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 λ_ex = 229 nm and λ_cm = 545 nm. Optimum conditions for the formation of the complex in aqueous system, were 16 mmol/L TRIS buffer, pH 5.7, TOPO 200 umol/L and 15 μmol/L of Tb³⁺, which allows for the determination of 9.7 × 10^-7 - 9.7 × 10^-6 mol/L IB with a detection limit of 1.2 × 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%.