Green Micelle-Enhanced Spectrofluorimetric Determination of Gefitinib in Pharmaceutical Tablets Using Cremophor RH 40: Response-Surface Optimization and Time-Dependent Density Functional Theory (TD-DFT) Interpretation

Gefitinib is an epidermal growth factor receptor inhibitor used in non-small-cell lung cancer. This study developed a micelle-enhanced spectrofluorimetric method for its determination in tablets using native fluorescence and Cremophor RH 40 without derivatization. Experimental conditions were screened by a univariate approach and further evaluated by response-surface methodology. The quadratic model was significant (F = 83.26, p = 0.0019), and three confirmation experiments yielded prediction errors of 0.515–0.954%, supporting local agreement at the selected conditions. Fluorescence intensity was measured at an emission wavelength of 394 nm following excitation at 333 nm. The method was linear over 50–1200 ng mL−1 (r = 0.9997). The calculated limits of detection and quantification were 6.89 and 20.89 ng mL−1, respectively, while 50 ng mL−1 was retained as the lowest validated concentration. The method showed acceptable accuracy, repeatability, and selectivity for the investigated tablet matrix. Robustness testing indicated that pH requires careful control around 8.0. Analysis of pooled commercial tablets yielded an assay of 100.21 ± 1.86% of the label claim. TD-DFT calculations supported qualitative interpretation of the electronic transitions. The AGREE score was 0.61, indicating a more favorable environmental profile than the reference spectrofluorimetric method comparator (0.46).