A new sensing platform based on magnetic Fe3O4@NiO core/shell nanoparticles modified carbon paste electrode for simultaneous voltammetric determination of Quercetin and Tryptophan

In current study, electrochemical sensing electrode based on uniform three-dimensional (3D) flowerlike Fe3O4@NiO magnetic nanoparticles (MNPs) modified carbon paste electrode (Fe3O4@NiO/CPE) is introduced for simultaneous determination of Quercetin (Q) and Tryptophan (Trp). The Fe3O4@NiO nano-flowers were synthesized by solvothermal/decomposition method in a hierarchical architecture with microspheres of 70-80 nm, and the outer shells consisted of several nano flakes with 10-20 nm in thickness via a facile, cost effective technique. Various techniques were employed to thoroughly characterize of the sensor as well as the synthesizes magnetic nanoparticles, namely field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and voltammetry. Electrochemical studies revealed that the proposed sensor exhibited some major advantages, including high effective surface area, numerous reactive sites and excellent electrochemical catalytic activity toward oxidation of Q and Trp. Under the optimal conditions, the electrode showed linear responses for Q and Trp in wide ranges of concentrations, e.g. 0.08-60 and 0.1-120 mu M for Q and Trp, respectively. The estimated detection limits were 2.18 and 14.23 nM for Q and Trp, respectively. This sensor displayed an excellent stability, selectivity, sensitivity and good reproducibility for the modified electrode, suggesting that the sensor was a promising one for the simultaneous determination of Q and Trp in human breast milk, cow milk and honey with an excellent recovery and without the interferences of coexisting substances.