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Abstract
Impurity is defined as any substance coexisting with the original drug, such as starting material or intermediates or that is formed due to any side reactions. The impurity may be developed either during formulation, or upon aging of both API's and formulated API's in medicines. The presence of these unwanted chemicals, even in small amount, may influence the efficacy and safety of the pharmaceutical products. The control of impurities is currently a critical issue to the pharmaceutical industry. Impurity profiling includes identification, structure elucidation and quantitative determination of impurities and degradation products in bulk drug materials and pharmaceutical formulations. Identification of impurities is done by variety of Chromatographic and Spectroscopic techniques, either alone or in combination with other techniques. The advent of hyphenated techniques has revolutionized impurity profiling, by not only separation but structural identification of impurities. This review highlights the different types of impurities and various methods for isolation, separation and characterization of impurities.
Keywords: Isolation, Separation, Characterization of impurities.
1. Introduction
Chemically a compound is impure if it contains undesirable foreign matter i.e. impurities. An impurity in a drug product is any component of the drug product that is not the chemical entity defined as the drug substance or excipients in the drug product.1 Impurities in pharmaceuticals are the unwanted chemicals that can develop during synthesis, formulation or with aging of active pharmaceutical ingredient (API). Presence of impurity even in small quantity may influence the efficacy and safety of pharmaceutical products2. Now a day's majority of the drugs used are of synthetic origins, which are further formulated into different finished dosage forms. These formulations deliver the drug substances in a stable, non-toxic and acceptable form, ensuring its bio-availability and therapeutic activity3.
The major challenge for both bulk drug industries and pharmaceutical industries is to produce quality products. To meet this, vigorous quality control tests are carried out to maintain quality, purity, safety and efficacy of pharmaceuticals. The pharmacopoeias specify not only purity but also puts limits which can be very stringent on levels of various impurities4. An impurity as defined by the ICH guidelines is "Any component of the medicinal product which is not the chemical entity defined as the active substance or an excipient in the product5. The efficacy and...