Chemical Sniffing Instrumentation for Security Applications

Detection of Volatile Organic Compounds with Secondary Electrospray Ionization and Proton Transfer Reaction High-Resolution Mass Spectrometry: A Feature Comparison

The analysis of volatiles is of high relevance for a wide range of applications from environmental air sampling and security screening to potential medical applications. High-resolution mass spectrometry methods offer a particularly wide compound coverage, sensitivity, and selectivity. Online approaches allow direct analysis in real time without the need for sample preparation. For the first time, we systematically compared the analysis of volatile organic compounds with secondary electrospray ionization (SESI) and proton transfer reaction (PTR) high-resolution mass spectrometry. The selected instruments had comparable mass resolving powers with m/Δm ≥ 15000, which is particularly suitable for nontargeted analysis, for example, of exhaled breath. Exhalations from 14 healthy adults were analyzed simultaneously on both instruments. In addition, 97 reference standards from nine chemical classes were analyzed with a liquid evaporation system. Surprisingly, in breath, we found more complementary than overlapping features. A clear mass dependence was observed for each method with the highest number of detected m/z features for SESI in the high mass region (m/z = 150-250) and for PTR in the low mass region (m/z = 50-150). SESI yielded a significantly higher numbers of peaks (828) compared to PTR (491) among a total of 1304 unique breath m/z features. The number of signals observed by both methods was lower than expected (133 features) with 797 unique SESI features and 374 unique PTR features. Hypotheses to explain the observed mass-dependent differences are proposed.

Uranyl Organic Framework as a Highly Selective and Sensitive Turn-on and Turn-off Luminescent Sensor for Dual Functional Detection Arginine and MnO4. Inorg Chem 2020;59:5004-5017. [PMID: 32207299 DOI: 10.1021/acs.inorgchem.0c00236]

Five new uranyl coordination polymers were prepared by the hydrothermal method based on 5-nitroisophthalic acid (H₂nip) as (UO₂)(nip)(2,2'-bpy) (1), (H₂4,4'-bpy)·[(UO₂)₃(nip)₄]·(4,4'-bpy) (2), (H₂bpe)·[(UO₂)_0.5(nip)] (3), (H₂ bpp)·[(UO₂)₂-(nip)₃]·H₂O (4), and (H₂tmp)·[(UO₂)(nip)₂](5) [2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine, bpe = 4,4'-vinylenedipyridine, bpp = 4,4' -trimethylenedipyridine, tmp = tetramethylpyrazine]. All of these synthesized complexes have been characterized by single crystal and powder X-ray diffraction, IR spectra, thermogravimetric analysis, elemental analysis, and luminescent properties. In particular, it is found that compounds 1 and 4 can be used as a luminescent sensor to efficiently detect arginine in aqueous solution by means of "turn-on"; the detection limits were 1.06 × 10^-6 and 6.42 × 10^-6 mol/L, respectively. Moreover, 4 can also be used as a bifunctional sensor for selective sensing of MnO₄^- anion by "turn-off". The detection limit of MnO₄^- in water was 1.79 × 10^-6 mol/L; the K_sv was 1.88 × 10⁴. The sensing effect of arginine in simulated grape juice samples and MnO₄^- in simulated river water samples was also investigated by this sensing system with high recovery. In addition, the possible mechanism of sensing arginine and MnO₄^- in the aqueous solution was discussed.

A Colorimetric Artificial Olfactory System for Airborne Improvised Explosive Identification

The detection of ultralow or nonvolatile target analytes remains a significant challenge for artificial olfactory systems even after decades of development, which severely limits their widespread application. To overcome this challenge, an artificial olfactory system based on a colorimetric hydrogel array is constructed for the first time as a universal representative. As an effective extension of conventional artificial olfactory systems that integrates the merits of its predecessors, the proposed system accurately mimics olfactory mucosa and specific odorant binding proteins using hydrogels endowed with specific colorimetric reagents for the detection of hypochlorite, chlorate, perchlorate, urea, and nitrate. Therefore, the proposed system is capable of detecting and discriminating between these five airborne improvised explosive microparticulates with a detection limit as low as 39.4 pg. Additionally, the system demonstrates good reusability over ten cycles, rapid response time of ≈0.2 s, and excellent discrimination properties, despite significant variation. This proof-of-concept study on colorimetric artificial olfactory systems yields a novel strategy for the direct and discriminative detection of nonvolatile airborne microparticulates.

