Towards a complete picture of organics in the atmosphere with a filter-based CIMS approach

Chemical Ionization Mass Spectrometry (CIMS) is an effective technique for accurate and sensitive detection of atmospheric organic compounds relevant to atmospheric chemistry and aerosol particle formation. Several types of mass spectrometers have been developed and used widely by the atmospheric community for online measurements. One of the limitations of the online technique is its size and weight and therefore, challenges in measuring in remote locations. To facilitate measurements of organic vapours, a filter desorption unit was developed that can be easily mounted to APi-ToF (Tofwerk AG) or Orbitrap (ThermoFisher) mass spectrometers. Tenax-coated filters, which maximize the retention of organic vapours, are used for the collection of ambient air. Then, the collected filter deposit is thermally desorbed while the temperature rises to 200 C in three minutes. In the next step Multi-scheme chemical ionization inlet, MION2 (Karsa Ltd.), is used for chemical ionization with X-ray and preparation of the analyte to the detection in the mass spectrometer without further chromatographic separation. The whole process takes less than five minutes. This new method has already been tested on various groups of compounds, including organics, and will be extended to more species in the near future. In conclusion, the new filter-based approach in combination with the excellent detection limits of MION2, expands the use of CIMS instruments and opens possibilities for sampling in remote locations as well as on new platforms, such as drones.