Development and Validation of a Stability-indicating RP-HPLC Method for Estimation of Metformin and Rosuvastatin along with Impurities from a Combined Oral Solid Dosage Form

The objective of current study was to develop and validate a stability-indicating reversed-phase highperformance liquid chromatography for simultaneous quantification of impurities in metformin sustained release-rosuvastatin immediate release combined oral solid dosage form as per International Conference on Harmonisation guidelines. Chromatographic separation was achieved using a Waters high performance liquid chromatography system with a YMC-Pack ODS-A 100x4.6 mm; 3 mu m column. Mobile phase A comprised of 20 mM ammonium acetate:acetonitrile (9:1 v/v) pH 3.5, and mobile phase B, consisted of 20 mM ammonium acetate:acetonitrile:methanol (3:5:2 v/v/v) pH 3.5. The gradient program was set as (T/% B) 0/30, 5/30, 10/50, 30/50, 40/80, 42/30 and 45/30, which pumped at a rate of 0.9 ml/min. About 10 mu l of sample solutions were injected and monitored at 240 nm. Column temperature and sample compartment was maintained at 25 degrees and 5 degrees, respectively. Forced degradation studies revealed that the peak threshould was more than the peak purity and no purity flag was observed. Repeatability, intra, and inter-day precision results were well within the tolerable limits. Limits of detection were found to be 0.10, 0.05, 0.15, 0.20 and 0.40 ppm and limits of quantitation as 0.30, 0.15, 0.45, 0.60 and 1.0 ppm for metformin, rosuvastatin, rosuvastatin impurity A, B, and C, respectively. The correlation coefficient of linearity for metformin, rosuvastatin and its impurities were found to be >= 0.999. The method recovery was found between 99 and 102 %. The proposed method appeared to be a simple, rapid, economical, accurate, specific, robust and able to distinguish the two key components from their degradants, impurities, and excipients. Therefore, current method could be applied successfully for stability and routine examination.