Extraction of Common Small Microplastics and Nanoplastics Embedded in Environmental Solid Matrices by Tetramethylammonium Hydroxide Digestion and Dichloromethane Dissolution for Py-GC-MS Determination

Determination of microplastics and nanoplastics (MNPs),especiallysmall MPs and NPs (<150 & mu;m), in solid environmental matricesis a challenging task due to the formation of stable aggregates betweenMNPs and natural colloids. Herein, a novel method for extracting smallMPs and NPs embedded in soils/sediments/sludges has been developedby combining tetramethylammonium hydroxide (TMAH) digestion with dichloromethane(DCM) dissolution. The solid samples were digested with TMAH, andthe collected precipitate was washed with anhydrous ethanol to eliminatethe natural organic matter. Then, the MNPs in precipitate were extractedby dissolving in DCM under ultrasonic conditions. Under the optimizeddigestion and extraction conditions, the factors including sizes andconcentrations of MNPs showed insignificant effects on the extractionprocess. The feasibility of this sample preparation method was verifiedby the satisfactory spiked recoveries (79.6-91.4%) of polystyrene,polyethylene, polypropylene, poly(methyl methacrylate), polyvinylchloride, and polyethylene terephthalate MNPs in soil/sediment/sludgesamples. The proposed sample preparation method was coupled with pyrolysisgas chromatography-mass spectrometry to determine trace smallMPs and NPs with a relatively low detection limit of 2.3-29.2 & mu;g/g. Notably, commonly used MNPs were successfully detectedat levels of 4.6-51.4 & mu;g/g in 6 soil/sediment/sludgesamples. This proposed method is promising for evaluating small solid-embeddedMNP pollution. This study offers a novel method forextracting trace smallmicroplastics and nanoplastics embedded in soils, sediments, and sludges.