Development and Validation of Indirect Spectrophotometric Methods for Assessing Levofloxacin in Pure and Pharmaceutical Formulations

Abstract

Two simple, sensitive, and economical indirect spectrophotometric methods were developed for the determination of levofloxacin (LEVX) in the pure form and pharmaceutical preparations. The first proposed method (A) involved oxidation of LEVX using an excess amount of N-bromosuccinimide (NBS) under acidic conditions. Once the reaction was complete, the residual NBS was determined by shortening the color of Orange G (OG) dye, with the absorbance of the remaining dye measured at 476 nm. The second proposed method (B) is also based on the oxidation of LEVX using a fixed excess amount of NBS in an acidic environment. The excess NBS then reacts with p-Anisidine (P-AN), producing a violet-coloured brominated product. The intensity of the resulting colour, measured at 518 nm, is inversely proportional to the amount of LEVX present in the sample. Linear calibration curves were obtained for both methods within the concentration ranges of,0.5 – 10.5 and 1.0 – 15.0 μg.mL-1, respectively, with correlation coefficients of 0.9990 and 0.9992. The molar absorptivity values were 4.17×104 and 2.92×104 L.mol-1.cm-1 for methods A and B, respectively. Whereas, Sandell’s sensitivity index values were 0.00867 and 0.0123 μg.cm-2, respectively. The limits of detection (LOD) were 0.014 and 0.46 μg.mL-1, and the limits of quantification (LOQ)were 0.12 and 0.40 μg.mL-1 for methods A and B, respectively. The proposed methods were effectively used to estimate LEVX in available dosage forms, and their validity was confirmed through a recovery study using the standard addition method.