Detection of sulfur mustard simulant by trisaryl phosphoric triamide-based resin using a quartz crystal microbalance sensor

Chemical warfare agents (CWAs) pose a persistent threat to human safety, and bis(2-chloroethyl) sulfide, or sulfur mustard (SM) is one of the most dangerous substances and is able to cause serious harm. Detecting SM gas is vital, but current methods have high-temperature requirements and limited selectivity, mainly because of the lack of CWA receptor development, and this makes them challenging to use. To address this issue, we present a trisaryl phosphoric triamide-based resin receptor that preferentially interacts with a SM simulant 2-chloroethyl ethyl sulfide (2-CEES) through dipole interactions. The receptor was synthesized through a facile process using an amine and a triethyl phosphate and the properties of its coating were enhanced using epoxy chemistry. The receptor's superior triamide structure was evaluated using a quartz crystal microbalance and reactivity was confirmed by observing the variations in reactivity according to the number of phosphoramides. The receptor showed better reactivity to 2-CEES vapor than to the known poly(epichlorohydrin) and showed selectivity to other volatile organic compounds. Moreover, its durability was evident even 30 days post-coating. The applicability of this receptor extends to array sensors, sound acoustic wave sensors, and chemo-resistive and chemo-capacitive sensors, and it promises advances in chemical warfare agent detection.

Sensitive Materials Used in Surface Acoustic Wave Gas Sensors for Detecting Sulfur-Containing Compounds

There have been many studies on surface acoustic wave (SAW) sensors for detecting sulfur-containing toxic or harmful gases. This paper aims to give an overview of the current state of polymer films used in SAW sensors for detecting deleterious gases. By covering most of the important polymer materials, the structures and types of polymers are summarized, and a variety of devices with different frequencies, such as delay lines and array sensors for detecting mustard gas, hydrogen sulfide, and sulfur dioxide, are introduced. The preparation method of polymer films, the sensitivity of the SAW gas sensor, the limit of detection, the influence of temperature and humidity, and the anti-interference ability are discussed in detail. The advantages and disadvantages of the films are analyzed, and the potential application of polymer films in the future is also forecasted.

Fluoride derivatization-enabled sensitive and simultaneous detection of biomarkers for nitrogen mustard in human plasma and urine via gas chromatography tandem mass spectrometry

Methyl-diethanolamine (CAS: 105-59-9), ethyl-diethanolamine (CAS: 139-87-7), and triethanolamine (CAS: 102-71-6) were identified as the degradation products and bio-markers of nitrogen mustard exposure. Sensitive and convenient detection methods for amino alcohol are of great importance to identify nitrogen mustard exposure in forensic analysis. Herein, analytical methods including gas chromatography-tandem mass spectrometry combined with heptafluorobutyryl derivatization and solid phase extraction were established for retrospective detection of the biomarkers in human plasma and urine samples. The efficiency of the method was improved by optimizing the conditions for sample preparation and the GC-MS/MS method. The optimization included the derivatization temperature, reaction time, reagent dosage and solid phase extraction cartridges, eluent and pH of the loading sample. The results indicated that the SCX cartridge resulted in better enrichment and purification effects, and the best recovery could be obtained with pH = 3-4 for the loading samples and an eluent of 2 mL 10% NH4OH/MeOH. The GC-MS/MS parameters were also optimized for better specificity and sensitivity. The established method was fully validated for each analyte both in plasma and urine matrixes. The linear range of analytes in plasma was 1.0-1000 ng mL-1 with a correlation parameter (R2) of ≥0.994, intra-day/inter-day accuracy of 93.7-117%, and relative standard deviation (RSD) of ≤6.5%. Meanwhile the results in urine were 1.0-1000 ng mL-1 with R2 of ≥0.996, intra-day/inter-day accuracy of 94.3-122%, and RSD of ≤6.6%. The detection limit of the analytes was 1.0 ng mL-1. The method was applied for the detection and identification of trace amino alcohols present in urine samples dispatched by the Organization for the Prohibition of Chemical Weapons (OPCW) and the results were confirmed to be correct.

