The effects of molecular weight and thermal decomposition on the sensitivity of a thermal desorption aerosol mass spectrometer

Details

• Journal Title:
  Aerosol Science and Technology
• Personal Author:
  Murphy, D. M.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory) ; CSL (Chemical Sciences Laboratory)
• Description:
  In free molecular flow the slower speed of heavier molecules means that they spend more time in the ion source of a mass spectrometer. Hence the sensitivity of the thermal desorption mass spectrometers such as the Aerodyne Aerosol Mass Spectrometer (AMS) should include a term that scales as the square root of the molecular weight. Thermal decomposition on the vaporizer reduces the molecular weight prior to ionization and changes electron impact cross-sections. Thermal decomposition therefore has the potential to change the sensitivity, in some cases by more than a factor of three. Current AMS calibrations that rely upon an ammonium nitrate calibration and scaling for other components with a relative ionization efficiency may overestimate the concentration of large, thermally stable molecules and underestimate small or thermally unstable molecules. The overall sensitivity of the AMS to organics includes a partial cancellation of these effects. There is an incomplete understanding of the vaporization process, including that of ammonium nitrate.
• Keywords:
  Aerosols Mass Spectrometry Remote Sensing Mass Spectrometry Remote Sensing
• Source:
  Aerosol Science and Technology, 50:2, 118-125, 2016
• DOI:
  https://doi.org/10.1080/02786826.2015.1136403
• Document Type:
  Journal Article
• Rights Information:
  Public Domain
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:c4abd39703d82ce1cf17219da8cecef6e1525c9425befc28d53d64c2a1946d07db8c5bbf3f0292eacb36cd6b7710f0f442f611392f9392597cae0d1012eaa7c3
• Download URL:
  https://repository.library.noaa.gov/view/noaa/27206/noaa_27206_DS1.pdf
• File Type:
  [PDF - 888.98 KB ]