Accurate Quantitation of <i>N</i> -Nitrosodimethylamine in Pharmaceutical Products with High Levels of <i>N</i> , <i>N</i> -Dimethylformamide by HPLC-MS

The presence of nitrosamines in pharmaceutical products presents significant challenges for the industry, primarily due to the potential carcinogenic risks they pose to patients. Among these, N-nitrosodimethylamine (NDMA) has garnered attention as one of the first nitrosamines identified in products such as Valsartan, Ranitidine, and Metformin. NDMA is a polar compound with weak retention on most stationary phases, making it susceptible to matrix interferences. A prevalent issue is the coelution of NDMA and N,N-dimethylformamide (DMF), a common solvent and precursor for NDMA. DMF is typically present in much higher concentrations, which can lead to false positives and an overestimation of NDMA concentration due to interference from 15N DMF and 13C DMF. Conversely, elevated DMF concentrations can induce ion suppression, resulting in false negatives. Consequently, accurately quantifying NDMA remains a challenge even when utilizing high-resolution or tandem mass spectrometry techniques. To address these issues, we developed a robust HPLC-MS method employing an Evosphere AQUA column, which enables the good separation of NDMA from DMF and other sample matrices. This method permits accurate quantification of NDMA in the presence of DMF at concentrations up to 1,000,000 times greater. We achieved a quantitation limit of 0.3 ng/mL using a single quadrupole mass spectrometer, such as QDa, which corresponds to 3 ng/g NDMA relative to a 100 mg/mL Metformin HCl sample concentration, less than 10% acceptable intake of NDMA (32 ng/g). The method has been successfully validated according to ICH guidelines, demonstrating specificity, sensitivity, accuracy, precision, and robustness. The application of this method was further illustrated through the analysis of NDMA in Metformin drug products, including both immediate-release and extended-release formulations.