Determining the hydrodynamic diameters of nanoplastics via short-end capillary zone electrophoresis-Taylor dispersion analysis in tandem

As plastics persist in the environment, they are broken down into smaller pieces through processes including UV degradation and mechanical forces. Current research focuses on developing analytical methods to characterize plastics <1 μm in diameter, known as nanoplastics, as their size is related to their toxicity. We present a novel short-end capillary zone electrophoresis-Taylor dispersion analysis (CZE-TDA) approach for determining the hydrodynamic diameters and size distributions of mixtures of nanoplastics with different surface chemistries. The CZE-TDA approach first separates particles based on electrophoretic mobility through CZE, reflecting compositional differences. In the subsequent TDA step, the hydrodynamic diameters of particles within the separated zones are determined. These steps are performed in a single analysis, using a conventional benchtop instrument with a single detector. The hydrodynamic diameters obtained by CZE-TDA were validated by Dynamic Light Scattering (DLS) and standalone TDA. Individual nanoplastics with different sizes and surface chemistries were analyzed using CZE-TDA, and the hydrodynamic diameters obtained were within 5% error of DLS. Comparable accuracy was observed for binary mixtures of nanoplastics. Our CZE-TDA approach is a promising technique for characterizing the hydrodynamic diameters of nanoplastics in complex environmental mixtures.