Green Tandem Mass Spectrometry Method for Carcinogenic Nitrosamine Impurity Determination in Oral‐Gonadotropin Releasing Hormone Receptor Antagonist Drug

ABSTRACT N‐nitroso‐elagolix (NNE) is an API related nitrosamine impurity raised in the production of elagolix sodium (ES), the active pharmaceutical ingredient. Consequently, A precise and sensitive multiple reaction monitoring (MRM) method was optimized for quantitative measurement and determination of the NNE impurity in ES API. Separation of ES and NNE was achieved under gradient elution conditions using a Waters SunFire C18 (150 × 4.6 mm, 3.5 µm). In this study, mobile phase A consisted of 5 Mm ammonium formate, while mobile phase B was a mixture of acetonitrile and water (90:10 v/v). The mobile phase was delivered at flow rate of 0.8 mL min −1 , and a 50:50 (v/v) water‐methanol mixture was used as the diluent. The MRM transition for NNE was set at 661.40 > 205.20 with a collision energy (CE) of −14.0 eV. The detection limit (DL) and quantification limit (QL) for the NNE impurity were determined to be 0.125 and 0.375 ppb, respectively. The method demonstrated excellent precision, with percent coefficient of variation (%CV) of 1.4% for repeatability and 1.7% for intermediate precision. Accuracy was confirmed by recovery results ranging from 95% to 105%. Overall, the developed LC‐MS/MS method was verified to be linear, accurate, precise, and robust for quantifying the NNE impurity in ES API. Method greenness was evaluated using several sustainability metrics: the National Environmental Method Index (NEMI; three green quadrants), Analytical Eco‐Scale (score of 79), Analytical Greenness metric (AGREE; 0.75), and the Modified Green Analytical Procedure Index (MoGAPI; 76), all confirming the method's environmental friendliness.