Detection of cocaine on euro banknotes; Development of a practical approach for the interpretation of suspect cases

The presence of traces of narcotics, particularly cocaine, on banknotes in circulation is a known and widespread fact in all countries. While linked to consumption and trafficking (primary contamination), their spread is due to direct contact with other banknotes during machine counting and cash financial transactions. The mere detection of traces of cocaine on a sample of banknotes is therefore not sufficient evidence to establish the banknote's illegal origin. Increasing levels of contamination are recorded close to (in terms of both place and time) the first direct contact with the substance. The analysis must thus be able to demonstrate that the concentration of narcotics on the banknotes is significantly higher (statistically) in terms of value and frequency than would be expected from background noise alone. Even in that event, however, this evidence has to be substantiated with additional confirmations linking banknotes to the person and this latter to drug trafficking and/or dealing. In general, an in-depth and systematic analysis of all seized banknotes to search for traces of narcotics is not only prohibitive in terms of cost, but also unnecessary. If the sampling procedure is respected, the Swiss Federal Supreme Court actually recognizes IMS (ion mobility spectrometry) as a lawful method for checking the degree of banknote contamination, as well as all the statistical conclusions that can be drawn from it. In special cases, the prosecutor may require confirmation of IMS results by a laboratory test (liquid/gas chromatography-mass spectrometry). Using a non-destructive sampling procedure (suction on swabs) we determined the presence of cocaine on 978 circulating euro banknotes, randomly collected at 5 swiss customs offices, with IMS and LC-MS/MS in order to establish a normal (background) contamination level. A significant proportion (46.4%) of the euro banknotes analysed by LC-MS/MS had cocaine concentrations above the quantification limit (1 ng/swab). However, the extent of contamination is a determining factor: 94.6% of the banknotes in circulation have cocaine concentrations equal to or less than 10 ng/swab and only 3.4% have cocaine concentrations above 20 ng/swab. By comparison, only 27.3% and 13.4% respectively of the seized banknotes (2 real cases) had cocaine concentrations equal to or less than 10 ng/swab, but 63.5% and 86.7% respectively had cocaine concentrations above 20 ng/swab. We also describe a Komolgorov-Smirnov test model used to determine the presence of an "abnormal" level of contamination relative to the reference banknotes (banknotes in circulation or background noise) effectively and within realistic practical and theoretical frameworks. This model provides a quantifiable and statistically significant result that not only simplifies data interpretation, but also facilitates admissibility as forensic evidence in proceedings. When applied to the sized banknotes using both IMS and LC-MS/MS data, we obtain fully consistent and sounding conclusions.

Active Self-Assembled Monolayer Sensors for Trace Explosive Detection

Trace explosives can be detected with the help of a portable device using a flexible active self-assembled monolayer (SAM). 9,10-diphenyl anthracene with aggregation-induced emission enhancement (AIEE) properties is selected as the fluorophore. Phosphoric acid as the anchor group is linked to the fluorophore through an alkyl chain and able to self-assemble into a dense monolayer on the HfO₂ adhesion layer on a flexible substrate. The dense SAMs show high fluorescence intensity, which can be quenched by nitroaromatic compounds (NACs), and have advantages of high response rate, sensitivity, reversibility, and selectivity.

TPE-containing amphiphilic block copolymers: synthesis and application in the detection of nitroaromatic pollutants

Two AIE block copolymers termed P1 and P2 bearing TPE and PEG-based chains were synthesized with moderate molecular weights and narrow PDIs via RAFT polymerization. Both P1 and P2 can be used in the fluorescence detection of nitroaromatic compounds (NACs) and cell images.

On-Line Analysis of Exhaled Breath Focus Review

On-line analysis of exhaled breath offers insight into a person's metabolism without the need for sample preparation or sample collection. Due to its noninvasive nature and the possibility to sample continuously, the analysis of breath has great clinical potential. The unique features of this technology make it an attractive candidate for applications in medicine, beyond the task of diagnosis. We review the current methodologies for on-line breath analysis, discuss current and future applications, and critically evaluate challenges and pitfalls such as the need for standardization. Special emphasis is given to the use of the technology in diagnosing respiratory diseases, potential niche applications, and the promise of breath analysis for personalized medicine. The analytical methodologies used range from very small and low-cost chemical sensors, which are ideal for continuous monitoring of disease status, to optical spectroscopy and state-of-the-art, high-resolution mass spectrometry. The latter can be utilized for untargeted analysis of exhaled breath, with the capability to identify hitherto unknown molecules. The interpretation of the resulting big data sets is complex and often constrained due to a limited number of participants. Even larger data sets will be needed for assessing reproducibility and for validation of biomarker candidates. In addition, molecular structures and quantification of compounds are generally not easily available from on-line measurements and require complementary measurements, for example, a separation method coupled to mass spectrometry. Furthermore, a lack of standardization still hampers the application of the technique to screen larger cohorts of patients. This review summarizes the present status and continuous improvements of the principal on-line breath analysis methods and evaluates obstacles for their wider application.

