The Experts below are selected from a list of 3180 Experts worldwide ranked by ideXlab platform
Tiina J Kauppila - One of the best experts on this subject based on the ideXlab platform.
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recent developments in atmospheric pressure Photoionization Mass Spectrometry
Mass Spectrometry Reviews, 2017Co-Authors: Tiina J Kauppila, Jack A Syage, Thorsten BenterAbstract:Recent developments in atmospheric pressure Photoionization (APPI), which is one of the three most important ionization techniques in liquid chromatography-Mass Spectrometry, are reviewed. The emphasis is on the practical aspects of APPI analysis, its combination with different separation techniques, novel instrumental developments - especially in gas chromatography and ambient Mass Spectrometry - and the applications that have appeared in 2009-2014. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:423-449, 2017.
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analysis of nitrogen based explosives with desorption atmospheric pressure Photoionization Mass Spectrometry
Rapid Communications in Mass Spectrometry, 2016Co-Authors: Tiina J Kauppila, Anu Flink, J Pukkila, Raimo A KetolaAbstract:Rationale Fast methods that allow the in situ analysis of explosives from a variety of surfaces are needed in crime scene investigations and home-land security. Here, the feasibility of the ambient Mass Spectrometry technique desorption atmospheric pressure Photoionization (DAPPI) in the analysis of the most common nitrogen-based explosives is studied. Methods DAPPI and desorption electrospray ionization (DESI) were compared in the direct analysis of trinitrotoluene (TNT), trinitrophenol (picric acid), octogen (HMX), cyclonite (RDX), pentaerythritol tetranitrate (PETN), and nitroglycerin (NG). The effect of different additives in DAPPI dopant and in DESI spray solvent on the ionization efficiency was tested, as well as the suitability of DAPPI to detect explosives from a variety of surfaces. Results The analytes showed ions only in negative ion mode. With negative DAPPI, TNT and picric acid formed deprotonated molecules with all dopant systems, while RDX, HMX, PETN and NG were ionized by adduct formation. The formation of adducts was enhanced by addition of chloroform, formic acid, acetic acid or nitric acid to the DAPPI dopant. DAPPI was more sensitive than DESI for TNT, while DESI was more sensitive for HMX and picric acid. Conclusions DAPPI could become an important method for the direct analysis of nitroaromatics from a variety of surfaces. For compounds that are thermally labile, or that have very low vapor pressure, however, DESI is better suited. Copyright © 2016 John Wiley & Sons, Ltd.
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laser ablation atmospheric pressure Photoionization Mass Spectrometry imaging of phytochemicals from sage leaves
Rapid Communications in Mass Spectrometry, 2014Co-Authors: Anu Vaikkinen, Risto Kostiainen, Bindesh Shrestha, Akos Vertes, Juha Koivisto, Tiina J KauppilaAbstract:RATIONALE Despite fast advances in ambient Mass Spectrometry imaging (MSI), the study of neutral and nonpolar compounds directly from biological matrices remains challenging. In this contribution, we explore the feasibility of laser ablation atmospheric pressure Photoionization (LAAPPI) for MSI of phytochemicals in sage (Salvia officinalis) leaves. METHODS Sage leaves were studied by LAAPPI-time-of-flight (TOF)-MSI without any sample preparation. Leaf Mass spectra were also recorded with laser ablation electrospray ionization (LAESI) Mass Spectrometry and the spectra were compared with those obtained by LAAPPI. RESULTS Direct probing of the plant tissue by LAAPPI efficiently produced ions from plant metabolites, including neutral and nonpolar terpenes that do not have polar functional groups, as well as oxygenated terpene derivatives. Monoterpenes and monoterpenoids could also be studied from sage by LAESI, but only LAAPPI was able to detect larger nonpolar compounds, such as sesquiterpenes and triterpenoid derivatives, from the leaf matrix. Alternative MSI methods for nonpolar compounds, such as desorption atmospheric pressure Photoionization (DAPPI), do not achieve as good spatial resolution as LAAPPI (<400 µm). CONCLUSIONS We show that MSI with LAAPPI is a useful tool for concurrently studying the distribution of polar and nonpolar compounds, such as phytochemicals, directly from complex biological samples, and it can provide information that is not available by other, established methods. Copyright © 2014 John Wiley & Sons, Ltd.
