Fluorescent labelling as a tool for identifying and quantifying nanoplastics†

Advancements in microplastic research are progressing rapidly, yet detecting and identifying nanoplastics remain challenging, especially in natural samples. In this study, we addressed these challenges by employing fluorescent labeling on nanoparticles of six prevalent plastic types (PP, LDPE, HDPE, PS, PET, and PVC) to enable their specific detection via the analysis of 3D fluorescence spectra post-staining. Four fluorescent molecules were tested: cyanine-3 phosphoramidite, rhodamine-6G, fluorescein sodium salt, and Vat Red 15. Our observations indicated that adsorption onto nanoplastic particles resulted in peak shifts in the fluorescence signal, providing sufficient specificity for nanoplastic identification. Among the tested fluorophores, fluorescein was the most effective, successfully discriminating PP, PVC, HDPE, LDPE, and PS. Rhodamine-6G produced shifted signals for HDPE, LDPE, and PS but grouped them together. Cyanine-3 effectively distinguished PVC, PS, and PET, while Vat Red was only able to discriminate PVC.