10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Performance of a New VOCUS-PTRTOF for Detecting Volatile-, Semi-Volatile and Low-Volatile Organic Compounds
PEKKA RANTALA, Matthieu Riva, Jordan Krechmer, Yanjun Zhang, Olga Garmash, Liine Heikkinen, Felipe Lopez-Hilfiker, Otso Peräkyla, Yonghong Wang, Mikael Ehn, University of Helsinki
Abstract Number: 792 Working Group: Instrumentation
Abstract Volatile organic compounds (VOCs) have a major impact on aerosol particle formation in the atmosphere. The development of new instruments – mainly mass spectrometers –, has brought new information to better understand the process chain from VOC emissions to oxidized compounds and condensation onto aerosol particles. However, to quantify each step of these chemical and physical processes, it is crucial to measure not only VOCs but also the wide variety of oxidation products from low to highly oxygenated molecules (HOMs).
Usually, the gas-phase measurements have been conducted using mass spectrometry with several different inlet designs to fill all the gaps between VOCs and HOMs. However, this is problematic in many ways. Calibrating all the instruments in a comprehensive way has remained especially challenging. In addition, operating several instruments is laborious, and availability of space and electricity can also be limited in remote locations. Therefore, instruments that can measure a wider range of compounds would be of great interest.
VOCUS PTR-TOF (proton transfer reaction time-of-flight mass spectrometer, TOFWERK AG/Aerodyne Research, Inc.) is a new instrument for detecting volatile organic compounds. The instrument is based on a new PTR-inlet design with sub-ppt detection limits. In December 2017, we organized a laboratory campaign, in which we explored the capability of the VOCUS to simultaneously measure α-pinene oxidation products generated from the ozonolysis of α-pinene under a wide variety of experimental conditions. Chemical characterization of gas-phase products was compared to several other types of chemical ionization mass spectrometers.
While data processing is still under way, first results indicate sensitive detection of the precursor and oxidized monomers (e.g. C10HxO<8). For more oxidized products and/or dimers, the VOCUS either cannot measure these compounds or the instrument must be tuned more carefully to optimize its performance for these molecules.