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infrared laser ablation atmospheric pressure Photoionization Mass Spectrometry
Analytical Chemistry, 2012Co-Authors: Anu Vaikkinen, Tiina J Kauppila, Bindesh Shrestha, Akos Vertes, Risto KostiainenAbstract:In this paper we introduce laser ablation atmo- spheric pressure Photoionization (LAAPPI), a novel atmospheric pressure ion source for Mass Spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 μm wave- length. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the Mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure Photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ∼300 μm lateral resolution comparable to, e.g., matrix- assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves.
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matrix effect in the analysis of drugs of abuse from urine with desorption atmospheric pressure Photoionization Mass Spectrometry dappi ms and desorption electrospray ionization Mass Spectrometry desi ms
Analytica Chimica Acta, 2011Co-Authors: Niina Suni, Tiina J Kauppila, Tapio Kotiaho, Pia Lindfors, Olli Laine, Pekka Ostman, Ilkka Ojanpera, Risto KostiainenAbstract:Abstract We have studied the matrix effect within direct analysis of benzodiazepines and opioids from urine with desorption electrospray ionization-Mass Spectrometry (DESI-MS) and desorption atmospheric pressure Photoionization-Mass Spectrometry (DAPPI-MS). The urine matrix was found to affect the ionization mechanism of the opioids in DAPPI-MS favoring proton transfer over charge exchange reaction. The sensitivity for the drugs in solvent matrix was at the same level with DESI-MS and DAPPI-MS (LODs 0.05–6 μg mL−1) but the decrease in sensitivity due to the urine matrix was higher with DESI (typically 20–160-fold) than with DAPPI (typically 2–15-fold) indicating better matrix tolerance of DAPPI over DESI. Also in MS/MS mode, DAPPI provided better sensitivity than DESI for the drugs in urine. The feasibility of DAPPI-MS/MS was then studied in screening the same drugs from five authentic, forensic post mortem urine samples. A reference measurement with gas chromatography-Mass Spectrometry (GC–MS) (including pretreatment) revealed 16 findings from the samples, whereas with DAPPI-MS/MS after sample pretreatment, 15 findings were made. Sample pretreatment was found necessary, since only eight findings were made from the same samples untreated.
Risto Kostiainen - One of the best experts on this subject based on the ideXlab platform.
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laser ablation atmospheric pressure Photoionization Mass Spectrometry imaging of phytochemicals from sage leaves
Rapid Communications in Mass Spectrometry, 2014Co-Authors: Anu Vaikkinen, Risto Kostiainen, Bindesh Shrestha, Akos Vertes, Juha Koivisto, Tiina J KauppilaAbstract:RATIONALE Despite fast advances in ambient Mass Spectrometry imaging (MSI), the study of neutral and nonpolar compounds directly from biological matrices remains challenging. In this contribution, we explore the feasibility of laser ablation atmospheric pressure Photoionization (LAAPPI) for MSI of phytochemicals in sage (Salvia officinalis) leaves. METHODS Sage leaves were studied by LAAPPI-time-of-flight (TOF)-MSI without any sample preparation. Leaf Mass spectra were also recorded with laser ablation electrospray ionization (LAESI) Mass Spectrometry and the spectra were compared with those obtained by LAAPPI. RESULTS Direct probing of the plant tissue by LAAPPI efficiently produced ions from plant metabolites, including neutral and nonpolar terpenes that do not have polar functional groups, as well as oxygenated terpene derivatives. Monoterpenes and monoterpenoids could also be studied from sage by LAESI, but only LAAPPI was able to detect larger nonpolar compounds, such as sesquiterpenes and triterpenoid derivatives, from the leaf matrix. Alternative MSI methods for nonpolar compounds, such as desorption atmospheric pressure Photoionization (DAPPI), do not achieve as good spatial resolution as LAAPPI (<400 µm). CONCLUSIONS We show that MSI with LAAPPI is a useful tool for concurrently studying the distribution of polar and nonpolar compounds, such as phytochemicals, directly from complex biological samples, and it can provide information that is not available by other, established methods. Copyright © 2014 John Wiley & Sons, Ltd.
