TbVO ₄ /GCN Nanohybrids for the Electrochemical Detection of Papaverine Hydrochloride in Complex Matrixes

Papaverine hydrochloride (PaP-H), an isoquinoline-derived alkaloid from the opium poppy, is widely used for its antispasmodic and vasodilatory effects, particularly in treating gastrointestinal and vascular disorders. While clinically beneficial, high doses of PaP-H can have adverse effects on cardiac conduction and blood pressure regulation. Moreover, concerns over its unregulated use and unauthorized presence in consumables necessitate the development of reliable and sensitive detection methods. In response, an electrochemical sensor was fabricated using a composite of terbium vanadate (TbVO4) and graphitic carbon nitride (g-CN) to enable precise PaP-H quantification. The modified electrode exhibited excellent electrochemical behavior, characterized by high conductivity, rapid electron transfer, and strong affinity toward PaP-H. The electrochemical oxidation of PaP-H entails a mechanism involving the transfer of one electron and one proton. The TbVO4/g-CN composite shows the lowest Rct of 367.32 Ω and an increased electrochemically active surface area of 0.13 cm2 mg–1. Using differential pulse voltammetry, the sensor achieved a low detection limit of 2.4 nmol L–1 and a quantification limit of 7.92 nmol L–1, based on standard deviation methodology. It displayed a high sensitivity of 9.57 μA μmol–1 L–1 cm–2 and maintained a wide linear dynamic range from 0.05 to 119 μmol L–1. To evaluate real-world applicability, the sensor was successfully tested in artificial saliva, water samples, and bovine serum albumin. The results confirm the sensor’s practicality, stability, and suitability for monitoring PaP-H in both clinical and environmental contexts.