Detection of Explosives and Explosives-Related Compounds by Single Photon Laser Ionization Time-of-Flight Mass Spectrometry

Abstract

The application of single photon ionization in combination with mass-selective detection by time-of-flight mass spectrometry is described for the rapid detection of the nitro-containing explosives and explosives-related compounds nitrobenzene, 1,3-dinitrobenzene, o-nitrotoluene, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene, as well as the peroxide-based explosive triacetone triperoxide in the gas phase. The technique is demonstrated to be a plausible approach for laser-based rapid detection of explosives. The limits of detection for nitrobenzene and 2,4-dinitrotoluene using SPI were also measured and determined to be 17-24 (S/N approximately 2:1) and approximately 40 ppb (S/N approximately 2:1), respectively.

What can we learn from ambient ionization techniques?

“…Interestingly, the deprotonated TNT signal (m/z 226) was exclusively observed in SESI (Figure 2f), suggesting that the mechanism of SESI is quite different from DESI or EESI. TNT radical anions were also exclusively observed in single photon ionization mass spectrometry (Figure 2g) [97,98]. The relative abundance of the various signals in the mass spectra thus depend on how and how much energy is deposited into the ions.…”

Ultrasensitive detection of explosives and chemical warfare agents by low-pressure photoionization mass spectrometry

“…The LOD of the instrument towards 2,4-DNT was ultimately calculated to be 30 pptv (2.4 pg). In previous studies, the LOD of gas chromatography/ PI-MS towards 2,4-DNT was $ 40 ppbv (2s), [6] and the LOD of sole PI-MS towards 2,4-DNT was 40 ppbv (3s) [22]. The LOD obtained using this technique was improved by 3 orders of magnitude as compared to the previous reports.…”

“…The mass peak at m/z 165 was the base peak in the spectrum with an intensity of 24790 counts and was thus used as the h value. Note that this spectrum was obtained for using a saturated vapor of 2,4-DNT and the concentration of 2,4-DNT (c) was 170 ppbv (298 K) [6]. The LOD of the instrument towards 2,4-DNT was ultimately calculated to be 30 pptv (2.4 pg).…”

“…Thus, 2,4-DNT is suggested to be the best chemical signature for the vapor-phase detection of TNT [2][3][4][5]. Additionally, the degradation products of TNT, such as nitrotoluene (NT) and nitrobenzene (NB), also have higher vapor pressures, and thus could serve as suitable chemical signatures for such explosives [6]. On the other hand, chemical warfare agents such as sarin are extremely toxic, and small amounts are sufficient to cause serious injury or death [7].…”

“…Based on the pressure in the PI region, traditional PI is known as vacuum PI. Vacuum PI has been used widely and several pioneering reports have illustrated its viability in the detection of TAs; however, the LOD of vacuum PI is only at the ten-ppbv level [6,18,22]. Atmospheric pressure PI (APPI) is a relatively new technique employed under ambient pressure, which mainly yields ions via electron attachments and molecule/ion reactions.…”