Nerve Agent Degradation Products Research Articles

Simultaneous analysis of degradation products of Novichok agents and conventional nerve agents in human urine by ion chromatography-tandem mass spectrometry using ammonium regeneration solution

An ion chromatography (IC)-tandem mass spectrometry (MS/MS) method to analyze nerve agent degradation products in human urine was developed. Six degradation products of conventional nerve agents and six Novichok agent degradation products were analyzed simultaneously despite their differences in hydrophilicity and acidity. Using ammonium regeneration solution improved the peak shapes greatly compared with the results obtained with the ordinary IC-MS/MS configuration. For urine samples, a simple pretreatment method of dilution with water and ultrafiltration was used. The detection limits of the nerve agent degradation products were sufficiently low (10–250 ng/mL) and the calibration curves showed acceptable linearity. Due to the absence of a derivatization step, throughput was higher than for our previous derivatization-liquid chromatography-MS/MS method.

Synthesis, experimental and molecular dynamics simulation of the ESI-CID spectrum of the nerve agent Novichok analog O-2-methoxyethyl N- [bis(dimethylamino)methylidene]-P-methylphosphonamidate

The comprehensive and accurate analysis of mass spectral data is critical for the unequivocal identification of environmental samples containing compounds short-listed by the Chemical Weapons Convention (CWC). In particular, experiments with nerve agents are limited by the high risks involved in their handling. Therefore, the possibility of studying fragmentation pathways by a theoretical approach is especially welcome. In this work, for the first time, O-2-methoxyethyl N- [bis(dimethylamino)methylidene]-P-methylphosphonamidate, an analog of the Novichok nerve agent A-242, was synthesized employing a one-pot microscale synthesis. Electron ionization (EI) and electrospray ionization (ESI) mass spectra (MS) were measured to provide data for CWC verification purposes. Considering that ESI-MS/MS is a powerful method for analyzing non-volatile, highly polar, and very water-soluble compounds, such as degradation products of nerve agents, we extensively investigated for the first time the ESI-(collision-induced dissociation) CID fragmentation pathways of the selected molecule. For this purpose, molecular dynamics simulations using the Quantum Chemical Mass Spectrometry (QCxMS) method employing the semiempirical electronic structure method GFN2-xTB were compared with Triple Quadrupole electrospray ionization (ESI) experimental spectra in positive ion mode. The base peak of the EI spectrum for this molecule was found to be m/z 151, which strongly suggests a McLafferty +1 (ML+1) rearrangement involving the 2-methoxyethyl moiety. The formation of ion the m/z 106 in the ESI-CID spectrum, according to the simulations, results from the rearrangement involving a transfer of one dimethylamino group to the phosphorus atom, a mechanism that would be difficult to identify without employing theoretical methods.

Analysis of degradation products of Novichok agents in human urine by hydrophilic interaction liquid chromatography–tandem mass spectrometry

PurposeThe detection of hydrolysis products of Novichok agents in biological samples from victims is important for confirming exposure to these agents. However, Novichok agents are new class of nerve agent and there have been only few reports on analyses of Novichok agent degradation products. Here, we developed hydrophilic interaction liquid chromatography (HILIC)–tandem mass spectrometry (MS/MS) methods to detect Novichok agent degradation products in human urine with simple pretreatment and high sensitivity.MethodsA Poroshell 120 HILIC-Z column was used to analyze six Novichok agent degradation products. For urine samples, we used a simple pretreatment method, which consisted of deproteinization with acetonitrile and microfiltration. We calculated the pKa values of the OH groups, the log P values, and the molecular weights to investigate the difference in chromatographic behaviors of the Novichok agent degradation products and the degradation products of conventional nerve agents.ResultsSix Novichok agent degradation products, including N-(bis-(diethylamino)methylidene)-methylphosphonamidic acid (MPGA), which could not be detected by our previous method, could be analyzed with sufficient peak shape and mutual separation. The detection limits of six Novichok agent degradation products were sufficiently low (1–50 ng/mL) and the calibration curves showed sufficient linearity. The physicochemical parameters of Novichok agent degradation products were different from those of conventional nerve agent degradation products, and this explains the difference in chromatographic behaviors.ConclusionSix Novichok agent degradation products were successfully analyzed by HILIC–MS/MS. Due to the absence of a derivatization step, throughput performance was higher than our previous derivatization-liquid chromatography–MS/MS method.

Analysis of degradation products of nerve agents in biological fluids by ion chromatography-tandem mass spectrometry.

