Umifenovir impurities are chemical substances that are present in small amounts in the drug Umifenovir. These impurities can affect the purity, safety, and efficacy of the drug. Therefore, it is important to identify and control the impurities in the manufacturing process to ensure that the drug is of high quality and meets regulatory standards. Analytical methods such as HPLC, LC-MS, and NMR are used to detect and quantify the impurities.