International Journal of Mass Spectrometry 286 (2009) 122–128 Contents lists available at ScienceDirect International Journal of Mass Spectrometry journal homepage: www.elsevier.com/locate/ijms Short communication A high resolution and high sensitivity proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) A. Jordan a , S. Haidacher a , G. Hanel a , E. Hartungen a , L. Märk a , H. Seehauser a , R. Schottkowsky a , P. Sulzer a , T.D. Märk a,b,∗ a Ionicon Analytik Gesellschaft m.b.H., Technikerstr. 21a, A-6020 Innsbruck, Austria b Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität, Technikerstr. 25, A-6020 Innsbruck, Austria article info Article history: Received 31 March 2008 Received in revised form 13 July 2009 Accepted 13 July 2009 Available online 24 July 2009 Keywords: Proton-transfer-reaction time-of-flight mass spectrometer PTR-MS PTR-TOF-MS Volatile organic compounds abstract Proton-transfer-reaction mass spectrometry (PTR-MS) developed about 10 years ago is used today in a wide range of scientific and technical fields allowing real-time on-line measurements of volatile organic compounds in air with a high sensitivity and a fast response time. Most instruments employed so far use quadrupole filters to analyze product ions generated in the reaction drift tube. Due to the low mass resolution of the quadrupoles used this has the disadvantage that identification of trace gases under study is not unambiguous. Here we report the development of a new version of PTR-MS instruments using a time-of-flight mass spectrometer, which is capable of measuring VOCs at ultra-low concentrations (as low as a few pptv) under high mass resolution (as high as 6000 m/m in the V-mode) with a mass range of beyond 100 000 amu. This instrument was constructed by interfacing the well characterized and recently improved Ionicon hollow cathode ion source and drift tube section with a Tofwerk orthogonal accelera- tion reflectron time-of-flight mass spectrometer. We will first discuss the set-up of this new PTR-TOF-MS mass spectrometer instrument, its performance (with a sensitivity of several tens of cps/ppbv) and finally give some examples concerning urban air measurements where sensitivity, detection limit and mass resolution is essential to obtain relevant data. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Volatile organic compounds (VOCs) in the atmosphere are emitted from different biogenic and anthropogenic sources. The production, storage and use of fossil fuel products as well as inten- sive agriculture and biomass burning leads to an increasing change of the atmospheric composition. Deposition processes and impor- tant photochemical reactions are removing and changing the VOC composition in the atmosphere. Photochemical reactions are dom- inated by the hydroxyl radical (OH) which is produced by photons from water during the daytime. The reactions of VOCs with the OH radical require different time scales from minutes to months. For many established analyzers a sample preparation and accu- mulation over some time is necessary which results in bad time resolution. Proton-transfer-reaction mass spectrometry (PTR-MS) has overcome some of the disadvantages of traditional GC measure- ments and is by now a well established mass spectrometric tech- ∗ Corresponding author at: Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität, Technikerstr. 25, A-6020 Innsbruck, Austria. Tel.: +43 512 507 6240; fax: +43 512 507 2932. E-mail address: tilmann.maerk@uibk.ac.at (T.D. Märk). nique used in a wide variety of fields including besides fundamental mass spectrometry, atmospheric science, medical and biotechno- logical applications, food and flavour science and industrial mon- itoring [1–4]. PTR-MS was developed as a new method for quan- titative trace gas analysis in the nineties by Lindinger et al. at the Institut für Ionenphysik in Innsbruck and immediately overcame some of the disadvantages of gas chromatographic methods, how- ever at the cost of chemical detail [1,2]. Over the past 10 years much has been unravelled about the performance, response and speci- ficity of PTR-MS instruments and present day knowledge in partic- ular concerning field measurements of atmospheric VOCs has been summarized in the seminal review by de Gouw and Warnecke [4]. Besides the many advantages, one of the drawbacks of PTR-MS is the fact that only the nominal mass-to-charge ratio of the pro- tonated parent ion (or product ion) can be determined, which is a useful quantity but does not always allow a unique identification of the VOCs under study. The presence of several different species on the same nominal mass, cluster ion formation and parent ion fragmentation may lead to complications in the interpretation of ion signals measured. Various ways have been developed to over- come these complications (including specially designed drift tubes, ion traps and triple quads and coupling of PTR-MS with GC [5]), the most obvious one is however the use of a high resolution mass 1387-3806/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ijms.2009.07.005