Green and sensitive stability-indicating spectrofluorimetric assay method for the determination of donepezil HCl in pure and tablet dosage form and its kinetic application

Donepezil HCl (DH) is commonly used for the treatment of different neurological disorders such as dementia, Alzheimer’s, and Parkinson’s diseases. So far, there is no stability-indicating spectrofluorimetric assay method for the estimation of DH that has been reported. Therefore, this study aims to develop and validate a green and eco-friendly stability-indicating spectrofluorimetric assay method for the estimation of DH in pure, dosage form, and degraded solutions. The green and eco-friendly spectrofluorimetric method was developed and validated by the International Council on Harmonization guidelines, and the parameters mentioned in the guidelines were studied. The maximum pH for the fluorescence intensity of DH has been studied in the pH range 1.0–14.0, and found that from pH 1.0 to 8.0, there is no considerable difference in the fluorescence intensity of DH. Therefore, pH 7.0 was selected for the assay of DH, and the pK_a value was determined as 8.20. The calibration curve for DH is linear in the 0.50–3.50 × 10^–5 M concentration range. The accuracy and precision of the method are in the range of 100.07–100.70% and 0.57–0.65% (%RSD), respectively. The limit of detection (LOD) and quantification (LOQ) are found to be 0.89 and 2.71 × 10^–6 M, respectively. Stress degradation studies were also carried out on DH and found that the degradation products formed were not altering the accurate and precise determination through the proposed method.