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As ion mobility spectrometry (IMS) is used with mass spectrometry in more applications, increased emphasis is placed on the ion-neutral collisional cross sections (CCS) to identify unknown analytes in complex matrices. While CCS values can provide useful information about relative analyte size, several critical assumptions are inherent in the most common method of calculating CCS values, the Mason-Schamp equation. The largest source of error in the Mason-Schamp equation originates from not accounting for higher reduced electric field strengths, which are present in low-pressure instruments that require calibration. Previous corrections based on field strength have been proposed in literature, but their data used atomic ions in atomic gases, whereas most applications examine molecules measured in nitrogen. Here, we use a series of halogenated anilines measured in air and nitrogen between 6–120 Td on a first principles ion mobility instrument (HiKE-IMS). With this series of measurements, the average velocity of the ion packet is known allowing for direct calculation of reduced mobilities (K0), alpha functions, and finally, a detailed examination of CCS as a function of E/N. In the worst-case scenario, there is over a 55% difference in CCS values for molecular ions measured at high fields depending on the method used. When comparing CCS values to those in a database for unknown identification, this difference can lead to misidentification. To immediately alleviate some of the error in calibration procedures, we propose an alternative method using K0 and alpha functions that simulate first principles mobilities at higher fields. [ABSTRACT FROM AUTHOR]

Here, we present proof of principle studies to demonstrate how the product ions associated with the ion mobility peaks obtained from a High Kinetic Energy-Ion Mobility Spectrometer (HiKE-IMS) measurement of a volatile can be identified using a Proton Transfer Reaction/Selective Reagent Ion-Time-of-Flight-Mass Spectrometer (PTR/SRI-ToF-MS) when operating both instruments at the same reduced electric field value and similar humidities. This identification of product ions improves our understanding of the ion chemistry occurring in the ion source region of a HiKE-IMS. The combination of the two analytical techniques is needed, because in the HiKE-IMS three reagent ions (NO+, H3O+ and O2+•) are present at the same time in high concentrations in the reaction region of the instrument for reduced electric fields of 100 Td and above. This means that even with a mass spectrometer coupled to the HiKE-IMS, the assignment of the product ions to a given reagent ion to a high level of confidence can be challenging. In this paper, we demonstrate an alternative approach using PTR/SRI-ToF-MS that allows separate investigations of the reactions of the reagent ions NO+, H3O+ and O2+•. In this study, we apply this approach to four nitrile containing organic compounds, namely acetonitrile, 2-furonitrile, benzonitrile and acrylonitrile. Both the HiKE-IMS and the PTR/SRI-ToF-MS instruments were operated at a commonly used reduced electric field strength of 120 Td and with gas flows at the same humidities. [ABSTRACT FROM AUTHOR]

The first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometry (HiKE-IMS-MS) studies involving six volatiles (acetone, acetonitrile, methanol, ethanol, 2-propanol, and 1-butanol) and their fully deuterated analogues are reported. The goal is to further our understanding of the ion–molecule chemistry occurring in the HiKE-IMS. This is needed for its full analytical potential to be reached. Product ions are identified as a function of the reduced electric field (30–115 Td) and the influence of sample air humidity in the reaction region on deuterium/hydrogen (D/H) exchange reactions is discussed. Reagent ions include H3O+(H2O)m (n = 0, 1, 2 or 3), NO+(H2O)n (m = 0 or 1) and O2+·. Reactions with H3O+(H2O)m lead to protonated monomers (through either proton transfer or ligand switching). Reactions with NO+ involve association with acetone and acetonitrile, hydride anion abstraction from ethanol, 2-propanol, and 1-butanol, and hydroxide abstraction from 2-propanol and 1-butanol. With the exception of acetonitrile, O2+· predominantly reacts with the volatiles via dissociative charge transfer. A number of sequential secondary ion-volatile processes occur leading to the formation of dimer and trimer-containing ion species, whose intensities depend on a volatile's concentration and the reduced electric field in the reaction region. Deuterium/hydrogen (D/H) exchange does not occur for product ions from acetone-d6 and acetonitrile-d3, owing to their inert methyl functional groups. For the deuterated alcohols, rapid D/H-exchange reaction at the hydroxy group is observed, the amount of which increased with the increasing humidity of the sample air and/or lowering of the reduced electric field. [ABSTRACT FROM AUTHOR]

