A novel, sensitive, and environmentally sustainable spectrofluorimetric method was developed for lisinopril quantification based on Erythrosin B fluorescence quenching. The method exploits static quenching through ground-state ion-pair complex formation between dianionic Erythrosin B and dicationic lisinopril at pH 6.0. Comprehensive mechanistic investigation employing temperature-dependent Stern-Volmer analysis, thermodynamic studies, Job's method, and PM3 semi-empirical quantum mechanical calculations confirmed the static quenching mechanism driven by electrostatic interactions with binding energy of -6.90 kcal/mol (-28.87 kJ/mol). Under optimized conditions (pH 6.0, 15 μg/mL Erythrosin B, excitation/emission, 533/555 nm), the method exhibited excellent linearity over 0.01-3.0 μg/mL (r = 0.9998) with high sensitivity (LOD, 3.1 ng/mL; LOQ, 9.2 ng/mL). Validation according to ICH Q2(R2) guidelines demonstrated excellent accuracy (99.8 ± 1.119%), precision (RSD < 1.63%), robustness, and selectivity. The method was successfully applied to pharmaceutical tablets (100.02 ± 1.079% recovery) and spiked human plasma (96.19%-105.72% recovery). Comprehensive sustainability assessment using RGB12 (whiteness, 88.0/100) and EPPI (total score, 83.8) confirmed the method's superior environmental sustainability and ideal green profile. The developed method offers significant advantages including commercially available reagents, elimination of derivatization or nanomaterial synthesis, and simple instrumentation, representing an environmentally friendly alternative for routine lisinopril determination in pharmaceutical quality control and bioanalytical applications.
Abdelzaher et al. (Mon,) studied this question.