Chemical warfare sarin

Discovered in the late 1930s in Germany as improved poisonous insecticides, organophosphorus ChEIs were developed as chemical warfare agents (e.g. sarin, soman, and tabun) and were more recently employed in the 1995 terrorist attack in the Tokyo subway system [5]. 

Chemical warfare agents, such as soman and sarin, sometimes termed nerve gases, are powerful anticholinesterases, which bear some resemblance in structure and properties, to the OP insecticides. A major difference from most insecticides is their high volatility. These agents were possessed by the major powers during World War II, althongh they were never employed in warfare. 

Production, Import/Export, Use, Release, and Disposal. The risk for exposure of the general population to substantial levels of diisopropyl methylphosphonate is quite low. GB (Sarin) and diisopropyl methylphosphonate have not been produced in the United States since 1957, and there is no indication that U.S. production of these chemicals will resume (EPA 1989). No information exists regarding the import or export of diisopropyl methylphosphonate. Diisopropyl methylphosphonate has no known commercial uses, but has been used by the military as a simulant for chemical warfare agents (Van Voris et al. 1987). 

Although the inhibition-based biosensors are sensitive, they are poor in selectivity and are rather slow and tedious since the analysis involves multiple steps of reaction such as measuring initial enzyme activity, incubation with inhibitor, measurement of residual activity, and regeneration and washing. Biosensors based on direct pesticide hydrolysis are more straightforward. The OPH hydrolyzes ester in a number of organophospho-rus pesticides (OPPs) and insecticides (e.g. paraoxon, parathion, coumaphos, diazinon) and chemical warfare agents (e.g. sarin) [53], For example, OP parathion hydrolyzes by the OPH to form p-nitrophenol, which can be measured by anodic oxidation. Rainina... 

Nerve Agent Substances that interfere with the central nervous system. Organic esters of phosphoric acid used as a chemical warfare agent because of their extreme toxicity (tabun-GA, sarin-GB, soman-GD, GF, and VX). All are potent inhibitors of the enzyme, acetylcholinesterase, which is responsible for the degradation of the neurotransmitter, acetylcholine in neuronal synapses or myoneural junctions. Nerve agents are readily absorbed by inhalation and/or through intact skin. 

Unable to provide definitive answers to most of these questions, chemical warfare specialists continued to repeat what we have already heard that a single whiff of a nerve gas such as sarin, or a single drop of a liquid nerve agent such as VX can be fatal. They incorrectly warn us that an enemy can pack enough such poison into a single missile warhead to annihilate thousands of people, perhaps the population of an entire city. They note that even the skin can be penetrated, but then tell us it is even more important to possess an airtight mask. 

Even more reactive towards acetylcholinesterase are the organophosphorus derivatives developed as chemical warfare nerve agents, e.g. sarin. Such compounds react readily with the enzyme and form very stable addition intermediates. It is unusual to see fluoride as a leaving group, as in sarin, but its presence provides a huge inductive effect, thus accelerating the initial nucleophilic addition step (see also Section 13.7). 

Organophosphorsus inhibitors have been developed as insecticides (paraoxon, parathion) and for chemical warfare (soman, tabun, sarin). They are extremely toxic and lethal either by cardiac arrest of general paralysis and subsequent suffocation. 

German Trilons. Extremely toxic Chemical Warfare Agents developed before WWII but never employed. They included Sarin, Soman, Tabun and probably others. See PATR 2510(1958), p Ger 204-L and GA and GB in Vol 2 of Encycl, p C167-R... 

Organophosphate and carbamate cholinesterase inhibitors (see Chapter 7) are widely used to kill insects and other pests. Most cases of serious organophosphate or carbamate poisoning result from intentional ingestion by a suicidal person, but poisoning has also occurred at work (pesticide application or packaging) or, rarely, as a result of food contamination or terrorist attack (eg, release of the chemical warfare nerve agent sarin in the Tokyo subway system in 1995). 

Figure 1 Structures of chemical warfare agents (sarin and soman), simulants (dimethyl methylphosphonate and diisoproyl fluorophosphate), and pesticides (paratliion and diazinon).

Methylphosphonic acid (MPA), a degradation product of gas chemical warfare agents, such as sarin (isopropyl methylphosphonofluoridate), soman or VX (0-ethy I -.S -2-di isopropyl am i noethvl methyl phosphonoth ioate), has been recognized selectively by an MIP chemosensor using potentiometric transduction (Table 6) [181]. The MIP preparation involved co-adsorption, in ethanol, of the methylphosphonic acid (MPA) template and octadecyltrichlorosilane, followed by silanization on the indium-tin oxide (ITO) electrode surface in the chloroform-carbon tetrachloride solution at 0 °C. Subsequently, the electrode was rinsed with chloroform to remove the template. A potential shift due to the presence of MPA was significant as compared to that due to interferants like methyl parathion, dimethoate, phosdrin, malathion, etc. The linear concentration range varied from 50 pM to 0.62 M MPA at LOD as low as 50 pM and an appreciably short response time of 50 s. 

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