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Ion mobility spectrometers can detect gaseous compounds at atmospheric pressure in the range of parts per trillion within a second. Due to their fast response times, high sensitivity, and limited instrumental effort, they are used in a variety of applications, especially as mobile or hand-held devices. However, most real-life samples are gas mixtures, which can pose a challenge for IMS with atmospheric pressure chemical ionization mainly due to competing gas-phase ionization processes. Therefore, we present a miniaturized drift tube IMS coupled to a compact gas chromatograph for pre-separation, built of seven bundled standard GC columns (Rtx-Volatiles, Restek GmbH) with 250 μm ID and 1.07 m in length. Such pre-separation significantly reduces chemical cross sensitivities caused by competing gas-phase ionization processes and adds orthogonality. Our miniaturized GC-IMS system is characterized with alcohols, halocarbons, and ketones as model substances, reaching detection limits down to 70 pptv with IMS averaging times of just 125 ms. It separates test mixtures of ketones and halocarbons within 180 s and 50 s, respectively. The IMS has a short drift length of 40.6 mm and reaches a high resolving power of RP = 68. [ABSTRACT FROM AUTHOR]

With recent advances in ionization sources and instrumentation, ion mobility spectrometers (IMS) have transformed from a detector for chemical warfare agents and explosives to a widely used tool in analytical and bioanalytical applications. This increasing measurement task complexity requires higher and higher analytical performance and especially ultra-high resolution. In this review, we will discuss the currently used ion mobility spectrometers able to reach such ultra-high resolution, defined here as a resolving power greater than 200. These instruments are drift tube IMS, traveling wave IMS, trapped IMS, and field asymmetric or differential IMS. The basic operating principles and the resulting effects of experimental parameters on resolving power are explained and compared between the different instruments. This allows understanding the current limitations of resolving power and how ion mobility spectrometers may progress in the future. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry (IMS) is a well-known technique for fast trace gases detection. Employing atmospheric pressure chemical ionization in IMS, ion clusters, e.g. protonated monomer or proton bound dimer analyte ions such as MH + (H 2 O) n or M 2 H + (H 2 O) n form in the positive mode, where the chemical ionization is based on positively charged reactant ions H + (H 2 O) n . In the negative mode, where the ionization is based on negatively charged reactant ions O 2 - (H 2 O) n , similar cluster formation is possible but less common. In this paper, we investigate 2-chlorophenol, formic acid and toluene-diisocyanate as single substances and in mixtures, showing their different behavior regarding the formation of symmetric and asymmetric clusters and thus the presence and absence of additional peaks in the ion mobility spectra. Quantum-chemical calculations regarding the stabilization energy can explain the absence of certain cluster signals quite well when based on the assumption of ionization by electron capture in contrast to the typically expected ionization by proton abstraction. [ABSTRACT FROM AUTHOR]

Highlights: [•] Detection of low concentration of benzene in ion mobility spectrometry with non-radioactive and non-optical source. [•] Improved investigation of simultaneous detection of benzene and toluene possible with this source. [•] Less signal reduction when adding toluene to benzene achieved. [•] Important example for ionization control in IMS with pulsed electron sources via electron beam intensity and duration. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry is a well-known technique used to analyze trace gases in ambient air. Typically, it works by employing a radioactive source to provide electrons with high energy to ionize the analytes in a series of chemical reactions. During the past ten years non-radioactive sources have been one of the subjects of interest in ion mobility spectrometry, initially in order to replace radioactive sources as a result of general security and regulatory concerns. Among these non-radioactive sources especially pulsed sources have recently been shown to additionally improve the analytic information provided by ion mobility spectrometers. In this review we will describe the progress regarding the application of pulsed non-radioactive electron sources in ion mobility spectrometry and show the recent analytical advances that have been achieved by using pulsed electron beams. [ABSTRACT FROM AUTHOR]

