Development of Standardized Methods to Extract and Digest Microplastics in Environmental Samples

The contamination of environments by microplastics has been extensively documented; however, the absence of standardized and effective extraction and digestion methods presents a substantial challenge for accurate evaluation. This study addressed this gap by testing four commonly found microplastics (PET, PVC, PS, and PP) to develop microplastic extraction and digestion methods that preserve their integrity during analysis. A total of 72 tests of extraction and digestion methods were examined, incorporating variations in chemical agents, exposure durations, and conditions. For extraction, density separation using sodium hydroxide, zinc chloride, potassium iodide, and sodium bromide was examined over two exposure durations (4 and 72 h). Hydrogen peroxide was applied for digestion over three exposure durations (24, 72, and 10 days), while Fenton's reagent was applied for 24 and 72 h. Significant variations in the physicochemical properties of plastics were observed because of various density separation and digestion methods. Potassium iodide and zinc chloride caused noticeable changes in PET, while PS was more affected by the digestion methods. This study offers a foundational understanding of how different methods affect microplastic integrity and provides practical guidance for selecting suitable chemical agents and conditions.