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Title: Application of chemical derivatization techniques combined with chemical ionization mass spectrometry to detect stabilized Criegee intermediates and peroxy radicals in the gas phase
Abstract. Short-lived highly reactive atmospheric species, such as organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), play an important role in controlling the oxidative removal and transformation of many natural and anthropogenic trace gases in the atmosphere. Direct speciated measurements of these components are extremely helpful for understanding their atmospheric fate and impact. We describe thedevelopment of an online method for measurements of SCIs and RO2 inlaboratory experiments using chemical derivatization and spin trappingtechniques combined with H3O+ and NH4+ chemicalionization mass spectrometry (CIMS). Using chemical derivatization agentswith low proton affinity, such as electron-poor carbonyls, we scavenge allSCIs produced from a wide range of alkenes without depleting CIMS reagentions. Comparison between our measurements and results from numericmodeling, using a modified version of the Master Chemical Mechanism, showsthat the method can be used for the quantification of SCIs in laboratoryexperiments with a detection limit of 1.4×107 molecule cm−3for an integration time of 30 s with the instrumentation used in this study. Weshow that spin traps are highly reactive towards atmospheric radicals andform stable adducts with them by studying the gas-phase kinetics of thereaction of spin traps with the hydroxyl radical (OH). We also demonstrate that spin trapadducts with SCIs and RO2 can be simultaneously probed and quantified under laboratory conditions with a detection limit of 1.6×108 molecule cm−3 for an integration time of 30 s for RO2 species with the instrumentation used in this study. Spin trapping prevents radical secondary reactions and cycling, ensuring that measurements are not biased by chemical interferences, and it can be implemented for detecting RO2 species in laboratory studies and potentially in the ambient atmosphere.  more » « less
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Journal Name:
Atmospheric Measurement Techniques
Page Range / eLocation ID:
2501 to 2513
Medium: X
Sponsoring Org:
National Science Foundation
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