Engineering Aviation Security Environments—Reduction of False Alarms in Computed Tomography-Based Screening of Checked Baggage (2013) / Chapter Skim
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C--Chemistry-Based Alternatives to Computed Tomography-Based Explosives Detection
C--Chemistry-Based Alternatives to Computed Tomography-Based Explosives Detection
Pages 73-80
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From page 73... ...
It is conceivable that one could manipulate non-explosive materials to get the same output as given by an explosive. GENERAL REQUIREMENTS FOR ALTERNATIVE TECHNOLOGIES TO COMPUTED TOMOGRAPHY-BASED EXPLOSIVES DETECTION Any technology developed to augment or replace CT for explosives detection must be moleculespecific because explosives have a wide variety of chemical structures, some of which are very similar to an even larger class of non-explosive materials, and may, moreover, be present in mixtures that have responses different from those of pure explosives.
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From page 74... ...
The potential of MS in aviation security applications was described in the 2004 report of the NRC Committee on Assessment of Security Technologies for Transportation, Opportunities to Improve Airport Passenger Screening with Mass Spectrometry. In that report the committee's focus was MS's potential in explosives trace detection (ETD)
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From page 75... ...
These are discussed in the following section. Recent Developments in Mass Spectrometry Ambient Ionization Ambient ionization refers to a family of methods developed since 2004, in which samples are ionized in their native environment and original physical state without needing to be prepared by transferring analyte ions from near the surface of the sample into the vacuum system of the mass spectrometer.
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From page 76... ...
The method shows promise as an ionization method complementary to DESI: It ionizes many small molecules, including explosives, and generates mass spectra characterized by abundant molecular ions from which molecular weights are obtained and from which MS/MS spectra can be recorded showing characteristic fragment ions for compound identification.
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From page 77... ...
Moreover, the low-impact nature of DESI and other methods of ambient ionization means that the mass spectra are dominated by intact molecular ions. The specific identification of materials as particular chemical entities is arguably more important and more difficult than achieving the speed and sensitivity necessary for airport security detection purposes.
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From page 78... ...
Current efforts focus on optimization of ion transport in these experiments, which remain inefficient in spite of ability to detect subnanogram amounts of explosives using benchtop instruments. Most losses are in the atmospheric pressure region and involve failure to efficiently transport the atmospheric pressure ions/ionized droplets into the mass spectrometer.
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From page 79... ...
Perry, and R Graham Cooks, Trace detection of explosives distributed over large areas using mass transfer and ambient ionization mass spectrometry, Analyst 135:1953-1960, 2010.
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From page 80... ...
Among the favorable characteristics of these instruments are their small size and the highly capable ambient ionization methods, which are rapid and sensitive and yet give a great deal of specific information on the chemical nature of a particular sample, including information on the presence of traces of explosives on surfaces. Other characteristics, like the ability to perform stand-off MS detection, the ability to add specificity by "reactive" ionization methods, the ability to quantify, and the ability to extend the methodology to surfaces with large areas are less well developed but are under study.
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