The API-TOF is a flexible research platform for labs using unique ion source hardware

An atmospheric pressure interface (API) mass spectrometer designed for easy coupling to ion sources with operating pressures between 1 and 1000 mbar. Ready to use in the lab or field.

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Advantages of API-TOF

  • Convenient, adaptable source-mounting flange – makes installation and interchange of sources fast and easy
  • Employs any of our TOF analyzers
  • Available as a research instrument or as an OEM component
  • 4 differential pumping stages between ion source and TOF with RF and DC focusing optics
  • Compact, robust assembly for bench-top or field applications, as shown in photo
  • Successfully adapted for many mobile laboratories, including: aircraft, research ships, trucks, and even a zeppelin
  • Ideal instrument for research groups developing novel ionization schemes

Example Ion Sources for API-TOF

  • Proton Transfer Reaction (Vocus PTR-TOF)
  • Extractive Electrospray Ionization (EESI)
  • Reduced Pressure or Atmospheric Pressure Chemical Ionization
  • Electrospray Ionization (ESI)
  • Direct Analysis in Real Time (DART,  Ionsense)
  • Dielectric Barrier Discharge (DBD)
  • Corona Discharge
  • X-Ray Ionization
  • Radionuclides

TOF Analyzer Performance Specifications

Ion Source Pressure 1 to 1,000 mbar
Differential Pumping Stages 1 to 3 mbar: Quadrupole 1
~1e-3 mbar: Quadrupole 2
~1e-5 mbar: Primary Beam Lens Stack
1e-6 mbar: TOF
Vacuum Pumps (excluding ion source) (1) Scroll Pump
(1) Turbo Pump
(1) Diagphram Pump
Mass Rack with HTOF: 85 kg
Rack with LTOF: 107 kg
Scroll Pump: 32 kg
Dimensions of Rack-Mounted System HTOF Version: 565 x 395 x 800 mm
LTOF Version: 615 x 480 x 1480 mm
Power Requirements (Excluding Source) 100-240 VAC, 50-60 Hz, 2 kW

API-TOF Publications


  1. V. Pospisilova; F. Lopez-Hilfiker; D. Bell; I. El Haddad; C. MohrW. Huang; L. HeikkinenM. Xiao; J. Dommen; A. Prevot;  U. Baltensperger; J. Slowik.  On the fate of oxygenated organic molecules in atmospheric aerosol particles.  Science Advances, 2020. DOI: 10.1126/sciadv.aax8922
  2. Stefenelli, G.; Pospisilova, V.; Lopez-Hilfiker, F.; Daellenbach, K.; Hüglin, Yandong TongC.;  Baltensperger, U.; Prévôt, A.; Slowik, J. Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 1: Biogenic influences and day–night chemistry in summer. Atmospheric Chemistry and Physics, 2019. DOI: 10.5194/acp-19-14825-2019
  3. Qi, L.; Chen, M.; Stefenelli, G.; Pospisilova, V.; Tong, Y.; Bertrand, A.; Hueglin, C.;  Ge, X.; Baltensperger, U.;   Prévôt, A.; Slowik, J. Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 2: Biomass burning influences in winter. Atmospheric Chemistry and Physics, 2019DOI: 10.5194/acp-19-8037-2019
  4. F. Lopez-Hilfiker et al. An Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles, Atmos. Meas. Tech. Discuss.,  2019. DOI: 10.5194/amt-12-4867-2019


  1. F. Bianchi et al. New particle formation in the free troposphere: A question of chemistry and timing.  Science, 2016. DOI: 10.1126/science.aad5456
  2.  J. Kirkby et al. Ion-induced nucleation of pure biogenic particles. Nature, 2016. DOI:10.1038/nature17953
  3. J. Tröstl et al. The role of low-volatility organic compounds in initial particle growth in the atmosphere. Nature, 2016. DOI:10.1038/nature18271


  1. Neutral molecular cluster formation of sulfuric acid–dimethylamine observed in real time under atmospheric conditions, A. Kürten, et al., Proc. Natl. Acad. Sci. U.S.A., 111, 42, 15019–15024, 2014. DOI: 10.1073/pnas.1404853111
  2. A large source of low-volatility secondary organic aerosol, Ehn, M. et al, Nature 506, 476–479, 2014. DOI:10.1038/nature13032


  1. Molecular understanding of atmospheric particle formation from sulfuric acid and large oxidized organic molecules, S. Schobesberger, et al., Proc. Natl. Acad. Sci. U.S.A., 110, 43, 17223–17228, 2013. DOI: 10.1073/pnas.1306973110


  1. T. H. Bertram et al.  A field-deployable, chemical ionization time-of-flight mass spectrometer. Atmos. Meas. Tech., 2011. DOI: 10.5194/amt-4-1471-2011


  1. H. Junninen et al. A high-resolution mass spectrometer to measure atmospheric ion composition.  Atmos. Meas. Tech., 2010. DOI: 10.5194/amt-3-1039-2010

*The API-TOF is a core component of the Aerodyne Research ToF-CIMS.   This field-portable chemical ionization mass spectrometer has been deployed for atmospheric measurements around the world.  Complete list of ToF-CIMS publications.

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