Mobility Spectrometer Research Articles

Differentiation of aspirated nasal air from room air using analysis with a differential mobility spectrometry-based electronic nose: a proof-of-concept study

Over the last few decades, breath analysis using electronic nose (eNose) technology has become a topic of intense research, as it is both non-invasive and painless, and is suitable for point-of-care use. To date, however, only a few studies have examined nasal air. As the air in the oral cavity and the lungs differs from the air in the nasal cavity, it is unknown whether aspirated nasal air could be exploited with eNose technology. Compared to traditional eNoses, differential mobility spectrometry uses an alternating electrical field to discriminate the different molecules of gas mixtures, providing analogous information. This study reports the collection of nasal air by aspiration and the subsequent analysis of the collected air using a differential mobility spectrometer. We collected nasal air from ten volunteers into breath collecting bags and compared them to bags of room air and the air aspirated through the device. Distance and dissimilarity metrics between the sample types were calculated and statistical significance evaluated with Kolmogorov-Smirnov test. After leave-one-day-out cross-validation, a shrinkage linear discriminant classifier was able to correctly classify 100% of the samples. The nasal air differed (p < 0.05) from the other sample types. The results show the feasibility of collecting nasal air by aspiration and subsequent analysis using differential mobility spectrometry, and thus increases the potential of the method to be used in disease detection studies.

Preparation of Dr\xe4ger Atlan A350 and General Electric Healthcare Carestation 650 anesthesia workstations for malignant hyperthermia susceptible patients

BackgroundPatients at risk of malignant hyperthermia need trigger-free anesthesia. Therefore, anesthesia machines prepared for safe use in predisposed patients should be free of volatile anesthetics. The washout time depends on the composition of rubber and plastic in the anesthesia machine. Therefore, new anesthesia machines should be evaluated regarding the safe preparation for trigger-free anesthesia. This study investigates wash out procedures of volatile anesthetics for two new anesthetic workstations: Dräger Atlan A350 and General Electric Healthcare (GE) Carestation 650 and compare it with preparation using activated charcoal filters (ACF).MethodsA Dräger Atlan and a Carestation 650 were contaminated with 4% sevoflurane for 90 min. The machines were decontaminated with method (M1): using ACF, method 2 (M2): a wash out method that included exchange of internal parts, breathing circuits and soda lime canister followed by ventilating a test lung using a preliminary protocol provided by Dräger or method 3 (M3): a universal wash out instruction of GE, method 4 (M4): M3 plus exchange of breathing system and bellows. Decontamination was followed by a simulated trigger-free ventilation. All experiments were repeated with 8% desflurane contaminated machines. Volatile anesthetics were detected with a closed gas loop high-resolution ion mobility spectrometer with gas chromatographic pre-separation attached to the bacterial filter of the breathing circuits. Primary outcome was time until < 5 ppm of volatile anesthetics and total preparation time.ResultsTime to < 5 ppm for the Atlan was 17 min (desflurane) and 50 min (sevoflurane), wash out continued for a total of 60 min according to protocol resulting in a total preparation time of 96-122 min. The Carestation needed 66 min (desflurane) and 24 min (sevoflurane) which could be abbreviated to 24 min (desflurane) if breathing system and bellows were changed. Total preparation time was 30-73 min. When using active charcoal filters time to < 5 ppm was 0 min for both machines, and total preparation time < 5 min.ConclusionBoth wash out protocols resulted in a significant reduction of trace gas concentrations. However, due to the complexity of the protocols and prolonged total preparation time, feasibility in clinical practice remains questionable. Especially when time is limited preparation of the anesthetic machines using ACF remain superior.

ХАРАКТЕРИСТИКИ БЕССЕТОЧНОГО ДВУХЭЛЕКТРОДНОГО ИОННОГО ЗАТВОРА ПРИ АТМОСФЕРНОМ ДАВЛЕНИИ

As an ion gate for the formation of a short ion pulse in an ion mobility spectrometer, a gridless design with two coaxial diaphragms is proposed. It has been experimentally shown that, depending on the geometric and electrical parameters of this shutter, there is an optimal duration of the electric pulse opening the gate, which provide the maximum amplitude of the ion pulse.

