Magnetic bismuth sulfide-decorated activated carbon nanocomposite for ultrasensitive electrochemical determination of felodipine in real samples

Reliable and accurate analytical techniques are vital for detecting felodipine (FLD), a calcium channel blocker used to treat hypertension, in real samples. In this study, a voltammetric sensor with enhanced sensing performance for the electrochemical detection of FLD is designed based on a carbon paste electrode (CPE) modified with magnetic bismuth sulfide loaded activated carbon nanocomposite (M@Bi₂S₃NPs-AC). The effective development of the synthesized nanocomposite was confirmed by its characterization using SEM, XRD, TEM and EDX. The combination of Fe₃O₄ and Bi₂S₃ NPs within the porous AC network results in a multifunctional hybrid where, AC improves FLD accumulation and provides a conductive backbone, Bi₂S₃ accelerates the electro-oxidation reaction, and Fe₃O₄ enhances magnetic handling, stability, and conductivity ensuring a large electroactive surface area and fast electron transfer. The sensor exhibited a linear correlation for FLD in the concentration range of 0.009–3 μM under ideal conditions using differential pulse voltammetry (DPV), with a low detection limit of 2.3 nM. The technique demonstrated stability over four weeks, good reproducibility (RSD = 0.48 %), and exceptional selectivity even in the presence of frequent interferents. By evaluating FLD in pharmaceutical tablets and human blood serum samples, the sensor's practical application was confirmed, yielding good recoveries (97.2–102.8 %). This suggested sensor provides a quick, economical, and accurate method for determining FLD in medical and quality control labs.