Selection of Suitable Detection Methods for Microplastics in Soil—A Decision-Making Flowchart

The increasing occurrence of microplastics in environmental compartments such as water, soil, air, and food represents a growing challenge for environmental science and policy. Despite their ecological relevance, the 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 review is therefore to systematically document and evaluate existing measurement methods for MPs in soil samples in order to support the development of standardized and practice-oriented analytical approaches. All fundamental operating principles of the analytical instruments—spectroscopic (Fourier Transform Infrared Spectroscopy (FTIR), Near-Infrared Spectroscopy (NIR) and Raman Spectroscopy), thermoanalytical (Pyrolysis–Gas Chromatography–Mass Spectrometry (Py-GC/MS), Thermal Extraction–Desorption Gas Chromatography–Mass Spectrometry (TED-GC-MS), and Differential Scanning Calorimetry—DSC), imaging, (Light Microscopy and Scanning Electron Microscopy—SEM), and fluorescence-based methods—are analyzed in details and compared. Our analysis shows that consistent quality control, particularly regarding preventing cross contamination during sampling, 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.