Microplastics and nanoplastics released by peeling off aluminium foil cap sealing liner.

Most of our food, drinks, medicines, health care products and cosmetics are bottled for delivery and sealed using aluminium foil liner that is coated with a plastic layer. Once we open it by peeling off the liner, some debris might be released as microplastics that are tested here. By advancing the Raman imaging and the statistical analysis, we can capture ∼25 microplastics per 0.04 mm2 or ∼625 / mm2, particularly when scratch or scrape the container or liner surface, which might be a big concern as the potential microplastic source in our daily lives. The traditional analysis based on a homogenised sample such as an aqueous solution might generated bias for microplastics that is neither ion nor molecule. The subsequent point analysis via a single spectrum can be improved to imaging analysis via a hyper spectrum matrix that can contain hundreds-to-thousands of spectra / points (as pixels in the image) to enhance the signal-to-noise ratio. Raman imaging analysis can be further improved by algorithm to effectively decode the hyper spectrum matrix, to separately image the background and the targeted item. The generated images can identify and visualise microplastics towards quantification analysis. A statistical analysis is developed to capture the details at a high magnification and expand the statistic results to a big area at a low magnification, to estimate the release amount and the detailed morphology. The Raman imaging results are cross-checked with scanning electron microscopy (SEM) to benefit each other. Overall, the results send us a warning that microplastic and even nanoplastic contamination can happen in our daily livers in our kitchen and entre our food chain directly.