Classification, Quantification, and Fluorescence Behavior Analysis of Microplastics via Nile Red Staining: Application to Detection Emission in Takeaway Food Container.

Microplastic (MP) ingestion risk via takeaway food containers is a major public health concern. The universality of Nile Red (NR) staining used for MP detection is hindered by the lack of standardized protocols for staining, as well as low accuracy in polymer classification. Twenty solvents were tested to evaluate their effects on fluorescence intensity (FI) and apparent fluorescence color shift of prevalent polymers used in food delivery. HSV color model was established for fluorescence classification and quantification. Polarity force, hydrogen bonding force, and dispersion force are three intrinsic factors influencing NR-staining fluorescence behavior. The optimized protocol (acetone/n-hexane 3:1 (v/v), 10 μg/mL, immersion staining) achieves high FI, successfully differentiates among all polymers. Seven takeaway containers released 420-1326 MPs/box, most of which were between 10 and 20 μm and in irregular fragments. SEM observations confirmed that exposures induced surface cracks and wrinkles, which significantly compromised surface integrity and facilitated the release of MPs.