Electrochemical sensing of sildenafil in pharmaceutical formulations using an (S,N)-doped reduced graphene oxide-modified electrode.

In this work, (S,N)-co-doped reduced graphene oxide ((S,N)-rGO) was successfully synthesized via thermal treatment and thoroughly characterized by X-ray diffraction, high-resolution transmission electron microscopy, elemental mapping, photoluminescence, and Raman spectroscopy, confirming the successful incorporation of nitrogen and sulfur into the graphene framework. The obtained (S,N)-rGO was used to modify a glassy carbon electrode for the electrochemical determination of sildenafil (SDN). The modified electrode exhibited enhanced electrocatalytic activity toward SDN oxidation, providing a well-defined current response. Under optimized conditions, the sensor showed a good linear relationship between peak current and SDN concentration in the range of 0.25-4.98 µM, with a low limit of detection of 0.24 µM and a limit of quantification of 0.78 µM. The proposed sensor demonstrated satisfactory repeatability, reproducibility, and stability, as well as good selectivity in the presence of potential interfering substances. The applicability of the method was validated by the determination of SDN in pharmaceutical samples. The results were in good agreement with those from high-performance liquid chromatography, indicating that the proposed electrochemical method is reliable and suitable for practical analysis.