Submicro quantification of N-acetylcysteine by electrochemically-driven homogeneous catalysis, on boron-doped diamond electrodes

Biologically relevant thiols (biothiols) are the most important systemic and intracellular endogenous antioxidants, useful in the fight against oxidative stress (OS). This work describes the development of a sim pie and ultrasensitive electrochemical method for the determination of N-acetylcysteine (NAC), on a boron doped diamond electrode (BODE), based on an electrochemically-driven homogeneous catalysis, between lipoic acid (Lipfü) and NAC. Lipfü suffers oxidation to the sulfoxide, at potentials around +0.85 V vs Ag/AgCI. The addition of NAC (not oxidized at this potential) causes the increase of the anodic current of LipS2 Analytical parameters were obtained and redox mechanisms were proposed. The electrochemical response of NAC, in the presence of LipS2 is strongly pH-dependent and favoreci in neutral pH, being 7 the best value, which facilitates the application and the study of this interaction in biological samples. Several analytical parameters of the method were optimized for NAC, and the analytical curves were built in the range of 1 up to 100 μmol L·1, with a good correlation coefficient (0.993), with a submicrodetection limit of 93 nM. This method was successfully applied in pharmaceutical samples (capsules, syrup and suspension) containing NAC. The present study shows that the redox homogeneous reaction between the studied thiol and disulfide, on BODE, is a promising analytical tool, which can be used for quantifying NAC in a simple, rapid, convenient, sensitive and low-cost way.