Validation of multi-step analytical protocols for microplastics detection in lipid-rich matrices

The increasing amount of microplastics (MPs) in the environment has raised serious concern about human exposure to MPs in food. Several methods have been developed to extract and detect MPs in food matrices. However, complex matrices, such as those rich in lipids, often require multiple pretreatment steps that, while not affecting the detection of other organic compounds, can lead to sample contamination and reduce recovery rates for MPs analysis. In addition, the presence of lipid material often inhibits filtration processes and compromises the potential chemical characterization of polymers by forming a lipid layer that can absorb radiation. Here, several multi-step analytical protocols were optimized and validated to extract and purify MPs from different lipid-rich matrices from species suitable for human consumption, such as eggs and fish. First, the lipid content of each matrix was evaluated by gravimetric analysis. Then the most suitable digestion method was evaluated, from basic oxidative digestion to more elaborate enzymatic processes. Recoveries and precision (RSD) were calculated using standards. In addition, the efficiency of the digestion treatment to remove lipid matter was estimated through the compatibility of using μFTIR spectroscopy to chemically characterize the spiked standards. Spectroscopic analysis also allowed the integrity of the polymers to be assessed after the digestion treatment. Quality assurance and quality control were assessed through the entire processes. With the ability to remove all interfering materials, it will be possible to characterize MPs and thus provide an accurate ecological risk assessment on edible species. The presence of MPs in food can pose a risk to human health and animal because of their potential bioaccumulation in organisms and their ability to act as a carrier for other toxic chemicals. Therefore, the validation of methods that accurately detect the presence of MPs in complex matrices such as food is crucial.