High-sensitivity determination of the degradation products of chemical warfare agents by capillary electrophoresis–indirect UV absorbance detection

Capillary electrophoresis coupled with indirect UV absorbance detection was employed for the determination of the chemical warfare agent degradation products: methylphosphonic acid, ethyl methylphosphonate, isopropyl methylphosphonate, and pinacolyl methylphosphonate. Glutamic acid was used as a buffering agent at its isoelectric point (pH 3.22). In its zwitterionic form, glutamic acid does not act as a competing co-anion in the system, thus providing buffering capacity while maintaining high sensitivity. The indirect probe (phenylphosphonic acid) concentration was lowered to 1 mM from the 10 mM in previous literature studies, further enhancing sensitivity. Detection limits of 2 μM were achieved with hydrodynamic injection and up to 100-fold lower using electrokinetic injection. The increased buffering capacity of this system over previous methods led to migration time reproducibility RSD values of 0.18 to 0.22%. This represents a 10-fold improvement in reproducibility over previous studies with comparable or improved sensitivity.     

Derivatisation reactions in the chromatographic analysis of chemical warfare agents and their degradation products

The analysis of chemical warfare agents and their degradation products is an important component of verification of compliance with the Chemical Weapons Convention. Gas and liquid chromatography, particularly combined with mass spectrometry, are the major techniques used to detect and identify chemicals of concern to the Convention. The more polar analytes, and some of the more reactive or highly volatile agents, are usually derivatised to facilitate chromatography, and to impart properties beneficial for detection. This review focuses on derivatisation reactions used in the chromatographic analysis of chemical warfare agents, their degradation products and metabolites.     

Selective enrichment of the degradation products of organophosphorus nerve agents by zirconia based solid-phase extraction

Selective extraction and enrichment of nerve agent degradation products has been achieved using zirconia based commercial solid-phase extraction cartridges. Target analytes were O-alkyl alkylphosphonic acids and alkylphosphonic acids, the environmental markers of nerve agents such as sarin, soman and VX. Critical extraction parameters such as modifier concentration, nature and volume of washing and eluting solvents were investigated. Amongst other anionic compounds, selectivity in extraction was observed for organophosphorus compounds. Recoveries of analytes were determined by GC-MS which ranged from 80% to 115%. Comparison of zirconia based solid-phase extraction method with anion-exchange solid-phase extraction revealed its selectivity towards phosphonic acids. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes were achieved down to 4.3 and 8.5 ng mL(-1), respectively, in selected ion monitoring mode.     

Development of the HS-SPME-GC-MS/MS method for analysis of chemical warfare agent and their degradation products in environmental samples

After World War II approximately 50,000 tons of chemical weapons were dumped in the Baltic Sea by the Soviet Union under the provisions of the Potsdam Conference on Disarmament. These dumped chemical warfare agents still possess a major threat to the marine environment and to human life. Therefore, continue monitoring of these munitions is essential. In this work, we present the application of new solid phase microextraction fibers in analysis of chemical warfare agents and their degradation products. It can be concluded that the best fiber for analysis of sulfur mustard and its degradation products is butyl acrylate (BA), whereas for analysis of organoarsenic compounds and chloroacetophenone, the best fiber is a co-polymer of methyl acrylate and methyl methacrylate (MA/MMA). In order to achieve the lowest LOD and LOQ the samples should be divided into two subsamples. One of them should be analyzed using a BA fiber, and the second one using a MA/MMA fiber. When the fast analysis is required, the microextraction should be performed by use of a butyl acrylate fiber because the extraction efficiency of organoarsenic compounds for this fiber is acceptable. Next, we have elaborated of the HS-SPME-GC-MS/MS method for analysis of CWA degradation products in environmental samples using laboratory obtained fibers The analytical method for analysis of organosulfur and organoarsenic compounds was optimized and validated. The LOD's for all target chemicals were between 0.03 and 0.65 ppb. Then, the analytical method developed by us, was used for the analysis of sediment and pore water samples from the Baltic Sea. During these studies, 80 samples were analyzed. It was found that 25 sediments and 5 pore water samples contained CWA degradation products such as 1,4-dithiane, 1,4-oxathiane or triphenylarsine, the latter being a component of arsine oil. The obtained data is evidence that the CWAs present in the Baltic Sea have leaked into the general marine environment.     