The detection of hydrolysis products of nerve agents (alkyl methylphosphonic acids; RMPAs) in biological samples from victims is important to confirm exposure to nerve agents. However, analysis of RMPAs is difficult due to their high hydrophilicity. The aim of this study was to develop ion chromatography-tandem mass spectrometry (IC-MS/MS) methods using commercially available equipment and columns to analyze RMPAs in human urine and serum with high sensitivity and without using complicate techniques. A Dionex IonPac AS11-HC anion-exchange column was used to analyze six RMPAs (MPA, EMPA, IMPA, iBuMPA, CHMPA, and PMPA). For pretreatments of biological fluids, we developed two pretreatment methods (Method 1: dilution and ultrafiltration; Method 2: removal of chloride ions with Ag cartridges). Six RMPAs including highly hydrophilic methylphosphonic acid and ethyl methylphosphonic acid could be analyzed with sufficient retention times and peak shape. The detection limits of RMPAs were improved using Dionex OnGuard II Ba/Ag/H cartridges and MetaSEP IC-Ag cartridges (urine: 0.5-5ng/mL; serum: 1-5ng/mL). These methods were also applied to the test samples for the Organisation for the Prohibition of Chemical Weapons Biomedical Proficiency Tests. RMPAs could be sufficiently analyzed by IC-MS/MS. In addition, the limits of detection were superior to those obtained in our previous study involving LC-MS/MS or derivatization-LC-MS/MS method. For analysis of biological samples, an appropriate pretreatment method can be chosen according to the amount of sample available for analysis and expected RMPA concentrations.

Parallel artificial liquid membrane extraction of organophosphorus nerve agent degradation products from environmental samples

An emerging miniaturized high-throughput microextraction technique named Parallel artificial liquid membrane extraction (PALME) was, for the first time, investigated for the extraction of polar alkyl methylphosphonic acids (AMPAs) that are the degradation products of organophosphorus nerve agents. The effect of the key-parameters of the extraction method (nature of the membrane, of the extraction solvent, of the pH values of both donor and acceptor phases, agitation speed, extraction time, temperature and ionic strength) on the extraction recoveries was studied in spiked pure water samples. This led to extraction recoveries in the range of 25–102% for the 5 targeted analytes from water with enrichment factors in the range of 4.50–42.75.The developed PALME-LC-MS/MS method was first evaluated with spiked pure water. LOQs (S/N ≥ 10) were in the range of 0.009–1.141 ng mL−1, linearity above 0.9973 for all the AMPAs and with RSD values below 11%. This method was then applied on simulated waste water, river water and aqueous soil extracts. The achieved LOQs were in the range of 0.011–1.210, 0.013–1.196 and 0.016–6.810 ng mL−1, respectively. A detailed comparison of the performances of this PALME method with those of a previously developed hollow fiber liquid-phase microextraction methods already applied to AMPAs was done thus allowing to demonstrate the easy transfer of methods from HF-LPME to PALME. Moreover, the high-throughput potential of PALME was revealed since 192 samples were processed in parallel during 120 min (37.5 s/sample).

Analysis of Organophosphorus-Based Nerve Agent Degradation Products by Gas Chromatography-Mass Spectrometry (GC-MS): Current Derivatization Reactions in the Analytical Chemist's Toolbox.

The field of gas chromatography-mass spectrometry (GC-MS) in the analysis of chemical warfare agents (CWAs), specifically those involving the organophosphorus-based nerve agents (OPNAs), is a continually evolving and dynamic area of research. The ever-present interest in this field within analytical chemistry is driven by the constant threat posed by these lethal CWAs, highlighted by their use during the Tokyo subway attack in 1995, their deliberate use on civilians in Syria in 2013, and their use in the poisoning of Sergei and Yulia Skripal in Great Britain in 2018 and Alexei Navalny in 2020. These events coupled with their potential for mass destruction only serve to stress the importance of developing methods for their rapid and unambiguous detection. Although the direct detection of OPNAs is possible by GC-MS, in most instances, the analytical chemist must rely on the detection of the products arising from their degradation. To this end, derivatization reactions mainly in the form of silylations and alkylations employing a vast array of reagents have played a pivotal role in the efficient detection of these products that can be used retrospectively to identify the original OPNA.

