Determination of piroxicam in pharmaceutical formulations and urine samples using europium-sensitized luminescence

A simple, selective and sensitive luminescence method for the assay of piroxicarn (PX) in aqueous solution is developed. The method is based on the luminescence sensitization of europium (Eu3+) by formation of ternary complex with PX in the presence of TOPO and Tween-80 as surfactant. The signal for Eu-PX-TOPO is monitored at lambda(ex) = 359 nm and lambda(em) = 615 nm. Optimum conditions for the formation of the complex in sequential injection analysis (SIA) were 0.01 M Tris buffer, pH 7.5, TOPO 5.0 x 10(-5) M, Tween-80 0.15% and 1.5mM of Eu3+, which allows the determination of 100-1000 ppb of PX with limit of detection (LOD) of 29 ppb. The relative standard deviations of the method range between 0.5% and 3.9% indicating excellent reproducibility of the method. The proposed method was successfully applied for the assay of PX in pharmaceutical formulations and in urine samples. Average recoveries of 100.8 +/- 1.7% was obtained in tablet, whereas a recovery of 97.5 +/- 2.0% was obtained for the total PX (PX+hydoxy-PX) in urine sample. (c) 2007 Elsevier B.V. All rights reserved.