Overview
Researchers from the Institute for Ion Physics and Applied Physics at the University of Innsbruck have developed a concept for a Chemical Ionization – Time-Of-Flight Mass Spectrometry (CI-TOFMS) instrument (Breitenlechner et al., 2017), the so-called PTR3. The fundamental idea behind PTR3 is the decoupling of the ion-molecule reaction chemistry from the axial transport of the reagent and analyte ions. This decoupling allows variations in the E/N without affecting the reaction time. The realization of elevated pressure and increased reaction time tremendously boosts the overall sensitivity of the instrument
As a partner in this original research project we have pursued the PTR3 concept and successfully developed an advanced version of this high performance trace VOC-ELVOC analyzer: The PTR3-TOF 10k. Three ion sources now allow for fast switching of different primary reagent ions, overall ion transmission was further improved and the instrument was completed with a dedicated high resolution TOF-MS - the ioniTOF 10K.
The PTR3 was discontinued and has been replaced by the superior FUSION PTR technology and FUSION PTR-TOF instruments.
The PTR3 is a specialized system dedicated to the highly sensitive detection of ultra low traces of volatile organic compounds and their oxidation products that enables monitoring reactions from the first oxidation steps up to highly-oxygenated organic molecules (HOMs) down to ppqV levels (Breitenlechner et al., 2017). The inlet system and the ionization chamber are especially designed to reduce surface interactions. This concept of contact free sampling allows for detecting organics of virtually all volatility classes ranging from volatile (VOC) to extremely low volatile (ELVOC).
Results from the well-known CLOUD experiment very well illustrate the advantages of the PTR3 over a commonly used nitrate (NO3-) Chemical Ionization Mass Spectrometer (CIMS). Both instruments show a similar detection efficiency towards ELVOCs, but the PTR3 clearly excels the CIMS when it comes to the detection of less oxidized VOCs (see e.g. Stolzenburg et al., 2018; Simon et al., 2020). The PTR3 even allows for detecting and quantifying organic peroxy (RO2) radicals. By including these radicals, Hansel et al. (2018) could achieve carbon closure for a cyclohexene ozonolysis experiment when operated in soft adduct NH4+ ionization mode. Furthermore, Zaytsev et al. (2019) recently demonstrated the ability of the PTR3 to study the composition and concentration of secondary organic aerosols.