Identification Of Chemical Warfare Agents Research Articles

P-Toluenesulfonic Acid–Celite as a Reagent for Synthesis of Esters of Alkylphosphonic Acids under Solvent-Free Conditions

The coupling reaction of alkylphosphonic acids and alcohols on the surface of p-toluenesulfonic acid–Celite under mild and solvent-free conditions gave the corresponding phosphonates in excellent yields. This method provides a useful rapid synthesis of phosphonates for use in the unambiguous identification of chemical warfare agents.

Screening and Identification of Organophosphorus Compounds Related to the Chemical Weapons Convention with 1D and 2D NMR Spectroscopy

Two-dimensional 1H-31P Fast-HMQC was tested for determination of the presence in low concentrations of organophosphorus compounds related to the Chemical Weapons Convention. This method, based on inverse detection, demonstrated high sensitivity and selectivity. Background signals, such as solvent peaks, are suppressed with good efficiency, and organophosphorus compounds present at a concentration level 1-10 microg/mL can be detected within a few hours. In addition, phosphorus-selective one-dimensional 1H-31P HSQC-TOCSY was applied to produce a complete proton spectrum of selected organophosphorus compound from a sample containing intense background resonances. Application of the methods presented in this paper resulted in considerably improved performance of NMR spectroscopy as a complementary technique for screening as well as identification of chemical warfare agents in environmental samples.

Liquid chromatography electrospray tandem mass spectrometric and desorption electrospray ionization tandem mass spectrometric analysis of chemical warfare agents in office media typically collected during a forensic investigation

Most prior analytical studies have dealt with the determination of chemical warfare agents in environmental or biological matrices that would typically be collected following battlefield use or in support of the Chemical Weapons Convention. These methods may be useful for some investigations, but may not be practical for indoor forensic investigations where chemical warfare agent use is suspected. There is a need for analytical methods for chemical warfare agent identification in office media, including flooring, wall surfaces, office fabrics and paper products, which would typically be collected in an office environment during forensic investigations. During this study, typical office environment media were spiked at the 4–20 μg/g level with either a complex munitions grade sample of tabun (GA) or with a standard containing the three nerve agents, sarin (GB), cyclohexyl methylphosphonofluoridate (GF), soman (GD) and the nerve agent simulant, triethyl phosphate (TEP), to evaluate the potentials of liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) for forensic purposes. An emerging technique, desorption electrospray ionization (DESI-MS/MS), was also investigated for the direct determination of TEP, GB and GD sampled onto solid phase microextraction (SPME) fibers exposed to spiked office media. The spiked chemical warfare agents were recovered with varying efficiencies during this study, but in all cases sufficient chemical warfare agent was recovered for mass spectrometric identification purposes. Full high resolution mass spectra were acquired for all the chemical warfare agents in the continuum mode, which typically resulted in mass measurement errors of 0.001 Da or less.

Hollow fiber-mediated liquid-phase microextraction of chemical warfare agents from water

Unambiguous detection and identification of chemical warfare agents (CWAs) and related compounds are of paramount importance from verification point of view of Chemical Weapons Convention (CWC). It requires development of fast, reliable, simple and reproducible sample preparation of CWAs from water which is likely to be contaminated during deliberate or inadvertent spread of CWAs. This work describes development of hollow fiber liquid-phase microextraction (HF-LPME) method for efficient extraction of CWAs (such as sarin, sulfur mustard and their analogues) from water followed by gas chromatography–mass spectrometric analysis. Extraction parameters, such as organic solvent, agitation, extraction time, and salt concentration were optimized. Best recoveries of target analytes were achieved using 1 μL trichloroethylene as extracting solvent, 1000 rpm stirring rate, 15 min extraction time, and 30% NaCl. Excellent precision was observed with less than 7.6% RSD. The limit of detection by HF-LPME was achieved up to 0.1 μg/L at 30% salt concentration.

Surface-enhanced Raman spectroscopy of half-mustard agent

The detection and identification of chemical warfare agents is an important analytical goal. Herein, it is demonstrated that 2-chloroethyl ethyl sulfide (half-mustard, CEES) can be successfully analysed using surface-enhanced Raman spectroscopy (SERS). A critical component in this detection system is the fabrication of a robust, yet highly enhancing, sensor surface. Recent advances in substrate fabrication and in the fundamental understanding of the SERS phenomenon enable the development of improved substrates for practical SERS applications.

