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Sources of Impurities in Pharmaceutical Substances

Sources of Impurities in Pharmaceutical Substances

The impurities in pharmaceuticals are unwanted chemicals that remain with the active pharmaceutical ingredients (APIs) or develop during formulation or upon aging of both API and pharmaceutical formulation.
Sources of Impurities in Pharmaceutical Substances

Raw material employed in the manufacture

When chemical and substance are manufactured, the raw materials from which these are prepared often contain some impurities like arsenic, lead, heavy metals, etc.

The method used in the manufacture

There are a number of drugs and chemicals, which are manufactured from different raw materials by adopting different methods. Certain drugs a multiple-step synthesis procedure is involve which produces intermediate compounds. The purification of the intermediate is also essential; otherwise, it will get into the final compound. Some side reaction takes place during the synthesis. Impurities of the side reactions products are also found in the substance.

Chemical process & material employed

In the synthesis of drugs, many chemical reactions like nitration, halogenations, oxidation, reduction, hydrolysis are involved when chemical reactions are carried out in vessels or containers. The material of these vessels (Fe, Cu, Al, Ar) reacts upon by the solvents & chemical & reaction products are formed.

Storage condition

The chemical and substances are prepared are stored in different types of containers, depending upon the nature of the material, batch size, and quality.

Various type of material (plastic, polythene, iron, stainless steel, Al and copper) are used for storage reaction of these substances with the material of the storage vessels may take place and the products formed occur as impurities in the stored material.


Some substance decomposes on to keep the presence of light, air, and oxygen. Many substances lose water crystallization when kept open, while deliquescent substances absorb water from the atmosphere and get liquefied. A number of organic substances get spoiled on exposure to the atmosphere e.g. amines, phenols, potent drugs, etc.


Contamination may be particulate matter in finished product due to dust, dirt, the particle of plaster, metal, or even land which may gain entry due to the wrong environment or due to corrosion of machinery.