New method for separating and online detecting polydisperse mixed nanoplastics

Accurately separating and detecting polydisperse mixed nanoplastics (NPs) is crucial for understanding their environmental and health impacts. Following optimization of the separation mode and parameters, the coupling of asymmetric flow field-flow fractionation (AF4) with an ultraviolet-visible photodiode array detector enabled high-resolution fractionation of NPs in 20-200 nm size range. The method's recovery rates range from 86 % to 92 % (method recovery) and 91-110 % (sample recovery), with a linear range of 10-200 μg/mL. The limit of detection and limit of quantitation were less than 2 μg/mL and 6.19 μg/mL, respectively. The method also showed high repeatability, with RSD of retention time and peak area below 10 % for repeated tests. In addition, this method can be applied to separate and detect different types of NPs, such as Polystyrene, Poly(methyl methacrylate) and Polyethylene terephthalate under different pH and water-quality conditions. Moreover, it can be applied for efficient separation and detection of polydisperse mixed NPs in real water samples with retention time deviations of within 1 min. This method provides a reliable tool for the analysis of NPs in complex environments, and a convenient technology for environmental monitoring and pollution control, especially for revealing the environmental and health effects of NPs with different particle sizes.