Thermal Desorption Ion Drift Chemical Ionization Mass Spectrometry for the Analysis of Secondary Organic Aerosols

Secondary organic aerosols (SOA) represent a large fraction of atmospheric particulate matter that affects air quality, climate, planetary energy balance, and human health on a global scale. Furthermore, SOA represent the most active area of atmospheric chemistry research. To develop accurate atmospheric models for the regulation of emissions and of control policies that address the SOA challenge, clear understanding of the SOA formation mechanisms is an urgent need. Currently, the knowledge of SOA formation mechanisms is limited by the lack of aerosol chemical composition data. We have developed a novel Thermal Desorption Ion Drift Chemical Ionization Mass Spectrometry (TD-ID-CIMS) platform that offers a new analytical alternative for the study of SOA from a broad size range.The success of the new TD-ID-CIMS instrument resides in the soft vaporization and ionization methods that preserve the chemical integrity of the components of SOA. We have applied the new system to the analysis commonly reported SOA precursors such as sulfuric acid, sulfates, aminium salts, organic acids, and chemically modified aerosols for nucleation to accumulation mode particles with sizes between 10-200 nm. We have established the limit of detection down to the picogram level and current work centers on chemically modified aerosols in laboratory studies. Future experiments aim to deploy the instrument for field measurements in urban centers. Considering that the new TD-ID-CIMS offers a versatile, robust, and sensitive platform for the quantitative and qualitative study of SOA, our results may generate new insight to draw solid conclusions regarding the chemical dynamics of SOA.