Detecção eletroquímica de ácido ascórbico utilizando monocamadas auto-organizadas (SAM) de 4-nitrothiofenol e nanopartículas de ouro

The ascorbic acid (L-AscH2) is an antioxidant vitamin of great importance for the living beings1 . Considered essential for collagen synthesis, for tissue repair, as well as, in the treatment and prevention of certain diseases such as: Alzheimer, atherosclerosis, infertility, cancer and AIDS2,3. Different chemicals methods are used for its detection, however, electrochemical methods have been employed because they present advantages such as: low detection limit, high quantification limit and high sensitivity. The present work describes, from an innovative and simple way, the development of an eletrochemical sensor for L-AscH2 based on a self-assembled monolayers (SAM) of 4-nitrothiophenol (4-NTP) and gold nanoparticles. Initially, the 4-NTP was strategically connected to a nanostructured surface based on multi-walled carbon nanotubes (MWCNT), polyethyleneimine (PEI), and gold nanoparticles (GN). The techniques used in this work were cyclic voltammetry and chronoamperometry. In order to evaluate the sensor performance, the pair, R–NHOH/ R-NO was electrogenerated in situ by cyclic voltammetry in the potential range between 0.0 and 1.0 V vs. Ag/AgCl. Then, the potential band was restricted to study the electrocatalytic of the sensor. The electrode modified showed an efficient electrocatalytic activity towards the oxidation of L-AscH2 with oxidation overpotential of 0.15 V vs. Ag/AgCl (Figure 1). The proposed sensor showed a linear response interval of 5.0-55.0 μmol L-1 , limit of detection de 1.47 μmol L-1 , limit of quantification 4.9 μmol L-1 , and sensitivity 2.9 µA L µmol-1 , according to the analytical curve (Figure 2) obtained through chronoamperometry. Thus, the sensor is an excellent alternative for the determination of ascorbic acid.