Dimethyl Methylphosphonate Research Articles

Insights and Heuristics for Predicting Diffusion Rates of Chemical Warfare Agents in Zirconium Metal-Organic Frameworks.

Designing nanoporous catalysts to destroy chemical warfare agents (CWAs) and environmental contaminants requires consideration of both intrinsic catalytic activity and the mass transfer of molecules in and out of the pores. Polar adsorbates such as CWAs experience a heterogeneous environment in many metal-organic frameworks (MOFs) due to the arrangement of the metal nodes and organic linkers of the MOF. However, quantitative relationships between the pore architecture and the resulting diffusion properties of polar molecules have not been established. We used molecular dynamics simulations to calculate the diffusion coefficients of the CWA simulant dimethyl methyl phosphonate (DMMP) in a diverse set of 776 MOFs with Zr6 nodes. We developed a 4-parameter machine learning model to predict DMMP diffusivities in Zr6 MOFs and found the model to be transferable to the CWA sarin. We then developed a simplified heuristic based on the machine learning model that the node-node distance and accessible surface area should be maximized to find MOFs with rapid CWA diffusion.

Sunflower Oil as a Renewable Resource for Polyurethane Foams: Effects of Flame-Retardants

Currently, polyurethane (PU) manufacturers seek green alternatives for sustainable production. In this work, sunflower oil is studied as a replacement and converted to a reactive form through epoxidation and oxirane opening to produce rigid PU foams. Confirmatory tests such as Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and hydroxyl value among others were performed to characterize the synthesized polyol. Despite the versatility of rigid PU foams, they are highly flammable, which makes eco-friendly flame retardants (FRs) desired. Herein, expandable graphite (EG) and dimethyl methyl phosphonate (DMMP), both non-halogenated FR, were incorporated under different concentrations to prepare rigid PU foams. Their effects on the physio-mechanical and fire-quenching properties of the sunflower oil-based PU foams were elucidated. Thermogravimetric and compression analysis showed that these foams presented appreciable compressive strength along with good thermal stability. The closed-cell contents (CCC) were around 90% for the EG-containing foams and suffered a decrease at higher concentrations of DMMP to 72%. The burning test showed a decrease in the foam's flammability as the neat foam had a burning time of 80 s whereas after the addition of 13.6 wt.% of EG and DMMP, separately, there was a decrease to 6 and 2 s, respectively. Hence, our research suggested that EG and DMMP could be a more viable alternative to halogen-based FR for PU foams. Additionally, the adoption of sunflower polyol yielded foams with results comparable to commercial ones.

Dual-technique assay for the analysis of organophosphorus compounds for environmental and chemical defense applications

Forensic and environmental sciences often rely on chromatographic separations coupled to mass spectrometry to detect contaminants in complex matrices. However, these methods require lengthy analysis times and sample preparation that is not suitable for analysis in the field. In this work, two analytical methods were combined that are known for their potential for portable analysis. The ambient ionization technique, paper spray mass spectrometry (paper spray-MS) was coupled to paper-based surface enhanced Raman spectroscopy (pSERS) to detect toxic organophosphorus molecules from the same substrate, with a total analysis time of less than five minutes. The coupling of these techniques presents a potential for portable Raman screening followed by MS confirmation in a field-forward laboratory. A cartridge insert was designed and 3D printed to facilitate the sample collection and analysis for PS-MS and pSERS. Three chemical warfare agent simulants: dimethyl methylphosphonate (DMMP), diethyl phosphoramidate (DEPA), and diisopropyl methylphosphonate (DIMP) were included in the method due to having similar chemistries to G- and V-series chemical warfare agents (CWAs). Organophosphorus pesticides, malathion and dichlorvos, with similar mechanisms of action to the CWAs, were also included in the method. Because CWAs quickly degrade in the environment, the CWA hydrolysis products, ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA), pinacolyl methylphosphonic acid (PinMPA), methylphosphonic acid (MPA), 2-Diethylaminoethanethiol (EDA), and 2-Diisopropylaminoethanethiol (IDA) were also studied. A mixture of the analytes was used to create calibration curves using the dual-polarity, PS-MS method with sub-ng to low ng limits of detection. A dilution series, spanning 3 orders of magnitude, was made using pSERS, also with low ng limits of detection. These experiments show the potential and feasibility for PS-MS coupled to pSERS to be used to rapidly, screen and confirm the presence of organophosphorus molecules, in complex matrices, with portable instrumentation.

