Rapid and high-throughput analysis of PAHs and pesticides adsorbed on microplastics using SPME-MS through a microfluidic open interface coupled to liquid electron ionization mass spectrometry

Microplastics (MPs) are pervasive contaminants in aquatic environments, capable of adsorbing and transporting hazardous chemicals such as polycyclic aromatic hydrocarbons (PAHs) and pesticides. Understanding these adsorption processes is crucial for evaluating their ecological and health risks. In this study, a green analytical approach with a high-throughput, solid-phase microextraction coupled with a microfluidic open interface and liquid electron ionization mass spectrometry (SPME-MOI-LEI-MS), was applied to investigate the kinetics and thermodynamics of PAHs and pesticides adsorption on low-density polyethylene (LDPE) and polypropylene (PP) microplastics. Method optimization and validation demonstrated intraday RSD values below 15% and limits of quantification below 10 μg/L. Results revealed that PAHs adsorb predominantly through non-polar interactions, with adsorption efficiency correlating with analyte hydrophobicity. For pesticides, adsorption patterns were more diverse, reflecting differences in molecular structure and physicochemical properties. Notably, chlorpyrifos exhibited high affinity for LDPE (95% recovery), raising concern due to its toxicity. Competition experiments further highlighted how strongly adsorbing molecules can inhibit the uptake of weaker ones as adsorption capacity at the equilibrium of atrazine, metalaxyl, dichlorvos and alachlor increases in absence of chlorpyrifos.