An analytical strategy for challenging members of the microplastic family: Particles from anti-corrosion coatings
Lars Hildebrandt, Marten Fischer, Ole Klein, Tristan Zimmermann, F. Fensky, A. Siems, Alan B. Zonderman, Elena Hengstmann, Torben Kirchgeorg, Daniel Pröfrock
Abstract
Potentially hazardous particles from paints and functional coatings are an overlooked fraction of microplastic (MP) pollution since their accurate identification and quantification in environmental samples remains difficult. We have applied the most relevant techniques from the field of microplastic analysis for their suitability to chemically characterize anti-corrosion coatings containing a variety of polymer binders (LDIR, Raman and FTIR spectroscopy, Py-GC/MS) and inorganic additives (ICP-MS/MS). We present the basis of a possible toolbox to study the release and fate of coating particles in the (marine) environment. Our results indicate that, due to material properties, spectroscopic methods alone appear to be unsuitable for quantification of coating/paint particles and underestimate their environmental abundance. ICP-MS/MS and an optimized Py-GC/MS approach in combination with multivariate statistics enables a straightforward comparison of the multi-elemental and organic additive fingerprints of paint particles. The approach can improve the identification of unknown particles in environmental samples by an assignment to different typically used coating types. In future, this approach may facilitate allocation of emission sources of different environmental paint/coating particles. Indeed, future work will be required to tackle various remaining analytical challenges, such as optimized particle extraction/separation of environmental coating particles. Potentially hazardous particles from paints and functional coatings are an overlooked fraction of microplastics (MPs) pollution. Paint and coating particles are of high ecotoxicological concern due to the elevated chemical toxicity compared with MPs of similar sizes. High concentrations of hazardous additives have been historically and are currently used to produce paint and coatings. Our findings indicate that most MP monitoring studies relying solely on spectroscopic techniques significantly underestimate the abundance of paint/coating particles in the environment. Considering the assumed higher toxicity compared to thermoplastic/regular MP particles of similar sizes, the results tend to raise concern.