Rational Design of a Zr-MOF@Curli-Polyelectrolyte Hybrid Membrane toward Efficient Chemical Protection, Moisture Permeation, and Catalytic Detoxification.

Developing high-performance protective materials is important for soldiers and civilians who are exposed to the atmosphere of highly toxic chemical warfare agents (CWAs). Polyelectrolyte membranes are promising candidates with excellent chemical resistance and moisture permeability, but they cannot efficiently degrade CWAs. Here, we design and prepare a hybrid membrane through in situ growth of catalytically active zirconium-based metal-organic frameworks (Zr-MOFs) on a polyelectrolyte membrane mediated by biofilm-inspired curli nanofibers (CNFs). Superior to the bare polyelectrolyte membrane, the prepared MOF-808@CNF-PQ hybrid membrane exhibits improved rejection of the nerve agent simulant dimethyl methyl phosphonate (DMMP) vapor and permeation of the water vapor by 113 and 45%, respectively. The water/DMMP selectivity of the hybrid membrane reaches 498.6, approximately 13 times that of the commercial polyelectrolyte membrane Nafion 117. In addition, the hybrid membrane possesses appreciable catalytic activity for the hydrolysis of the nerve agent simulant dimethyl 4-nitrophenyl phosphate (DMNP) with a half-life of ∼38 min. Nanomechanical characterization results based on atomic force microscopy (AFM) techniques demonstrate the critical role of CNFs in mediating Zr-MOF nucleation and the dominant effect of electrostatic interactions on self-assembly of CNFs on polyelectrolyte base. It is also confirmed that the Zr-MOF toppings serve as the key components in physically adsorbing and chemically degrading the DMNP molecules through multiple strong intermolecular interactions. Our work offers a rational strategy to develop advanced membranes toward efficient chemical protection, moisture permeation, and catalytic detoxification against CWAs.

Gas sensing of organophosphorous compounds with III–V semiconductor plasmonics

Chemical warfare agents including nerve agents, e.g., sarin, are part of the organophosphorous compounds group known for their extreme lethal potency towards humans. With increasing risks of exposure to these molecules, there is a need for sensitive and selective detection. Infrared absorption spectroscopy is a powerful technique for the identification of molecules by probing their vibro-rotational molecular resonances. However, infrared light wavelength and molecule absorption cross-section dimensions mismatch, significantly hampering light-matter interaction especially at low concentrations, therefore lowering the sensitivity. To overcome this challenge, we propose a rapid chemistry-free III–V semiconductors InAsSb plasmonic sensor working in the mid-infrared with ribbon-shape nano-antennas associated to a confined enhanced electric field at the nanoscale. Exploiting well-known Salisbury perfect absorber structure coupled to an epsilon-near-zero layer benefit both spectral and spatial overlap, two required conditions for surface-enhanced infrared spectroscopy. Finite difference time domain and rigorous coupled-wave analysis coupled to Drude formalism were performed to design the sensor. The plasmonic sensor was exposed to hundreds of ppm-level concentration vapors of dimethyl methylphosphonate, known as DMMP, a commonly used sarin simulant. We determined that DMMP bound to the sensor native oxide to form a 5 Å estimated monolayer. The sensor response results from the coupling between surface plasmons and DMMP molecular vibrations upon adsorption at resonances frequency. Further simulations confirmed experimental results. This work demonstrates the application of III–V semiconductor plasmonics for gas sensing of complex molecules exploiting surface-enhanced infrared absorption.