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infrared laser ablation atmospheric pressure Photoionization Mass Spectrometry
Analytical Chemistry, 2012Co-Authors: Anu Vaikkinen, Tiina J Kauppila, Bindesh Shrestha, Akos Vertes, Risto KostiainenAbstract:In this paper we introduce laser ablation atmo- spheric pressure Photoionization (LAAPPI), a novel atmospheric pressure ion source for Mass Spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 μm wave- length. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the Mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure Photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ∼300 μm lateral resolution comparable to, e.g., matrix- assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves.
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matrix effect in the analysis of drugs of abuse from urine with desorption atmospheric pressure Photoionization Mass Spectrometry dappi ms and desorption electrospray ionization Mass Spectrometry desi ms
Analytica Chimica Acta, 2011Co-Authors: Niina Suni, Tiina J Kauppila, Tapio Kotiaho, Pia Lindfors, Olli Laine, Pekka Ostman, Ilkka Ojanpera, Risto KostiainenAbstract:Abstract We have studied the matrix effect within direct analysis of benzodiazepines and opioids from urine with desorption electrospray ionization-Mass Spectrometry (DESI-MS) and desorption atmospheric pressure Photoionization-Mass Spectrometry (DAPPI-MS). The urine matrix was found to affect the ionization mechanism of the opioids in DAPPI-MS favoring proton transfer over charge exchange reaction. The sensitivity for the drugs in solvent matrix was at the same level with DESI-MS and DAPPI-MS (LODs 0.05–6 μg mL−1) but the decrease in sensitivity due to the urine matrix was higher with DESI (typically 20–160-fold) than with DAPPI (typically 2–15-fold) indicating better matrix tolerance of DAPPI over DESI. Also in MS/MS mode, DAPPI provided better sensitivity than DESI for the drugs in urine. The feasibility of DAPPI-MS/MS was then studied in screening the same drugs from five authentic, forensic post mortem urine samples. A reference measurement with gas chromatography-Mass Spectrometry (GC–MS) (including pretreatment) revealed 16 findings from the samples, whereas with DAPPI-MS/MS after sample pretreatment, 15 findings were made. Sample pretreatment was found necessary, since only eight findings were made from the same samples untreated.
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desorption atmospheric pressure Photoionization Mass Spectrometry in routine analysis of confiscated drugs
Forensic Science International, 2011Co-Authors: Tiina J Kauppila, Anu Flink, Raimo A Ketola, Markus Haapala, Ullamaija Laakkonen, Laura Aalberg, Risto KostiainenAbstract:Abstract A comprehensive study was made, where desorption atmospheric pressure Photoionization (DAPPI) was applied to the direct analysis of confiscated drugs and pharmaceuticals of various forms and matrices. The analyzed samples included herbal products [ Catha edulis (khat), Psilocybe mushrooms, opium and Spice], designer drugs in tablet and powder form [e.g. meta -chlorophenylpiperazine (mCPP), 3-fluoromethamphetamine (3-FMA), methylenedioxypyrovalerone (MDPV) and methylone], and anabolic steroids in oil and tablets. The analyses were performed with ion trap Mass spectrometer in MS and MS 2 modes and the obtained spectra were compared with GC–MS results. Contamination of the Mass spectrometer was avoided by careful adjustment of the distance of the sample from the Mass spectrometer inlet. DAPPI proved to be a fast and specific analysis technique, which does not require any sample preparation, and which therefore suits well to this type of forensic analysis.
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environmental and food analysis by desorption atmospheric pressure Photoionization Mass Spectrometry
Rapid Communications in Mass Spectrometry, 2010Co-Authors: Laura Luosujarvi, Risto Kostiainen, Tapio Kotiaho, Sanna Kanerva, Ville Saarela, Sami Franssila, Tiina J KauppilaAbstract:Desorption atmospheric pressure Photoionization-Mass Spectrometry (DAPPI-MS) is a versatile surface analysis technique for a wide range of analytes, especially for neutral and non-polar analytes. Here, a set of analytes typically found in environmental or food samples was analyzed by DAPPI-MS. The set included five polyaromatic hydrocarbons (PAHs), one N-PAH, one brominated flame retardant, and nine pesticides, which were studied with three different spray solvents: acetone and toluene in positive ion mode, and anisole in negative ion mode. The analytes showed [M + H] + , M +• , and [M―H] ― ions as well as fragmentation and substitution products. Detection limits for the studied compounds ranged from 30 pg to 1 ng (from 0.14 to 5.6 pmol). To demonstrate the feasibility of the use of DAPPI-MS two authentic samples - a circuit board and orange peel ― and a spiked soil sample were analyzed. Tetrabromobisphenol A, imazalil, and PAHs were observed from the three above-mentioned samples, respectively. The method is best suited for rapid screening analysis of environmental or food samples.