Pyrenyl-Functionalized Polysiloxane Based on Synergistic Effect for Highly Selective and Highly Sensitive Detection of 4-Nitrotoluene

4-Nitrotoluene (NT) is an important intermediate for the manufacture of dyes, agricultural chemicals, medicaments, and synthetic fibers. But its wide use has resulted in a series of ecological problems and health issues due to high toxicity, mutagenicity, and carcinogenicity. However, no fluorescent probes with high selectivity and high sensitivity to NT has been reported yet, and the current probes usually prefer to detect multi-nitrosubstituted nitroaromatic compounds (NACs) including 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol. Herein, we report a series of pyrene-functionalized polysiloxanes with high selectivity and high sensitivity to NT. Pyrene was introduced into polysiloxane through a carbon-carbon double bond, and the formed rigid side-chain fluorophore and flexible backbone structure of polysiloxane provide an ideal platform for the highly selective detection of NT. We further explored the possible response mechanism and speculated that the high selectivity and high sensitivity were derived from the synergistic effect between steric hindrance and dipolar interaction. In addition, paper sensors based on the obtained fluorescent materials were fabricated and change in their high sensitivity and visible fluorescence indicated that the paper sensor is a simple testing tool for portable and visual detection of NT. Furthermore, the design strategy in this work provides a novel synthetic route to synthesize other fluorescent probes with unique selectivity to NACs detection.

Low-cost photoionization sensors as detectors in GC × GC systems designed for ambient VOC measurements

Conventional volatile organic compound (VOC) monitoring based on thermal desorption - gas chromatography-mass spectrometry (TD-GC-MS) or gas chromatography-flame ionization detector (TD-GC-FID) is relatively cumbersome and expensive. In this study commercial off the shelf low-cost and low-power photo-ionization detector (PID) sensors are used as simple detectors in VOC analysis systems based on GC, including a miniaturised GC × GC device with portable, low-cost, and low-energy-consumption features. PID sensors produce a voltage signal positively proportional to VOC concentration, which when incorporated into a TD-GC system gave limit of detection of 0.02 ppbV for isoprene. To test PID performance in real-world applications, PID sensors were deployed as (i) a second alternative detector in a GC-Quadruple Time Of Flight Mass spectrometry (GC-Q-TOF-MS), and (ii) the main detector in a compact two-dimensional gas chromatograph (GC × GC). PID sensors with 10.6 eV and 11.7 eV lamps were used to measure eight toxic chemicals including organic sulfide and organic phosphonates via GC; two species were ionized by a 10.6 eV lamp and four species by the 11.7 eV lamp. Commercially available low-cost PIDs designed for standalone could be straightforwardly and effectively re-used as detectors in compact GC × GC systems, in this work showing excellent VOC sensitivity, fast response and low operational demands compared to comparable field instruments based on GC-FID or MS.

Reactive Olfaction Ambient Mass Spectrometry

Chemical ionization of organic compounds with negligible vapor pressures (VP) is achieved at atmospheric pressure when the proximal sample is exposed to corona discharge. The vapor-phase analyte is produced through a reactive olfaction process, which is determined to include electrostatic charge induction in the proximal condensed-phase sample, resulting in the liberation of free particles. With no requirement for physical contact, a new contained nano-atmospheric pressure chemical ionization (nAPCI) source was developed that allowed direct mass spectrometry analysis of complex mixtures at a sample consumption rate less than nmol/min. The contained nAPCI source was applied to analyze a wide range of samples including the detection of 1 ng/mL cocaine in serum and 200 pg/mL caffeine in raw urine, as well as the differentiation of chemical composition of perfumes and beverages. Polar (e.g., carminic acid; estimated VP 5.1 × 10^-25 kPa) and nonpolar (e.g., vitamin D2; VP 8.5 × 10^-11 kPa) compounds were successfully ionized by the contained nAPCI ion source under ambient conditions, with the corresponding ion types of 78 other organic compounds characterized.

