Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS

Holzinger, Rupert; Acton, W. Joe F.; Bloss, William J.; Breitenlechner, Martin; Crilley, Leigh R.; Dusanter, Sébastien; Gonin, Marc; Gros, Valerie; Keutsch, Frank N.; Kiendler-Scharr, Astrid; Kramer, Louisa J.; Krechmer, Jordan E.; Languille, Baptiste; Locoge, Nadine; Lopez-Hilfiker, Felipe; Materić, Dušan; Moreno, Sergi; Nemitz, Eiko ORCID: https://orcid.org/0000-0002-1765-6298; Quéléver, Lauriane L.J.; Sarda Esteve, Roland; Sauvage, Stéphane; Schallhart, Simon; Sommariva, Roberto; Tillmann, Ralf; Wedel, Sergej; Worton, David R.; Xu, Kangming; Zaytsev, Alexander. 2019 Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS. Atmospheric Measurement Techniques, 12 (11). 6193-6208. https://doi.org/10.5194/amt-12-6193-2019

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Abstract/Summary

In September 2017, we conducted a proton-transfer-reaction mass-spectrometry (PTR-MS) intercomparison campaign at the CESAR observatory, a rural site in the central Netherlands near the village of Cabauw. Nine research groups deployed a total of 11 instruments covering a wide range of instrument types and performance. We applied a new calibration method based on fast injection of a gas standard through a sample loop. This approach allows calibrations on timescales of seconds, and within a few minutes an automated sequence can be run allowing one to retrieve diagnostic parameters that indicate the performance status. We developed a method to retrieve the mass-dependent transmission from the fast calibrations, which is an essential characteristic of PTR-MS instruments, limiting the potential to calculate concentrations based on counting statistics and simple reaction kinetics in the reactor/drift tube. Our measurements show that PTR-MS instruments follow the simple reaction kinetics if operated in the standard range for pressures and temperature of the reaction chamber (i.e. 1–4 mbar, 30–120∘, respectively), as well as a reduced field strength E∕N in the range of 100–160 Td. If artefacts can be ruled out, it becomes possible to quantify the signals of uncalibrated organics with accuracies better than ±30 %. The simple reaction kinetics approach produces less accurate results at E∕N levels below 100 Td, because significant fractions of primary ions form water hydronium clusters. Deprotonation through reactive collisions of protonated organics with water molecules needs to be considered when the collision energy is a substantial fraction of the exoergicity of the proton transfer reaction and/or if protonated organics undergo many collisions with water molecules.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.5194/amt-12-6193-2019
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-)
ISSN:	1867-1381
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
NORA Subject Terms:	Atmospheric Sciences
Date made live:	09 Apr 2019 13:49 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/522451

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