200 College Street
Jay G. Slowik
Research Scientist, Laboratory of Atmospheric Chemistry
Paul Scherrer Institute Switzerland
Mass spectrometry is a powerful tool for the analysis of aerosol composition. However, tradeoffs typically exist between the loss of chemical information due to thermal decomposition and/or ionization-induced fragmentation on the one hand, and lower time resolution and/or separated collection/analysis stages on the other. We address these issues through the development of an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF), which provides online, highly time-resolved measurements of aerosol composition without significant decomposition or fragmentation. Further, the EESI-TOF provides a versatile sampling/ionization framework, as by simply changing the composition of the primary spray and mass spectrometer polarity, the instrument can be configured to optimize detection of different organic fractions or water-soluble metals, while the sampling inlet can be configured to allow separate detection of the gas and particle phase. Two applications of the EESI-TOF are presented. First, we demonstrate rapid intra-particle decomposition reactions in secondary organic aerosol generated from the dark ozonolysis of α-pinene, as well as further reaction on the exposure of the aerosol to visible light. Second, we explore the sources and processes governing SOA composition in complex urban environments.