Highly vertical 3D bio-inspired hierarchical and multiscale superstructures on microcantilever for gas sensing of organophosphorous agents

Microgravimetric sensors offer promising solution to detect volatile compounds. However, they suffer from a low surface-to-volume ratio limiting the maximum amount of adsorbate that can be fixed on their 2D surface. In this study, we report a bio-inspired method to elaborate highly vertical 3D hierarchical and multiscale superstructures in order to greatly increase the surface area of the microcantilever and to capture more molecules in vapor phase. However, building such superstructures on the microcantilever surface remains challenging in terms of structural design and synthesis while preserving a sufficient response of the sensor at low gas concentration. These particular superstructures are inspired from the antenna of the silkmoth Bombyx mori which is composed of a stem with branches on either side, themselves covered with sensilla. A patterned-microcantilever with high-aspect-ratio silicon micropillars is therefore used as support to generate a dense array of titanium dioxide nanorods decorated by goethite nanobranches. 3D hierarchical superstructures show a high enhancement in the response of the sensor to vapor of dimethyl methylphosphonate, a common simulant of sarin considered as one of the most toxic molecules. This design generates mass and surface stress effects under exposure to low vapor concentrations allowing to reach a limit of detection of 3 ppb. The sensor shows also a fast response to a wide range of concentrations. These results provide promising prospects to improve the detection potential of microcantilever-based sensors by using complex superstructures and dedicated materials to generate stress effect on the microcantilever surface and overcome the conventional microcantilever sensors based only on mass variation.

Detection of hazardous chemical using dual-wavelength Raman spectroscopy in the ultraviolet region

This study proposes a stand-off Raman spectroscopy system using dual-wavelength in the ultraviolet (UV) region to detect hazardous chemicals. The Raman spectrum generated by the UV excitation source avoids solar background noise during daytime for chemical detection as the spectrum is in the solar blind range. Wavelengths of 213 and 266 nm by 5th and 4th harmonics are generated from Nd:YAG laser. However, Raman spectra of chemicals exhibit different signal-to-noise ratios for both the excitation wavelengths; therefore, to detect such chemicals, Raman spectra by two sources are required. Raman spectra were acquired using a dual-wavelength laser and spectrometer with a single grating and detector at the wavelengths of 213 and 266 nm simultaneously. The Raman spectra of sulfuric acid, 2-chloroethyl ethyl sulfide, and dimethyl methylphosphonate were acquired and analyzed, thus highlighting the application of dual-wavelength Raman spectroscopy. For efficient chemical detection in the field, we have ensured that the system developed in this study is robust.

Catalytic Oxidative Decomposition of Dimethyl Methyl Phosphonate over CuO/CeO2 Catalysts Prepared Using a Secondary Alkaline Hydrothermal Method

Bimetallic synergism plays an important role in lattice-doped catalysts. Therefore, lattice-doped bimetallic CuO/CeO2 catalysts were prepared by secondary alkaline hydrothermal reaction. During this process, the CeO2 nanomaterials were partially dissolved and recrystallized; thus, Cu ions were doped into the CeO2 lattice. The physical and chemical properties of CeO2, CuO/CeO2, and CuO were investigated. H2 temperature-programmed reduction characterization showed that the oxidation activity of CuO/CeO2 was significantly improved. X-ray photoelectron spectroscopy results showed that electron transfer occurred between Ce and Cu in the CuO/CeO2 catalyst. Additionally, Raman characterization confirmed the strong interaction between Cu and Ce. After CuO was loaded, the thermal catalytic decomposition performance of the catalyst was significantly improved with respect to the sarin simulant dimethyl methyl phosphonate (DMMP); with an increase in the Cu/Ce ratio, the performance first strengthened and then weakened. Additionally, the reaction tail gas and catalyst surface products were analyzed using mass spectrometry and ion chromatography, and the changes in the surface products during the thermal catalytic decomposition of DMMP were characterized at different temperatures using in situ diffuse reflectance infrared Fourier transform spectroscopy. Finally, the catalytic reaction pathways of DMMP on CeO2, CuO/CeO2, and CuO were inferred. The study results not only demonstrate an effective catalyst for the removal of nerve agent but also a feasible preparation method for lattice-doped bimetallic catalysts in the field of environmental protection.

Synthesis and Characterization of MnO2@Cellulose and Polypyrrole-Decorated MnO2@Cellulose for the Detection of Chemical Warfare Agent Simulant.

