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A standardized protocol for microplastic and non-synthetic microfiber extraction and µFTIR identification in elasmobranch gastrointestinal tissues
Original title: A standardized protocol for microplastic and non-synthetic microfiber extraction and µFTIR identification in elasmobranch gastrointestinal tissues
Summary
Scientists developed a reliable new method for extracting and identifying microplastics from shark and ray gut tissue, tackling the tricky fat- and tissue-dense makeup of these organs. The technique accurately recovered over 93% of test plastic particles and found that most contamination in real samples was actually tiny fibers—many from natural materials like cellulose, plus some plastics like PET and nylon. This matters because sharks and rays sit near the top of the ocean food chain, so better tools for tracking what they're ingesting can help researchers understand how microplastics move through seafood and potentially reach our plates.
Elasmobranch gastrointestinal tissues are a complex matrix for microplastic work: high in lipids, dense in connective tissue, and prone to losing small particles during handling. In this work, we developed a protocol that targets these problems. Tissue is digested in 20% (w/v) KOH at 40°C until the soft fraction dissolves (24-72 h); when organic residues persist, 30% (v/v) H₂O₂ is added until the solution clears to amber. The digest is then density-separated in 5 M NaCl, filtered through 1.2 µm glass fiber, sorted under a stereomicroscope, and identified by µFTIR-ATR. Validation on eight samples spiked with 100 polyethylene reference particles (50-500 µm) gave recoveries of 90-96% (mean 93.4 ± 2.06%); the procedural blank returned 97%. From the real samples, 172 particles were recovered, mostly fibers, with cellulose as the dominant material, alongside PET, acrylic, nylon, and polypropylene. Detection was reliable down to ∼150 µm by stereomicroscopy and ∼60-70 µm by µFTIR. The method is not designed for particles below 50 µm or polymers denser than the saline brine (∼1.2 g cm⁻³); because both require adapting the density step. Key features of the method:•Sequential KOH-H₂O₂ digestion handles the fat- and protein-rich matrix of shark and ray digestive tissue without altering common polymers.•Mean recovery of 93.4% on polyethylene-spiked samples (90-96%); 97% in procedural blanks.•µFTIR-ATR identification down to ∼60 µm, with a reliable visual sorting threshold of ∼150 µm.