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.