In-Situ Analysis of Essential Fragrant Oils Using a Portable Mass Spectrometer

A portable mass spectrometer was coupled to a direct inlet membrane (DIM) probe and applied to the direct analysis of active fragrant compounds (3-methylbutyl acetate, 2-methyl-3-furanthiol, methyl butanoate, and ethyl methyl sulfide) in real time. These fragrant active compounds are commonly used in the formulation of flavours and fragrances. Results obtained show that the portable mass spectrometer with a direct membrane inlet can be used to detect traces of the active fragrant compounds in complex mixtures such as essential fragrant oils and this represents a novel in-situ analysis methodology. Limits of detection (LOD) in the sub-ppb range (< 2.5 pg) are demonstrated. Standard samples in the gaseous phase presented very good linearity with RSD % at 5 to 7 for the selected active fragrant compounds (i.e., isoamyl acetate, 2-methyl-3-furanthiol, methyl butanoate, and methyl ethyl sulphide). The rise and fall times of the DIM probe are in the ranges from 15 to 31 seconds and 23 to 41 seconds, respectively, for the standard model compounds analysed. The identities of the fragrance active compounds in essential oil samples (i.e., banana, tangerine, papaya, and blueberry muffin) were first identified by comparison with a standard fragrance compounds mixture using their major fragment peaks, the NIST standard reference library, and gas chromatography mass spectrometry (GC-MS) analysis. No sample preparation is required for analysis using a portable mass spectrometer coupled to a DIM probe, so the cycle time from ambient air sampling to the acquisition of the results is at least 65 seconds.

Preconcentration techniques for trace explosive sensing

Trace sensing of explosive vapours is a method in humanitarian demining and Improvised Explosive Device (IED) detection that has received increasing attention recently, since accurate, fast, and reliable chemical detection is highly important for threat identification. However, trace molecule sampling in the field can be extremely difficult due to factors including weather, locale, and very low vapour pressure of the explosive. Preconcentration of target molecules onto a substrate can provide a method to collect higher amounts of analyte for analysis. We used the commercial fluoropolymer Aflas as a preconcentrator material to sorb explosive molecules to the surface, allowing subsequent detection of the explosives via the luminescence quenching response from the organic polymer Super Yellow. The preconcentration effect of Aflas was confirmed and characterised with 2,4-DNT, prior to field sampling being conducted at a test minefield in Croatia by placing preconcentration strips in the entrance of beehives, where honeybees have collected explosive materials during free-flying. In this work we show for the first time a method for confirmation of landmines combining honeybee colonies containing a preconcentration material and subsequent monitoring of luminescence quenching.

Volatolomics: A broad area of experimentation

Chemical analysis (detection and monitoring) of compounds associated with the metabolic activities of an organism is at the cutting edge of science. Volatile metabolomics (volatolomics) are applied in a broad range of applications including: biomedical research (e.g. disease diagnostic tools, personalized healthcare and nutrition, etc.), toxicological analysis (e.g. exposure tool to environmental pollutants, toxic and hazardous chemical environments, industrial accidents, etc.), molecular communications, forensics, safety and security (e.g. search and rescue operations). In the present review paper, an overview of recent advances and applications of volatolomics will be given. The main focus will be on volatile organic compounds (VOCs) originating from biological secretions of various organisms (e.g. microorganisms, insects, plants, humans) and resulting fusion of chemical information. Bench-top and portable or field-deployable technologies-systems will also be presented and discussed.

Detection of chemical warfare agent simulants and hydrolysis products in biological samples by paper spray mass spectrometry

Paper spray ionization coupled to a high resolution tandem mass spectrometer (a quadrupole orbitrap) was used to identify and quantitate chemical warfare agent (CWA) simulants and their hydrolysis products in blood and urine. Three CWA simulants, dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), and diisopropyl methylphosphonate (DIMP), and their isotopically labeled standards were analyzed in human whole blood and urine. Calibration curves were generated and tested with continuing calibration verification standards. Limits of detection for these three compounds were in the low ng mL^-1 range for the direct analysis of both blood and urine samples. Five CWA hydrolysis products, ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA), isobutyl methylphosphonic acid (iBuMPA), cyclohexyl methylphosphonic acid (CHMPA), and pinacolyl methylphosphonic acid (PinMPA), were also analyzed. Calibration curves were generated in both positive and negative ion modes. Limits of detection in the negative ion mode ranged from 0.36 ng mL^-1 to 1.25 ng mL^-1 in both blood and urine for the hydrolysis products. These levels were well below those found in victims of the Tokyo subway attack of 2 to 135 ng mL^-1. Improved stability and robustness of the paper spray technique in the negative ion mode was achieved by the addition of chlorinated solvents. These applications demonstrate that paper spray mass spectrometry (PS-MS) can be used for rapid, sample preparation-free detection of chemical warfare agents and their hydrolysis products at physiologically relevant concentrations in biological samples.