Abstract: Ion mobility spectrometry (IMS) is a well-known technique applied to detect hazardous substances in ambient air. Consequently, it has been used for many years for the detection of chemical warfare agents, toxic substances or illegal drugs. The main advantages are the small size of IMS instruments and the very high sensitivity in the range of a few parts per billion. However, one major disadvantage is the fairly difficult interpretation of spectra especially when mixtures of substances are involved. Spectra recorded with a pulsed IMS, in which delay times can be inserted between ion formation and ion detection, can simplify this task due to the distinct behavior that monomer and dimer peaks exhibit with varying delay times. The discrimination between monomer and dimer signals would normally require further experimental efforts (e.g. a mass spectrometer) with disadvantages regarding the portability of the device. This paper describes how a pulsed electron gun used in a standard IMS device allows for this discrimination without compromising any of the benefits IMS devices offer. [Copyright &y& Elsevier]

Ion mobility spectrometry (IMS) is a well-known method for detecting hazardous compounds in air. Typical applications are the detection of chemical warfare agents, highly toxic industrial compounds, explosives, and drugs of abuse. Detection limits in the low part per billion range, fast response times, and simple instrumentation make this technique more and more popular. Common ion mobility spectrometers work by employing a radioactive source to provide electrons with high energy to ionize analytes in a series of chemical reactions. General security as well as regulatory concerns related to radioactivity result in the need for a different ionization source which on the other hand produces ions in a similar manner as a radioactive source since the ion chemistry is well- known. Here we show the application of a novel nonradioactive source that produces spectra similar to those obtained with radioactive tritium sources. Using this source in a pulsed mode offers the additional advantage of selecting certain analytes by their recombination lime and thus significantly increasing the selectivity. The successful isolation of a target signal in the presence of contaminants using a pulsed electron beam or more precisely the difference in recombination times will be demonstrated for the case of dimethyl-methylphosphonate (DMMP) showing the potential of this source to reduce the possibility for false-positive detection of corresponding chemical warfare agents (CWA) by IMS. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry (IMS) is a well-known method for detecting hazardous compounds in air. Typical applications are the detection of chemical warfare agents, highly toxic industrial compounds, explosives, and drugs of abuse. Detection limits in the low part per billion range, fast response times, and simple instrumentation make this technique more and more popular. In particular, there is an increasing demand for miniaturized low-cost IMS for hand-held devices and air monitoring of public areas by sensor networks. In this paper, we present a miniaturized aspiration condenser type ion mobility spectrometer for fast detection of chemical warfare agents. The device is easy to manufacture and allows single substance identification down to low part per billion-level concentrations within seconds. The improved separation power results from ion focusing by means of geometric constraints and fluid dynamics. A simple pattern recognition algorithm is used for the identification of trained substances in air. The device was tested at the German Armed Forces Scientific Institute for Protection Technologies-NBC-Protection. Different chemical warfare agents, such as sarin, tabun, soman, US-VX, sulfur mustard, nitrogen mustard, and lewisite were tested. The results are presented here. [ABSTRACT FROM AUTHOR]

Abstract: Ion mobility spectrometry is a well-known method for detecting hazardous compounds in air. Detection limits in the low ppb range and fast response times make this technique more and more popular. Typical applications are the detection of chemical warfare agents, toxic industrial compounds, explosives and drugs. This paper describes the concept and preliminary results of a simple planar ion-focusing aspiration condenser as an ion mobility spectrometer (IMS). Compared to other aspiration condenser IMS with identical ion carrier gas and drift gas, our design has separate gas flows. This allows fluidic focusing of the ion carrier gas by means of geometric constrains. Thus, ions are focused before separation, which results in improved separation power. Furthermore, humidity in the ion carrier gas does not effect peak position in the ion mobility spectrum when using dry drift gas. In addition, the system is easy to fabricate at low-cost, has small dimensions and low power consumption. First measurements of 1-Octanol in air demonstrate the potential of this novel concept. [Copyright &y& Elsevier]

