Selection of suitable detection methods for microplastics

Abstract

The increasing occurrence of microplastics in environmental compartments such as water, soil, air, and food represents a growing challenge for environmental science and policy. Microplastics originate both from the degradation of larger plastic fragments and from the direct release of primary particles. They enter the environment through pathways such as wastewater, tire abrasion, and atmospheric transport, where they accumulate over long periods of time. Despite their ecological relevance, reliable detection and quantification of microplastics are hampered by methodological variability, the lack of standards, and heterogeneous sample matrices. The wide range of available analytical methods results in datasets that are not directly comparable, thereby limiting the interpretability of current assessments. The aim of this project is therefore to systematically document and evaluate existing measurement methods in order to support the development of standardized and practice oriented analytical approaches.

The analysis shows that a variety of sampling methods exist for the collection of microplastic samples, each of which is highly specialized and tailored to the respective environmental medium. In addition, different approaches to sample preparation are applied, likewise specific to the individual matrices, enabling the subsequent use of various analytical techniques depending on the respective research question. At the same time, it became evident that the issue of cross contamination is frequently neglected in many studies, particularly during the sampling stage. Due to insufficient documentation and inconsistent definitions of microplastics, studies are therefore in some cases difficult or even impossible to compare.

The study demonstrates that the lack of standardization remains a central challenge in microplastic analysis and significantly limits comparability between studies. Differences in sampling and detection methods indicate that no universal analytical strategy exists and that method selection must always be adapted to the research question, the sample matrix, and the particle size range of interest. The guidelines of the BMBF status paper (Braun, 2020) emphasize the importance of a uniform presentation of results and the separate reporting of particle number and mass, while conversions between these parameters should be avoided due to high associated uncertainties. Consistent quality control, particularly regarding preventing cross contamination during sampling (Cruz-Salas et al., 2023), is essential to obtain reliable results. The developed flowchart supports structured methodological decision making and contributes to transparency and comparability in microplastic related studies, but it does not replace detailed method planning.