The content of microplastics (MP) in the environment is constantly growing. Since the environmental relevance, particularly bioavailability, rises with decreasing particle size, the knowledge of the MP proportion in habitats and organisms is of gaining importance. The reliable recognition of MP particles is limited and underlies substantial uncertainties. Therefore spectroscopic methods are necessary to ensure the plastic nature of isolated particles, determine the polymer type and obtain particle count related quantitative data. In this study Curie-Point pyrolysis-gas chromatography-mass spectrometry combined with thermochemolysis is shown to be an excellent analytical tool to simultaneously identify and optionally quantify MP in environmental samples on a polymer specific mass related trace level. The method is independent of any mechanical preselection or particle appearance. For this purpose polymer characteristic pyrolysis products and their indicative fragment ions were used to analyze eight common types of plastics. Further aspects of calibration, recoveries, and potential matrix effects are discussed. The method is exemplarily applied on selected fish samples after an enzymatic-chemically pretreatment. This new approach with mass-related results is complementary to established FT-IR and Raman methods providing particle counts of individual polymer particles.

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Thermal methods are of increased relevance in the field of mass-related microplastics (MP) analysis on trace level.

Analysis of microplastics (MP) in environmental samples is an emerging field, which is performed with various methods and instruments based either on spectroscopy or thermoanalytical methods. In general, both approaches result in two different types of data sets that are either mass or particle number related. Depending on detection limits of the respective method and instrumentation the derived polymer composition trends may vary. In this study, we compare the results of hyperspectral Fourier-transform infrared (FTIR) imaging analysis and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) analysis performed on a set of environmental samples that differ in complexity and degree of microplastic contamination. The measurements were conducted consecutively, and on exactly the same sample. First, the samples were investigated with FTIR using aluminum oxide filters; subsequently, these were crushed, transferred to glass fiber filters, in pyrolysis cups, and measured via Py-GC/MS. After a general data harmonization step, the trends in MP contamination were thoroughly investigated with regard to the respective sample set and the derived polymer compositions. While the overall trends in MP contamination were very similar, differences were observed in the polymer compositions. Furthermore, polymer masses were empirically calculated from FTIR data and compared with the Py-GC/MS results. Here, a most plausible shape-related overestimation of the calculated polymer masses was observed in samples with larger particles and increased particle numbers. Taking into account the different measurement principles of both methods, all results were examined and discussed, and future needs for harmonization of intermethodological results were identified and highlighted.