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In this work, a simple electrochemical biosensor for 4-chlorophenol was developed based on laccase immobilized on a hybrid nanocomposite (ZnO nanoparticles/chitosan), and incorporated in a carbon paste electrode. There are few biosensors in the literature for this specific pollutant because it tends to form polymeric films on the electrode, causing surface passivation or even enzyme inactivation. The carbon paste allowed the surface to be easily renewed by polishing, which amends this limitation. To optimize the experimental conditions, we used cyclic voltammetry and hydroquinone as a representative of phenolic compounds due to the high toxicity of chlorophenol, thus avoiding the generation of hazardous residues. After optimization, a calibration curve was constructed for 4-chlorophenol using differential pulse voltammetry, and a linear response was obtained from 1 to 50 µM, with a lower detection limit of 0.7 µM. The obtained biosensor showed high accuracy when employed in the analysis of industrial wastewater.

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