An amorphous zinc/copper double transition metal hydroxides for electrochemical simultaneous detection of dopamine, serotonin, and melatonin

A novel electrochemical sensor, wherein the working electrode is a glassy carbon electrode modified with amorphous zinc/copper double transition metal hydroxide (ZnCu-TMH/GCE), is developed for simultaneous detection of dopamine (DA), serotonin (5-HT), and melatonin (MT), which is important for the understanding and treatment of circadian rhythm disorder diseases. The working electrode was studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). It showed that amorphous ZnCu-TMH can significantly improve the oxidation of DA during the simultaneous detection of DA, 5-HT, and MT, and the electrochemical peak potential difference was as low as 0.15 V between DA and 5-HT, showing very good electrocatalytic performance. By optimizing the detection conditions, the sensor showed a good linear response to DA, 5-HT, and MT in the range of 3 × 10⁻⁶ mol L⁻¹ ∼ 1 × 10⁻³ mol L⁻¹ (with two linear relationship curves), and the detection limits were 1.048 × 10⁻⁶, 2.213 × 10⁻⁶, and 2.356 × 10⁻⁶ mol L⁻¹ (S/N = 3), respectively. In addition, ZnCu-TMH/GCE was successfully applied to the simultaneous detection of DA, 5-HT, and MT in human saliva samples.