An electrode for monoethylene glycol analysis was developed based on the modification of the surface of the glassy carbon electrode with electrochemically reduced graphene oxide and gold and palladium nanoparticles (GCE/rGO/AuPd-np). Its analytical performance was assessed by determining some analytical figures of merit. Graphene oxide was reduced electrochemically as well as the metal particles with gold deposited by chronopotentiometry and palladium by cyclic voltammetry (CV). The electrode was characterized by MET, TEM and EDS techniques. The study of alcohol behaviour was performed electrochemically using CV technique. The positive synergistic effect of metals provided greater electrocatalytic response, stability and resistance to poisoning.The GCE/rGO/AuPd-np sensor presented a detection limit equal to 31.48 ${\mu}$mol l$^{–1}$ for a linear range of 89.5–179 ${\mu}$mol l$^{–1}$ with a linear correlation coefficient of 0.9096 and high stability, not losing response even after 650 cycles.

Two electrochemical sensors based on modified glassy carbon electrodes with carbon nanostructures as graphene (GCE-EG) and carbon nanotubes (GCE–CNT) were evaluated for morpholine analysis. The carbon nanostructures were obtained and characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and cyclic voltammetry. All spectroscopic and microscopic techniques confirmed the procurement of graphene and CNT. The electrochemical studies proved the efficient behaviour of both electrodes GCE–EG and GCE–CNT in sensing and detection of morpholine via differential pulse voltammetry. The area of the anodic peaks was correlated with the concentration of the analyte. It was observed that the implementation of a thin film of EG and CNT on the GCE promoted the electrocatalytic activity towards morpholine electro-oxidation, and a considerable increase in the corresponding oxidation peak was observed in both cases. Theoretical detection limits of 1.0 and 1.3 mg l$^{–1}$ were obtained for GCE–EG and GCE–CNT, respectively. These merit figures, both satisfactorily meet the requirements of the Food and Drug Administration for morpholine detection in real applications. Finally, the sample recovery for GCE–EG and GCE–CNT sensors were, respectively, 107 and 103%, at 20.0 mg l$^{–1}$ morpholine in the boiler water.