Simultaneous voltammetric determination of hydroquinone and catechol by using a glassy carbon electrode modified with carboxy-functionalized carbon nanotubes in a chitosan matrix and decorated with gold nanoparticles

The authors describe a method to anchor gold nanoparticles (AuNPs) on carboxy-functionalized multi-walled carbon nanotubes (c-MWCNTs) utilizing chitosan as dispersing and protective agent. A sensor for the simultaneous determination of hydroquinone and catechol was then fabricated by placing this nanocomposite on a glassy carbon electrode (GCE). The morphology and composition of the nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction. The electrochemical behavior of the modified GCE was studied by electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The modified GCE exhibits good electrooxidative activity towards hydroquinone and catechol and therefore was used for simultaneous determination of both, with typical voltages of 30 and 130 mV (vs. SCE). A linear reponse is found for the 0.5 μM to 1.5 mM hydroquinone concentration range, and for the 5.0 μM to 0.9 mM catechol concentration range. The respective lower detection limits are 0.17 and 0.89 μM (at an S/N ratio of 3). The sensitivity is 644.44 μA mM−1 cm−2 for hydroquinone and 770.98 μA mM−1 cm−2 for catechol.