Diisopropyl Methylphosphonate Research Articles

Oxidative Destruction of Multilayer Diisopropyl Methylphosphonate Films by O(3P) Atomic Oxygen.

We present work detailing the oxidative destruction of the nerve agent simulant diisopropyl methylphosphonate (DIMP) with O(3P) using time-resolved, in situ reflection absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). Thermally annealed DIMP films deposited on Au(111) are observed to react upon exposure to a supersonic beam containing O(3P) with average translational energies of 0.12 eV. The reaction is initiated by a hydrogen abstraction from one of three possible sites on DIMP, and then progresses through various secondary reactions with resultant hydroxyl radicals, carbon-centered DIMP-derived radicals, and nondissociated O2 in the beam. These reactions are accompanied by uptake of oxygen into the film, leading to new hydrogen bonding with the DIMP phosphoryl group. The generated product also presents greater thermal stability than pristine DIMP, suggesting the formation of a distribution of oligomeric and polymeric products. As reactivity is observed to decrease upon continued O(3P) exposure, this product likely forms a protective layer at the vacuum-film interface, hindering destruction of thicker films. Importantly, the rate of reaction and general reactivity trends are the same between DIMP and the smaller simulant dimethyl methylphosphonate (DMMP). The comparable reaction rates of the two molecules coupled with oxygen's inability to erode thick films all the way down to the substrate have specific implications for the development of oxidation-based decontamination strategies for these and other organophosphates in the solid phase. The findings presented in this paper add significant new fundamental understanding of the oxidative chemistry of such species, knowledge needed in order to develop efficacious nerve agent decontamination strategies as well as the refinement of existing models for the dispersal, adsorption, persistence, and destruction of organophosphates in the environment.

Investigation of the Persistence of Nerve Agent Degradation Analytes on Surfaces through Wipe Sampling and Detection with Ultrahigh Performance Liquid Chromatography-Tandem Mass Spectrometry

The persistence of chemical warfare nerve agent degradation analytes on surfaces is important, from indicating the presence of nerve agent on a surface to guiding environmental restoration of a site after a release. Persistence was investigated for several chemical warfare nerve agent degradation analytes on indoor surfaces and presents an approach for wipe sampling of surfaces, followed by wipe extraction and liquid chromatography-tandem mass spectrometry detection. Commercially available wipe materials were investigated to determine optimal wipe recoveries. Tested surfaces included porous/permeable (vinyl tile, painted drywall, and wood) and largely nonporous/impermeable (laminate, galvanized steel, and glass) surfaces. Wipe extracts were analyzed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). UPLC provides a separation of targeted degradation analytes in addition to being nearly four times faster than high-performance liquid chromatography, allowing for greater throughput after a large-scale contamination incident and subsequent remediation events. Percent recoveries from nonporous/impermeable surfaces were 60-103% for isopropyl methylphosphonate (IMPA), GB degradate; 61-91% for ethyl methylphosphonate (EMPA), VX degradate; and 60-98% for pinacolyl methylphosphonate (PMPA), GD degradate. Recovery efficiencies for methyl phosphonate (MPA), nerve agent degradate, and ethylhydrogen dimethylphosphonate (EHDMAP), GA degradate, were lower, perhaps due to matrix effects. Diisopropyl methylphosphonate, GB impurity, was not recovered from surfaces. The resulting detection limits for wipe extracts were 0.065 ng/cm(2) for IMPA, 0.079 ng/cm(2) for MPA, 0.040 ng/cm(2) for EMPA, 0.078 ng/cm(2) for EHDMAP, and 0.013 ng/cm(2) for PMPA. The data indicate that laboratories may hold wipe samples for up to 30 days prior to analysis. Target analytes were observed to persist on surfaces for at least 6 weeks.

