The objective of this study was to develop an accessible and accurate analysis method for microplastics that have been unintentionally added to cream cosmetic products. An experiment was performed on three cleansing creams in rich and viscous formulations. A spiked sample was prepared by adding polyethylene (PE) microspheres to the cleansing creams. After removing cosmetic ingredients from the creams using chemical digestion, damage to the PE microspheres was identified using Fourier transform infrared (FT-IR) spectroscopy. Field emission scanning electron microscopy (FE-SEM) images were obtained before and after digestion and used to characterize the morphology of the PE microspheres.
FIG: FE-SEM images of PE microspheres before digestion at (a) low and (b) high magnification; after KOH digestion at (c) low and (d) high magnification; and after Acid Mix digestion at (e) low and (f) at high magnification.
The highest digestion efficiency was obtained using a chemical digestion method consisting of heating and stirring a sample in a 10 wt% KOH solution at 55 °C and 300 rpm for 5 days and did not damage the PE microspheres. The Nile red (9-diethylamino-5H-benzo[α]phenoxazine-5-one) staining method was effective in identifying small microplastics (< 106 μm). The optimal staining conditions are 5 μg/ml Nile red in n-hexane for green wavelengths.
Lee, S., Lee, T.G. A novel method for extraction, quantification, and identification of microplastics in CreamType of cosmetic products. Sci Rep 11, 18074 (2021). https://doi.org/10.1038/s41598-021-97557-0