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Controlled modification of the hydrophilicity of polyethylene terephthalate micro- and nanoplastic particles and their analysis in bottled drinking water

Schirinzi GF, Seghers J, Roncari F, Valsesia A, Emteborg H

Analytical and bioanalytical chemistry, 2026

Abstract

We have previously developed methods to artificially age cryogenically milled polyethylene terephthalate (PET) and polyethylene (PE) particles using alkaline and acidic treatments. This approach reliably resulted in large quantities of micro- and nanoplastic particles with significantly increased hydrophilicity. To investigate the relationship between treatment time and hydrophobicity, we studied the hydrophobicity index (Hy) of PET particles treated with 0.25 M KOH for different treatment times in an ultrasonic bath (1.5-6 h). We obtained a specific size fraction of interest (0.2-1.2 µm), by centrifugation of the initial suspension of artificially aged PET (aPET). For this, a stepwise centrifugation protocol was used, and we characterized the specific size fraction using an array of different techniques. The characterization techniques included dark field (DF) microscopy for determining the hydrophobicity index (Hy), particle counting by single particle extinction and scattering (SPES), dynamic light scattering (DLS), Raman microscopy, and scanning electron microscopy (SEM). The results showed clear instability and hydrophobic behavior for shorter treatment times. Stable suspensions were obtained after 6 h of treatment with KOH yielding increased hydrophilicity and a sufficiently high zeta potential. The decrease in hydrophobicity index values over time should make it possible to design future reference materials where the artificially aged micro- and nanoplastic particles…

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