Microplastic Extraction from Digestive Tracts of Large Decapods

Abstract

The reliable quantification of microplastic contamination in chitinous organisms requires validated methods to remove interfering complex organic and inorganic material. This study trialled KOH, H2O2 and HNO3 digestion methods on the digestive tracts of two large decapods (Panulirus cygnus and Portunus armatus) to validate a protocol that facilitates reliable microplastic extraction. KOH digestion provided the best recovery (>95%) of ten polymer types, with the lowest impact to their physical morphology and chemical spectra. While HNO3, and HNO3 + H2O2 treatments were more effective at digesting chitin, they also destroyed polyamide, and altered several other polymers. High digestion efficiency of chitin did not result in high matrix clarification or high microplastic recovery for large decapods. This study emphasises the importance of validating species-specific microplastic separation methods, whilst proposing additional post-digestion protocols for complex samples, that can be applied in future research investigating plastic contamination in large decapods.

Keywords: chitin, crustacean, plastic contamination, KOH method, alkaline digestion, density separation