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Published February 20, 2018 | Supplemental Material
Journal Article Open

Iodometry-Assisted Liquid Chromatography Electrospray Ionization Mass Spectrometry for Analysis of Organic Peroxides - an Application to Atmospheric Secondary Organic Aerosol


Organic peroxides comprise a significant fraction of atmospheric secondary organic aerosol (SOA). Detection and quantification of particle-phase organic peroxides are highly challenging, and current efforts rely significantly on filter extraction and offline mass spectrometry (MS). Here, a novel technique, iodometry-assisted liquid chromatography electrospray ionization mass spectrometry (iodometry-assisted LC-ESI-MS), is developed and evaluated with a class of atmospherically relevant organic peroxides, α-acyloxyalkyl hydroperoxides, synthesized via liquid ozonolysis. Iodometry-assisted LC-ESI-MS unambiguously distinguishes organic peroxides, compensating for the lack of functional group information that can be obtained with MS. This technique can be versatile for a wide spectrum of environmental analytical applications for which a molecular-level identification of organic peroxide is required. Here, iodometry-assisted LC-ESI-MS is applied to the water-soluble organic carbon (WSOC) of α-pinene SOA. Unexpectedly, a limited number of detectable compounds in WSOC appear to be organic peroxides, despite the fact that spectroscopy-based iodometry indicates 15% of WSOC mass is associated with organic peroxides. This observation would be consistent with decomposition of multifunctional organic peroxides to small peroxides that can be quantified by spectroscopy-based iodometry but not by LC-ESI-MS. Overall, this study raises concerns regarding filter extraction-based studies, showing that assignment of organic peroxides solely on the basis of MS signatures can be misleading.

Additional Information

© 2018 American Chemical Society. Received: September 20, 2017; Revised: January 10, 2018; Accepted: January 25, 2018; Published: January 25, 2018. The authors thank Dwight and Christine Landis for their generous contribution to the CPOT, Prof. Paul Wennberg for helpful discussion, Dr. John Crounse for assistance with UV–vis measurements, and Dr. Michelle Kim for the synthesis of methylhydroperoxide. LC-ESI-MS and TOC analyses were performed in the Environmental Analysis Center (EAC). This work was supported by National Science Foundation Grants AGS-1523500 and CHE-1508526. R.Z. also acknowledges support from a Natural Science and Engineering Research Council of Canada Postdoctoral Fellowship (NSERC-PDF). The authors declare no competing financial interest.

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