Medical Aspects of Chemical Warfare (2008) - The Black Vault

Medical Aspects of Chemical Warfaremodifications of the assay for these compounds havebeen developed, and several have been applied tohuman exposure cases. Important factors to considerwhen anticipating using this test are the extent ofexposure and time elapsed since the event. In mostcases, hydrolysis products are not expected to be presentfor more than 24 to 48 hours following exposure;however, one of the most severely poisoned victims ofthe Matsumoto sarin attack had measurable IMPA inthe urine on the seventh day after the incident. In thisparticular case, extremely depressed AChE values, inrange of 5% to 8% of normal, 24 further indicated theextent of exposure (Table 22-2).Assay of Adducts to BiomoleculesThe relatively rapid excretion and short-lived presenceof urinary hydrolysis products imposes timerestrictions for collecting a viable sample. Efforts toincrease the sampling window have taken advantageof the interactions between chemical warfare agentsand biological targets with large molecular weights(adducts to biomolecules), such as proteins. The reactionof chemical agents with large molecules providesa pool of bound compound that can be tested to verifyexposure. Theoretically, the longevity of the markeris consistent with the in-vivo half-life of the targetmolecule, provided that the binding affinity is highenough to prevent spontaneous reactivation. Bindingof nerve agents to ChE targets has been one of theprimary interactions leveraged in assay development.Several assays have been developed based on variationsof this concept.Analytical MethodsPolhuijs et al 29 developed an assay technique basedon observations of earlier findings that sarin-inhibitedChE could be reactivated with fluoride ions. 30–32 Thedisplacement of covalently bound sarin to butyrylcholinesterase(BChE) was accomplished by incubatinginhibited plasma with fluoride to form free enzymeTable 22-2Methods Used to Confirm Human Exposures to Nerve Agents via Assay ofHydrolysis ProductsAgent/Incident Sample Matrix Product Identified Concentration Reported Analytical MethodGB, Tokyo, Japan urine empa, IMPA, MPA NR GC-FPD 1GB, Matsumoto, Japan Urine impa 0.76–0 .01 μg/mL GC-FPD 2mpa0.14–0.02 μg/mLGB, Matsumoto and Tokyo, Serum impa matsumoto (2–135 ng/mL) LC-MS-MS 3,4Japantokyo (2–127 ng/mL)VX, Osaka, Japan Serum empa, diisopro- 1.25 μg/mL GC-MS, GC-MS-MS 5pylaminoethyl 143 ng/mLmethyl sulfideEMPA: ethyl methylphosphonic acidFPD: flame photometric detectionGB: sarinGC: gas chromatographyIMPA: isopropyl methylphosphonic acidLC: liquid chromatographyMPA: methylphosphonic acidMS: mass spectrometryNR: not reportedData sources: (1) Minami M, Hui DM, Katsumata M, Inagaki H, Boulet CA. Method for the analysis of methylphosphonic acid metabolitesof sarin and its ethanol-substituted analogue in urine as applied to the victims of the Tokyo sarin disaster. J Chromatogr B Biomed Sci Appl.1997;695:237–244. (2) Nakajima T, Sasaki K, Ozawa H, Sekjima Y, Morita H, Fukushima Y, Yanagisawa N. Urinary metabolites of sarin in apatient of the Matsumoto incident. Arch Toxicol. 1998;72:601–603. (3) Noort D, Hulst AG, Platenburg DH, Polhuijs M, Benschop H. Quantitativeanalysis of O-isopropyl methylphosphonic acid in serum samples of Japanese citizens allegedly exposed to sarin: estimation of internaldosage. Arch Toxicol. 1998;72:671–675. (4) Polhuijs M, Langenberg JP, Noort D, Hulst AG, Benschop HP. Retrospective detection of exposure toorganophosphates: analyses in blood of human beings and rhesus monkeys. In: Sohns T, Voicu VA, eds. NBC Risks: Current Capabilities andFuture Perspectives for Protection. Dordrecht, Holland, Netherlands: Kluwer Academic Publishers; 1999:513–521. (5) Tsuchihashi H, Katagi M,Nishikawa M, Tatsuno M. Identification of metabolites of nerve agent VX in serum collected from a victim. J Anal Toxicol. 1998;22:383–388.698