Determinação voltamétrica simples e sensível de N-acetilcisteína na presença de ácido lipóico em eletrodo de diamante dopado com boro

N-acetylcysteine (NAC) is considered a medicine as well as a nutraceutical, with numerous uses [1]. It acts as a scavenger of reactive oxygen and nitrogen species (ROS), as well as a source of glutathione, one of the most important biological thiols. These properties make NAC a powerful antioxidant and a potential therapeutic agent in the treatment of diseases which pathogenesis is based on oxidative damage [1,2]. This work describes the development of a simple and sensitive electrochemical method for the determination of NAC, on a boron-doped diamond (BDD) electrode, based on a redox partnership, in solution, between lipoic acid (LipS2) and NAC. The results indicate that LipS2 is oxidized at the electrode, but is regenerated by NAC, suggesting a homogeneous redox catalytic effect. The influence of pH value was investigated in order to establish the best analytical conditions to investigate this electro-oxidation. Studies at different pH values, held in BR buffers, clearly show that at pH values between 2 to 4, there is no significant current increase of LipS2, upon addition of NAC and vice-versa. On the other hand, at pH values between 6 and 8, an intense voltammetric response is observed. At pH values above 8, we can observe a second oxidation peak with peak potential around 0.55 V vs. Ag/AgCl. In this sense, the electrochemical response of NAC, in the presence of LipS2 is strongly pH-dependent and favored in neutral pH, being 7, the best value, which facilitates the application and the study of this interaction in biological samples. The present study shows that the redox homogeneous reaction between the studied thiol and disulfide, on BDDE is a promising analytical tool, which can be used for quantifying NAC in a simple, rapid, convenient, sensitive and low-cost way, significantly better than on GCE [3].