Gas chromatographic separation of the stereoisomers of organophosphorus chemical warfare agents using cyclodextrin capillary columns

The synthesis of the organophosphorus nerve agents sarin, tabun, and cyclohexyl methylphosphonofluoridate (GF) produces a mixture of two stereoisomers except for soman where four stereoisomers are produced. Significant differences exist in the reported toxicity and AChE inhibition rates of the various stereoisomers. This makes the ability to distinguish between the different stereoisomers desirable. Five different derivatized cyclodextrin stationary phases developed for gas chromatography were tested for their ability to resolve the nerve agent stereoisomers using a gas chromatograph interfaced to an atomic emission detector. Of the five columns that we examined, only the 2,6-di-O-pentyl-3-O-trifluoroacetyl or 2,6-di-O-pentyl-3-O-butyryl γ-cyclodextrins were able to successfully resolve all four soman stereoisomers. The elution order for each column was determined using solutions of isolated soman stereoisomers. Enantiomers of sarin, tabun, and GF were resolved with varying degrees of success on the different cyclodextrin stationary phases. Only the butyryl γ-cyclodextrin was able to separate the enantiomers of all four of the nerve agents examined in this study. The capacity (k) and selectivity (α) factors were determined for each of the chemical warfare agents successfully separated. The TNO Prins Maurits Laboratory in the Netherlands has previously developed several different chromatographic methods to resolve the stereoisomers of soman, sarin, and tabun. The advantage of the method described here is that commercially available cyclodextrin gas chromatography columns were used to resolve the stereoisomers, thereby facilitating rapid and routine analysis of organophosphorus nerve agents.     

Rapid screening of precursor and degradation products of chemical warfare agents in soil by solid-phase microextraction ion mobility spectrometry (SPME-IMS)

The use of solid-phase microextraction (SPME) coupled to ion mobility spectrometry (IMS) to detect precursor and degradation products of chemical warfare agents (CWAs) as soil contaminants was investigated. The development and characterization of a system to interface a thermal desorption solid-phase microextraction inlet with a hand held ion mobility spectrometer was demonstrated. The analytes used in this study were diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP), and dimethyl methylphosphonate (DMMP). Two SPME fibers with different stationary phases, 100 μm polydimethylsiloxane (PDMS) and 65 μm polydimethylsiloxane divinylbenzene (PDMS/DVB), were evaluated in this study to determine the optimal fiber and extraction conditions. Better results were obtained with the PDMS fiber. SPME-IMS offered good repeatability and detection of the precursor and degradation products in spiked soil at concentrations as low as 10 μg/g. Sample analysis time was less than 30 min for all the precursor and degradation products.     

Utilisation of separation methods in the analysis of chemical warfare agents

Chemical warfare agents and their degradation products represent a broad group of compounds with different chemical properties (polarity, volatility, thermostability, etc.). These chemicals often have to be detected and determined in complex matrices and therefore highly efficient separation techniques hyphenated to selective and sensitive detectors play an indispensable role. This review offers an overview of selected papers devoted to the title subject. It cannot be considered as a comprehensive literature compilation but should allow the reader to obtain an insight into the application of separation techniques in the important area of human protection and control of chemical weapons.     

Analysis of chemical warfare agents. I. Use of aliphatic thiols in the trace level determination of Lewisite compounds in complex matrices

A series of normal aliphatic thiols have been used to derivatise the chemical warfare agents Lewisites I and II (LI and LII) in hydrocarbon matrices. Varying the chain length of the thiol allowed adjustment of derivative tR by 5.9 min for Lewisite I and 5.3 min for Lewisite II. Linear regression analysis of the chain length of the thiol derivatives of the Lewisite species, and that of a series of normal alkanes against tR, allowed regression models to be developed for each set of compounds. Application of the models allowed thiol reagents to be chosen to give derivatives of Lewisites I and II that eluted before and after the major hydrocarbon contaminant. Limits of detection were comparable for all thiol derivatives analysed by GC-MS in the selection ion monitoring mode (all below 1 microg ml(-1)). The robustness of this approach was illustrated by successful identification of Lewisite I in samples from the Sixth Proficiency Test (organised by the Organisation for the Prohibition of Chemical Weapons, OPCW) in a matrix of 1 mg ml(-1) diesel oil.     