Fluorescent probes for the detection of chemical warfare agents

Chemical warfare agents (CWAs) are toxic chemicals that have been intentionally developed for targeted and deadly use on humans. Although intended for military targets, the use of CWAs more often than not results in mass civilian casualties. To prevent further atrocities from occurring during conflicts, a global ban was implemented through the chemical weapons convention, with the aim of eliminating the development, stockpiling, and use of CWAs. Unfortunately, because of their relatively low cost, ease of manufacture and effectiveness on mass populations, CWAs still exist in today's world. CWAs have been used in several recent terrorist-related incidents and conflicts (e.g., Syria). Therefore, they continue to remain serious threats to public health and safety and to global peace and stability. Analytical methods that can accurately detect CWAs are essential to global security measures and for forensic analysis. Small molecule fluorescent probes have emerged as attractive chemical tools for CWA detection, due to their simplicity, ease of use, excellent selectivity and high sensitivity, as well as their ability to be translated into handheld devices. This includes the ability to non-invasively image CWA distribution within living systems (in vitro and in vivo) to permit in-depth evaluation of their biological interactions and allow potential identification of therapeutic countermeasures. In this review, we provide an overview of the various reported fluorescent probes that have been designed for the detection of CWAs. The mechanism for CWA detection, change in optical output and application for each fluorescent probe are described in detail. The limitations and challenges of currently developed fluorescent probes are discussed providing insight into the future development of this research area. We hope the information provided in this review will give readers a clear understanding of how to design a fluorescent probe for the detection of a specific CWA. We anticipate that this will advance our security systems and provide new tools for environmental and toxicology monitoring.

Recent advances in fluorescent and colorimetric chemosensors for the detection of chemical warfare agents: a legacy of the 21st century

Chemical warfare agents (CWAs) are among the most prominent threats to the human population, our peace, and social stability. Therefore, their detection and quantification are of utmost importance to ensure the security and protection of mankind. In recent years, significant developments have been made in supramolecular chemistry, analytical chemistry, and molecular sensors, which have improved our capability to detect CWAs. Fluorescent and colorimetric chemosensors are attractive tools that allow the selective, sensitive, cheap, portable, and real-time analysis of the potential presence of CWAs, where suitable combinations of selective recognition and transduction can be integrated. In this review, we provide a detailed discussion on recently reported molecular sensors with a specific focus on the sensing of each class of CWAs such as nerve agents, blister agents, blood agents, and other toxicants. We will also discuss the current technology used by military forces, and these discussions will include the type of instrumentation and established protocols. Finally, we will conclude this review with our outlook on the limitations and challenges in the area and summarize the potential of promising avenues for this field.

Bifunctional Fluorescent Probes for the Detection of Mustard Gas and Phosgene

Mustard gas [sulfur mustard (SM)] and phosgene are the most frequently used chemical warfare agents (CWAs), which pose a serious threat to human health and national security, and their rapid and accurate detection is essential to respond to terrorist attacks and industrial accidents. Herein, we developed a fluorescent probe with o-hydroxythioketone as two sensing sites, AQso, which can detect and distinguish mustard gas and phosgene. The dual-sensing-site probe AQso reacts with mustard gas to form a cyclic product with high sensitivity [limit of detection (LOD) = 70 nM] and is highly selective to SM over phosgene, SM analogues, active alkylhalides, acylhalides, and nerve agent mimics, in ethanol solutions. When encountering phosgene, AQso rapidly converts to cyclic carbonate, which is sensitive (LOD = 14 nM) and highly selective. Their sensing mechanisms of AQso to mustard gas and phosgene were well demonstrated by separation and characterization of the sensing products. Furthermore, a facile test strip with the probe was prepared to distinguish 2-chloroethyl ethyl sulfide (CEES) and phosgene in the gas phase by different fluorescence colors and response rates. Not using the complicated instrument, the qualitative and quantitative detection of CEES or phosgene can be achieved only by measuring the red-green-blue (RGB) channel intensity of the test strip after being exposed to CEES or phosgene gas by the smartphone with an RGB color application.

Advances in Noble-Metal Nanoparticle-Based Fluorescence Detection of Organophosphorus Chemical Warfare Agents

Efficient and simple detection of chemical warfare agents (CWAs) is an essential step in minimizing the potentially lethal consequences of chemical weapons. CWAs are a family of organic chemicals that are used as chemical weapons because of their enormous severity and lethal effects when faced with unforeseen challenges. To stop the spread of CWAs, it is critical to develop a platform that detects them in a sensitive, timely, selective, and minimally invasive manner. Rapid advances in the demand for on-site sensors, metal nanoparticles, and biomarker identification for CWAs have made it possible to use fluorescence as a precise real-time and point-of-care (POCT) testing technique. For POCT-based applications, the new capabilities of micro- and nanomotors offer enormous prospects. In recent decades, significant progress has been made in the design of fluorescent sensors and the further development of noble metal nanoparticles for the detection of organophosphorus CWAs, as described in this review. Through this work, recent attempts to fabricate sensors that can detect organophosphorus CWAs through changes in their fluorescence properties have been summarized. Finally, an integrated outlook on how noble metal nanoparticles could be used to develop smart sensors for organophosphorus CWAs that communicate with and control electronic devices to monitor and improve the health of individuals.

