Identification and analysis of microplastics: a systematic review of methods and techniques

This systematic review was conducted to examine relationships between sample matrices and predominant analytical methods in microplastics research. An extensive literature search was performed across Springer, MDPI, and Scopus databases to identify relevant publications through October 2022. Through systematic screening, 180 studies were selected for full-text analysis. The reviewed methodologies revealed two primary sample preparation approaches: density separation and organic matter digestion. For organic matter digestion, oxidation using 30% hydrogen peroxide (H2O2) was identified as the predominant technique. In density separation protocols, zinc chloride (ZnCl2) emerged as the most frequently employed chemical compound. Regardless of the sample matrix, the main identification methods were Fourier transform infrared spectroscopy (µFTIR), µRaman and pyrolysis mass spectrometry (Pyr/GC–MS). The choice of methodology is heavily influenced by the sample matrix, however, other aspects are relevant, such as the type of material and concentration of organic matter in the sample. To address challenges in methodological standardization and result comparability, it is recommended that future studies be categorized according to identification method, as this parameter significantly influences the detectable size range of microplastics. Furthermore, density separation techniques should be carefully considered, as solution density may affect the recovery of higher-density polymers. Implementation of these methodological considerations could enhance the accuracy of comparative analyses regarding polymer types and particle size distributions in environmental microplastic samples. The findings suggest that while methodological approaches vary substantially, systematic classification of analytical protocols could facilitate more robust inter-study comparisons in microplastics research.