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A glassy carbon electrode (GCE) was modified with multi-walled carbon nanotubes (MWCNT) and silver nanoparticles (AgNPs) and applied to the simultaneous determination of hydroquinone (HQ), catechol (CC), bisphenol A (BPA) and phenol by using square-wave voltammetry. The MWCNTs were deposited on the GCE and the AgNPs were then electrodeposited onto the MWCNT/GCE by the application of 10 potential sweep cycles using an AgNP colloidal suspension. The modified GCE was characterized by using SEM, which confirmed the presence of the AgNPs. The electrochemical behavior of the material was evaluated by using cyclic voltammetry, and by electrochemical impedance spectroscopy that employed hexacyanoferrate as an electrochemical probe. The results were compared to the performance of the unmodified GCE. The modified electrode has a lower charge-transfer resistance and yields an increased signal. The peaks for HQ (0.30 V), CC (0.40 V), BPA (0.74 V) and phenol (0.83 V; all versus Ag/AgCl) are well separated under optimized conditions, which facilitates their simultaneous determination. The oxidation current increases linearly with the concentrations of HQ, CC, BPA and phenol. Detection limits are in the order of 1 μM for all 4 species, and the sensor is highly stable and reproducible. The electrode was successfully employed with the simultaneous determination of HQ, CC, BPA and phenol in spiked tap water samples. Graphical abstract A glassy carbon electrode was modified with carbon nanotubes and silver nanoparticles and then successfully applied to the simultaneous determination of four phenolic compounds. The sensor showed high sensitivity in the detection of hydroquinone, catechol, bisphenol A and phenol in water samples.

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