Novel Membrane Detector Based on Smart Nanogels for Ultrasensitive Detection of Trace Threat Substances

A novel membrane detector is developed by a facile strategy combining commercialized membrane and smart nanogels for ultrasensitive and highly selective real-time detection of trace threat substances. On the basis of nanogel filtration and polydopamine adhesion, the membrane detector is fabricated by simply immobilizing smart nanogels onto the multiple pores of a commercialized membrane as the nanosensors and nanovalves. This is demonstrated by incorporating Pb²⁺-responsive poly( N-isopropylacrylamide- co-acryloylamidobenzo-18-crown-6) nanogels in the straight pores of a commercialized polycarbonate membrane for ultrasensitive and highly selective real-time detection of trace Pb²⁺. When selectively recognizing the Pb²⁺ in solution, the smart nanogels in the membrane pores swell, which lead to trans-membrane flux change. Quantitative detection of Pb²⁺ concentration can be achieved by simply measuring the flow rate of the trans-membrane flow. Due to the multiple nanochannels of nanogel-immobilized pores in the membrane for Pb²⁺ sensing and flux regulating, ultrasensitive and highly selective real-time detection of trace Pb²⁺ with concentration as low as 10^-10 mol L^-1 can be achieved. The nanogel-immobilized membrane detector offers a flexible platform to create versatile new membrane detectors by incorporating diverse smart nanogels for ultrasensitive and highly selective real-time detection of different trace threat substances.

Protein- and Peptide-Based Biosensors in Artificial Olfaction

Animals' olfactory systems rely on proteins, olfactory receptors (ORs) and odorant-binding proteins (OBPs), as their native sensing units to detect odours. Recent advances demonstrate that these proteins can also be employed as molecular recognition units in gas-phase biosensors. In addition, the interactions between odorant molecules and ORs or OBPs are a source of inspiration for designing peptides with tunable odorant selectivity. We review recent progress in gas biosensors employing biological units (ORs, OBPs, and peptides) in light of future developments in artificial olfaction, emphasizing examples where biological components have been employed to detect gas-phase analytes.

Progress in the development of olfactory-based bioelectronic chemosensors

Artificial chemosensory devices have a wide range of applications in industry, security, and medicine. The development of these devices has been inspired by the speed, sensitivity, and selectivity by which the olfactory system in animals can probe the chemical nature of the environment. In this review, we examine how molecular and cellular components of natural olfactory systems have been incorporated into artificial chemosensors, or bioelectronic sensors. We focus on the biological material that has been combined with signal transduction systems to develop artificial chemosensory devices. The strengths and limitations of different biological chemosensory material at the heart of these devices, as well as the reported overall effectiveness of the different bioelectronic sensor designs, is examined. This review also discusses future directions and challenges for continuing to advance development of bioelectronic sensors.

Nanosensors for water quality monitoring

Nanomaterial-enabled sensors are being designed for high-efficiency, multiplex-functionality and high-flexibility sensing applications. Many existing nanosensors have the inherent capacity to achieve such goals; however, they require further development into consumer- and operator-friendly tools with the ability to detect analytes in previously inaccessible locations, as well as at a greater scale than heretofore possible. Here, I discuss how nanotechnology-enabled sensors have great, as yet unmet, promise to provide widespread and potentially low-cost monitoring of chemicals, microbes and other analytes in drinking water.

A Mass Spectrometer in Every Fume Hood

Since their inception, mass spectrometers have played a pivotal role in the direction and application of synthetic chemical research. The ability to develop new instrumentation to solve current analytical challenges in this area has always been at the heart of mass spectrometry, although progress has been slow at times. Herein, we briefly review the history of how mass spectrometry has been used to approach challenges in organic chemistry, how new developments in portable instrumentation and ambient ionization have been used to open novel areas of research, and how current techniques have the ability to expand on our knowledge of synthetic mechanisms and kinetics. Lastly, we discuss the relative paucity of work done in recent years to embrace the concept of improving benchtop synthetic chemistry with mass spectrometry, the disconnect between applications and fundamentals within these studies, and what hurdles still need to be overcome. Graphical Abstract.

