Environ. Sci. Nano http://doi.org/cq9x (2018)

Pollution from microplastics, particles of plastic smaller than 5 mm in size, poses a serious threat to a range of ecosystems. Due to their increased toxicity, it is important to make a distinction for nanoplastics with size ranging between a few tens and a few hundreds of nanometres. Nanoplastics are difficult to detect, so providing an estimate of their concentration, size and composition is challenging. More generally, there seems to be no real consensus on the methods used to identify and classify plastic particles of all sizes.

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Mintenig et al. now propose a general framework for the analysis of both micro- and nanoplastics. This framework consists of a sampling step to generate a density of particles high enough to be detected, a sizing step and an identification step to establish the type of polymers in the particles. For particles larger than 20 μm, common methods can be used for all three steps. For smaller particles, the team propose crossflow ultrafiltration, a method used in medical dialysis, for sampling. Asymmetrical flow field-flow fractionation can be used for sizing, and pyrolysis gas chromatographic-mass spectroscopy can be used for the identification of the composition.

The three steps were tested by using known nanoparticles as small as 50 nm in size. Though some improvements will be necessary, the results show that the proposed framework could indeed be used as a general method to quantify and analyse plastic particles of a wide range in size.