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Hazardous chemical leakages involved in chemical terrorist attacks and chemical industrial accidents have been posing severe threats to human health and the environment. Vehicle-mounted mass spectrometry (MS) has been developed for continuous, on-road measurements to map the spatial and temporal distributions of hazardous chemicals. However, the detection of chemicals with small temporal scales and spatial scales is always challenging. In this study, a parallel coupling apparatus combining the techniques of ion mobility spectrometry and ion trap MS ( p -IMS-ITMS) was developed to improve the detection rate and the time response capability of a stand-alone ITMS system for short time-span chemical tracking. A workflow was also proposed along with the apparatus, where the ITMS system can be triggered, as chemical suspects were discovered with the IMS system. The sampling positions of the ITMS system were investigated and optimized. In addition, a strategy was proposed to diminish the time span of samples from 1.5 to 0.5 s for evaluating the performances of the p -IMS-ITMS system. The detection rate of the stand-alone ITMS system was measured to be only 9.5, 32, and 87.5% for the time span of 0.5, 1, and 1.5 s, respectively. By comparison, the detection rates of the p -IMS-ITMS system were 99.5, 100, and 100%, where the detection rate was increased by a factor of 10 for 0.5 s time span. Moreover, the addition of an IMS system could provide temporal patterns of hazardous chemicals with a resolution of 33 ms. Finally, the potential of the p -IMS-ITMS system for environmental navigation monitoring and assessment was further demonstrated by detecting the leakages of dimethyl methyl phosphonate and dipropylene glycol monomethyl ether.

Online measuring end-tidal propofol concentration during balanced anesthesia is important for anesthetists to learn the patient's anesthesia depth as exhaled propofol concentration is well related to blood propofol concentration. In previous work, exhaled propofol was detected using acetone assisted negative photoionization ion mobility spectrometer, however, the existence of high concentration sevoflurane interfered the response of propofol. In this work, an anisole assisted photoionization ion mobility spectrometer operated in positive mode was developed to sensitively and selectively measure the end-tidal propofol by eliminating the interferences of exhaled humidity and sevoflurane during balanced anesthesia. Anisole molecular ion is stable enough not to go under proton transfer reaction with water presents in the exhaled breath. Hence, the exhaled humidity related peaks were eliminated and only one propofol product ion peak (K 0  = 1.50 cm 2  V -1  s -1 ) was observed. The relative standard deviation (RSD) ranging from 0.64%-0.91% showed good repeatability and the quantitative range was 0.2-40 ppbv with a response time of 4 s. Finally, the performance of the proposed method was demonstrated by monitoring end-tidal propofol of balanced anesthetized patients during gastric cancer surgery., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The concentration of propofol in blood is an important indicator for anesthesiologists to monitor and regulate the anesthesia depth of patients during surgery. Herein, a negative photoionization ion mobility spectrometry with acetone as the dopant was developed for rapid and direct determination of intraoperative blood propofol concentration in the operating theatre. High concentration of acetone molecules in the carrier gas was used not only to enhance neutral desorption and release free propofol molecules from the whole blood, but also to increase the intensity of reactant O 2 - and reduce the amount of non-reactive CO 3 - ions simultaneously, which allowed to measure trace propofol in less than 2 min without any tedious pretreatment. Under optimized conditions, a linear calibration curve of propofol was obtained with the range of 0.5-20 ng μL -1 and with a limit of detection of 0.14 ng μL -1 , which met the clinical requirements and correlated well with standard HPLC methods. Finally, the method was applied to detect intraoperative blood propofol concentration in nearly 100 surgical patients, demonstrating its excellent detection capability and facilitating the study of propofol pharmacokinetics., (Copyright © 2019 Elsevier B.V. All rights reserved.)

