Optimization of an Analytical Protocol for the Extraction of Microplastics from Seafood Samples with Different Levels of Fat

Marine organisms are affected by the ubiquitous occurrence of microplastics (MPs) in the environment. Several protocols have been described to extract and quantify MPs in seafood, although their complex matrices, with high level of fat, can compromise the efficiency of MPs extraction. To solve this issue, the present study aimed to develop a detailed methodology suitable to process seafood samples with different levels of fat, namely fish and molluscs, from fresh and canned sources, including the immersive liquids from the cans. Sample digestion was tested using different solutions (10% KOH, 30% H₂O₂), temperatures (40 °C, 65 °C) and incubation times (24, 48, 72 h). For fat removal, three detergents (two laboratory surfactants and a commercial dish detergent) and 96% ethanol were tested, as well as the manual separation of fat. The methodology optimized in this study combined a digestion with 30% H₂O₂ at 65 °C, during 24 to 48 h, with a manual separation of the fat remaining after the digestion. All steps from the present methodology were tested in six types of polymers (PE-LD, PET, PE, AC, PS, and lycra), to investigate if these procedures altered the integrity of MPs. Results showed that the optimized methodology will allow for the efficient processing of complex seafood samples with different fat levels, without compromising MPs integrity (recoveries rate higher than 89% for all the polymers tested).