Gas Mass Spectrometric Analysis Research Articles

Argon pharmacokinetics: a solubility measurement technique.

The noble gas argon has demonstrated biological activity that may prove useful as a medical intervention. Pharmacokinetics, the disposition of the drug molecule in the body through time, is fundamental necessary knowledge to drug discovery, development and even post-marketing. The fundamental measurement in pharmacokinetic studies is blood concentration of the molecule (and its metabolites) of interest. While a physiologically based model of argon pharmacokinetics has appeared in the literature, no experimental data have been published. Thus, argon pharmaceutical development requires measurement of argon solubility in blood. This paper reports on the development of a technique based on mass spectrometry for measuring argon solubility in liquids, including blood, to be further employed in pharmacokinetics testing of argon. Based on a prototype, results are reported from sensitivity experiments using ambient air, water and rabbit blood. The key takeaway is that the system was sensitive to argon during all of the testing. We believe the technique and prototype of the quadrupole mass spectrometer gas analyzer will be capable of inferring argon pharmacokinetics through the analysis of blood samples.

A mechanistic study on the CO2 activation over Pd-containing MCM-22 zeolite based on DRIFT analysis: Impact of counter cations in the zeolite framework

Zeolites have been playing an important role in the field of so-called “Carbon dioxide Capture, Utilization, and Storage (CCUS)”. Catalytic activation of CO2 over zeolite-based catalysts has been extensively investigated, while many issues remain unsolved. In this study, the MWW-type zeolites impregnated with the Pd nanoparticles were used as the catalysts for CO2 activation. Furthermore, various amounts of charge balance cations (Na+ and H+) were added to the Pd-MWW with the intention of improving CO2 adsorption capacity. A fixed-bed reactor equipped with the Mass Spectrometer for effluent gas analysis was used to evaluate the steady-state conversion of the CO2 activation on these as-prepared catalysts from 50 to 650 °C. The compositions of the effluent gases and their associated quantities were monitored for each test. Finally, two infrared techniques (steady-state and dynamic measurements) were applied to identify the spectroscopic evidence of the heterogeneous catalysis reaction. In the first technique, the amount of chemisorbed CO2 was quantified by the infrared transmitted intensity across the samples from the vacuum to various levels of CO2 pressure at ambient temperature. The second technique investigates the hydrogenation mechanisms of adsorbates by the time-resolved FTIR with an in-situ diffusive reflectance airtight chamber. Both methods facilitated the infrared spectra of surface-adsorbed species during the hydrogenation. In combination with the temperature-programmed CO2 activation tests, this research prompted to reveal the kinetic mechanisms of CO2 activation.

Comparison of triethylgallium and diethylgallium ethoxide for β-Ga2O3 growth by metalorganic vapor phase epitaxy

The suitability of diethylgallium ethoxide (Et2GaOEt) containing Ga–O bonds as a Ga precursor for beta-gallium oxide (β-Ga2O3) growth by metalorganic vapor phase epitaxy (MOVPE) was investigated. Because estimating the growth behavior by thermodynamic analysis is difficult as a result of a lack of knowledge about the thermodynamics of Et2GaOEt, the growth behavior was estimated by observing its pyrolysis and combustion processes. Mass spectrometric analysis of gases sampled directly from an MOVPE reactor when only Et2GaOEt was supplied revealed that Et2GaOEt was decomposed to gallane, ethylene, and acetaldehyde by β-hydrogen (β-H) elimination at temperatures greater than 450 °C. However, when Et2GaOEt was supplied together with O2 to the MOVPE reactor maintained at 1000 °C, the combustion of hydrogen and carbon derived from Et2GaOEt was accelerated as the O2 supply was increased. In addition, the amount of O2 required for the complete combustion of Et2GaOEt (i.e., the amount required for the growth of β-Ga2O3) was clarified. On the basis of this pyrolysis/combustion behavior, homoepitaxial growth of β-Ga2O3 layers on β-Ga2O3 substrates was investigated at 1000 °C using Et2GaOEt as a Ga precursor and the growth behavior was compared with that when triethylgallium (Et3Ga) was used as a Ga precursor. Because both Ga precursors ultimately provide Ga gas after β-H elimination, no substantial difference in the growth rate was observed with respect to the amount of Ga atoms injected into the growth reactor. In addition, no substantial difference in crystallinity was observed; homoepitaxial layers grown at 0.7—0.8 μm/h were single crystals without twins, whereas those at 1.5—1.6 μm/h had twins. Et2GaOEt was found to be suitable as a Ga precursor for MOVPE of β-Ga2O3, with performance comparable to that of Et3Ga.

