28 Apr 2023
 | 28 Apr 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Technical note: Effects of storage conditions on molecular-level composition of organic aerosol particles

Julian Resch, Kate Wolfer, Alexandre Barth, and Markus Kalberer

Abstract. A significant fraction of atmospheric aerosol particles, which affect both the Earth’s climate and human health, can be attributed to organic compounds and especially secondary organic aerosol (SOA). To better understand the sources and processes generating organic aerosol particles, detailed chemical characterization is necessary, and particles are often collected onto filters and subsequently analyzed by liquid chromatography mass spectrometry (LC-MS). A downside of such offline analysis techniques is the uncertainty regarding artefactual changes in composition occurring during sample collection, storage, extraction and analysis. The goal of this work was to characterize how storage conditions and storage time may affect the chemical composition of SOA generated from β-pinene and naphthalene, as well as from urban atmospheric aerosol samples. SOA samples were produced in the laboratory using an aerosol flow tube and collected on PTFE filters, whereas ambient samples were collected onto quartz filters with a high-volume air sampler. To characterize temporal changes of SOA composition, all samples were extracted and analyzed immediately after collection, but were also stored as aqueous extracts or as filters for 24 hours and up to 4 weeks at three different temperatures of +20 °C, -20 °C or -80 °C, to assess whether a lower storage temperature would be favorable. Analysis was conducted using ultra high-performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS). Both principal component analysis (PCA) and time series of selected compounds were analyzed to identify the compositional changes over time. We illustrate that the chemical composition of organic aerosols remained stable during low temperature storage conditions, while storage at room temperature led to significant changes over time, even at short storage times of only one day. This indicates that it is necessary to freeze samples immediately after collection, and this requirement is especially important when automated ambient sampling devices are used where filters might be stored in the device for several days before being transferred to a laboratory.

Julian Resch et al.

Status: open (until 09 Jun 2023)

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  • RC1: 'Comment on egusphere-2023-840', Anonymous Referee #1, 03 May 2023 reply

Julian Resch et al.


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Short summary
Detailed chemical analysis of organic aerosol is necessary to better understand their effects on climate and health. Aerosol samples are often stored for days to months before analysis. We examined effects of storage conditions (i.e., time, temperature and aerosol storage on filters or as solvent extracts) on composition and found significant changes in the concentration of individual compounds, indicating that sample storage can strongly affect the detailed chemical particle composition.