Abstract. The Filter Inlet for Gases and AEROsols (FIGAERO) is an inlet specifically
designed to be coupled with the Aerodyne High-Resolution Time-of-Flight
Chemical Ionization Mass Spectrometer (HR-ToF-CIMS). The FIGAERO-HR-ToF-CIMS
provides simultaneous molecular information relating to both the gas- and
particle-phase samples and has been used to extract vapour pressures (VPs) of
the compounds desorbing from the filter whilst giving quantitative
concentrations in the particle phase. However, such extraction of vapour
pressures of the measured particle-phase components requires use of
appropriate, well-defined, reference compounds. Vapour pressures for the
homologous series of polyethylene glycols (PEG)
((H-(O-CH2-CH2)n-OH) for n=3 to n=8), covering a range
of vapour pressures (VP) (10−1 to 10−7 Pa) that are
atmospherically relevant, have been shown to be reproduced well by a range of
different techniques, including Knudsen Effusion Mass Spectrometry (KEMS).
This is the first homologous series of compounds for which a number of vapour
pressure measurement techniques have been found to be in agreement,
indicating the utility as a calibration standard, providing an ideal set of
benchmark compounds for accurate characterization of the FIGAERO for
extracting vapour pressure of measured compounds in chambers and the real
atmosphere. To demonstrate this, single-component and mixture vapour pressure
measurements are made using two FIGAERO-HR-ToF-CIMS instruments based on a
new calibration determined from the PEG series. VP values extracted from both
instruments agree well with those measured by KEMS and reported values from
literature, validating this approach for extracting VP data from the FIGAERO.
This method is then applied to chamber measurements, and the vapour pressures
of known products are estimated.
A method for extracting calibrated volatility information from the FIGAERO-HR-ToF-CIMS and its experimental application
