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. Secondary organic aerosols (SOAs) play a key role in climate change and airquality. Determining the fundamental parameters that distribute organiccompounds between the phases is essential, as atmospheric lifetime andimpacts change drastically between the gas and particle phase. In this work,gas-to-particle partitioning of major biogenic oxidation products wasinvestigated using three different aerosol chemical characterizationtechniques. The aerosol collection module, the collection thermal desorption unit, and thechemical analysis of aerosols online are different aerosol sampling inlets connected to a proton-transfer reaction time-of-flightmass spectrometer (ACM-PTR-ToF-MS, TD-PTR-ToF-MS, and CHARON-PTR-ToF-MS, respectively, referred to hereafter asACM, TD, and CHARON). These techniqueswere deployed at the atmosphere simulation chamber SAPHIR to performexperiments on the SOA formation and aging from different monoterpenes( β -pinene, limonene) and real plant emissions (Pinus sylvestris L.). The saturation massconcentration C* and thus the volatility of the individual ions wasdetermined based on the simultaneous measurement of their signal in the gas and particle phase. A method to identify and exclude ions affected by thermal dissociationduring desorption and ionic dissociation in the ionization chamber of theproton-transfer reaction mass spectrometer (PTR-MS) was developed and tested for each technique. Narrow volatilitydistributions with organic compounds in the semi-volatile (SVOCs – semi-volatileorganic compounds) tointermediate-volatility (IVOCs – intermediate-volatility organic compounds) regime were found for all systems studied.Despite significant differences in the aerosol collection and desorptionmethods of the proton-transfer-reaction (PTR)-based techniques, a comparison of the C* values obtainedwith different techniques was found to be in good agreement (within 1 orderof magnitude) with deviations explained by the different operatingconditions of the PTR-MS. The C* of the identified organic compounds were mapped onto thetwo-dimensional volatility basis set (2D-VBS), and results showed a decrease in C* with increasing oxidation state. For all experiments conducted inthis study, identified partitioning organic compounds accounted for20–30 % of the total organic mass measured from an aerosol mass spectrometer (AMS). Furthercomparison between observations and theoretical calculations was performedfor species found in our experiments that were also identified in previouspublications. Theoretical calculations based on the molecular structure ofthe compounds showed, within the uncertainties ranges, good agreement withthe experimental C* for most SVOCs, while IVOCs deviated by up to a factor of300. These latter differences are discussed in relation to two mainprocesses affecting these systems: (i) possible interferences by thermal andionic fragmentation of higher molecular-weight compounds, produced byaccretion and oligomerization reactions, that fragment in the m∕z rangedetected by the PTR-MS and (ii) kinetic influences in the distributionbetween the gas and particle phase with gas-phase condensation, diffusion inthe particle phase, and irreversible uptake.

Gas-to-particle partitioning of major biogenic oxidation products: a study on freshly formed and aged biogenic SOA