Lactose Tablets spiked with PET as suitable Microplastics reference material to support validation studies and quality control

Abstract

Method validation in the field of microplastics analysis is challenging due to a lack of suitable reference materials describing the property of interest. The EU-funded PlasticTrace project aims to overcome that gap by developing water-soluble tablets containing defined numbers and masses of polyethylene terephthalate (PET) particles. Tablets were produced by solid-phase dilution following a strict preparation protocol with additional quality control. Different batches containing different particle numbers and masses were prepared and tested down to the detection limits of the analytical methods: theoretical mass (determined number by µ-Raman): 0.2 µg (151), 18.5 µg (1764) and 400 µg (not measured). PET particles had a mean size of approximately 40 µm, ranging from 1 to 100 µm, and an irregular shape determined by laser diffraction and scanning electron microscopy. All measurements were performed in accordance with ISO 16094–2 and ISO/FDIS 16,094–3. The most accepted microplastics detection methods were applied for characterisation: µ-FTIR, µ-Raman, Py-GC/MS and TED-GC/MS. Homogeneity and stability tests were assessed in terms of mass by TGA. The PET particles in the tablets show homogeneity with a relative standard deviation of <20%. No significant changes were observed during 6 months of storage. The developed tablet production method was also applied for polyethylene microplastics to assess its transferability to another polymer type. These reference materials can help to fulfill the criteria of EU Commission for MP monitoring in drinking water and wastewater. © 2026 The Authors.