Ion mobility spectrometry provides ion separation in the gas phase mainly based on differing ion-neutral collision cross sections, enabling powerful analysis of many isomers. However, the separation also has a miniscule mass dependence due to the acceleration and collision properties. In this work, we show for the first time that using a compact ultra-high-resolution ion mobility spectrometer with a resolving power of 250 and an UV ionization source enables the separation of isotopologues with ion mobility spectrometry. This is demonstrated for regular and perdeuterated acetone, benzene, and toluene as well as toluene-13C7 in nitrogen and in purified air as drift gas. The observed peak shifts in the ion mobility spectrum agree with the basic ion mobility equation when using nitrogen as drift gas and also agree with a combination of this equation with Blanc's law when using purified air as drift gas. For benzene and toluene, a reduction in the ion-neutral collision cross section of the isotopically replaced species is observed. Furthermore, a third peak formed from regular and perdeuterated acetone is observed, which can most likely be attributed to the exchange of a methyl group. [ABSTRACT FROM AUTHOR]

The Renewable Energy Act 2023 (§39i) requires reducing corn silage in biogas plants from 40 % to 30 % in 2026. Since corn silage yields the highest biogas per weight unit of all biogas feedstocks, this poses new challenges for biogas plant operators. However, alternative biogas feedstocks not harvested directly from the field may contain siloxanes due to the use of care products and disinfectants. The conversion of siloxanes into silicon dioxide during the combustion process seriously threatens the lifetime and efficiency of the used gas engine, even in very low concentrations. Consequently, we present a highly sensitive measurement system for monitoring biogas. Detection limits down to 0.037 mg/m³ for the tested siloxanes have been reached. Furthermore, ketones can be detected down to 0.002 mg/m³, alcohols down to 0.001 mg/m³. The device combines an ultra-fast polarity switching ion mobility spectrometer with a switching time of 12 ms and a resolving power of R P = 70, a gas chromatographic pre-separation, and a non-dispersive infrared sensor for methane. In this context, we analyzed the biogas composition for volatile substances and siloxanes, whereby we only found the volatile substances. For demonstration, biogas was analyzed at three different stages during the gas purification process. [Display omitted] [ABSTRACT FROM AUTHOR]

• How the ionization region volume of an IMS affects GC-IMS separation power. • Sample depletion leads to reduced effective detector volume and signal intensities. • Finding the optimum operating: SNR vs. peak broadening. In this work, the influence of the sample gas flow rate and the ionization region volume of an ion mobility spectrometer (IMS) used as a detector in gas chromatography (GC) on GC-IMS peak shape has been investigated. Therefore, a drift tube IMS with a field-switching ion shutter, a defined ionization region volume and an ultra-violet radiation source was used. To identify the influence of the sample gas flow rate entering the ionization region (equals the GC carrier gas flow rate if no further make-up gas is used) and the ionization region volume on peak broadening and signal intensity, different sample volumes as they would elute from a GC were tested at a variety of sample gas flow rates at a given ionization region volume. The results clearly show that for low sample gas flow rates a depletion of sample molecules in the ionization region leads to a significant decrease in effective detector volume but also to reduced signal intensities. Therefore, for optimal performance of a GC-IMS, the optimal operating point of the GC should match the flow range, where the IMS provides the best compromise between signal-to-noise ratio and peak broadening. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry provides information about molecular structures of ions. Hence, high resolving power allows separation of isomers which is of major interest in several applications. In this work, we couple our high-resolution ion mobility spectrometer (IMS) with a resolving power of Rp = 100 to a time-of-flight mass spectrometer (TOF-MS). Besides, the benefit of an increased resolving power such an IMS-MS also helps analyzing and understanding the ionization processes in IMS. Usually, the coupling between IMS and TOF-MS is realized by synchronizing data acquisition of the IMS and MS resulting in two-dimensional data containing ion mobility and mass spectra. However, due to peak widths of less than 100 μs in our high-resolution IMS, this technique is not practicable due to significant peak broadening during the ion transfer into the MS and an insufficient data acquisition rate of the MS. Thus, a novel but simple interface between the IMS and MS has been designed which minimizes ion losses, allows recording of ion mobility at full IMS resolving power, and enables a shuttered transmission of ions into the MS. The interface is realized by replacing the Faraday plate used in IMS by a Faraday grid that is shielded by two additional aperture grids. For demonstration, positive product ions of benzene, toluene, and m-xylene in air are investigated. The IMS is equipped with a radioactive 3H source. Besides the well-known product ions M+ and M·NO+, a dimer ion is also observed for benzene and toluene, consisting of two molecules and three further hydrogen atoms.ᅟ [ABSTRACT FROM AUTHOR]

