Efficient extraction of small microplastic particles from rat feed and feces for quantification

To date, microplastic is ubiquitously encountered in the environment. Studies analyzing micro -plastic in terrestrial ecosystems, including animal feces and feed, are few. Microplastic quanti-fication method validation and harmonization are not yet far developed. For the analysis of small microplastic, approximately <0.5 mm, extraction from organic and inorganic materials is fundamental prior to quantitative and qualitative analysis. Method validation, including recovery studies, are necessary throughout the analytical chain. In this study, we developed an optimized, efficient protocol with a duration of 72 h for the digestion of laboratory rat feed and feces. A combination of a mild acidic (H2O2 15%; HNO3 5%) and an alkaline treatment (10% KOH) dissolving the previous filter, followed by enzymatic digestion (Viscozyme (R) L) proved to be efficient for the extraction and identification of spiked polyamide (15-20 mu m) and polyethylene (40-48 mu m) from feed and feces samples from rats, showing high recovery rates. Extracted rat feces samples from an in vivo study in which Wistar rats were fed with feed containing micro -plastic were analyzed with pyrolysis-gas chromatography-OrbitrapTM mass spectrometry, quan-tifying recovered microplastic in rat feces in environmentally relevant concentrations. The presented three-step protocol provides a suitable, time and cost-effective method to extract microplastic from rat feed and feces.

Automated summary

Microplastic is widely present in the environment, but there are few studies on microplastic in terrestrial ecosystems. The validation and harmonization of microplastic quantification methods are not yet well developed. For small microplastic analysis (<0.5 mm), extraction from organic and inorganic materials is essential before quantitative and qualitative analysis. In this study, a three-step protocol was developed to efficiently extract microplastic from rat feed and feces, providing a suitable and cost-effective method.