Yang Pan - One of the best experts on this subject based on the ideXlab platform.
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benzene decomposition by non thermal plasma a detailed mechanism study by synchrotron radiation Photoionization Mass Spectrometry and theoretical calculations
Journal of Hazardous Materials, 2021Co-Authors: Yuting Liang, Jiuzhong Yang, Yingying Xue, Ting Tan, Zhi Jiang, Wenfeng Shangguan, Yang PanAbstract:Non-thermal Plasma (NTP) catalysis is considered as one of the most promising technologies to address a wide range of environmental needs, such as volatile organic compounds (VOCs) and NOx removal. To meet the updated environmental emission standard, the NTP catalysis reaction system needs to be better understood and further optimized. In this work, the degradation process of benzene in NTP, which is still regarded as a "black box" process, was explored by synchrotron vacuum ultraviolet Photoionization Mass Spectrometry (SVUV-PIMS). For the first time, we observed over 20 representative species by PIMS and identified their structures accurately by Photoionization efficiency (PIE) spectra. Phenol, acetylene and acrolein were recognized as the three main products. More intriguingly, concentration profiles demonstrated that a large amount of acrolein and also several higher-order products, which were usually neglected in previous research, were produced during the NTP destruction process. The details of the benzene degradation reaction mechanism, were finally established by the combination of SVUV-PIMS results, thermochemistry and theoretical calculations. This work helps to complete the mechanistic picture of plasma chemistry, which may be helpful on raveling the more complicated NTP catalysis mechanism in the future therefore contributing to design of improved NTP system for environmental applications.
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online study on the co pyrolysis of coal and corn with vacuum ultraviolet Photoionization Mass Spectrometry
Bioresource Technology, 2017Co-Authors: Junjie Weng, Yanan Zhu, Yang Pan, Yuexi Liu, Zhenyu TianAbstract:Abstract With the aim to support the experimental tests in a circulating fluidized bed pilot plant, the pyrolysis processes of coal, corn, and coal-corn blend have been studied with an online pyrolysis Photoionization time-of-flight Mass Spectrometry (Py–PI–TOFMS). The Mass spectra at different temperatures (300–800 °C) as well as time-evolved profiles of selected species were measured. The pyrolysis products such as alkanes, alkenes, phenols, aromatics, as well as nitrogen- and sulfur-containing species were detected. As temperature rises, the relative ion intensities of high molecular weight products tend to decrease, while those of aromatics increase significantly. During the co-pyrolysis, coal can promote the reaction temperature of cellulose in corn. Time-evolved profiles demonstrate that coal can affect pyrolysis rate of cellulose, hemicellulose, and lignin of corn in blend. This work shows that Py–PI–TOFMS is a powerful approach to permit a better understanding of the mechanisms underlying the co-pyrolysis of coal and bioMass.
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pyrolysis mechanism study of lignin model compounds by synchrotron vacuum ultraviolet Photoionization Mass Spectrometry
Energy & Fuels, 2016Co-Authors: Yimeng Zhang, Yanan Zhu, Wu Wen, Yang PanAbstract:To investigate the lignin pyrolysis mechanism, two α-O-4 and one completely substituted β-O-4 lignin dimeric model compounds were studied using in situ synchrotron vacuum ultraviolet Photoionization time-of-flight Mass Spectrometry (SVUV PIMS) at 350–500 °C. The collision-reduced vacuum condition, in situ characteristic, and “soft” ionization technique of this reactor system allowed for the direct detection of thermolysis radicals and high-boiling-point compounds. For the α-O-4 compound 4-(benzyloxy)phenol (BOP) pyrolysis, benzyl radical, p-semiquinone radical, toluene, and bibenzyl were confirmed, supplying firm evidence for the free radical dominant mechanism. Experiments of the p-methoxy substituent on the hydroxyl position of BOP show that the p-methoxy substituent can lower the Caromatic–Cα and Oether–Caromatic bond dissociation energies. For β-O-4 compound guaiacylglycerol-β-guaiacyl ether (GGGE), it is inferred that the C–O homolysis mechanism was minor and the concerted reaction dominated in the e...