ОЦЕНКА ВЛИЯНИЯ ОБЪЕМНОГО ЗАРЯДА НА РАЗРЕШЕНИЕ ИОН-ДРЕЙФОВОГО СПЕКТРОМЕТРА

The paper presents an analytical model describing the dynamics of ion cloud, taking into account the action of space charge during a motion in ion mobility spectrometer — starting from the reaction region, where the shutter forms an ion pulse, and the further drift of the formed ion pulse towards the collector. The presented model lets to estimate the degree of influence of the space charge on possible ion losses and the resolution of ion mobility spectrometer. The effect of the space charge becomes noticeable, starting with the ion density of 106 cm–3. Comparison of the results obtained using the analytical model with the results of numerical solution of the initial equations shows that they practically coincide.

Monitoring the Yogurt Fermentation Process and Analysis of Flavor Compounds using a Novel Ion Mobility Spectrometer

Monitoring the Yogurt Fermentation Process and Analysis of Flavor Compounds using a Novel Ion Mobility Spectrometer

Developing Macro-Raman Mapping as a Tool for Studying the Pigment Distribution of Art Objects.

Raman spectroscopy is a well-appreciated technique in cultural heritage research for its ability to obtain molecular information nondestructively. During Raman mapping experiments, advantage is taken of the excellent spatial resolution of the approach, allowing to visualize the spatial distribution of the molecules. In the current research, macro-Raman mapping is proposed, allowing us to map large areas of an artwork (typically tens or hundreds of square centimeters). Therefore, a new setup is made, using a commercially available mobile Raman spectrometer and fast translation stages. Moreover, the probe is equipped with a triangulator to measure the distance to the surface of the artwork and thus achieving accurate focusing of the Raman probe. Finally, the correct setup is guaranteed by using a calibration module that is designed to allow for spectral calibration and aligning all components of the probe. The use of the method is demonstrated by three cases, where different data processing techniques are illustrated.

A real-time gas monitoring system based on ion mobility spectrometry for workplace environmental measurements.

A volatile organic compounds (VOC) gas monitor was developed using an ion mobility spectrometer (IMS). It was designed for real-time monitoring in work environments, where gas chromatography/mass spectrometry (GC/MS) does not perform well. To evaluate the identification capability, response time, and quantitative accuracy of this device, experiments were conducted using methyl ethyl ketone. This is widely used in many factories, and its short-term exposure limit (STEL) has been set by the American Conference of Governmental Industrial Hygienists. Because the ionizable amount of methyl ethyl ketone has already been exceeded in STEL value of 300 ppm which belongs to the measurement range of interest in this study, this study estimated the peak shift amount rather than the peak intensity. Calibration curves with high accuracy were obtained in a range including 300 ppm which is the STEL of methyl ethyl ketone. The results of the experiment suggest that the device can be used for monitoring chemical substances in a work environment.

High efficient solid-phase microextraction based on a covalent organic framework for determination of trifluralin and chlorpyrifos in water and food samples by GC-CD-IMS

Novel porous covalent organic framework (COF) based on condensation reaction between cyanuric chloride, 4,4′-ethylendianiline, and 3,4,9,10-perylenetetracarboxylic dianhydride was synthesized via sealed tube condition. The results COF was used as a new adsorbent for solid-phase microextraction (SPME) for extracting trifluralin and chlorpyrifos from vegetables, fruit samples, and wastewater. Gas chromatograph with a corona discharge-ion mobility spectrometer as the detector was also used for analyzing the target analytes. Some parameters that affected the extraction, such as stirring rate, time and temperature of extraction and pH were investigated, exhaustively. The detection limits were 0.13, and 0.15 µg/L and the linear ranges of 0.45–20 and 0.50–25 µg/L with a linearity coefficient of 0.9965 and 0.9987 were also obtained for trifluralin and chlorpyrifos, respectively. The method was applied successfully to analyze some real samples of cucumber, carrot, grape, and agriculture wastewater, and the results showed a relative recovery in the range of 87% to 110%.

