Chapter 5 - High-Performance Ion Mobility Spectrometry

Ion mobility spectrometry: Current status and application for chemical warfare agents detection

On-site detection and initial identification of chemical warfare agents (CWAs) remain difficult despite the many available devices designed for this type of analysis. Devices using well-established analytical techniques such as ion mobility spectrometry, gas chromatography coupled with mass spectrometry, or flame photometry, in addition to unquestionable advantages, also have some limitations (complexity, high unit cost, lack of selectivity). One of the emerging techniques of CWA detection is based on acoustic wave sensors, among which surface acoustic wave (SAW) devices and quartz crystal microbalances (QCM) are of particular importance. These devices allow for the construction of undemanding and affordable gas sensors whose selectivity, sensitivity, and other metrological parameters can be tailored by application of particular coating material. This review article presents the current state of knowledge and achievements in the field of SAW and QCM-based gas sensors used for the detection of blister agents as well as simulants of these substances. The scope of the review covers the detection of blister agents and their simulants only, as in the available literature no similar paper was found, in contrast to the detection of nerve agents. The article includes description of the principles of operation of acoustic wave sensors, a critical review of individual studies and solutions, and discusses development prospects of this analytical technique in the field of blister agent detection.

Photoionization induced chemical ionization time-of-flight mass spectrometry for rapid and sensitive detection of trace gaseous chemical warfare agents.

E-mail: ydkim91@skku.eduReceived March 3, 2013, Accepted April 1, 2013Aim of our study is finding adsorbents suitable for pre-concentration of chemical warfare agents (CWAs). Weconsidered Tenax, bare silica and polydimethylsiloxane (PDMS)-coated silica as adsorbents for dimethylmethylphosphonate (DMMP) and dipropylene glycol methyl ether (DPGME). Tenax showed lower thermalstability, and therefore, desorption of CWA simulants and decomposition of Tenax took place simultaneously.Silica-based adsorbents showed higher thermal stabilities than Tenax. A drawback of silica was that adsorptionof CWA simulant (DMMP) was significantly reduced by pre-treatment of the adsorbents with humid air. In thecase of PDMS-coated silica, influence of humidity for CWA simulant adsorption was less pronounced due tothe hydrophobic nature of PDMS-coating. We propose that PDMS-coated silica can be of potential importanceas adsorbent of CWAs for their pre-concentration, which can facilitate detection of these CWAs.Key Words : Chemical warfare agents (CWAs), Pre-concentration, Polydimethylsiloxane (PDMS)-coating,SilicaIntroductionDetection of ultralow concentration of chemical warfareagents (CWAs) has been attracting attention recently indefense development. CWAs with high vapor pressure canbe easily spread out in the atmosphere, and therefore, detec-tion of low-concentration of CWAs can allow initiation ofprotection process from CWAs as early as possible, ultimate-ly hindering diffusion of CWAs into a wider area.For detection of CWAs, ion mobility spectroscopy, gaschromatography and mass spectrometry can be used.

Stand-off tissue-based biosensors for the detection of chemical warfare agents using photosynthetic fluorescence induction

Ion mobility spectrometry (IMS) is an analytical technique that has primarily been used as a trace chemical monitor in the field. The benefits of IMS as a field detector are its simplicity, sensitivity, fast analysis times, portability, ruggedness, and its operation at ambient pressures. IMS has successfully been used for many years to detect traces of explosives at airports and other security checkpoints; illicit drugs in prisons, cargo, and in border security. The military have long used IMS for detection of chemical warfare agents. Innovations in drift tubes, nonradioactive ion sources, and hyphenated IMS techniques in recent years have expanded the range of forensic applications. A sample introduced into the IMS undergoes atmospheric pressure chemical ionization and the resulting product ions are separated by their mobilities in the drift tube. Several factors such as temperature, humidity, concentration and presence of interferences can affect the ionization and separation process. This article describes the principles of IMS, developments in technology, and their implications for forensic science. IMS trends in detection of explosives, illicit drugs, and chemical warfare agents are discussed. The article also provides an overview of some unconventional applications and some interesting emerging forensic applications of IMS.

In situ construction of hierarchical Fe2O3 nanotube arrays for real-time detection and degradation of 2-CEES gas

The use of Ion Mobility Spectrometry (IMS) in the Detection of Contraband Sandia researchers use ion mobility spectrometers for trace chemical detection and analysis in a variety of projects and applications. Products developed in recent years based on IMS-technology include explosives detection personnel portals, the Material Area Access (MAA) checkpoint of the future, an explosives detection vehicle portal, hand-held detection systems such as the Hound and Hound II (all 6400), micro-IMS sensors (1700), ordnance detection (2500), and Fourier Transform IMS technology (8700). The emphasis to date has been on explosives detection, but the detection of chemical agents has also been pursued (8100 and 6400). Combining Ion Mobility Spectrometry (IMS) with Mass Spectrometry (MS) is described. The IMS-MS combination overcomes several limitations present in simple IMS systems. Ion mobility alone is insufficient to identify an unknown chemical agent. Collision cross section, upon which mobility is based, is not sufficiently unique or predictable a priori to be able to make a confident peak assignment unless the compounds present are already identified. Molecular mass, on the other hand, is much more readily interpreted and related to compounds. For a given compound, the molecular mass can be determined using a pocket calculator (or in one's head) while a reasonable value of the cross-section might require hours of computation time. Thus a mass spectrum provides chemical specificity and identity not accessible in the mobility spectrum alone. In addition, several advanced mass spectrometric methods, such as tandem MS, have been extensively developed for the purpose of molecular identification. With an appropriate mass spectrometer connected to an ion mobility spectrometer, these advanced identification methods become available, providing greater characterization capability.