Sensitive and selective detections of mustard gas and its analogues by 4-mercaptocoumarins as fluorescent chemosensors in both solutions and gas phase

Mustard gas has been used as a chemical warfare agent for a century, and is the most likely chemical weapon used in wars or by terrorists. Thus, it is important to develop a facile, rapid and highly selective method for the detection of mustard gas. In this paper, two fluorescent probe molecules, 4-mercaptocoumarins, have been developed for rapid and sensitive detections of SM and its analogues (CEES and NH1) in both solutions and gas phase. The sensing reaction is a nucleophilic addition at three-membered hetercyclic sulfonium/ammonium formed from SM, CEES/NH1 in ethanol. Two fluorescent probes (4-mercaptocoumarins, ArSH) in ethanol deprotonate to form thiophenol anions (ArS^-) resulting from their low pKa values (3.2-3.4), and the nucleophilic addition of the anion ArS^- generates the corresponding thioethers, giving a turn-on fluorescence response. The thiophenol anion can fast sense SM, CEES and NH1 (within 1-4 min) with high sensitivity (~nM level) at 60 °C, and high selectivity through adding a tertiary amine, and two probes exhibit excellent chemical and photostability in detection systems. Furthermore, a facile test strip with the sensor was fabricated for the detection of CEES vapor with rapid response (3 min), high sensitivity (9 ppb) and high selectivity.

Design and development of a prototype for specific naked-eye detection of blister and nerve agents

In view of the strong need to strengthen the national security arising from chemical terrorism, a rapid, specific, and onsite detection of chemical warfare agents (CWAs) employing a simple and easy-to-use kit is of utmost importance. Constant and sincere efforts are being carried out by the scientific community to find reliable techniques/methods for early warning detection. Herein, we designed a prototype technique in the form of a smart and portable chemical weapon detection kit (CWDK) to facilitate rapid and onsite detection. In this portable kit, a range of unique chemical probes were condensed to achieve the specific chromogenic and fluorogenic detection and discrimination of each member of blister and nerve agents. The embodiment of three chemical probes (Fc, SQ, and LH2) was eventually employed in a compact and flexible plastic packaging for detecting the presence of CWAs with the 'naked-eye' in the areas where laboratory services do not normally exist. The CWDK contains dye/reagent vials, sampling assembly, and a UV torch. The convenience and practicality of this technique suggest a great prospect for highly specific sensing of the complete class of CWAs with fast and accurate results in real-time scenarios with a sensitivity much below their lethal dose.

Quinoline-2-thione-based fluorescent probes for selective and sensitive detections of mustard gas and its analogues

Sulfur mustard (SM, also called as mustard gas (HD)) is a persistent and highly toxic gas used as chemical weapon in wars and military conflicts. Moreover, owing to its simple structure and easy synthesis, it is the most likely chemical agent used by terrorists. For this reason, it is vital important to develop a facile, rapid and reliable detection system for SM. In this paper, we have developed four quinoline-2-thiones as fluorescent probes, 2a-2d, for the detection of SM and its analogues, half sulfur mustard (CEES) and a nitrogen mustard NH1. In the presence of KOH, these quinoline-2-thiones deprotonated to quinoline-2-thiophenol anions, which react with SM and its analogues rapidly to form quinoline-2-thiethers with highly efficient fluorescence, giving turn-on fluorescence response. The sensing products with CEES were isolated and fully characterized, thereby, the sensing mechanism was firmly established. The fluorescent probes with 4-trifluoromethyl group, 2b and 2d, exhibit rapid response to SM, CEES and NH1 (within 1 min at 60 °C for CEES and NH1), high sensitivity (limit of detection, 50 nM for SM and 20 nM for NH1) and high selectivity. Furthermore, polymer film test strips were fabricated with probe-embedded poly(ethylene oxide) for the detection of CEES vapor. These test strips displayed a rapid response (<4 min) to gaseous CEES with high sensitivity (0.2 ppm) and high selectivity. These results show that fluorescent probes 2b and 2d have a good application prospect in the field detection of mustard gas.

