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Towards nanoplastic reference materials representative of partially degraded/naturally aged samples in complex food and environmental matrices
Summary
Researchers developed nanoplastic reference materials that better represent partially degraded and naturally aged particles found in real environmental and food matrices, addressing the inadequacy of commercially available monodispersed spherical particles that do not reflect the polydispersed, irregular morphology of environmental nanoplastics.
Microplastics (MPs) and nanoplastics (NPs) in the environment or food chain are extremely complex and predominantly composed of hydrocarbon polymers. This makes it very tricky to isolate and detect them in environmental and food matrices, which are already rich in carbon-based components. Moreover, almost all prior research on MPs/NPs have been based on commercially available particles that are monodispersed, spherical and coated with surfactants and stabilisers. In contrast, real MPs/NPs in the environment are polydispersed with undefined morphologies, highlighting the urgent need for truly representative reference materials. A number of research needs has been identified by the European Food Safety Agency (EFSA), the Science Advise for Policy by European Academies (SAPEA), and the WHO including the need to develop representative reference materials for plastic particles in different size range. In the frame of the Plastic Trace Project https://plastictrace.eu/ sub-micron plastic particles and NPs, representative of common industry polymers like polyethylene (PE) and polypropylene (PP), have been produced and characterised. The produced materials mimic particles in the environment according to size, shape and aging status. NanoPP and nanoPE were produced by crushing PP or PE pellets in acetone with following sieving/filtration. Ensuring homogeneity and stability in these suspensions is crucial for reliable reference materials, especially challenging for low-density PE or PP, which tend to float. Homogeneity and stability tests according to the size distribution and number concentration of particles were carried out after ISO 17034 and ISO Guide 35:2017 using dynamic light scattering (DLS) and particle tracking analysis (PTA). Moreover, the candidate reference materials were characterised using a selection of complementary techniques including Scanning Electron Microscopy (SEM) for shape, Pyrolysis coupled with Gas Chromatography Mass Spectrometry (Py-GC/MS) and Thermal Extraction and Desorption GC-MS (TED-GC/MS) for mass concentration, and Atomic Force Microscopy (AFM) and µ-Raman spectroscopy for particle number measurements. Also see: https://micro2024.sciencesconf.org/559355/document