Chemical heterogeneity observed in the development of photo-oxidized PET micro- and nanoparticle weathered controls

Abstract

Determining unknown secondary micro and nanoplastic (MNP) composition remains a persistent analytical challenge for field collected samples. The availability of material standards should accelerate method development for improved identification. Here, ultraviolet irradiated polyethylene terephthalate (PET) films and particles were used as models for investigating the production of weathered controls. We investigated the weathered products' chemical signatures, their stability during sampling and examination, and reproducible production of the chemical distributions using commonly reported analytical approaches for small plastic particles. We found that both conditions during irradiation and the processing procedure used for MNP production significantly contribute to changes in product distribution and the persistence of the oxidized products within the particles. Measurements were also conducted directly on MNP powders after UV-exposure to minimize any possible perturbations in product distribution from sample handling and processing. Using the model PET system, differences in sensitivity for commonly used techniques and methods were compared and discussion on relative performance for detection sensitivity was provided. Together, these findings revealed unreported pitfalls affecting accurate identification of chemically modified MNP materials.