No abstract

Extraction and identification of lethal nerve agents and their markers in complex organic background have a prime importance from the forensic and verification viewpoint of the Chemical Weapons Convention (CWC). Liquid-liquid extraction with acetonitrile and commercially available solid phase silica cartridges are extensively used for this purpose. Silica cartridges exhibit limited applicability for relatively polar analytes, and acetonitrile extraction shows limited efficacy toward relatively nonpolar analytes. The present study describes the synthesis of polymeric sorbents with tunable surface polarity, their application as a solid-phase extraction (SPE) material against nerve agents and their polar as well as nonpolar markers from nonpolar organic matrices. In comparison with the acetonitrile extraction and commercial silica cartridges, the new sorbent showed better extraction efficiency toward analytes of varying polarity. The extraction parameters were optimized for the proposed method, which included ethyl acetate as an extraction solvent and n-hexane as a washing solvent. Under optimized conditions, method linearity ranged from 0.10 to 10 μg mL ( r = 0.9327-0.9988) for organophosphorus esters and 0.05-20 μg mL ( r = 0.9976-0.9991) for nerve agents. Limits of detection (S:N = 3:1) in the SIM mode were found in the range of 0.03-0.075 μg mL for organophosphorus esters and 0.015-0.025 μg mL for nerve agents. Limits of quantification (S:N = 10:1) were found in the range of 0.100-0.25 μg mL for organophosphorus esters and 0.05-0.100 μg mL for nerve agents in the SIM mode. The recoveries of the nerve agents and their markers ranged from 90.0 to 98.0% and 75.0 to 95.0% respectively. The repeatability and reproducibility (with relative standard deviations (RSDs) %) for organophosphorus esters were found in the range of 1.35-8.61% and 2.30-9.25% respectively. For nerve agents, the repeatability range from 1.00 to 7.75% and reproducibility were found in the range of 2.17-6.90%.

The strict monitoring and precise measurements of chemical warfare agents (CWAs) in environmental and other complex samples with high accuracy have great practical significance from the forensic and Chemical Weapons Convention (CWC) verification point of view. Therefore, this study was aimed to develop an efficient extraction and enrichment method for identification and quantification of toxic agents, especially with high sensitivity and multidetection ability in complex samples. It is the first study on solid-phase extraction (SPE) of CWAs and their related compounds from hydrocarbon backgrounds using covalent triazine-based frameworks (CTFs). This nitrogenrich CTF sorbent has shown an excellent SPE performance toward sample cleanup by selective elimination of hydrocarbon backgrounds and enrich the CWC related analytes in comparison with the conventional and other reported methods. The best enrichment of the analytes was found with the washing solvent (1 mL of n-hexane) and the extraction solvent (1 mL of dichloromethane). Under the optimized conditions, the SPE method had good linearity in the concentration range of 0.050−10.0 μg mL −1 for organophosphorus esters, 0.040− 20.0 μg mL −1 for nerve agents, and 0.200−20.0 μg mL −1 for mustards with correlation coefficients (r 2 ) between 0.9867 and 0.9998 for all analytes. Limits of detection (S/N = 3:1) in the SIM mode were found to be in the range of 0.015−0.050 μg mL −1 for organophosphorus esters, 0.010−0.030 μg mL −1 for nerve agents, and 0.050−0.100 μg mL −1 for blister agents. Limits of quantification (S/N = 10:1) were found in the range of 0.050−0.200 μg mL −1 for organophosphorus esters, 0.040−0.100 μg mL −1 for nerve agents, and 0.180−0.350 μg mL −1 for blister agents in the SIM mode. The recoveries of all analytes ranged from 87 to 100% with the relative standard deviations ranging from 1 to 8%. This method was also successfully applied for the sample preparation of 1 H NMR analysis of sulfur and nitrogen mustards in the presence of hydrocarbon backgrounds. Therefore, this SPE method provides the single sample preparation for both NMR and GC−MS analyses. KEYWORDS: triazine-based covalent organic framework, solid-phase extraction, chemical warfare agents, hydrocarbon backgrounds, organic samples, GC−MS and 1 H NMR analysis

Extraction of vesicant class of chemical warfare agents (CWAs) such as sulfur mustard and nitrogen mustards from the environmental matrices is of prime importance, from a forensic and verification viewpoint of the Chemical Weapons Convention (CWC). For extraction of Convention Related Compounds from nonpolar organic medium, commercially available silica cartridges are used extensively, but silica cartridges exhibit limited efficiency toward vesicant classes of compounds. It is expected that sulfur mustard being nonpolar does not retain sufficiently on silica surface, and nitrogen mustards (being basic) are strongly adsorbed on acidic silica surface, resulting in their poor recoveries. Contrary to the expected higher recovery of sulfur mustard over nitrogen mustards, it was observed that the recovery of sulfur mustard was lower than that of nitrogen mustards with the silica based sorbent. The reason for this typical behavior of these agents on silica was investigated. This study was aimed to develop an analytical method for efficient extraction and enrichment of sulfur and nitrogen mustards from hydrophobic matrices. In this work, the polymeric sorbent was synthesized with polar methacrylic acid (MAA) as monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker and used for solid phase extraction (SPE) of sulfur mustard and nitrogen mustards. The extraction efficiency of the polymeric sorbent was optimized and compared with that of silica cartridges. Both classes of analytes were recovered in good amounts from the polymeric sorbent compared to silica. The extraction parameters were optimized for the proposed method which included extraction solvent ethyl acetate and washing solvent n-hexane (1 mL). The recoveries of the analytes ranged from 75 to 87% with relative standard deviations (RSDs) lower than 9%. The limit of detection (LOD) was found to be in the range of 0.075-0.150 μg mL, and limit of quantification (LOQ) was >0.25 μg mL. The linear dynamic range of optimized method was found to be 0.50-20 μg mL ( r = 0.9994) for sulfur mustard and 0.25-20 μg mL ( r = 0.9897-0.9987) for nitrogen mustards, respectively.

Rationale:Analytical methods for the detection and identification of half nitrogen mustards (halfNMs), i.e., partially hydrolyzed products of nitrogen mustards (pHpNMs), using silyl derivatives are often associated with low sensitivity and selectivity. In order to overcome these limitations, the derivatization of halfNMs was performed using perfluoroacylation.Methods: Two efficient derivatization techniques using trifluoroacetyl (TFA) and heptafluorobutyryl (HFB) groups were developed for the unambiguous identification of halfNMs. A mass spectral database was generated by performing gas chromatography/electron ionization mass spectrometry (GC/EI-MS) and gas chromatography/positive chemical ionization mass spectrometry (GC/PCI-MS). The fragmentation pathways were studied by tandem mass spectrometry (MS/MS) in both EI and PCI mode. Results:The EI-MS spectra of the TFA and HFB derivatives of halfNMs contain intense molecular ions and fragment ions, thus making perfluoroacylation preferable to silylation. In addition, the background-free chromatogram obtained using these derivatives provides unambiguous identification of these compounds in blind samples. The structures of the fragment ions were postulated, and the sources of significant ions were traced by performing MS/MS precursor ion scans. In the PCI-MS spectra, along with the protonated molecule, significant peaks due to neutral losses of HF, HCl, CH 3 Cl and CF 3 COOH were observed.Conclusions: This is the first report of the elucidation of the fragmentation pathways of perfluoroacyl derivatives of halfNMs. The complementary GC/PCI-MS and GC/PCI-MS/MS data will be helpful in the identification of unknown metabolites in a fast and reliable fashion.