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pyrolysis study on solid fuels from conventional analytical methods to synchrotron vacuum ultraviolet Photoionization Mass Spectrometry
Energy & Fuels, 2016Co-Authors: Yu Wang, Jiuzhong Yang, Yanan Zhu, Zhongyue Zhou, Yang PanAbstract:The demand of modern society for energy keeps increasing as a result of the rapid growth of population and urbanization. Pyrolysis of solid fuels, including bioMass, coal, and polymer waste, has recently received special attention because it can provide extra sources of fuels. In the past few years, a variety of analytical techniques have been used to detect the pyrolysis products of solid fuels, such as gas chromatography/Mass Spectrometry, thermogravimetry, Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, etc. However, online detection of gas release during the pyrolysis process, which is believed to be closely related to the thermal decomposition mechanisms of solid fuels, is rare. Recently, some progress has been made in real-time diagnostic techniques, the most important one of which is Photoionization Mass Spectrometry (PIMS). This review focuses on recent developments in the pyrolysis study of solid fuels, especially on those performed with synchrot...
John D Savee - One of the best experts on this subject based on the ideXlab platform.
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direct measurements of unimolecular and bimolecular reaction kinetics of the criegee intermediate ch3 2coo
Journal of Physical Chemistry A, 2017Co-Authors: Rabi Chhantyalpun, John D Savee, Lucy Blacker, Henry R Hill, Matilda Ashcroft, Anwar M H Khan, Oliver Welz, Arkke J. Eskola, Edmond P F Lee, Guy C LloydjonesAbstract:The Criegee intermediate acetone oxide, (CH3)2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O2 and characterized by synchrotron Photoionization Mass Spectrometry and by cavity ring-down ultraviolet absorption spectroscopy. The rate coefficient of the reaction of the Criegee intermediate with SO2 was measured using Photoionization Mass Spectrometry and pseudo-first-order methods to be (7.3 ± 0.5) × 10-11 cm3 s-1 at 298 K and 4 Torr and (1.5 ± 0.5) × 10-10 cm3 s-1 at 298 K and 10 Torr (He buffer). These values are similar to directly measured rate coefficients of anti-CH3CHOO with SO2, and in good agreement with recent UV absorption measurements. The measurement of this reaction at 293 K and slightly higher pressures (between 10 and 100 Torr) in N2 from cavity ring-down decay of the ultraviolet absorption of (CH3)2COO yielded even larger rate coefficients, in the range (1.84 ± 0.12) × 10-10 to (2.29 ± 0.08) × 10-10 cm3 s-1. Photoionization Mass Spectrometry measurements with deuterated acetone oxide at 4 Torr show an inverse deuterium kinetic isotope effect, kH/kD = (0.53 ± 0.06), for reactions with SO2, which may be consistent with recent suggestions that the formation of an association complex affects the rate coefficient. The reaction of (CD3)2COO with NO2 has a rate coefficient at 298 K and 4 Torr of (2.1 ± 0.5) × 10-12 cm3 s-1 (measured with Photoionization Mass Spectrometry), again similar to rate for the reaction of anti-CH3CHOO with NO2. Cavity ring-down measurements of the acetone oxide removal without added reagents display a combination of first- and second-order decay kinetics, which can be deconvolved to derive values for both the self-reaction of (CH3)2COO and its unimolecular thermal decay. The inferred unimolecular decay rate coefficient at 293 K, (305 ± 70) s-1, is similar to determinations from ozonolysis. The present measurements confirm the large rate coefficient for reaction of (CH3)2COO with SO2 and the small rate coefficient for its reaction with water. Product measurements of the reactions of (CH3)2COO with NO2 and with SO2 suggest that these reactions may facilitate isomerization to 2-hydroperoxypropene, possibly by subsequent reactions of association products.