Ion mobility spectrometers (IMS) are compact devices for extremely sensitive detection of proton and electron affine volatile compounds down to low ppt v concentrations within less than a second. The measuring principle requires ionization of the target analyte. Most IMS employ radioactive electron sources, such as 63 Ni or 3 H. These radioactive materials suffer from legal restrictions limiting the fields of application. Furthermore, the electron emission has a predetermined intensity and cannot be controlled or disabled. In a previous work, we replaced the axially mounted 3 H source of our ion mobility spectrometer with a commercially available X-ray source operated at low acceleration voltage of 4.5 kV to be applicable in most application without legal restrictions. However, the high penetration depth of the radiation together with the statistical behavior of the X-ray ionization process led to an increase of Fano noise and thus a limited signal-to-noise ratio. Therefore, the X-ray source is now mounted orthogonal to the drift tube in order to avoid Fano noise. Here, we compare the analytical performance of this orthogonal setup with the axially mounted X-ray source. The noise level is significantly reduced. This improves the signal-to-noise ratio from 700 with the axially placed source to more than 3000 with the orthogonally placed source, while the resolving power still remains at R = 100. Furthermore, typical limits of detection for some model substances in the low ppt v range in positive and negative ion mode are given. [ABSTRACT FROM AUTHOR]

Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with high ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region.ᅟ [ABSTRACT FROM AUTHOR]

High kinetic energy ion mobility spectrometry (HiKE-IMS) allows for sensitive trace gas analysis within seconds, mitigating many disadvantages of standard ion mobility spectrometers through operation at reduced pressure and high electric field strengths. However, these advantages usually come at the cost of reduced resolving power, ranging from a maximum of 75 down to 50 at a reduced field strength of 120 Td for the original device. In this work, we present an extended theory for HiKE-IMS resolving power and a novel tristate ion shutter principle able to achieve initial ion packet widths of 1 µs without significant mobility discrimination. Such an ultrashort injection time allows for improving the resolving power of the HiKE-IMS to 140 for a wide range of reduced electric field strengths. With this resolving power, separating all ion species generated from a mixture of benzene, toluene, and xylene is possible. Furthermore, a resolving power of 140 is sufficient to partially separate isotopologues under high electric field strengths. [ABSTRACT FROM AUTHOR]

Ion mobility spectrometry is a powerful and low-cost technique for the identification of chemical warfare agents, toxic chemicals, or explosives in air. Drift tube ion mobility spectrometers (DT-IMS) separate ions by the absolute value of their low field ion mobility, while field asymmetric ion mobility spectrometers (FAIMS) separate them by the change of their ion mobility at high fields. However, using one of these devices alone, some common and harmless substances show the same response as the hazardous target substances. In order to increase the selectivity, orthogonal data are required. Thus, in this work, we present for the first time an ambient pressure ion mobility spectrometer which is able to separate ions both by their differential and low field mobility, providing additional information for selectivity enhancement. This novel field asymmetric time of flight ion mobility spectrometer (FAT-IMS) allows high repetition rates and reaches limits of detection in the low ppb range common for DT-IMS. The device consists of a compact 44 mm drift tube with a tritium ionization source and a resolving power of 70. An increased separation of four substances with similar low field ion mobility is shown: phosgene (K0 = 2.33 cm2/ (V s)), 1,1,2-trichlorethane (K0 = 2.31 cm2/(V s)), chlorine (K0 = 2.24 cm2/(V s)), and nitrogen dioxide (K0 = 2.25 cm2/(V s)). Furthermore, the behavior and limits of detection for acetonitrile, dimethyl methylphosphonate, diisopropyl methyl phosphonate in positive polarity and carbon dioxide, sulfur dioxide, hydrochloric acid, cyanogen chloride, and hydrogen cyanide in negative polarity are investigated. [ABSTRACT FROM AUTHOR]