Chemical warfare agents (CWAs) have been threatening human civilization and its existence because of their rapid response, toxic, and irreversible nature. The hybrid nanostructured composites were synthesized by the hydrothermal process to detect the dimethyl methyl phosphonate (DMMP), a simulant of G-series nerve agents, especially sarin. Cellulose (CE), manganese oxide cellulose (MnO2@CE), and MnO2@CE/polypyrrole (PPy) exhibited a frequency shift of 0.4, 4.8, and 8.9 Hz, respectively, for a DMMP concentration of 25 ppm in the quartz crystal microbalance (QCM). In surface acoustic wave (SAW) sensor, they exhibited 187 Hz, 276 Hz, and 78 Hz, respectively. A comparison between CE, MnO2@CE, and MnO2@CE/PPy demonstrated that MnO2@CE/PPy possesses excellent linearity with a coefficient of determination (COD or R2) of 0.992 and 0.9547 in the QCM and SAW sensor. The hybrid composite materials showed a reversible adsorption and desorption phenomenon in the reproducibility test. The response and recovery times indicated that MnO2@CE/PPy showed the shortest response (~23 s) and recovery times (~42 s) in the case of the QCM sensor. Hence, the pristine CE and its nanostructured composites were compared to analyze the sensing performance based on sensitivity, selectivity, linearity, reproducibility, and response and recovery times to detect the simulant of nerve agents.

Thermal Catalytic Decomposition of Dimethyl Methyl Phosphonate Using CuO-CeO2/γ-Al2O3

Chemical warfare agents (CWAs) are highly toxic and fast-acting and are easy to cause large-scale poisoning to humans and livestock after being released. The activated carbon used for CWAs adsorption has disadvantages of limited adsorption capacity, easy aging and deactivation. Metal oxides have environmental stability, and they are characterized by long lasting and broad spectrum when used for thermal catalytic decomposition. Therefore, in this study, the supported copper–cerium catalyst CuO-CeO2/γ-Al2O3 was prepared using an equal volume impregnation method. The thermal catalytic decomposition performance was studied using sarin CWAs simulant dimethyl methyl phosphonate (DMMP) as the target compound. The results show that the CuO-CeO2/γ-Al2O3 catalyst with a CeO2 loading of 5% exhibited better thermal catalytic decomposition performance of DMMP. The catalyst provided protection against DMMP for 237 min at 350 °C; CuO was highly dispersed on CuO-5% CeO2/γ-Al2O3, and there was a strong interaction between Cu and Ce on CuO-5% CeO2/γ-Al2O3, which promoted the generation of surface-adsorbed oxygen, leading to a better thermal catalytic decomposition performance of DMMP. This study is expected to provide a reference for the study of catalysts for the thermal catalytic decomposition of CWAs.

Preparation of flame‐retardant rigid polyurethane foam with bio‐based phosphorus‐containing polyols and expandable graphite

AbstractIn the last decades, rigid polyurethane foam has focused on increasing renewable components and enhancing flame retardancy due to sustainable development and fire safety requirements. Herein, we report a bio‐based phosphorus‐containing polyester polyol (PMCP) that is synthesized with dimethyl methylphosphonate, malic acid, citric acid, and 1,6‐hexanediol in one pot. The hydroxyl value of PMCP is 485 ~ 512 mg KOH/g. As a result, it can be used as the sole polyol in the production of RPUF. Moreover, expandable graphite (EG) was incorporated into RPUF‐PMCP20 to enhance flame retardance. The limited oxygen index of RPUF increases from 18.3% to 24.0% with the rise in DMMP moiety in PMCP. Moreover, the peak heat release rate (PHRR) significantly decreases from 264.2 to 129 kW/m2. Meanwhile, the time to ignition increases from 5 to 18 s. The flame retardant mechanism indicated that PMCP plays a dual role in the gaseous and condensed phases. The addition of EG exhibits an excellent blocking effect. The LOI increases from 22.5% to 27.3% with increasing EG content. In addition, both the PHRR and smoke release rate of RPUF are suppressed by incorporating EG.

