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2 Mass Spectrometry for Trace Detection of Threat Agents
Pages 15-28

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From page 15...
... It has become the gold standard for resolving high-consequence analyses involving water, air, and ground pollution; pharmaceutical drug development and manufacture; treaty compliance verification relating to proliferation of nuclear materials; verification of employee drug abuse for prosecution and job termination; detection of performance-enhancing drugs in horses and athletes; and routine analysis in the chemical, drug, and fuel manufacturing industries. While mass spectrometers have become one of the analytical mainstays of today' s chemists and biotechnology laboratories, they have historically been large, complex systems that occupied the volume of several file cabinets, were operated by highly trained mass spectrometr~sts, and sold for around $250,000.
From page 16...
... This multiple mass analysis technique provides information about the structure of the original molecule and confirms the detection of the target compound. This same chemical specificity can be achieved in a single-ion-trap mass spectrometer by howling the ions of interest in a three-climensional ion trap, colliding them with neutral gas molecules, collecting the fragments, and sweeping the fragments in order of ascending mass out of the trap for detection.
From page 17...
... Laboratory-based mass spectrometers, especially when used in combination with other separation methods such as chromatography, have the ability to identify and quantify targeted chemicals based on molecular weight and structure in very complex mixtures at picomole (Io-~2 mole) to attomole (lo-~8 mole)
From page 18...
... The chemical specificity of an instrumental method can be quantitatively estimated on a consistent basis using a metric called "informing power." In a discussion of the informing power of tandem mass spectrometry (MS/MS) , Yost anti Fetterolf~ use information theory to give figures of merit for chemical resolution of various analysis techniques.
From page 19...
... Thus, one floes not have to determine the identity of an unknown substance from scratch but rather must determine whether it contains one of these ~200 compounds or organisms. If a mass spectrometer is used, the spectrum obtained would be compared electronically against a library of reference spectra, ant!
From page 20...
... below, MSbasecI systems can address several of the specific limitations of current 1MS systems. Lower Detection Threshold with Lower False Alarm Rate Given the unpredictable efficiency of sample acquisition, discussed above, and the possibility that a terrorist wouIc} try to minimize the presence of threat substance residues on his or her hands and luggage, it is desirable to reduce alarm thresholds below current levels to increase the probability of detection of trace residues or vapor.
From page 21...
... 1993. Atmospheric Sampling Glow Discharge Ionization and Triple Quadrupole Tandem Mass Spectrometry for Explosives Vapor Detection.
From page 22...
... TOF spectrometers with large mass ranges may be required if detection of characteristic polypeptides or unique amino acid sequences is the goal, MS/MS and small spectrometers might be used. Single-particle aerosol mass spectrometers are also being developed that can analyze the composition of individual aerosol particles in real time.23, 24 Only further research on these issues will c~eterniine which, if any, MS technology will be appropriate.
From page 23...
... 23 Biological agent analysis will require consiclerable chemical specificity, and MS/MS configurations will be incorporated. MS/MS systems with a single-analyzer, ion trap mass spectrometer have been implemented by Oak Ridge National Laboratory in the chemical ant]
From page 24...
... SOURCE: JHU/APL. TOF mass spectrometer utilizing electron impact ionization for vapors and laser desorption-ionization for higher molecular weight threats (bioregulators, toxins, and microbes; see Figure 2-21.3~ 32 Recent reports from Purdue University suggest that the identification of whole proteins from complex mixtures can be accomplished with lysated cells (E.
From page 25...
... Cooks at Purdue University is leading an initiative on multiplexing anti miniaturizing ion trap mass spectrometers.35 These crevices (Figure 2 3136 are ion traps anti hence have MS/MS capability. They are m~niatunze~i and have a single vacuum system; they are, however, the only devices having separate mass spectrometers and separate ion inlets, allowing different ionization ant} sample handling techniques.
From page 26...
... Deployment of both IMS and MS types with lower alarm levels would be a good test of mass spectrometry's ability to detect at lower levels with fewer false positives than current technology. The probability of detection should be compared with the probability of false alarms at lower alarm thresholds for each technology in an airport scenario, and each technology should be characterized for operational and security adequacy.
From page 27...
... FINDINGS AND RECOMMENDATIONS Baser! on the discussion above, the committee offers two sets of findings and recommendations: Finding I: The trace detection systems currently deployed in airports have limited utility for the following reasons: The relatively low chemical specificity of IMS means that the instrument alarm threshold must be set high to avoid excessive false alarms; yet, lower alarm levels are desirable to account for inefficient manual anti portal sampling techniques and, possibly, "cleaner" perpetrators.
From page 28...
... Rugged m~niatunzec] MS-based trace detection systems should be developed for use in an airport environment in order to achieve lower alarm threshoicis without increasing false alarm rates and to provide versatility for threat substances not now detected.


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