Polyelectrolyte functionalized multi-walled carbon nanotubes as strong anion-exchange material for the extraction of acidic degradation products of nerve agents

Extraction, enrichment and gas chromatography mass spectrometric analysis of degradation products of nerve agents from water is of significant importance for verification of Chemical Weapons Convention (CWC) and gathering forensic evidence of use of nerve agents. Multi-walled carbon nanotubes (MWCNTs) were non-covalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) to afford the cationic functionalized nano-tubes, which were used as solid-phase anionic-exchanger sorbents to extract the acidic degradation products of nerve agents from water. Extraction efficiencies of MWCNTs-PDDA were compared with those of mixed mode anion-exchange (HLB) and silica based strong anion-exchange (Si-SAX) cartridges. Optimized extraction parameters included MWCNTs-PDDA 12 mg, washing solvent 5 mL water and eluting solvent 3 mL of 0.1M aqueous HCl followed by 3 mL methanol. At 1 ng mL(-1) spiking concentration of mono- and di-basic phosphonic acids, MWCNTs-PDDA exhibited higher extraction efficiencies in comparison to Si-SAX and HLB. The limits of detection were achieved down to 0.05 and 0.11 ng mL(-1) in selected ion and full scan monitoring mode respectively; and limits of quantification in selected ion monitoring mode were achieved down to 0.21 ng mL(-1).     

Analysis of chemical warfare agents. II. Use of thiols and statistical experimental design for the trace level determination of vesicant compounds in air samples

Thermal desorption with gas chromatography-mass spectrometry (TD-GC-MS) remains the technique of choice for analysis of trace concentrations of analytes in air samples. This paper describes the development and application of a method for analysing the vesicant compounds sulfur mustard and Lewisites I-III. 3,4-Dimercaptotoluene and butanethiol were used to spike sorbent tubes and vesicant vapours sampled; Lewisite I and II reacted with the thiols while sulfur mustard and Lewisite III did not. Statistical experimental design was used to optimise thermal desorption parameters and the optimum method used to determine vesicant compounds in headspace samples taken from a decontamination trial. 3,4-Dimercaptotoluene reacted with Lewisites I and II to give a common derivative with a limit of detection (LOD) of 260 microg m(-3), while the butanethiol gave distinct derivatives with limits of detection around 30 microg m(-3).     

Determination of nerve agent degradation products in environmental samples by liquid chromatography-time-of-flight mass spectrometry with electrospray ionization

A powerful and rapid method has been developed for the identification and quantitative determination of alkyl methylphosphonic acids, which are the degradation products of nerve agents, using liquid chromatography-time-of-flight mass spectrometry with electrospray ionization. Six alkyl methylphosphonic acids were well separated within 16 min. For quantitative analysis, good linearity, sensitivity and reproducibility were obtained by LC-MS in the selected ion monitoring mode. For unambiguous identification of alkyl methylphosphonic acids, fragment ions were produced by in-source collision induced dissociation (CID), and then exact mass measurement of CID fragment ions was performed. The feasibility of applying this technique for detecting these compounds in spiked environmental waters and soils was demonstrated.     

Determination of diphenylarsinic acid and phenylarsonic acid,the degradation products of organoarsenic chemical warfare agents,in well water by HPLC–ICP‐MS

Diphenylarsinic acid (DPAA) and phenylarsonic acid (PAA), which were degradation products of organoarsenic chemical warfare agents used as sternutatory gas, were detected in the well water at Kamisu, Ibaraki Prefecture, Japan. The standard material of DPAA was synthesized with aqueous arsenic acid and phenylhydrazine in order to determine organic arsenic compounds in well water. The DPAA showed a protonated ion at m/z 263 [M + H]⁺ and a loss of H₂O ion at m/z 245 [M + H ? H₂O]⁺ from protonated ion by the electrospray ionization time‐of‐flight mass spectrometry. The quantitative analysis of DPAA and PAA was performed by high‐performance liquid chromatography inductively coupled plasma mass spectrometry and the system worked well for limpid liquid samples such as well water. Copyright © 2005 John Wiley & Sons, Ltd.     

Application of microcolumn liquid chromatography and capillary electrophoresis with flame photometric detection for the screening of degradation products of chemical warfare agents in water and soil

Microcolumn liquid chromatography (microLC) and capillary electrophoresis (CE) coupled on-line with flame photometric detection (FPD) have been used for the screening of polar breakdown products of chemical warfare agents in water and soil samples, provided during Official Proficiency Tests organized by the Technical Secretariat of the Organization for the Prohibition of Chemical Weapons. CE-FPD is shown to be a powerful and rapid method for the determination of alkylphosphonic acids, which are the breakdown products of organophosphorus nerve agents. Gradient elution microLC-FPD is more sensitive and robust but less rapid in the determination of these compounds. In addition, microLC-FPD can be applied to screen for hydrolysis products of sulfur mustard and its analogues. Both methods can be applied without prior derivatization and are extremely selective. In order to unambiguously identify the relevant compounds, electrospray ionization (tandem) mass spectrometry, gas chromatography-mass spectrometry and nuclear magnetic resonance spectrometry were applied.     

