Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink Coloured complexes were determined either by AAS or colorimetrically at lambda(max) 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50\% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 mug ml(-1) of NRF, CPF, OFL and ENF, respectively. The optimizations Of various experimental conditions were described. The results obtained showed good recoveries of 99.15 +/- 1.15, 99.30 +/- 1.40, 99.60 +/- 1.50, and 99.00 +/- 1.25\% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69\% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented. (C) 2003 Elsevier B.V. All rights reserved.