Demonstration of spread-on peel-off consumer products for sampling surfaces contaminated with pesticides and chemical warfare agent signatures

A terrorist attack using toxic chemicals is an international concern. The utility of rubber cement and latex body paint as spray-on/spread-on peel-off collection media for signatures attributable to pesticides and chemical warfare agents from interior building and public transportation surfaces two weeks post-deposition is demonstrated. The efficacy of these media to sample escalator handrail, stainless steel, vinyl upholstery fabric, and wood flooring is demonstrated for two pesticides and eight chemicals related to chemical warfare agents. The chemicals tested are nicotine, parathion, atropine, diisopropyl methylphosphonate, dimethyl methylphosphonate, dipinacolyl methylphosphonate, ethyl methylphosphonic acid, isopropyl methylphosphonic acid, methylphosphonic acid, and thiodiglycol. Amounts of each chemical found are generally greatest when latex body paint is used. Analytes with low volatility and containing an alkaline nitrogen or a sulfur atom (e.g., nicotine and parathion) usually are recovered to a greater extent than the neutral phosphonate diesters and acidic phosphonic acids (e.g., dimethyl methylphosphonate and ethyl methylphosphonic acid).

Spectroscopic Investigation of the Noncovalent Association of the Nerve Agent Simulant Diisopropyl Methylphosphonate (DIMP) with Zinc(II) Porphyrins

Organophosphonates pose a significant threat as chemical warfare agents, as well as environmental toxins in the form of pesticides. Thus, methodologies to sense and decontaminate these agents are of significant interest. Porphyrins and metalloporphyrins offer an excellent platform to develop chemical threat sensors and photochemical degradation systems. These highly conjugated planar molecules exhibit relatively long-lived singlet and triplet states with high quantum yields and also form self-associated complexes with a wide variety of molecules. A significant aspect of porphyrins is the ability to functionalize the peripheral ring system either directly to the pyrrole rings or to the bridging methine carbons. In this report, steady-state absorption and fluorescence are utilized to probe binding affinities of a series of symmetric and asymmetric zinc(II) metalloporphyrins for the nerve agent simulant diisopropyl methylphosphonate (DIMP) in hexane. The red shifts in the absorption and emission spectra observed for all of the metalloporphyrins probed are discussed in the frame of Gouterman's four orbital model and a common binding motif involving coordination between the metalloporphyrin and DIMP via interaction between the zinc metal center of the porphyrin and phosphoryl oxygen of DIMP (Zn-O═P) is proposed.

Application of a High Surface Area Solid-Phase Microextraction Air Sampling Device: Collection and Analysis of Chemical Warfare Agent Surrogate and Degradation Compounds

This work examines a recently improved, dynamic air sampling technique, high surface area solid-phase microextraction (HSA-SPME), developed for time-critical, high-volume sampling and analysis scenarios. The previously reported HSA-SPME sampling device, which provides 10-fold greater surface area compared to commercially available SPME fibers, allowed for an increased analyte uptake per unit time relative to exhaustive sampling through a standard sorbent tube. This sampling device has been improved with the addition of a type-K thermocouple and a custom heater control circuit for direct heating, providing precise (relative standard deviation ∼1%) temperature control of the desorption process for trapped analytes. Power requirements for the HSA-SPME desorption process were 30-fold lower than those for conventional sorbent-bed-based desorption devices, an important quality for a device that could be used for field analysis. Comparisons of the HSA-SPME device when using fixed sampling times for the chemical warfare agent (CWA) surrogate compound, diisopropyl methylphosphonate (DIMP), demonstrated that the HSA-SPME device yielded a greater chromatographic response (up to 50%) relative to a sorbent-bed method. Another HSA-SPME air sampling approach, in which two devices are joined in tandem, was also evaluated for very rapid, low-level, and representative analysis when using discrete sampling times for the compounds of interest. The results indicated that subparts per billion by volume concentration levels of DIMP were detectable with short sampling times (∼15 s). Finally, the tandem HSA-SPME device was employed for the headspace sampling of a CWA degradation compound, 2-(diisopropylaminoethyl) ethyl sulfide, present on cloth material, which demonstrated the capability to detect trace amounts of a CWA degradation product that is estimated to be less volatile than sarin. The rapid and highly sensitive detection features of this device may be beneficial in decision making for law enforcement, military, and civilian emergency organizations and responders, providing critical information in a contaminated environment scenario when time is of the essence.