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direct measurements of unimolecular and bimolecular reaction kinetics of the criegee intermediate ch3 2coo
Journal of Physical Chemistry A, 2017Co-Authors: Rabi Chhantyalpun, John D Savee, Lucy Blacker, Henry R Hill, Matilda Ashcroft, Anwar M H Khan, Guy C Lloydjones, Oliver Welz, Arkke J. Eskola, Louise A EvansAbstract:The Criegee intermediate acetone oxide, (CH3)2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O2 and characterized by synchrotron Photoionization Mass Spectrometry and by cavity ring-down ultraviolet absorption spectroscopy. The rate coefficient of the reaction of the Criegee intermediate with SO2 was measured using Photoionization Mass Spectrometry and pseudo-first-order methods to be (7.3 ± 0.5) × 10–11 cm3 s–1 at 298 K and 4 Torr and (1.5 ± 0.5) × 10–10 cm3 s–1 at 298 K and 10 Torr (He buffer). These values are similar to directly measured rate coefficients of anti-CH3CHOO with SO2, and in good agreement with recent UV absorption measurements. The measurement of this reaction at 293 K and slightly higher pressures (between 10 and 100 Torr) in N2 from cavity ring-down decay of the ultraviolet absorption of (CH3)2COO yielded even larger rate coefficients, in the range (1.84 ± 0.12) × 10–10 to (2.29 ± 0.08) × 10–10 cm3 s–1. Photoionization Mass Spectrometry measurements with deu...
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new insights into low temperature oxidation of propane from synchrotron Photoionization Mass Spectrometry and multiscale informatics modeling
Journal of Physical Chemistry A, 2015Co-Authors: Oliver Welz, John D Savee, David L. Osborn, Stephen J Klippenstein, Craig A Taatjes, Michael P Burke, Ivan O Antonov, Franklin C Goldsmith, Leonid ShepsAbstract:Low-temperature propane oxidation was studied at P = 4 Torr and T = 530, 600, and 670 K by time-resolved multiplexed Photoionization Mass Spectrometry (MPIMS), which probes the reactants, intermediates, and products with isomeric selectivity using tunable synchrotron vacuum UV ionizing radiation. The oxidation is initiated by pulsed laser photolysis of oxalyl chloride, (COCl)2, at 248 nm, which rapidly generates a ∼1:1 mixture of 1-propyl (n-propyl) and 2-propyl (i-propyl) radicals via the fast Cl + propane reaction. At all three temperatures, the major stable product species is propene, formed in the propyl + O2 reactions by direct HO2 elimination from both n- and i-propyl peroxy radicals. The experimentally derived propene yields relative to the initial concentration of Cl atoms are (20 ± 4)% at 530 K, (55 ± 11)% at 600 K, and (86 ± 17)% at 670 K at a reaction time of 20 ms. The lower yield of propene at low temperature reflects substantial formation of propyl peroxy radicals, which do not completely de...
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Multiplexed Photoionization Mass Spectrometry Investigation of the O(3P) + Propyne Reaction
2015Co-Authors: John D Savee, Oliver Welz, Craig A Taatjes, Sampada Borkar, Bálint Sztáray, David L. OsbornAbstract:The reaction of O(3P) + propyne (C3H4) was investigated at 298 K and 4 Torr using time-resolved multiplexed Photoionization Mass Spectrometry and a synchrotron-generated tunable vacuum ultraviolet light source. The time-resolved Mass spectra of the observed products suggest five major channels under our conditions: C2H3 + HCO, CH3 + HCCO, H + CH3CCO, C2H4 + CO, and C2H2 + H2 + CO. The relative branching ratios for these channels were found to be 1.00, (0.35 ± 0.11), (0.18 ± 0.10), (0.73 ± 0.27), and (1.31 ± 0.62). In addition, we observed signals consistent with minor production of C3H3 + OH and H2 + CH2CCO, although we cannot conclusively assign them as direct product channels from O(3P) + propyne. The direct abstraction mechanism plays only a minor role (≤1%), and we estimate that O(3P) addition to the central carbon of propyne accounts for 10% of products, with addition to the terminal carbon accounting for the remaining 89%. The isotopologues observed in experiments using d1-propyne (CH3CCD) and analysis of product branching in light of previously computed stationary points on the singlet and triplet potential energy surfaces (PESs) relevant to O(3P) + propyne suggest that, under our conditions, (84 ± 14)% of the observed product channels from O(3P) + propyne result from intersystem crossing from the initial triplet PES to the lower-lying singlet PES
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rate coefficients of c1 and c2 criegee intermediate reactions with formic and acetic acid near the collision limit direct kinetics measurements and atmospheric implications
