Aplicação de um eletrodo modificado com nanocompósito de óxido de grafeno reduzido/nanopartículas de ouro para determinação voltamétrica de metilparabeno

A glassy carbon electrode (GCE) modified with reduced graphene oxide (rGO) and gold nanoparticles (nAu) dispersed in chitosanis proposed as a novel detector for voltammetric determination of methylparaben (MePa). MePa is a member of a homologous series of parabens used single or in combination in pharmaceutical, food and cosmetic industries for antimicrobial action. However, recent studies revealed that exposure to MePa disrupts or modifies the endocrine system [1,2]. Therefore, rapid, sensitiveand convenient determination of MePa is of great importance. Graphene oxide (GO) was obtained by the modified Hummers method from the oxidation of graphite powder. The GO suspension was mixed with a chitosan aqueous solution and heatedat 90C in order to prepare reduced GO(rGO). Then, tetrachloroauric acidwas addedtothe rGO suspension. The mixture washeated, resulting in the suspensionof nAu-rGO nanocomposite. The characterization of the rGO and nAu was carried out by transmission electron microscopy (TEM), UV-vis spectroscopy and ATR FT-IR spectroscopy. The modified electrode was prepared by dropping the nAu-rGO suspensionon to the surface of a GCE. The modified surface was characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy with field emission gun (SEM-FEG).The electrochemical behavior of MePa at nAu-rGO/GCE in 0.2 mol L−1PBS buffer (pH 8.0) was studied by cyclic voltammetry.A single oxidation peak at +1.00 V was observed, characterizing an irreversible process.Theanodic current at the nAu-rGO/GCEwas4.7 times higher thanat the bare electrode, justifying its use for detection of MePa.The calibration curve for MePa determination was obtained by square wave voltammetry under optimized experimental conditions:f=50.0Hz, a =40.0mV and ΔEs =3.0 mV.Thepeak current increased linearlywith the MePa concentration in the range of 0.03 to 1.30μmol L−1(R= 0.998).The detection and quantitation limits obtained were 13.77 and 41.73nmol L−1, respectively.The proposed modified electrode was applied fordetermination of MePa in personal care products. The results obtained were compared with those provided by UV-vis spectroscopy.