Integrated electrochemical platform modified with a carbon black-cerium oxide nanocomposite for the simultaneous sensing of rifampicin and isoniazid in biological and environmental samples.

Tuberculosis is a major infectious disease with high global mortality, and its first-line drugs, rifampicin (RIF) and isoniazid (INZ), are associated with serious adverse effects and public health risks when improperly administered, due to toxicity, environmental residues, and the potential induction of mycobacterial resistance. Low-cost, rapid analytical methods with simple instrumentation, particularly electrochemical approaches using screen-printed carbon electrodes (SPCE), are highly desirable for detecting these drugs. In this work, a novel electrochemical method for the simultaneous quantification of RIF and INZ was developed employing linear sweep voltammetry (LSV) as the analytical technique. As an electrochemical platform, a miniaturized and portable carbon-integrated substrate system was modified via drop-casting using a nanocomposite based on carbon black (CB) with cerium oxide (CeO2), which was comprehensively characterized using structural, morphological, and electrochemical analyses. Importantly, this CB/CeO2 material offered a drastic synergic effect for improving the electrochemical response of both antibiotics. The voltammetric strategy provided wide linear ranges for INZ (3.66 to 343.0 μmol L-1) and RIF (0.611 to 57.3 μmol L-1) with limits of detection of 0.638 μmol L-1 and 0.0390 μmol L-1, respectively. In addition, the sensor exhibited excellent fabrication reproducibility with RSD <4.76 %, as well as high selectivity for the analyte, making SPCE/CB/CeO2 applicable to tap water, human urine, and synthetic human serum, with satisfactory recoveries ranging from 96.9 to 106 % demonstrating its potential for monitoring aquatic and biological matrices.