A europium-sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of gatifloxacin (GFLX). The GFLX-Eu3+-SDBS system was studied and it was found that SDBS significantly enhanced the fluorescence intensity of the GFLX-Eu3+ complex (about 25-fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 338 and 617 nm, pH 7.5, 3.0 x 10(-6) mol/L europium(III), and 5.0 x 10(-5) mol/L SDBS. The enhanced fluorescence intensity of the system (DeltaI(f)) showed a good linear relationship with the concentration of GFLX over the range 1.0 x 10(-8)-8.0 x 10(-7) mol/L with a correlation coefficient of 0.9990. The detection limit (S:N = 3) was determined as 1.0 x 10(-9) mol/L. This method has been successfully applied for the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range and good stability. The luminescence mechanism of the system is also discussed in detail.

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