Development of a parallel sampling and analysis method for the elucidation of gas/particle partitioning of oxygenated semi-volatile organics : a limonene ozonolysis study
Résumé
Gas/particle partitioning behaviour of secondary organic matter semi-volatile fraction and the associated multiphase chemistry are key features to accurately evaluate secondary organic aerosol climate and health impacts. However, today, oxygenated secondary species partitioning is rarely assessed in experimental SOA studies and SOA modelling is still largely based on estimated partitioning data. This paper describes a new analytical approach, solvent free and easy to use, to explore the chemical composition of the secondary organic matter at a molecular scale in both gas and particulate phases. The method is based on thermal-desorption (TD) of gas and particulate samples, coupled with gas chromatography (GC) and mass spectrometry (MS), with on sampling supports derivatisation processes. Gaseous compounds are trapped on PFBHA or MTBSTFA pre-coated Tenax TA adsorbent tubes. Particulate samples are collected onto quartz or Teflon-quartz filters and subsequently exposed to PFBHA or MTBSTFA derivatisation reagents before TD-GC-MS analysis. Method development and validation are presented from an atmospherically relevant range of organic acids and carbonyl and hydroxyl compounds. Method application to a limonene ozonolysis experiment conducted in the EUPHORE simulation chamber under close-to-real conditions of low concentrations and relative humidity provides an overview of the method abilities. 25 compounds have been positively or tentatively identified, 9 being in both gaseous and particulate phases and 11, among them tri carboxylic acids, hydroxyl dicarboxylic acids and oxodicarboxylic acids, being detected for the first time.
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