Methods of preparation of emulsions MCQs With Answer

Introduction: Emulsions are key dosage forms in pharmaceutics, enabling delivery of poorly water-soluble drugs via stable oil-in-water (o/w) or water-in-oil (w/o) systems. This overview focuses on methods of preparation of emulsions for B. Pharm students: dry gum (continental), wet gum (English), Forbes bottle method, in-situ soap (nascent soap) method, and modern techniques like high-shear mixing, high-pressure homogenization, ultrasonication, microfluidization, and low-energy approaches (PIT/EIP, spontaneous emulsification). Core concepts include primary emulsion ratios (4:2:1), order of addition, emulsifying agents, HLB selection, phase inversion strategies, and practical cues (click sound, viscosity rise). Mastering these techniques ensures effective formulation, stability, and scalability in pharmacy practice. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which statement best describes the dry gum (continental) method?

• Triturate gum with oil, then add all water at once and triturate until a click sound and thick primary emulsion forms
• Make gum mucilage first, then add oil in portions with trituration
• Shake oil and gum in a bottle with incremental water additions
• Heat oil and water above PIT to invert phases

Correct Answer: Triturate gum with oil, then add all water at once and triturate until a click sound and thick primary emulsion forms

Q2. The standard primary emulsion ratio for fixed oils with acacia in the dry gum method is:

• 4:2:1 (oil:water:gum)
• 1:2:4 (oil:water:gum)
• 2:2:1 (oil:water:gum)
• 3:2:1 (oil:water:gum)

Correct Answer: 4:2:1 (oil:water:gum)

Q3. For volatile oils using acacia, the commonly recommended primary emulsion ratio is:

• 2:2:1 (oil:water:gum)
• 4:2:1 (oil:water:gum)
• 3:2:1 (oil:water:gum)
• 1:1:1 (oil:water:gum)

Correct Answer: 2:2:1 (oil:water:gum)

Q4. In the English (wet gum) method, the first critical step is to:

• Prepare mucilage by triturating acacia with twice its weight of water
• Mix gum with oil first
• Homogenize under 1000 bar
• Add lime water to oil

Correct Answer: Prepare mucilage by triturating acacia with twice its weight of water

Q5. The Forbes bottle method is preferred when:

• Using volatile or low-viscosity oils
• Working with very viscous oils
• Preparing sterile injectable emulsions
• Nanometer-sized droplets are required

Correct Answer: Using volatile or low-viscosity oils

Q6. A practical sign that the primary emulsion has formed in the dry gum method is:

• A clicking sound and increased viscosity
• Rapid phase separation
• A clear, transparent solution
• A strong ammonia-like odor

Correct Answer: A clicking sound and increased viscosity

Q7. The in-situ soap method using lime water produces primarily:

• w/o emulsion via calcium oleate formation
• o/w emulsion via sodium oleate formation
• A microemulsion without added surfactant
• A solid dispersion rather than an emulsion

Correct Answer: w/o emulsion via calcium oleate formation

Q8. The phase inversion temperature (PIT) method relies on:

• Temperature-dependent hydrophilic-lipophilic balance of nonionic surfactants
• Electrolyte complexation at the interface
• Protein denaturation at high temperature
• Mechanical entrapment by hydrogels

Correct Answer: Temperature-dependent hydrophilic-lipophilic balance of nonionic surfactants

Q9. High-pressure homogenization typically operates at:

• 100–1500 bar
• 1–5 bar
• 5000–10,000 bar
• Under vacuum only

Correct Answer: 100–1500 bar

Q10. Ultrasonication during emulsion preparation primarily reduces droplet size by:

• Cavitation and microturbulence
• Simple diffusion across the interface
• Freeze-drying of droplets
• Osmotic swelling of the dispersed phase

Correct Answer: Cavitation and microturbulence

Q11. Microfluidization achieves narrow droplet size distribution by:

• Forcing fluids through microchannels with impingement
• Stirring at 50 rpm
• Filtration through a 0.45 μm membrane
• Heating above the PIT only

Correct Answer: Forcing fluids through microchannels with impingement

Q12. In the dry gum method, adding water slowly dropwise initially will most likely:

• Fail to form a stable primary emulsion
• Improve droplet size uniformity
• Prevent the click sound but still succeed
• Increase the HLB of the surfactant blend

Correct Answer: Fail to form a stable primary emulsion

Q13. For very viscous oils, the more suitable hand method is:

• Wet gum (English) method
• Dry gum (continental) method
• Forbes bottle method
• PIT method

Correct Answer: Wet gum (English) method

Q14. When using acacia in the wet gum method, oil is added:

• In small portions with continuous trituration to the mucilage
• All at once to the dry gum
• After heating both phases to 70°C
• Only after high-pressure homogenization

Correct Answer: In small portions with continuous trituration to the mucilage

Q15. For preparing o/w emulsions, the required HLB of the emulsifier blend is generally:

