Electrochemical tracking of sulphadiazine with a SnO₂-PANI functionalized carbon paste electrode

Sulphadiazine (SDZINE) is widely used in clinical and veterinary practice, and its residues in food and environmental matrices require simple and cost-effective detection approaches. In this study, a SnO₂-polyaniline nanocomposite-modified carbon paste electrode (SnO₂–PANI/MCPE) was fabricated for the electrochemical detection of SDZINE. SnO₂ and PANI were synthesised and incorporated into a modified carbon paste electrode, and the material was characterised using SEM-EDX, XRD, and FTIR. Electrochemical performance was evaluated using cyclic voltammetry and differential pulse voltammetry in 0.2 M phosphate buffer solution at pH 7.4. The SnO₂-PANI/MCPE showed enhanced anodic response compared with the bare carbon paste electrode (BCPE) and individually modified electrodes, indicating improved electrocatalytic activity toward SDZINE oxidation. Scan-rate studies suggested a mixed diffusion-adsorption controlled process with significant adsorption contribution, while pH studies supported proton involvement in the oxidation process. Under optimised conditions, the sensor exhibited a linear response over 40–280 µM, with a sensitivity of 0.019639 µA µM⁻¹ , an LOD of 75.72 µM, and an LOQ of 252.41 µM. The sensor showed good anti-interference performance against common matrix species and acceptable stability, repeatability, and reproducibility. Application in spiked milk samples produced recoveries of 95.6–97.5%, supporting the preliminary practical applicability of the SnO₂-PANI/MCPE platform for SDZINE detection.