Sustainable fluorescence quenching approach for betahistine analysis: greenness evaluation

A simple, sensitive, and eco-friendly spectrofluorimetric method has been developed for the determination of betahistine in bulk powder and tablet formulations. The method relies on fluorescence quenching of eosin Y at 540 nm (λ_ex = 335 nm) through formation of a non-fluorescent ion-pair complex between the dye and protonated betahistine in acetate buffer (pH 3.8). Key experimental parameters-including buffer pH, buffer volume, eosin concentration, and diluting solvent-were optimized to maximize sensitivity. Under the selected conditions, a linear calibration curve was obtained over 1.0-5.0 µg mL⁻¹ with an excellent correlation coefficient (r = 0.9996). Limits of detection and quantification were 0.17 and 0.51 µg mL⁻¹, respectively. Validation according to International Council for Harmonization Q2 (R1) guidelines confirmed high accuracy (mean recovery 99.06%) and precision (RSD < 2%). The method was successfully applied to commercial tablets without interference from excipients, and results showed no significant difference compared with a reported spectrophotometric method. Owing to its simplicity, sensitivity, and exclusive use of aqueous media, the procedure is well-suited for routine pharmaceutical quality control.