Quantitative Determination of Azithromycin by Extractive Ion-Pair Spectrophotometry Using Methyl Orange as Ion Pairing Agent

Abstract

Azithromycin is a macrolide antibiotic used in the treatment of bacterial infections. The present study is aimed at developing and validating a new colorimetric method for its determination in both pure form and in tablet formulation. The developed method utilizes ion-pair spectrophotometry and is employed for the quantitative evaluation of the drug using the acidic dye - methyl orange (MO) as ion-pairing agent at pH 2 (phthalate buffer). The yellow ion-pair complex was extracted with butanone and spectrophotometrically estimated at 422.5 nm. The developed method was validated according to ICH guidelines. The ion-pair complex of Azithromycin and methyl orange obeyed Beer’s law in the range of 10 -50 μg/ml with a correlation coefficient (r2) of 0.971. Recovery by the method was also good, with a relative standard deviation (%RSD) of 0.65 -1.06; precision (inter-day 0.675 - 0.883 and intra-day 0.712 – 1.072) were also within validation limits. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.1 and 5.7 μg/ml respectively. The developed method was successfully applied to determine Azithromycin in tablet formulation and was demonstrated to be accurate, precise and reproducible. It is also sufficiently sensitive and specific for the determination of the drug in bulk and formulation with satisfactory results.