The Cu- and Zn-complex-catalyzed methanolysis of the chemical warfare nerve agents soman,sarin, and VX

The catalytic methanolysis of the chemical warfare nerve agents soman, sarin, and VX was investigated by using Cu or Zn complexes. Although VX withstood decontamination, the decomposition yield being around 96%, the soman and sarin deposited on different surfaces were almost fully destroyed under ambient conditions. The catalytic tests performed on a wide range of contaminated surfaces confirm the activity of the investigated catalytic systems, these complexes being suitable, from an economical point of view, for use in the formulation of a possible decomposition kit with military or civilian applicability.     

Determination of chemical warfare agents and related compounds in environmental samples by solid-phase microextraction with gas chromatography

Solid phase microextraction (SPME) is an increasingly common method of sample isolation and enhancement. SPME is a convenient and simple sample preparation technique for chromatographic analysis and a useful alternative to liquid-liquid extraction and solid phase extraction. SPME is speed and simply method, which has been widely used in environmental analysis because it is a rather safe method when dealing with highly toxic chemicals. A combination of SPME and gas chromatography (GC) permits both the qualitative and quantitative analysis of toxic industrial compounds, pesticides and chemical warfare agents (CWAs), including their degradation products, in air, water and soil samples. This work presents a combination of SPME and GC methods with various types of detectors in the analysis of CWAs and their degradation products in air, water, soil and other matrices. The combination of SPME and GC methods allows for low detection limits depending on the analyte, matrix and detection system. Commercially available fibers have been mainly used to extract CWAs in headspace analysis. However, attempts have been made to introduce new fiber coatings that are characterized by higher selectivities towards different analytes of interest. Environmental decomposition of CWAs leads to the formation of more hydrophilic products. These compounds may be isolated from samples using SPME and analyzed using GC however, they must often be derivatized first to produce good chromatography. In these cases, one must ensure that the SPME method also meets the same needs. Otherwise, it is helpful to use derivatization methods. SPME may also be used with fieldportable mass spectrometry (MS) and GC-MS instruments for chemical defense applications, including field sampling and analysis. SPME fibers can be taken into contaminated areas to directly sample air, headspaces above solutions, soils and water.     

Application of high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy for the analysis of degradation products of V-class nerve agents and nitrogen mustard

The detection and identification of the degradation products of nitrogen mustard and nerve agent VX by high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-UV-SPE-NMR) were demonstrated. The analytes selected for the study were N,N-dimethylaminoethanol (DMAE), N,N-diethylaminoethanol (DEAE), N,N-diisopropylaminoethanol (DIAE) and triethanolamine (TEA). Offline solid-phase extraction (SPE) followed by derivatization was applied to eliminate the interferents and make the analytes amenable for UV detection. Thereafter, chromatographically separated derivatives were trapped on on-line SPE cartridges. They were subsequently eluted and ¹H NMR and COSY spectra were obtained. The overall detection limits of the LC-UV-SPE-NMR method for the mentioned analytes were found to be 18, 23, 25, and 32 mg/L respectively. Applicability of the method to real samples was demonstrated by the analysis of samples provided during the 22nd OPCW official proficiency test. The method gave reproducible NMR spectra devoid of intense background signals.     

Chemometric interpretation of pesticide occurence in soil samples from an intensive horticulture area in north Portugal

An extensive monitoring programme of pesticides was carried out in soil samples from an intensive horticulture area in north of Portugal, putting into practice the needs for increased control of soil quality as far as organic pollution is concerned. The area under investigation was additionally defined as vulnerable to nitrates due to local soil and aquifer characteristics, which might be extended to pesticides contamination. Five sampling sites were selected and soils analysed at three depths in eight sampling campaigns, for the period of 2 years. A stepwise multivariate statistical approach was selected to uncover most relevant patterns inside a complex environmental data matrix. Cluster analysis was applied both to group pesticides and samples, giving a primary and unsupervised overlook of privileged relationships. Clusters of persistent pesticides and selected herbicides were identified, whereas sample classes were also formed and disposed geographically. Thirty eight percent of analysed soils samples fell into one class characterized by low contamination (class 1 in cluster analysis), which is entirely representative of the sampling site no. 1. Afterwards, linear discriminant analysis was applied to identify those pesticides, which had a higher impact in the definition of classes. Finally, factor analysis using a five component model was implemented in order to bring to light the constitution and data variance explained by each of the five main principal components, as well as, their relation to pest management practices. A factor was identified (PC1 – 22% variance) composed of chlorinated pesticides, which was representative of one of the investigated sites indicating its high contamination status. Qualitative main findings and class average concentration values were obtained through this multivariate statistical approach.     