X-ray was utilized as an ionization source for differential ion mobility spectrometry (DMS) for the first time. The utilization of this ionization source increases the potential of DMS system for on-site based applications. The influence of experimental parameters (e.g. accelerating voltage, filament current, and separation field) on the analysis of model compounds was investigated and discussed. It was found that both the positive and the negative reactive ion peaks [RIP(+) and RIP(−)] formed during X-ray ionization are identical with those observed with the traditional 63 Ni radioactive ion source. This is especially notable for RIP(−), because the chemistry provided by other nonradioactive sources in the negative mode is more complicated or even different than that observed with a 63 Ni source. Increase of either filament current or accelerating voltage resulted in increased intensity of both RIP(+) and RIP(−). However, because of the materials used for construction of X-ray adapter the maximal level of filament current and accelerating voltage used in this study were limited to 700 mA and 5 kV, respectively. Analytical performance was determined with two model compounds (acetone and methyl salicylate) using X-ray and directly compared to 63 Ni ionization source. When X-ray was coupled to DMS, calculated LOD values were found to be within the range of 0.17–1.52 ppb v/v (concentration in the carrier gas). These values are competitive with those calculated for DMS equipped with traditional 63 Ni radioactive ionization source. The obtained results are promising enough to ensure the potential of X-ray as ionization source for DMS. [ABSTRACT FROM AUTHOR]

Here, we present a new and an easy to assemble dielectric barrier discharge plasma ionization source based on printed circuit boards with two parallel isolated electrodes for generating a plasma inside an inert fused silica capillary. For demonstration, this plasma source is coupled to an ion mobility spectrometer. With two different sample gas feeds the analytes can either pass through the plasma or bypass the plasma before entering the reaction region of the ion mobility spectrometer, allowing for different ionization pathways, e.g. electron impact ionization, ionization by excited species, e.g. helium metastables, or chemical ionization via reactant ions generated inside or downstream of the plasma. The plasma source, in particular, the electrode geometry and the capillary diameter were designed with the help of electric field simulations. A rectangular electrode with a height of at least twice the outer diameter of the capillary turned out to be ideal, in both the simulation and the experiment. Furthermore, a simple control electronics has been developed, which can be easily applied to other plasma sources. With the plasma source presented here, detection limits in the mid ppt v range have been reached. [Display omitted] • Easy to assemble plasma ionization source based on printed circuit boards. • Two different sample gas feeds for different ionization pathways and limits of detection in the ppt v to ppb v range. • Wide useable gas flow range for various applications in mass spectrometry and ion mobility spectrometry. • Electrode geometry including length and height and capillary diameter optimized by using field simulations. • Simple control electronics for plasma ionization sources with isolated output. [ABSTRACT FROM AUTHOR]

One major drawback of ion mobility spectrometry (IMS) is the dependence of the response to a certain analyte on the concentration of water or the presence of other compounds in the sample gas. Especially for low proton affine analytes, e.g., benzene, which often exists in mixtures with other volatile organic compounds, such as toluene and xylene (BTX), a time-consuming preseparation is necessary. In this work, we investigate BTX mixtures using a compact IMS operated at decreased pressure (20 mbar) and high kinetic ion energies (HiKE-IMS). The reduced electric field in both the reaction tube and the drift tube can be independently increased up to 120 Td. Under these conditions, the water cluster distribution of reactant ions is shifted toward smaller clusters independent of the water content in the sample gas. Thus, benzene can be ionized via proton transfer from H3O+ reactant ions. Also, a formation of benzene ions via charge transfer from NO+ is possible. Furthermore, the time for interaction between ions and neutrals of different analytes is limited to such an extent that a simultaneous quantification of benzene, toluene, and xylene is possible from low ppbv up to several ppmv concentrations. The mobility resolution of the presented HiKE-IMS varies from R = 65 at high field (90 Td) to R = 73 at lower field (40 Td) in the drift tube, which is sufficient to separate the analyzed compounds. The detection limit for benzene is 29 ppbv (2 s of averaging) with 3700 ppmv water, 12.4 ppmv toluene, and 9 ppmv xylene present in the sample gas. Furthermore, a less-moisture-dependent benzene measurement with a detection limit of 32 ppbv with ca. 21 000 ppmv (90% relative humidity (RH) at 20 °C) water present in the sample gas is possible evaluating the signal from benzene ions formed via charge transfer. [ABSTRACT FROM AUTHOR]

