RESUMEN
During stress degradation studies of pioglitazone hydrochloride, one major unknown oxidative degradation impurity and two major unknown base degradation impurities were identified by LC-MS. These impurities were isolated using preparative liquid chromatography. Based on the spectral data (1H NMR, 13C NMR, MS and IR), oxidative degradation impurity, base degradation impurity-1 and base degradation impurity-2 were characterized as pioglitazone N-oxide, 3-(4-(2-(5-ethylpyridine-2yl) ethoxy) phenyl)-2-mercaptopropanoic acid and 2-(1-carboxy-2-{4-[2-(5-ethylpyridine-2yl)-ethoxy] phenyl}-ethyl disulfanyl)-3-{4-[2-(5-ethylpyridine-2yl)-ethoxy] phenyl propanoicacid, respectively. The formation and mechanism of these impurities were discussed and presented.