A sustainable spectrofluorimetric method for ivabradine quantification based on erythrosin B quenching with quantum...

A novel, sensitive, and environmentally sustainable spectrofluorimetric method was developed for ivabradine determination based on the fluorescence quenching of erythrosin B. The method exploits the formation of a stable 1 : 1 ground-state complex between anionic erythrosin B and cationic ivabradine through electrostatic interactions. To elucidate the interaction mechanism, comprehensive mechanistic studies using Stern-Volmer analysis, thermodynamic parameters determination, and Job's method confirmed static quenching with spontaneous complex formation. Furthermore, quantum mechanical calculations using PM3 methodology revealed multiple interaction sites with binding distances of 1.7-3.6 Å, involving electrostatic interactions and hydrogen bonding. Subsequently, Box-Behnken experimental design optimization identified optimal conditions: pH 5.6, buffer volume 1.1 mL, erythrosin B concentration 25 µg mL^-1, and reaction time 4.0 minutes. Under these optimized conditions, the method demonstrated excellent analytical performance with linear response over 0.02-2.0 µg mL^-1 (r ² = 0.9995), superior sensitivity (LOD = 6.46 ng mL^-1), high accuracy, and precision. The practical applicability was demonstrated through successful application to commercial tablets and spiked human plasma samples, confirming utility for both pharmaceutical quality control and bioanalytical applications. Therefore, the developed method represents a significant advancement in green analytical chemistry, offering a cost-effective, rapid, and environmentally friendly alternative for ivabradine monitoring in pharmaceutical and clinical settings.