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.