Analysis of drugs including illicit and new psychoactive substances in oral fluids by gas chromatography-drift tube ion mobility spectrometry

In this study, a gas chromatograph (GC) has been coupled to a drift tube ion mobility spectrometer (IMS) in order to develop an analytical procedure for the determination of psychoactive substances in oral fluids. Working parameters, including the GC-IMS interface ones, were adjusted in order to obtain sensitive and robust signals. A volume of 500 μL of oral fluid was extracted with 250 μL chloroform and, after centrifugation, were injected into the GC-IMS system. Amphetamine, methylone, α-PVP, ketamine, lidocaine, MPHP, cocaine, THJ-2201, and 5F-ADB were employed as model compounds, providing limits of detection from 6 to 15 μg L−1 and recoveries from 70 to 115% for field oral fluids spiked with target analytes at 250, 500, and 600 μg L−1. Moreover, two oral fluid certified reference materials were analysed by the proposed GC-IMS based methodology with obtained relative percentage errors lower than 8.4%, being the proposed GC-IMS procedure a reliable, selective, and sensitive technique for the determination of psychoactive substances in oral fluids.

Characterization of vapor emissions from pentaerythritol tetranitrate solids in nitrogen by atmospheric pressure chemical ionization mass spectrometry and in ambient air by ion mobility spectrometry

ABSTRACT The emission of vapors from solid samples of Pentaerythritol Tetranitrate (PETN) in a flow of nitrogen from ~20 to 140°C was characterized using atmospheric pressure chemical ionization mass spectrometry equipped with a 63Ni ion source. Mass analysis of ions derived from vapors from military grade PETN at room temperature, without deposition from solution, included only NO3 − (62 Da) and HNO3 ·NO3 − (125 Da) and were attributed to residual levels of nitric acid in the PETN solid. The vapor level of HNO3 persisted until 80°C and after this declined asymptotically to background levels; ions observed above 110°C were nitrate adducts of molecular PETN including (PETN)n ·NO3 − with mass values of 378 Da (n = 1) and 695 Da (n = 2). Subsequent reheating of the PETN solid caused an increase release of nitric acid and formation, above 140°C, of the same nitrate adducts of PETN,, consistent with thermal degradation of some PETN to nitric acid. A commercial handheld ion mobility spectrometer was used to sample airborne vapors from solid PETN in an open container and heated in ambient air. The ion mobility spectra showed that ionization chemistry was rapidly transformed from O2 − to NO3 − which persisted indefinitely and produced ion above 80°C with Ko values of 1.48, 1.21, 1.15, and 1.10 cm2/V s. These relatively low-mobility peaks were attributed to cluster ions of nitrate with nitric acid and molecular PETN generated from thermal decomposition and some vaporization of solid PETN. Persistence of nitrate as a reactant ion in the handheld analyzer suggested a need for specialized designs and materials for such explosives vapor measurements.

Rapid simultaneous determination of ketamine and midazolam in biological samples using ion mobility spectrometry combined by headspace solid-phase microextraction

Ketamine (Ket) and midazolam (Mdz) are among well-known anesthetic agents which frequently coadministered in surgical procedures and emergency department. Only a few reports have been published for the simultaneous analysis of these compounds. In the present study, we reported a simple, sensitive, and rapid method for simultaneous determination of Ket and Mdz based on headspace solid-phase microextraction coupled with ion mobility spectrometry (HS-SPME-IMS). Ion mobility spectrometer operated under positive mode of a corona discharge ionization source using ammonia as a dopant. The effective parameters on the extraction process consisting of pH of the sample, extraction temperature, extraction time, salt concentration were optimized. The calibration plots exhibited good linearity over the concentration ranges of 10-800 and 100-1500 µg L−1 and detection limit of 8.9 and 52 µg L−1 for Ket and Mdz respectively with correlation coefficients greater than 0.99. The relative standard deviation (RSD) for five replicate measurements was determined to be less than 8%. Finally, the applicability of the proposed method was tested in human plasma and serum samples. These tests showed that the matrix in serum samples interfere with midazolam determination but quantitative recoveries from 85 to 95 % were obtained for both drugs in the human plasma samples. The method herein provides simple and suitable approach while minimizing sample preparation and the overall complexity of the analysis in comparison to existing methodologies.

