Determination of ibuprofen in pharmaceutical formulations using time-resolved terbium-sensitized luminescence.

A sensitive and specific luminescence method for the determination of ibuprofen (IB) in pharmaceutical formulations in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb(3+)) by formation of ternary complex with IB in the presence of tri-n-octylphosphine oxide (TOPO) and Tween-20 as surfactant. The luminescence signal for Tb-IB-TOPO is monitored at lambda(ex) = 229 nm and lambda(em) = 545 nm. Optimum conditions for the formation of the complex in aqueous system, were 16 mmol/L TRIS buffer, pH 5.7, TOPO 200 micromol/L and 15 micromol/L of Tb(3+), which allows for the determination of 9.7 x 10(-7) - 9.7 x 10(-6) mol/L IB with a detection limit of 1.2 x 10(-7) mol/L. The relative standard deviations of the method were <1.4%, indicating excellent reproducibility. The proposed method was successfully applied for the assays of IB in pharmaceutical formulations with average recoveries of 100.3-102.5%.