3 Marks Questions
1. Sources of Impurities in Pharmaceutical Substances
Common sources of impurities:
Raw materials: Impurities from the starting materials used in drug synthesis.
Manufacturing process: Contamination from reagents, solvents, or machinery.
Storage conditions: Degradation due to temperature, humidity, or light exposure.
(Example: Oxidation, hydrolysis, or microbial contamination.)
2. Define Error and Types of Errors
Error: The difference between the measured value and the true value.
Types of Errors:
Systematic Errors: Predictable and consistent errors (e.g., instrumental or
procedural flaws).
Random Errors: Unpredictable variations (e.g., environmental changes).
Gross Errors: Human mistakes during measurement.
3. Volumetric Analysis and Its Classification
Definition: Quantitative chemical analysis using measured volumes of a reagent.
(the amount of a substance is determined by measuring the volume that it has
occupied)
Classification:
Acid-base titrations: Neutralization reactions.
Redox titrations: Oxidation-reduction reactions.
Complexometric titrations: Reactions involving complex formation (e.g., EDTA
titrations).
4. Gravimetric Analysis
determining the amount of a substance present in a sample based on the measurement
of its mass.
Principle: A substance is converted into a measurable solid (precipitate).
Types:
Precipitation method: Analyte forms an insoluble compound.
Volatilization method: Analyte is vaporized and measured.
5. Pharmaceutical Formulations of Specific Chemicals
Ferrous Sulfate: Used as an iron supplement for anemia.
Formulations: Tablets, syrups.
Calcium Carbonate: Used as an antacid or calcium supplement.
Formulations: Chewable tablets, powders.
Nitrous Oxide: Used as an anesthetic or analgesic.
Formulations: Compressed gas cylinders.
6. Define Topical Agents with Examples
Definition: Substances applied externally for therapeutic effects.
Examples:
Antifungal creams (e.g., clotrimazole).
Antiseptic ointments (e.g., povidone-iodine).
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5 Marks Questions
1. Arsenic Limit Test (I.P.)
Purpose: To detect trace arsenic in pharmaceuticals. (The arsenic limit test, also
known as the Gutzeit test, is a procedure that detects the presence of arsenic in a
sample. It's used to test for arsenic impurities in drugs.)
Apparatus: Gutzeit or Marsh apparatus.
Reaction:
Arsenic reacts with zinc and acid to form arsine gas.
Arsine reacts with mercuric bromide paper to form a yellow-brown stain.
2. Acid-Base Titration
Definition: Neutralization between an acid and a base to determine unknown
concentration.
Indicators: Phenolphthalein (pink in base), Methyl orange (orange in acid).
Example: Titrating HCl against NaOH.
3. Precipitation Titration (Mohr’s Method)
Precipitation titration is a titration method that involves the formation of an
insoluble precipitate when a titrant reacts with an analyte.
Principle: Formation of a precipitate during titration (e.g., silver nitrate and
chloride).
Reaction:
AgNO₃ + NaCl → AgCl (precipitate) + NaNO₃
Mohr’s Method: Uses potassium chromate as an indicator to form a red precipitate
(silver chromate) at the endpoint.
(the type of titration which helps in determining the Chloride ion
concentration when it is titrated against Silver nitrate)
4. Gastrointestinal Agents
Definition: Drugs that act on the digestive system (e.g., antacids, laxatives).
Classification:
Antacids: Neutralize stomach acid (e.g., magnesium hydroxide).
Laxatives: Promote bowel movement (e.g., lactulose).
Uses: Treat indigestion, acidity, and constipation.
Storage:
Magnesium Hydroxide: Store in a tightly closed container away from moisture.
Kaolin: Store in a dry place to prevent caking.