Substrate binding mechanism of glycerophosphodiesterase towards organophosphate pesticides

Glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes is a binuclear metallohydrolase, which is capable of catalyzing the hydrolysis of mono-, di-, and tri-ester substrates, including some organophosphate pesticides and degradation products of nerve agents. The GpdQ has attracted recent attention as a promising enzyme for bioremediation. This enzyme utilizes two metal ions located in the α and β sites of the enzyme active site for catalysis and is found to bind to Fe(II) ion preferentially. In this study, we aimed to investigate the binding interactions of three organophosphate pesticides (i.e., profenofos, diazinon and chlorpyrifos) to the GpdQ using computational approaches. Firstly, each pesticide molecule was separately docked into the active site of the GpdQ using molecular docking. Then, 500-ns MD simulations were carried out on the systems without (apo enzyme) and with pesticides bound. The MD results showed that the Feβ binds well with the GpdQ active site in the presence of pesticide. It is also seen that the binding of the pesticide could stabilize the enzyme structure in the active conformation, allowing the substrate to be catalysed into less harmful products. Therefore, the ability of in silico analysis presented here could be informative for enhancing enzyme stability and activity in the future.

A Brief Overview of HPLC-MS Analysis of Alkyl Methylphosphonic Acid Degradation Products of Nerve Agents.

The analysis of degradation products from the classic chemical warfare nerve agents by high-performance liquid chromatography-mass spectrometry has been of much interest in recent years owing to the possible use as a terrorist weapon, and the incidents of chemical weapon usage in recent years in war torn countries. The alkyl methylphosphonic acid degradation products are of a particular interest, and they represent a specific chromatographic technical challenge for use in typical separation systems. Various published methods are summarized in this review and some of the problems associated with the analysis of these compounds are discussed. Future trends of the analysis in this area of research are also considered.

In-situ derivatization and headspace solid-phase microextraction for gas chromatography-mass spectrometry analysis of alkyl methylphosphonic acids following solid-phase extraction using thin film

A headspace solid-phase microextraction (HS-SPME) method, involving solid-phase extraction and in-situ derivatization using polymeric thin film, was developed for the gas chromatography-mass spectrometry (GC–MS) analysis of the degradation products of nerve agents. The solid-phase extraction (SPE) was performed using poly([2-(Methacryloyloxy)ethyl]trimethylammonium chloride) film on a gold plate prepared via surface-initiated polymerization. The extracted analytes were directly derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) on the plate. Various parameters like fiber type, headspace time, temperature, and amount of BSTFA were optimized. Under the optimized conditions, the relative standard deviations (RSDs) were in the range 7.0–13.1% and the limits of detection (LODs) were measured to be between 10 and 20 pg mL−1. The application of the developed method was tested using the 35th Organization for Prohibition of Chemical Weapons (OPCW) proficiency test sample.

Solid-phase extraction of nerve agent degradation products using poly[(2-(methacryloyloxy)ethyl)trimethylammonium chloride] thin films

In this study, a simple solid-phase extraction (SPE) technique was developed to extract organophosphonic acids as degradation products of nerve agents from aqueous samples for identification by instrumental analyses such as FT-IR, TOF-SIMs and GC-MS. To selectively extract the organophosphonic acids, we synthesized an anion exchange polymer film on a gold plate using surface-initiated controlled radical polymerization with 2-[(methacryloyloxy)ethyl]trimethylammonium chloride. Extraction of the organophosphonic acids onto the plates was successfully confirmed by polarized angle fourier transformation-infra red (FT-IR) spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry analyses. The limit of detection of the developed SPE method satisfied the detection limit of Chemical Warfare Agents verification criteria by FT-IR analysis. After optimization, the detection limit values were found to be between 0.1 and 0.4 µg mL−1, and the recovery ranged from 50% to 110% in aqueous solution containing various interference. In addition, the SPE process was successfully applied to the detection of pinacolyl methylphosphonic acid, the degradation product of soman, in the 35th Organization for Prohibition of Chemical Weapons proficiency test sample.

Analysis of degradation products of nerve agents via post-pentafluorobenzylation liquid chromatography-tandem mass spectrometry

In the work reported here, a screening procedure was developed for the detection and identification of RMPAs (nerve agent degradation products) after pentafluorobenzylation using liquid chromatography-tandem mass spectrometry (LC–MS/MS). With this method, all RMPAs, including highly hydrophilic types such as methylphosphonic acid (MPA) and ethyl methylphosphonic acid (EMPA), were sufficiently retained in commonly used reversed-phase columns (retention times: 15.7 and 11.0 min.), and the presence of RMPAs was determined more efficiently than with the conventional direct LC–MS/MS method. The detection limits of RMPAs using this approach (<33 ng) were mostly superior to those observed with direct LC–MS/MS (<74 ng) and gas chromatography-mass spectrometry (GC–MS) after pentafluorobenzylation (<1.1 μg). The applicability of newly developed method toward real samples was evaluated via recovery tests involving urine/serum and wipe tests on various surfaces.

NMR chemical shift and J coupling parameterization and quantum mechanical reference spectrum simulation for selected nerve agent degradation products in aqueous conditions.

