title: Quantification of sarin and cyclosarin metabolites isopropyl methylphosphonic acid and cyclohexyl methylphosphonic acid in minipig plasma using isotope-dilution and liquid chromatography- time-of-flight mass spectrometry.
abstract: An analysis method for determining isopropyl methylphosphonic acid (IMPA) and cyclohexyl methylphosphonic acid (CMPA), the metabolic hydrolysis products of toxic organophosphorus nerve agents isopropyl methylphosphonofluoridate (sarin, GB) and cyclohexyl methylphosphonofluoridate (cyclosarin, GF), respectively, has been developed and validated using high-performance liquid chromatography-mass spectrometry with negative ion electrospray ionization with time-of-flight detection (LC-ESI-MS-TOF). The linear range of quantitation was 5 to 125 ng/mL in plasma with a method detection limit of 2 ng/mL for each compound. This method was developed to determine the amount of metabolic hydrolysis that was formed during and after nerve agent exposure in minipigs to account for a major pathway of GB and GF elimination that had not been previously characterized in the bloodstream, particularly during low-level whole-body inhalation experiments. Metabolic hydrolysis accounted for 70% to 90% of the recoverable agent in the bloodstream during exposure, when compared to both unbound and cholinesterase bound agent recovered by fluoride ion reactivation analysis for the same samples. The estimated half-life of IMPA and CMPA in plasma was determined to be 44 and 61 min, respectively. The method utilizes the mass selectivity of LC-ESI-MS-TOF using a bench-top instrument to achieve a detection limit that is consistent with reported LC-MS-MS methods analyzing blood samples.
authors.affiliation: US Army Edgewood Chemical Biological Center, R&T Directorate, Aberdeen Proving Ground, Maryland 21010-5424, USA. ronald.a.evans@us.army.mil
authors.forename: R A
authors.initials: RA
authors.lastname: Evans
authors.forename: E M
authors.initials: EM
authors.lastname: Jakubowski
authors.forename: W T
authors.initials: WT
authors.lastname: Muse
authors.forename: K
authors.initials: K
authors.lastname: Matson
authors.forename: S W
authors.initials: SW
authors.lastname: Hulet
authors.forename: R J
authors.initials: RJ
authors.lastname: Mioduszewski
authors.forename: S A
authors.initials: SA
authors.lastname: Thomson
authors.forename: A L
authors.initials: AL
authors.lastname: Totura
authors.forename: J A
authors.initials: JA
authors.lastname: Renner
authors.forename: C L
authors.initials: CL
authors.lastname: Crouse
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D015415:Biomarkers / Q000097:blood; D002619:Chemical Warfare Agents / Q000032:analysis / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods; D004781:Environmental Exposure / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D006207:Half-Life; D009943:Organophosphorus Compounds / Q000008:administration & dosage / Q000097:blood* / Q000378:metabolism*; D015203:Reproducibility of Results; D012524:Sarin / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D052616:Solid Phase Extraction / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013552:Swine; D013556:Swine, Miniature
chemical_list: D015415:Biomarkers; D002619:Chemical Warfare Agents; D002800:Cholinesterase Inhibitors; D009943:Organophosphorus Compounds; C048760:isopropyl methylphosphonic acid; C073636:cyclohexyl methylphosphonic acid; D012524:Sarin; C053914:cyclohexyl methylphosphonofluoridate