Development of a Dye-Binding Method for Nanoplastics Detection in Snow Samples Using Capillary Electrophoresis with Laser-Induced Fluorescence Detection.

Advanced analysis of nanoplastics in snow presents unique challenges due to the intricacies involved in extracting and detecting small particles within a snow matrix. In developing a new method, samples were collected in aluminum cans during and after snowfall. The melting process was controlled within a closed metal chamber to prevent contamination. The melted snow samples were treated with a consortium of fluorescent organic dyes that bind to the target nanoplastics. Centrifugation effectively sedimented most dye-bound nanoplastics from the heterogeneous mixture. Subsequent electrokinetic injection of free dyes from the supernatant facilitated their efficient separation by capillary electrophoresis (CE), which enabled precise quantification through laser-induced fluorescence (LIF) detection. This novel dyes-CE-LIF method favorably compares with established instrumental methods for quantitatively analyzing melted snow samples containing nanoplastics amid microplastics and other colloidal particles. This novel application of the method enables rapid detection, within 15 min, at a lower limit as small as 0.1 μg of nanoplastics in melted snow samples. It requires minimal sample handling and enhances analytical throughput. Principal component analysis (PCA) revealed grouping trends among the melted snow samples and other water samples based on dye binding percentages. Variability due to differences in nanoplastic types, surface chemistry, particle size distribution, dye-nanoplastic interactions, and impurity levels were investigated across different sample sources.