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Chen YL, Taatjes CA, Meloni G. Estimate of the C-Cl photoionization cross section and absolute photoionization cross sections of chlorinated organic compounds. Chemphyschem 2024; 25:e202300896. [PMID: 38265931 DOI: 10.1002/cphc.202300896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/16/2024] [Accepted: 01/23/2024] [Indexed: 01/26/2024]
Abstract
Chlorinated organic compounds are prominently used for industrial production, but their vapors and emission byproducts can cause detrimental effects to human health and the environment. To accurately quantify organochlorine compounds, the absolute photoionization cross section of tetrachloroethylene, chlorobenzene, 1,2-dichlorobenzene, and chloroacetone are measured using multiplexed synchrotron photoionization mass spectrometry at the Advanced Light Source at Lawrence Berkeley National Laboratory. These measurements allow for the estimation of the C-Cl photoionization cross section, increasing quantification accuracy of chlorinated emissions for kinetic modeling and pollutant mitigation. CBS-QB3 calculations of adiabatic ionization energies and thermochemical appearance energies are also presented and agree well with the experimental results.
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Affiliation(s)
- Yilan Lori Chen
- Department of Chemistry, University of San Francisco, 94117, San Francisco, CA, USA
| | - Craig A Taatjes
- Combustion Research Facility, Sandia National Laboratories, 94550, Livermore, CA, USA
| | - Giovanni Meloni
- Department of Chemistry, University of San Francisco, 94117, San Francisco, CA, USA
- Department of Biological and Chemical Sciences, New York Institute of Technology, 11568, Old Westbury, NY, USA
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2
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Qian B, Hu Y, Xu M, Yang J, Liu C, Pan Y. Online Exploring the Gaseous Oil Fumes from Oleic Acid Thermal Oxidation by Synchrotron Radiation Photoionization Mass Spectrometry. J Am Soc Mass Spectrom 2023; 34:2680-2690. [PMID: 37983183 DOI: 10.1021/jasms.3c00259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Cooking oil fumes are an intricate and dynamic mixture containing a variety of poisonous and hazardous substances, and their real-time study remains challenging. Based on tunable synchrotron radiation photoionization mass spectrometry (SR-PIMS), isomeric/isobaric compounds in the gaseous oil fumes from oleic acid thermal oxidation were determined in real time and distinguished by photoionization efficiency (PIE) curve simulation combined with multiple linear regression (MLR) analysis. A series of common carcinogens such as formaldehyde, acetaldehyde, acrolein, and several unreported chemicals including diethyl ether and formylcyclohexane were successfully characterized. Moreover, time-resolved profiles of certain components in gaseous oil fumes were monitored for 55 h. Distinct evolutionary processes were observed, indicating the consumption and formation of parent molecules, intermediates, and final products.
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Affiliation(s)
- Bing Qian
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
| | - Yonghua Hu
- Center of Technology, China Tobacco Anhui Industrial Co, Ltd., Hefei, Anhui 230088, P. R. China
| | - Minggao Xu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
| | - Jiuzhong Yang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
| | - Chengyuan Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
| | - Yang Pan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
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Yue H, Zhang C, Lin X, Wen Z, Zhang W, Mostafa S, Luo PL, Zhang Z, Hemberger P, Fittschen C, Tang X. Dimeric Product of Peroxy Radical Self-Reaction Probed with VUV Photoionization Mass Spectrometry and Theoretical Calculations: The Case of C 2H 5OOC 2H 5. Int J Mol Sci 2023; 24:ijms24043731. [PMID: 36835141 PMCID: PMC9965172 DOI: 10.3390/ijms24043731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/06/2023] [Accepted: 02/10/2023] [Indexed: 02/16/2023] Open
Abstract
Organic peroxy radicals (RO2) as key intermediates in tropospheric chemistry exert a controlling influence on the cycling of atmospheric reactive radicals and the production of secondary pollutants, such as ozone and secondary organic aerosols (SOA). Herein, we present a comprehensive study of the self-reaction of ethyl peroxy radicals (C2H5O2) by using advanced vacuum ultraviolet (VUV) photoionization mass spectrometry in combination with theoretical calculations. A VUV discharge lamp in Hefei and synchrotron radiation at the Swiss Light Source (SLS) are employed as the photoionization light sources, combined with a microwave discharge fast flow reactor in Hefei and a laser photolysis reactor at the SLS. The dimeric product, C2H5OOC2H5, as well as other products, CH3CHO, C2H5OH and C2H5O, formed from the self-reaction of C2H5O2 are clearly observed in the photoionization mass spectra. Two kinds of kinetic experiments have been performed in Hefei by either changing the reaction time or the initial concentration of C2H5O2 radicals to confirm the origins of the products and to validate the reaction mechanisms. Based on the fitting of the kinetic data with the theoretically calculated results and the peak area ratios in the photoionization mass spectra, a branching ratio of 10 ± 5% for the pathway leading to the dimeric product C2H5OOC2H5 is measured. In addition, the adiabatic ionization energy (AIE) of C2H5OOC2H5 is determined at 8.75 ± 0.05 eV in the photoionization spectrum with the aid of Franck-Condon calculations and its structure is revealed here for the first time. The potential energy surface of the C2H5O2 self-reaction has also been theoretically calculated with a high-level of theory to understand the reaction processes in detail. This study provides a new insight into the direct measurement of the elusive dimeric product ROOR and demonstrates its non-negligible branching ratio in the self-reaction of small RO2 radicals.
