AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Particle-phase Organic Peroxides; Where Are You?
RAN ZHAO, Christopher Kenseth, Yuanlong Huang, John Seinfeld, California Institute of Technology
Abstract Number: 254 Working Group: Aerosol Chemistry
Abstract Organic peroxides comprise a significant fraction of extremely low-volatility, highly oxygenated organic compounds in secondary organic aerosol (SOA). Analyses of particle-bound organic peroxides at the molecular level present a significant analytical challenge, due to their chemical instability and complexity. Recent applications of liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) techniques facilitated the detection of a large variety of particle-phase oxidation products, among which many were proposed to be organic peroxides. However, unambiguous assignment of functional groups using mass spectrometry is challenging, and unique analytical techniques must be employed to distinguish organic peroxides in complex chemical matrices. In this study, we have developed a novel LC-ESI-MS technique assisted by iodometry. Iodide ion (I-), in an acidic solution, selectively reduces organic peroxides (ROOR) to the corresponding alcohols (ROH). The application of iodometry so far has been limited to the determination of the total peroxide content which can be tracked with the UV absorption of I3- forming in the solution. In this study, iodometry is employed for the first time in molecular-level analyses of organic peroxides by coupling to an LC-ESI-MS technique, where mass spectrometric peaks that are converted by the iodometry treatment can be identified as organic peroxides. The characterization of this technique and its application to the water-soluble fraction of α-pinene SOA are presented. Our preliminary results imply that none of the major dimers detected by our LC-ESI-MS can be concluded as organic peroxides.