Magnetic adsorption-pyrolysis mass spectrometry technology for the capture, separation and quantitative analysis of microplastics from aqueous environments

Microplastics (MPs), a pivotal concern in environmental research due to their global ubiquity and potential ecological risks, present formidable obstacles for separation and detection within complex aquatic environment. This study innovatively established Magnetic Adsorption - Electromagnetic Heating - Pyrolysis - Mass Spectrometry (MA-EP-MS) to address the aforementioned issues. Nano-ferric oxide was modified and employed as the magnetic adsorbent in this protocol, which was executed using specialized Eh-Py-MS system. Employing polystyrene (PS) and poly (methyl methacrylate) (PMMA) as MPs models, the methodology enabled comprehensive detection of MPs across varying particle sizes in diverse aqueous matrices, including ultrapure water, tap water, lake water and seawater. The modified magnetic iron oxide nanoparticles (M-Fe 3 O 4 NPs) adsorbent demonstrated gorgeous capture efficiency exceeding 80% for both PS and PMMA MPs, while its direct introduction into the pyrolysis system contributed negligible background interference. Systematic evaluation revealed excellent methodological reproducibility, as evidenced by intra-day and inter-day relative standard deviations of 2.09% and 3.46%. Notably, the adsorption efficiency maintained highly stable across various aqueous matrices, with minimal interference observed. The established method achieved impressive detection limits, as low as 0.27 μg for PS MPs and 0.22 μg for PMMA MPs. Furthermore, through characterization using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) etc., mechanistic investigations revealed that physical adsorption likely represents the dominant interaction pathway for PS MPs capture. In summary, the established method provides a novel technical approach for detecting MPs in environmental water bodies, demonstrating considerable application potential.