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Affiliation(s)
- Hao Yue
- Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- Science Island Branch, Graduate School, University of Science and Technology of China, Hefei 230026, China
| | - Cuihong Zhang
- Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- Science Island Branch, Graduate School, University of Science and Technology of China, Hefei 230026, China
- Univ. Lille, CNRS, UMR 8522-PC2A–Physicochimie des Processus de Combustion et de I’Atmosphère, F-59000 Lille, France
| | - Xiaoxiao Lin
- Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Zuoying Wen
- Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Weijun Zhang
- Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Sabah Mostafa
- Univ. Lille, CNRS, UMR 8522-PC2A–Physicochimie des Processus de Combustion et de I’Atmosphère, F-59000 Lille, France
| | - Pei-Ling Luo
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Zihao Zhang
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - Christa Fittschen
- Univ. Lille, CNRS, UMR 8522-PC2A–Physicochimie des Processus de Combustion et de I’Atmosphère, F-59000 Lille, France
- Correspondence: (C.F.); (X.T.)
| | - Xiaofeng Tang
- Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
- Correspondence: (C.F.); (X.T.)
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Qi K, Xu M, Yin H, Wu L, Hu Y, Yang J, Liu C, Pan Y. Online Monitoring the Key Intermediates and Volatile Compounds Evolved from Green Tea Roasting by Synchrotron Radiation Photoionization Mass Spectrometry. J Am Soc Mass Spectrom 2021; 32:1402-1411. [PMID: 33961425 DOI: 10.1021/jasms.1c00012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Online monitoring of the volatile compounds during the tea roasting process is crucial to find the optimum roasting conditions and improve the quality of green tea. In this work, synchrotron radiation photoionization mass spectrometry (SR-PIMS) was utilized to online monitor the evolved gaseous compounds during the tea roasting process. By virtue of "soft" ionization and fast data acquisition characteristics of SR-PIMS, dozens of aroma compounds including alcohols, aldehydes, furans, and nitrogen- and sulfur-containing species were detected and identified in real time. Moreover, 5-hydroxymethylfurfural (5-HMF), the key intermediate of Maillard reactions, was found with high sensitivity. Evolution processes of all the products could be observed via the time- and temperature-resolved profiles in N2 and the air. Dehydration was found to be the first step during roasting. Oxygen in the air was found to accelerate the formation rate of various stable species and intermediates in the course of the thermal treatment of fresh green tea. The formation mechanisms of evolved compounds such as three sulfur-containing compounds, i.e., dimethyl sulfide, hydrogen sulfide, and methanethiol, could be proposed according to the step-by-step formation process. The time-resolved results were demonstrated to be applicable in the evaluation of different roasting processes by statistical analysis. The optimum tea roasting temperature and duration are proposed to be around 200 °C and 1000 s.
