Negative-ion fragmentation pathways in 2,4,6-trinitrotoluene

Identification and analysis of organic explosives from post-blast debris by nuclear magnetic resonance

The growing threat of terrorism has triggered an urgent need to find effective ways to improve the analysis of explosives. This will aid forensic scientists in analysing the post-blast debris, which in turn helps the law enforcement agencies to frame suitable regulations. Analysis of post-blast debris is challenging as it hosts a massive amount of complexity. There are various techniques reported till date such as mass spectrometry, gas chromatography, high-performance liquid chromatography, Fourier transform infrared spectroscopy, and Raman spectroscopy for the analysis of post-blast residues. However, none of them has been able to identify the structural composition of the explosives. The current research study focuses on identifying the structural composition of the explosives from the post-blast debris using the nuclear magnetic resonance (NMR) technology. The post-blast analytes were extracted from soil samples, cleaned by the solid phase extraction (SPE) method and were rapidly analysed by the nuclear magnetic resonance spectrometer. This paper reports the identification of nitro organic explosives such as pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT) and 2,4,6-trinitrophenylmethylnitramine (tetryl) in post-blast debris by 400 MHz nuclear magnetic resonance spectrometer.

Fragmentation study of hexanitrostilbene by ion trap multiple mass spectrometry and analysis by liquid chromatography/mass spectrometry

The fragmentation pathways of three explosive compounds with similar structures, hexanitrostilbene (HNS), cyclotrimethylene trinitramine (RDX), and 2,4,6-trinitrotoluene (TNT), have been investigated by multiple mass spectrometry (MSn, n = 1, 2, 3) with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources. The electron capture mechanism for these compounds in negative ion APCI and ESI mode differs from the usual negative ion mechanism, deprotonation or addition of other species. This was shown for HNS and TNT, which both gave a [M]- anion but not a [M-H]- ion in APCI, and the [M]- anion of HNS was observed in ESI. The quantitative analysis of HNS was performed by liquid chromatography (LC)/ESI-MS, and the results obtained by the internal standard (ISTD) method were compared with those from the external standard (ESTD) method, demonstrating that both quantitation approaches are useful, with good sensitivity, reproducibility and linearity, and ESTD is preferable in routine applications.

Explosives detection: a challenge for physical chemistry

The detection of explosives, energetic materials, and their associated compounds for security screening, demining, detection of unexploded ordnance, and pollution monitoring is an active area of research. A wide variety of detection methods and an even wider range of physical chemistry issues are involved in this very challenging area. This review focuses on techniques such as optical and mass spectrometry and chromatography for detection of trace amounts of explosives with short response times. We also review techniques for detecting the decomposition fragments of these materials. Molecular data for explosive compounds are reviewed where available.

High-pressure ion source combined with an in-axis ion trap mass spectrometer. 1. Instrumentation and applications

A new combination of a dual EI/CI ion source with a quadrupole ion trap mass spectrometer has been realized in order to efficiently produce negative ions in the reaction cell. Analysis of volatile compounds was performed under negative ion chemical ionization (NICI) during a reaction period where selected reactant negative ions, previously produced in the external ion source, were allowed to interact with molecules, introduced by hyphenated techniques such as gas chromatography. The O2*-, CH3O-, and Cl- reactant ions were used in this study to ensure specific ion/molecule interactions such as proton transfer, nucleophilic displacement, or charge exchange processes, respectively leading to even-electron species, i.e., deprotonated [M - H]- molecules, diagnostic [M - R]- ions, or odd-electron M*- molecular species. The reaction orientation depends on the thermochemistry of reactions within kinetic controls. First analytical results are presented here for the trace-level detection of several contaminants under NICI/Cl- conditions. Phosphorus-containing compounds (malathion, ethyl parathion, and methyl parathion as representative for pesticides) and nitro-containing compounds (2,4,6-trinitrotoluene for explosive material) have been chosen in order to explore the analytical ability of this promising instrumental coupling.