Determination of ascorbic acid in biological samples using an electrochemical sensor modified with Au-Cu2O/MWCNTs nanocomposite

In this study, we developed a novel electrochemical sensor for measuring ascorbic acid (AA) or vitamin C (C6H8O6) in urine samples. The sensor was designed using a glassy carbon electrode that was modified with a nanocomposite of Au-Cu2O and MWCNTs. We investigated the characteristics of the nanocomposite using FE-SEM, TEM, XRD, and EDS. Cyclic voltammetry (CV) was used to determine the electrochemical behavior of the modified electrode and how AA is electrooxidized. Based on the electrochemical experiments, the sensor can detect trace levels of AA through voltammetry at a working potential of 0.5 vs. Ag/AgCl. We studied and modified several experimental parameters such as the supporting electrolyte, accumulation potential, solution pH, accumulation time, and amount of modifier to optimize the performance of the sensor. Furthermore, the proposed electrode exhibited a wide linear dynamic range of 1–200 μM, with a low detection limit (S/N = 3) of 0.3 μM. The use of MWCNT semiconductors and Au nanoparticles in electrode modification likely contributed to these favorable results. The outstanding properties of the nanocomposite include a large surface area, exceptional electrical conductivity, and strong electrocatalytic activity.