The spectral parameters of selected nerve agent degradation products relevant to the Chemical Weapons Convention, namely, ethyl methylphosphonate, isopropyl methylphosphonate, pinacolyl methylphosphonate and methylphosphonic acid, were studied in wide range of pH conditions and selected temperatures. The pH and temperature dependence of chemical shifts and J couplings was parameterized using Henderson-Hasselbalch-based functions. The obtained parameters allowed calculation of precise chemical shifts and J coupling constants in arbitrary pH conditions and typical measurement temperatures, thus facilitating quantum mechanical simulation of reference spectra in the chosen magnetic field strength for chemical verification. Copyright © 2017 John Wiley & Sons, Ltd.

Liquid chromatography-tandem mass spectrometry determination of the degradation products of V-type nerve agnents, N,N-dialkylaminoethanesulfonic acids

Degradation products of V-type nerve agents are important markers of these toxic chemical warfare agents, hence their detection and identification is of high importance from verification point of view of Chemical Weapons Convention (CWC). We focused on detailed investigation of fragmentation of N, N-dialkylaminoethanesulfonic acids, degradation products of V-type nerve agents using liquid chromatography-tandem mass spectrometry (LC−MS/MS), a LCQ Deca XP max ion trap mass spectrometer via an electrospray ionization in ESI mode. Capillary and tube lens voltages were optimized to give maximum response to m/z 210 [M + H]+ ion of N,N-diisopropylaminoethanesulfonic acid. The main fragmentation pathways are loss of alkyl groups attached to the nitrogen atoms. Within the aims of CWC, LC−ESI-MSn represents an important tool to control the production of prohibited compounds among others due to a possibility of easy monitoring of their content in environmental matrices. The knowledge of the fragmentation pathway will be useful for the unambiguous identification of degradation products of V-type nerve agents in human urine matrices as well as environmental matrices in the Organization for the Prohibition of Chemical Weapons proficiency test.

Single vial sample preparation of markers of nerve agents by dispersive solid-phase extraction using magnetic strong anion exchange resins

A sample preparation method involving extraction, enrichment and derivatization of acidic degradation products of nerve agents was developed using magnetic strong anion exchange resins (MSAX). The method was performed in a single vial involving magnetic dispersive solid phase extraction (MDSPE). Analytes were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) in the presence of resins. MSAX were custom synthesized using Fe3O4 nanoparticles as core, 4-vinylpyridine-co-divinylbenzene as polymer shell and quaternary pyridinium function as anion-exchanger. Hydroxide ions were the counter-anions of MSAX to effectively capture the acidic alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs). Quantitative measurements of analytes were performed in the selected ion monitoring mode of GC–MS. Full scan mode of analysis was followed for identifications. Under the optimized conditions analytes were recovered in the range of 39.7–98.8% (n=3, relative standard deviations (RSD) from 0.3 to 6.5%). Limits of detection (LODs) were in the range of 0.1–1.1ngmL−1; and the linear dynamic range was 5–1000ngmL−1 with r2 of 0.9977–0.9769. Applicability of the method was tested with rain-, tap-, muddy-water and Organization for Prohibition of Chemical Weapons (OPCW) Proficiency Test samples.

Rapid screening and determination of nerve agent metabolites in human urine by LC-MS/MS

Qualitative screening procedures have been developed for the rapid detection and identification of the metabolites of nerve agents in the urine samples and extracts using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The combination of negative electrospray ionization (ESI) using a C18 column and water-methanol mobile phase modified with ammonium formate provides a rapid screening procedure for nerve agent degradation products with limit of detection of 1 ng/mL in the precursor-ion analysis. Also, determination of the alkyl methylphosphonic acids was carried out by the SRM scan mode with the limit of detection of 0.1 ng/mL. These procedures will be applicable to the trace analysis of metabolites of nerve agents in human urine matrices in the Organisation for the Prohibition of Chemical Weapons (OPCW) proficiency test.

Solid supported in situ derivatization extraction of acidic degradation products of nerve agents from aqueous samples

This study deals with the solid supported in situ derivatization extraction of acidic degradation products of nerve agents present in aqueous samples. Target analytes were alkyl alkylphosphonic acids and alkylphosphonic acids, which are important environmental signatures of nerve agents. The method involved tert-butyldimethylchlorosilane mediated in situ silylation of analytes on commercially available diatomaceous solid phase extraction cartridges. Various parameters such as derivatizing reagent, its concentration, reaction time, temperature and eluting solvent were optimized. Recoveries of the analytes were determined by GC–MS which ranged from 60% to 86%. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 78 and 213ngmL−1 respectively, in selected ion monitoring mode. The successful applicability of method was also demonstrated on samples of biological origin such as plasma and to the samples received in 34th official proficiency test conducted by the Organization for Prohibition the of Chemical Weapons.

