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Anttalainen O, Karjalainen M, Lattouf E, Hecht O, Vanninen P, Hakulinen H, Kotiaho T, Thomas C, Eiceman G. Time-Resolved Ion Mobility Spectrometry with a Stop Flow Confined Volume Reaction Region. Anal Chem 2024; 96:10182-10192. [PMID: 38857882 PMCID: PMC11209659 DOI: 10.1021/acs.analchem.4c00434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 05/16/2024] [Accepted: 05/17/2024] [Indexed: 06/12/2024]
Abstract
An ion source concept is described where the sample flow is stopped in a confined volume of an ion mobility spectrometer creating time-dependent patterns of ion patterns of signal intensities for ions from mixtures of volatile organic compounds and improved signal-to-noise rate compared to conventional unidirectional drift gas flow. Hydrated protons from a corona discharge were introduced continuously into the confined volume with the sample in air at ambient pressure, and product ions were extracted continuously using an electric field for subsequent mobility analysis. Ion signal intensities for protonated monomers and proton bound dimers were measured and computationally extracted using mobilities from mobility spectra and exhibited distinct times of appearance over 30 s or more after sample injection. Models, and experimental findings with a ternary mixture, suggest that the separation of vapors as ions over time was consistent with differences in the reaction rate for reactions between primary ions from hydrated protons and constituents and from cross-reactions that follow the initial step of ionization. The findings suggest that the concept of stopped flow, introduced here for the first time, may provide a method for the temporal separation of atmospheric pressure ions. This separation relies on ion kinetics and does not require chromatographic technology.
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Affiliation(s)
- Osmo Anttalainen
- VERIFIN,
Finnish Institute for Verification of the Chemical Weapons Convention,
Department of Chemistry, University of Helsinki, Helsinki FI-00014, Finland
| | - Markus Karjalainen
- VERIFIN,
Finnish Institute for Verification of the Chemical Weapons Convention,
Department of Chemistry, University of Helsinki, Helsinki FI-00014, Finland
| | - Elie Lattouf
- VERIFIN,
Finnish Institute for Verification of the Chemical Weapons Convention,
Department of Chemistry, University of Helsinki, Helsinki FI-00014, Finland
| | - Oliver Hecht
- Airsense
Analytics GmbH, Hagenower
Straße 73, Schwerin 19061, Germany
| | - Paula Vanninen
- VERIFIN,
Finnish Institute for Verification of the Chemical Weapons Convention,
Department of Chemistry, University of Helsinki, Helsinki FI-00014, Finland
| | - Hanna Hakulinen
- VERIFIN,
Finnish Institute for Verification of the Chemical Weapons Convention,
Department of Chemistry, University of Helsinki, Helsinki FI-00014, Finland
| | - Tapio Kotiaho
- Drug
Research Program and Division of Pharmaceutical Chemistry and Technology,
Faculty of Pharmacy, University of Helsinki, P.O. Box 56, Helsinki FI-00014, Finland
- Department
of Chemistry, Faculty of Science, University
of Helsinki, P.O.Box 55, Helsinki FIN-00014, Finland
| | - Charles Thomas
- Department
of Chemistry, Loughborough University, Leicestershire LE11 3TU, U.K.
