Proguanil is an antimalarial drug used to treat and prevent malaria. However, during the manufacturing process, Proguanil can sometimes contain impurities that can affect its effectiveness or cause harmful side effects. These impurities can include residual solvents, degradation products, and other contaminants. Therefore, it is important to ensure that Proguanil is properly purified and tested for impurities before it is released for use.