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Bringing the Advantages of the IMS-TOF to the Atmosphere

Ion mobility spectrometry–mass spectrometry (IMS–MS) for on- and offline analysis of atmospheric gas and aerosol species

J.E. Krechmer, et al.
Atmos. Meas. Tech., 2016, DOI:10.5194/amt-9-3245-2016

IMS-MS is rapidly being adopted by bioanalytical researchers. The promise of being able to quickly separate isomeric compounds is especially interesting for the fields of metabolomics and lipidomics where different isomers sometimes exhibit huge differences in biological activity.

Adding an IMS dimension to MS analyses could also be of major benefit for atmospheric measurements. There, researchers are often faced with the problem that many molecules from organic aerosols cannot be sufficiently well identified based on MS alone. Yet, these identifications, especially for isomeric molecules, are crucial for establishing chemical mechanisms that inform climate models.  IMS-MS instruments could consequently greatly improve the understanding of reactions in the atmosphere.

Taken together, the small size, robust construction, and high IMS resolving power of the TOFWERK IMS-TOF suggest an opportunity to bring the advantages of IMS-MS to the challenging research environments that are typical of atmospheric research.   Such capability is demonstrated by Krechmer et al. in their current paper in Atmospheric Measurement Techniques.

Elemental composition and molecular structure of organic species in ambient air were simultaneously characterized with a TOFWERK IMS-TOF that was run continuously for multiple weeks at a remote Alabama field site during the 2013 Southern Oxidant and Aerosol Study (SOAS) campaign.   The IMS-TOF data set yielded many exciting results, including differentiation of organosulfates derived from isomers of isoprene epoxydiols (IEPOX). Fragmentation of precursor ions by collisionally induced dissociation (CID) was used to validate MS peak assignments, elucidate structures of oligomers, and confirm the presence of the organosulfate functional group.

The gas and aerosol IMS–TOF data sets provide valuable chemical information that cannot be obtained from high resolution mass spectrometry alone.

Top: Aerial view of the SOAS field site in Brent, Alabama taken from a tower that was installed to sample air above the forest canopy.    The white trailers in the top half of the photo served as the laboratories.   Bottom:  A look inside one of the trailer laboratories.  Ambient outdoor air was directly sampled through inlets in the windows and walls.  Photos compliments of Jimenez Research Group, U of Colorado Atmospheric researchers from around the world brought instrumentation to the SOAS campaign for the measurement of many different types of chemical compounds.   Data were shared and inter-compared in order to understand the complex chemistry of the atmosphere in this region, where urban air masses mix with forest emissions.  The campaign included long-term measurements (3 to 5 weeks) from multiple ground sites and measurements from research aircraft flying over the region.