Stability indicating ion chromatography method for the simultaneous determination of ibandronate sodium drug substance and its impurities

A simple and sensitive ion chromatography method has been developed for the simultaneous assay of ibandronate sodium drug substance and the determination of its impurities. The separation was achieved on Allsep™ anion column 150 mm × 4.6 mm, 7 μm particle diameter. The mobile phase consisted of 1% (v/v) aqueous formic acid and acetone 98:2% (v/v); flow rate 1.0 ml min⁻¹ at ambient temperature. The analytes were monitored by conductometric detector. The drug substance was subjected to stress conditions of hydrolysis, oxidation, photolytic, thermal and humidity degradation. Considerable degradation was achieved only under oxidative conditions. Mass balance was demonstrated in all stress conditions. The method was validated for specificity, precision, linearity, solution stability and accuracy. The limits of detection (LOD) and limits of quantification (LOQ) for impurities were in the range of 0.36–0.80 μg ml⁻¹ and 1.00–2.40 μg ml⁻¹, respectively. For ibandronate LOD was 38 μg ml⁻¹ and LOQ was 113 μg ml⁻¹. The average recoveries for impurities and ibandronate were in the range of 99.0–103.1% and the method can be successfully applied for the routine analysis of ibandronate sodium drug substance.