Determination of meloxicam using europium sensitized luminescence in the presence of co-luminescence reagents

A sensitive time- resolved luminescence method for the determination of meloxicam (MX) in methanol and in aqueous solution is described. The method is based on the luminescence sensitization of europium (Eu ³⁺) by formation of ternary complex with MX in the presence of 1,10- phenanthroline as coligand, Tween-80 as surfactant and gadolinium ion as a co-luminescence reagent. The signal for Eu- MX-1, 10- phenanthroline is monitored at λ _ex=360 nm and λ _em=620 nm. Optimum conditions for the formation of the complex in aqueous system were 0.01 M TRIS buffer, pH 8.0, 1,10- phenanthroline (6.0×10 ^-6 M), Gd ³⁺ (7.0×10 ^-6 M), Tween-80 (0.28%) and 1.75 mM of Eu ³⁺ which allows the determination of 20.800 ppb of MX with limit of detection (LOD) of 7 ppb. The relative standard deviations of the method range between 0.1 and 1.1% indicating excellent reproducibility of the method. The proposed method was successfully applied for the assay of MX in pharmaceutical formulations, plasma and in urine samples. Average recoveries of 99.8-1.1%, 100.2-0.9% and 100.9-1.1% were obtained for MX in tablet, plasma and urine sample respectively.