| | - Gary Eiceman
- VERIFIN,
Finnish Institute for Verification of the Chemical Weapons Convention,
Department of Chemistry, University of Helsinki, Helsinki FI-00014, Finland
- New
Mexico
State University, 1175 N Horseshoe Dr., Las Cruces, New Mexico 88003, United States
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Crossley-Lewis J, Dunn J, Hickman IF, Jackson F, Sunley GJ, Buda C, Mulholland AJ, Allan NL. Multilevel quantum mechanical calculations show the role of promoter molecules in the dehydration of methanol to dimethyl ether in H-ZSM-5. Phys Chem Chem Phys 2024; 26:16693-16707. [PMID: 38809246 DOI: 10.1039/d3cp05987a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
Methyl carboxylate esters promote the formation of dimethyl ether (DME) from the dehydration of methanol in H-ZSM-5 zeolite. We employ a multilevel quantum method to explore the possible associative and dissociative mechanisms in the presence, and absence, of six methyl ester promoters. This hybrid method combines density functional theory, with dispersion corrections (DFT-D3), for the full periodic system, with second-order Møller-Plesset perturbation theory (MP2) for small clusters representing the reaction site, and coupled cluster with single, double, and perturbative triple substitution (CCSD(T)) for the reacting molecules. The calculated adsorption enthalpy of methanol, and reaction enthalpies of the dehydration of methanol to DME within H-ZSM-5, agree with experiment to within chemical accuracy (∼4 kJ mol-1). For the promoters, a reaction pathway via an associative mechanism gives lower overall reaction enthalpies and barriers compared to the reaction with methanol only. Each stage of this mechanism is explored and related to experimental data. We provide evidence that suggests the promoter's adsorption to the Brønsted acid site is the most important factor dictating its efficiency.
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Affiliation(s)
- Joe Crossley-Lewis
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Josh Dunn
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Isabel F Hickman
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Fiona Jackson
- Applied Sciences, bp Innovation and Engineering, BP plc, Saltend, Hull, HU12 8DS, UK
| | - Glenn J Sunley
- Applied Sciences, bp Innovation and Engineering, BP plc, Saltend, Hull, HU12 8DS, UK
| | - Corneliu Buda
- Applied Sciences, bp Innovation and Engineering, BP plc, 30 South Wacker Drive, Chicago, IL 60606, USA
| | - Adrian J Mulholland
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Neil L Allan
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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Zhu W, Benkwitz F, Sarmadi B, Kilmartin PA. Validation Study on the Simultaneous Quantitation of Multiple Wine Aroma Compounds with Static Headspace-Gas Chromatography-Ion Mobility Spectrometry. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:15020-15035. [PMID: 34874158 DOI: 10.1021/acs.jafc.1c06411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A new quantitative method based on static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS) is proposed, which enables the simultaneous quantitation of multiple aroma compounds in wine. The method was first evaluated for its stability and the necessity of using internal standards as a quality control measure. The two major hurdles in applying GC-IMS in quantitation studies, namely, nonlinearity and multiple ion species, were also investigated using the Boltzmann function and generalized additive model (GAM) as potential solutions. Metrics characterizing the model performance, including root mean squared error, bias, limit of detection, limit of quantitation, repeatability, reproducibility, and recovery, were investigated. Both nonlinear fitting methods, Boltzmann function and GAM, were able to return desirable analytical outcomes with an acceptable range of error. Potential pitfalls that would cause inaccurate quantitation, that is, effects of ethanol content and competitive ionization, were also discussed. The performance of the SHS-GC-IMS method was subsequently compared against that of a currently established method, namely, GC-MS, using commercial wine samples. These findings provide an initial validation of a GC-IMS-based quantitation method, as well as a starting point for further enhancing the analytical scope of GC-IMS.
