Microplastics in Water: A Comparative Review of Sampling, Sample Preparation, and Analytical Identification Methods

Environmental contamination by microplastics is closely associated with the widespread use of plastics. However, reliable assessment of this problem remains challenging because of the lack of fully harmonized definitions and considerable variability in analytical procedures. This review critically compares the procedures used for the collection, preparation, and identification of microplastics in water samples. The review is based on literature identified through searches in the Scopus and Web of Science databases using keywords related to microplastics, aquatic environments, sample preparation, separation procedures, and analytical identification methods. The analysis primarily covers recent publications from 2023–2026, supplemented by earlier studies that provide foundational methodological background. Particular attention is paid to filtration, organic matter removal, density separation, particle transfer, and identification using optical microscopy, Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and thermal methods. The comparison shows that mesh and filter size, separation-solution density, digestion conditions, and manual handling may affect particle recovery and preservation, while weathering, biofilms, pigments, and additives may hinder polymer identification. No single universal procedure is therefore suitable for all studies. Reliable and comparable results require combining morphological and chemical information, reporting analytical conditions in detail, and adapting the analytical workflow to the particle-size range and study objective.