Non-contact identification and differentiation of illicit drugs using fluorescent films

Sensitive and rapid identification of illicit drugs in a non-contact mode remains a challenge for years. Here we report three film-based fluorescent sensors showing unprecedented sensitivity, selectivity, and response speed to the existence of six widely abused illicit drugs, including methamphetamine (MAPA), ecstasy, magu, caffeine, phenobarbital (PB), and ketamine in vapor phase. Importantly, for these drugs, the sensing can be successfully performed after 5.0 × 10⁵, 4.0 × 10⁵, 2.0 × 10⁵, 1.0 × 10⁵, 4.0 × 10⁴, and 2.0 × 10² times dilution of their saturated vapor with air at room temperature, respectively. Also, presence of odorous substances (toiletries, fruits, dirty clothes, etc.), water, and amido-bond-containing organic compounds (typical organic amines, legal drugs, and different amino acids) shows little effect upon the sensing. More importantly, discrimination and identification of them can be realized by using the sensors in an array way. Based upon the discoveries, a conceptual, two-sensor based detector is developed, and non-contact detection of the drugs is realized.

Sensitive and rapid identification of illicit drugs in a non-contact mode remains a challenge. Here, the authors report three film-based fluorescent sensors showing remarkable sensitivity, selectivity and response speed to six widely abused illicit drugs in vapor phase.

Sniffing Entrapped Humans with Sensor Arrays

Earthquakes are lethal natural disasters frequently burying people alive under collapsed buildings. Tracking entrapped humans from their unique volatile chemical signature with hand-held devices would accelerate urban search and rescue (USaR) efforts. Here, a pilot study is presented with compact and orthogonal sensor arrays to detect the breath- and skin-emitted metabolic tracers acetone, ammonia, isoprene, CO2, and relative humidity (RH), all together serving as sign of life. It consists of three nanostructured metal-oxide sensors (Si-doped WO3, Si-doped MoO3, and Ti-doped ZnO), each specifically tailored at the nanoscale for highly sensitive and selective tracer detection along with commercial CO2 and humidity sensors. When tested on humans enclosed in plethysmography chambers to simulate entrapment, this sensor array rapidly detected sub-ppm acetone, ammonia, and isoprene concentrations with high accuracies (19, 21, and 3 ppb, respectively) and precision, unprecedented by portable sensors but required for USaR. These results were in good agreement (Pearson's correlation coefficients ≥0.9) with benchtop selective reagent ionization time-of-flight mass spectrometry (SRI-TOF-MS). As a result, an inexpensive sensor array is presented that can be integrated readily into hand-held or even drone-carried detectors for first responders to rapidly screen affected terrain.

Analysis of the Precursors, Simulants and Degradation Products of Chemical Warfare Agents

Recent advances in analysis of precursors, simulants and degradation products of chemical warfare agents (CWA) are reviewed. Fast and reliable analysis of precursors, simulants and CWA degradation products is extremely important at a time, when more and more terrorist groups and radical non-state organizations use or plan to use chemical weapons to achieve their own psychological, political and military goals. The review covers the open source literature analysis after the time, when the chemical weapons convention had come into force (1997). The authors stated that during last 15 years increased number of laboratories are focused not only on trace analysis of CWA (mostly nerve and blister agents) in environmental and biological samples, but the growing number of research are devoted to instrumental analysis of precursors and degradation products of these substances. The identification of low-level concentration of CWA degradation products is often more important and difficult than the original CWA, because of lower level of concentration and a very large number of compounds present in environmental and biological samples. Many of them are hydrolysis products and are present in samples in the ionic form. For this reason, two or three instrumental methods are used to perform a reliable analysis of these substances.

Molecular Communication over Gas Stream Channels using Portable Mass Spectrometry

The synthetic generation/coding and transmission of olfactory information over a gas stream or an odor network is a new and unexplored field. Application areas vary from the entertainment or advertisement industry to security and telemedicine. However, current technological limitations frustrate the accurate reproduction of decoded and transmitted olfactory data. This study describes the development, testing, and characterization of a novel odor emitter (OE) that is used to investigate the generation-encoding of gaseous standards with odorous characteristics with a regulatable way, for scent transmission purposes. The calibration and the responses of a developed OE were examined using a portable quadrupole mass spectrometer (MS). Experiments were undertaken for a range of volatile organic compounds (VOCs) at different temperatures and flow rates. Individual compounds and mixtures were tested to investigate periodic and dynamic transmission characteristics within two different size tubular containers for distances up to 3 m. Olfactory information transmission is demonstrated using MS as the main molecular sensor for odor detection and monitoring and for the first time spatial encryption of olfactory information is shown. Graphical Abstract ᅟ.

