Spectrophotometric determination of some fluoroquinolone antibacterials by binary complex formation with xanthene dyes.

Two simple, rapid and sensitive spectrophotometric methods for the determination of levofloxacin, norfloxacin and ciprofloxacin have been performed in pure form, pharmaceutical tablets and spiked human urine. Both methods are based on the formation of a binary complex between the drugs and one of the two xanthene dyes, eosin Y or merbromin in aqueous buffered medium. Under the optimum conditions, the binary complexes showed absorption maxima at 547 nm for eosin Y and 545 nm for merbromin. Using eosin Y, the calibration graph was linear over the range 2-8 microg ml(-1) for the three drugs with mean percentage recoveries 99.935 +/- 0.648, 99.973 +/- 0.678 and 100.011 +/- 0.606 for levofloxacin, norfloxacin and ciprofloxacin, respectively. While in case of merbromin, the concentration range was 2-15 microg ml(-1) with mean percentage recoveries 99.960 +/- 0.491, 100.017 +/- 0.510 and 99.980 +/- 0.506 for the three drugs, respectively. The proposed methods were successfully applied to determine these drugs in their tablet formulations and spiked human urine and the results compared favorably to that of reference methods. The suggested methods have the advantage of being applicable for the determination of the three drugs without prior extraction. They are recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical techniques are of great importance.