Analysis and Detection of Explosives by Mass Spectrometry

Mass spectrometry has become a routine technique for forensic analysis of explosives and one of the technologies used for vapor and trace detection of hidden explosives. 

Mass spectrometry is the field dealing with separation and analysis of substances according to the masses of the atoms and molecules of which the substance is composed. The principle of mass analysis is that parameters of time and space of the path of a charged particle in a force field in vacuum are dependent on its mass-to-charge ratio (m/z). 

The two main types of mass spectrometers used for analysis and detection of explosives are the quadrupole and the ion trap. These two types of mass analyzers are relatively small, when compared with magnetic sector instruments. They can be miniaturized to make mobile detectors weighing less than 15 kg. 

Aspects of Explosives Detection M. Marshall andJ.C. Oxley (Editors) 

Ions produced in the source enter the trap through the inlet focusing system and the entrance end-cap electrode. Various voltages are applied to the electrodes to trap and eject ions according to their mass-to-charge ratios. 

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Tanner SD, Davidson WR, Fulford JE. 1983. The instantaneous detection of explosives by tandem mass spectrometry. In Proceedings of the International Symposium on the Analysis and Detection of Explosives, FBI Academy, Quantico, VA, March 29-31, 1983. Washington, DC U.S. Department of Justice, Federal Bureau of Investigation, 409-417. 

With a focus on trace forensic detection of explosives, especially for use in counterterrorism and to counter narcotics investigations, Fetterolf et al. [75] evaluated the use of ion mobility-mass spectrometry for explosives determinations. In this, explosives residues were collected on a membrane filter by a special attachment on a household vacuum cleaner. Although subsequent thermal desorption and analysis required only 5 s, fimits of detection for most common explosives were as low as 200 pg. The persistence of explosives on hands and transfer to other surfaces were also examined as were post-blast residues of NG on fragments of improvised explosive devices constructed with double-based smokeless powder. Finally, postblast residue from C-4, Semtex, and other explosives was found by IMS analyses on items of forensic and evidentiary value. These few out of many examples demonstrate that mobihty spectrometers are well suited tools for laboratory and on-site investigations, before and after the use of explosives. 

The equipment for screening passengers and baggage is designed to identify trace amounts of specific known explosives. Analytic trace detection is conducted using mass spectrometry, gas chromatography, chemical luminescence, or ion mobility spectrometry. Ion mobility spectrometry is most commonly used. Novel explosive material wiU not be probably detected by these systems. Information on the equipment s technical performance is not publicly available because of security reasons, which inhibits an independent analysis of equipment s performance [160]. 

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