A Preliminary Study of Microplastic Abrasion from the Screw Cap System of Reusable Plastic Bottles by Raman Microspectroscopy

The packaging material of bottled water is suspected to be a source of microplastics (MP). In this preliminary study, the screw cap system was examined for its MP release potential. Therefore, the concentration of MP (≥10 μm) was determined in reusable polyethylene terephthalate (PET) bottles with polypropylene (PP) caps and polyethylene (PE) seals after opening and closing once and 11 times. The entire contents of the bottles were filtered onto a silicon filter after opening. The inside of the bottles and caps was rinsed with filtered water. The total Si filter area was analyzed by Raman microspectroscopy. After one opening, 131 ± 25 microplastic particles (MPP) per liter were detected. After 11 openings and closings, 242 ± 64 MPP/L were detected. The increase is caused by a significant increase in the number of PP particles from 100 ± 27 to 185 ± 52 MPP/L. The concentration of PE and PET particles did not change significantly. Regardless of polymer type and the number of openings and closings, 80% of the MPP were identified in the smallest size class investigated (10–50 μm). Using a specially developed method, the concentration of MPP was determined before the screw cap system was opened and did not differ from the procedural blank.