Angewandte Chemie, 2014Co-Authors: Oliver Welz, John D Savee, David L. Osborn, Arkke J. Eskola, Leonid Sheps, Brandon Rotavera, Adam M Scheer, Douglas Lowe, Murray A Booth, Ping XiaoAbstract:Rate coefficients are directly determined for the reactions of the Criegee intermediates (CI) CH2OO and CH3CHOO with the two simplest carboxylic acids, formic acid (HCOOH) and acetic acid (CH3COOH), employing two complementary techniques: multiplexed Photoionization Mass Spectrometry and cavity-enhanced broadband ultraviolet absorption spectroscopy. The measured rate coefficients are in excess of 1×10−10 cm3 s−1, several orders of magnitude larger than those suggested from many previous alkene ozonolysis experiments and assumed in atmospheric modeling studies. These results suggest that the reaction with carboxylic acids is a substantially more important loss process for CIs than is presently assumed. Implementing these rate coefficients in global atmospheric models shows that reactions between CI and organic acids make a substantial contribution to removal of these acids in terrestrial equatorial areas and in other regions where high CI concentrations occur such as high northern latitudes, and implies that sources of acids in these areas are larger than previously recognized.
Jiuzhong Yang - One of the best experts on this subject based on the ideXlab platform.
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benzene decomposition by non thermal plasma a detailed mechanism study by synchrotron radiation Photoionization Mass Spectrometry and theoretical calculations
Journal of Hazardous Materials, 2021Co-Authors: Yuting Liang, Jiuzhong Yang, Yingying Xue, Ting Tan, Zhi Jiang, Wenfeng Shangguan, Yang PanAbstract:Non-thermal Plasma (NTP) catalysis is considered as one of the most promising technologies to address a wide range of environmental needs, such as volatile organic compounds (VOCs) and NOx removal. To meet the updated environmental emission standard, the NTP catalysis reaction system needs to be better understood and further optimized. In this work, the degradation process of benzene in NTP, which is still regarded as a "black box" process, was explored by synchrotron vacuum ultraviolet Photoionization Mass Spectrometry (SVUV-PIMS). For the first time, we observed over 20 representative species by PIMS and identified their structures accurately by Photoionization efficiency (PIE) spectra. Phenol, acetylene and acrolein were recognized as the three main products. More intriguingly, concentration profiles demonstrated that a large amount of acrolein and also several higher-order products, which were usually neglected in previous research, were produced during the NTP destruction process. The details of the benzene degradation reaction mechanism, were finally established by the combination of SVUV-PIMS results, thermochemistry and theoretical calculations. This work helps to complete the mechanistic picture of plasma chemistry, which may be helpful on raveling the more complicated NTP catalysis mechanism in the future therefore contributing to design of improved NTP system for environmental applications.
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new insights into propanal oxidation at low temperatures an experimental and kinetic modeling study
Proceedings of the Combustion Institute, 2019Co-Authors: Xiaoyuan Zhang, Yuyang Li, Jiuzhong Yang, Tianyu Li, Wei Li, Yan Zhang, Philippe DagautAbstract:Abstract The kinetics of propanal oxidation was studied in a jet-stirred reactor (JSR) at atmospheric pressure. The investigated temperature range is from 450 to 800 K at two different equivalence ratios (0.35 and 4.0). Thanks to the synchrotron vacuum ultraviolet Photoionization Mass Spectrometry (SVUV-PIMS), critical intermediates were identified, including methylperoxy, methyl hydroperoxide, ethylperoxy, ethyl hydroperoxide, α-lactone, β-propiolactone and ketohydroperoxides. A kinetic model for propanal oxidation was also developed and validated against the present experimental results, as well as those available from the literature. Main chain-branching pathways under the investigated conditions were analyzed based on present experimental data and kinetic model. The O2 addition reaction to the propanoyl radical and subsequent oxidation reactions play an important role in determining the oxidation rate of propanal under fuel-lean conditions, especially in the low-temperature oxidation region. Under fuel-rich conditions, the decomposition of the propanoyl radical is predominant and C2H5 relevant reactions consequently determine the kinetics of oxidation of propanal.
