Separation and Identification of Related Substances in Candesartan Cilexetil Tablets by UHPLC-Q-TOF–MS

Related substances, such as process-related substances and degradation products, may affect the efficacy of drugs and cause adverse reactions. Therefore, identifying and controlling them is of the importance. A rapid ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF–MS) method has been developed for the separation and characterization of related substances in candesartan cilexetil tablets. After optimization, the method validation was followed according to ICH guidelines. The developed UHPLC method showed adequate specificity, sensitivity, accuracy, linearity, precision, stability and robustness for validation of analytical procedures. Commercial candesartan cilexetil tablets was subjected to stress testing (60 ℃, 90% RH and 4500 lx for ten days) and forced degradation studies (acidic, alkaline, oxidative and photolytic degradation conditions). A total of eleven related substances were detected and characterized. Among them, four related substances have not been reported in the literature yet, and one of them (RS7) was confirmed as candesartan cilexetil methoxy analog by reference substance. In addition, plausible mechanisms for the formation of these related substances are discussed. This study provides a useful reference for the quality control of candesartan cilexetil tablets.