Chemical tests for Colophony MCQs With Answer

Chemical tests for Colophony MCQs With Answer

Colophony (rosin) is a solid resin obtained from pine trees, rich in resin acids such as abietic and pimaric acids. For B. Pharm students, understanding chemical tests for colophony is essential for pharmacognosy and quality control of excipients and topical formulations. Common evaluations include solubility checks, acid value, saponification value, melting/softening behavior, and chromatographic or spectroscopic identification (TLC, HPLC, IR). Practical tests detect adulterants, quantify free acids, and assess suitability in ointments, adhesives, and coatings. This concise review emphasizes analytical principles, reaction behavior with alkali, and instrumental confirmation methods. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is colophony (rosin)?

• A liquid essential oil from citrus peels
• A synthetic polymer used as a plasticizer
• A solid resin obtained from pine trees
• A mineral wax derived from petroleum

Correct Answer: A solid resin obtained from pine trees

Q2. Which class of compounds is the major constituent of colophony?

• Alkaloids
• Resin acids (e.g., abietic acid)
• Polypeptides
• Steroid glycosides

Correct Answer: Resin acids (e.g., abietic acid)

Q3. How does colophony behave in water and ethanol with respect to solubility?

• Soluble in water, insoluble in ethanol
• Insoluble in water, soluble in ethanol
• Soluble in both water and ethanol
• Insoluble in both water and ethanol

Correct Answer: Insoluble in water, soluble in ethanol

Q4. Which pharmacopeial test indicates the amount of free resin acids in colophony?

• Saponification value
• Acid value
• Moisture content test
• Specific rotation

Correct Answer: Acid value

Q5. What does the saponification value of colophony measure?

• The content of volatile terpenes
• The total amount of esterifiable material plus free acids
• The degree of polymerization of resin acids
• The water solubility of rosin

Correct Answer: The total amount of esterifiable material plus free acids

Q6. Which chemical reaction is used to demonstrate that colophony contains carboxylic acids?

• Treatment with dilute acid to form salts
• Titration with alkali to determine acid value
• Bromination of double bonds
• Hydrogenation under pressure

Correct Answer: Titration with alkali to determine acid value

Q7. In thin-layer chromatography (TLC) of colophony, what is commonly detected after development?

• Protein bands visible by Coomassie stain
• Spots corresponding to different resin acids visualized by spraying reagents
• Fluorescent peptides under UV 254 nm only
• No separable components due to high purity

Correct Answer: Spots corresponding to different resin acids visualized by spraying reagents

Q8. Which spectroscopic feature is characteristic of resin acids in colophony?

• A strong OH stretch at 3200–3600 cm⁻¹ only
• A carbonyl (C=O) stretch near 1700 cm⁻¹ in IR
• A sharp nitrile band at 2250 cm⁻¹
• No significant IR absorptions

Correct Answer: A carbonyl (C=O) stretch near 1700 cm⁻¹ in IR

Q9. Which instrumental method is most suitable for quantifying specific resin acids in colophony?

• Gas chromatography (GC) after derivatization
• Paper chromatography without detection
• Polarimetry
• Flame photometry

Correct Answer: Gas chromatography (GC) after derivatization

Q10. Which of the following is a common pharmaceutical use of colophony?

• Antibiotic agent
• Ointment base and adhesive component
• Systemic analgesic
• Anticoagulant

Correct Answer: Ointment base and adhesive component

Q11. How is adulteration of colophony commonly detected in quality control?

• By measuring melting point only
• By comparing acid value, ester content, and chromatographic profile
• By tasting small samples
• By checking for radioactivity

Correct Answer: By comparing acid value, ester content, and chromatographic profile

Q12. What effect does saponification with alcoholic KOH have on colophony?

• It oxidizes resin acids to ketones
• It converts resin acids into their potassium salts (soaps)
• It polymerizes the resin to a higher molecular weight
• It removes inorganic ash

Correct Answer: It converts resin acids into their potassium salts (soaps)

Q13. Which parameter assesses volatile impurities in colophony?

• Loss on drying or volatile matter determination
• Acid value
• pH of aqueous solution
• Optical rotation

Correct Answer: Loss on drying or volatile matter determination

Q14. Which reagent in TLC spraying is frequently used to visualize terpene and resin acid spots?

• Dragendorff’s reagent
• Vanillin–sulfuric acid reagent
• Ninhydrin
• Biuret reagent

Correct Answer: Vanillin–sulfuric acid reagent

Q15. Why is acid value critical for topical formulations containing colophony?

