biostudies-literatureResch JSwiss National Science Foundation14318-14328https://www.ebi.ac.uk/biostudies/studies/S-EPMC11325657biostudies-literatureUnknown58(32)Secondary organic aerosol (SOA) represents a large fraction of atmospheric aerosol particles that significantly affect both the Earth's climate and human health. Laboratory-generated SOA or ambient particles are routinely collected on filters for a detailed chemical analysis. Such filter sampling is prone to artifactual changes in composition during collection, storage, sample workup, and analysis. In this study, we investigate the chemical composition differences in SOA generated in the laboratory, kept at room temperature as aqueous extracts or on filters, and analyzed in detail after a storage time of a day and up to 4 weeks using liquid chromatography coupled to high-resolution mass spectrometry. We observe significantly different temporal concentration changes for monomers and oligomeEnvironmental science & technologyProlonged Dark Chemical Processes in Secondary Organic Aerosols on Filters and in Aqueous Solution.PMC11325657200021_192192/1Kalberer MResch JLi KfalseProlonged Dark Chemical Processes in Secondary Organic Aerosols on Filters and in Aqueous Solution.Secondary organic aerosol (SOA) represents a large fraction of atmospheric aerosol particles that significantly affect both the Earth's climate and human health. Laboratory-generated SOA or ambient particles are routinely collected on filters for a detailed chemical analysis. Such filter sampling is prone to artifactual changes in composition during collection, storage, sample workup, and analysis. In this study, we investigate the chemical composition differences in SOA generated in the laboratory, kept at room temperature as aqueous extracts or on filters, and analyzed in detail after a storage time of a day and up to 4 weeks using liquid chromatography coupled to high-resolution mass spectrometry. We observe significantly different temporal concentration changes for monomers and oligome2024-01-01T00:00:00Z2024 Aug2025-04-19T14:50:43.442Z2025-04-19T14:50:43.442ZS-EPMC113256573907887510.1021/acs.est.4c01647