Quinidine impurities are unwanted substances that may be present in quinidine drug products. These impurities can arise during the manufacturing process or storage of the drug. They may have adverse effects on the safety, efficacy, and quality of the drug product. Therefore, it is important to control and monitor these impurities to ensure that the drug product meets the required quality standards. Various analytical techniques such as high-performance liquid chromatography (HPLC) are used to detect and quantify quinidine impurities.