title: Online Quantification of Criegee Intermediates of α-Pinene Ozonolysis by Stabilization with Spin Traps and Proton-Transfer Reaction Mass Spectrometry Detection.
abstract: Biogenic alkenes, which are among the most abundant volatile organic compounds in the atmosphere, are readily oxidized by ozone. Characterizing the reactivity and kinetics of the first-generation products of these reactions, carbonyl oxides (often named Criegee intermediates), is essential in defining the oxidation pathways of organic compounds in the atmosphere but is highly challenging due to the short lifetime of these zwitterions. Here, we report the development of a novel online method to quantify atmospherically relevant Criegee intermediates (CIs) in the gas phase by stabilization with spin traps and analysis with proton-transfer reaction mass spectrometry. Ozonolysis of α-pinene has been chosen as a proof-of-principle model system. To determine unambiguously the structure of the spin trap adducts with α-pinene CIs, the reaction was tested in solution, and reaction products were characterized with high-resolution mass spectrometry, electron paramagnetic resonance, and nuclear magnetic resonance spectroscopy. DFT calculations show that addition of the Criegee intermediate to the DMPO spin trap, leading to the formation of a six-membered ring adduct, occurs through a very favorable pathway and that the product is significantly more stable than the reactants, supporting the experimental characterization. A flow tube set up has been used to generate spin trap adducts with α-pinene CIs in the gas phase. We demonstrate that spin trap adducts with α-pinene CIs also form in the gas phase and that they are stable enough to be detected with online mass spectrometry. This new technique offers for the first time a method to characterize highly reactive and atmospherically relevant radical intermediates in situ.
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Chiara
authors.identifier: 0000-0001-7821-7398
authors.initials: C
authors.lastname: Giorio
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Campbell
authors.affiliation: Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra, Università degli Studi di Milano Bicocca , Piazza della Scienza 1, Milano 20126, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bruschi
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Padova , via Marzolo 1, Padova 35131, Italy.
authors.forename: Francesco
authors.identifier: 0000-0003-1474-867X
authors.initials: F
authors.lastname: Tampieri
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Padova , via Marzolo 1, Padova 35131, Italy.
authors.forename: Antonio
authors.identifier: 0000-0002-2009-5874
authors.initials: A
authors.lastname: Barbon
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Padova , via Marzolo 1, Padova 35131, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Toffoletti
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Padova , via Marzolo 1, Padova 35131, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Tapparo
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Claudia
authors.initials: C
authors.lastname: Paijens
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wedlake
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Grice
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Howe
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
authors.forename: Markus
authors.initials: M
authors.lastname: Kalberer
mesh_terms: D000475:Alkenes / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry; D007700:Kinetics; D013058:Mass Spectrometry; D009862:Online Systems; D010087:Oxides / Q000032:analysis*; D010126:Ozone / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory
chemical_list: D000475:Alkenes; D010087:Oxides; D011522:Protons; D010126:Ozone