Letrozole Diacid Impurity is primarily used in the pharmaceutical industry as a reference standard in the quality control and analytical testing of Letrozole, a drug commonly prescribed for the treatment of breast cancer. It helps in identifying and quantifying impurities during the manufacturing process, ensuring the final product meets stringent regulatory and safety standards. Additionally, it aids in the development and validation of analytical methods, such as HPLC and LC-MS, to assess the purity and stability of Letrozole formulations. Its role is critical in maintaining the efficacy and safety of the drug for therapeutic use.