Evaluating the Occurrence of Polystyrene Nanoparticles in Environmental Waters by Agglomeration with Alkylated Ferroferric Oxide Followed by Micropore Membrane Filtration Collection and Py-GC/MS Analysis.

Although nanoplastics (NPs) are recognized as emerging anthropogenic particulate pollutants, the occurrence of NPs in the environment is rarely reported, partly due to the lack of sensitive methods for the concentration and detection of NPs. Herein, we present an efficient method for enriching NPs of different compositions and various sizes. Alkylated ferroferric oxide (Fe3O4) particles were prepared as adsorbents for highly efficient capture of NPs in environmental waters, and the formed large Fe3O4-NP agglomerates were separated by membrane filtration. Detection limits of 0.02-0.03 µg/L were obtained for polystyrene (PS) and poly(methyl methacrylate) (PMMA) NPs by detection with pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). When analyzing real water samples from different sources, it is remarkable that PS NPs were detected in 11 out of 15 samples with concentrations ranging from <0.07 to 0.73 µg/L, while PMMA were not detected. The wide detection of PS NPs in our study confirms the previous speculation that NPs may be ubiquitous in the environmental waters. The accurate quantification of PS NPs in environmental waters make it possible to monitor the pollution status of NPs in aquatic systems and evaluate their potential risks.

Sequential Isolation of Microplastics and Nanoplastics in Environmental Waters by Membrane Filtration, Followed by Cloud-Point Extraction.

Respective detection of microplastics (MPs) and nanoplastics (NPs) is of great importance for their different environmental behaviors and toxicities. Using spherical polystyrene (PS) and poly(methyl methacrylate) (PMMA) plastics as models, the efficiency for sequential isolation of MPs and NPs by membrane filtration and cloud-point extraction was evaluated. After filtering through a glass membrane (1 µm pore size), over 90.7% of MPs were trapped on the membrane, whereas above 93.0% of NPs remained in the filtrate. The collected MPs together with the glass membrane were frozen in liquid nitrogen, ground, and suspended in water (1 mL) and subjected to pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) determination. The NPs in the filtrate were concentrated by cloud-point extraction, heated at 190 °C to degrade the extractant, and then determined by Py-GC/MS. For MPs and NPs spiked in pure water, the method detection limits are in the range of 0.05-1.9 µg/L. The proposed method is applied to analyze four real water samples, with the detection of 1.6-7.6 µg/L PS MPs and 0.6 µg/L PMMA MPs in three samples, and spiked recoveries of 75.0-102% for MPs and 67.8-87.2% for NPs. Our method offers a novel sample pretreatment approach for the respective determination of MPs and NPs.