Infrared Spectra and Binding Energies of Chemical Warfare Nerve Agent Simulants on the Surface of Amorphous Silica

The fundamental interactions of a series of chemical warfare agent (CWA) simulants on amorphous silica particulates have been investigated with transmission infrared spectroscopy and temperature-programmed desorption (TPD). The simulants methyl dichlorophosphate (MDCP), dimethyl cholorophosphate (DMCP), trimethyl phosphate (TMP), dimethyl methylphosphonate (DMMP), and diisopropyl methylphosphonate (DIMP) were chosen to help develop a comprehensive understanding for how the structure and functionality of CWA surrogate compounds affect uptake and hydrogen-bond strengths at the gas–surface interface. Each simulant was found to adsorb molecularly to silica through the formation of strong hydrogen bonds primarily between isolated surface silanol groups and the oxygen atom of the P═O moiety in the adsorbate. The TPD data revealed that the activation energy for desorption of a single simulant molecule from amorphous silica varied slightly with coverage. In the limit of zero coverage and the absence of significant surface defects, the activation energies for desorption were found to follow the trend MDCP < DMCP < TMP < DMMP < DIMP. This trend demonstrates the critical role of electron-withdrawing substituents in determining the adsorption energies through hydrogen-bonding interactions. The infrared spectra for each adsorbed species, recorded during uptake, showed a significant shift in the frequency of the ν(SiO–H) mode as the hydrogen bonds formed. A clear linear relationship between the desorption energy and the shift of the surface ν(SiO–H) mode across this series of adsorbates demonstrates that the Badger–Bauer relationship, established origninally for solute–solvent interactions, effectively extends to gas–surface interactions. High-level electronic structure calculations, including extrapolation to the complete basis set limit, reproduce the experimental energies of all simulants with high levels of accuracy and have been employed to provide insight into the molecular-level details of adsorption geometries for the simulants and to predict the interaction energies for the CWA isopropyl methylphosphonofluoridate (sarin).

Theoretical Study of the Adsorption of Organophosphorous Compounds to Models of a Silica Surface

We present a study of the interaction of seven organophosphorous (OP) compounds with models of a silica surface using electronic structure calculations. Two of the OP species are chemical-warfare nerve agents (sarin and soman) and the rest are organophosphate (methyl dichlorophosphate, dimethyl chlorophosphate, and trimethyl phosphate) or organophosphonate (dimethyl methylphosphonate and diisopropyl methylphosphonate) mimics utilized in recent experiments. Calculations that approximate an amorphous silica surface by a simple gas-phase silanol molecule qualitatively reproduce the trend in binding energies determined in recent ultrahigh vacuum experiments. These calculations also show that, of the various atoms in the OP species that can accept hydrogen bonds from silanol groups, the oxygen atom that forms a double bond with the central phosphorus atom provides the largest binding energy, followed first by the remaining oxygen atoms and then by the halogen atoms. Quantitative comparisons with experiments ar...

Surface Binding of Organophosphates on Silica: Comparing Experiment and Theory

A consistent embedding hierarchy is applied to the calculation of binding enthalpies for organophosphate molecules to a silica surface and compared to experiment. The interaction of four probe molecules, dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), diisopropyl fluorophosphate (DFP), and sarin, with the silica surface is examined. Quantum chemical methods are employed to compute binding enthalpies and vibrational spectra for all interactions between probe molecules and silanol sites on the silica surface. Comparison with experimentally measured infrared shifts indicates that the theoretically modeled adsorption sites are similar to those found in experiment. The calculated binding enthalpies agree well with experiment for sarin, ΔHads,443K = −22.0 kcal/mol (calculated) vs −18.8 ± 5.5 kcal/mol (measured, 433 K < Texpt < 453 K), and DIMP, ΔHads,463K = −26.9 kcal/mol (calculated) vs −29.3 ± 0.9 kcal/mol (measured, 453 K < Texpt < 473 K). Agreement with experiment is less good for D...

