Simultaneous Determination of Epinephrine and Dopamine by Electrochemical Reduction on the Hybrid Material SiO2/graphene Content Ag Nanoparticles

Dopamine (DA), noradrenaline (NE) and epinephrine (EA) are important biological neurotransmitters belonging to the class of catecholamines that are present in mammals. Catecholamines have only a brief duration of action and are ineffective when administered orally, because they are rapidly inactivated in the intestinal mucosa and the liver before reaching the systemic circulation. These neurotransmitters play important roles in the endocrine and central nervous systems, acting to stimulate the heart, increase blood pressure and relax muscle contractions when the body prepares for major physical exertion. Furthermore, changes in their levels indicate possible neurological disorders such as HIV infection [1], Parkinson’s disease [2], and schizophrenia [3]. This work describes the synthesis, characterization and applications of a new hybrid material composed of mesoporous silica (SiO2) modified with graphene oxide (GO), SiO2/GO, obtained by the sol-gel process using HF as the catalyst. The hybrid material, SiO2/GO, was decorated with silver nanoparticles (AgNPs) with a size of less than 20 nanometres, prepared directly on the surface of the material using N,N-dimethylformamide (DMF) as the reducing agent. The resulting material was designated as AgNPs/SiO2/GO. The AgNPs/SiO2/GO material was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and high-resolution transmission electron microscopy (HR-TEM). A glassy carbon electrode modified with the AgNPs/SiO2/GO was used in the development of a sensitive electrochemical sensor for the simultaneous determination of epinephrine and dopamine employing electrocatalytic reduction using squarewave voltammetry. Well-defined and separate reduction peaks were observed in PBS buffer at pH 7, optimised conditions. No significant interference was seen for primarily biological interferents such as uric acid and ascorbic acid in the detection of dopamine and epinephrine. Our study demonstrated that the resultant AgNPs/SiO2/GO-modified electrode is highly sensitive for the simultaneous determination of dopamine and epinephrine, with the limits of detection being 0.26 and 0.27 μmol L -1 , respectively. The AgNPs/SiO2/GO-modified electrode is highly selective and can be used to detect dopamine and epinephrine in a human urine sample.