Reduced graphene oxide coated cotton e-textile for wearable chemical warfare agent sensors

A facile, safe, and scalable method for fabricating electrically conductive-reduced graphene oxide (rGO) e-fabric using a plasma-assisted coating process has been demonstrated. A wearable sensor based on rGO e-fabric was fabricated and used to detect and distinguish deadly chemical warfare agents (CWAs). The rGO e-fabric-based CWA sensor exhibited consistent responses upon repeated exposure to chemicals, including dimethyl methylphosphonate (DMMP) and soman (GD), which is a nerve agent. A difference in responses of the sensor toward GD and DMMP was observed. Theoretical studies further confirmed the potential of the as-prepared device as an e-fabric sensor for the detection of nerve agents. This novel functional e-fabric holds promise for future applications of wearable chemical agent sensors in smart personal protective suits.

Adsorptive degradation of dimethyl methylphosphonate over Zr-based metal–organic framework built from 3,3′,5,5′-azobenzenetetracarboxylic acid

Chemical warfare agents (CWAs) pose a significant threat to humans because of their high toxicity. Zirconium-based metal–organic frameworks (Zr-MOFs) are promising candidates for the purification and detoxification of CWAs. In this study, we prepared a Zr6O4(OH)8(H2O)4(abtc)2 denoted to Zr-abtc (abtc = 3,3′,5,5′-azobenzene-tetracarboxylate) under eco-friendly hydrothermal reflux conditions and investigated its detoxification performance. Dimethyl methylphosphonate (DMMP) was used as a simulant of a nerve agent to evaluate the adsorption performance of Zr–abtc. The Zr–abtc MOF was constructed from an 8-connected Zr6 cluster [Zr6(µ3-O)4(µ3-OH)4] with abtc as a linker, resulting in the generation of abundant surface hydroxyl groups, high porosity, and remarkable structural robustness under high moisture and high temperature conditions. The results of the breakthrough (BT) test of DMMP under dry and humid conditions reveal that Zr–abtc displays high DMMP adsorption performance with the adsorption capacity of 1.74 and 1.60 mmol/g under dry and humid condition, respectively. The high performance of Zr–abtc can be attributed to not only the strong interaction between the surface hydroxyl group of Zr–abtc MOF and DMMP but also the catalytic activity of the surface hydroxyl group to form the decomposed product of DMMP, as demonstrated using Fourier transform infrared spectroscopy (FTIR).

Analysis of Permeation Behaviors of Dimethyl Methyl Phosphonate Solutions and Influence on Mechanical Properties of Designed Double-Layer Peelable Coating

Analysis of Permeation Behaviors of Dimethyl Methyl Phosphonate Solutions and Influence on Mechanical Properties of Designed Double-Layer Peelable Coating

Experimental and theoretical study on the suppression effect of water mist containing dimethyl methylphosphonate (DMMP) on hydrogen jet flame

This work investigates the suppression effect of water mist containing dimethyl methylphosphonate (DMMP) on H2 jet flame. The flame appearances are analyzed and the flame temperature is recorded by a high-speed infrared camera. Results show that the suppression effect of water mist containing DMMP is better than that of pure water mist. To better understand the suppression effect of water mist containing DMMP, the burning velocity, heat production and free radicals are analyzed. Results indicate that suppressant could scavenge lots of free radicals to reduce the burning velocity in a wide range of equivalence ratios. Moreover, the influence of DMMP on lean CH4 and H2 flames is compared. Different with that of lean CH4 flame, the combustion parameters of lean H2 flame decline with DMMP addition. There is no combustion enhancement effect of DMMP on lean H2 flame. Because of the higher combustion intensity of lean H2 flame, the hydrocarbon in DMMP has little impact on the combustion. Furthermore, the reaction path of DMMP decomposition is analyzed. Results demonstrate that the rates of most phosphorus reactions in H2 flame are larger than that in CH4 flame. This work could provide foundation for improving the safety of hydrogen energy application.

