A Novel Green Spectrofluorimetric Approach for Memantine Quantification With Mechanistic Elucidation Through Quantum Mechanical Modeling and Green Analytical Chemistry Evaluation

ABSTRACT A novel, sustainable spectrofluorimetric method was developed for memantine determination using erythrosin B as a fluorescent probe, addressing critical analytical gaps in pharmaceutical quality control and environmental monitoring. The method exploits static fluorescence quenching through ground‐state complex formation between protonated memantine and anionic erythrosin B. Initially, UV–Vis absorption spectroscopy revealed a significant hypochromic effect accompanied by a hypsochromic shift of 5 nm, with the absorption maximum shifting from 527 to 522 nm upon complex formation, while fluorescence studies demonstrated concentration‐dependent quenching at 527 nm excitation and 553 nm emission wavelengths. Subsequently, temperature‐dependent Stern–Volmer analysis yielded quenching constants decreasing from 6.22 × 10 5 to 4.47 × 10 5 mol L −1 (298–313 K), confirming the static quenching mechanism. Furthermore, Job's method established 2:1 memantine‐to‐erythrosin B stoichiometry, which was validated by quantum mechanical calculations revealing energetically favorable binding interactions. The developed method exhibited excellent analytical performance with a linear range of 0.02–2.0 μg/mL, a detection limit of 6.5 ng/mL, precision (%RSD < 2%), and accuracy (98.59%). Moreover, successful applications included pharmaceutical formulations and spiked environmental water samples, achieving quantitative recoveries ranging from 96% to 104% across different matrices. Finally, a comprehensive sustainability assessment demonstrated superior green credentials compared to conventional chromatographic approaches.