Vocus CI-TOF

The Vocus CI-TOF directly measures trace compounds in air in real time
Chemical ionization mass spectrometers with sub-ppt limits of detection for volatile organic and
inorganic compounds (VOCs and VICs). Optimized for use in laboratory, industrial, and mobile

The Vocus CI-TOF is currently compatible with several different reactors:

PTR Reactor

Proton transfer reaction mass spectrometry (PTR-MS) is a powerful technique for the analysis of
a broad range of volatile organic compounds (VOCs). The proprietary Vocus PTR Reactor
reduces wall losses and focuses ions with RF fields to give you up to 10x the sensitivity of other
commercial PTR-MS. The Vocus PTR Reactor is further compatible with other reagent ions
schemes, including ammonium adduct ionization – to target broader ranges of compounds.
See the specification sheet for the PTR reactor.

Aim Reactor
The Vocus Aim Reactor offers fast, sensitive detection of trace organic and inorganic
compounds spanning the entire volatility range. The flow tube reactor operates at an increased
pressure to suppress fragmentation of analyte ions, and uses compact VUV sources to generate
both positive and negative reagent ions.

The Aim is compatible with the FIGAERO inlet. The FIGAERO inlet, which was jointly
developed with the University of Washington, enables semi-continuous detection of both
particle-phase and gas-phase compounds with the ToF-CIMS.

  • Easily interchanged with the standard gas-phase inlet of the ToF-CIMS
  • Sampling cycles between two modes: (i) Gas-phase measurement during aerosol collection (ii) thermal desorption and mass spectral analysis of collected aerosol
  • Automated switching between aerosol, gas, and blank sampling with programmable thermal desorption ramps.

EESI Reactor
Real-time aerosol chemical composition with Extractive Electrospray Ionization (EESI)
The EESI source, which was jointly developed with the Paul Scherer Institute in
Switzerland and our partners at TOFWERK, A.G., enables rapid (< 1 Hz) chemical composition
measurements of aerosol.

  • Solubilizes aerosol stream into droplets and ionizes
  • “Soft” ionization enables detection of molecular aerosol constituents
  • Useable with many different chemical reagent ionization schemes (Na+, Li+, I-)
  • High sensitivity (2,000 – 6,000 counts per second per μg m-3 (cps/ug/m3)) for precise measurements

Nitrate Reactor
Wall-less flow reactor for the measurement of low-volatility gases such as sulfuric acid and highly oxidized.

The Vocus instrument delivers ultra-low limits of detection with the highest available mass resolving power in a field-proven API-TOF platform.


  • Anthropogenic emissions monitoring: ppq-level sensitivity for benzene, toluene, and xylenes.
  • OVOC detection: detection of oxygenated VOCs
  • Indoor air quality
  • Breath analysis

Instrument Versions

a. Resolving power at specified sensitivity. Each model can be operated with higher resolving
power at reduced sensitivity.