Sources of impurities
Objective
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
Definitions
• 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
pH
Limit test
Assay
Storage
• 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
Filthy
Temperature
• 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
Summary
• 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