Industrial cyber-physical system driven intelligent prediction model for converter end carbon content in steelmaking plants

Industry 4.0 provides an opportunity for realizing converter intelligent steelmaking. Based on a cyber-physical system (CPS) framework for steelmaking plants, we developed a non-contact intelligent prediction model for determining molten steel carbon content. We achieved this by leveraging big data in-depth learning and optical information from converter mouth flame characteristics to realize accurate control of end-point carbon content in the process of intelligent steelmaking. The spectral information of a converter port flame was gathered using a USB2000+ spectrometer, and its main characteristics were extracted via factor analysis. The sampling frequency of the converter flue gas analysis mass spectrometer was set to obtain the carbon content of continuous molten steel during the late stages of steelmaking consistent with the spectral information collection frequency. A large sample dataset was constructed to continuously predict the carbon content of the molten steel based on the flame spectrum information of the furnace orifice. Furthermore, the parameters of a support vector regression algorithm were optimized, and the quantitative relationships among the sample data were intelligently mined to obtain a dynamic prediction model of the carbon content of 150 furnace samples. To improve the universality of the model, the initial steelmaking conditions were applied as the optimization criteria of the carbon content prediction model generated by matching different furnace samples. A support vector machine algorithm was applied to construct a model optimization classifier to obtain a universal prediction model. The results indicate that in the late stages of smelting, the spectral information of the flame in the furnace exhibited a high correlation with the carbon content of the molten steel. After testing, the prediction accuracy of this model was more than 90%. With the help of big data deep learning and CPS framework, we can build robust and accurate steelmaking intelligent control systems.

Solid state catalytic tritiation of deuterated polybutadiene through isotopic exchange and tritium addition

Deuterated-tritiated polymers are a type of promising target materials for inertial confinement fusion (ICF). The preparation of a deuterated-tritiated polymer was performed from a deuterated polybutadiene under tritium through solid state catalytic tritiation with 5 wt% Pd/BaSO4 as a catalyst. After reaction, the gas mixture in the vessel and the raw T2/Ar mixture in the flask were analyzed with a gas chromatography, a quadrupole mass spectrometer and a high resolution gas analysis mass spectrometer. The 2H-NMR and 3H-NMR spectra were employed to characterize the deuterated-tritiated polymer. Both isotopic exchange and addition during the reaction were confirmed and the tritium ratio of the deuterated-tritiated polymer was determined to be 26.5 %.The solid state tritiation free of solvents can avoid the generation of high radioactive liquids.

Experimental Approaches to Identify Selective Picomolar Inhibitors for Carbonic Anhydrase IX.

Carbonic anhydrases (CAs) regulate pH homeostasis via the reversible hydration of CO2, thereby emerging as essential enzymes for many vital functions. Among 12 catalytically active CA isoforms in humans, CA IX has become a relevant therapeutic target because of its role in cancer progression. Only two CA IX inhibitors have entered clinical trials, mostly due to low affinity and selectivity properties. The current review presents the design, development, and identification of the selective nano- to picomolar CA IX inhibitors VD11-4-2, VR16-09, and VD12-09. Compounds were selected from our database, composed of over 400 benzensulfonamides, synthesized at our laboratory, and tested for their binding to 12 human CAs. Here we discuss the CA CO2 hydratase activity/inhibition assay and several biophysical techniques, such as fluorescent thermal shift assay and isothermal titration calorimetry, highlighting their contribution to the analysis of compound affinity and structure- activity relationships. To obtain sufficient amounts of recombinant CAs for inhibitor screening, several gene cloning and protein purification strategies are presented, including site-directed CA mutants, heterologous CAs from Xenopus oocytes, and native endogenous CAs. The cancer cell-based methods, such as clonogenicity, extracellular acidification, and mass spectrometric gas-analysis are reviewed, confirming nanomolar activities of lead inhibitors in intact cancer cells. Novel CA IX inhibitors are promising derivatives for in vivo explorations. Furthermore, the simultaneous targeting of several proteins involved in proton flux upon tumor acidosis and the disruption of transport metabolons might improve cancer management.

