The bulk drug industry forms base of all pharmaceutical industries as it is the source of active pharmaceutical ingredients (APIs) of specific quality. Over the last few decades much attention is paid towards the quality of pharmaceuticals that enter the market. The major challenge for both bulk drug industries and pharmaceutical industries is to produce quality products. It is necessary to conduct vigorous quality control checks in order to maintain the quality and purity of output from each industry. Purity of active pharmaceutical ingredient depends on several factors such as raw materials, their method of manufacture and the type of crystallization and purification process. Concept about purity changes with time and it is inseparable from the developments in analytical chemistry. The pharmacopoeias specify not only purity but also puts limits which can be very stringent on levels of various impurities. Modern separation methods clearly play a dominant role in scientific research today because these methods simultaneously separate and quantify the components hence making the separation and characterization of impurities easier.

Impurities in pharmaceuticals are unwanted chemicals that remain with the Active Pharmaceutical Ingredients (APIs) or develop during formulation or develop upon ageing of both APIs and formulated APIs to medicines. The presence of these unwanted chemicals even in small amounts may influence the efficacy and safety of the pharmaceutical products. Different pharmacopoeias such as British pharmacopoeia (BP) and the United States pharmacopoeia (USP) are slowly incorporating limits to allowable levels of impurities present in the APIs or formulations. The International Conference on Harmonization (ICH) has published guidelines on impurities in new drug substances, products and residual solvents. In addition, Ahuja and Gorog have published books covering different aspects of impurities including regulatory requirements, sources and types of impurities, isolation, characterization and monitoring of impurities found in drug products. Impurity profile is description of the identified and unidentified impurities present in a typical batch of API produced by a specific controlled production process. It is one of the most important fields of activity in contemporary industrial pharmaceutical analysis. The main reasons for the increasing interest of drug manufacturers and drug registration authorities in the impurity profiles of bulk drug substances.