Spectrophotometric Determination of Norfloxacin in Pharmaceutical Formulations Based on Charge Transfer Reaction with Quinalizarin

Abstract

A simple and rapid method has been developed for the determination of norfloxacin in bulk and pharmaceutical formulations. This method was based on the formation of bluish-green charge transfer complex of norfloxacin with quinalizarin in dimethyl sulphoxide medium. A 1:1 complex was formed between the drug and reagent almost instantaneously which has a λmax of 620 nm. Under optimum conditions of reagent concentration and reaction time, the calibration curve was found to be linear over the range of 8-100 µg mL-1of norfloxacin. The detection limit was found to be 0.27 µg mL-1 with Sandell's sensitivity 0.1287 µg cm−2. Stability constant (log K) was found to be 5.91±0.04 showing high stability of the complex. Molar absorptivity was found to be 2.479×103 L mol-1 cm-1. This method was subjected to analytical quality control. Recovery studies and interference studies were carried out. The proposed method was successfully applied to the determination of norfloxacin in pharmaceutical formulations.