title: Quantification of VX vapor in ambient air by liquid chromatography isotope dilution tandem mass spectrometric analysis of glass bead filled sampling tubes.
abstract: An analysis method has been developed for determining low parts-per-quadrillion by volume (ppqv) concentrations of nerve agent VX vapor actively sampled from ambient air. The method utilizes glass bead filled depot area air monitoring system (DAAMS) sampling tubes with isopropyl alcohol extraction and isotope dilution using liquid chromatography coupled with a triple-quadrupole mass spectrometer (LC/MS/MS) with positive ion electrospray ionization for quantitation. The dynamic range was from one-tenth of the worker population limit (WPL) to the short-term exposure limit (STEL) for a 24 L air sample taken over a 1 h period. The precision and accuracy of the method were evaluated using liquid-spiked tubes, and the collection characteristics of the DAAMS tubes were assessed by collecting trace level vapor generated in a 1000 L continuous flow chamber. The method described here has significant improvements over currently employed thermal desorption techniques that utilize a silver fluoride pad during sampling to convert VX to a higher volatility G-analogue for gas chromatographic analysis. The benefits of this method are the ability to directly analyze VX with improved selectivity and sensitivity, the injection of a fraction of the extract, quantitation using an isotopically labeled internal standard, and a short instrument cycle time.
authors.affiliation: Analytical Toxicology Branch, RDCB-DRT-T, US Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, Maryland 21010-5424, USA. ronald.a.evans@us.army.mil
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Evans
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Smith
authors.forename: Nam-Phuong
authors.initials: NP
authors.lastname: Nguyen
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Crouse
authors.forename: Charles L
authors.initials: CL
authors.lastname: Crouse
authors.forename: Steven D
authors.initials: SD
authors.lastname: Norman
authors.forename: E Michael
authors.initials: EM
authors.lastname: Jakubowski
mesh_terms: D000388:Air; D002853:Chromatography, Liquid / Q000379:methods*; D004784:Environmental Monitoring; D005898:Glass / Q000737:chemistry*; D008863:Microspheres; D008958:Models, Molecular; D008968:Molecular Conformation; D009946:Organothiophosphorus Compounds / Q000032:analysis* / Q000737:chemistry*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013696:Temperature; D014835:Volatilization
chemical_list: D009946:Organothiophosphorus Compounds; C009680:VX-agent