Development and Validation of an Efficient Method for Processing Microplastics in Biota Samples

The impacts of microplastics on aquatic ecosystems and biota are gaining attention globally. Although microplastics have been widely detected in biota, there currently are few standardized detection and identification methods. The present study developed a novel one-step digestion method which was evaluated with mussel and fish samples. This method employed nitric acid and hydrogen peroxide (HNO₃ :H₂ O₂ = 4:1 by volume) as digestion reagents, which completely digested biota samples <5 g weight within 30 min at 50 °C. A density separation step was subsequently used to remove organic residues as necessary. The efficiency and suitability of this method were tested by spiking microplastics of 7 different types and of various sizes (1000, 900, 675, 300, 250, and 150 μm) into mussel and gastrointestinal tracts of fish. The recoveries of microplastics ranged from 90 to 100%. No significant changes in weight, surface area, and particle size (t test, p > 0.05) were observed for all tested polymers. Fourier transform infrared spectral analyses demonstrated that the method did not degrade any of the polymers except for polyethylene terephthalate. The method was demonstrated with mussel and fish samples collected from the Pearl River delta, south China, and was able to recover microplastics effectively. Overall, the present method is time-saving and easy to operate, with low procedural cross-contamination. The properties of microplastics recovered by the present method remained largely intact, greatly benefiting subsequent qualitative and quantitative analyses. Environ Toxicol Chem 2019;38:1400-1408. © 2019 SETAC.