Strong Blue Emissive Supramolecular Self-Assembly System Based on Naphthalimide Derivatives and Its Ability of Detection and Removal of 2,4,6-Trinitrophenol

Two simple and novel gelators (G-P with pyridine and G-B with benzene) with different C-4 substitution groups on naphthalimide derivatives have been designed and characterized. Two gelators could form organogels in some solvents or mixed solvents. The self-assembly processes of G-P in a mixed solvent of acetonitrile/H₂O (1/1, v/v) and G-B in acetonitrile were studied by means of electron microscopy and spectroscopy. The organogel of G-P in the mixed solvent of acetonitrile/H₂O (1/1, v/v) formed an intertwined fiber network, and its emission spectrum had an obvious blue shift compared with that of solution. By contrast, the organogel of G-B in acetonitrile formed a straight fiber, and its emission had an obvious red shift compared with that of solution. G-P and G-B were employed in detecting nitroaromatic compounds because of their electron-rich property. G-P is more sensitive and selective toward 2,4,6-trinitrophenol (TNP) compared with G-B. The sensing mechanisms were investigated by ¹H NMR spectroscopic experiments and theoretical calculations. From these experimental results, it is proposed that electron transfer occurs from the electron-rich G-P molecule to the electron-deficient TNP because of the possibility of complex formation between G-P and TNP. The G-P molecule could detect TNP in water, organic solvent media, as well as using test strips. It is worth mentioning that the organogel G-P can not only detect TNP but also remove TNP from the solution into the organogel system.

A Simple and Inexpensive Electrochemical Assay for the Identification of Nitrogen Containing Explosives in the Field

We report a simple and inexpensive electrochemical assay using a custom built hand-held potentiostat for the identification of explosives. The assay is based on a wipe test and is specifically designed for use in the field. The prototype instrument designed to run the assay is capable of performing time-resolved electrochemical measurements including cyclic square wave voltammetry using an embedded microcontroller with parts costing roughly $250 USD. We generated an example library of cyclic square wave voltammograms of 12 compounds including 10 nitroaromatics, a nitramine (RDX), and a nitrate ester (nitroglycine), and designed a simple discrimination algorithm based on this library data for identification.

Analytical Validation of a Portable Mass Spectrometer Featuring Interchangeable, Ambient Ionization Sources for High Throughput Forensic Evidence Screening

Forensic evidentiary backlogs are indicative of the growing need for cost-effective, high-throughput instrumental methods. One such emerging technology that shows high promise in meeting this demand while also allowing on-site forensic investigation is portable mass spectrometric (MS) instrumentation, particularly that which enables the coupling to ambient ionization techniques. While the benefits of rapid, on-site screening of contraband can be anticipated, the inherent legal implications of field-collected data necessitates that the analytical performance of technology employed be commensurate with accepted techniques. To this end, comprehensive analytical validation studies are required before broad incorporation by forensic practitioners can be considered, and are the focus of this work. Pertinent performance characteristics such as throughput, selectivity, accuracy/precision, method robustness, and ruggedness have been investigated. Reliability in the form of false positive/negative response rates is also assessed, examining the effect of variables such as user training and experience level. To provide flexibility toward broad chemical evidence analysis, a suite of rapidly-interchangeable ion sources has been developed and characterized through the analysis of common illicit chemicals and emerging threats like substituted phenethylamines. Graphical Abstract ᅟ.

Pt(II)C∧N∧N-Based Luminophore-Micelle Adducts for Sensing Nitroaromatic Explosives

Two luminescent cyclometalated Pt(II)-complexes, 1•Pt and 2•Pt, respectively, were synthesized by using unsymmetrical C^∧N^∧N ligands having different alkyl substituents. These π-electron-rich complexes are used for sensing various electron deficient nitroaromatic explosives, e.g., 4-nitrotoluene (NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and 2,4,6-trinitrophenol (TNP), in aqueous, nonaqueous, as well as in the solid state as a paper strip with maximum detection limit of ca. 10^-9 M. It was demonstrated that the sparingly soluble 2•Pt complex becomes water-soluble in the presence of all kinds of surfactants, viz., cationic (e.g., cetyltrimethylammonium bromide, CTAB), anionic (e.g., sodium dodecyl sulfate, SDS), and neutral (e.g., Triton X-100). This may be due to the incorporation of its long lyophilic tail group (-C₁₂H₂₅) inside the micellar core, exposing planar Pt(II)C^∧N^∧N headgroup to the aqueous bulk phase. It was also observed that the extent of solubility of these Pt(II)-complexes in micellar media strongly depends on the length of the existing alkyl chain. For instance, the presence of longer dodecyl chain makes 2•Pt complex ca. 1000-fold more soluble than the complex 1•Pt, which contains a shorter propyl chain. Their sensing behavior essentially arises by the quenching of Pt(II)-based intense luminescence due to the supramolecular charge transfer (CT) process originating from Pt(II)C^∧N^∧N-antenna to the electron deficient nitroaromatic explosives. Our present work shows that the micellar adducts formed by highly luminophoric material and surfactant molecules could effectively detect such explosives in aqueous medium with better sensitivity compared to what were observed in other media.