Dust as a collection media for contaminant source attribution

Dust was investigated for its ability to retain source attribution profiles (SAPs) after chemical exposure. Three distinct sources of the organophosphate pesticide acephate were investigated as a proof-of-concept model. In addition, attribution profiles were created and tested using compounds related to chemical warfare agents (CWAs), specifically VX and G-series agents: O-ethyl methylphosphonothioate (EMPTA), N,N-diisopropylmethylamine (DIPMA), N,N-diisopropylethylamine (DIEA), diisopropylamine (DIPA), diethyl aniline (DEA), diethyl ethyl phosphonate (DEEP), trimethyl phosphite (TMP), dimethyl hydrogen phosphite (DMHP), diethyl hydrogen phosphite (DEHP), triethyl phosphate (TEP), ethyl methylphosphonate (EMPA), and diisopropyl methylphosphonate (DIMP). Dust was collected from a storage shed, aliquots deposited on carpet and loaded with distinct chemical profiles using an exposure chamber and aerosolizer. After a given period of time (1h, 24h, or 72 h), the dust was extracted and its SAP analyzed by gas chromatography-mass spectrometry (GC-MS) and/or liquid chromatography-tandem mass spectrometry (LC-MS/MS). Principal components analysis (PCA) was used to determine the association of dust exposed to the same and different chemical sources. PCA results demonstrate that dust samples exposed to distinct chemical sources are clearly differentiated from one another across all collection times. Furthermore, dust aliquots exposed to the same source can be clearly associated with one another across all collection times. When the CWA-related compounds were subjected to elevated temperature (90°C) conditions, it was found that the signature was stable at the 1h and 24h collections. At 72 h and elevated temperature, larger deviations from the control were observed for some compounds. Elevated pH (10) affected the profile to a lesser degree than elevated temperature. Overall, dust is found to be an effective media for the in situ collection of source attribution profiles.

Structural Elucidation of Direct Analysis in Real Time Ionized Nerve Agent Simulants with Infrared Multiple Photon Dissociation Spectroscopy

Infrared multiple photon dissociation (IRMPD) was used to generate vibrational spectra of ions produced with a direct analysis in real time (DART) ionization source coupled to a 4.7 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The location of protonation on the nerve agent simulants diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP) was studied while solutions of the compounds were introduced for extended periods of time with a syringe pump. Theoretical vibrational spectra were generated with density functional theory calculations. Visual comparison of experimental mid-IR IRMPD spectra and theoretical spectra could not establish definitively if a single structure or a mixture of conformations was present for the protonated parent of each compound. However, theoretical calculations, near-ir IRMPD spectra, and frequency-to-frequency and statistical comparisons indicated that the protonation site for both DIMP and DMMP was predominantly, if not exclusively, the phosphonyl oxygen instead of one of the oxygen atoms with only single bonds.

A hybrid chemiresistive sensor system for the detection of organic vapors

A five node sensor array, consisting of three films of gold nanoparticles functionalized with p-terphenylthiol, dodecanethiol and mercapto-(triethylene glycol) methyl ether, and films of poly(3-hexylthiophene) and polypyrrole, was integrated into a portable, microprocessor-based system. The system was evaluated for the detection of chloroform, diisopropyl methylphosphonate (DIMP), ethanol, hexane, methanol, and toluene vapors. Direct comparison of the five sensor films with respect to sensitivity, response time and recovery time was made by measurement of the resistance changes upon simultaneous exposure to each analyte. In general, the sensor films responded, with greatest sensitivity, to organic analyte molecules with similar chemical functionality (e.g., polarity). For example, the dodecanethiol-functionalized gold nanoparticle film sensor excelled at detecting hexane, while the mercapto-(triethylene glycol) methyl ether-functionalized nanoparticle film exhibited superb detection of ethanol and chloroform. Although the poly(3-hexylthiophene) film was very sensitive to polar analytes, including DIMP, in many cases it suffered from relatively long recovery times. Following training of the sensor system, successful differentiation and detection of the analytes were realized using a relatively simple algorithm based on “minimization of the squares of differences” method. The ability of the system to optimally differentiate these analytes is considered within the context of principal component analysis, and the effects of long-term sensor drift are discussed.

