Soman separating

As with chemical weapons ingredients, the chemical equipment needed to make chemical warfare agents is commercially available just about anywhere. Certainly, to set up a full-scale poison gas production line, terrorists would need reactors and agitators, chemical storage tanks, containers, receivers, condensers for temperature control, distillation columns to separate chemical compounds, valves and pumps to move chemicals between reactors and other containers. Additionally, ideally the equipment would be corrosion-resistant. For a full-scale mustard gas production plant the price tag would be between 2.5 and 5 million. Approximately 10 million would be required to set up a plant to manufacture tabun, sarin or soman.47 Terrorists, however, can be assumed to forego the scale and the safety precautions that most governments would consider essential for a weapons programme. In fact, standard process equipment or a laboratory set-up of beakers and... 

Branching of the O-alkyl ester chain of organo-phosphorus compounds may introduce an asymmetric center, which together with an asymmetric substituted phosphorus atom creates a number of stereoisomers. Diastereoisomers may even be separated on a conventional capillary GC column. This is, for instance, the case with the nerve gas soman, which usually produces two peaks in a gas chromatogram. Although this is characteristic for identifying soman, it also increases the GC/MS detection limit by a factor of two. 

Isomers of soman were separated by GC on a Chirasil-L-Val column but lacked baseline separation (Benschop et al, 1981, 1985 Li et al., 2003). In contrast, (+)-sarin and (—)-sarin could be completely separated by the same column (Benschop and de Jong, 2001). A recent study presented a modified method using a Chiraldex y-cyclo-dextrin trifluoroacetyl GC-column coupled to an electron impact (EI)-MS which enabled sufficient baseline separation of all four stereoisomers of soman (Smith and Schlager, 1996 Yeung et al, 2008). 

FIGURE 54.2. Typical separation of the stereoisomers of soman and internal standard di3-C(—)P(+)-soman using the 2D-GC configuration. From Trap and Van der Schans (2007), Figures 3 and 4. 

Benschop, H.P., Konings, C.A.G., De Jong, L.PA. (1981). Gas chromatographic separation and identification of the four stereoisomers of 1,2,2-trimethylpropyl methylphosphono-fluoridate (soman). Stereospecificity of in vitro detoxification reactions. J. Am. Chem. Soc. 103 4260. 

Tabun has a stereogenic (chiral) phosphoms atom and exists as a pair of enantiomers. A gas chromatograph study of the enantiomers of tabun has been reported (Degenhardt et al., 1986). Separation was achieved through the use of bis[(l/f)-3-(heptafluorobutyryl-camphorate)nickel(II). This approach also separated stereoisomers of both sarin and soman. These authors also reported the stereospecific hydrolysis of racemic tabun using phosphorylphosphatases. They noted the species (mouse, rat, horse) dependence of the hydrolysis. Dilute solutions of tabun in inert solvents (e.g., carbon tetrachloride) exhibit optical stability for months at — 25°C. 

In an attempt to understand the mechanism whereby diazepam was efficacious, Johnson and co-workers (Johnson and Lowndes, 1974 Johnson and Wilcox, 1975) showed diazepam to counteract the over-activity normally associated with skeletal and heart muscle following soman intoxication. It was also shown, however, that diazepam enhances the respiratory depression produced by soman in the pentobarbitone-anaesthetized rabbit. Boskovid (1981) found that atropine and diazepam increased approximately threefold the survival time of rats poisoned with soman, when given 1 min after poisoning. In addition, there are several pharmacodynamic studies of oximes by the same author, in which diazepam (and frequently atropine) were included, but it is often difficult to separate out the effects of the diazepam from the other drugs used (e.g. BoSkovid etal, 1984). 

Separation of the various stereoisomers of the nerve agents for analytical purposes became feasible with the advent of optically active coating materials for columns as used in capillary gas chromatography (GC) and in high performance liquid chromatography (HPLC). The complete separation of the four stereoisomers of soman and of the two stereoisomers of sarin with GC on capillary columns is described in Section III. So far, (-1-)- and (-)-VX could not be separated by means of capillary gas chromatography, but HPLC on a so-called Chiralcel OD-H column yields complete separation of the two stereoisomers of this agent. ... 

FIG U RE 2.2 Gas chromatographic separation (left panel) of the four stereoisomers of soman and two deuterated stereoisomers on a Chirasil-L-Val column and (right panel) of the two stereoisomers of sarin (Peaks 2 and 3) and one deuterated stereoisomer (Peak 1) on a CycloDexB column. The deuterated stereoisomers are used as internal standards for quantitation of the stereoisomers. (Left panel from Benschop, H.P, Bijleveld, E.C., Otto, M.F., Degenhardt, C.E.A.M., Van Helden, H.P.M., and De Jong, L.P.A., Ana/. Biochem., 151, 242,... 

Organophosphoms chemical agents are often mixtures of isomers. It is possible to separate, chromatographicaUy, four stereoisomers of soman and enantiomers of sarin and tabun using short capillary columns packed with chiral... 

Enzymatic reaction can be used for the analysis of not only organic phosphorous chemical agents, but also organic phosphorous pesticides and carbamates, as these compounds also inhibit cholinesterase, and can occur together with CWA in field conditions. Therefore, methods have been developed for differentiating cholinesteraseblocking pesticides and organic phosphorous CWA. Ten insecticides and soman and VX were separated on a plate with silica gel. A mixture of dichloroethane and ethyl acetate (9 1) was used as the mobile phase. Analyzed chemicals were identified with selective reactions. Total time of the analysis did not exceed 30 min. 

Tabun, Sarin, Soman, DPP, and VX, organophosphorus warfare compounds, were detected and determined by OPLC in the presence of 20 different types of pesticides such as OC, OP, carbamates, and carbamides. The determination of these compounds was disturbed by the structurally related OP insecticides. The chromatographic separation was studied by two dimensional TLC. The multi-component eluent system was optimiz by the PRISMA model. 

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