Toward Practical and Sensitive Fluorescence Analysis: Factorial Design‐Optimized <i>o</i> ‐Phthalaldehyde Derivatization for Synchronous Spectrofluorimetric Determination of Modafinil in Plasma and Dosage Form

The current research discusses a simple, sensitive, and practical spectrofluorimetric method for Modafinil (MDF) analysis. MDF can improve the fatigue symptoms associated with amyotrophic lateral sclerosis. MDF's aliphatic primary amide moiety can undergo base-catalyzed condensation with o-phthalaldehyde to give a highly fluorescent isoindoline derivative measured at 445 nm using synchronous spectrofluorimetry with Δλ of 110 nm. Different factors were studied using a two-level factorial design to reach the optimum conditions for the analysis. The method validation was carried out following the International Conference on Harmonization guidelines. The calibration curve was established to illustrate how relative fluorescence intensity varies with MDF concentration, and linearity was attained over the range of 10-7000 ng mL^-1, with an average recovery of 100.51% ± 0.91%. The limit of detection (LOD) was determined to be 3.21 ng mL^-1 while the quantitation limit (LOQ) was found to be 9.74 ng mL^-1. The developed method demonstrated its effectiveness in determining MDF in tablets and spiked human plasma with recoveries of 100.43% ± 0.16 and 96.07% ± 1.55, respectively. MoGAPI, AGREE, and BAGI assessments yielded scores of 72, 0.62, and 70, respectively. The results show that the method is user-friendly and can be used in routine applications.