Autonomous Multi-Robot Search for a Hazardous Source in a Turbulent Environment

Finding the source of an accidental or deliberate release of a toxic substance into the atmosphere is of great importance for national security. The paper presents a search algorithm for turbulent environments which falls into the class of cognitive (infotaxi) algorithms. Bayesian estimation of the source parameter vector is carried out using the Rao-Blackwell dimension-reduction method, while the robots are controlled autonomously to move in a scalable formation. Estimation and control are carried out in a centralised replicated fusion architecture assuming all-to-all communication. The paper presents a comprehensive numerical analysis of the proposed algorithm, including the search-time and displacement statistics.

Application of the Transpiration Method To Determine the Vapor Pressure and Related Physico-Chemical Data of Low Volatile, Thermolabile, and Toxic Organo(thio)phosphates

The present work represents the most recent study on the physico-chemical properties of the organophosphate compound class being directly related to the Chemical Weapons Convention (CWC). This compound class is of great importance in the ongoing conflict in Syria. Here, the vapor pressure of the deadly organo(thio)phosphate Amiton and seven of its derivatives was investigated. These medium to low volatile analytes pose a potential threat toward human life by inhalation or direct contact with the skin at very low doses. Therefore, the vapor pressures in ambient temperature regimes were measured by utilizing the transpiration method to determine the saturation vapor pressure p_sat and the enthalpy of vaporization Δ_l^gH_m^° at 298.15 K. We also successfully applied the transpiration method for the examination of thermolabile compounds. In particular, five of the molecules can undergo a thiono-thiolo rearrangement at elevated temperatures within a couple of hours and thus could possibly alter in the course of the experiment. In addition we demonstrate that the concentration under diffusion conditions, c_dif, is a useful parameter for the choice of suitable gas phase detection equipment for Amiton and its derivatives, because it can be directly compared with the limit of detection LOD [ng L^-1] of the device used. Finally, we proved the transpiration method to be applicable for the investigation of toxic and also high boiling and even thermolabile chemicals in general.

Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization

Venturi-assisted ENTrainment and Ionization (VENTI) was developed, demonstrating efficient entrainment, collection, and transport of remotely sampled vapors, aerosols, and dust particulate for real-time mass spectrometry (MS) detection. Integrating the Venturi and Coandă effects at multiple locations generated flow and analyte transport from non-proximate locations and more importantly enhanced the aerodynamic reach at the point of collection. Transport through remote sampling probes up to 2.5 m in length was achieved with residence times on the order of 10^-2 s to 10^-1 s and Reynolds numbers on the order of 10³ to 10⁴. The Venturi-assisted entrainment successfully enhanced vapor collection and detection by greater than an order of magnitude at 20 cm stand-off (limit of simple suction). This enhancement is imperative, as simple suction restricts sampling to the immediate vicinity, requiring close proximity to the vapor source. In addition, the overall aerodynamic reach distance was increased by approximately 3-fold over simple suction under the investigated conditions. Enhanced aerodynamic reach was corroborated and observed with laser-light sheet flow visualization and schlieren imaging. Coupled with atmospheric pressure chemical ionization (APCI), the detection of a range of volatile chemical vapors; explosive vapors; explosive, narcotic, and mustard gas surrogate (methyl salicylate) aerosols; and explosive dust particulate was demonstrated. Continuous real-time Venturi-assisted monitoring of a large room (approximately 90 m² area, 570 m³ volume) was demonstrated for a 60-min period without the remote sampling probe, exhibiting detection of chemical vapors and methyl salicylate at approximately 3 m stand-off distances within 2 min of exposure.

Towards on-site analysis of complex matrices by solid-phase microextraction-transmission mode coupled to a portable mass spectrometer via direct analysis in real time

On-site analysis of complex matrices by SPME-TM coupled to a portable mass spectrometer via DART.