Trace identification of different nanoplastic types in real samples by electrokinetics integrated electrochemical sensor array

Abstract

The release of micro-and nanoplastics (NPs) from food packaging poses increasing environmental and health concerns. However, most analytical techniques rely on spiked samples, as weak sensor-NP interactions and diffusion limitations reduce detection sensitivity. Surface-enhanced Raman spectroscopy (SERS) using paper substrates and portable Raman systems has recently demonstrated detection limits down to 1 pg mL-1 , but reliable quantification remains difficult, particularly at low concentrations due to signal dependence on NP spatial distribution. Here, we present a novel method that integrates a hydrogen titanate nanotube (HTNT)-based electrochemical sensor array with frequency-dependent electrokinetic enrichment for sensitive detection and quantification of multiple NPs, including polystyrene, polyethylene, polypropylene, and polyethylene terephthalate, extracted from food packaging and drinking water bottles. Selective adsorption of NPs onto HTNTs (supported by computational interaction studies and Raman analysis) combined with frequency-tuned dielectrophoresis produces distinct current responses in differential pulse voltammetry. This approach achieves a detection range of 0.1 pg mL-1 to 1 ng mL-1 , with a limit of detection of 0.1 pg mL-1 in real samples, surpassing existing electrochemical sensors by over three orders of magnitude. Unique frequency-dependent signatures in the range of 500 kHz-2 MHz enable identification of NP type and concentration within 25 min, validated by Raman spectroscopy and nanoparticle tracking analysis. The method enables reliable quantification in non-spiked extracts of commercial food packages, even in presence of beverages like tea and milk, marking a substantial advancement over conventional electrochemical sensors for NP detection and paving the way for practical applications.