On-matrix derivatisation–extraction of precursors of nitrogen- and sulfur-mustards for verification of chemical weapons convention

Development and refinement of sample preparation protocols for retrospective detection and identification of chemical warfare agents (CWAs) and their markers is of paramount importance from verification point of view of chemical weapons convention (CWC). Precursors of nitrogen- and sulfur-mustards (NMPs and SMPs) are polar adsorptive markers of vesicant class of CWAs. Their detection in a given environmental sample may imply past contamination with mustards. For the efficient extraction of NMPs and SMPs from soil, on-matrix derivatisation–extraction (OMDEX) method was developed and optimized. The method involved trifluoroacetylation of analytes on soil itself, followed by extraction with suitable solvent. The extracted samples were analyzed by gas chromatography–mass spectrometry (GC–MS). This virtually single-step sample preparation offered better recoveries of NMPs and SMPs in comparison to conventionally used extraction, evaporation and derivatisation. The best recoveries of analytes were obtained with acetonitrile by OMDEX method. Dynamic linearity range of trifluoroacetylated (TFA) derivatives of NMPs and SMPs was 1–12 μg/L in GC–MS analysis in SIM mode. Repeatability and reproducibility of this technique containing 5 and 10 μg analytes/gm soil was <3.3% and <4.6%, respectively. OMDEX technique was finally applied for the detection of TFA derivatives of NMPs in the soil sample supplied in 16th official proficiency test conducted by OPCW in October 2004.

Application of Single Drop Microextraction for Analysis of Chemical Warfare Agents and Related Compounds in Water by Gas Chromatography/Mass Spectrometry

Retrospective detection and identification of chemical warfare agents (CWAs) is important from the verification point of view of the Chemical Weapons Convention. In the present work, a novel method for determination of CWAs and their markers in water has been described. It is based on a single drop micro extraction (SDME) of analytes and gas chromatography/mass spectrometric identification. Extraction conditions, such as solvent selection, agitation, extraction time, and salt content, were found to have significant influence on SDME. The conditions optimized for extraction of CWAs were 1 microL CH2Cl2/CCl4 (3:1 v/v), 30-min extraction time, 300-rpm stirring rate, and with or without NaCl addition. Under optimized conditions, comparison of SDME, solid-phase microextraction, and liquid-liquid extraction was also made. The limit of detection by SDME ranged from 75 to 10 microg L(-1) at a signal-to-noise ratio of 10:1.

Packed capillary liquid chromatography–electrospray ionization (tandem) mass spectrometry of mustard hydrolysis products in soil

A packed capillary liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method was developed and applied to the identification of mustard hydrolysis products in aqueous extracts of soil. In the first application the LC-ESI-MS/MS method was used to identify thiodiglycol and nine longer chain diols in soil samples taken at different locations and depths from a former mustard storage site as part of an ongoing environmental assessment. Aqueous extracts of the soil samples were analysed by LC-ESI-MS/MS using a quadrupole/time-of-flight tandem mass spectrometer operating with a resolution of 9000. High resolution product mass spectra were acquired for thiodiglycol, the hydrolysis product of mustard and nine other sulfur containing diols, including five longer chain diols that could not be identified during prior LC-ESI-MS analyses. The high resolution LC-ESI-MS/MS method was also incorporated into an analytical approach designed to provide rapid chemical warfare agent identification in cases where the chemical and/or biological warfare agent content of a sample is unknown. A sample handling method involving aqueous extraction of the soil sample in biocontainment level 3 (BL-3), followed by autoclave sterilization of the aqueous extract was developed. Once sterilized, the container and aqueous extract can then be safely manipulated outside of BL-3 in the analytical laboratories and may be analysed for the presence or absence of chemical warfare agents, their hydrolysis products or related compounds by LC-ESI-MS/MS.

Packed capillary liquid chromatography–electrospray ionization (tandem) mass spectrometry of mustard hydrolysis products in soil

A packed capillary liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI-MS/MS) method was developed and applied to the identification of mustard hydrolysis products in aqueous extracts of soil. In the first application the LC–ESI-MS/MS method was used to identify thiodiglycol and nine longer chain diols in soil samples taken at different locations and depths from a former mustard storage site as part of an ongoing environmental assessment. Aqueous extracts of the soil samples were analysed by LC–ESI-MS/MS using a quadrupole/time-of-flight tandem mass spectrometer operating with a resolution of 9000. High resolution product mass spectra were acquired for thiodiglycol, the hydrolysis product of mustard and nine other sulfur containing diols, including five longer chain diols that could not be identified during prior LC–ESI-MS analyses. The high resolution LC–ESI-MS/MS method was also incorporated into an analytical approach designed to provide rapid chemical warfare agent identification in cases where the chemical and/or biological warfare agent content of a sample is unknown. A sample handling method involving aqueous extraction of the soil sample in biocontainment level 3 (BL-3), followed by autoclave sterilization of the aqueous extract was developed. Once sterilized, the container and aqueous extract can then be safely manipulated outside of BL-3 in the analytical laboratories and may be analysed for the presence or absence of chemical warfare agents, their hydrolysis products or related compounds by LC–ESI-MS/MS.

