Technical Note pubs.acs.org/ac
Performance of a Novel High Throughput Method for the Determination of VX in Drinking Water Samples Jennifer S. Knaack,‡,† Yingtao Zhou,‡ Matthew Magnuson,§ Erin Silvestri,§ and Rudolph C. Johnson*,‡ ‡
Emergency Response Branch, Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, 4770 Buford Highway, MS F44, Chamblee, Georgia 30341, United States § U.S. Environmental Protection Agency, National Homeland Security Research Center, 26 W. Martin Luther King Drive, MS NG16, Cincinnati, Ohio 45268, United States ABSTRACT: VX (O-ethyl-S-(2-diisopropylaminoethyl) methylphosphonothioate) is a highly toxic organophosphorus nerve agent, and even low levels of contamination in water can be harmful. Measurement of low concentrations of VX in aqueous matrixes is possible using an immunomagnetic scavenging technique and detection using liquid chromatography/tandem-mass spectrometry. Performance of the method was characterized in high-performance liquid chromatography (HPLC)-grade water preserved with sodium omadine, an antimicrobial agent, and sodium thiosulfate, a dechlorinating agent, over eight analytical batches with quality control samples analyzed over 10 days. The minimum reportable level was 25 ng/L with a linear dynamic range up to 4.0 μg/L. The mean accuracies for two quality control samples containing VX at concentrations of 0.250 and 2.00 μg/L were 102 ± 3% and 103 ± 6%, respectively. The stability of VX was determined in five tap water samples representing a range of water quality parameters and disinfection practices over a 91 day period. In preserved tap water samples, VX recovery was between 81 and 92% of the fortified amount, 2.0 μg/L, when analyzed immediately after preparation. Recovery of VX decreased to between 31 and 45% of the fortified amount after 91 days, indicating hydrolysis of VX. However, the preservatives minimized the hydrolysis rate to close to the theoretical limit. The ability to detect low concentrations of VX in preserved tap water 91 days after spiking suggests applicability of this method for determining water contamination with VX and utility during environmental remediation.
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OPNA VX (O-ethyl-S-(2-diisopropylaminoethyl) methylphosphonothioate) is more toxic and environmentally persistent than sarin,9 and thus, there is a concern that it could be intentionally used to contaminate a drinking water system.10 The U.S. Environmental Protection Agency’s (EPA) Water Laboratory Alliance (WLA), part of the Environmental Response Laboratory Network (ERLN), provides a national laboratory network with the capacity and capability to analyze samples from both unintentional and intentional water-related contamination (biological, chemical, and radiochemical contaminants) in support of monitoring, surveillance, response, and remediation. 11 In order to assess the extent of contamination of a drinking water system, accurate and rapid analytical detection methods are needed to analyze samples.2 Limits of detection, data quality objectives and quality control criteria, selectivity for the analyte of interest, and high throughput capability are all important factors to consider when selecting a method to analyze a large number of drinking water samples following a contamination event.12
ince the terrorist attacks of September 11, 2001, awareness of the potential vulnerability of the water infrastructure of the United States has increased.1 Both large and small drinking water and wastewater utilities could potentially be the target of a terrorist attack.1 Intentional contamination of drinking water systems with chemical agents could damage or disrupt drinking water systems and result in illness, disease, or death to the population relying on those water sources.2 Chemical warfare agents (CWAs) have been used in the past for warfare and terrorism,3−5 and the potential for water to be a target matrix for chemical terrorism exists. For instance, during the Iran−Iraq War from 1980 to 1988, Iraq used mustard gas against Iranian troops and was later reported to have used both mustard gas and organophosphorus nerve agents (OPNAs), such as sarin, when they dropped bombs on their own Kurdish civilians in 1988.5,6 Because Iraq was producing these CWAs for warfare,5 there remained a possibility that the agents could be accidentally or intentionally released or disposed of into the waters of the Arabian−Persian Gulf, the primary source of water for countries along the Gulf.7 In June 1994, sarin was released in Matsumoto, Japan, causing approximately 600 exposures and 7 deaths.8 Sarin was detected in a small pond in the area,8 which suggests the potential for contamination of water supplies following a gaseous release of nerve agents. The This article not subject to U.S. Copyright. Published 2013 by the American Chemical Society
Received: December 12, 2012 Accepted: January 24, 2013 Published: February 12, 2013 2611
dx.doi.org/10.1021/ac3036102 | Anal. Chem. 2013, 85, 2611−2616
Analytical Chemistry
Technical Note
the active site of BuChE (FGESAGAAS) and unlabeled and isotopically labeled (13C4D615N) peptides corresponding to VXBuChE adducts were synthesized at Los Alamos National Laboratory (Los Alamos, NM). Monoclonal antibodies against human BuChE were purchased from Thermo Fisher Affinity BioReagents (Rockford, IL). The following materials were purchased from Sigma-Aldrich (St. Louis, MO): triethanolamine buffer solution containing 0.2 M triethanolamine with magnesium ions, ethylenediaminetetraacetic acid (EDTA), and
