Microplastics (1 µm – 5 mm) and nanoplastics (<1 µm) have been identified as pollutants in all environmental matrices – and demands for documenting and monitoring environmental concentrations continue to increase.
Microplastic and nanoplastic analysis
To be able to robustly risk assess microplastic and nanoplastic pollution in the environment we need validated methods to accurately identify and quantify them in water, sediment, soils, biota and foodstuffs.
Microplastic and nanoplastic can be produced through the degradation of any polymer materials, including many consumer plastic products, synthetic textiles, paints/coatings and vehicle tyres. This also means that their chemical composition, especially at the surface, may be altered relative to the original polymer. This variety of physical and chemical properties poses a major challenge for identification and quantification, and no single instrument is able to identify and quantify both microplastic and nanoplastic.
Unique identification methods
Today, methods for microplastic analysis are relatively well established, but inter-laboratory harmonisation and quality assurance criteria remain to be finalised. SINTEF has a dedicated plastics laboratory and a team of highly qualified, internationally recognised researchers and technicians working on methods for the isolation and analysis of microplastic from complex environmental matrices (e.g. seawater, sediments and biota). We have a strong focus on quality assurance and quality control throughout the whole process, from sampling to analysis and final data.
Across SINTEF, we offer a range of characterization techniques that can be applied to microplastic and nanoplastic analysis. Most noteworthy are our µRaman and µFTIR instrumentation, both capable at both identifying, distinguishing and quantifying microplastic in the size ranges > 1µm and > 20 µm, respectively. In addition, we have a range of other instrumentation that can provide additional characterisation information, including particle size analysers and pyrolysis GC-MS (polymer identification, mass quantification and additive chemical profiling).
In contrast to microplastic analysis, nanoplastic analysis remains in the exploration stage. Their small size means they are non-detectable by optical techniques, while their particle nature means chemical analysis techniques are also very limited. Furthermore, their expected concentrations in environmental matrices are typically very low. SINTEF is strongly involved in the development of advanced, robust methods for the identification and quantification of nanoplastics in different matrices. Our primary tool is pyrolysis GC-MS, which can provide a mass-based quantification of different polymers present in a sample. We are currently developing a pipeline to combine size fractionation and characterization techniques such as field-flow-fractionation with mass-based quantification via pyrolysis-GCMS, which shows promise but remains technically challenging.
Microplastic and nanoplastic reference materials
The availability of high quality, well-characterised and environmentally relevant test and reference materials that accurately represent the microplastic and nanoplastic particles that are present in the natural environment are critical for validating the sample processing and analytical approaches used to identify and quantify them. Similarly, the availability of suitable reference materials are important for understanding how microplastic and nanoplastic behaves in the environment and how environmental matrices affect their detection. This is fundamental for quantifying exposures, assessing hazards and understanding their risk.
Such test and reference materials are challenging to produce, especially in the small microplastic and nanoplastic sizes. SINTEF is developing methods for the production of microplastic and nanoplastic test/reference materials for utilisation of fate and effects assessments and analytical protocol validation. We are working to develop feasible methods for producing relevant microplastic and nanoplastic test materials in sufficient quantities by using combinations of top-down processes such as mechanical degradation, UV degradation and partial dissolution. Importantly, we are trying to develop methods that retain the inherent additive chemical and non-intentionally added substance profiles of the plastic materials.
SINTEF also uses these lab-based degradation mechanisms to study the degradation and fate of plastic materials in the natural environment, linking this to advanced analysis for quantifying degradation and chemical composition changes.
These are examples of how SINTEF, together with industry and research partners, is contributing to the development of solutions that increase our understanding of plastic pollution. Furthermore, our research activity is contributing directly to national, regional and global level microplastic and nanoplastic monitoring and policy development.