An ion mobility quadrupole time-of-flight mass spectrometry-based pesticide suspect screening methodology was developed and validated covering 20 plant-derived food matrices deriving from six commodity groups of different complexity according to the actual European Commission document SANTE/11813/2017 applying a QuEChERS sample preparation protocol. The method combines ultra-performance liquid chromatography, traveling wave ion mobility, and quadrupole time-of-flight mass spectrometry. Besides the determination of the physicochemical property collision cross-section and the establishment of a corresponding scientific suspect screening database comprising 280 pesticides for several pesticides, different protomers, sodium adducts, as well as dimers were identified in ion mobility spectrometry traces. Additionally, collision cross-section values were included in the validation requirements regarding chromatography and mass spectrometry for the detection of pesticides. A collision cross-section value window was analyzed within a tolerable error of ±2%. For this cross-matrix validation, screening detection limits were determined at concentration levels of 0.100mg/kg (84% of the original pesticide scope), 0.010mg/kg (56%), and 0.001mg/kg (21%). By application of ion mobility spectrometry, the compound identification was improved due to independence of commodity of concern and concentration levels of analyte molecules, as false assignments are reduced by application of a collision cross-section range.

Ultrasensitive detection of explosives and chemical warfare agents by low-pressure photoionization mass spectrometry

State of ion mobility spectrometry and applications in agriculture: A review

A rapid and simple sampling technique for use in conjunction with commercial ion mobility spectrometric detectors is described. The technique may be used for the detection of chemical warfare agents in the field. A plastic syringe with a steel needle was attached to the nozzle of the detector, and the syringe shortened to reduce the dead volume in the interface. After heating samples of protective clothing in closed headspace vials to 70 °C for three minutes, the detector with the syringe and needle (called HS-LCD) was used to penetrate the vial and the overpressure was transferred to the detector via the simple interface. The detector response was registered in realtime. To demonstrate the possibilities with this technique, the HS-LCD sampler was tested in the field at relatively low temperatures on pieces of protective clothing contaminated by the chemical warfare agent simulants methyl salicylate and dipropylene glycol methyl ether. A significant improvement in detector response was observed utilising this technique compared to using the detector to survey the material in the open air. This improvement is believed to increase with decreasing ambient temperature and with decreasing analyte volatility. A more comprehensive list of possible interferents should be tested in the future.

The development of mass spectrometric and ion mobility devices heavily depends on a comprehensive understanding of the behavior of ions within such systems. Therefore, numerical modeling of ion paths helps to optimize and verify existing devices, and contributes to the development of innovative ion optical systems and multipole geometries. This Article introduces IDSimF (Ion Dynamics Simulation Framework), an open-source simulation tool tailored to the nonrelativistic dynamics of molecular ions in mass and ion mobility spectrometry applications. Addressing limitations in existing software packages, as for example SIMION, OpenFOAM, and COMSOL, IDSimF offers a specialized platform for simulating ion trajectories in electric fields. IDSimF efficiently accounts for space charge effects and considers various ion-neutral collision models while handling chemical kinetics. The framework is highly modular with reduced user input configuration complexity and aims to support simulation efforts in development and optimization of in mass spectrometers.

The Joint Chemical Agent Detector (JCAD) will provide state of the art chemical warfare agent detection capability to ground vehicle operators. Intelligence sources estimate that over twenty counties have active chemical weapons programs. The spread of chemical weapons to third world nations, coupled with the potential for US involvement in these areas in an operational or support capacity, increases the probability that the Joint Services may encounter chemical agents and toxic industrial materials anywhere in the world. Currently, fielded chemical agent detectors are bulky, labor intensive, and subject to false readings. No legacy detector is sensitive enough to provide detection and warning of the low dose hazards associated with miosis contamination. The JCAD will provide a small, lightweight chemical agent detector for vehicle interiors, aircraft, individual personnel, shipboard, and fixed site locations. The system provides a common detection components across multi-service platforms. This common detector system will allow the Joint Services to use the same operational and support concept for more efficient utilization of resources. The JCAD will detect, identify, quantify, and warn of the presence of chemical agents prior to onset of miosis. Upon detection of chemical agents, the detector will provide local and remote audible and visual alarms to the operators. Advance warning will provide the vehicle crew with the time necessary to protect themselves from the lethal effects of chemical agents. The JCAD will also be capable of being upgraded to protect against future chemical agent threats. The JCAD will provide the vehicle operators with the warning necessary to survive and fight in a chemical warfare agent threat environment.

Mass spectrometry (MS) as an analytical technique enables the identification and quantitative determination of proteins, metabolites, or lipids in a studied sample. However, this method has limitations regarding the number of molecules that can be identified at a given time. To increase the number of identifications, the application of ion mobility spectrometry (IMS) can be employed. This technique allows the separation of ions based on their mobility while traversing the analyser in a gradient of an electromagnetic field and opposing gas pressure. The separation is performed in conjunction with MS analysis, adding another dimension to the analysis, resulting in a significant improvement in the number of identified compounds and a reduction in noise. Alternatively, while maintaining the same number of identifications, analysis can be performed in a shorter time period. It is crucial to pay special attention to the type of IMS analyser used, as its specific implementation dictates further stages of analysis and ion detection capabilities.