On the semi-quantification of polycyclic aromatic hydrocarbons in contaminated soil by an enzyme-linked immunosorbent assay kit

Polycyclic aromatic hydrocarbons (PAHs) are of environmental concern, for instance when found in contaminated soils at sites where industrial activities have occurred. For efficient screening of such soils, the commercially available enzyme-linked immunosorbent assay (ELISA) kit, the PAH RIS^c® soil test, can be used. However, the site-specific performance may vary due to differences in soil properties and contamination profiles. Hence, in this study we have examined various contributing factors to the total ELISA measurements uncertainties. These factors include contributions from co-extracted (non-target) compounds, the extraction efficiency and differences in cross-reactivity among the target analytes. Reference values were obtained through pressurized liquid extraction (PLE) and gas chromatography coupled to mass spectrometry (GC-MS) analysis. The results showed that the ELISA does not seem to respond to non-target compounds in the soil extracts to any large extent. Furthermore, high molecular weight PAHs were found to be more efficiently extracted with PLE than with methanol agitation, which is used for ELISA. If this, and the cross-reactivity of the individual PAHs, were taken into consideration, the ELISA and GC-MS results were in good agreement.     

LC-PDA and LC-ESI-MS separation and determination of process-related substances arising from stilbene-type fluorescent whitening agents. Application to monitoring of their photodegradation products in industrial effluents and aqueous environmental systems

A simple and rapid gradient elution high-performance liquid chromatographic method using photodiode array and electrospray ionization mass spectrometric detectors was developed for separation and determination of the process-related substances and photodegradation products of stilbenesulfonic acids, viz. 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNSDA), 4-amino-4'-nitrostilbene-2,2'-disulfonic acid (ANSDA), and 4,4'-diaminostilbene-2,2'-disulfonic acid (DASDA) in industrial waste waters. Gradient elution was carried out using ammonium acetate and acetonitrile as mobile phase and an Inertsil-ODS 3V column for separation. The negative-ion electrospray ionization mass spectra containing [M-H]- ions of sulfonic acids allowed molecular mass determination of unknowns and the structures were proposed on the basis of the fragment ions in the MS/MS spectra.     

Optimisation of solid-state urea clathrate formation as a chemical separation method coupled to compound-specific stable carbon isotope analysis

Solid-state urea clathrate formation (SSUCF) as a chemical separation method prior to stable carbon isotope fingerprinting of diesel fuel contaminations was studied. The stable carbon isotope ratios (δ¹³C) of n-alkanes in diesel fuel can be used to trace the origin of a contamination. The accurate measurement of the stable isotopic composition of individual compounds requires baseline separation from any other co-eluting compounds. For this purpose silica gel column chromatography (SGCC) and SSUCF were applied. Detailed optimisation of SSUCF was performed: different activators, clathrate formation temperatures, activator volumes, clathrate formation times and sample capacity were investigated. The main benefits of the developed method are reduced clathrate formation time and increased recoveries for lower molecular weight n-alkanes. The recoveries of the developed SSUCF method ranged between 63 and 100% for C10–C24 n-alkanes with relative standard deviation no more than 7%. The precision of the gas chromatography-isotope ratio mass spectrometry measurement was acceptable with a standard deviation of the δ¹³C values ranging between 0.08 and 0.15‰. The absence of isotopic fractionation was also investigated.

The robustness of the method was tested within a model experiment. Nine different water samples including distilled water, tap water, river water, industrial wastewaters and groundwater samples were spiked with the same diesel fuel. The water samples were extracted with n-hexane and after purification with both SGCC and SSUCF n-alkanes were measured. The δ¹³C values of n-alkanes were found to be similar for all samples. The importance of sample purification prior to compound-specific isotope analysis (CSIA) was also demonstrated within this model experiment by analysing samples from different stages of the sample preparation.

Our results show that the proposed method can remarkably improve the precision of compound-specific stable carbon isotope analysis of n-alkanes originating from diesel contamination of the aquatic environment.