Studies on residue-free decontaminants for chemical warfare agents

Non-contact detection of thiodiglycol vapors and associated degradation products using atmospheric flow tube mass spectrometry

Thiodiglycol (TDG) is a synthetic precursor and an environmental degradation product of sulfur mustard (HD). Consequently, its presence can be indicative of illicit preparation or historical presence of chemical weapons, but its lower toxicity lends itself to use as an HD simulant for testing and method development. Detection of TDG vapor often proves elusive with existing techniques exhibiting undesirably high detection limits in the gas phase (>ppm). Moreover, traditional approaches to detecting TDG vapor rely upon non-specific approaches that do not provide the certainty afforded by mass spectrometry. Using atmospheric flow tube mass spectrometry (AFT-MS), which has previously demonstrated the capacity to detect parts-per-quadrillion levels of vapor, we evaluate the capacity of this approach for non-contact residue analysis based upon TDG vapor sampling and nitrate clustering chemistry. Furthermore, we discuss challenges with ambient vapor detection using the AFT-MS system and associated observations related to TDG degradation into 2,2'-sulfonyldiglycol from exposure to ambient conditions with vapor detection being possible even after 7-weeks of sample aging.

Active and Strippable PVA/Borax/NaBO3 Hydrogel for Effective Containment and Decontamination of Chemical Warfare Agents

Active gels present unique potential for the decontamination of chemical warfare agents (CWAs) as they strongly adhere to surfaces, thus allowing prolonged decontamination time. Herein, we present a decontamination hydrogel based on polyvinyl alcohol/borax, which contains sodium perborate (NaBO₃), as an in situ source of the active ingredient hydrogen peroxide. Developed as a binary formulation, this gel instantly forms and effectively sticks when sprayed on various matrices, including porous and vertically positioned matrices. The gel efficiently detoxified the CWAs sarin (GB), O-ethyl S-2-(diisopropylamino)ethyl methylphosphonothioate (VX), and sulfur mustard (HD) in test tubes (2 μL CWA/0.5 mL gel) to provide nontoxic products with reaction half-lives of <3, 45 and 113 min, respectively. The gel was also shown to efficiently decontaminate surfaces contaminated with VX (5-7 mg, 8-12 mL of gel, i.e., >99%) and to prevent GB evaporation, as proven by laboratory wind tunnel experiments. The universal decontamination abilities of this mild hydrogel, as well as its facile application and removal processes suggest that it holds high potential for future development as a new CWA decontamination tool.

Rapid activation of basic hydrogen peroxide by borate and efficient destruction of toxic industrial chemicals (TICs) and chemical warfare agents (CWAs)

The activation process of the B(OH)₃-activated H₂O₂ solution and its performance toward toxic industrial chemicals (TICs) and chemical warfare agents (CWAs) were investigated to find an efficient way to destroy TICs and CWAs. ¹¹B NMR analysis proved that B(OH)₃ reacted rapidly with basic H₂O₂ to produce peroxoborates ([B(OH)_(4-x)(OOH)_x]^-), and the proportional contents were closely related to the pH and temperature. ¹O₂ and ·O₂^- were generated, and their production increased exponentially with pH. TICs thioanisole and paraoxon were used as simulants of CWAs to investigate the decontamination performance and nucleophilic/oxidizing reactivity of the B(OH)₃-activated H₂O₂. Batch experiments proved that peroxoborates acted as the oxidants for the primary oxidation of the sulfide at a pH range of 8-12 and that ·O₂^- was responsible for the further oxidation of sulfoxide. Paraoxon degraded through OOH^--mediated S_N2 displacement with high stereo-selectivity, and the degradation rate increased exponentially with pH. Mustard gas, soman, and VX degraded effectively into nontoxic products in the B(OH)₃-activated H₂O₂ solution. A pH of 9-11 was recommended as the suitable acidity for developing the B(OH)₃-activated H₂O₂ solution to be a candidate for nucleophilic/oxidizing decontaminant, with advantages in rapid activation and low loss rate of reactive oxygen species.

Self-Decontaminating Fibrous Materials Reactive toward Chemical Threats

Polymers that possess highly nucleophilic pyrrolidinopyridine (Pyr) and primary amino (vinylamine, VAm) groups were prepared by free-radical copolymerization of N,N-diallylpyridin-4-amine (DAAP) and N-vinylformamide (NVF) followed by acidic hydrolysis of NVF into VAm. The resulting poly(DAAP-co-VAm-co-NVF) copolymers were water-soluble and reacted with water-dispersible polyurethane possessing a high content of unreacted isocyanate groups. Spray-coating of the nylon-cotton (NYCO), rayon, and poly(p-phenylene terephthalamide) (Kevlar 119) fibers pretreated with phosphoric acid resulted in covalent bonding of the polyurethane with the hydroxyl groups on the fiber surface. A second spray-coating of aqueous solutions of poly(DAAP-co-VAm-co-NVF) on the polyurethane-coated fiber enabled formation of urea linkages between unreacted isocyanate groups of the polyurethane layer and the amino groups of poly(DAAP-co-VAm-co-NVF). Fibers with poly(DAAP-co-VAm-co-NVF) attached were compared with fibers modified by adsorption of water-insoluble poly(butadiene-co-pyrrolidinopyridine) (polyBPP) in terms of the stability against polymer leaching in aqueous washing applications. While the fibers modified by attachment of poly(DAAP-co-VAm-co-NVF) exhibited negligible polymer leaching, over 65% of adsorbed polyBPP detached and leached from the fibers within 7 days. Rayon fibers modified by poly(DAAP-co-VAm-co-NVF) were tested for sorption of dimethyl methylphosphonate (DMMP) in the presence of moisture using dynamic vapor sorption technique. Capability of the fibers modified with poly(DAAP-co-VAm-co-NVF) to facilitate hydrolysis of the sorbed DMMP in the presence of moisture was uncovered. The self-decontaminating property of the modified fibers against chemical threats was tested using a CWA simulant diisopropylfluorophosphate (DFP) in aqueous media at pH 8.7. Fibers modified with poly(DAAP-co-VAm-co-NVF) facilitated hydrolysis of DFP with the half-lives up to an order of magnitude shorter than that of the unmodified fibers. The presented polymers and method of multilayer coating can lead to a development of self-decontaminating textiles and other materials.

The combined action of methanolysis and heterogeneous photocatalysis in the decomposition of chemical warfare agents

The combination of methanolysis and photocatalysis can be used for the decomposition of CWA. Herein, we present such a catalytic system, which is able to perform efficient nerve agent decomposition in just 1 minute.