Microplastic Release from Plastic Bottles - Comparison of Two Analytical Methodologies (SEM-EDX and mu-FTIR)

Plastic debris and microplastics (MPs) evolve into an urgent problem for environmental contamination; any ecosystems are subject to a sort of “plastic invasion”. Until now, many sources have been identified and nearly all the environmental compartments are subject to MP contamination. The detection of MPs is, in principle, relatively simple. However, due to their size, and especially when small sizes are considered (around 1 μm), it may be problematic. In literature, different analytical approaches such as micro-Fourier transform infrared spectroscopy (μ-FTIR) and RAMAN spectroscopy, were proposed. In this work, we compared μ-FTIR with Scanning electron microscopy coupled to Energy dispersive X-ray spectroscopy (SEM-EDX) for analysing MPs concentrations in single-use polyethylene terephthalate (PET) mineral water bottles. We further considered the release of MPs from the bottle upon exposure to mechanical stress (squeezing treatment; none, 1 min, 10 min). After bottles were exposed to the three treatments, water was filtered on a silver membrane. Subsequently, the filters were analysed by SEM-EDX and μ-FTIR. The first methodology showed the presence of an increasing number of particles in relation to the treatment, but this increase was not statistically significant and, in addition, most of them were not of plastic origin. In the water samples, only few particles of small size (<10 μm) were identified by their elemental composition as PET. In contrast, μ-FTIR analyses of replicates of samples analysed by SEM-EDX, showed a lower number of particles and none could be identified as PET (>10 μm). SEM-EDX technique showed a high analytical potential because of its resolution for small size MPs. It should be considered as additional analysis to support spectroscopic methods.