New application for the identification and differentiation of microplastics based on fluorescence lifetime imaging microscopy (FLIM)

The problem of micro- and nanoplastic (short: plastics) pollution is an increasing global issue and therefore several detection methods for plastics, also investigating the chemical nature via spectroscopy and chromatography, have been developed over the years. A new approach for identification and characterization of plastics is fluorescence lifetime imaging microscopy (FLIM) - a microspectroscopic method to detect fluorescence lifetime (tau) of plastics. We tested whether FLIM can be employed for the identification and characterization of plastics. Six types of plastics (ABS, PA6, PET, PLA, PPE, PU), with and without prior heat treatment, were subjected to FLIM with excitation wavelengths of 470 nm and 440 nm. The results provided mean tau (intensity weighted) values of 3.850 (+-0.033) ns for ABS, 8.143 (+-0.060) ns for PPE, 3.519 (+-0.090) ns for PET of a bottle from Germany and 3.564 (+-0.126) ns for PET of a bottle from the USA. The combination of mean intensity weighted tau and mean amplitude weighted r values allowed for the significant differentiation of 52 (94.55 %) of the 55 possible plastic comparisons. Moreover, FLIM showed the potential for the sub-micrometer range plastic characterization, phasor analysis and allows for visual 3D-sectioning of samples that could be important for identification and characterization of plastics in tissue and environmental samples.

Automated summary

The FLIM method was tested for identification and characterization of six types of plastics, showing significant differentiation in 94.55% of the comparisons. Results suggest that FLIM has the potential for sub-micrometer plastic characterization and allows for visual 3D-sectioning of samples, which could be important for identifying and characterizing plastics in tissue and environmental samples.