Busulfan is a chemotherapy drug used to treat certain types of cancer. However, during its synthesis and storage, impurities may be formed which can affect the drug's efficacy and safety. These impurities can be organic or inorganic in nature and must be monitored and controlled to ensure the quality and purity of the final drug product. Analytical methods are used to detect and quantify these impurities, and strict regulations are in place to limit their levels in the drug.