Phase composition and thermal properties of the Sakharinskoe deposit oxidized nickel ore

X-ray diffraction, optical microscopy and X-ray microanalysis were used to determine the composition and distribution of elements in the main mineral constituents of oxidized nickel ore at the Sakhalin deposit (goethite, hematite, serpentine, talc and chlorite). The main fraction of nickel is concentrated in iron oxides, where its content reaches 2,4 %, while in magnesium silicates it does not exceed 0,4 %. The sequence and temperature intervals of transformations were established when heating ore in inert and reducing media by means of thermal analysis methods combined with mass-spectrometric analysis of gases and subsequent X-ray phase analysis of products. The temperature regimes of ore roasting for the reduction of nickel and iron from their minerals were justified. The temperature regimes of sample heating are assumed to be close to the conditions implemented in industrial units (electric furnaces) where the rate of charge heating varies within 5—15 degrees/min, up to the melting point (1450 °С) of ferronickel and slag. It is proposed to use information on material composition, thermal properties and metal forms in ore to select regimes and technologies for their pyro-or hydrometallurgical processing. Nickel and iron recovery from oxides in CO environment occurs above 800 °С, while serpentines remain stable up to 1200 °С. The use of coke as a reducing agent allows reducing iron and nickel from serpentines at temperatures above 1250 °С. The obtained data were used to substantiate the operating conditions of roaster and electric furnaces during ferronickel smelting from oxidized ores. When roasting, resulting ferronickel particles will contain 2—4 % Ni. Completing recovery processes in the electric furnace will ensure metal recovery from magnesium silicates, which will slightly increase the nickel content in ferro-nickel.

A comparative study of Ti-6Al-4V powders for additive manufacturing by gas atomization, plasma rotating electrode process and plasma atomization

In this study, it is the first time to overall compare three types of spherical Ti-6Al-4V powders by gas atomization, plasma rotating electrode process and plasma atomization in terms of microstructure, porosity, argon gas content and pore spatial structure using scanning electron microscopy, mass spectrometer gas analyzer and synchrotron X-ray computed tomography (CT). It is found that the particle size plays a crucial role in the micro-morphology, porosity and argon gas content of the atomized powders. The experimental results show that the argon content of the gas atomized (GAed), plasma rotating electrode processed (PREPed) and plasma atomized (PAed) powders below 150 μm is 0.77 ± 0.06, 0.16 ± 0.06 and 0.70 ± 0.06 μg/g, while its porosity is 0.20 ± 0.01%, 0.08 ± 0.01% and 0.12 ± 0.01%, respectively. Both argon content and porosity within powders increase with increasing particle size for each type of powders. The results of three-dimensional reconstructed images from CT scanning present that the pore population, size and porosity within powders gradually increase with the increase of particle size. The pore sphericity of the GAed and PAed powders exhibits relatively higher than that of the PREPed powders due to different gas pressures inside of powders.

Selective inhibition of human carbonic anhydrase IX in Xenopus oocytes and MDA-MB-231 breast cancer cells

Human carbonic anhydrase IX (CA IX) is overexpressed in the most aggressive and invasive tumors. Therefore, CA IX has become the promising antitumor drug target. Three inhibitors have been shown to selectively and with picomolar affinity inhibit human recombinant CA IX. Their inhibitory potencies were determined for the CA IX, CA II, CA IV and CA XII in Xenopus oocytes and MDA-MB-231 cancer cells. The inhibition IC50 value of microelectrode-monitored intracellular and extracellular acidification reached 15 nM for CA IX, but with no effect on CA II expressed in Xenopus oocytes. Results were confirmed by mass spectrometric gas analysis of lysed oocytes, when an inhibitory effect on CA IX catalytic activity was found after the injection of 1 nM VD11-4-2. Moreover, VD11-4-2 inhibited CA activity in MDA-MB-231 cancer cells at nanomolar concentrations. This combination of high selectivity and potency renders VD11-4-2, an auspicious therapeutic drug for target-specific tumor therapy.