Synthesis of O2- and N3-(2-Phosphonomethoxy)ethyl Derivatives of 6-Phenyl- and 6-Pyridinyl-5-azacytosine

A series of hydrolytically stable Oand N-(2-phosphonomethoxy)ethyl (PME) derivatives of 6-phenyl, pyridin-2, -3 and -4-yl-5-azacytosines was prepared by their alkylation with diisopropyl (2-chloroethoxy)methylphosphonate followed by the deprotection. No antitumor or antiviral activity was found except for 6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine (13d) which exhibited slight activity against feline herpesvirus in CrFK cell cultures with IC50 = 6.7 μg/mL. INTRODUCTION 5-Azacytosine nucleosides are well-known anticancer agents with an epigenetic mechanism of action. Two of them, 2’-deoxy-5-azacytidine (decitabine, Dacogen, 1; its alpha anomer 2 shows comparable epigenetic activity but with much lower toxicity) and 5-azacytidine(Vidaza, 3), were approved for treatment of myelodisplastic syndromes (MDS, Figure 1). Others, i.e. 5-azacytosine arabinoside (fazarabine, 4) and 5,6-dihydro-5-azacytidine (5), are being investigated in clinical trials. On the other hand, 2’-deoxy-5,6-dihydro-5-azacytidine (6) exhibits a very strong anti-HIV potency, which enables, especially when its prodrug KP-1461 (7) is applied, the eradication of HIV from laboratory cell cultures. Compound 6 does not inhibit reverse transcription like other nucleosides or acyclic nucleoside phosphonates, but, after incorporation into proviral DNA, it acts as an ambiguous base, which causes mutations. An accumulation of the errors throughout the viral genome during the replication cycle may lead to a progressive decrease of the fitness of the virus and further to a lethal mutagenesis, which may cause a total collapse of the virus population. Recently, a pronounced antiviral activity has been HETEROCYCLES, Vol. 83, No. 4, 2011 797

Modification of poly(vinyl butyral) coatings using bis-silanes

A commercially available poly(vinyl butyral) (PVB) coating was modified using a combination of 1–10wt.% bis(trimethoxysilylethyl)benzene and dibutyltin dilaurate as the hydrolysis catalyst. Results of attenuated total reflectance (ATR)–FTIR analysis indicated the modification resulted in a hybrid coating material containing silicate moieties covalently bonded to the PVB polymer chains. Gravimetric analysis indicted the bis-silane addition resulted in a reduction in the diffusion coefficient of the parent coating to 2-chloroethyl ethyl sulfide (2-CEES), dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate, and methyl salicylate; the most significant reduction was observed for 2-CEES and DMMP at temperatures ≥50°C. Glass transition temperature, abrasion resistance, tensile strength, and coating hardness were increased upon incorporation of the bis-silane. Despite incorporation of an inorganic component, coating flexibility was retained at low temperature (−15°C).

ChemInform Abstract: Esterification of Amine-Carboxyboranes with Orthoformates: A High Yield Synthesis.

