GC-APCI expands the analytical window for detection of large PAHs (> 24 ringed-carbons) in pyroplastics and other environmental matrices

Open waste burning, large-scale fires, and maritime disasters produce partially burnt plastic called ‘pyroplastic’ - a newly recognized form of plastic in the Anthropocene and potentially a significant and previously unrecognized source of microplastics in the environment. Chemical markers, compounds unique to pyroplastic, would provide a complementary method to appearance and physical properties for identifying pyroplastics in environmental samples. Recent work showed that pyroplastic can have significant quantities of parent polycyclic aromatic hydrocarbons (PAHs) up to 278 Da with unique distributions. Because of this enrichment, we considered whether large PAHs (> 24 ringed-carbons) could serve as chemical markers for pyroplastics. To address this, we developed a high-temperature gas chromatography atmospheric pressure ionization (GC-APCI) method, targeting large PAHs with molecular weights ranging from 314 to 424 Da, using tandem mass spectrometry (MS/MS).Method development was performed using National Institute of Standards and Technology standard reference materials (SRMs) previously characterized for PAHs greater than 302 Da. A PAH class-specific MS/MS acquisition scheme combined with a simple, generic microextraction provided sensitive and specific detection without the need for sample fractionation or cleanup. Pyroplastics collected during the 2021 M/V X-Press Pearl ship fire and plastic spill were analyzed. Semi-quantitative comparison shows that the pyroplastic samples contain over two orders of magnitude higher amounts of the total 16 large PAHs (≥ 24 ringed-carbons, 314 to 424 Da) than were found in unburnt plastic pellets, reflecting trends previously observed for parent PAHs up to 278 Da. Qualitative comparison of samples and SRMs revealed multiple potential candidates suitable for further study as markers of pyroplastics in complex environmental samples. An increased range of chemical markers for pyroplastics should prove helpful in monitoring efforts for air quality, waste management, micro-pyroplastic pollution, and fires at the forest-urban interface.