Development and validation of an analytical pyrolysis method for determination of microplastic polymers in atmospheric aerosols

There is a need to develop analytical techniques for detection of airborne microplastic particles due to increasing evidence of their presence in ambient air and the associated possible health and climate effects. Current analytical methods are limited by particle size and subjective visual evaluation. We have tested and validated an analytical pyrolysis gas chromatography-mass spectrometry, py-GC-MS, method that was developed specifically for detection of micro- and nanoplastic particles in aerosol samples. Some of the most common polymers, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyurethane (PU), polyamide (PA) and polystyrene (PS), were mixed and analyzed in atmospherically relevant sample matrices. A temperature-ramped selected ion monitoring (SIM) method was developed to detect them, based on characteristic pyrolysis products identified in pyrograms of each polymer individually and in their mixtures. Calibration curves in the range 10 ng – 1 µg were determined for each polymer with R 2 values ranging from 0.72 to 0.99. A negative matrix effect was observed for reactive pyrolysis products, which was stronger in samples containing more aerosol matrix. This effect may be caused by secondary reactions between the pyrolysis products and aerosol matrix components. On the contrary a positive matrix effect was observed for PVC, possibly due to the addition of alkenes by the matrix which partake in radical reactions to form naphthalene. Deuterated polystyrene was tested as an internal standard to account for the matrix effect, but it was found to only be suitable for PS and PP. Other internal standards are thus needed for the other polymers. This study presents a method for direct analysis of aerosol particle samples with quantification of PP, PS, and PA on the nanogram scale and semi-quantification of PE, PU, PET, and PVC, also in the sub-microgram range. • Novel analysis method for atmospheric PE, PP, PVC, PET, PU, PA, and PS using direct py-GC-MS • Quantitative for PP, PA, and PS and semi-quantitative for PE, PU, PET, and PVC on the nanogram scale • Method validated for the polymers in aerosol matrix from candle emissions and urban PM 2.5 .