Focal plane array detector-based micro-Fourier-transform infrared imaging for the analysis of microplastics in environmental samples

The pollution of the environment with microplastics (plastic pieces ,5 mm) is a problem of increasing concern. However, although this has been generally recognised by scientists and authorities, the analysis of microplastics is often done by visual inspection alone with potentially high error rates, especially for smaller particles. Methods that allow for a fast and reliable analysis of microplastics enriched on filters are lacking. Our study is the first to fill this gap by using focal plane array detector-based micro-Fourier-transform infrared imaging for analysis of microplastics from environmental samples. As a result of ouriteratively optimised analytical approach (concerningfilter material, measuring mode, measurement parameters and identification protocol), we were able to successfully measure the whole surface (>10-mm diameter) of filters with microplastics from marine plankton and sediment samples. The measurement with a highlateralresolutionallowedforthedetectionofparticlesdowntoasizeof20mminonlyafractionalpartoftimeneeded for chemical mapping. The integration of three band regions facilitated the pre-selection of potential microplastics of the ten most important polymers. Subsequent to the imaging the review of the infrared spectra of the pre-selected potential microplastics wasnecessaryforaverificationofplastic polymerorigin.Theapproachwepresenthereishighlysuitableto be implemented as a standard procedure for the analysis of small microplastics from environmental samples. However, a further automatisation with respect to measurement and subsequent particle identification would facilitate the even faster and fully automated analysis of microplastic samples. Additional keywords: microplastic analysis, microplastic detection, microplastic identification.