Vacuum lifetime and residual gas analysis of parabolic trough receiver

The vacuum characteristics and lifetime are the key problems of parabolic trough receiver. Heat loss of the receiver will greatly increase when the vacuum has been lost. Especially, if hydrogen is inside the annulus space of the receiver, heat loss at a level is approximately a factor of four higher than the loss for a receiver with good vacuum. Suitable vacuum levels and residual gases should be maintained in the receiver to ensure performances during its projected lifetime. In this paper, the variations of composition and partial pressure of residual gases with temperature in the receiver were measured by a high sensitivity quadrupole mass spectrometer gas analyzer. The effects of residual gas and getter on the vacuum lifetime of receiver were analyzed. The results showed that hydrogen was the main residual gas in the annular space of receiver without getter, and the nitrogen was the main gas released in the receiver with getter. It can be confirmed that the residual gas analysis was a very effective way to predict and evaluate the vacuum lifetime of the receiver.

Numerical modeling and experimental validation of a universal secondary electrospray ionization source for mass spectrometric gas analysis in real-time

The process by which ambient vapors are ionized upon interaction with electrosprays is not fully understood, compromising its optimization and widespread use. In this work we evaluated the different scales associated with the processes involved in secondary electrospray ionization (SESI), and developed a new numerical method that merges the analytical solution that describes the angle of aperture and the current of an ideal electrospray, with a finite element method that enables the evaluation of complex geometries. The numerical method showed that, despite the low ionization efficiency (i.e. ion concentration/neutral vapor concentration ∼10−4), depletion of neutral vapors plays an important role. We used this method to optimize and design a low flow SESI source, which was coupled with a commercial high resolution/high mass accuracy mass spectrometer. The system was designed to be interfaced with virtually any pre-existing atmospheric pressure ionization mass spectrometer. The experimental validation for the detection of ambient vapors confirmed qualitatively the numerical predictions in terms of ionization efficiency as a function of sample flow rate. As a result of the optimization, this prototype showed a 5-fold sensitivity increase against standard SESI. This novel add-on is meant to upgrade mass spectrometers to analyze trace gases in real time by SESI technique.

Gasification Reactivity and Mass Spectrometric Analysis of Gases of Energy Crop Chars under a CO2 Atmosphere

Aiming to investigate the possibility of exploitation of perennial crops for energetic uses, five sustainable energy plants, previously devolatilized, were gasified by carbon dioxide up to 950 °C in a thermobalance system, coupled with a quadrupole mass spectrometer. The gasification reactivity, thermal decomposition characteristics, and products of gasification were determined, and the effect of inherent inorganic matter of these fuels on process parameters was examined. The bulk of the gasification process occurred above 800 °C, with main products CO and lesser amounts of H2 and H2O. Gasification reactivity was highly correlated to the specific surface area of the chars. Inherent mineral species K, P, S, and Cl influenced the temperature sensitivity of the process and reduced the gasification rate and H2 production. However, a lower pyrolysis temperature of char generation increased the gasification reactivity and greatly enhanced H2 production.

Kinetic studies of heterogeneous reactions of particulate phosmet and parathion with NO3 radicals

Organophosphorous pesticides (OPPs) are ubiquitous pollutants in the atmospheric environment with adverse effects on human health. In this study, heterogeneous kinetics of particulate phosmet and parathion with NO3 radicals were investigated with a mixed-phase relative rate method. A vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) and an atmospheric gas analysis mass spectrometer were used to monitor online the decays of particulate OPPs and reference compound, respectively. Reactive uptake coefficients of NO3 radicals on phosmet and parathion particles were (0.12±0.03) and (0.14±0.04), respectively, calculated according to the measured OPPs loss ratios and the average NO3 concentrations. Additionally, the average effective rate constants for heterogeneous reactions of particulate phosmet and parathion with NO3 radicals measured under experimental conditions were (2.80±0.16)×10−12 and (2.97±0.13)×10−12cm3molecule−1s−1, respectively. The experimental results of these heterogeneous reactions in the aerosol state provide supplementary knowledge for kinetic behaviors of airborne OPPs particles.