UV photoionization (UV-PI) is a promising non-radioactive ionization method for ion mobility spectrometry (IMS). It could work at either direct photoionization mode or chemical ionization mode by adding photoionizable dopants, and thus its applications extend to a wide range of compound classes. This work is to present a comprehensive review on the development of UV-PI-IMS. It focuses on UV-PI's capabilities and how to use them fully. A summary discussion of the ionization processes in UV-PI would be presented first for understanding the fundamentals of UV-PI-IMS. Followed by descriptions of the technical configurations of UV-PI source in IMS. Improvements in the design of UV-PI source for achieving optimum results will be presented with references to examples. Further, a broad range of applications, including environmental contaminants analysis, trace explosives and chemical warfare agents detection, food safety and quality analysis, and clinical diagnosis, would be presented to demonstrated the analytical performance of UV-PI-IMS. In the conclusion, perspectives on areas of UV-PI technique which have the potential to be improved would be reasonably presented., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Online monitoring of end-tidal propofol provides important information of anesthesia deepness for anesthetists as propofol concentrations in plasma and breath are well correlated. In this work, a dopant-assisted photoionization positive ion mobility spectrometry (DAPI-PIMS) coupled with time-resolved purge introduction was developed for online quantitative monitoring end-tidal propofol. With optimized dopant, toluene, the selectivity and sensitivity of propofol was improved as interference from sevoflurane was eliminated. Using the time-resolved purge introduction, the response of propofol and moisture was separated due to their absorption differences on the inwall of the fluorinated ethylene propylene (FEP) sample loop, ensuring sensitive measurement of end-tidal propofol with a short response time of 4 s. The quantitative equation derived from the second order reaction kinetics model extended the quantitative range of propofol from 0.2 ppbv to 45 ppbv. Finally, the method was used to monitor the intraoperative end-tidal propofol of six patients, and the results nicely demonstrated its feasibility in practical clinical environment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ion mobility spectrometry (IMS) opened a potential avenue for the rapid detection of organophosphorus pesticides (OPPs), though an improved selectivity of stand-alone IMS was still in high demand. In this study, a stand-alone positive photoionization ion mobility spectrometry (PP-IMS) apparatus was constructed for the rapid detection of OPPs with acetone as dopant. The photoionization of acetone molecules was induced by the ultraviolet irradiation to produce the reactant ions (Ac) 2 H + , which were employed to ionize the OPPs including fenthion, imidan, phosphamidon, dursban, dimethoate and isocarbophos via the proton transfer reaction. Due to the difference in proton affinity, the tested OPPs exhibited the different dopant-dependent manners. Based on this observation, the switching of dopant concentration was implemented to improve the selectivity of PP-IMS for OPPs detection. For instance, a mixture of fenthion, dursban and dimethoate was tested. By switching the concentration of doped acetone from 0.07 to 2.33 to 19.94mgL -1 , the ion peaks of fenthion and dursban were inhibited in succession, achieving the selective detection of dimethoate at last. In addition, another mixture of imidan and phosphamidon was initially detected by PP-IMS with a dose of 0.07mgL -1 acetone, indicating that their ion peaks were severely overlapped; when the concentration of doped acetone was switched to 19.94mgL -1 , the inhibition of imidan signals promised the accurate identification of phosphamidon in mixture. Finally, the PP-IMS in combination of switching dopant concentration was applied to detect the mixed fenthion, dursban and dimethoate in Chinese cabbage, demonstrating the applicability of proposed method to real samples., (Copyright © 2017. Published by Elsevier B.V.)