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Affiliation(s)
- Keke Qi
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
| | - Minggao Xu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
| | - Hao Yin
- National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, P. R. China
| | - Liutian Wu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
| | - Yonghua Hu
- Research and Development Centre, China Tobacco Anhui Industrial Co., Ltd., Hefei 230088, P. R. China
| | - Jiuzhong Yang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
| | - Chengyuan Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
| | - Yang Pan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, P. R. China
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Heide J, Adam TW, Jacobs E, Wolter JM, Ehlert S, Walte A, Zimmermann R. Puff-resolved analysis and selected quantification of chemicals in the gas phase of E-Cigarettes, Heat-not-Burn devices and conventional cigarettes using single photon ionization time-of-flight mass spectrometry (SPI-TOFMS): A comparative study. Nicotine Tob Res 2021; 23:2135-2144. [PMID: 33993304 DOI: 10.1093/ntr/ntab091] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 05/14/2021] [Indexed: 01/14/2023]
Abstract
INTRODUCTION A wide array of alternative nicotine delivery devices (ANDD) has been developed and they are often described as less harmful than combustible cigarettes. This work compares the chemical emissions of three ANDD in comparison to cigarette smoke. All the tested ANDD are characterized by not involving combustion of tobacco. METHOD Single photon ionization time-of-flight mass spectrometry (SPI-TOFMS) is coupled to a linear smoking machine, which allows a comprehensive, online analysis of the gaseous phase of the ANDD aerosol and the conventional cigarette smoke (CC). The following devices were investigated in this study: a tobacco cigarette with a glowing piece of coal as a heating source, an electric device for heating tobacco and a first-generation electronic cigarette. Data obtained from a standard 2R4F research cigarette are taken as a reference. RESULTS The puff-by-puff profile of all products was recorded. The ANDD show a substantial reduction or complete absence of known harmful and potentially harmful substances compared to the CC. In addition, tar substances (i.e. semivolatile and low volatile aromatic and phenolic compounds) are formed to a much lower extent. Nicotine, however, is supplied in comparable amounts except for the investigated electronic cigarette. CONCLUSIONS The data shows that consumers switching from CC to ANDD are exposed to lower concentrations of harmful and potentially harmful substances. However, toxicological and epidemiological studies must deliver conclusive results if these reduced exposures are beneficial for users. IMPLICATION The comparison of puff-resolved profiles of emissions from different tobacco products, traditional and alternative, may help users switch to lower emission products. Puff-resolved comparison overcomes technical changes, use modes between products and may help in their regulation.
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Affiliation(s)
- J Heide
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany
| | - T W Adam
- Joint Mass Spectrometry Centre, Cooperation Group "Comprehensive Molecular Analytics", Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany.,Bundeswehr University Munich, Neubiberg, Germany
| | - E Jacobs
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany
| | - J-M Wolter
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany
| | - S Ehlert
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany.,Photonion GmbH, Schwerin, Germany
| | - A Walte
- Photonion GmbH, Schwerin, Germany
| | - R Zimmermann
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Rostock, Germany.,Joint Mass Spectrometry Centre, Cooperation Group "Comprehensive Molecular Analytics", Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany
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Czech H, Heide J, Ehlert S, Koziorowski T, Zimmermann R. Smart Online Coffee Roasting Process Control: Modelling Coffee Roast Degree and Brew Antioxidant Capacity for Real-Time Prediction by Resonance-Enhanced Multi-Photon Ionization Mass Spectrometric (REMPI-TOFMS) Monitoring of Roast Gases. Foods 2020; 9:foods9050627. [PMID: 32422859 PMCID: PMC7278678 DOI: 10.3390/foods9050627] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 05/06/2020] [Accepted: 05/07/2020] [Indexed: 02/07/2023] Open
Abstract
Process control with high time resolution is essential to maintain high product quality in coffee roasting. However, analytical techniques for quality assurance or measurements of desired coffee properties are often labor-intensive and can only be conducted after dropping the coffee beans. Resonance-enhanced multi-photon ionization time-of-flight mass spectrometry (REMPI-TOFMS) at 248 nm and 266 nm was applied to analyze the composition of the roast gas from small-scale Arabica coffee roasting. Coffee beans were dropped after different roasting times, ground and analyzed by Colorette to obtain the roast degree. Additionally, the antioxidant capacity of the coffee brew was determined by Folin–Ciocalteu (FC) assay. Models for the prediction of Colorette and FC values from REMPI mass spectra were constructed by partial least squares (PLS) regression. REMPI-TOFMS enables the prediction of Colorette values with a root-mean-square error in prediction (RMSEP) below 5 for both wavelengths. FC values could be predicted using REMPI at 248 nm with an RMSEP of 80.3 gallic acid equivalents (GA-eq) mg L−1, while REMPI at 266 nm resulted in RMSEP of 151 GA-eq mg L−1. Finally, the prediction of Colorette and FC value at 5 s time resolution were demonstrated with online measurements.
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Affiliation(s)
- Hendryk Czech
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (J.H.); (R.Z.)