COVID-19 screening using breath-borne volatile organic compounds

Rapid screening of COVID-19 is key to controlling the pandemic. However, current nucleic acid amplification involves lengthy procedures in addition to the discomfort of taking throat/nasal swabs. Here we describe potential breath-borne volatile organic compound (VOC) biomarkers together with machine learning that can be used for point-of-care screening of COVID-19. Using a commercial gas chromatograph-ion mobility spectrometer, higher levels of propanol were detected in the exhaled breath of COVID-19 patients (N = 74) and non-COVID-19 respiratory infections (RI) (N = 30) than those of non-COVID-19 controls (NC)/health care workers (HCW) (N = 87), and backgrounds (N = 87). In contrast, breath-borne acetone was found to be significantly lower for COVID-19 patients than other subjects. Twelve key endogenous VOC species using supervised machine learning models (support vector machines, gradient boosting machines (GBMs), and Random Forests) were shown to exhibit strong capabilities in discriminating COVID-19 from (HCW + NC) and RI with a precision ranging from 91% to 100%. GBM and Random Forests models can also discriminate RI patients from healthy subjects with a precision of 100%. In addition, the developed models using breath-borne VOCs could also detect a confirmed COVID-19 patient but with a false negative throat swab polymerase chain reaction test. It takes 10 min to allow an entire breath test to finish, including analysis of the 12 key VOC species. The developed technology provides a novel concept for non-invasive rapid point-of-care-test screening for COVID-19 in various scenarios.

Development of Real-time Gas monitor Using an Ion Mobility Spectrometer for Work Environment Measurement

Development of Real-time Gas monitor Using an Ion Mobility Spectrometer for Work Environment Measurement

Successive reactions in field induced fragmentation spectra from tandem ion mobility spectrometry at ambient pressure and their influence on classification by neural networks

Field-induced fragmentation (FIF) spectra were obtained for mobility isolated protonated monomers of volatile organic compounds from six chemical families at 130 to 157 Td in the reactive stage of a tandem ion mobility spectrometer at 98 °C. The extent of fragmentation at ambient pressure increased linearly with field strength for n-alcohols of carbon number 3 to 5, for n-akyl acetates of carbon numbers 4 to 11, and for n-aldehydes and ethers not previously fragmented at 129 Td and 93 °C. Efficiencies of fragmentation at 157 Td ranged from 57 to 100% for n-alcohols, 25–100% for n-alkyl acetates of carbon numbers 5 to 8 (10–29% for carbon numbers 9 to 11), 29–84% for ethers of carbon numbers 8 and below, and 7–57% for n-alkanes of carbon numbers 7 to 11. Multiple, low mass ions in FIF spectra were attributed to second and third levels of fragmentation with identical reduced mobility coefficients characteristic of a chemical class. Differences in fragment ion patterns between chemical classes were attributed to structural information from field-induced fragmentation. Classification by chemical class using neural networks was significantly improved for acetates and aldehydes with increased fragmentation at 157 Td. Spectra without fragmentation were poorly classified. Models of ion energy within the reactive stage suggested that ions undergoing decomposition were not symmetrically distributed between etched metal grids in the reactive stage.