Biogenic amines are degradation products generated through enzymatic and microbial processes during food spoilage, which may pose a health hazard to consumers at elevated levels. Trimethylamine (TMA) is a good target for the detection of biogenic amines due to its volatility and fishy odor. In this study, we developed a stand-alone dopant-assisted positive photoionization ion mobility spectrometry (DAPP-IMS) for rapid and sensitive detection of TMA. Response of TMA was enhanced by the addition of dopants and characteristic product ions with reduced mobility 2.26cm 2 V -1 s -1 were formed. 2-Butaone was chosen as the dopant for better separation between reagent ion peak and TMA product ion peak as well as higher sensitivity and the limit of detections (LODs) for TMA standard sample was 1ppb. The potential application of DAAP-IMS was evaluated by the detection of TMA generated by oyster and shrimp during 4°C storage. Analysis of two kinds of seafood showed the same characteristic peak to TMA standard sample, and the intensity of TMA increased over the storage time. The results of this study testify to the potential of DAPP-IMS for qualitative and quantitative determination of TMA in real food samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The plasma propofol concentration is important information for anaesthetists to monitor and adjust the anaesthesia depth for patients during a surgery operation. In this paper, a stand-alone ion mobility spectrometer (IMS) was constructed for the rapid measurement of the plasma propofol concentrations. Without any sample pre-treatment, the plasma samples were dropped on a piece of glass microfiber paper and then introduced into the IMS cell by the thermal desorption directly. Each individual measurement could be accomplished within 1 min. For the plasma propofol concentrations from 1 to 12 μg mL -1 , the IMS response was linear with a correlation coefficient R 2 of 0.998, while the limit of detection was evaluated to be 0.1 μg mL -1 . These measurement results did meet the clinical application requirements. Furthermore, other clinically-often-used drugs, including remifentanil, flurbiprofen and atracurium, were found no significant interference with the qualitative and quantitative analysis of the plasma propofol. The plasma propofol concentrations measured by IMS were correlated well with those measured by the high performance liquid chromatography (HPLC). The results confirmed an excellent agreement between these two methods. Finally, this method was applied to monitor the plasma propofol concentrations for a patient undergoing surgery, demonstrating its capability of anaesthesia monitoring in real clinical environments.

Ion mobility spectrometry (IMS) was explored in the selective detection of nitrobenzene compounds in industrial waste water and surface water, and the selectivity was theoretically elucidated with the transformation energy in the product ion formation reaction. A linear detection range of 0.5–50 ppm and a limit of detection (LOD) of 0.1 ppm were found for 2,4,6-trinitrotoluene (TNT). With the IMS as the detection system of molecularly imprinted polymer (MIP) separation technique, the MIP-IMS system was proved to be excellent method to detect trace amount of nitrobenzene compounds in surface water, in which more than 87% of nitrobenzene compounds could be adsorbed on MIPs with 90–105% of recovery. [ABSTRACT FROM AUTHOR]

The online monitoring of hydrogen sulfide (H 2 S) presents a critical advancement for environmental protection and public health, yet existing methodologies struggle to achieve on-site, on-line and highly sensitive detection in atmospheric conditions. This study introduces a novel approach employing ozone-enhanced photoionization ion mobility spectrometry (IMS) in conjunction with a time-resolved dynamic diluter (TRDD) for the efficacious identification of H 2 S within environments of high humidity, such as sewers. This method ingeniously addresses the challenge of distinguishing H 2 S in the presence of water vapor through a dual strategy of ozone oxidization pretreatment and TRDD injection. The strategic placement of ozone within the drift region significantly amplifies the sensitivity of the IMS detection, showcasing the method's superior sensitivity, stability, and humidity interference resilience. Notably, this technique achieves a detection limit for H 2 S at an impressive 2.5 parts per billion (ppb), maintaining a consistent relative standard deviation (RSD) of 2.5 % over three consecutive days. Furthermore, the approach effectively mitigates the effects of moisture, maintaining an RSD of 3.0 % despite a relative humidity (RH) increase from 22 % to 95 %. Applied to the on-site measurement of H 2 S in sewer systems, the method demonstrated all the aforementioned performance characteristics, marking it a promising way of high humidity environment H 2 S monitoring. [Display omitted] • H 2 S was sensitively detected with ozone-enhanced ion mobility spectrometry. • The limit of detection of 2.5 ppb for H 2 S was achieved. • Moisture effect was avoided using time-resolved dynamic dilution inlet method. • Stability with relative standard deviation as low as 0.59 % was achieved. [ABSTRACT FROM AUTHOR]

