Quantitation of some recently introduced antibacterial drugs using sudan III as chromogenic reagent

A simple, rapid, accurate and sensitive spectrophotometric method for the determination of norfloxacin (NRF), ofloxacin (OFL) and ciprofloxacin (CPF) is described. This method is based on the formation of an ion pair with sudan III in aqueous-acetone medium [40% (v/v) acetone]. The coloured products are measured at 567, 565 and 566 nm for NRF OFL and CPF respectively. The optimization of various experimental conditions is described. Beer's law is obeyed in the range 0.4-12.0, 0.4-8.8 and 0.4-10.4 mu g mL(-1) of NRF, OFL and CPF respectively. For more accurate results, Ringbom optimum concentration ranges were 0.8-11.2, 0.6-8.5 and 0.8-10.0 mu g mL(-1), respectively. The results obtained showed good recoveries of +/- 1.2, +/- 1.5 and +/- 1.7% with relative standard deviations of 0.67, 0.83 and 1.08% for NRF OFL, and CPF, respectively. The molar absorptivity and Sandell sensitivity were also calculated. Applications of the proposed method to representative pharmaceutical formulations are successfully presented.