Dynamic Filtering Approach for the Online Preconcentration of Nanoplastics Using Capillary Electrophoresis

Nanoplastics, defined as plastic particles <1 μm in diameter, are increasingly recognized as chemicals of concern due to their demonstrated toxicity, which scales with concentration. Conventional analytical techniques for quantifying nanoplastics often exhibit limits of detection (LODs) above environmentally relevant concentrations. This motivates the development of new preconcentration strategies to enable more effective analysis by improving detectivity. Here, we present a novel dynamic filtration approach for the online preconcentration of polystyrene nanoplastics using entangled polymers in capillary electrophoresis (CE). The method employs a large-volume injection of dilute analyte followed by the introduction of a short plug of entangled poly vinyl alcohol (PVA) at concentrations where the entangled polymer effective pore size is significantly smaller than the diameter of the nanoplastics in the sample. Nanoplastics, whose diameters are significantly larger than the entangled polymer mesh size would be restrained from entering the pores, while buffer components pass through. Using this approach, polystyrene nanoplastics with varying surface chemistries were preconcentrated 10-fold, greatly enhancing detectivity and improving LOD relative to conventional CE and previously reported Raman-based methods. The applicability of the technique was further applied to mixtures of nanoplastics, and particles in complex environmental matrices. Overall, dynamic filtering followed by CE is a promising technique for the preconcentration and analysis of nanoplastics in environmental samples.