Surface-initiated molecularly imprinted polymer film for sensitive electrochemical detection of PFOA in environmental waters.

Abstract

An electrochemical sensor for the selective detection of perfluorooctanoic acid (PFOA), a highly persistent and hazardous per- and polyfluoroalkyl substances (PFAS), was developed using a molecularly imprinted polymer (MIP) approach. The sensing layer was fabricated through surface-initiated controlled photopolymerization (via a "grafting from" strategy) directly from a commercial screen-printed gold electrode that was first functionalized with a tailor-made photoiniferter. Upon UV irradiation, acrylamide (AAm) and ethylene glycol dimethacrylate (EGDMA) were copolymerized in the presence of PFOA, generating specific recognition sites within the polymer network. Optimization was performed on the polymerization time and the extraction procedure of PFOA from the MIP layer, with morphological and chemical characterization via atomic force microscopy (AFM) and energy-dispersive X-ray spectroscopy (EDX), respectively. Sensor performances were assessed using square wave voltammetry (SWV). It could detect PFOA over a wide concentration range, from 8 pM to 80 µM, with a limit of detection (LOD) of 8 pM (3.31 ng/L). Selectivity was evaluated against structurally similar non-fluorinated compounds, as well as short- and long-chain PFAS, showing good recognition of PFOA even in competitive mixtures (ratios of 1:1, 1:5, and 1:10). Applicability was further confirmed through successful detection in tap water, surface freshwater, and river water demonstrating good correlation between electrochemical measurements and high-performance liquid chromatography (HPLC-MS/MS) results. The controlled grafting strategy developed enables the formation of a robust and selective MIP layer, offering a promising platform for sensitive PFAS detection in natural waters.

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