Photonic Liquid Crystal Polymer Absorbent for Immobilization and Detection of Gaseous Nerve Agent Simulants

Detection and sequestration of chemical warfare agents (CWAs), such as poisonous organophosphates, are highly desirable for both personal security and environmental protection. However, both sensing and absorption in a single device have been rarely reported. In this study, we describe a photonic absorbent based on a cholesteric liquid crystal polymer as a dual sensing and decontamination device for gas-type CWAs. Dimethyl methylphosphonate (DMMP) was used as a simulant compound. A blue reflective photonic polymer was fabricated that was able to detect DMMP vapor through absorption. Hydrogen bond interactions between DMMP and mesogenic carboxylic groups of the polymer allow selectivity and capture. A distinct optical change of the film from blue to bright green indicates the absorption of DMMP vapor molecules and confirms when full absorption of the polymer is achieved. The diffusion of DMMP vapor into the material was observed by the formation of a sharp boundary between swollen and unswollen material, as evidenced by scanning electron microscopy images and the structural color changes. In ambient conditions, DMMP molecules are retained in the photonic absorbent without release to the environment. Heating above approximately 60 °C releases the absorbed DMMP, leading to a reusable optical device. These results confirm the ability of photonic polymers to sense and immobilize dangerous vapor, paving the way for the realization of simple, battery-free optical devices able to simultaneously warn and protect.

Nano-Sheet-like Morphology of Nitrogen-Doped Graphene-Oxide-Grafted Manganese Oxide and Polypyrrole Composite for Chemical Warfare Agent Simulant Detection.

Chemical warfare agents (CWAs) have inflicted monumental damage to human lives from World War I to modern warfare in the form of armed conflict, terrorist attacks, and civil wars. Is it possible to detect the CWAs early and prevent the loss of human lives? To answer this research question, we synthesized hybrid composite materials to sense CWAs using hydrothermal and thermal reduction processes. The synthesized hybrid composite materials were evaluated with quartz crystal microbalance (QCM) and surface acoustic wave (SAW) sensors as detectors. The main findings from this study are: (1) For a low dimethyl methyl phosphonate (DMMP) concentration of 25 ppm, manganese dioxide nitrogen-doped graphene oxide (NGO@MnO2) and NGO@MnO2/Polypyrrole (PPy) showed the sensitivities of 7 and 51 Hz for the QCM sensor and 146 and 98 Hz for the SAW sensor. (2) NGO@MnO2 and NGO@MnO2/PPy showed sensitivities of more than 50-fold in the QCM sensor and 100-fold in the SAW sensor between DMMP and potential interferences. (3) NGO@MnO2 and NGO@MnO2/PPy showed coefficients of determination (R2) of 0.992 and 0.975 for the QCM sensor and 0.979 and 0.989 for the SAW sensor. (4) NGO@MnO2 and NGO@MnO2/PPy showed repeatability of 7.00 ± 0.55 and 47.29 ± 2.69 Hz in the QCM sensor and 656.37 ± 73.96 and 665.83 ± 77.50 Hz in the SAW sensor. Based on these unique findings, we propose NGO@MnO2 and NGO@MnO2/PPy as potential candidate materials that could be used to detect CWAs.

Fabrication of dimethyl methylphosphonate-loaded mesoporous silica nano fire extinguisher and flame retarding unsaturated polyester

A novel nano fire extinguisher is constructed by loading the guest molecule (dimethyl methylphosphonate, DMMP) into the host material (mesoporous silica, m-SiO2) by a vacuum-assisted immersion method. SiO2-DMMP can avoid the excessive plasticization caused by the high addition of DMMP; under a relatively high addition amount (20 phr), the unsaturated polyester (UP) can normally be cured. 20 phr SiO2-DMMP imparts excellent flame retardancy to UP, i.e., 49.8% reduction in peak heat release rate and passing the UL-94 V-0 rating. Moreover, through the mesoporous confinement of m-SiO2, the thermal stability of DMMP is improved. In addition, easy migration of DMMP in UP is also solved; the UP can pass the UL-94 V-0 rating after soaking in water for 72 h. The flame retardant mechanism is the quenching mechanism. This strategy will be a universal method for loading liquid flame retardants to construct SiO2-based composite flame retardants.

