A simple and rapid microplate fluorescence determination of adamantanes in pharmaceutical formulations

Abstract: Adamantane drugs (e.g., memantine, rimantadine, and amantadine) consist of a core tricyclodecane with different substituents. Memantine is used for treatment of Alzheimer’s disease, while rimantadine and amantadine are recommended for influenza A infection. Additionally, amantadine is clinically used for Parkinson’s disease. Analysis of adamantine drugs by optical detection requires some derivatization due to the lack of chromophores or fluorophores in their structures. This procedure is performed to enhance their detectability, but it can be time- and labor-intensive. This work focuses on developments of a simple and fast technique for the analysis of these drugs in a microplate platform. Derivatization was achieved in 50 mM borate buffer (pH 11.0) using a stoichiometric ratio between the analyte and fluorescamine (as a derivatizing reagent) of 1:10 and a reaction time of 10 min. The fluorescent derivatives were determined in a 96-well microplate using excitation and emission wavelengths at 385 and 485 nm, respectively. The method showed good linearity (r² > 0.968), repeatability (RSDs of < 2.6%), and accuracy (% recovery 96.2–101.1 with RSD < 4.5%) with acceptable limits of detection (< 3 µM) and quantitation (< 10 µM). The method was successfully applied for the determination of the drugs in pharmaceutical formulations. Graphic abstract: [Figure not available: see fulltext.].