Poly(bromophenol blue)/CoSn(OH)6 cubic particles modified pencil graphite electrode for electrochemical determination of diphenhydramine

In this study, a poly(bromophenol blue) (poly(BPB))-coated CoSn(OH)6 cubic particles -modified pencil graphite electrode (poly(BPB)@CoSn(OH)6/PGE) was developed, and its electrochemical activity towards diphenhydramine (DPHN) oxidation was systematically investigated. Cyclic voltammetric studies revealed that the oxidation of DPHN at the modified electrode is governed by a diffusion-controlled process, indicating strong interaction between DPHN molecules and the poly(BPB) film. The incorporation of the CoSn(OH)6 cubic structure enhances electron transfer kinetics by increasing the density of electroactive sites and facilitating charge transport across the electrode interface. This cooperative interaction between the conductive polymer and metal hydroxide structure results in a significant amplification of the oxidation response. Under optimized conditions, the proposed electrode exhibited a linear response in the concentration range of 1.0-500.0 µM with a detection limit (LOD) of 0.30 µM. Although the analytical performance is comparable to previously reported systems, the present work provides deeper insight into the role of polymer-metal hydroxide interfaces in governing electrochemical sensing behavior. The sensor also demonstrated acceptable selectivity and applicability in pharmaceutical, biological, and environmental samples. These findings highlight the importance of interfacial design in improving electrochemical performance and offer a useful framework for developing advanced hybrid sensing platforms.