Trace level detection and identification of chemicals related to the chemical weapons convention from complex organic samples

A solid-phase extraction (SPE) method involving selective usage of solvents has been developed for trace level identification of chemical warfare agents (CWAs) present in a complex organic background. The total ion chromatograms obtained from direct gas chromatography–electron ionization mass spectrometric analysis of samples spiked with CWAs in the presence of diesel are very complex and dominated by hydrocarbon peaks and the same after treatment with SPE show distinct peaks corresponding to spiked chemicals. The recovery of samples from SPE is found to be 70–85% at the 10 ppm level.

Integration test of a miniature ExB mass spectrometer with a gas chromatograph for development of a low-cost, portable, chemical-detection system

We present preliminary test results for the integration of a miniature crossed electric and magnetic field mass spectrometer (MS) and a small commercial gas chromatograph (GC). We targeted the experiments to identify design variables for the next generation of field-portable low-cost micro-GC–MS instruments to be developed at Lawrence Livermore National Laboratory for identification of chemical warfare agents (CWAs) and, specifically, to evaluate the potential usage of the commercial version of the compact double-focusing MS (CDFMS) as the detector component.

Mass spectrometric analysis of chemical warfare agents and their degradation products in soil and synthetic samples.

A packed capillary liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for the identification of chemical warfare agents, their degradation products and related compounds in synthetic tabun samples and in soil samples collected from a former mustard storage site. A number of organophosphorus and organosulfur compounds that had not been previously characterized were identified, based on acquired high-resolution ESI-MS data. At lower sampling cone voltages, the ESI mass spectra were dominated by protonated, sodiated and protonated acetonitrile adducts and/or their dimers that could be used to confirm the molecular mass of each compound. Structural information was obtained by inducing product ion formation in the ESI interface at higher sampling cone voltages. Representative ESI-MS mass spectra for previously uncharacterized compounds were incorporated into a database as part of an on-going effort in chemical warfare agent detection and identification. The same samples were also analyzed by capillary column gas chromatography (GC)-MS in order to compare an established method with LC-ESI-MS for chemical warfare agent identification. Analysis times and full-scanning sensitivities were similar for both methods, with differences being associated with sample matrix, ease of ionization and compound volatility. GC-MS would be preferred for organic extracts and must be used for the determination of mustard and relatively non-polar organosulfur degradation products, including 1,4- thioxane and 1,4-dithiane, as these compounds do not ionize during ESI-MS. Diols, formed following hydrolysis of mustard and longer-chain sulfur vesicants, may be analyzed using both methods with LC-ESI-MS providing improved chromatographic peak shape. Aqueous samples and extracts would, typically, be analyzed by LC-ESI-MS, since these analyses may be conducted directly without the need for additional sample handling and/or derivatization associated with GC-MS determinations. Organophosphorus compounds, including chemical warfare agents, related compounds and lower volatility hydrolysis products may all be determined during a single LC-ESI- MS analysis. Derivatization of chemical warfare agent hydrolysis products and other compounds with hydroxyl substitution would be required prior to GC-MS analysis, giving LC-ESI-MS a definite advantage over GC-MS for the analysis of samples containing chemical warfare agents and/or their hydrolysis products.

Rapid Identification of Chemical Warfare Agents by Artificial Neural Network Pruning of Temperature-Programmed Microsensor Databases

Rapid identie cation of three chemical warfare (CW) agents and a CW agent simulant has been achieved by analyzing the responses of an array of four microhotplate conductometric sensors with tin oxide and titanium oxide thin sensing e lms. Analyte concentration values in the range of nmol/mol (ppb) to mmol/mol (ppm) were also determined. Calculating the ratios of the response onset and recovery time constants of the different sensor materials at different temperatures, when operated in the e xed temperature sensing mode, clearly identie ed each CW agent. Training artie cial neural network (ANN) models from an 80-component response database (four sensing e lms at 20 operating temperature steps), obtained in the temperature-programmed sensing operating mode, led to successful individual analyte recognition and four separate agent concentration models to provide the concentrations of the target compounds. Recursive elimination of the less relevant inputs and ANN model re-training identie ed the 5 to 12 inputs that are sufe cient to identify and quantify the CW agents. The information obtained through pruning allows one to reduce the microsensor scan time by 40% to 80% and provides insight into the nature of the most critical gas‐ solid interactions for detection.

