CWA and TIC Detection

FT-IR can be used for detection of CWAs and TICs in vapor, liquid, or solid samples. The most common method used in identifying chemicals in samples is to compare the resulting spectrum to the various libraries stored in the instrument. For instruments used in detection of CWAs and some TICs, the library may be limited to the chemicals of interest for faster search results. This is different from attempts to identify unknown chemicals, as the spectrum may have to be compared with a 

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Bruker Daltonics has also developed chanical monitors based on IMS technology that cover CWA and TIC detection tasks (Hgure 13.3). The RAID series includes the portable RAID-M 100 detector, which provides very low detection limits, and the RADD-XP, which has chemical and radiological detection in one system, as well as the... 

Capabihties of existing commercial sensors are limited. Most manufactured sensors are designed for use in specific environments to detect compounds of their interest. Sensor systems that can detect a large number of chemicals are needed at present. Given the high toxicity of the CWAs and TICs, detection sensitivity of many existing sensors must be improved significantly. 

Advances in analytical chanistry, nucrotechnologies, and computer software have made more techniques available for CWA and TIC detection. Detectors have become smaller, more sensitive, more reliable, and with more functions. Modem computer technologies have permitted more sophisticated data processing to enable fine-tuning of detection algorithms. Further nfiniaturization of detectors that are more sensitive, with lower false-alarm rates, and high tolerance to varied environment conditions snmmarizes the current focus of development. 

In this paper several Chemical Warfare Agents Simulants (CWAS), some of their hydrolysis and degradation products, and Toxic Indnstrial Compounds (TIC s) were analyzed nsing vibrational spectroscopy. The objective of this work is to characterize the spectroscopic signatures of these threat compounds and to demonstrate, at laboratory scale, the capability of Infrared and Raman spectroscopy for generating methodologies for detection of CWA and TIC s. 

FIGURE 13.2 Left Small, lightweight, continuous, real-time detector of CWAs and toxic chemicals. Right Sabre Centurion II, automated fixed-site CWA and TIC threat air monitoring and detection system. (From Smiths Detection, Chemical agents and toxic industrial chemicals detection equipment, http //www.smithsdetection.com/chemical agents TICS.php.)... 

This device is a stationary ion mobility spectrometer for detecting CWAs and TICs through mode changes. Automatic polarity switching permits detection of all CWAs continuously. Sophisticated software prevents false alarms due to Interfering substances. Specially designed for continuous operation for up to 1 year before maintenance. 

FPD is very sensitive for sulfur and phosphorous compound detection. The reported limit of CWA detection is at the parts-per-billion level, which is lower than the IDLH levels set for all CWAs and TICs. 

Based on observations from testing of various devices from different manufacturers, both PID and FID instruments would not be the detectors of choice for CWA or TIC detection without the addition of a GC type of compound separator to increase selectivity. In brief, other detection technologies are preferable. (The related DPP test report is posted at http hld.sbccom.army.mi1/ip/reports.htm detectors.)... 

We have discussed various technologies employed for detection of CWA and TIC vapors. Each of those technologies offers nnique desirable as well as undesirable features. There is considerable room for improvement. Increasing detection reliability and reducing the frequency of false responses continue to be major challenges. The recent emphasis on TIC detection capability in addition to that of CWAs has also created substantial challenges for researchers and developers. Such requirements limit the number of technologies that can be effectively used. 

Numerous methods, techniques, and instruments have been developed for the detection of CWAs and TICs. After the Septanber 11 incident, aggressive efforts have focused on obtaining better detectors for diverse scenarios. 

Different analytical strategies have been employed to increase the sensitivity and specificity of IMS-based instruments for detection of CWAs and toxic indnstrial chemicals (TICs). Dopants, such as acetone, are utilized to enhance the performance of IMS instruments in several commercial instruments. A different approach to increase performance was to operate at pressures below or above the ambient pressnre. In the former case, it was reported that the reduced pressure doubled the resolution of the DMS, thus improving the specificity of the device. In the latter case, the IMS was operated at pressures up to 4,560 torr (6 bar) for detection of DMMP (commonly used as a simulant for nerve agents) and other compounds. Resolution increased, to a certain extent, with pressure (and the electric field strength), but once clnstering effects became dominant, the resolution did not increase as theory predicted. ... 

V plays an important role in determining deployment and detection effectiveness. The V of aU CWAs and some TICs is higher or much higher than their respective IDLH concentration levels. This suggests that the chemicals can easily reach dangerous vapor concentrations in the surrounding air. 

Appearing below are selected requirements for the development of future detection devices such as the JCAD. As mentioned previously, the JCAD is intended to be widely deployable to replace or complement the ACADA. The JCAD must be able to detect and identify numerous CWAs and selected TICs. 

CWAs are manufactured and stored by government facilities for basically two reasons. Stored CWAs serve as an effective deterrent to first use of CWAs by others. Secondly, manufacture of these agents permits necessary research of agent characteristics, and provides a means for research of detection techniques and antidote developments. Early detection and warning of even minute amounts of CWAs and/or TICs in the air are essential to minimize casualties. 

Other types of detectors are less selective and will respond to many chaiucals. Hame ionization detectors respond to a large number of orgaific compounds without discrinunation. Thus, they would not be suitable detection devices for CWAs or TICs in the field where the potential for exposure to specific toxins is unknown. 

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. 

Audio and visual alarm Indicators. Can be upgraded to detect new compounds through changeable data libraries. Capable of storing 50 libraries of 60 gas classes each. No consumables except for occasional filter changes. Can be used as a CWA or TIC detector. Has data logging capability and is capable of networking. 

Colorimetric detectors are usually specifically developed for certain groups of compounds that nndergo similar chemical reactions. Therefore, they are usually less prone to interference compared to other types of generic detection technologies. The downside is that reactions require time and manipulation, and different reactions are required to detect different types of compounds. Therefore, colorimetric detectors are best used to supplement other types of devices that could provide more effective real-time detection of CWA or TIC presence. 

PIDs and FIDs have similar detection capability for VOCs in that the ionization process and signal collection of both are nonselective. Although very useful as VOC detectors, they are quite limited when nsed as field detectors for CWAs. Detection of CWAs can occnr only throngh the nse of response factors equivalent to respective calibration gas. Methane gas and isobntylene are nsed by FID and PID, respectively, as the reference calibration gas. Response factors correlate detector responses calibrated against the reference gases to a known concentration of a given compound. The usefulness of response factors, nnfortunately, is valid only if the sample contained the targeted chemical withont any other infinences (i.e. in a known situation). They are not viable CWA or TIC detectors becanse they do not provide specific... 

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