Summary report on: The development of pristine SI traceable reference materials for SMPs (0.1 μm - 10 μm) and NPs (< 0.1 μm), representative of partially degraded/naturally aged samples in complex food and environmental matrices, and for realistic polydisperse size distributions and irregular shapes

This report describes the production and characterisation of SMPs and NPs reference material candidates produced in PlasticTrace. The particles should mimic particles in the environment according to size, shape and aging status. PlasticTrace is focussing on materials used in packaging that are either in direct food contact or can be found in the environment because of improper disposal or for example by spreading compost on the fields, where today a certain amount of plastic from shredded packaging may still be included as a by-product. The chosen polymers are PE and PP. These can degrade in the nature due to weathering conditions and will have an irregular shape with oxidized surface.The nanoPE and nanoPP were produced by crushing PE or PP pellets in acetone with following sieving/filtration and change of the solvent to water.PP (<10 μm) is also produced by crushing PP pellets but here in ethanol and under cooling in an ice bath. The particles are sieved and collected on a 1 μm filter, before dispersion in water with 1 mg/mL.Homogeneity and stability control is absolutely mandatory in order to be able to name the developed test materials as reference materials in the future. For this purpose, homogeneity and stability tests according to the size distribution and number concentration of particles are carried out according to ISO 17034 and ISO Guide 35:2017 “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