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Characterization of a Fast-GC/Proton Transfer Reaction-Time of Flight Mass Spectrometer for ambient measurements of speciated BVOCs

This study aims at characterizing the coupling of a fast Gas Chromatograph (fast-GC) with a Proton Transfer Reaction-Time of Flight Mass Spectrometer (PTR-ToFMS) to perform speciated measurements of Biogenic Volatile Organic Compounds (BVOCs) in ambient air.

The SAGE department from IMT Lille Douai has a long experience in developing new types of instrumentation and new analytical procedures to better characterize the chemical composition of the troposphere. Field measurements of speciated BVOCs are currently performed with GC instruments but are limited to time resolutions of 30-90 minutes. While this is sufficient to monitor daily variations of BVOC concentrations, a faster time resolution would be beneficial to investigate the rapid oxidation chemistry involving these species.

Recently, the development of several chemical ionization mass spectrometry techniques has improved the coverage of atmospheric trace gases with a time resolution of less than one second. Of particular interest, PTR-ToFMS is now routinely used during intensive field campaigns to monitor low-molecular-weight hydrocarbons and the sum of large-molecular-weight BVOCs. The main drawback of this technique is its inability to speciate isobaric BVOCs (monoterpenes, sesquiterpenes), i.e. BVOCs exhibiting the same exact mass. In this project we propose to characterize a PTR-ToFMS instrument coupled to a fast-GC to perform speciated measurements of isobaric BVOCs at a time resolution of a few minutes.

The main objectives are to:
- improve a methodology to prepare standard mixtures of BVOCs (monoterpenes and sesquiterpenes)

- optimize the fast-GC/PTR-ToFMS operating conditions for ambient measurements of isobaric BVOCs

- quantify figures of merit (precision, accuracy, detection limits)

This work will ultimately help improving our knowledge on BVOC sources, their reactivity in ambient air, and their implication in the formation of secondary pollutants such as secondary organic aerosols.

Keywords: Atmospheric composition, gas chromatography, mass spectrometry, instrumentation

Workpackage of the Labex CaPPA: WP 1

Laboratory: SAGE (IMT Lille Douai)

Supervisor(s): Dr. Sébastien DUSANTER