Development and Validation of a Stability-Indicating RP-HPLC Method for the Determination of Erythromycin Related Impurities in Topical Dosage Form

Arobust, specific, sensitive, and precise reverse-phase HPLC method has been developed to determine a typical antibiotic drug erythromycin and related potential impurities in topical solutions. Chromatographic separation was achieved on Agilent PLRP-S (250 × 4.6 mm, 8 μm, 1000 Å) column using mobile phase A (a mixture of pH 9.0 dibasic potassium phosphate buffer, tertiary butyl alcohol, and acetonitrile in the ratio of 800:170:30 v/v/v, respectively), mobile phase B (purified water), and mobile phase C (acetonitrile) in gradient elution mode. The flow rate was kept at 2.0 mL/min, the column temperature was maintained at 65°C, and the total run time was 35 min. The optimized method was found to produce symmetric and sharp peaks with good separation between the known impurities and degradation products. The quantification was achieved with photodiode array detection at 215 nm. The Erythromycin drug was found to degrade significantly under acid, base, oxidative and thermal stress conditions, and was only stable under photolytic degradation conditions. The degradation products were well resolved from the erythromycin peaks. The developed method has been validated as per ICH guidelines and found to be linear, accurate, specific, selective, precise, robust, and useful during the process development and quality check in bulk drug and finished dosage form manufacturing.