SERS of Bottled Water: Automated PET Nanoplastic Detection and Quantification

Nanoplastics represent an emerging contaminant of growing environmental and public health concern, with polyethylene terephthalate (PET) being on topic due to its dominant use in beverage packaging. This study presents a SERS approach for the detection and quantification of PET nanoplastics in commercial bottled water, combining SERS with colloidal silver nanoparticles (AgNPs) and commercial solid SERS substrates, with automated Pearson correlation spectral classification. Mapping SERS samples of PET-bottled water combined with a Python identification algorithm enabled the detection of PET nanoplastics, while SEM-EDX analysis confirmed the presence of nanoscale carbon-oxygen particles consistent with PET stoichiometry. Beyond PET, phthalocyanine pigment nanoparticles, likely originating from bottle package, and inorganic residues including calcite, gypsum, and sodium nitrate were simultaneously identified, demonstrating the multianalyte capability of the approach. Using colloidal AgNPs, the estimated PET nanoplastic concentration was 17.25 ± 1.6 million particles per 0.5 L bottle (34.5 ± 3.2 million particles/L), comparative with values reported by nanoparticle tracking analysis (NTA) and stimulated Raman scattering (SRS) microscopy in comparable studies. The method requires minimal sample preparation, limited to concentration by evaporation, without digestion or extraction steps, and preliminary results can be obtained within a few hours. These findings establish SERS combined with automated spectral analysis as a practical and sensitive screening tool for nanoplastic monitoring in drinking water, reporting particle concentrations directly in the number of particles per liter and with potential applicability to broader water quality analysis.