Amine-alkoxycarbonylboranes, amine BH 2 CO 2 R (amine=trimethylamine, methylamine, N-methylmorpholine, pyridine, and diisopropyl (methylamino)methylphosphonate; R=methyl, ethyl, propyl, allyl, and 2-methylpropyl) were prepared in high yield by reacting the amine-carboxyborane with a trialkyl orthoformate in the presence of diethyl ether-boron trifluorate complex as a catalyst

ANALYSIS AND IDENTIFICATION SPIKING CHEMICAL COMPOUNDS RELATED TO CHEMICAL WEAPON CONVENTION IN UNKNOWN WATER SAMPLES USING GAS CHROMATOGRAPHY AND GAS CHROMATOGRAPHY ELECTRON IONIZATION MASS SPECTROMETRY

The identification and analysis of chemical warfare agents and their degradation products is one of important component for the implementation of the convention. Nowadays, the analytical method for determination chemical warfare agent and their degradation products has been developing and improving. In order to get the sufficient analytical data as recommended by OPCW especially in Proficiency Testing, the spiking chemical compounds related to Chemical Weapon Convention in unknown water sample were determined using two different techniques such as gas chromatography and gas chromatography electron-impact ionization mass spectrometry. Neutral organic extraction, pH 11 organic extraction, cation exchanged-methylation, triethylamine/methanol-silylation were performed to extract the chemical warfare agents from the sample, before analyzing with gas chromatography. The identification of chemical warfare agents was carried out by comparing the mass spectrum of chemicals with mass spectrum reference from the OPCW Central Analytical Database (OCAD) library while the retention indices calculation obtained from gas chromatography analysis was used to get the confirmation and supported data of the chemical warfare agents. Diisopropyl methylphosphonate, 2,2-diphenyl-2-hydroacetic acid and 3-quinuclidinol were found in unknown water sample. Those chemicals were classified in schedule 2 as precursor or reactant of chemical weapons compound in schedule list of Chemical Weapon Convention. Keywords: gas chromatography, mass spectrometry, retention indices, OCAD library, chemical warfare agents

The coupling of direct analysis in real time ionization to Fourier transform ion cyclotron resonance mass spectrometry for ultrahigh-resolution mass analysis

Direct Analysis in Real Time (DART) is an ambient ionization technique for mass spectrometry that provides rapid and sensitive analyses with little or no sample preparation. DART has been reported primarily for mass analyzers of low to moderate resolving power such as quadrupole ion traps and time-of-flight (TOF) mass spectrometers. In the current work, a custom-built DART source has been successfully coupled to two different Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers for the first time. Comparison of spectra of the isobaric compounds, diisopropyl methylphosphonate and theophylline, acquired by 4.7 T FT-ICR MS and TOF MS, demonstrates that the TOF resolving power can be insufficient for compositionally complex samples. 9.4 T FT-ICR MS yielded the highest mass resolving power yet reported with DART ionization for 1,2-benzanthracene and 9,10-diphenylanthracene. Polycyclic aromatic hydrocarbons exhibit a spatial dependence in ionization mechanisms between the DART source and the mass spectrometer. The feasibility of analyzing a variety of samples was established with the introduction and analysis of food products and crude oil samples. DART FT-ICR MS provides complex sample analysis that is rapid, highly selective and information-rich, but limited to relatively low-mass analytes.

Preferential photodegradation of contaminants by molecular imprinting on titanium dioxide

The photocatalytic degradation of organic contaminants on titanium dioxide is basically non-selective. While this seems at first glance to be an advantage, this is not the case when a stream containing low concentrations of highly toxic substances together with high concentrations of low toxic organics has to be treated. A method for obtaining preferential degradation by means of preparation of molecularly imprinted photocatalyst is presented hereby. The method is demonstrated with two model compounds simulating the nerve gas sarin: diisopropyl methylphosphonate (DIMP) and diethylhydroxy methylphosphonate (DEHMP).An improvement by a factor of 3–4 in the mineralization rates was observed upon using the imprinted substrates. This enhancement in photocatalytic rates cannot be explained by the modest growth in the surface area (not more than 20–30%), hence it can be concluded that the enhancement resulted from the conformity between the target molecules and the molecular cavities on the imprinted sites. This conclusion is further supported by the lower extent of enhancement upon degrading benzene and heptane.Of particular interest is the fact that substrates that were imprinted with DEHMP were found to be very effective in the degradation of the homolog DIMP. This observation suggests the use of molecules having good affinity to the matrix as a means to obtain high surface concentration of molecular active sites, thus detouring the problem of aggregation that might arise in cases where the target contaminants have low affinity to the matrix. Another benefit is the possibility of using non-toxic homolog molecules for constructing the imprinted photocatalyst. This benefit is in particular important when designing a photocatalyst for WMD warfare agents, as in the case of sarin.

