Facile fabrication of an electrochemical sensor for the determination of two sulfonamide antibiotics in milk, honey and water samples using the effective modification of carbon paste electrode with graphitic carbon nitride and manganese oxide nanostructures

In this study, a facile, cost-effective, sensitive, and fast electrochemical sensor was designed to detect sulfa-thiazole (STZ) and sulfapyridine (SP) by a differential pulse voltammetry (DPV) method. To fabricate the sensor, a carbon paste electrode (CPE) was modified with graphitic carbon nitride and manganese oxide nanostructures (Mn3O4/g-C3N4) as environmentally friendly sensing materials. The modifiers were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The electrochemical behavior of the modified electrode was studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified CPE showed an oxidation peak of the target analytes at 0.85 mV vs. Ag/AgCl. The synergistic effect of Mn3O4, and g-C3N4/CPE promotes electron transfer and improves the sensitivity of the sensor. The parameters affecting the electrochemical responses of the two analytes were investigated and optimized. Under the optimal conditions, linear calibration plots were obtained in the con-centration ranges of 1-100 mu mol L-1 and 0.75-100 mu mol L-1 with detection limits of 0.23 mu mol L-1 and 0.11 mu mol L-1 and sensitivities of 0.1479 and 0.2950 mu A/mu mol L-1 for SP and STZ, respectively. The developed sensor also exhibited a limited interference effect on the detection of SP and STZ. Moreover, it shows good selectivity, stability, and reproducibility with a rapid response time (< 20 s). The designed electrochemical sensing platform was employed to determine SP in honey and milk, and STZ in water and milk samples with acceptable recoveries in the ranges of 86.5%-101% and 90.2-109.3%, respectively.