Predicting ion mobility as a function of the electric field for small ions in light gases

High resolution mobility devices such as Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) and Differential Mobility spectrometers (DMS) use strong electric fields to gas concentration ratios, E/N, to separate ions in the gas phase. While extremely successful, their empirical results show a non-linear, ion-dependent relation between mobility K and E/N that is difficult to characterize. The one-temperature theory Mason-Schamp equation, which is the most widely used ion mobility equation, unfortunately, cannot capture this behavior. When the two-temperature theory is used, it can be shown that the K−E/N behavior can be followed quite closely numerically by equating the effect of increasing the field to an increase in the ion temperature. This is attempted here for small ions in a Helium gas environment showing good agreement over the whole field range. To improve the numerical characterization, the Lennard-Jones (L-J) potentials may be optimized. This is attempted for Carbon, Hydrogen, Oxygen and Nitrogen at different degrees of theory up to the fourth approximation, which is assumed to be exact. The optimization of L-J improves the accuracy yielding errors of about 3% on average. The fact that a constant set of L-J potentials work for the whole range of E/N and for several molecules, also suggests that inelastic collisions can be circumvented in calculations for He. The peculiar K−E/N hump behaviors are studied, and whether mobility increases or decreases with E/N is shown to derive from a competition between relative kinetic energy and the interaction potentials.

Combining instrument inversions for sub-10 nm aerosol number size-distribution measurements

Resolving aerosol dynamical processes in the sub-10 nm range is crucial for our understanding of the contribution of new particle formation to the global cloud condensation nuclei budget or air pollution. Accurate measurements of the particle size distribution in this size-range are challenging due to high diffusional losses and low charging and/or detection efficiencies. Several instruments have been developed in recent years in order to access the sub-10 nm particle size distribution; however, no single instrument can provide high counting statistics, low systematic uncertainties and high size-resolution at the same time. Here we compare several data inversion approaches that allow combining data from different sizing instruments during the inversion and provide python/Julia packages for free usage of the methods. We find that Tikhonov regularization using the L-curve method for optimal regularization parameter estimation gives very reliable results over a wide range of tested data sets and clearly improves standard inversion approaches. Kalman Filtering or regularization using a Poisson likelihood can be powerful tools, especially for well-defined chamber experiments or data from mobility spectrometers only, respectively. Nullspace optimization and non-linear iterative regression are clearly inferior compared to the aforementioned methods. We show that with regularization we can reconstruct the size-distribution measured by up to 4 different mobility particle size spectrometer systems and several particle counters for datasets from Hyytiälä and Helsinki, Finland, revealing the sub-10 nm aerosol dynamics in more detail compared to a single instrument assessment.

Thermal decomposition of the chloride and nitrate adducts of pentaerythritol tetranitrate in air at ambient pressure using a cross flow design tandem ion mobility spectrometry

The thermal decomposition of the chloride adduct of pentaerythritol tetranitrate (PETN) has been studied with a new cross-flow sample introduction, dual shutter, ion mobility spectrometer. Chloride anions, produced in an ion source, react with PETN introduced by a nebulizer into a flow of heated gas orthogonal to the drift gas flow. This cross-flow procedure allows PETN introduction from solution at drift gas temperatures where the PETN∙Cl¯ intensity is sufficiently intense and stable to allow characterization of its thermal decomposition kinetics. Dual shutter operation allows the selection of PETN∙Cl¯ for observation of its thermal decomposition in the electrostatic drift field. In this adduct, Cl¯ displaces NO3¯ in an SN2 reaction with an activation energy of 80 ± 7 kJ mol-1 over the temperature range 145 °C–165 °C. At temperatures above 165 °C, decomposition occurs before ion selection, resulting in the release of NO3¯ and PETN∙NO3¯ becomes the sole adduct ion. PETN∙NO3¯ decomposes over the temperature range 175 °C–200 °C with an activation energy of 92 ± 8 kJ mol-1. Density functional calculations are used to interpret the results.