Development of a New Method for the Identification of Degradation Products of V-Type Nerve Agents by Liquid Chromatography–Tandem Mass Spectrometry

Degradation products of V-type nerve agents are important markers of these toxic chemical warfare agents; hence their detection and identification are of high importance from verification point of view of Chemical Weapons Convention. The new analytical technique using quantitation-enhanced data-dependent (QED) method has been developed for the analysis of the degradation products, 2-(N,N-dialkylamino)ethanesulfonic acids of V-type nerve agents, by using liquid chromatography-tandem mass spectrometry (Thermo-Scientific Vantage triple stage quadrupole mass spectrometer, Thermo Finnigan Surveyor, San Jose, CA, USA) via an atmospheric pressure ionization source/interface operated in eletrospray ionization mode. With a single analytical run, we could perform the quantitative analysis of the 2-(N,N-dialkylamino)ethanesulfonic acids by the selected reaction monitoring scan mode with limit of detection at 0.1 ng/mL and identify their isomeric compounds by product ion scan mode, simultaneously. The QED method will be applicable to the trace analysis of degradation products of V-type nerve agents in the environmental matrices in the Organisation for the Prohibition of Chemical Weapons proficiency test.

Trace determination of primary nerve agent degradation products in aqueous soil extracts by on-line solid phase extraction–liquid chromatography–mass spectrometry using ZrO2 for enrichment

A method for determination of the primary nerve agent degradation products ethyl-, isopropyl-, isobutyl-, cyclohexyl- and pinacolyl methylphosphonic acid in aqueous soil extracts has been developed utilizing on-line solid phase extraction-liquid chromatography and mass spectrometry (SPE–LC–MS). Four different stationary phases (ZrO2, TiO2, polymeric mixed mode anion exchange and porous graphitic carbon) were investigated for their suitability as SPE materials in the on-line SPE–LC–MS setup. Zirconium dioxide was chosen due to its high affinity for the alkyl methylphosphonic acids (AMPAs), and its compatibility with LC–MS. Aqueous soil extracts were acidified with 0.1% acetic acid and aliquots of 300μL were injected on a 2mm×10mm ZrO2 column. Separation of the analytes was performed on a reversed phase column with acetonitrile/water gradient and 15mM ammonium acetate. Method validation was performed with the analytes added to an aqueous extract of a loam soil, and the AMPAs could be determined at concentrations as low as 0.05–0.5μgL−1. The method was linear (R2>0.995) from the limit of quantification (LOQ) to 100×LOQ, and the within assay repeatability was below 10% and 5% relative standard deviation at LOQ and 50×LOQ, respectively. The developed method was employed for determination of the AMPAs which had been added to the aqueous extracts of five different soil types from cultivated and uncultivated areas. The obtained recoveries showed that the analytes could be determined at the sensitivities achieved in the method validation in four of the extracts. For the first time, we have demonstrated a method capable of detecting primary nerve agent degradation products at sub ppb levels in the aqueous extracts of various soils. The method requires no sample preparation after soil extraction other than pH adjustment of the aqueous extract.

Detection of Nerve Agents Using Proton Transfer Reaction Mass Spectrometry with Ammonia as Reagent Gas

The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS.

New Techniques for Nerve Agent Oxidation Products Determination in Environmental Water by High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) and Capillary Electrophoresis (CE) with Direct Ultraviolet (UV) Detection

This work represents two approaches of the determination of V-gases that are stable oxidative products in the environment. Four N,N-(dialkyl)aminoethanesulfonic acids: methyl-, ethyl-, n-propyl- and iso-propyl- (DMT, DET, DPT, and DIT, respectively) which are known as oxidative degradation products (DPs) of nerve agents were determined in seven different natural water samples using high-performance liquid chromatography-mass spectrometry (HPLC-MS) and capillary electrophoresis (CE) with direct ultraviolet (UV) detection (CE-UV). Linear response ranges were approximately two orders of magnitude for these four compounds. Limits of detection of these substances were 0.015–0.025 mg/L for HPLC-MS and 1.5–2 mg/L for CE-UV determination. Successful development of the technique may lead to a simple sensor for V-gases DPs that could be implemented and used at sensitive locations throughout the world. Forensic analysis of DMT, DET, DPT, and DIT as specific markers of different types of V-gases performed by these two approaches is allowing to track the source of the nerve agents released into environment.