Proton transfer reaction mass spectrometry (PTR-MS) is a well-established technique for real-time analysis of volatile organic compounds (VOCs). Although it is extremely sensitive (with sensitivities of up to 4500 cps/ppbv, limits of detection <1 pptv and the response times of approximately 100 ms), the selectivity of PTR-MS is still somewhat limited, as isomers cannot be separated. Recently, selectivity-enhancing measures, such as manipulation of drift tube parameters (reduced electric field strength) and using primary ions other than H3O+, such as NO+ and O2+, have been introduced. However, monoterpenes, which belong to the most important plant VOCs, still cannot be distinguished so more traditional technologies, such as gas chromatography mass spectrometry (GC-MS), have to be utilised. GC-MS is very time consuming (up to 1 h) and cannot be used for real-time analysis. Here, we introduce a sensitive, near-to-real-time method for plant monoterpene research—PTR-MS coupled with fastGC. We successfully separated and identified six of the most abundant monoterpenes in plant studies (α- and β-pinenes, limonene, 3-carene, camphene and myrcene) in less than 80 s, using both standards and conifer branch enclosures (Norway spruce, Scots pine and black pine). Five monoterpenes usually present in Norway spruce samples with a high abundance were separated even when the compound concentrations were diluted to 20 ppbv. Thus, fastGC-PTR-ToF-MS was shown to be an adequate one-instrument solution for plant monoterpene research.
PTR-MS FastGC Monoterpenes VOC Plant VOCs Pinene
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DM and ML gratefully acknowledge the Proton Ionization Molecular Mass Spectrometry (PIMMS) Initial Training Network (ITN), which is funded by the European Commission’s 7th Framework Programme under Grant Agreement Number 287382 for financial support, providing a high-quality training programme and the opportunity to link with leaders of cutting edge analytical techniques.
Conflict of interest
The measurements were conducted in the laboratory of IONICON Analytik, the manufacturer of the PTR-TOF 8000 and the fastGC. Philipp Sulzer, Jens Herbig, and Matteo Lanza are employed by IONICON Analytik. Other authors declare that they have no conflict of interest.
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