- Joint Mass Spectrometry Centre, Cooperation Group “Comprehensive Molecular Analytics”, Helmholtz Zentrum München-German Research Center for Environmental Health GmbH, Gmunder Str. 37, 81379 München, Germany
- Correspondence:
| | - Jan Heide
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (J.H.); (R.Z.)
| | - Sven Ehlert
- Photonion GmbH, Hagenower Str. 73, 19061 Schwerin, Germany;
- Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
| | - Thomas Koziorowski
- PROBAT-Werke von Gimborn Maschinenfabrik GmbH, Reeser Str. 94, 46446 Emmerich am Rhein, Germany;
| | - Ralf Zimmermann
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (J.H.); (R.Z.)
- Joint Mass Spectrometry Centre, Cooperation Group “Comprehensive Molecular Analytics”, Helmholtz Zentrum München-German Research Center for Environmental Health GmbH, Gmunder Str. 37, 81379 München, Germany
- Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
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Heide J, Czech H, Ehlert S, Koziorowski T, Zimmermann R. Toward Smart Online Coffee Roasting Process Control: Feasibility of Real-Time Prediction of Coffee Roast Degree and Brew Antioxidant Capacity by Single-Photon Ionization Mass Spectrometric Monitoring of Roast Gases. J Agric Food Chem 2020; 68:4752-4759. [PMID: 31967467 DOI: 10.1021/acs.jafc.9b06502] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Precise controlling and monitoring the status of the coffee roasting process is essential for consistent product quality and optimization toward targeted coffee properties. In small-scale roasting experiments, the chemical composition of the roasting off-gas was analyzed by online single-photon ionization time-of-flight mass spectrometry (SPI-TOFMS) at 118 nm with 5 s time resolution. Subsequently, mass spectra at the drop of the coffee beans were combined with off-line measurements of roast degree, described by color value "Colorette", and the antioxidant capacity, obtained from the Folin-Ciocalteu (FC) assay, in an explanatory projection on latent structure regression model. While the roast degree gives an indication of the coffee flavor, antioxidants in brewed coffee are regarded as beneficial for human health. Colorette and FC values could be derived from the SPI mass spectra with root-mean-square errors from Monte Carlo cross-validation of 6.0 and 139 mg of gallic acid equiv L-1, respectively, and explained covariance (R2CV) better than 89%. Finally, the regression models were applied to the SPI mass spectra over the entire roast to demonstrate the predictive ability for online process control in real time.
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Affiliation(s)
- Jan Heide
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
| | - Hendryk Czech
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
- Joint Mass Spectrometry Centre, Cooperation Group "Comprehensive Molecular Analytics", Helmholtz Zentrum München-German Research Center for Environmental Health GmbH, Gmunder Straße 37, 81379 München, Germany
| | - Sven Ehlert
- Photonion GmbH, Hagenower Straße 73, 19061 Schwerin, Germany
- Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
| | - Thomas Koziorowski
- PROBAT-Werke von Gimborn Maschinenfabrik GmbH, Reeser Straße 94, 46446 Emmerich am Rhein, Germany
| | - Ralf Zimmermann
- Joint Mass Spectrometry Centre, Chair of Analytical Chemistry, Institute of Chemistry, University of Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
- Joint Mass Spectrometry Centre, Cooperation Group "Comprehensive Molecular Analytics", Helmholtz Zentrum München-German Research Center for Environmental Health GmbH, Gmunder Straße 37, 81379 München, Germany
- Department Life, Light & Matter, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany
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Winfough M, Meloni G. Investigation on the absolute and relative photoionization cross sections of 3 potential propargylic fuels. J Mass Spectrom 2017; 52:799-808. [PMID: 28865113 DOI: 10.1002/jms.4023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/15/2017] [Accepted: 08/24/2017] [Indexed: 06/07/2023]
Abstract
Absolute photoionization cross sections for 2 potential propargylic fuels (propargylamine and dipropargyl ether) along with the partial ionization cross sections for their dissociative fragments are measured and presented for the first time via synchrotron photoionization mass spectrometry. The experimental setup consists of a multiplexed orthogonal time-of-flight mass spectrometer and is located at the Advanced Light Source facility of the Lawrence Berkeley National Laboratory in Berkeley, California. Data for a third propargylic compound (propargyl alcohol) were taken; however, because of its low signal, due to its weakly bound cation, only the dissociative ionization fragment from the H-loss channel is observed and presented. Suggested pathways leading to formation of dissociative photoionization fragments along with CBS-QB3 calculated adiabatic ionization energies and appearance energies for the dissociative fragments are also presented.