Molecular Modeling and Gas Permeation Properties of a Polymer of Intrinsic Microporosity Composed of Ethanoanthracene and Tröger’s Base Units

Polymers of intrinsic microporosity (PIMs) are receiving increasing attention from the membrane community because of their high gas and vapor permeability. Recently a novel ethanoanthracene-based PIM synthesized by Troger’s base formation (PIM-EA-TB) was reported to have exceptional transport properties, behaving as a polymer molecular sieve membrane. In the present work, an extensive investigation of the structural, mechanical, and transport properties of this polymer, both by experimental analysis and by molecular simulation, offers deep insight into the behavior of this polymer and gives an explanation for its remarkable performance as a membrane material. Transport properties were determined by the barometric time-lag method, by the volumetric method with gas chromatographic or mass spectrometric gas analysis, and by gravimetric sorption measurements, yielding all basic transport parameters, permeability (P), diffusivity (D), and solubility (S). Upon alcohol treatment, PIM-EA-TB exhibited a much stron...

Products and kinetics of the heterogeneous reaction of particulate ametryn with NO3 radicals.

As a renowned s-triazine herbicide, ametryn is worldwide emitted into the atmosphere in both gaseous and particulate phases via spray drifts from treatments and post application emissions, but its chemical degradation in the atmosphere has not been well characterized. In this study, the heterogeneous kinetics of particulate ametryn with NO3 radicals were investigated with a mixed-phase relative rate method. A vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) and an atmospheric gas analysis mass spectrometer were synchronously used to online monitor the decays of particulate ametryn and gas-phase isoprene. The reactive uptake coefficient of NO3 radicals on ametryn particles was calculated to be 2.9 × 10(-2), according to the measured ametryn loss ratio and the average NO3 concentration. The effective rate constant for the heterogeneous reaction of particulate ametryn with NO3 radicals measured under experimental conditions was 8.4 × 10(-13) cm(3) molecule(-1) s(-1). In addition, atraton, ametryn sulfoxide and ametryn sulfone were identified as the reaction products by gas-chromatography-mass spectrometry (GC-MS) analysis. The experimental results might shed light on the chemical behavior of atmospheric ametryn at night-time.

Heterogeneous reaction of particulate chlorpyrifos with NO3 radicals: Products, pathways, and kinetics

Chlorpyrifos is a typical chlorinated organophosphorus pesticide. The heterogeneous reaction of chlorpyrifos particles with NO3 radicals was investigated using a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) and a real-time atmospheric gas analysis mass spectrometer. Chlorpyrifos oxon, 3,5,6-trichloro-2-pyridinol, O,O-diethyl O-hydrogen phosphorothioate, O,O-diethyl ester thiophosphoric acid, diethyl hydrogen phosphate and a phosphinyl disulfide compound were identified as the main degradation products. The heterogeneous reaction pathways were proposed and their kinetic processes were investigated via a mixed-phase relative rate method. The observed effective rate constant is 3.4±0.2×10−12cm3molecule−1s−1.

Heterogeneous reactions of particulate benzo[b]fluoranthene and benzo[k]fluoranthene with NO3 radicals

Benzo[b]fluoranthene (B[b]F) and benzo[k]fluoranthene (B[k]F) are widespread priority pollutants of polycyclic aromatic hydrocarbons (PAHs), which can react with atmospheric oxidants during transport in the troposphere and lead to the formation of more toxic compounds. At present, the rates of heterogeneous reactions of B[b]F and B[k]F aerosols with NO3 radicals, an important atmospheric oxidant, are not fully understood. Thus, this study investigated the products and kinetics of heterogeneous reactions of suspended B[b]F and B[k]F particles with NO3 radicals in an aerosol reaction chamber at room temperature (293±2K) under atmospheric pressure. The reactions are monitored online using a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) and an atmospheric gas analysis mass spectrometer. The mono-nitro-, di-nitro-, tri-nitro-products, and those products containing both nitro and ketone groups are observed with VUV-ATOFMS. The effective rate constants for heterogeneous reactions of particulate B[b]F and B[k]F with NO3 radicals under the experimental conditions are respectively estimated to (1.2±0.1)×10−12cm3molecule−1s−1 and (5.8±0.3)×10−13cm3molecule−1s−1 using a mixed-phase relative rate method, and the corresponding effective uptake coefficients are respectively estimated to 0.22 and 0.65. The lifetimes of particulate B[b]F and B[k]F at a typical concentration of NO3 radicals (5×108moleculecm−3) in the lower troposphere during the night are estimated to 3.0 and 3.9h, respectively. The experimental results of these heterogeneous reactions in the aerosol state provide supplementary knowledge for kinetic behaviors of airborne PAHs particles.

