Organic matter removal in microplastic extraction from environmental samples: Challenges and methodological solutions

Accurate quantification and characterization of microplastics (MPs) in complex environmental samples is essential. Achieving this requires reliable protocols for extracting and isolating MPs from other matrix components that may interfere with analytical detection or hinder recovery. To address this need, this paper focuses on the removal of biogenic organic matter (OM), a major constituent of terrestrially derived environmental samples and water samples. We discussed how the interferences caused by OM, such as biofilms, algae, plankton, plant debris, and microbial residues, can reduce separation efficiency, clog filtration systems, overlap with MP signals in microscopy and spectroscopy, or introduce background noise in thermal analyses, ultimately leading to misidentification or false positives. To address these issues, a preparatory step involving the efficient removal of OM while minimizing alterations to the physicochemical properties of MP particles is essential. In this paper, we present a detailed discussion of various OM digestion methodologies and factors such as temperature and duration impacting their efficiencies. Moreover, the potential impacts of these methodologies on the MPs' physicochemical properties, such as surface chemistry and size distribution, are discussed. The most common methods involve oxidative, acidic, alkaline, and enzymatic digestions showed varied levels of OM removal efficiency. Integrating these approaches has shown to enhance OM digestion while minimizing damage to MPs, thereby offering optimized performances for diverse environmental samples while preserving polymer stability.