Combining suspect screening and advanced flow analysis for the investigation of UV-light exposed microplastics:...

There is a quest for investigating the effect of microplastics (MPs) aging on the human bioaccessibility of plastic additives and the degradation products thereof. In this study, polyethylene (PE) certified reference MPs containing eight phthalate congeners with distinct polarities, ranging from dimethyl phthalate (DMP) to diisodecyl phthalate, plus bisphenol A (BPA) were weathered under controlled UV irradiation in a climatic chamber to simulate early-stage environmental aging. A suspect screening workflow using liquid chromatography coupled to high resolution mass spectrometry was leveraged to identify degradation products, namely, monomethyl phthalate, monoethyl phthalate, monobutyl phthalate, monobenzyl phthalate, monoisononyl phthalate isomers, and BPA-catechol, which were subsequently incorporated into a targeted analytical method. An automatic dynamic flow-through system based on the Unified Bioaccessibility Method (UBM) was designed for the simultaneous quantification of the oral bioaccessible concentrations of both parent compounds and degradation products. The flow-based method enables continuous extraction under physiologically relevant conditions (37 °C) along with the in-line sorptive clean-up of the gastrointestinal (GI) extracts and the handling of isotopologues. The highest GI bioaccessibility in aged PE MPs was found for parent compounds, such as BPA (76%), diethyl phthalate (92%), and DMP (108%) , while more hydrophobic congeners exhibited release down to 15%. All degradation products were significantly bioaccessible, on account of their enhanced polarity, with values > 51%. Temporal extraction profiles of both parent compounds and degradation products thereof fitted a first-order kinetic model (R² > 0.95), with apparent rate constants for the parent species of one to two orders of magnitude higher than those previously reported for pristine MPs using semi-continuous extraction systems. Overall, the integration of environmental aging, suspect screening, and an advanced automatic dynamic UBM method enhances the mechanistic understanding of the release of MP additives under physiologically relevant conditions and sets a framework for the realistic human health risk assessment of MP-associated contaminants.