Terbium sensitized luminescence for the determination of ketoprofen in pharmaceutical formulations

This paper explores an ultra-sensitive luminescence method for the determination of Ketoprofen (KP) in pharmaceutical formulations. The technique is indirect and exploits the luminescence enhancement of terbium (Tb ³⁺) by complexation with KP (Tb ³⁺-KP), which was monitored at respective excitation and emission wavelengths of λ _ex=258 nm and λ _em=549 nm. The effect of varying the Tb ³⁺ concentration and using multiple solvents was examined to determine optimal experimental conditions. Maximum sensitization was accomplished in the presence of methanol where the most favourable condition for the formation of the complex was recorded at a level of 1.0×10 ^-5 M of Tb ³⁺. Under these optimum experimental conditions, linear calibration curve was obtained in the range of 2.8×10 ^-7-3.1×10 ^-6 M with a detection limit of 8.7×10 ^-8 M. The technique was validated with 'working' reference standards and produced relative standard deviations < 2% indicating that the reproducibility was highly acceptable. The proposed method was successfully applied to assays of KP in pharmaceutical formulations with average recoveries of 92-98%. The results were found to be in good agreement with those obtained by HPLC. The method is highly suited for general applications of this nature.