Development of a green spectrofluorimetric method for eszopiclone determination based on erythrosin B fluorescence
Ahmed A Almrasy1, Omkulthom Al Kamaly2, Anwar M Alnakhli2
1Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Al-Azhar University, Nasr City, Cairo, 11751, Egypt.
Abstract:
A novel, sensitive, and environmentally sustainable spectrofluorimetric method was developed and validated for eszopiclone quantification in pharmaceutical formulations and human plasma. The method exploits fluorescence quenching of erythrosin B upon ground-state complex formation with eszopiclone. Stern-Volmer analysis at three temperatures (298, 303, and 313 K) confirmed a static quenching mechanism, with thermodynamic parameters (ΔH = -35.20 kJ mol-1, ΔS = -4.03 J mol-1 K-1, ΔG = -34.00 to -33.94 kJ mol-1) revealing spontaneous, exothermic, enthalpy-driven binding. Job's plot established 1:1 M stoichiometry. Box-Behnken response surface methodology optimized critical parameters, yielding optimal conditions of pH 6.8, buffer volume 1.3 mL, erythrosin B concentration 12 μg/mL, and reaction time 4 min. The validated method demonstrated excellent linearity (0.1-4.0 μg/mL, r2 = 0.9997), outstanding sensitivity (LOD = 0.031 μg/mL; LOQ = 0.094 μg/mL), superior precision (intra-day RSD = 1.130%; inter-day RSD = 1.861%), and satisfactory accuracy (99.33 ± 1.12%). Application to pharmaceutical tablets (99.21 ± 0.306%) and spiked plasma samples (98.50-100.40%) confirmed broad analytical utility, with statistical equivalence to a reference HPLC method established by t- and F-tests. Green chemistry assessment using AGREE (0.74), MoGAPI (78%), BAGI (70), and RGB12 (87.2% whiteness) confirmed high environmental sustainability.