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Affiliation(s)
- Matthew Winfough
- Department of Chemistry, University of San Francisco, San Francisco, California, 94117-1080, USA
| | - Giovanni Meloni
- Department of Chemistry, University of San Francisco, San Francisco, California, 94117-1080, USA
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Stein T, Bandyopadhyay B, Troy TP, Fang Y, Kostko O, Ahmed M, Head-Gordon M. Ab initio dynamics and photoionization mass spectrometry reveal ion-molecule pathways from ionized acetylene clusters to benzene cation. Proc Natl Acad Sci U S A 2017; 114:E4125-33. [PMID: 28484019 DOI: 10.1073/pnas.1616464114] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The growth mechanism of hydrocarbons in ionizing environments, such as the interstellar medium (ISM), and some combustion conditions remains incompletely understood. Ab initio molecular dynamics (AIMD) simulations and molecular beam vacuum-UV (VUV) photoionization mass spectrometry experiments were performed to understand the ion-molecule growth mechanism of small acetylene clusters (up to hexamers). A dramatic dependence of product distribution on the ionization conditions is demonstrated experimentally and understood from simulations. The products change from reactive fragmentation products in a higher temperature, higher density gas regime toward a very cold collision-free cluster regime that is dominated by products whose empirical formula is (C2H2) n+, just like ionized acetylene clusters. The fragmentation products result from reactive ion-molecule collisions in a comparatively higher pressure and temperature regime followed by unimolecular decomposition. The isolated ionized clusters display rich dynamics that contain bonded C4H4+ and C6H6+ structures solvated with one or more neutral acetylene molecules. Such species contain large amounts (>2 eV) of excess internal energy. The role of the solvent acetylene molecules is to affect the barrier crossing dynamics in the potential energy surface (PES) between (C2H2)n+ isomers and provide evaporative cooling to dissipate the excess internal energy and stabilize products including the aromatic ring of the benzene cation. Formation of the benzene cation is demonstrated in AIMD simulations of acetylene clusters with n > 3, as well as other metastable C6H6+ isomers. These results suggest a path for aromatic ring formation in cold acetylene-rich environments such as parts of the ISM.
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10
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Price C, Fathi Y, Meloni G. Absolute photoionization cross sections of two cyclic ketones: cyclopentanone and cyclohexanone. J Mass Spectrom 2017; 52:259-270. [PMID: 28231419 DOI: 10.1002/jms.3923] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 02/15/2017] [Accepted: 02/17/2017] [Indexed: 06/06/2023]
Abstract
Absolute photoionization cross sections for cyclopentanone and cyclohexanone, as well as partial ionization cross sections for the dissociative ionized fragments, are presented in this investigation. Experiments are performed via a multiplexed photoionization mass spectrometer utilizing vacuum ultraviolet (VUV) synchrotron radiation supplied by the Advanced Light Source of Lawrence Berkeley National Laboratory. These results allow the quantification of these species that is relevant to investigate the kinetics and combustion reactions of potential biofuels. The CBS-QB3 calculated values for the adiabatic ionization energies agree well with the experimental values, and the identification of possible dissociative fragments is discussed for both systems. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- Chelsea Price
- Department of Chemistry, University of San Francisco, CA, 94117, USA
| | - Yasmin Fathi
- Department of Chemistry, University of San Francisco, CA, 94117, USA
| | - Giovanni Meloni
- Department of Chemistry, University of San Francisco, CA, 94117, USA
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11
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Smith AR, Meloni G. Absolute photoionization cross sections of furanic fuels: 2-ethylfuran, 2-acetylfuran and furfural. J Mass Spectrom 2015; 50:1206-1213. [PMID: 26505765 DOI: 10.1002/jms.3638] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 07/23/2015] [Accepted: 07/28/2015] [Indexed: 06/05/2023]
Abstract
Absolute photoionization cross sections of the molecules 2-ethylfuran, 2-acetylfuran and furfural, including partial ionization cross sections for the dissociative ionized fragments, are measured for the first time. These measurements are important because they allow fuel quantification via photoionization mass spectrometry and the development of quantitative kinetic modeling for the complex combustion of potential fuels. The experiments are carried out using synchrotron photoionization mass spectrometry with an orthogonal time-of-flight spectrometer used for mass analysis at the Advanced Light Source of Lawrence Berkeley National Laboratory. The CBS-QB3 calculations of adiabatic ionization energies and appearance energies agree well with the experimental results. Several bond dissociation energies are also derived and presented.
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Affiliation(s)
- Audrey R Smith
- Department of Chemistry, University of San Francisco, San Francisco, CA, 94117-1080, USA
| | - Giovanni Meloni
- Department of Chemistry, University of San Francisco, San Francisco, CA, 94117-1080, USA
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