A New Approach to Speciation of the Organic Component of Atmospheric Aerosols

Real-time in situ analysis of the organic component of atmospheric aerosols has been hampered by the lack of analytical techniques that allow molecular speciation. We report here the application of a relatively new ambient ionization method, extractive electrospray ionization mass spectrometry (EESI-MS), to probe aerosols from various sources, including secondary organic aerosols (SOA) formed by the reaction of α-pinene with ozone. The mass spectra are compared to those of the same samples that were first collected on a filter, dissolved in the solvent and then analyzed by conventional ESI-MS. Although EESI-MS has been used to explore other systems such as aerosolized drugs, to the best of our knowledge this is the first instance of applying the technique to atmospherically relevant aerosols. This technique has the advantages of providing mass spectra that are characteristic of individual organic compounds, yet is carried out at ambient pressures and temperatures and does not require prior collection and/or extraction of particles. Results from different aerosol samples will be presented and potential applications to ambient aerosols discussed.