Impurities are unwanted chemicals that remain with the Drug Substances and Drug Products or develop during formulation or upon aging of both API and formulation. In the pharmaceutical industry, an impurity is considered as any other inorganic or organic material, or residual solvents other than the drug substances, or ingredients, that arise out of synthesis or unwanted chemicals that remains with APIs. The unwanted chemicals even in trace amount may influence the efficacy and safety of pharmaceutical product.

Impurity profiling includes identification, structure elucidation and quantitative determination of impurities and degradation products in bulk drug materials and pharmaceutical formulations. Impurity profiling has gained importance in modern pharmaceutical analysis due to the fact that unidentified, potentially toxic impurities are hazardous to health and in order to increase the safety of drug therapy, impurities should be identified and determined by selective methods.