Printable Carbon Black/Graphite Conductive Ink toward Electrochemical Determination of Norfloxacin in Environmental Samples

Norfloxacin (NOR), a fluoroquinolone antibiotic widely used to treat urinary tract infections and gastrointestinal disorders caused by bacteria, poses a significant environmental concern. The widespread use of NOR can lead to the development of antibiotic resistance in human populations and, upon release into the environment, can contaminate aquatic and terrestrial ecosystems, potentially impacting human and environmental health. This work aimed to develop an electrochemical sensor printed with a conductive ink composed of graphite (Gr), carbon black (CB), and stained-glass varnish (SGV) for the detection of NOR in environmental samples. The optimal ink composition demonstrated 33% Gr, 22% CB, and 45% SGV. The morphology of the proposed sensor was designed by scanning electron microscopy and Fourier transform infrared spectroscopy, and electrochemical characterization was performed by cyclic voltammetry and electrochemical impedance spectroscopy. Differential pulse voltammetry was employed for NOR determination using 0.05 mol L^–1 Britton-Robinson buffer as the electrolyte. Optimal current responses were obtained at pH 5.0. The developed sensor presented a detection limit of 0.227 μmol L^–1 and a quantification limit of 0.756 μmol L^–1 for NOR, demonstrating high sensitivity, precision, and accuracy. Furthermore, its application in real river water samples provided recovery values between 83.9 and 103.3%. The sensor proved suitable and stable for NOR determination in environmental samples.