Solvent-Free Bubbling Extraction Mass Spectrometry for Ultrasensitive, Size-Independent Detection of Microplastics in Water

Abstract

Ultratrace microplastics (MPs) in aquatic environments are a growing problem for ecosystems and human health, yet their reliable detection at subng/L levels with sub-100 nm particle sizes remains a substantial analytical challenge. Herein, we introduce a solvent-free and interface-driven bubbling extraction solid-phase microextraction gas chromatography mass spectrometry (BE−SPME−GC−MS) platform that enables ultrasensitive and size-independent detection of representative MPs (poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(lactic acid) (PLA)). The method combines bubble bursting−induced aerosol enrichment with the adsorptive microstructures of SPME coatings to achieve a dual solvent-free preconcentration pathway, facilitating the selective release of diagnostic volatile markers (methyl methacrylate, styrene, and lactide). The optimized system achieved limits of detection (LODs) of 80−180 pg/L, which are 3−6 orders of magnitude lower than those of conventional spectroscopic and pyrolysis-based approaches. The method exhibited excellent reproducibility (relative standard deviation <5%) and linearity, with correlation coefficients >0.999 over a broad concentration range. Field application to surface waters in Chengdu revealed MP concentrations below the LODs. Release tests revealed that PS cups exhibit temperature-dependent MP emissions, whereas PLA cups exhibit a nonmonotonic profile characterized by low-temperature brittleness, glass transition behavior, and high-temperature hydrolysis. Overall, this solvent-free, size-independent, and ultrasensitive analytical platform provides a robust tool for elucidating MP release behaviors and assessing real environmental exposure to ultratrace MPs in natural waters.