Effects of modular ion-funnel technology onto analysis of breath VOCs by means of real-time mass spectrometry
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RESEARCH PAPER
Effects of modular ion-funnel technology onto analysis of breath VOCs by means of real-time mass spectrometry Giovanni Pugliese 1 & Felix Piel 2,3,4 & Phillip Trefz 1 & Philipp Sulzer 2 & Jochen K. Schubert 1 & Wolfram Miekisch 1 Received: 27 March 2020 / Revised: 21 July 2020 / Accepted: 24 July 2020 / Published online: 13 August 2020 # The Author(s) 2020
Abstract Proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a powerful tool for real-time monitoring of trace concentrations of volatile organic compounds (VOCs). The sensitivity of PTR-ToF-MS also depends on the ability to effectively focus and transmit ions from the relatively high-pressure drift tube (DT) to the low-pressure mass analyzer. In the present study, a modular ion-funnel (IF) is placed adjacent to the DT of a PTR-ToF-MS instrument to improve the ion-focusing. IF consists of a series of electrodes with gradually decreasing orifice diameters. Radio frequency (RF) voltage and direct current (DC) electric field are then applied to the electrodes to get the ions focused. We investigated the effect of the RF voltage and DC field on the sensitivity of a pattern of VOCs including hydrocarbons, alcohols, aldehydes, ketones, and aromatic compounds. In a proof-ofconcept study, the instrument operating both as normal DT (DC-mode) and at optimal IF conditions (RF-mode) was applied for the breath analysis of 21 healthy human subjects. For the range of investigated VOCs, an improvement of one order of magnitude in sensitivity was observed in RF-mode compared with DC-mode. Limits of detection could be improved by a factor of 2–4 in RF-mode compared with DC-mode. Operating the instrument in RF-mode allowed the detection of more compounds in the exhaled air compared with DC-mode. Incorporation of the IF considerably improved the performance of PTR-ToF-MS allowing the real-time monitoring of a larger number of potential breath biomarkers. Keywords PTR-ToF-MS . Ion-funnel . Real-time mass spectrometry . Breath analysis . VOCs
Introduction Proton transfer reaction mass spectrometry (PTR-MS) is an analytical technique that allows real-time monitoring of volatile organic compounds (VOCs) at low concentrations. It is
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00216-020-02846-8) contains supplementary material, which is available to authorized users. * Wolfram Miekisch [email protected] 1
Department of Anaesthesia and Intensive Care, Rostock University Medical Center, Schillingallee 35, 18057 Rostock, Germany
2
IONICON Analytik GmbH, Eduard-Bodem-Gasse 3, 6020 Innsbruck, Austria
3
Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
4
Present address: Department of Chemistry, University of Oslo, Sem Sælands vei 26, 0371 Oslo, Norway
widely used, e.g. in environmental sciences, food chemistry, homeland security, and breath analysis [1]. Since its introduction in the 1990s [2], PTR-MS has been improved i
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