Monitoring at Chemical Agent Disposal Facilities (2005) / Chapter Skim
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5 Prospective Innovative Chemical Agent Monitoring Technologies
5 Prospective Innovative Chemical Agent Monitoring Technologies
Pages 38-63
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From page 38... ...
The triple constraints of high sensitivity, monitoring technologies that may be developed and high specificity, and rapid response place severe demands deployed to supplement the system currently in use is the on any chemical agent monitoring system for demilitariza- possibility of significantly improving response time, which tion activities (Hill and Martin, 2002)
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PROSPECTIVE INNOVATIVE CHEMICAL AGENT MONITORING TECHNOLOGIES 39 OVERVIEW OF OPTICAL DETECTION TECHNOLOGIES and reflection losses at the mirrors may be as much as 80 percent overall. Long-path measurement through the Basic Principles atmosphere is the basis of differential optical absorption spectroscopy (DOAS)
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From page 40... ...
By deploying of the data acquisition time. a set of retroreflectors at strategic locations, multiple The use of FT-IR for chemical agent monitoring at directions or elevations can be sampled in a short period of demilitarization facilities has been suggested.1 For perimeter time from a single monitoring station.
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PROSPECTIVE INNOVATIVE CHEMICAL AGENT MONITORING TECHNOLOGIES 41 ) -1 cm -1 g (l Absorptivity Wave Number (cm-1)
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42 MONITORING AT CHEMICAL AGENT DISPOSAL FACILITIES FIGURE 5-2 Schematic depiction of open-path Fourier transform infrared spectroscopy. SOURCE: Courtesy of H
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than were measured at ture. Similarly, reference spectra of chemical agents are Tooele in the Utah desert.
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at the analytical signal will be masked by the signals from the interferents wavelength. Unfortunately, most airborne chemical agents present at much higher concentrations.
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PROSPECTIVE INNOVATIVE CHEMICAL AGENT MONITORING TECHNOLOGIES 45 SERS Substrate Fiber Optics Probe From Laser and to Spectrograph Inlet Fan Vapor Solution Jar FIGURE 5-4 Schematic diagram of the system used to show the feasibility of surface-enhanced Raman scattering (SERS) measurements of low-concentration explosives in the vapor phase.
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46 MONITORING AT CHEMICAL AGENT DISPOSAL FACILITIES which often leads to fragmentation of the molecule of inter- small that fragmentation frequently does not occur.
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The big drawback is that false positives possible. The atmospheric instruments are both custom built are common, because compounds with similar weights and and commercially available, although the latter are not as molecular shapes are also detected at approximately the same sensitive as the former.
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If exothermic, F should be very sensitive have much better sensitivity and use a variety of ions as the and most likely background free, since the molecular weights chemical ionization medium. Generally, these instruments of the chemical agents are relatively high.
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Negative ions hold much promise mainly in terms MOLECULAR-LEVEL CHEMICAL SENSORS of selectivity and therefore small background. The ion chemistry is relatively easy to test, both through calculations A number of innovative technologies exist that have the and through the use of surrogates in ion-molecule reactors potential for contributing to the chemical agent monitoring such as flow tubes and ion cyclotron resonance instruments.
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50 MONITORING AT CHEMICAL AGENT DISPOSAL FACILITIES Electronic or Artificial Noses California Institute of Technology, has enabled arrays of simple, readily fabricated, chemically sensitive resistor films An emerging approach to broadband chemical detection to be produced. An array of sensors that individually respond is inspired by the biological olfactory system (Buck and to vapors can produce a distinguishable response pattern for Axel, 1991; Buck, 1996)
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. Live-agent testing at the Edgewood Research, another, thereby enabling vapor identification upon subDevelopment, and Engineering Center at Aberdeen Proving sequent exposure.
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52 MONITORING AT CHEMICAL AGENT DISPOSAL FACILITIES A Methanol Ethyl Acetate Benzene 1 0.8 0.6 0.4 0.2 0 Sensor Number (normalization factor) B 0.5 0.4 0.3 0.2 0.1 0 PC 3 tetradecane -0.1 -0.2 -0.3 0 dodecane 0.5 pentane 1.0 hexane decane PC 1 heptane 1.5 nonane octane 2.0 -0.8 -0.6 2.5 -0.4 -0.2 0.0 0.2 0.4 3.0 PC 2 0.6 0.8 FIGURE 5-9 (A)
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PROSPECTIVE INNOVATIVE CHEMICAL AGENT MONITORING TECHNOLOGIES 53 FIGURE 5-10 Photograph of a "nose-chip," with 12 columns and FIGURE 5-11 Microsphere sensors loaded onto the end of an 6 rows, each having a different polymeric sensor combination and optical fiber array. By averaging the signals of multiple copies of each pixel having a switch under its pair of contact lines.
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From page 54... ...
A training process alone could be quite extensive and time consuming, requiring hundreds or even The Swager group at the Massachusetts Institute of Techthousands of observations to be collected in order to nology has developed a fluorescent indicator that is selective accurately train the array to detect chemical agents in envi- for molecular functional groups. The indicator displays a ronments with complex backgrounds.
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PROSPECTIVE INNOVATIVE CHEMICAL AGENT MONITORING TECHNOLOGIES 55 A B C FIGURE 5-14 (A) Reaction of the Chemical Warfare Indicating Chromophore (CWIC)
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56 MONITORING AT CHEMICAL AGENT DISPOSAL FACILITIES The sensitivity of the Nomadics CWIC sensor (Figure 5-14) Porous Silicon Technology exceeds the present Department of Defense specifications The first chemical sensor that utilized the passive optical for the Joint Chemical Agent Detector (JCAD)
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Field detection of such hazardous substances as phate esters, including the organophosphate nerve warfare chemical warfare agents requires that powerful analytical agents. GB (sarin)
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SOURCE: Courtesy of M.J. Sailor, University of California, San Diego, and Kwok Ong, Aberdeen Proving Ground/Edgewood Arsenal.
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During the time remaining for the CMA pro- In this chapter, the committee identified real-time or neargram, new chemical sensor technology is not likely to be real-time technologies that are based on measurement useful for demilitarization plant monitoring at the STEL principles that differ from those currently being used for regulatory levels or below. The lead times for developing chemical agent monitoring at Army stockpile sites and that engineering prototypes and validating the technology with have the potential of being applied to agent vapor detection.
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Ion mobility spectrometry (IMS) ppb to 10 ppt Unacceptably high level of false positives.
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Aberdeen Proving Ground, Md.: Program Manager for Eisele, F.L., and D.J. Tanner.
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Aberdeen Proving Ground, Md.: Edgewood Sylvia, J.M., J.A. Janni, J.D.
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PROSPECTIVE INNOVATIVE CHEMICAL AGENT MONITORING TECHNOLOGIES 63 explosives or organophosphate nerve agents. Analytical Chemistry Improved partition layer, temporal stability, reversibility, and resistance 74(5)
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