Assessing nano-particle composition using online filter-based TD-MION-Orbitrap

Understanding the role organic aerosols (OA) play in air quality, climate, and human health requires detailed knowledge of their chemical composition. For example, the volatility of OA is further a crucial piece of information in the handling of secondary organic aerosols (SOA) in atmospheric models. Various experimental approaches to assess the composition of aerosol particles have been developed (FIGAERO, VIA, etc.), but they all struggle with limited sensitivity, particularly at small particle sizes.

Here, we demonstrate a novel online filter-based system, leveraging the Thermal Desorption Multi-scheme chemical IONization inlet coupled to an Orbitrap mass spectrometer (TD-MION-Orbitrap). This system enables semi-continuous online measurements of the physicochemical properties of aerosol particles. Aerosol particles are collected onto stainless steel mesh filters positioned inside the thermal desorber unit. By adjusting the collection time, sufficient particle accumulation for analysis is ensured. The sample is then thermally desorbed at temperatures exceeding 300°C. The MION-Orbitrap provides reagent- and polarity-switching chemical analysis of the evaporated molecules at high sensitivity and mass resolution.

We describe the operating principles of this system and present results from laboratory experiments where organic and inorganic aerosol particles are produced, collected, desorbed and analysed with two different chemical ionization schemes. The quantitative performance of the system is also explored, and initial data from a field campaign further demonstrate the capability of this novel analytical technique to advance the characterization of aerosol particles.