Chemical warfare agent detecting techniques

Various techniques have been developed for the detection of CWAs (see Table 14.6, which shows the most important detection techniques). Among the various detection techniques, the methods most highly recommended are the use of an ion mobility spectrometer (IMS), semiconductors, and SAW-type devices. 

The ion mobility spectrometry detection technique was first developed in 1965 by the Franklin GNO Corporation. It has become a representative tool for the detection of CWA. Using this instrument, the types and concentrations of agents can be checked in real time. 

One of most recommended methods for the detection of CWAs is the semiconducting device. There are two main types of semiconducting devices Sn02 and ZnO. Among Sn02 devices, there are several different types which can be differentiated according to the thickness and size, such as thick-film, thin-film, and micro. Although different, these types of sensor actually have 

Photoionization Rapid response. Sensitive to organics Poor specificity 

Paper tape Very specific to certain compounds Requires frequent replacement 

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Concerns over possible terrorist use, continued interest by the defense community and the requirements of a verifiable CWC, have driven the development and application of analytical methods for the detection, characterization, and confirmation of chemical warfare agents. Analytical techniques play an important role in this process as sampling and analysis will be conducted to ensure treaty compliance, to investigate allegations of use, and to verify the use of these weapons for forensic purposes. 

There have been many quite useful discoveries in chemistry and chemical engineering over the years that have been used for detection applications. The first example is plasma chromatography, otherwise known as ion mobility spectrometry. In the 1980s this technique became the method of choice for detecting chemical warfare agents and was used by soldiers in Desert Storm with unfortunate results. Official reports tell that the rate of false alarms for these instruments was so high that soldiers became desensitized to real hazards. One infantry battalion eventually turned their alarms off. Much of the Gulf War Syndrome may well have been caused because ion mobihty spectrometry was oversold as a detection technique. 

Toxic hazards never seem as acute as other hazards in the ordnance industries, and the prevailing habits of cleanliness and orderliness go a long way toward their amelioration. The current emphasis on the maintenance of environmental standards have placed additional requirements on the control of effluent gas and liq process streams. The care now being exercised is evidenced by new analytical techniques for the detection of trace contaminants such as the presence of TNT and other aromatic nitrates in the soli and in the ground w (Ref 43), New techniques of detoxification have been developed using microwave plasma oxidation of aromatic compds, heavy metal compns and chemical warfare agents (Refs 65 81)... 

Figure 16.7 Ion mobility spectrometer. The ions are admitted into the analyser tube hy controlling the polarity of the entry grid. Below, an example of a recording obtained from gaseous compounds. Armies in many countries use this technique for the detection of chemical warfare agents.

Chemical warfare agents (CWAs) are known to be highly dangerous for human health because of their fatal toxicity, colorlessness and toxicity. Therefore, fast and selective detection of CWAs is essential to protect human beings and animals. In this chapter, properties of CWAs and various detecting techniques for CWAs were introduced in detail. 

Several review papers on the application of ion mobility spectrometry (IMS) and differential mobility spectrometry (DMS) for detection of chemical warfare agents (CWAs) and their simnlants have been published during the last decade. " The comprehensive review by Sferopoulos on detector technologies and commercial devices for detection of CWAs is especially noteworthy as it surveyed all the different techniques and included a chapter on IMS-based instrumentation. ... 

Rapid detection of chemical warfare agents in the field is essential. However, reliable analytical techniques such as gas or liquid chromatography are not suitable for routine use out of the laboratory. One method that has been investigated makes use of the release of HF from the hydrolysis of a fiuorophosphonate compound (e.g. Sarin). The reaction is catalysed by a copper(II) complex containing the MezNCHzCHzNMez ligand ... 

Ion mobility spectrometry (IMS) is now a well-established analytical technique that is employed throughout the world for the detection of explosives, drngs, and chemical warfare agents. The predominant approach is based on the nse of a drift cell in which ions migrate through a counter flowing bnffer gas in the presence of a low electric field. Separation of ions takes place as a resnlt of interactions between these ions and the buffer gas, and depends on the mass, charge, and shape of the ion. Because the drift cell was employed in the first ion mobility (IM) approach used (and is still the most common), the use of the drift cell in this manner is often referred to as IMS. In discussions of the development of the field of IM, it would be prudent to differentiate this experimental technique in which the drift cell is used from other... 

Capillary column GC-MS/MS offers the analyst the potential for highly specific, sensitive detection of chemical warfare agents as this technique significantly reduces the chemical noise associated with complex biological or environmental sample extracts. The specificity of product scanning with moderate sector resolution, as well as the specificity of ammonia Cl, was demonstrated with a hybrid tandem mass spectrometer during analysis of painted panel samples circulated during an international round robin verification exercise. 

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