PTR3: An Instrument for Studying the Lifecycle of Reactive Organic Carbon in the Atmosphere
journal contributionposted on 24.04.2017, 00:00 by Martin Breitenlechner, Lukas Fischer, Markus Hainer, Martin Heinritzi, Joachim Curtius, Armin Hansel
We have developed and characterized the novel PTR3, a proton transfer reaction-time-of-flight mass spectrometer (PTR-TOF) using a new gas inlet and an innovative reaction chamber design. The reaction chamber consists of a tripole operated with rf voltages generating an electric field only in the radial direction. An elevated electrical field is necessary to reduce clustering of primary hydronium (H3O+) and product ions with water molecules present in the sample gas. The axial movement of the ions is achieved by the sample gas flow only. Therefore, the new design allows a 30-fold longer reaction time and a 40-fold increase in pressure compared to standard PTR-TOF-MS. First calibration tests show sensitivities of up to 18000 counts per second/parts per billion and volume (cps/ppbv) at a mass resolution of >8000 m/Δm (fwhm). The new inlet using center-sampling through a critical orifice reduces wall losses of low volatility compounds. Therefore, the new PTR3 instrument is sensitive to VOC typically present in the ppbv range as well as to semivolatile organic compounds (SVOC) and even highly oxidized organic molecules (HOMs) present in the parts per quadrillion per volume (ppqv) range in the atmosphere.
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reaction chambermass resolutiongas inletsample gasproton transfer reaction-time-of-flight mass spectrometerPTR-TOF-MSvolatility compoundsreaction timeSVOCwall losseswater moleculesReactive Organic CarbonFirst calibration tests show sensitivitiessample gas flowH 3 OVOCppbv range18000 countsreaction chamber designproduct ionsvolumerf voltagesPTR 3 instrumentPTR-TOFHOM