Genotoxic impurities (GTIs) are intermediates or reactants that can develop during the synthesis of a drug substance. In addition to process impurities, certain drugs may generate GTIs via degradation during formulation or storage. The genotoxic compounds have the potential to react with DNA, which could consequently cause a carcinogenic response and tumor development. It is therefore essential to identify the presence of these impurities early in the drug development process, and to have reliable and highly sensitive methods for their accurate determination in both drug substance and drug product.