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Affiliation(s)
- Wenyao Zhu
- Wine Science Programme, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Kim Crawford Winery, Constellation Brands NZ, 237 Hammerichs Road, Blenheim 7273, New Zealand
| | - Frank Benkwitz
- Kim Crawford Winery, Constellation Brands NZ, 237 Hammerichs Road, Blenheim 7273, New Zealand
| | - Bahareh Sarmadi
- Wine Science Programme, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Paul A Kilmartin
- Wine Science Programme, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Safi ZS, Wazzan N. Benchmark calculations of proton affinity and gas-phase basicity using multilevel (G4 and G3B3), B3LYP and MP2 computational methods of para-substituted benzaldehyde compounds. J Comput Chem 2021; 42:1106-1117. [PMID: 33871092 DOI: 10.1002/jcc.26538] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/03/2021] [Accepted: 04/07/2021] [Indexed: 12/18/2022]
Abstract
This study presents the benchmark calculations of proton affinities (PAs) and gas-phase basicities (GBs) of 8-para substituted benzaldehyde compounds using the multilevel model chemistries (G3B3 and G4), density-functional quantum model (B3LYP) and ab initio model (MP2). The results show that the computed properties are strongly correlated with the available experimental data. The PAs and the GBs of other eight para-substituted benzaldehyde compounds, for which the experimental data does not currently exist, have been calculated using G3B3 and B3LYP methods. The correlations between the experimental PAs and GBs with the computed properties such as PA, GB, chemical properties (bond lengths, electron density and δ1 H NMR chemical shift) of the investigated benzaldehydes have been studied and statistically analyzed. The influence of the substituted groups has been discussed in terms of inductive effect and electron donating and electron withdrawing effect. The results obtained show that the chemical properties of the benzaldehyde compounds are controlled by the strong coupling between the CHO group and the nature of the para-substituent groups through the benzene ring as a conducting linkage.
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Affiliation(s)
- Zaki S Safi
- Chemistry Department, Faculty of Science, Al Azhar University-Gaza, Gaza, Palestine
| | - Nuha Wazzan
- Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
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van Huizen NA, Holmes JL, Burgers PC. One electron less or one proton more: how do they differ? JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4462. [PMID: 31697855 PMCID: PMC7317499 DOI: 10.1002/jms.4462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
From the NIST website and the literature, we have collected the Ionisation Energies (IE) of 3,052 and the Proton Affinities (PA) of 1,670 compounds. For 614 of these, both the IE and PA are known; this enables a study of the relationships between these quantities for a wide variety of molecules. From the IE and PA values, the hydrogen atom affinities (HA) of molecular ions M•+ may also be assessed. The PA may be equated to the heterolytic bond energy of [MH]+ and HA to the homolytic bond energy. Plots of PA versus IE for these substances show (in agreement with earlier studies) that, for many families of molecules, the slope of the ensuing line is less negative than -1, i.e. changes in the PA are significantly less than the concomitant opposite changes in IE. At one extreme (high PA, low IE) are the metals, their oxides and hydroxides, which show a slope of close to -1, at the other extreme (low PA, high IE) are the hydrogen halides, methyl halides and noble gases, which show a slope of ca. -0.3; other molecular categories show intermediate behaviour. One consequence of a slope less negative than -1 is that the changes in ionic enthalpies of the protonated species more closely follow the changes in the enthalpies of the neutral molecules compared with changes in the ion enthalpies of the corresponding radical cations. This is consistent with findings from ab initio calculations from the literature that the incoming proton, once attached to the molecule, may retain a significant amount of its charge. These collected data allow a comparison of the thermodynamic stability of protonated molecules in terms of their homolytic or heterolytic bond cleavages. Protonated nitriles are particularly stable by virtue of the very large hydrogen atom affinities of their radical cations.
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Affiliation(s)
- Nick A. van Huizen
- Department of Neurology, Laboratory of Neuro‐OncologyErasmus Medical CenterRotterdam3015CNThe Netherlands
- Department of SurgeryErasmus Medical CenterRotterdam3015CNThe Netherlands
| | - John L. Holmes
- Department of Chemistry and Biological SciencesUniversity of Ottawa10 Marie CurieOttawaOntarioK1N 6N5Canada
| | - Peter C. Burgers
- Department of Neurology, Laboratory of Neuro‐OncologyErasmus Medical CenterRotterdam3015CNThe Netherlands
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Rapid volatiles fingerprinting by dopant-assisted positive photoionization ion mobility spectrometry for discrimination and characterization of Green Tea aromas. Talanta 2019; 191:39-45. [DOI: 10.1016/j.talanta.2018.08.039] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/03/2018] [Accepted: 08/12/2018] [Indexed: 11/23/2022]
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