ORIGINAL PAPER Lorena Athie Goulart 1 & Roger Gonçalves 1 & Alessandra Alves Correa 1 & Ernesto Chaves Pereira 1 & Lucia Helena Mascaro 1 Received: 10 July 2017 /Accepted: 9 November 2017 /Published online: 5 December 2017 # Springer-Verlag GmbH Austria, part of Springer Nature 2017 Abstract 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 deter- mination. 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. Keywords Multi-walled carbon nanotubes . AgNPs . Metallic nanoparticles . Sensor . Phenolic compounds . Voltammetry . Endocrine disruptor . Emerging pollutants . Simultaneous determination . Electrochemical detection Introduction Carbon nanotubes (CNTs) are very versatile and can be applied in different electrochemical devices. They are materials that are structured in the nanometer scale with unique properties, such as high tensile strength and electrical and thermal conductivity [1]. Multi-walled carbon nanotubes (MWCNTs) are widely employed and used to build electrochemical sensors and bio- sensors due its catalytic properties and high surface area [2]. Acid treatments [ 3] and the incorporation of metallic nanoparticles [4] within the CNTs are an alternative with which to improve the analytical response of the sensors, thereby resulting in low detection limits [5]. The metallic nanoparticles that are most often used are gold, nickel, copper oxide and silver [6, 7]. Silver nanoparticles (AgNPs) have stood out because they are inexpensive, easy to obtain and offer excellent catalytic properties [8]. Different methods have been reported for the deposition of nanoparticles on CNTs. The most frequently used are casting, spin coating and electrodeposition [9]. The electrochemical procedure presents advantages because of its simplicity and quickness. In this work, a sensor based on MWCNTs and AgNP was developed for the detection of phenolic compounds such as hydroquinone (HQ), catechol (CC), bisphenol A (BPA) and phenol (Phe). These substances are commonly used in the manufacture of plastic bottles, metal food cans, cosmetics, and pesticides [10]. However, these compounds are emerging Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-017-2540-5) contains supplementary material, which is available to authorized users. * Lucia Helena Mascaro lmascaro@ufscar.br 1 Department of Chemistry, Universidade Federal de São Carlos, CP 676, São Carlos-SP 13565-905, Brazil Microchimica Acta (2018) 185: 12 https://doi.org/10.1007/s00604-017-2540-5 Synergic effect of silver nanoparticles and carbon nanotubes on the simultaneous voltammetric determination of hydroquinone, catechol, bisphenol A and phenol