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

Sources of impurities

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

Effects of Impurities

Impurities in pharmaceuticals can have various effects, including:

  • Safety Concerns: Impurities may be toxic or cause adverse reactions, posing a risk to patient safety.
  • Efficacy Issues: Impurities can reduce the effectiveness of the pharmaceutical product, rendering it less potent or even inactive.
  • Stability Problems: Impurities can lead to physical or chemical instability, affecting the shelf life and storage conditions of the product.
  • Regulatory Compliance: Excessive impurities can lead to non-compliance with regulatory standards, resulting in the withdrawal of the product from the market.

Tests for Purity

Ensuring pharmaceutical purity involves a series of rigorous tests. These tests are conducted to identify and quantify impurities, ensuring the product meets established quality and safety standards. Some common tests for purity include:

  1. Chromatography: High-Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC) are widely used to separate and quantify impurities in pharmaceutical products.
  2. Spectroscopy: Techniques like UV-Visible Spectroscopy and Infrared (IR) Spectroscopy are used to identify and measure impurities based on their spectral characteristics.
  3. Dissolution Testing: This assesses the rate at which a drug substance dissolves and can help identify impurities affecting dissolution.
  4. Titration: Titration techniques can be used to determine the concentration of impurities by measuring their reaction with specific reagents.
  5. Mass Spectrometry: Mass spectrometry techniques can provide accurate mass and structural information about impurities.
  6. X-ray Diffraction: This is used to identify the crystal structure and purity of solid pharmaceuticals.
  7. Microbiological Testing: In the case of biopharmaceuticals, microbiological testing is essential to detect microbial contaminants.

Frequently Asked Questions (FAQs)

  1. Why is purity important in pharmaceuticals? Purity ensures the safety and efficacy of pharmaceutical products. Impurities can compromise patient health and the effectiveness of the drug.
  2. How are impurities identified in pharmaceuticals? Impurities are identified through various analytical techniques, such as chromatography, spectroscopy, and mass spectrometry.
  3. What are acceptable levels of impurities in pharmaceuticals? Acceptable levels of impurities are determined by regulatory agencies and can vary depending on the specific pharmaceutical product and its intended use.
  4. Can impurities change over time in pharmaceuticals? Yes, impurities can change over time due to degradation, interactions, or external factors like storage conditions.
  5. How can pharmaceutical companies ensure the purity of their products? Pharmaceutical companies employ strict quality control measures, testing protocols, and adherence to regulatory guidelines to ensure the purity of their products.


• 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

Also, Visit: B. Pharmacy Notes | B. Pharma Notes | Study material Bachelor of Pharmacy

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