Real-Time
Analysis of Ambient Organic Aerosols Using
Aerosol Flowing Atmospheric-Pressure Afterglow Mass Spectrometry (AeroFAPA-MS)
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Abstract
Organic
compounds contribute to a major fraction of atmospheric
aerosols and have significant impacts on climate and human health.
However, because of their chemical complexity, their measurement remains
a major challenge for analytical instrumentation. Here we present
the development and characterization of a new soft ionization technique
that allows mass spectrometric real-time detection of organic compounds
in aerosols. The aerosol flowing atmospheric-pressure afterglow (AeroFAPA)
ion source is based on a helium glow discharge plasma, which generates
excited helium species and primary reagent ions. Ionization of the
analytes occurs in the afterglow region after thermal desorption and
produces mainly intact quasimolecular ions, facilitating the interpretation
of the acquired mass spectra. We illustrate that changes in aerosol
composition and concentration are detected on the time scale of seconds
and in the ng m<sup>–3</sup> range. Additionally, the successful
application of AeroFAPA-MS during a field study in a mixed forest
region is presented. In general, the observed compounds are in agreement
with previous offline studies; however, the acquisition of chemical
information and compound identification is much faster. The results
demonstrate that AeroFAPA-MS is a suitable tool for organic aerosol
analysis and reveal the potential of this technique to enable new
insights into aerosol formation, growth, and transformation in the
atmosphere