Characterization of airborne PET nanoplastic particles using Aerosol mass spectrometry

Atmospheric nanoplastics (NPs) have emerged as a significant environmental concern, but knowledge about these emerging contaminants remains limited due to challenges associated with analytical techniques for detection and quantification. Aerosol mass spectrometry (AMS) has demonstrated potential to measure airborne NPs, but there is a need for a systematic assessment of its capability to measure NPs. Here we used polyethylene terephthalate nanoplastic particles (PET-NPs) as a proxy of NPs to investigate the ability of high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to determine monomeric composition and evaluate its sensitivity toward NPs. Different PET consumer products were used to generate PET-NPs under thermo-oxidation conditions, using either a 3D printer or a tube furnace. The relative ionization efficiency (RIE) of PET-NPs was determined to be around 0.75. The particle mass spectra observed by AMS under standard operating conditions reveal notable marker ions of emitted PET-NPs such as those at m/z 149 and 166. Upon comparing the particle composition data obtained from AMS with that from pyrolysis gas chromatography mass spectrometry, we note consistencies in the mass spectra between online and offline techniques, implying similar thermal decomposition and ion fragmentation mechanisms under electron ionization (EI) at the respective operating temperatures. No evidence of vaporization delay was observed for PET at the standard vaporization temperature (600 °C) of HR-ToF-AMS. The results of this study further inform the ability and limitations of using real time aerosol mass spectrometry to measure airborne NPs.