Trace detection

An application of surface-assisted laser desorption-ionization (SALDI) method for practical, ultrahigh sensitivity detection of aromatic amines by GC-MS is reported. The prototype analytical device for trace detection of different organic compounds is created. 

Kresbach, G. M., Annan, R. S., Saha, M. G., Giese, R. W., and Vouros. P. Mass Spectrometric and Chromatographic Properties of Ring-Penta Fluorobenzylated Nucleobases Used in the Trace Detection of Alkyl DNA Adducts. Proceedings of the 36th Annual Conference of the American Society for Mass Spectrometry, San Francisco, June 5-10, 1988. 

Fox, A. Wright, L. Fox, K. Gas chromatography-tandem mass spectrometry for trace detection of muramic acid, a peptidoglycan marker in organic dust. I. Microbiol. Meth. 1995, 22,11-26. 

Shahgholi, M. Ohorodnik, S. Callahan, J. H. Fox, A. Trace detection of underiva-tized muramic acid in environmental dust samples by microcolumn liquid chromatography electrospray-tandem mass spectrometry. Anal. Chem. 1997, 69, 1956-1960. 

Morgan, S. L. Fox, A. Gilbart, J. Profiling, structural characterization, and trace detection of chemical markers for microorganisms by gas chromatography-mass spectrometry. J. Microbiol. Meth. 1989,9,57-69. 

The photodegradation mechanism of 2,4-xylidine to a mineralized form, oxalate was deduced from GC-MS trace detection of reaction intermediates. A summary of the proposed degradation path is shown in Fig. 16.2. The presence of some of these intermediates are supported by GC and HPLC data [2]. 

The functional components of a bomb are a control system, detonator, booster, and a main charge. Such threats can often be recognized from their shape. These can be viewed as bulk detection issues, historically addressed by imaging techniques such as sight or touch. Other threats may take no particular physical form and can only be recognized by their chemical composition. These are often trace detection issues, historically detected by the sense of taste or smell. 

Probably the oldest need for trace detection was for the detection of poisons. Food tasters fulfilled that role, as did canaries when used by miners to warn of poisonous atmospheres underground. In more recent times, society has required the detection of other chemicals. Often a trained dog meets that need. Canine olfaction wiU be discussed in Chapter 3. 

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. 

J.E. Parmeter, G.A. Eiceman andJ.E. Rodriguez, Trace Detection of Narcotics Using a Preconcentrator/ Ion Mobility Spectrometer System, NIJ Report 602-00, April 2001. 

W.J. McGann, P. Haigh andJ.L. Neves, Expanding the capability of IMS explosive trace detection. International Journal for Ion Mobility Spectrometry 5(3) (2002) 119-122. 

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]. 

TSA Criteria for Certification of Explosives Trace Detection Systems, 67 Fed. Reg. 48506-48509 (24 July 2002). 

LOD for each. MacDonald et al. [29], however, aggregate all trace detection technologies into four broad categories. 

Fisher, M. and C. Cumming. Trace detection of nitroaromatic explosives by fluorescence quenching of novel polymer materials, in Proceedings of the U.S. Federal Aviation Administration s Third International Aviation Security Technology Symposium, Atlantic City, NJ, November 27-30, 2001. 

Sampling is difficult because the vapor pressures for most explosives are very low. For example, the room temperature equilibrium headspace concentration of RDX in air is about 10 pptv (parts per trillion by volume). Collection of vapor is further compounded for explosives that are bound in matrices and wrappers and/or are concealed in wrappings or baggage. The prospects for trace detection of explosives are considered to be better when sampling objects for explosives contamination in the form of particles and residue. 

The lack of a capability to screen for explosives hidden on an individual is a major vulnerability in aviation and general security. Personal privacy issues and perceived health risks have deterred the use of bulk detectors, such as X ray, X-ray backscatter, and millimeter wave, for screening of individuals for concealed explosives. Consequently, the TSA is focused on trace detection as the best solution for passenger screening in airports. The TSA has determined that individuals carrying as little as 1 lb of concealed explosives get sufficiently contaminated to be detectable by portal devices that use trace detectors. The level of contamination on an individual s exterior clothing that can be routinely detected by the best portal devices is about 1 pg or about 1 part in 109 of the explosive mass. 

Selective, highly sensitive sensors that can detect trace amounts of explosive vapors in real time are needed to help combat terrorism [1-4], Trace detection of explosives, however, is a formidable task. Selectivity is difficult to achieve because many chemicals can be used as explosives, and they differ from each other in their chemical properties. The extremely small vapor pressures of the explosives make it challenging to achieve highly sensitive vapor-based detection. Also, because the terrorist threat is very broad, combating it requires widespread deployment of inexpensive, low-power-consuming sensors. Therefore, devices... 

Explosive-related chemical Explosive remnants of war Electrostatic discharge Explosives trace detection Explosive vapor detection (U.S.) Federal Aviation Administration Field asymmetric ion mobility spectrometry Fertilizer-Grade AN (ammonium nitrate)... 

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