Volatile organic compounds as fingerprints for identifying marine plastics

The increase in global marine plastic pollution highlights the need for more advanced yet simplified methods of plastic analysis. This study investigated the potential of volatile organic compounds (VOCs) emitted from plastics as fingerprints for plastic identification. Selected ion flow tube-mass spectrometry was used to conduct real-time analysis of VOCs emitted from heated (20-80 °C) pellets of plastic types commonly encountered in marine environments, including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), expanded polystyrene (EPS), and poly(ethylene terephthalate) (PET). VOCs consistently reflected the compositional characteristics of each plastic type: alkanes, characterised by their monomer units, were dominant in LDPE, HDPE, and PP; aromatics were prevalent in EPS; and ethylene glycol was observed in PET. The concentrations of these components varied with temperature, reflecting their unique thermal properties. A tiered classification model employing partial least squares discriminant analysis based on key mass fragment ions of emitted VOCs successfully distinguished among polymer types, achieving 100 % accuracy in determination of plastic products. This novel approach offers a simplified plastic polymer identification method, demonstrating that the chemical signatures of VOCs emitted from plastics can serve as unique and reliable fingerprints.