Sources of impurities - Pharmaceutical Analysis 1 B. Pharma 1st semester

Sources of impurities


At the end of this lecture, student will be able to

• Define the terms pharmaceutical chemistry, impurities, official compounds and pharmacopoeia

• Explain the sources of impurities and their effect in pharmaceuticals

• List out tests for purity


• Pharmaceutical Inorganic Chemistry--- is the science that makes use of laws of chemistry to study inorganic substances as drugs …

• Official compound ---- medicinal substances + pharmaceutical aids included in the monograph of latest edition of pharmacopoeia

• Pharmacopoeia---directions and requirements for the preparation of medicine

• Monograph-----complete description of a specific pharmaceutical…

Title, Formula

Category, Dose

Description, Solubility


Limit test



• Pure compound - free from foreign matter

• Impure compound- not free from foreign matter

• Cannot prepare a pure compound

• Can limit the amount

• Drug – Active Pharmaceutical Ingredient (API)

Effect of Impurities

• Having toxic effect - Lead and arsenic

• Lower the therapeutic activity - Ferrous sulphate- ferric sulphate

• Affect   the stability of compound - Digitalis

• In compactable with other substance

• Technical difficulties in the use of substance

KOH +   I2   à KIO 3  + H2O  + KI

KIO 3 + 3C  à 3CO + KI

• Make the substance unhygienic

Sources of Impurities

• Raw materials employed in the manufacturing of the pharmaceutical substance

• Rock salt - preparation of sodium chloride is contaminated with calcium and magnesium chlorides

• Barium and magnesium impurities - calcium minerals

• Reagents used in manufacturing process-- not completely removed

• Method of Manufacture ---

 Reagents employed in the manufacturing process

 Reagents used to eliminate other impurities

 Solvents

 Reaction vessels

• Chemical process used in the manufacture

• Atmospheric contamination during the manufacturing process

2NaOH + CO2   à   Na2CO3   + H2O

• Manufacturing hazards

Contamination from the particulate matter

Cross-contamination of the product

Errors in the packaging

Microbial contamination

• Storage condition

Chemical instability

Reaction with container materials



• Accidental substitution or deliberate adulteration

Spurious material

Useless material

Test for purity

• Colour, odour and taste

• Physico-chemical constants

• Acidity, alkalinity and pH

• Insoluble constituent

• Ash value

• Organic impurities


• Pharmaceutical chemistry deals with inorganic drugs, their preparation, chemical nature, and influence on organism

• Pure compounds are free from foreign matter

• Impure compounds contains varying amounts of foreign matter

• Pharmacopoeia is monographs of drugs

• Effect of impurities

Arsenic and lead are harmful impurities

Impurities lower the therapeutic activity

Affects stability of substance


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