The Chemistry Underlying Detection of Explosives by IMS

Other reaction channels may involve proton abstraction from the analyte molecule, which is essentially proton transfer to the reactant ion (Equation 12.2), forming an (M-H)- ion. 

More common are association or ion attachment reactions (Equation 12.3), which can be followed by dimerization or clustering (Equation 12.4) with elevated concentrations of M and collisional stabilization  

FIGURE 12.1 The mobility spectra of several types of explosives. (From Hilton et al., Improved analysis of explosives samples with electrospray ionization-high resolution ion mobility spectrometry (ESI-HRIMS), Int. J. Mass Spectrom. 2010,298,64-71. With permission.) 

30 ng for 2,4-DNT and 11-74 ng of diphenylamine (DPA). Methods for sampling the presence of taggants in the vapor phase and preconcentrating them with a SPME device were also studied by the same group. ° 

Portals for explosive detection should be like those used for metal detection screen people rapidly and with minimal intrusiveness as they pass through a portal. Portals have the capability to draw an air sample from a person s whole body, preconcentrate the vapors, and perform an analysis by IMS within a few seconds. Portals may also employ jets of air and gentle physical contact to detach particles, trap them on a filter, and thus enhance the sensitivity of the detector. In principle, a security checkpoint with such a portal could be designed to lock and trap a would-be bomber and limit the damage that may be inflicted by a suicide bomber. 

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