Optimisation of Small Microplastic Extraction and Quantification from Marine Tissues

Microplastics are plastic particles that are generally explained as being between 1μm and 5mm. They can be manufactured as micron-sized which are the primary microplastics, and can be formed by the breakdown of macroplastics, which are the secondary microplastics. Once in the marine environment, they are readily available for organisms to consume and accumulate. To date, they are identified from the water column, sediments, and marine biota. Despite the dramatic increase in microplastic studies observed in the last decades, their extraction and quantification from marine organisms remain hindered by several factors, including the lack of standardised protocols and technical limitations, especially for extracting microplastics smaller than 5 μm. This work addresses key methodological gaps identified through a comprehensive review of existing studies that aimed to develop or optimise methods for microplastics extraction. We optimised key experimental parameters from existing extraction protocols to achieve complete digestion of the target tissue and efficient recovery of 1 µm microplastics, using Mytilus galloprovincialis as the model organism. Specifically, we refined the tissue-to-reagent ratio to ensure thorough digestion, followed by filtration and microplastic quantification using scanning electron microscopy. We also evaluated the addition of a catalyst during the chemical digestion phase, which improved digestion efficiency. Our results also highlight a tissue-specific digestion for the tested digestion agents. Preliminary results have shown promising recovery rates of microplastics. Its outcome will implement the plan outlined in the Marine Strategy Framework Directive 2008/56 by developing innovative solutions, such as enhanced analytical methods and technologies for detecting and measuring microplastics in biological tissues and the marine environment, to facilitate effective sea monitoring.