Exogenous coreactant-free electrochemiluminescence sensing of antihistamine bilastine by harnessing electrode deactivation driven luminescence enhancement.

Bilastine (BIL), a second-generation antihistamine widely used for the treatment of allergic disorders, undergoes direct oxidation through its piperidine-based tertiary amine leading to rapid electrode surface deactivation, limiting its applicability in conventional electrochemical sensing. Herein, we report for the first time an exogenous coreactant-free electrochemiluminescence (ECL) strategy in which BIL acts as an intrinsic enhancer of the anodic ECL emission of tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+), eliminating the need for external coreactants such as tripropylamine (TPrA). Interestingly, continuous potential cycling results in an anomalous increase in ECL intensity, accompanied by a decrease in oxidation current, highlighting a unique decoupling between faradaic and luminescence response. Spectroscopic and electrochemical investigations attributed this behaviour to the formation and adsorption of a benzimidazole-based oxidative byproduct that induces partial electrode surface deactivation and facilitates a catalytic ECL pathway, leading to enhanced and stable emission. Leveraging this phenomenon, a highly sensitive ECL flow injection analysis (ECL-FIA) platform was developed, exhibiting two linear detection ranges for BIL with limits of detection of 0.162 μM and 2.22 μM, respectively. The proposed strategy offers a novel paradigm in designing of self-enhanced ECL systems where partial surface deactivation is harnessed to improve ECL performance, enabling reliable detection of electrochemically challenging small-molecule drugs.