Greenness Assessment of Two Validated Stability-Indicating Chromatographic Methods for Estimating Modafinil Using the Analytical Eco-Scale

Background Modafinil (MDF) is one of the drugs used for the treatment of narcolepsy. Objective This manuscript describes the development and validation of two chromatographic stability-indicating methods for MDF in the presence of its acid-induced degradation product. Methods MDF was degraded under different stress conditions and identification of the degradation product was performed using IR and mass spectroscopy. The first method involved TLC, in which plates precoated with silica gel G60 F254 were used and the developing system was dichloromethane– methanol (9:1, v/v). The second method was an eco-friendly (HPLC) method that utilized a C-18 column and ethanol–H2O (30:70, v/v) as a mobile phase with a flow rate of 1 mL/min and UV detection at 220 nm. Results Good linear relationships were obtained within the ranges 1–10 µg/band and 2–10 µg/mL for TLC–densitometry and HPLC, respectively. The obtained results were statistically compared with those of the official HPLC method and showed no significant difference with respect to their accuracy and precision at P = 0.05. Greenness scores represent excellent green analysis results in comparison with the reported studies. Conclusions The proposed methods were validated according to ICH guidelines and were applied on bulk powder and pharmaceutical dosage forms using eco-friendly mobile phases in line with worldwide trends. Highlights Chromatographic methods have been validated for the estimation of MDF in the presence of its degradation product. Clarification of the degradation pathway and elucidation of the structure were stated for the first time. This is the first published method using greenness assessment metrics for the analysis of MDF.