Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 12945-12959, 2016
https://doi.org/10.5194/acp-16-12945-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 Oct 2016
A novel framework for molecular characterization of atmospherically relevant organic compounds based on collision cross section and mass-to-charge ratio
Xuan Zhang1, Jordan E. Krechmer2,3, Michael Groessl4, Wen Xu1, Stephan Graf4, Michael Cubison4, John T. Jayne1, Jose L. Jimenez2,3, Douglas R. Worsnop1, and Manjula R. Canagaratna1 1Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, MA 01821, USA
2Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA
3Cooperative Institute for Research in Environmental Sciences, Boulder, CO 80309, USA
4TOFWERK, 3600 Thun, Switzerland
Abstract. A new metric is introduced for representing the molecular signature of atmospherically relevant organic compounds, the collision cross section (Ω), a quantity that is related to the structure and geometry of molecules and is derived from ion mobility measurements. By combination with the mass-to-charge ratio (mz), a two-dimensional Ω − mz space is developed to facilitate the comprehensive investigation of the complex organic mixtures. A unique distribution pattern of chemical classes, characterized by functional groups including amine, alcohol, carbonyl, carboxylic acid, ester, and organic sulfate, is developed on the 2-D Ω − mz space. Species of the same chemical class, despite variations in the molecular structures, tend to situate as a narrow band on the space and follow a trend line. Reactions involving changes in functionalization and fragmentation can be represented by the directionalities along or across these trend lines, thus allowing for the interpretation of atmospheric transformation mechanisms of organic species. The characteristics of trend lines for a variety of functionalities that are commonly present in the atmosphere can be predicted by the core model simulations, which provide a useful tool to identify the chemical class to which an unknown species belongs on the Ω − mz space. Within the band produced by each chemical class on the space, molecular structural assignment can be achieved by utilizing collision-induced dissociation as well as by comparing the measured collision cross sections in the context of those obtained via molecular dynamics simulations.

Citation: Zhang, X., Krechmer, J. E., Groessl, M., Xu, W., Graf, S., Cubison, M., Jayne, J. T., Jimenez, J. L., Worsnop, D. R., and Canagaratna, M. R.: A novel framework for molecular characterization of atmospherically relevant organic compounds based on collision cross section and mass-to-charge ratio, Atmos. Chem. Phys., 16, 12945-12959, https://doi.org/10.5194/acp-16-12945-2016, 2016.
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Short summary
We develop a novel two-dimensional space to probe the molecular composition of atmospheric organic aerosols.
We develop a novel two-dimensional space to probe the molecular composition of atmospheric...
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