AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
A Direct HO2 Measurement Method Using Chemical Ionization Mass Spectrometry (CIMS) for the Study of Peroxy Radical Fate
JAVIER SANCHEZ, David Tanner, Greg Huey, Nga Lee Ng, Georgia Institute of Technology
Abstract Number: 429 Working Group: Instrumentation and Methods
Abstract Secondary organic aerosols (SOA) make up a large fraction of ambient submicron aerosol. SOA composition and yields are strongly dependent on the fate of the alkyl peroxy radical (RO$_2).Traditional SOA chamber experiments have used hydrocarbon/NO$_x ratio as a proxy for RO$_2 fate or restricted RO$_2 fate in “high NO$_x” and “low NO$_x” experiments. However, such definitions do not capture the fate of RO$_2 radicals, limiting applicability of laboratory results to ambient conditions. Understanding of aerosol formation at atmospherically relevant RO$_2 fates requires measurements of HO$_2. However, HO$_2 measurements in SOA laboratory characterizations are rare and generally conducted by titration methods that convert HO$_2 to OH through NO additions. Such methods have been shown to suffer from significant positive artifacts. Here we demonstrate a direct method for the measurement of HO$_2 radicals using negative ion chemical ionization mass spectrometry (NI-CIMS). We will discuss instrument performance including sensitivity, accuracy, detection limit, and integration time. Sample ambient data collected in Atlanta will also be presented to demonstrate instrument capability.