Isolation and Characterisation of Degradation Impurities in the Cefazolin Sodium Drug Substance

Two unknown impurities were detected in the cefazolin sodium bulk drug substance using gradient reversed-phase high-performance liquid chromategraphy (HPLC). These impurities were isolated by preparative HPLC and characterized by using spectroscopic techniques like LC-MS, LC-MS/MS, 1D, 2D NMR, and FT-IR. Based on the spectral data, the impurities have been characterized as N-(2,2-dihydroxyethyl)-2-(1H-tetrazol-1-yl)acetamide (Impurity-I) and 2-{carboxy[(1H-tetrazol-1-ylacetyl)amino]methyl}-5-methylidene-5,6-dihydro-2H-1,3-thiazine-4-carboxylic acid (Impurity-II). The structures of these impurities were also established unambiguously by co-injection into HPLC to confirm the retention time. To the best of our knowledge, these two impurities were not reported elsewhere.