Europium-sensitized and simultaneous pH-assisted spectrofluorimetric assessment of ciprofloxacin, norfloxacin and gatifloxacin in pharmaceutical and serum samples

A facile, ultrasensitive and interference free europium-sensitized spectrofluorimetric method was developed for the simultaneous determination of ciprofloxacin (CFLX), norfloxacin (NFLX), and gatifloxacin (GFLX) in their mixture. A coordination complexes of Eu3+–CFLX/NFLX/GFLX were formed and the coordination was determined using the mole ratio method of continuous variation of equimolar solutions. It was found that the luminescence intensity of Eu3+ for these complexes in their mixtures is quite sensitive to three variant sets of pH, 6.0, 5.5 and 3.5 and excitation wavelengths (λex), 365, 340 and 395 for CFLX, NFLX and GFLX, respectively. Thus a dual-controlled luminescence of smoothly dynamic reversibility is achieved where a reversible on/off switchable emission of one system was observed by tuning its optimal values of pH and λex to the optimal ones of the second and so on for the third. The monitored luminescence intensity of the system showed a good linear relationship with the concentration of CFLX over the range of 5 × 10−8 to 1 × 10−6 mol L−1 with a correlation coefficient of 0.995, for NFLX within a range of 5 × 10−8 to 1.8 × 10−6 mol L−1 with a correlation coefficient of 0.990, and for GFLX within a range of 5 × 10−8 to 1.2 × 10−6 mol L−1 with a correlation coefficient of 0.995. The detection limit (LOD) was determined as 1.5 × 10−8 mol L−1 for CFLX, 3.0 × 10−8 mol L−1 for NFLX and 1.6 × 10−8 mol L−1 for GFLX. The limit of quantification (LOQ) is 4.5 × 10−8, 9.0 × 10−8, 2.8 × 10−8 for CFLX, NFLX and GFLX, respectively. Moreover, a ternary mixture of CFLX, NFLX and GFLX was satisfactorily assessed with average error <4.5%. This method has been successfully validated to the simultaneous and selective determination of CFLX, NFLX and GFLX in pharmaceuticals and serum samples with recoveries of (100.2 ± 2.1, 99.6 ± 2.5 and 103.1 ± 2.9) and (102.9 ± 1.1, 102.5 ± 1.5 and 104.4 ± 3.9), respectively.