Explosives by IMS

Danylewych-May L. L., Modifications to the ionization process to enhance the detection of explosives by IMS, Proc. First Int. Symp. Explos. Detect. Technol., FAA, Atlantic City NJ, Nov. 13-15, Khan S. M, Ed., 672-686, 1991. 

Eiceman et d. [23] determined that mixtures of product ions, M 02 and (M-H), can be observed when ion formation and determination are fast, as with an atmospheric pressure ionization (API) mass spectrometer. In contrast, usually (M—H) or M-02 (but not both) is observed with explosives in IMS drift mbes where residence times for ions are Sms or greater, enough time for proton abstraction to be complete [24]. Alternatively, the M-02 ion may undergo dissociation with charge retention by the analyte molecule as shown in Eq. (3) and Figure 6 ... 

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. 

This book outlines the basic principles needed to understand the mechanism of explosions by chemical explosives. The history, theory and chemical types of explosives are introduced, providing the reader with information on the physical parameters of primary and secondary explosives. Thermodynamics, enthalpy, free energy and gas equations are covered together with examples of calculations, leading to the power and temperature of explosions. A very brief introduction to propellants and pyrotechnics is given, more information on these types of explosives should be found from other sources. This second edition introduces the subject of Insensitive Munitions (IM) and the concept of explosive waste recovery. Developments in explosive crystals and formulations have also been updated. This book is aimed primarily at A level students and new graduates who have not previously studied explosive materials, but it should prove useful to others as well. I hope that the more experienced chemist in the explosives industry looking for concise information on the subject will also find this book useful. 

Although reliable and capable of operation by non-specialists with trace detection capabilities useful for explosives screening, IMS analyzers are comparatively low in resolution although specificity of response is strong owing to the method of ionization of sample and the additional evaluation of product ions with mobility, increased specificity and expanded scope of response to an enlarged list of explosives is a reasonable... 

The past decade may be characterized by an intense research effort to improve the sensitivity and reliability of ion mobility-based instruments for detection of explosives and to expand the inventory of detectable explosive substances. In addition, improvements in sampling techniques have been proposed, standards for calibration of ion mobility spectrometry (IMS) instruments and for method verification have been developed, and novel instrumental techniques based on laser ablation or electrospray ionization have been advanced. This has occurred due to the rising need for rapid, efficient, and reliable detectors of explosives that are used in acts of terrorism worldwide, as stated in many occasions (see Rame 12.1). Some idea about the scale of this trend can be gained from a recent report Austin, TX, 15 Septanber, 2011—Sales of Explosives, Weapons, and Contraband (EWC) Detection equipment to the world s airport authorities, amassed a significant 834.9 million in 2010, according to a recent study published by IMS Research, a leading provider of market research in the homeland security industry. ... 

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. 

In another study, 17 of the most common suspected interferents for detection of TNT by IMS technology in airport scenarios were investigated. The reactant ion was chloride, the most common reactant ion in explosive detectors. Ten of the interferents showed no IMS response, and of the other seven, only two presented a problem 4,6-Dinitro-( -cresol had a close reduced mobility value and 2,4-dinitro-phenol competed with ionization of TNT. The personal account given in Frame 12.2 shows that some chemicals that give a false-positive response may come from unexpected origins, such as hand lotion or other common cosmetics and medications. 

Various Ionization Methods for Trace Explosive Threat Detection by IMS Several articles and books review IMS for trace explosives detection [18, 45, 48]. In particular, a review article, describes many of the product ion formation reactions that create IMS product ions from explosive compounds [45]. The review also contains extensive tables of reduced mobility (Ko) values, which are used to identify ions in IMS, for the most common explosive compounds. 

Theoretically, any molecules that can be ionized are detectable by IMS-based detectors. Researchers have shown that IMS detectors can be used in various applications, such as detecting explosives, illicit drugs, CWAs, and many TICs. It has also found other applications. At present, interest is greatest in instruments that can detect multiple chemicals to minimize the number of devices necessary for an operation. This focus has made IMS detectors desirable because of their nonselective but high identification power attributes. 

Lighting fixtures installed in Division 1 areas must be explosion-proof and marked to indicate the maximum wattage of allowable lamps. Alsn, they must be protected against physical damage by a suitable guard im liy location. 

Seals are required at entries by conduit or cable to explosion-proof enclosures containing arcing or high-temperature devices in Division 1 and Division 2 locations. It is not required to seal IM in. or smaller conduits into explosion-proof enclosures in Division 1 areas housing switches, circuit breakers, fuses, relays, etc., if their current-interrupting contacts are hermetically sealed or under oil (having a 2-in. minimum immersion for power contacts and 1-in. for control contacts). 

Of the explosives listed in Table 4, only those such as NG with vapour pressures greater than 10 Pa at 25°C are good candidates for the direct detection of vapour by current instrumental techniques. However, vapour pressure rises markedly with temperature. In addition, consideration of the thermal stability data in Table 4 offers the possibility of heating samples containing traces of involatile explosives such as RDX or PETN to increase their vapour pressure and render them detectable. This is the basis of the common technique of combining a heated inlet system with a vapour-type detector, for example, the method of desorption from a swab on a heated stage often used with IMS or TEA systems. This approach has greatly broadened the scope of what were previously viewed as vapour-type detectors and is now standard practice such instruments are now known as particle detectors. 

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