Linear drift tube ion mobility spectrometry (DTIMS) is widely used in standalone and hyphenated IMS instruments for detecting trace chemical compounds. As a temporal dispersion technique, DTIMS requires an ion injection process for generating discrete ion packets to start the ion mobility separation and detection steps. The ion injection process is carried out mainly via ion gating with ion gates of different mechanism and that defines largely the resolving power and the sensitivity of IMS analysis. This work is to present a systematic interpretation on the principles, limitations, and advances of ion gating in IMS. It mainly focuses on understanding the movement behaviors of ions around the ion gates along with the gating field changing actions and how to use such information fully to enhance the analytical performance of IMS. A summary description of the working principles and various configurations of ion gates will be presented first to comprehend the fundamentals of ion gating in IMS, followed by a discussion of the ion mobility discrimination arising from the non-idealities of ion gate as well as its effect on the ion packet injection process. Then, the dynamics of ion swarm in temporal and spatial varying electric fields would be explained mathematically and graphically to understand how ion gating under such conditions might affect the resolving power and the sensitivity of IMS. Further, advanced ion gating modes developed in the past decade for improving the analytical performance of IMS would be categorized and discussed along with analytical results. In the conclusion, perspectives on the current status and future development of ion gating in IMS would be provided. • Working principles and various configurations of ion gates are summarily presented. • Ion gate non-idealities and their effect on the ion injection process are discussed. • Dynamics of ion swarm in temporal and spatial varying electric fields are explained. • Advanced ion gating modes for improving the IMS analysis performance are discussed. • Perspectives on the current and future development of ion gating in IMS are given. [ABSTRACT FROM AUTHOR]

Peroxide-based explosives (PBEs) are increasingly common in criminal and terrorist activity due to their easy synthesis and high explosive power. The rise in terrorist attacks involving PBEs has heightened the importance of detecting trace amounts of explosive residue or vapors. This paper aims to provide a review on the developments of techniques and instruments for detecting PBEs over the past ten years, specifically discussing advancements in ion mobility spectrometry, ambient mass spectrometry, fluorescence techniques, colorimetric methods, and electrochemical methods. We provide examples to illustrate their evolution and focus on new strategies for improving detection performance, specifically in terms of sensitivity, selectivity, high-throughput, and wide explosives coverage. Finally, we discuss future prospects for PBE detection. It is hoped this treatment will serve as a guide to the novitiate and as aid memoire to the researchers. [Display omitted] • Ion mobility spectrometry has been extensively deployed at screening points. • Mass spectrometry is considered the next-generation deployable system for field analysis of target explosives. • Fluorescent techniques show their potentials for the detection of explosives. • Colorimetric sensors also show the potential for the detection of explosives. • Electrochemical sensors also show the potential for the detection of explosives. [ABSTRACT FROM AUTHOR]

• Mathematical elucidation of the movement behaviors of ions in electrostatic fields. • Validation of the ion enrichment and ion dilution effects of electrostatic fields. • Development of an ion enrichment method for enhancing the sensitivity of IMS. The diversified applications of ion mobility spectrometry (IMS) frequently pose challenges to the sensitivity of IMS measurements. In this work, the ion density evolution profiles of a continuous flow of ions travelling in non-uniform electrostatic fields were studied. Based on that, an ion enrichment method was proposed for enhancing the sensitivity of IMS. It employed a gradually weakening electrostatic field in the ionization region of IMS and achieved ion density enhancement for the ion flow migrating from the ion source to the ion shutter. Using that method, the ion density of the ion flow produced by the ion source was increased by 180% when approaching the ion shutter. With the increased ion density, the limit of detection (LOD) for DMMP dimer peak was lowered from 425 to 200 pptv. Meanwhile, there was a slight reduction in the resolving power, which was tentatively assigned to the enhanced coulomb repulsion along with the increased ion density. The resolving power of the IMS with a drift length of 60 mm was still maintained around 80 at 100 degrees Celsius. The ion enrichment method needs no radial-confining radio frequency voltage. Also, it does not affect the response speed of IMS. [ABSTRACT FROM AUTHOR]

A real-time dynamic measurements of ammonia (NH 3 ) is crucial for understanding the atmospheric nucleation process. A novel method was developed for on line monitoring at the sub-second time scale for the gaseous ammonia in ambient air for months, based on a positive inhaling ion mobility spectrometry (IMS) with a 63 Ni ion source. The selective detection of NH 3 was achieved using a high resolution IMS with an optimization of the drift tube temperature above 150 °C. This method improved the peak-to-peak resolution significantly, thus avoided the interferences of the adjacent peaks to the quantitative analysis of NH 3 . The time resolution of the IMS was less than 0.1 s at a data averaging of 10 times. The limit of detection (LOD) achieved at sub-ppb level while a linear response of peak intensity versus concentration of NH 3 in the range of 10–60 ppb and 60–400 ppb were obtained. The relative standard deviations (RSD), the confidence level and the errors were 1.06%, 95% and ± 0.21 ppb by measuring 100 ppb NH 3 for 100 times. The effect of ambient humidity could be greatly reduced by using the drift temperature of over 150 °C. At last, the application of measuring the NH 3 concentration evolutions of Dalian city was performed from June 19 to December 3 in 2015. The results illustrated a potential method of using IMS for a real-time measuring atmospheric NH 3 at an unprecedented accuracy and sensitivity with long-term stability. [ABSTRACT FROM AUTHOR]

