Quantification of micro- and nano-plastics in atmospheric fine particles by pyrolysis-gas chromatography-mass spectrometry with chromatographic peak reconstruction.

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The effects of micro- and nano-plastics (MNPs) on human health are of global concern because MNPs are ubiquitous, persistent, and potentially toxic, particularly when bound to atmospheric fine particles (PM2.5). Traditional quantitative analysis of MNPs by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) is often inaccurate because of false positive signals caused by similar polymers and organic compounds. In this study, a reliable analytical strategy combining HNO3 digestion and chromatographic peak reconstruction was developed to improve the precision of pyrolysis-gas chromatography-mass spectrometry analysis of multiple MNPs bound to PM2.5. The optimized HNO3 digestion method using high-pressure oxidation conditions effectively removed organic matter within two hours, giving recovery rates of 64 %-110 % for eight target MNPs. The chromatographic peak reconstruction procedure minimized interferences caused by similar polymers and achieved high accuracy (101 % ± 10 %) for polyvinyl chloride, polyethylene terephthalate, and polystyrene, whose concentrations are often overestimated due to overlapping pyrolysis products. Quantification uncertainties for MNPs in real PM2.5 samples were up to 52 % lower using the new method than using previous methods. The method was validated using PM2.5 from urban Guangzhou. The total concentrations of the eight target MNPs in the PM2.5 samples were 100-990 ng/m3 (median 277 ng/m3) and the dominant MNPs were polyethylene, polyethylene terephthalate, and polyvinyl chloride, which contributed > 90 % of the MNPs. The new method allows the robust and accurate quantification of MNPs in atmospheric fine particles and will be useful in future studies on the environmental behaviors of MNPs and risks they pose.