Chromo-fluorogenic sensors for chemical warfare agents in real-time analysis: journey towards accurate detection and differentiation

The existence of chemical weapons (blister and nerve agents) is an unfortunate reality of the modern world. The usage of these chemical agents by rogue states or terrorist groups has showcased their ugly faces in the past and even in recent years. Despite extensive and strenuous efforts by the Organization for the Prohibition of Chemical Weapons (OPCW) to eliminate chemical warfare agents (CWAs) by the prohibition of their production and the destruction of their stockpiles, many countries still possess them in enormous quantities. Given the potential threat from these lethal agents, it is imperative to have a foolproof chemical sensor and detection system, which should consist of readily deployable chemical probes that can operate with high specificity and sensitivity. Over the last decade, our group has been engaged in designing and developing novel field-deployable sensing techniques by exploring approaches based on supramolecular tools, which can result in excellent specificity, sensitivity, high speed, portability and low cost. In this article, I describe our group's journey and success stories in the development of chemical warfare detection protocols, detailing the range of unique chemical probes and methods explored to achieve the specific detection of individual agents under real environmental conditions. It is interesting to note that the combination of three molecular probes (SQ, Fc and LH2) could simply achieve the detection of all CWAs at room temperature in one go without the need for nonportable and expensive instruments. The ease and generality of these techniques/methods suggest great promise for the highly specific chemical sensing of almost the entire class of CWAs. In this paper, a brief introduction is first provided to present the basic chemistry related to CWAs and the importance of supramolecular chemistry in the design of new protocols with new insights. The manipulation of molecular probes is then debated towards the development of a system for the chromo-fluorogenic sensing of CWAs without interference from most relevant analytes. Finally, the outlook of open challenges and the future developments of this rapidly evolving field is discussed.

A turn-on fluorescent probe based on N-(rhodamine-B)-thiolactam-2-n-butane with ionic liquids for selective and sensitive detection of mustard gas stimulant

Sulfur mustard (SM) is recognized as one of the most lethal warfare agents. It has the potential to seriously affect public health and safety. To employ appropriate medical countermeasures and treat victims as quickly as possible, the development of a rapid and simple SM detection technique is crucial. The aim of the present study was to explore novel detection systems exhibiting excellent selectivity and high sensitivity. An SM probe, namely N-(rhodamine-B)-thiolactam-2-n-butane (SRB-NB), which was based on a thiolactam structure, was effectively designed and synthesized. The rhodamine and thiourea moieties played the roles of the chromogenic and reacting groups, respectively. Subsequently, using ionic liquids (ILs) as the solvents, a turn-on fluorescence detection system was constructed. Notably, it was found that imidazole-based ILs displayed good solubility for an SM simulant, specifically 2-chloroethyl ethyl sulfide (2-CEES). Moreover, 1-butyl-3-methylimidazolium dicyandiamide ([BMIm]DCA) IL held the maximum amount of 2-CEES (132.5 g/100 g). The SRB-NB probe exhibited better ultraviolet (UV) absorption and fluorescence properties in ILs than in other organic solvents. SRB-NB/IL was able to detect 2-CEES in liquid form with remarkable selectivity and sensitivity. The limit of detection (LOD) was established at 3.0 × 10-6 M. Importantly, SRB-NB/ILs also showed good optical response to gaseous 2-CEES and SM.

Luminol-Based Turn-On Fluorescent Sensor for Selective and Sensitive Detection of Sulfur Mustard at Ambient Temperature

We have explored a novel turn-on fluorescence detection of sulfur mustard (SM) at "room temperature". The innovative protocol that uses the combination of luminol and an ionic liquid in water exhibits fluorescence detection of SM within seconds. In this simple, fast, and low-cost chemosensing method, luminol acts as the receptor as well as a signaling element, and the ionic liquid (1-ethyl-3-methylimidazolium dicyanamide) provides the requisite and polarizing medium to realize the detection at "room temperature". Interestingly, with a higher concentration of a probe (0.56 mM), SM sensing can be visualized with the naked eye, leading to the formation of a fluorescent green color within a minute, thus expanding the application of the developed sensing technique for chromo-fluorogenic detection of SM. Excellent selectivity, sensitivity (LOD: 6 ppm), and chemosensing at ambient temperature make this methodology completely field-deployable.

Optical detection of sulfur mustard contaminated surfaces based on a sprayable fluorescent probe

A water-based sprayable functional polymer was immobilized with the fluorescent probe DPXT and was used as a chemo-sensor for rapid localization of surface contamination by sulfur mustard.

A FRET probe for the detection of alkylating agents

A fluorogenic FRET probe allows efficient detection of toxic alkylating agents through a self-immolative reaction.

Highly selective and sensitive chromogenic detection of nerve agents (sarin, tabun and VX): a multianalyte detection approach

A novel strategy using ferrocenyl dye (1) was developed for highly selective chromogenic detection of all nerve agents.

Chromogenic and fluorogenic multianalyte detection with a tuned receptor: refining selectivity for toxic anions and nerve agents

In the present study, a chemical probe was finely tuned for the highly selective and sensitive chromogenic and fluorogenic detection of toxic anions and a nerve agent.