Rapid measurement of RH-dependent aerosol hygroscopic growth using a humidity-controlled fast integrated mobility spectrometer (HFIMS)

Abstract. The ability of aerosol particles to uptake water (hygroscopic growth) is an important determinant of aerosol optical properties and radiative effects. Aerosol hygroscopic growth is traditionally measured by humidified tandem differential mobility analyzers (HTDMA), in which size-selected dry particles are exposed to elevated relative humidity (RH), and the size distribution of humidified particles is subsequently measured using a scanning mobility particle sizer. As a scanning mobility particle sizer can measure only one particle size at a time, HTDMA measurements are time consuming, and ambient measurements are often limited to a single RH level. Pinterich et al. (2017b) showed that fast measurements of aerosol hygroscopic growth are possible using a humidity-controlled fast integrated mobility spectrometer (HFIMS). In HFIMS, the size distribution of humidified particles is rapidly captured by a water-based fast integrated mobility spectrometer (WFIMS), leading to a factor of ∼10 increase in measurement time resolution. In this study we present a prototype HFIMS that extends fast hygroscopic growth measurements to a wide range of atmospherically relevant RH values, allowing for more comprehensive characterizations of aerosol hygroscopic growth. A dual-channel humidifier consisting of two humidity conditioners in parallel is employed such that aerosol RH can be quickly stepped among different RH levels by sampling from alternating conditioners. The measurement sequence is also optimized to minimize the transition time between different particle sizes. The HFIMS is capable of measuring aerosol hygroscopic growth of six particle diameters under five RH levels ranging from 20 % to 85 % (30 separate measurements) every 25 min. The performance of this HFIMS is characterized and validated using laboratory-generated ammonium sulfate aerosol standards. Measurements of ambient aerosols are shown to demonstrate the capability of HFIMS to capture the rapid evolution of aerosol hygroscopic growth and its dependence on both size and RH.

The nano-scanning electrical mobility spectrometer (nSEMS) and its application to size distribution measurements of 1.5–25 nm particles

Abstract. Particle size measurement in the low nanometer regime is of great importance to the study of cloud condensation nuclei formation and to better understand aerosol–cloud interactions. Here we present the design, modeling, and experimental characterization of the nano-scanning electrical mobility spectrometer (nSEMS), a recently developed instrument that probes particle physical properties in the 1.5–25 nm range. The nSEMS consists of a novel differential mobility analyzer and a two-stage condensation particle counter (CPC). The mobility analyzer, a radial opposed-migration ion and aerosol classifier (ROMIAC), can classify nanometer-sized particles with minimal degradation of its resolution and diffusional losses. The ROMIAC operates on a dual high-voltage supply with fast polarity-switching capability to minimize sensitivity to variations in the chemical nature of the ions used to charge the aerosol. Particles transmitted through the mobility analyzer are measured using a two-stage CPC. They are first activated in a fast-mixing diethylene glycol (DEG) stage before being counted by a second detection stage, an ADI MAGIC™ water-based CPC. The transfer function of the integrated instrument is derived from both finite-element modeling and experimental characterization. The nSEMS performance has been evaluated during measurement of transient nucleation and growth events in the CLOUD atmospheric chamber at CERN. We show that the nSEMS can provide high-time- and size-resolution measurement of nanoparticles and can capture the critical aerosol dynamics of newly formed atmospheric particles. Using a soft x-ray bipolar ion source in a compact housing designed to optimize both nanoparticle charging and transmission efficiency as a charge conditioner, the nSEMS has enabled measurement of the contributions of both neutral and ion-mediated nucleation to new particle formation.

Studies on the Processes of Electron Capture and Clustering of Benzyl Chloride by Ion Mobility Spectrometry.

This paper presents the results of the study on the course of the benzyl chloride (BzCl) ionization process in a drift tube ion mobility spectrometer (DT IMS) in which nitrogen was used as the carrier gas. BzCl ionization follows the dissociative electron capture mechanism. The chloride ions produced in this process take part in the formation of cluster ions. Using DT IMS allows for estimation of the value of the electron attachment rate for BzCl and the equilibrium constant for the cluster ion formation. The basic experimental method used in this work was to analyze drift time spectra obtained for the introduction of the sample to the spectrometer with the drift gas. The theoretical interpretation of the results is based on the mathematical description of the ion transport. This description takes into account the phenomenon of diffusion, as well as the processes of formation and dissociation of ionic clusters occurring during the movement of ions in the drift section.