Malodorous hydrogen sulfide (H 2 S) gas often exists in the sewer system and associates with the problems of releasing the dangerous odor to the atmosphere and causing sewer pipe to be corroded. A simple method is in demand for real-time measuring H 2 S level in the sewer gas. In this paper, an innovated method based on dopant-assisted negative photoionization ion mobility spectrometry (DANP-IMS) with on-line semiconductor cooling inlet was put forward and successfully applied for the real-time measurement of H 2 S in sewer gas. The influence of moisture was effectively reduced via an on-line cooling method and a non-equilibrium dilution with drift gas. The limits of quantitation for the H 2 S in ≥60% relative humidity air could be obtained at ≤79.0 ng L −1 with linear ranges of 129–2064 ng L −1 . The H 2 S concentration in a sewer manhole was successfully determined while its product ions were identified by an ion-mobility time-of-fight mass spectrometry. Finally, the correlation between sewer H 2 S concentration and the daily routines and habits of residents was investigated through hourly or real-time monitoring the variation of sewer H 2 S in manholes, indicating the power of this DANP-IMS method in assessing the H 2 S concentration in sewer system. [ABSTRACT FROM AUTHOR]

Abstract: A computational fluid dynamics-Monte Carlo approach (abbreviated as CMC) based on SIMION has been developed for simulating the ions trajectories in both the fluid and electric fields simultaneously, the gas flow effect and collision of the ions with the gas molecules are considered within this approach. Four kinds of physical parameters of the instruments can be obtained by this model: the flow field, the electric field, the ion trajectories and the mobility spectrum. A drift tube ion mobility spectrometer was built and simulated to verify this model. The distribution of gas flow field (velocity, pressure, temperature) was simulated by a 2D geometry. The ions trajectories and ion mobility spectra of the IMS were then calculated. The good agreements between simulation and experiment show that the CMC model has predictive power for modeling ion motion at ambient pressure, and this model can serve as visual aids for intuitively understanding the factors that determine ion transport. [Copyright &y& Elsevier]

• DAPI-IMS with 2-butanone as dopant were proposed for atmospheric NH 3 measurement. • The method was proved to be specific to trace NH 3 in complex environments. • The method showed a linear range of 20–800 ppb v and a sensitivity of 0.2 fC/ppb v. • NH 3 in toilet was monitored on-site to demonstrate the potential of the DAPI-IMS. Ammonia (NH 3) is a critical hazard gas in both outdoor and indoor environments, which tends to cause problems on the environment and public health. This work is to propose a dopant assisted ion mobility spectrometry (DAPI-IMS) for on-site specific and sensitive determination of the atmospheric NH 3. Using 2-butanone as dopant, preliminary reactant ions (C 4 H 8 O) 2 H+ other than (H 2 O) n H+ were generated in the DAPI source. That provided a molecular substitution reaction channel for efficient ionization of NH 3 and ensured better resolution of NH 3 peak. Further, by introducing the NH 3 sample gas along with dopant into the IMS drift tube of unidirectional gas flow mode, the DAPI-IMS was enabled to specifically and sensitively detect the NH 3 in a background of high humidity and complex matrix. The DAPI-IMS exhibited a linear response range of 20–800 ppb v to NH 3 with a sensitivity of 0.20 fC/ppb v and a limit of detection as low as 4.0 ppb v. The potential of the DAPI-IMS for direct atmospheric NH 3 measurement was also demonstrated via on-site monitoring the day to day emission profiles of NH 3 in toilet. [ABSTRACT FROM AUTHOR]