Abstract View
Molecular Analysis of Freshly Nucleated α-pinene SOA Using Droplet Assisted Ionization
DEVAN E. KERECMAN, Murray Johnston, University of Delaware
Abstract Number: 321
Working Group: Instrumentation and Methods
Abstract
Droplet Assisted Ionization (DAI) is an inlet ionization technique that allows for online detection of intact molecular ions from airborne droplets. In our laboratory, DAI is used to perform online analysis of aerosol particles by passing the aerosol through a condensation growth chamber (CGC) to create micrometer-size aqueous droplets. DAI is performed by subsequently sending the droplets through a temperature-controlled capillary tube that serves as the inlet to a Waters SYNAPT G2-S mass spectrometer. Because the sensitivity of DAI analysis increases as the original aerosol particle diameter decreases, this method is particularly well suited to the study of nanoparticle formation and growth. In this presentation, experiments are reported where the molecular composition of freshly nucleated SOA is studied by DAI. In an initial experiment, SOA having a median diameter of 20 nm, a number concentration of 2 x104 cm-3, and a mass concentration of 0.25 µg m-3 produced signal with high ion intensity. Molecular characterization of the SOA was consistent with condensation of highly oxidized molecules (HOMs) that subsequently reacted within the particle phase. Further characterization of particle-phase chemistry is underway. The results have implications for understanding the relative roles of gas- vs. particle- phase processes that cause growth of newly formed particles.