Tropospheric Chemistry: VOC Instruments

Long Time-of-Flight Chemical Ionization Mass Spectrometer (LTOF-CIMS) with optional VOCUS Inlet for Aerosols (VIA) or Extractive Electrospray Ionization (EESI)

LTOF-CIMS: one instrument for VOC PM composition - partitioning - highly oxidized VOCs

Principle of the Measurement

Gas phase: Chemical ionization of VOCs in a VOCUS inlet via proton transfer with hydronium ions (H3O+) or ammonium ion (NH4O+) ligand-switching reactions and detection using a long time-of-flight mass spectrometer
Aerosol phase: The VOCUS Inlet for Aerosols (VIA) front end for thermal desorption of particles into the gas-phase for analysis using the VOCUS LTOF
Aerosol phase: The Extractive Electrospray Ionization (EESI) source is an atmospheric pressure interface for the detailed measurement of aerosol composition

Species Measured


Chemically detailed trace gas composition including small oxygenated compounds (PTR) or highly functionalized S/IVOCs and oxidized VOCs (NH4O+). The VIA and EESI sources measure individual aerosol constituents with a wide range of volatility and oxidation state.

Time Response

Gas phase: 10Hz
Aerosol phase VIA: 1Hz
Aerosol phase EESI: 1Hz



Field Projects

Secondary organic aerosol Chamber Experiments for Non-Traditional Species (SCENTS) 2022


Carsten Warneke, Matt Coggon, Chelsea Stockwell