First-line detection of PET and PVC microplastics in water using a portable fluorescence lifetime platform

The widespread presence of micro-and nanoplastics (MNPs) in aquatic environments raises increasing environmental and health concerns, highlighting the need for fast, portable, and accessible detection methods. While fluorescence lifetime analysis coupled with phasor analysis has shown promise for monodispersed polystyrene (PS) detection, its applicability to other prevalent MNPs remains underexplored. Here, the aqueous suspensions of polyethylene terephthalate (PET) and polyvinyl chloride (PVC) microplastics (0.01-0.05 mg/mL) were examined without labeling or preprocessing. Time-correlated single-photon counting data were transformed into phasor plot to extract their fluorescence lifetime (tau & Fcy;) and modulation. Both polymers exhibited stable fluorescence lifetimes (2.38+0.12 ns for PET and 2.50+0.21 ns for PVC) across the concentration range tested. Despite the fluorescence lifetimes of PET and PVC overlap with those of other common polymers, such as PS (2.34+0.14 ns), the photon counts and modulation increased approximately linearly with microplastic concentration. In summary, the consistent signal and the relationships among concentration, photon counts, and phasor fingerprints make the portable, label-free FLA system reliable for detecting MNPs in water within minutes, with a limit of detection of 0.01 mg/mL. This system's capability is particularly valuable for its deployment as a first-line screening tool in remote or resource-limited communities, enabling timely interventions and trigger targeted advanced polymer-specific analysis.