In recent years, many different process steps and methods have been applied for micro- and nanoplastics (MNPs) analysis including sampling, sample preparation and detection, with the aim of covering a wide range of analytical tasks. Samples can have an easy-to-measure drinking water matrix, or they can have much more complex matrices such as sewage sludge, soil, compost, sediment or even food, blood or human tissues. Of equal complexity as the matrix are the varieties of MNP shapes, such as irregular fragments, spheres, or fibers, made from many different plastic material types. This complexity of matrices and MNPs leads to many different approaches being used for MNP analysis. But the results from different analytical methods mean that there are large gaps in harmonisation with respect to terminology, size classes, sample preparation protocols and, finally, to the comparability of the measurands and descriptors.

This CUSP working group compiles an overview of the existing detection methods revealing advantages and disadvantages regarding the analytical tasks. There is a clear need to develop high class characterized reference materials for MNPs in the size ranges of 100-10 µm and smaller than 10 µm, so that these can be used to validate methods and to make results comparable. Inter-laboratory comparisons (ILCs) on model samples with complex matrices regarding mass, or water samples for number-based methods, will help us to advance the process of harmonization as well as to train users early in process of developing new methods.

We plan to keep all five CUSP projects well-connected and to extract the optimum of needs, capabilities, and efforts in order to launch new ILCs which should expand already available ones.