Identifying the compounds of an unknown gas mixture by using an ion mobility spectrometer (IMS) is a difficult task, because several ion species can be generated in the ionization process. One method to analyze the occurring peaks in an IMS spectrum is coupling an IMS to a mass spectrometer (MS). In our setup we coupled a ³H drift tube IMS to a Bruker micrOTOF II. Therefore, the detector plate of the IMS is pierced and a transfer capillary is inserted. The ions are transferred via gas flow and electric fields into the MS. The transmission of the ions through the transfer capillary can be shuttered very precisely by increasing the electric potential of the detector generating a repulsive electric field. Thus, it is possible to transfer single ion clouds of generated IMS spectra into the mass spectrometer where a corresponding mass spectrum is generated. In this work we analyze the positive and negative IMS spectra of single analytes as well as gas mixtures and characterize the occurring ion species. [ABSTRACT FROM AUTHOR]

Here we report the first High Kinetic Energy-Ion Mobility Spectrometry-Mass Spectrometric (HiKE-IMS-MS) investigations involving four fluranes; isoflurane, enflurane, sevoflurane and desflurane. Unlike standard (atmospheric pressure) IMS, HiKE-IMS can detect these compounds in positive ion mode. This is because its low-pressure environment (∼ 14 mbar) and the associated short ion drift times in the HiKE-IMS ensure the reagent ions O 2 +• and H 3 O+ are present in the reaction region, and these can react with the fluranes by dissociative charge and proton transfer, respectively. However, their ion intensities are very dependent on the value of the reduced electric field (E/N) applied and the humidity of the air in the reaction region of the HiKE-IMS. In this paper we explore the potential use of HiKE-IMS for air quality control and breath analysis of fluranes. To help in the interpretation of the ion mobility spectra, and hence the ion-flurane chemistry occurring in reaction region, a HiKE-IMS was coupled to a Time-of-Flight Mass Spectrometer so that the m/z values of both the reagent and product ions that are contained within the various ion mobility peaks observed could be identified with a high level of confidence. The dependencies of the intensities of these ions as functions of E/N (30–115 Td) and humidity in the reaction region are reported. A number of product ions have been observed only under low humidity conditions (H 2 O volume-mixing ratio ∼ 100 ppm v), including CHF 2 + and CHFCl + for isoflurane and enflurane, CHF 2 +, CF 3 + and C 3 H 2 F 5 O+ for desflurane, and CH 3 O+, CHF 2 +, C 3 H 3 F 4 O+, C 4 H 3 F 6 O+ and C 4 H 3 F 6 O+(H 2 O) for sevoflurane. It is interesting to note that CH 3 O+, CHF 2 +, CHFCl+ and CF 3 + have shorter drift times than that measured for O 2 +•. This is explained by resonant charge transfer reaction processes occurring in the drift region: O 2 +• + O 2 ⇌ O 2 +•.O 2 ⇌ O 2 + O 2 +•. [Display omitted] • First positive ion mode HiKE-IMS-MS investigation of four fluranes. • Ionisation of these fluranes in positive mode using HiKE-IMS is possible with O 2 +.• • Product ions are assigned to specific regions in the ion mobility spectra. • HiKE-IMS would be suited for air quality control of these fluranes. [ABSTRACT FROM AUTHOR]