Electrochemically simple, sensitive, and clean method for monitoring norfloxacin in advanced oxidative processes

In this work, an amperometric analysis strategy using a carbon fiber (CF) rod as an anode was developed to follow the degradation process of the norfloxacin (NOR) molecule via electrochemical advanced oxidation processes (EAOP). The voltammetric study showed that drug oxidation is an irreversible process which involves, in the determining stage of the reaction, a proton and an electron in an EC (electron transfer followed by chemical reaction) mechanism. After optimizing the electroanalytical conditions, CF sensor showed a linear amperometric response at concentrations ranging from 1.6 μmol L⁻¹ to 30.0 μmol L⁻¹, with detection and quantification limits of 0.5 μmol L⁻¹ and 1.8 μmol L⁻¹, respectively, which are sufficient to enable in monitoring the drug during its electrolytic degradation. The results clearly showed that the by-products generated during drug degradation do not interfere with the current signal. Other application scenarios were evaluated, such as the determination of NOR in river waters and in the presence of different drug degradation by-products, obtained after EAOPs in chloride-containing medium, and no interference was observed during the electroanalysis. Therefore, the proposed analytical methodology is promising for monitoring and controlling the treatment of water contaminated with NOR antibiotic.