse valve

“…By using heat‐resistive materials for the ion source system, the temperature of the ion source could be increased to 180°C. The present method gave LODs for explosives comparable with our those from our previous method that used a continuous gas introduction system …”

“…In our previous work, an APCI source using an ac corona discharge needle and a nickel capillary (115 μm i.d. and 12 mm long) was developed.…”

Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization

“…Here, HMDD demonstrated strong signal in positive mode for the protonated molecule, as well as peaks associated with lingering acetonitrile solvent vapor. NG, EGDN, and DNT were all detected in negative mode, yielding adducts and ions typical of dc and ac atmospheric pressure chemical ionization [45, 46]. The nitrate esters, NG and EGDN, predominately formed adducts with available anions ( m/z 46 NO 2 - , m/z 62 NO 3 - , m/z 61 HCO 3 - , m/z 77 HCO 4 - , etc.…”