A Terbium Sensitized Luminescence Method for the Assay of Flubiprofen in Pharmaceutical Formulations

A sensitive time-resolved luminescence method for the determination of flubiprofen (FLP) in methanol and in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb^3+) by the formation of a ternary complex with FLP in the presence of 4,7-diphenyl-1,10-phenanthroline (DPP) as co-ligand, and Tween-20 as surfactant. The signal for Tb-FLP-DPP was monitored at λex = 285 nm and λem = 552 nm. Optimum conditions for the formation of the complex in an aqueous system were TRIS buffer, pH 8.0, DPP (2.5×10^−7 M), Tween-20 (0.30%) and 4×10-5 mol L^-1 of Tb^3+ which allowed the determination of 20–1000 ng mL^-1 of FLP with a limit of detection (LOD) of 10 ng mL^-1. The relative standard deviations of the method ranged between 0.6 and 1.4% indicating excellent reproducibility of the method. The proposed method was successfully applied for the assays of FLP in pharmaceutical formulations and spiked tap water samples with average recoveries of 87% – 95%.