Assay of the chiral organophosphate, soman, in biological samples.
The anticholinesterase, soman, (CH3)3CC(H)CH3O(CH3)P(O)F, consists of four stereoisomers assigned as C(+/-)P(+/-)-soman in which C stands for chirality in the pinacolyl moiety and P for chirality at phosphorus. The four stereoisomers are separated by gas chromatography on an optically active Chirasil-Val column, synthesized and coated in house, or on a Chirasil-Val column identical with the commercially available column when combined with a Carbowax 20M column. This method in combination with an assay based on acetylcholinesterase inhibition shows that the two isomers which do not have anticholinesterase activity, i.e. C(+/-)P(+/-)-soman, are rapidly degraded in rat blood due to hydrolysis by phosphorylphosphatases. Epimeric soman isomers, e.g. C(+/-)P(-)-soman, can be separately assayed on a Carbowax or a CPSil 8 column, using 2H-labeled soman isomers as internal standards. 2H-labeled soman stereoisomers serve as internal standards in GC-assay of all four stereoisomers on Chirasil-Val. For work-up of the four stereoisomers from rat blood the sample is first stabilized by acidification to pH 4.2 at 0 degree C to suppress hydrolysis by phosphorylphosphatases, addition of aluminum ions for complexation of fluoride ions to prevent regeneration of C(+/-)P(-)-soman by free fluoride ions from soman-inhibited carboxylesterase, and addition of (CH3)3CCH2O(CH3)P(O)F to occupy covalent binding sites for C(+/-)P(-)-soman, before extraction with a Sep-Pak C18 cartridge and elution with ethyl acetate. Using a splitless or on-column injection technique and alkali flame ionization detection, the minimum detectable concentration is 30 pg/3-ml blood sample.
D000818:Animals; D002849:Chromatography, Gas; D005459:Fluorides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012999:Soman / Q000097:blood* / Q000302:isolation & purification; D013237:Stereoisomerism
D012999:Soman; D005459:Fluorides