Real‐time trace detection and identification of chemical warfare agent simulants using recent advances in proton transfer reaction time‐of‐flight mass spectrometry

This work demonstrates for the first time the potential of using recent developments in proton transfer reaction mass spectrometry for the rapid detection and identification of chemical warfare agents (CWAs) in real-time. A high-resolution (m/Deltam up to 8000) and high-sensitivity (approximately 50 cps/ppbv) proton transfer reaction time-of-flight mass spectrometer (PTR-TOF 8000 from Ionicon Analytik GmBH) has been successfully used to detect a number of CWA simulants at room temperature; namely dimethyl methylphosphonate, diethyl methylphosphonate, diisopropyl methylphosphonate, dipropylene glycol monomethyl ether and 2-chloroethyl ethyl sulfide. Importantly, we demonstrate in this paper the potential to identify CWAs with a high level of confidence in complex chemical environments, where multiple threat agents and interferents could also be present in trace amounts, thereby reducing the risk of false positives. Instantaneous detection and identification of trace quantities of chemical threats using proton transfer reaction mass spectrometry could form the basis for a timely warning system capability with greater precision and accuracy than is currently provided by existing analytical technologies.

Extraction of chemical impurities for forensic investigations: A case study for indoor releases of a sarin surrogate

A solvent extraction approach was developed and examined for extraction of targeted organophosphorus compounds as well as nerve agent simulants from painted wallboard (PWB). Painted wallboard was chosen as a substrate due to its presence as large surface area media in an indoor environment that is applicable to a chemical agent release scenario. Three different solvent systems were examined with a 1:1 methylene chloride: acetone mixture having the most robust and consistent extraction for four target organophosphorus compounds [dimethyl methyl phosphonate (DMMP), diethyl methyl phosphonate (DEMP), diethyl methyl phosphonothioate (DEMPT), and diisopropyl methyl phosphonate (DIMP)]. An average extraction efficiency of approximately 60% was obtained for these four compounds. The extraction approach was further demonstrated by extracting and detecting the chemical impurities present in neat DMMP that was vapor deposited onto painted wallboard tickets as a simulant to an agent release. Five chemical impurities that were present in DMMP – dimethyl phosphate, trimethyl ester phosphoric acid, ethyl methyl methylphosphonate, O,O,S-trimethyl ester phosphorothioic acid, and biphenyl were detected on the PWB and were utilized to determine the source/supplier of the DMMP.

Vapor Pressure of Organophosphorus Nerve Agent Simulant Compounds

The vapor pressures of four lower alkyl phosphonate compounds, dimethyl phosphonate (DMHP, CAS 868-85-9), dimethyl methylphosphonate (DMMP, CAS 756-79-6), diethyl methylphosphonate (DEMP, CAS 683-08-9), and diisopropyl methylphosphonate (DIMP, CAS 1445-75-6), have been measured by complementary methods that allow data collection at ambient and high temperatures by use of gas saturation and differential scanning calorimetry, respectively. Kosolapoff (J. Chem. Soc. 1955, 2964−2965) reported vapor pressure data above 200 Pa for several of these compounds measured by use of isoteniscope, although the lowest data points were deemed to be “not trustworthy” by the author. Our report extends the low end of the measured data range by 2 to 3 orders of magnitude in pressure. Antoine correlations, normal boiling temperatures, temperature-dependent enthalpies of vaporization, and volatility have been derived based on the measured data reported herein. The advantages of using complementary methodology and measuring, as opposed to extrapolating, data have been demonstrated in this work.