• High acid value indicates lower adhesive properties
• High acid value correlates with potential skin irritation and reactivity
• Acid value measures microbial contamination
• Acid value predicts color stability under light

Correct Answer: High acid value correlates with potential skin irritation and reactivity

Q16. Which chromatographic technique is preferred for separation of colophony components without derivatization?

• Reverse-phase HPLC with suitable detection
• Gel permeation chromatography for small acids
• Paper chromatography only
• Ion-exchange for neutral terpenes

Correct Answer: Reverse-phase HPLC with suitable detection

Q17. Which of the following safety concerns is most associated with colophony in pharmaceutical use?

• Severe systemic toxicity after oral dosing at low doses
• Allergic contact dermatitis in sensitive individuals
• Carcinogenicity at normal exposure levels
• Immediate anaphylaxis in all patients

Correct Answer: Allergic contact dermatitis in sensitive individuals

Q18. What does a high ash value indicate in colophony analysis?

• High organic resin content
• Presence of inorganic impurities or contamination
• Low viscosity
• High ester content

Correct Answer: Presence of inorganic impurities or contamination

Q19. Which test can help distinguish between colophony and its glycerol ester derivatives (gum rosin vs. esterified rosin)?

• Measurement of refractive index alone
• Determination of ester value or saponification value
• Color comparison by eye
• Melting point under vacuum

Correct Answer: Determination of ester value or saponification value

Q20. In IR spectroscopy of colophony, a broad band around 2500–3300 cm⁻¹ may indicate:

• Strong C–H stretches only
• Carboxylic acid O–H stretching
• N–H stretching from amines
• Triple bond C≡C stretching

Correct Answer: Carboxylic acid O–H stretching

Q21. Which mobile phase type is commonly used for TLC separation of resin acids?

• Highly polar aqueous buffers only
• Nonpolar solvents like hexane–ether mixtures
• Strong acidic aqua regia
• Pure water

Correct Answer: Nonpolar solvents like hexane–ether mixtures

Q22. What does a low saponification value relative to expected indicate in a rosin sample?

• Higher content of free acids and fewer esters
• Possible dilution with neutral non-saponifiable substances
• Excessive moisture content only
• Higher molecular weight of acids only

Correct Answer: Possible dilution with neutral non-saponifiable substances

Q23. Which preparative step is often required before GC analysis of colophony acids?

• Direct injection without treatment
• Derivatization (e.g., methylation) to form volatile esters
• Gelation to increase molecular weight
• Dialysis to remove salts

Correct Answer: Derivatization (e.g., methylation) to form volatile esters

Q24. In routine QC, what is the relevance of checking softening point of colophony?

• It identifies microbial load
• It predicts behavior in formulations and processing temperatures
• It measures acid content directly
• It shows the optical purity of resin acids

Correct Answer: It predicts behavior in formulations and processing temperatures

Q25. Which reagent would best indicate the presence of phenolic impurities in a rosin sample?

• Ferric chloride test producing color change
• Benedict’s reagent for reducing sugars
• Biuret test for proteins
• Kjeldahl digestion for nitrogen

Correct Answer: Ferric chloride test producing color change

Q26. Why is HPLC preferred over simple color tests for quantitative analysis of colophony?

• HPLC is faster but less specific than color tests
• HPLC provides accurate separation and quantitation of individual resin acids
• Color tests are always more expensive
• Color tests require large sample amounts only

Correct Answer: HPLC provides accurate separation and quantitation of individual resin acids

Q27. Which parameter is most useful to assess oxidative degradation of colophony?

• Optical rotation change only
• Increase in acid value and appearance of peroxide/oxidation products detectable by chromatography
• Decrease in ash content
• Reduction in water solubility

Correct Answer: Increase in acid value and appearance of peroxide/oxidation products detectable by chromatography

Q28. For compliance with pharmacopeial monographs, which combination of tests is typically required for colophony?

• Only color and odor
• Identification (IR/TLC), acid value, saponification value, volatile matter, and ash
• Only microbial limit tests
• Only melting point and taste

Correct Answer: Identification (IR/TLC), acid value, saponification value, volatile matter, and ash

Q29. How can tall oil (a by-product) contamination be detected in colophony?

• By measuring increased volatile terpenes only
• By specific chromatographic markers and altered acid/saponification profiles
• By checking for metallic sheen under light
• By simple solubility in water

Correct Answer: By specific chromatographic markers and altered acid/saponification profiles

Q30. What practical step should pharmacists take when using colophony-containing materials in topical products?

• Ignore patient allergy history since reactions are rare
• Assess for potential contact sensitization and label products appropriately
• Always fully neutralize rosin with acids before formulation
• Prefer raw colophony over purified grades for stability

Correct Answer: Assess for potential contact sensitization and label products appropriately

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com