Adsorption of benzophenone-3 and octocrylene UV filters on polyethylene: analysis by HPLC-MS/MS and voltammetry with screen-printed electrodes

Microplastics (MPs) are persistent pollutants that can adsorb contaminants, facilitating their accumulation in aquatic ecosystems. The presence of UV filters (UVFs) such as benzophenone-3 (BP3) and octocrylene (OC), exacerbates this issue, particularly in coastal areas. This study presents an innovative dual-method approach combining high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and differential pulse adsorptive stripping voltammetry (DPAdSV) to assess the adsorption of UVFs on polyethylene (PE), a widely found polymer in aquatic environments. Adsorption kinetics were analysed using pseudo-first-order (PFOM) and pseudo-second-order (PSOM) models, revealing a higher equilibrium sorption capacity for OC due to its stronger hydrophobic interactions with PE. A central composite design (CCD) was employed to enhance resources efficiency in experimentation and controlled experiments exposed the materials to both pure fresh water and synthetic seawater. The results indicate a higher adsorption affinity of OC on PE than BP3, attributed to its high octanol-water partition coefficient (log Kow 6.88) and stronger hydrophobic interactions. Exposure time was the most influential variable across both media, while pH and temperature had a significant effect on BP3 adsorption in synthetic seawater. Hydrophobic partitioning, aided by van der Waals forces, was identified as the dominant interaction mechanism for both UVFs, with π-π and electrostatic interactions playing minimal roles due to the nature of the polymer. The study provides new insights into how polymer-pollutant interactions vary across environmental conditions and offers a novel voltammetric alternative for in-situ UVFs monitoring.