The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe₃O₄/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe₃O₄/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe₃O₄ nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe₃O₄/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe₃O₄/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe₃O₄ and rGO. This implies that Fe₃O₄/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 µM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 µM for AA and DA, respectively.

Uric acid (UA), dopamine (DA) and ascorbic acid (AA) exist in the human body as protein metabolism, neurotransmitter and antioxidant, respectively. The abnormal levels of UA, DA and AA could lead to certain diseases and it could be measured and determined using electrochemical sensors. UA, DA and AA have close oxidation potentials and cause overlapping peaks in electrochemical measurements. Researchers have been working on electrode modification by using different materials to overcome those challenges and improve their selectivity, sensitivity and limit of detection. This review aims to highlight the performance of modified electrochemical sensors for detection of UA, DA and AA individually or simultaneously.