Formation of energetic heavy ion tracks in polyimide thin films

Polyimide thin films have been irradiated with a high energy beam of heavy ions to a fluence of approximately 4×1013ions/cm2. Proton backscattering spectroscopy was used to measure the composition of the films, which showed that oxygen was the element that exhibited the most rapid loss from the film. The gases evolved from the film during polymer modification were monitored using a quadrupole mass spectrometer for residual gas analysis (RGA). The fluence dependence of RGA signals were indicative of multi-step processes of gas release, whereby the passage of an ion through a region of pristine film changes the local molecular structure to one that will more readily form volatile species when subsequent ions pass.

Heterogeneous Reactions of Particulate Methoxyphenols with NO3 Radicals: Kinetics, Products, and Mechanisms

Methoxyphenols, tracers for wood smoke, are emitted into the atmosphere in large quantities, but their chemical degradation in the atmosphere has not been well characterized. In this study, heterogeneous kinetics of particulate syringaldehyde (SA), vanillic acid (VA), and coniferyl aldehyde (CA) with NO₃ radicals is investigated with a mixed-phase relative rate method. A vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer and an atmospheric gas analysis mass spectrometer are used to monitor online the decays of particulate methoxyphenols and gas-phase isoprene synchronously. The reactive uptake coefficients of NO₃ radicals on SA, VA, and CA particles are calculated to be 0.33, 0.31, and 0.28, respectively, according to the measured methoxyphenol loss ratios and the average NO₃ concentrations. The effective rate constants for heterogeneous reactions of particulate SA, VA, and CA with NO₃ radicals measured under experimental conditions are 5.7 × 10⁻¹², 5.2 × 10⁻¹², and 3.5 × 10⁻¹² cm³ molecule⁻¹ s⁻¹, respectively. In addition, oxalic acid, 2,6-dimethoxybenzoquinone, 5-nitro-VA, 4,6-dinitrogaiacol, protocatechuic acid, vanillin, 5-nitrovanillin, VA, and 5-nitro-CA are identified as the reaction products by gas chromatography-mass spectrometry analysis. On the basis of the identified products, the reaction mechanisms of methoxyphenols with NO₃ radicals are proposed. The main transformation pathway of methoxyphenols is the NO₃ electrophilic addition, followed by H-abstraction and nitro-substituted processes. The experimental results might shed light on the chemical behaviors of methoxyphenols at night.

Heterogeneous Reactions of Pirimiphos-Methyl and Pirimicarb with NO3 Radicals

Pirimiphos-methyl (PMM) and pirimicarb (PM) are two typical N,N-dialkyl substituted pyrimidine pesticides. The heterogeneous reactions of suspended PMM and PM particles with NO(3) radicals are investigated using an online aerosol time-of-flight mass spectrometer and a real-time atmospheric gas analysis mass spectrometer. Three products for PMM and five products for PM are observed and assigned with the aid of GC/MS. Phosphoric acid 2-diethylamino-6-methyl-4-pyrimidinyl dimethyl ester and 2-(dimethylamino)-5,6-dimethyl-4-hydroxy-pyrimidine are the main reaction products observed for PMM and PM, respectively. The effective rate constants for the reactions of PMM and PM particles with NO(3) radicals are (9.9 ± 0.3) × 10(-12) and (7.5 ± 0.3) × 10(-13) cm(3) molecule(-1) s(-1), respectively, obtained using a mixed-phase relative rate method. Geometries and energies of transition states (TS) and intermediates (IM) are obtained by DFT calculation to elucidate the detailed mechanism of the P═S group oxidation into the P═O group for PMM. The theoretical studies present the reasonable intermediates including the S-oxide and the diradical (IM1(a) and IM2(a)). The mechanism explanation may provide useful information for understanding the degradation mechanism of organothionophosphorus compounds in the environment.