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Experimental and Kinetic Modeling Studies of Methyl 2‑Furoate Pyrolysis at Atmospheric Pressure
2019Co-Authors: Beibei Yan, Jiuzhong Yang, Yan Zhang, Chuangchuang Cao, Zhanjun Cheng, Lixia Wei, Jinglan Wang, Qinghui Meng, Guanyi ChenAbstract:Methyl 2-furoate (FAME2) pyrolysis was studied experimentally on a flow reactor in the temperature range of 879-1107 K and at the pressure of 760 Torr using synchrotron vacuum ultraviolet Photoionization Mass Spectrometry. Several important intermediates were identified and measured, including the major pyrolysis products (methane, carbon monoxide, acetylene, formaldehyde, carbon dioxide, ketene, and vinyl acetylene) and even isomers of pyrolysis products (propyne, allene, 1,3-butadiene, 1-butyne, fulvene, and benzene). Unimolecular decomposition reactions in the pyrolysis of FAME2 were also studied theoretically at the CBS-QB3 level using the Gaussian procedure. Based on the calculated potential energy surface, a new kinetic model was developed and validated against our pyrolysis experiments. The rate of production and sensitivity analysis revealed that the decomposition reactions of FAME2 are mainly controlled by the unimolecular decomposition reactions, substitution reactions, H-abstraction reactions, and H-addition reactions in FAME2 pyrolysis. The dominant decomposition reaction is the direct release of CH3 from FAME2, which has about 42% contribution to the fuel consumption
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pyrolysis of n butylbenzene at various pressures influence of long side chain structure on alkylbenzene pyrolysis
Energy & Fuels, 2017Co-Authors: Yan Zhang, Jiuzhong Yang, Chuangchuang Cao, Wenhao Yuan, Xiaoyuan Yang, Tzuping Huang, Yinyu LeeAbstract:This work investigates the pyrolysis of n-butylbenzene, which widely exists in transportation fuels and their surrogate mixtures. Both reactive and stable pyrolysis products were comprehensively detected with synchrotron vacuum ultraviolet Photoionization Mass Spectrometry. Their mole fractions versus temperature were also evaluated at 30, 150, and 760 Torr. A kinetic model of n-butylbenzene pyrolysis was developed, and new data were used to validate the model. On the basis of the modeling analysis, the benzylic C–C bond dissociation that forms the benzyl radical and the propyl radical was found to be a key decomposition reaction of n-butylbenzene at all investigated pressures, whereas H abstraction provided increasing contributions with increasing pressure. Compared with small alkylbenzenes, such as toluene and ethylbenzene, n-butylbenzene demonstrates different pyrolysis characteristics and chemistry because of the existence of its long alkyl side chain. n-Butylbenzene has a higher pyrolysis reactivity ...
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experimental and kinetic modeling studies of furan pyrolysis fuel decomposition and aromatic ring formation
Fuel, 2017Co-Authors: Jiuzhong Yang, Lidong Zhang, Zhanjun Cheng, Yaoyao Tan, Lixia Wei, Lili Xing, Yanan Guan, Beibei Yan, Guanyi ChenAbstract:Abstract The pyrolysis of furan was studied from 1100 to 1600 K in a flow reactor at low pressure (30 Torr). Synchrotron vacuum ultraviolet Photoionization Mass Spectrometry (SVUV-PIMS) was used for isomeric identification and mole fraction measurements of the pyrolysis products, especially the free radicals. Specific products were observed and measured for the unimolecular decomposition reactions of furan, such as propyne + CO, acetylene + ketene and propargyl radical, etc. An updated combustion model of furan from Somers model was adopted to simulate the mole fraction profiles of the pyrolysis species measured in this work. Kinetic modeling analysis indicated that the decomposition of furan is mainly controlled by the unimolecular decomposition reactions under the investigated conditions. Based on the experimental results and theoretical simulations, propargyl radical is suggested to be mainly formed from the direct unimolecular decomposition of propyne instead of that of furan. In furan pyrolysis, propargyl and phenyl radicals are the most important precursors of large aromatic species.