On-site GC-QEPAS analysis on the scene of crime: The RISEN project

The capability to provide timely forensic analytical information is of paramount importance in criminal investigations involving chemical substances of toxicological interest. Miniaturized Gas Chromatography (GC) systems are suitable sensors to be deployed on the scene of crime, allowing to analyse specimens there, providing timely information to protect security and safety of specialists on-site and saving the time needed to collect, transport and analyse them in a forensic laboratory. An innovative hand-portable point sensor has been recently developed using a fully Micro-Electro-Mechanical-System (MEMS)-based compact-GC platform of the size of a few cm3 coupled to a miniaturized detector based on InfraRed Quartz Enhanced Photo Acoustic Spectroscopy (QEPAS). Sensing is based on the piezoelectric transduction of the photo-acoustic signal that is generated when laser radiation is absorbed by molecules in vapour phase in the QEPAS cell. Signal intensity is proportional to laser intensity, to the absorption cross section of the substance, and to its concentration. QEPAS spectra are very similar to the spectra obtained by classical IR absorption spectroscopy (IRAS), but, unlike IRAS cells, QEPAS cells can be designed as very cheap components of miniature size. The GC-QEPAS prototype is built upon a patented compact-GC architecture integrating three silicon micro-machined chips for sample pre-concentration, injection and GC separation and a QEPAS sensor based on a new ultra-wide tunability Quantum Cascade Laser (QCL) source, designed and assembled into a package matching the needs of hand-portability by the operator. The system was equipped with a compact air sampler, which also contains a first stage of pre-concentration, to allow vapour analysis on-site. Preliminary tests were carried out in a 60 litres glass box, where vaporizing solutions (between 1 and 100 microlitres) using a syringe of target substances. Sampling time was less than 60 seconds. The GC-QEPAS sensor was used to successfully analyse ppm and sub-ppm amounts of two nerve agent simulants: dimethyl methyl phosphonate (DMMP) and dipropylene glycol methyl ether (DPGME). Methyl salicylate (a blister agent simulant) and sulfur mustard (a real blister agent sample) were also tested. Other substances of interest in forensic toxicology where tested, including precursors of drugs of abuse. The sensor showed also its capability of analyzing amphetamine types stimulants (ATS) and drug precursors both as pure compounds and as mixtures. LoDs measured were in the order of about 10 ng for many precursors, and ten times larger for target compounds containing an amino group. Ethanol, propanol, gasoline and paint vapours at much higher concentrations, up to saturation vapor pressure, compared to the target chemical substances of forensic interest were also analysed to study the selectivity of the system in a real scenario. The miniature size of the column has allowed the separation of substances in cycle times of 2–3 minutes, to be compared with chemical substances eluting after retention times in the order of tens of minutes with traditional GC systems commonly used in forensic laboratories for casework. The total absorption chromatograms and the photoacoustic absorption spectra related to chromatographic peaks of both pure compounds and mixture will be shown, to demonstrate how the approach developed in the RISEN project will be able to support an improved approach to crime scene activities in the near future.

Miniaturized Photo-Ionization Fourier Deconvolution Ion Mobility Spectrometer for the Detection of Volatile Organic Compounds.

Because of its simplicity, reliability, and sensitivity, the drift tube ion mobility spectrometer (IMS) has been recognized as the equipment of choice for the on-site monitoring and identification of volatile organic compounds (VOCs). However, the performance of handheld IMS is often limited by the size, weight, and drift voltage, which heavily determine the sensitivity and resolving power that is crucial for the detection and identification of VOCs. In this work, we present a low-cost, miniaturized drift tube ion mobility spectrometer incorporated with a miniaturized UV ionization lamp and a relatively low drift voltage. The sensitivity and resolving power are boosted with the implementation of Fourier deconvolution multiplexing compared to the conventional signal averaging data acquisition method. The drift tube provides a high resolving power of up to 52 at a drift length of 41 mm, 10 mm ID dimensions, and a drift voltage of 1.57 kV. Acetone, benzene, dimethyl methyl phosphonate, methyl salicylate, and acetic acid were evaluated in the developed spectrometer and showed satisfactory performance.