• 8–18
• 3–6
• 1–3
• >20 only

Correct Answer: 8–18

Q16. The role of a co-surfactant (e.g., short-chain alcohol) in low-energy spontaneous emulsification is to:

• Reduce interfacial tension and facilitate interfacial curvature
• Increase Ostwald ripening rate
• Act only as a preservative
• Neutralize acids in the oil phase

Correct Answer: Reduce interfacial tension and facilitate interfacial curvature

Q17. In the bottle method, the ideal bottle should be filled to about:

• One-third to one-half of its capacity
• Completely full to exclude air
• Less than 10% capacity
• Exactly 90% capacity

Correct Answer: One-third to one-half of its capacity

Q18. Which sequence correctly describes the dry gum method using the 4:2:1 ratio?

• Triturate 1 part gum with 4 parts oil, then add 2 parts water at once
• Triturate 4 parts oil with 2 parts water, then add gum
• Triturate 2 parts water with 1 part gum, then add oil
• Shake all components together without trituration

Correct Answer: Triturate 1 part gum with 4 parts oil, then add 2 parts water at once

Q19. The Bancroft rule applied to emulsion preparation states that:

• The phase in which the emulsifier is more soluble tends to become the continuous phase
• Oil always becomes the continuous phase
• Water always becomes the continuous phase
• Particle size alone dictates the continuous phase

Correct Answer: The phase in which the emulsifier is more soluble tends to become the continuous phase

Q20. In the in-situ soap method to make an o/w emulsion, one may react:

• Oleic acid with sodium hydroxide to form sodium oleate
• Oleic acid with calcium hydroxide to form calcium oleate
• Stearic acid with aluminum chloride
• Palmitic acid with magnesium sulfate

Correct Answer: Oleic acid with sodium hydroxide to form sodium oleate

Q21. The emulsion inversion point (EIP) method achieves inversion primarily by:

• Gradually increasing the volume fraction of the dispersed phase
• Rapid cooling below freezing
• Adding excess preservative
• Evaporating solvent from the oil phase

Correct Answer: Gradually increasing the volume fraction of the dispersed phase

Q22. Compared to hand methods, high-shear rotor–stator mixing typically produces:

• Smaller mean droplet sizes and a narrower distribution
• Larger droplets with broad distribution
• No emulsification at all
• Only w/o emulsions

Correct Answer: Smaller mean droplet sizes and a narrower distribution

Q23. For acacia-based primary emulsions, a stabilizer often added after primary formation is:

• A viscosity enhancer like tragacanth or syrup
• Hydrochloric acid
• A strong oxidizer
• Heavy metal salts

Correct Answer: A viscosity enhancer like tragacanth or syrup

Q24. A common mistake leading to failure in the dry gum method is:

• Adding water incrementally rather than all at once
• Rotating the pestle at a steady speed
• Pre-wetting gum with water first
• Using a cool porcelain mortar

Correct Answer: Adding water incrementally rather than all at once

Q25. During the wet gum method, initial mucilage is prepared with:

• Gum plus water in a ratio of 1:2 by weight
• Oil plus water in a ratio of 1:1 by volume
• Gum plus oil in a ratio of 1:4 by weight
• Gum plus water in a ratio of 1:1 by weight

Correct Answer: Gum plus water in a ratio of 1:2 by weight

Q26. For sterile parenteral emulsions, the preferred approach is:

• Submicron droplets via high-pressure homogenization under aseptic conditions
• Large droplets via the bottle method
• Hand trituration only
• Ultrasonication in an open beaker

Correct Answer: Submicron droplets via high-pressure homogenization under aseptic conditions

Q27. Which method is particularly useful for preparing flavoring oil emulsions for oral drops at room temperature?

• Forbes bottle method
• PIT method
• High-pressure homogenization only
• Wet gum method with heating

Correct Answer: Forbes bottle method

Q28. When preparing an emulsion by the PIT method, droplets are “fixed” by:

• Rapid cooling from just above the PIT to below the PIT
• Adding an electrolyte to the oil phase
• Increasing oil viscosity only
• Using cationic surfactants exclusively

Correct Answer: Rapid cooling from just above the PIT to below the PIT

Q29. In practice, when adding preservatives to emulsions, formulators should:

• Dissolve oil-soluble preservatives in the oil phase and water-soluble in the aqueous phase prior to emulsification
• Always add preservatives only after homogenization
• Dissolve all preservatives in the water phase regardless of solubility
• Avoid using preservatives together with surfactants

Correct Answer: Dissolve oil-soluble preservatives in the oil phase and water-soluble in the aqueous phase prior to emulsification

Q30. A quick test to confirm o/w type immediately after preparation is:

• Dilution with water increases volume without separation
• Dilution with oil is effortless and stable
• An oil-soluble dye dissolves uniformly in the continuous phase
• The system is nonconductive to electricity

Correct Answer: Dilution with water increases volume without separation

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