Best Practice Guide on the traceable measurement and characterisation of SMPs/NPs in food and environmental matrices

An international interlaboratory comparison (ILC) was organised in 2024, with statistic support provided by the Plastic Trace project, to validate ISO 16094-2: Water quality — Analysis of microplastics in water – Part 2: Vibrational spectroscopy methods for waters with low content of suspended solids including drinking water. Eleven laboratories from eight countries analysed three reference materials using μ(FT)IR and μRaman spectroscopy. Results were evaluated statistically according to ISO 5725-2 to assess repeatability, reproducibility, and recovery.The study showed that the ISO 16094-2 methodology delivers satisfactory performance under repeatability conditions, with robust recovery for particles ≥50 μm. However, reproducibility across laboratories remained limited, with significant variability for mixed-polymer and high-concentration samples. Measurements could be extended down to 20 μm, but with increased uncertainty, reflecting analytical challenges at smaller size ranges.Overall, the ILC provides the first systematic validation of ISO 16094-2. The results confirm its robustness for clean water analysis while highlighting the need for greater harmonisation of laboratory practices, improved operator training, and the development of reliable reference materials below 50 μm to strengthen reproducibility and comparability worldwide. “The project 21GRD07 PlasticTrace has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States.”• Funder name: European Partnership on Metrology• Funder ID: 10.13039/100019599• Grant number: 21GRD07 PlasticTrace