Selegiline is a drug used to treat Parkinson's disease and depression. However, during the manufacturing process, impurities may be produced. These impurities can affect the quality, safety, and efficacy of the drug. Therefore, it is important to identify and control these impurities to ensure the drug's quality and safety. Various analytical techniques are used to detect and quantify selegiline impurities, including high-performance liquid chromatography, gas chromatography, and mass spectrometry.