Sample Preparation of Seafood for Microplastic Analysis: A Challenge at Every Step
Sample Preparation of Seafood for Microplastic Analysis: A Challenge at Every Step
Spotlight on André Marcel Bienfait
Microplastics (MPs) are widespread in the marine environment, while their potential impacts remain an important area of scientific investigation. Questions related to particle toxicity, plastic additives, the potential transport of organic pollutants or heavy metals, and interactions with pathogens all contribute to the need for reliable methods to detect and characterise microplastics in marine samples.
Yet, when analysing microplastics in seafood, one of the greatest challenges begins long before the sample reaches an analytical instrument.
At the InPlasTwin Summer School 2026, André Marcel Bienfait presented “Sample preparation of seafood for the analysis of MPs – a challenge in every step”, highlighting how sampling, contamination control, matrix digestion, filtration, quality control and analytical choices can all influence the reliability of the final result.
Start with the research question
Before collecting a biological sample, researchers need to be clear about what they actually want to investigate. For food-safety studies, the question may concern microplastics present in the edible parts of seafood. Ecotoxicological studies, on the other hand, may focus on tissues such as gills or on stomach contents to understand exposure and potential effects on the organism. This distinction is important because the research question determines what should be sampled, how the sample should be prepared and ultimately how the results should be interpreted.
Contamination can occur at every stage
One of the particular difficulties of microplastic research is that plastic is also present throughout our everyday environment. Sampling equipment, fishing nets, clothing, laboratory equipment, cutting boards, knife handles and storage containers can all potentially introduce contamination. Completely eliminating plastic from sampling and laboratory procedures is often unrealistic. The practical approach is therefore to minimise potential contamination wherever possible and carefully document unavoidable sources. Glassware and aluminium trays can replace plastic containers in many situations, while blanks and rigorous cleaning procedures provide important controls. Where certain materials cannot be avoided, this also needs to be considered when interpreting the analytical results. Contamination control continues inside the laboratory. Dedicated working areas, HEPA-filtered air and laminar airflow benches can help reduce airborne contamination. But even clean-room environments present a paradox: many materials designed for clean rooms are themselves made of plastic.
This makes contamination control not a single step, but a principle that needs to be applied throughout the entire analytical workflow.
The central challenge: removing biological material without losing the plastic
Seafood is a particularly complex matrix. Before microplastics can be analysed, biological tissue needs to be removed while keeping the target plastic particles as intact as possible. This creates a difficult methodological trade-off. Enzymatic digestion is relatively mild and can preserve most microplastics, but it can take one to two weeks, involve several procedural steps and be costly. Chemical digestion is considerably faster, often one or two days, and can therefore be more suitable for applications involving larger numbers of samples. However, harsher chemical conditions can damage certain polymers. There is therefore no simple “one method fits all” solution. Marine biological tissues differ considerably in their chemical composition and digestibility. Acidic methods can digest tissue effectively but may damage sensitive polymers; oxidative approaches may be less damaging to polymers but less effective at removing the matrix; and enzymatic methods are gentle but time-consuming.
Moving towards methods suitable for food-safety monitoring
A key part of the work presented at the Summer School addressed exactly this challenge. The aim was to develop an analytical procedure applicable to fish fillets, fish liver and marine oils, with the capacity to process sufficiently large numbers of samples for food-safety monitoring. Another important requirement was to use sample quantities capable of addressing sample inhomogeneity while maintaining polymer integrity and achieving acceptable recoveries for relevant microplastics down to 10 µm. Published acidic, oxidative, enzymatic and alkaline protocols were compared using salmon muscle. All showed limitations related either to slow filtration or insufficient digestion. The best performance was obtained with newly developed protocols combining potassium hydroxide (KOH) and surfactants. The use of surfactants was particularly relevant for challenging fatty matrices. In marine oil samples, KOH treatment alone could produce a viscous gel that was difficult to filter, whereas adding surfactants substantially reduced viscosity and made filtration possible. This illustrates why sample preparation cannot simply be treated as a preliminary technical step. The chemistry of the matrix, the behaviour of the polymers and even filtration performance need to be considered together when designing a robust analytical workflow.
Quality control remains a major challenge
Reliable microplastic analysis also depends on appropriate quality-control procedures. Air blanks can help assess environmental contamination, while procedural or method blanks follow the entire analytical procedure without the sample matrix. Recovery experiments using relevant polymers and particle-size ranges provide additional information about method performance.
However, important limitations remain. As highlighted in the presentation, there are very few commercial standards for microplastic analysis, no certified reference materials, and substantial variation can occur between laboratories. These limitations make comparison and harmonisation of results particularly challenging.
From sample preparation to reliable evidence
Modern analytical techniques provide increasingly powerful possibilities for microplastic research. Approaches discussed during the presentation included pyrolysis-GC-MS, infrared spectroscopy and Raman spectroscopy, each providing different types of information and operating across different particle-size ranges. But sophisticated instrumentation alone cannot guarantee reliable results. If contamination is introduced during sampling, if biological material is incompletely removed, if certain polymers are damaged during digestion, or if quality-control procedures are insufficient, the final measurement may not accurately represent the original sample.
The key message is therefore simple but important: in microplastic analysis, every step matters.
Developing robust, reproducible and comparable sample-preparation procedures will be essential if microplastic research is to move from individual studies towards reliable monitoring approaches that can support food-safety assessment and environmental decision-making.
About the expert
André Marcel Bienfait presented “Sample preparation of seafood for the analysis of MPs – a challenge in every step” during the InPlasTwin Summer School 2026. He is a Senior Researcher at the Institute of Marine Research (IMR), Section for Contaminants and Biohazards, in Bergen, Norway. His work interests include method development for the analysis of micro- and nanoplastics, as well as inorganic nanoparticles, in seafood and environmental samples, particularly marine sediments. Within the Horizon Europe twinning project InPlasTwin, he is the leader of Work Package 5 – Knowledge exchange in analytical techniques for the MNPs detection. The presentation also acknowledged contributions from Tanja Kögel, Fred Olav Libnau, Jennifer Gjerde, Ørjan Bjorøy, Bjørn Einar Grøsvik, Stepan Boitsov and other colleagues.