Determination of some non –steroidal anti-inflammatory drugs through quenching the fluorescence of lanthanide Tris complex

A new, simple and sensitive spectrofluorimetric method is developed for the determination of Piroxicam (PX), Tenoxicam (TX) and Lornoxicam (LX) .The proposed method involves the formation of complex with terbium (Tb^3+) in the presence of Tris buffer. The quenching of terbium fluorescence due to complex formation is monitored at λ em 540 nm after using λ ex 237 nm. A linear relationship is found between the concentration of the studied drugs and the quenching of the fluorescence of terbium-Tris complex. The optimum reaction conditions are studied and optimized .The proposed method is applicable over the concentration range 1.509×10^-6 – 1.509 × 10^-5 M (0.5-5 μg mL^ -1), 2.96 × 10^-6 – 1.48 × 10-5 M (1^-5 μg mL^ -1) and 1.34 × 10^-6 – 1.34 ×10^-5 M (0.5^-5 μg mL^ -1) with mean percentage recovery 99.66 ± 3.3, 100.79 ± 4.9 and 99.7±1.1 for PX, TX and LX respectively.The Correlation Coefficient is 0.9983 (n=8), 0.9989 (n=5) and 0.9999 (n=6) with limit of detection 0.2, 0.25 and 0.2 μg mL^-1 for PX , TX and LX respectively. The proposed method is applied successfully for the determination of the three drugs in their pharmaceutical formulations.The results are compared favorably with those of official or reference methods.