Sofosbuvir Impurity J is primarily used in the pharmaceutical industry as a reference standard during the quality control and analytical testing of Sofosbuvir, an antiviral medication. It helps in identifying and quantifying impurities in the drug substance, ensuring the final product meets regulatory standards for safety and efficacy. This impurity is crucial for developing and validating analytical methods, such as HPLC or LC-MS, to monitor the purity and stability of Sofosbuvir formulations. Its application is essential in maintaining the consistency and quality of the drug during manufacturing and storage.