Conventional analytical methods for chemical warfare agents

Abstract Analytical methods that are currently used for the detection and identification of chemical warfare agents are reviewed and classified by the number of dimensions of information they provide. Single dimensional sensors target specific compounds or classes of compounds. Although they can be less expensive and more portable than multidimensional sensors, multidimensional sensors detect a broader threat spectrum with greater precision and accuracy. The recommendation for analytical field verification during inspections under the Chemical Weapons Convention (CWC) is to use simple two-dimensional analytical methods, such as gas chromatography (GC) or ion mobility spectrometry (IMS), for on-site screening of chemical weapons (CW) agents or to fully equip a modern, mobile analytical laboratory located in an airplane, which can be moved rapidly throughout the world to each inspection site and provide high-quality analytical data on-site.

Retrospective identification of chemical warfare agents by high-temperature automatic thermal desorption–gas chromatography–mass spectrometry

An automated thermal desorption (ATD)–gas chromatography–mass spectrometry method was developed for the analysis of selected chemical warfare (CW) agents. Suitable methods were developed for analytes of high volatility to low volatility. The less volatile CW agents required the purchase and installation of a high-temperature valve upgrade kit allowing valve temperatures of up to 260°C to be reached. The limit of detection was 50 ng on the tube for most CW agents in full scan. Chloropicrin exhibited some temperature dependence, with detection limits improving as ATD temperatures were decreased below 150°C. A sample storage trial was undertaken to establish the most suitable storage environment for CW agents adsorbed onto Tenax TA. Temperature and time of storage were found to influence recovery of analytes with best recoveries being observed after 1 day storage in a freezer (−12°C). This method was evaluated during a trial of procedures for sampling and identification of chemical agents at Porton Down, UK. Sulfur mustard was detected downwind of a simulated exploded munition.

Application of NMR Spectroscopy to Environmental Analysis: Detection of Trace Amounts of Chemical Warfare Agents and Related Compounds in Organic Extract, Water, and Sand

1H and 31P{1H} NMR spectroscopy were used in the identification of chemical warfare agents and related compounds present in trace amounts in organic extract, water, and sand samples. The work was done as part of an international Trial Proficiency Test of laboratory performance. NMR spectroscopy provided identification of bis(2-chloroethyl)ethylamine (HN-1) in an organic extract and identification of methylphosphonic acid, cyclopentyl methylphosphonate, ethyldiethanolamine, diethylaminoethanol, and bis(N,N-diethylaminoethyl)disulfide in samples of canal water. Supporting evidence was provided for the presence of O-cyclopentyl S-2-(diethylamino)ethyl methylphosphonothiolate in the organic extract and of ethyldiethanolamine and diethylaminoethanol in a sand sample. The sample preparations, experiments, spectral analyses, and results obtained by NMR spectroscopy are described.

Detection of Trace Amounts of Chemical Warfare Agents and Related Compounds in Rubber, Paint, and Soil Samples by 1H and 31P{1H} NMR Spectroscopy

1H and 31P{1H} NMR spectroscopy was used in the identification of chemical warfare agents and related compounds present in trace amounts in rubber, paint, and soil samples. The work was done as part of an international Trial Proficiency Test of laboratory performance. NMR spectroscopy provided identifications of bis(2-chloroethyl) sulfide (mustard), bis(2-chloroethylthio)ethane (sesquimustard), dibenz[b,f][1,4]oxazepine (CR), bis(2-hydroxyethyl) sulfide (thiodiglycol), and cyclohexyl ethylphosphonate, and the presence of cyclohexyl methyl ethylphosphonate, 2-methoxyethyl pinacolyl methylphosphonate, and ethylphosphonic acid was supported. One of the spiking compounds, dithiane 1,4-cyclohexane-1-oxide, was not detected. This report describes sample preparations, experiments, spectral analyses, and the results obtained by NMR spectroscopy.

Enzyme-alterable alkylating agents. I. Synthesis, chemical properties, and toxicities of sulfur mustards containing enzyme-susceptible amide bonds.

Enzyme-alterable alkylating agents. I. Synthesis, chemical properties, and toxicities of sulfur mustards containing enzyme-susceptible amide bonds.

Chemical Detection of War Gases for Civilian Defense

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