Assay of the chiral organophosphate, soman, in biological samples
bookPart
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 phosphoryl-phosphatases. 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 (i) acidification to pH 4.2 at 0[ddot]C to suppress hydrolysis by phosphoryl-phosphatases, (ii) 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 (iii) 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.
For work-up of the four stereoisomers from rat blood the sample is first stabilized by (i) acidification to pH 4.2 at 0[ddot]C to suppress hydrolysis by phosphoryl-phosphatases, (ii) 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 (iii) 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.
TNO Identifier
115742
ISBN
9781003764427
Publisher
Gordon and Breach Science Publishers
Source title
Chemistry and Fate of Organophosphorus Compounds
Editor(s)
Merian, E.
Frei, R.W.
Lawrence, J.F.
Brinkman, U.A.T.
Frei, R.W.
Lawrence, J.F.
Brinkman, U.A.T.
Place of publication
S.l.
Pages
187-205
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