AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Isomer-resolved Chemical Characterization of the Particle-phase Oxidation Products of Indoor Emissions Using Gas Chromatography-Chemical Ionization Mass Spectrometry
CHENYANG BI, Graham Frazier, Jordan Krechmer, Wen Xu, Andrew Lambe, Megan Claflin, Brian Lerner, Manjula Canagaratna, John Jayne, Douglas Worsnop, Gabriel Isaacman-VanWertz, Virginia Tech
Abstract Number: 231 Working Group: Instrumentation and Methods
Abstract Oxidation of organic compounds emitted indoors produces hundreds or thousands of unique chemical components, both within and beyond the indoor environment into which they are emitted. The detailed arrangement of the atoms and structure of each individual compound (i.e. isomer-resolved composition) controls its chemical properties and effects. The substantial analytical challenge of characterizing this mixture has stymied a detailed understanding of chemical processes in indoor air. In this study, we developed a new instrument that quantifies known and previously unidentified compounds with resolution of individual isomers. A field‐deployable Thermal desorption Aerosol Gas chromatograph was coupled to a time-of-flight Chemical Ionization Mass Spectrometer (“TAG‐CIMS”) using iodide as a reagent. The column effluent was also split to a flame ionization detector, providing near-universal responses to all analytes, and an electron ionization mass spectrometer, providing molecular structural information through fragmentation. This instrument measures molecular formulas of unknowns alongside identifications of known compounds and precise quantification of all analytes. We present here detailed characterization of the particle-phase oxidation products of common indoor emissions (e.g. limonene) over hours to days of atmospheric oxidation (by OH and O3), with a focus on changes to particle composition as a function of aging. Furthermore, we present the directly measured sensitivity of the I- CIMS to a wide range of identified compounds and compare empirical sensitivity to currently adopted approaches to calibration (e.g. “voltage scanning”), yielding new insight into the capabilities and limitations of this reagent ion chemistry.