Multiple emulsions MCQs With Answer

Multiple emulsions MCQs With Answer provide B. Pharm students a focused, exam-ready study tool on complex carrier systems like W/O/W and O/W/O. This Student-friendly post covers key concepts—definition, preparation methods (two-step, membrane, phase inversion), stabilizers, HLB selection, characterization (droplet size, zeta potential, encapsulation efficiency) and major stability challenges such as coalescence, Ostwald ripening and leakage. Ideal for pharmacy coursework and competitive exams, these multiple choice questions deepen understanding of formulation strategies, release mechanisms, analytical techniques and pharmaceutical applications including controlled release and taste masking. Clear explanations and targeted practice boost retention and practical formulation skills. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is a multiple emulsion?

• An emulsion containing droplets of one liquid dispersed within droplets of another liquid, which are in turn dispersed in a continuous phase
• An emulsion stabilized by only one surfactant type
• A simple oil-in-water emulsion with added polymer
• A suspension of solid particles in an oil phase

Correct Answer: An emulsion containing droplets of one liquid dispersed within droplets of another liquid, which are in turn dispersed in a continuous phase

Q2. Which of the following is an example of a multiple emulsion type?

• W/O/W
• O/W
• S/W
• G/O

Correct Answer: W/O/W

Q3. In a W/O/W emulsion, what does the inner phase consist of?

• Water droplets encapsulated in oil droplets
• Oil droplets dispersed in water
• Solid particles suspended in oil
• Gas bubbles dispersed in water

Correct Answer: Water droplets encapsulated in oil droplets

Q4. Which preparation method involves creating a primary emulsion followed by emulsification into a second continuous phase?

• Two-step (multiple) emulsification
• Phase inversion temperature
• Spontaneous emulsification
• Solvent evaporation

Correct Answer: Two-step (multiple) emulsification

Q5. Which surfactant characteristic is most important when selecting emulsifiers for multiple emulsions?

• Hydrophilic-lipophilic balance (HLB)
• Color index
• Viscosity at 0°C
• Melting point

Correct Answer: Hydrophilic-lipophilic balance (HLB)

Q6. For a W/O primary emulsion in a W/O/W system, the surfactant used primarily should be:

• Primarily lipophilic
• Strongly hydrophilic
• Neutral polymeric only
• Anionic electrolyte

Correct Answer: Primarily lipophilic

Q7. Which instability phenomenon specifically refers to growth of larger droplets at the expense of smaller ones?

• Ostwald ripening
• Creaming
• Flocculation
• Coalescence

Correct Answer: Ostwald ripening

Q8. Which analytical technique is commonly used to measure droplet size distribution in multiple emulsions?

• Laser diffraction (dynamic light scattering)
• Gas chromatography
• UV-Visible spectroscopy
• Titration

Correct Answer: Laser diffraction (dynamic light scattering)

Q9. Encapsulation efficiency in multiple emulsions refers to:

• The percentage of drug retained within the internal droplets relative to the total drug added
• The viscosity of the continuous phase
• The electrical conductivity of the outer phase
• The pH stability range of the emulsion

Correct Answer: The percentage of drug retained within the internal droplets relative to the total drug added

Q10. Which factor helps prevent leakage of hydrophilic drug from the inner aqueous phase in W/O/W emulsions?

• Using an appropriate lipophilic surfactant and osmotic balance
• Increasing temperature above 100°C
• Removing all emulsifiers
• Reducing oil viscosity to zero

Correct Answer: Using an appropriate lipophilic surfactant and osmotic balance

Q11. What role does osmotic pressure play in multiple emulsions?

• Imbalance causes swelling or shrinkage of inner droplets, promoting leakage
• It changes color but not stability
• It only affects solid suspensions, not emulsions
• It increases thermal conductivity

Correct Answer: Imbalance causes swelling or shrinkage of inner droplets, promoting leakage

Q12. Which method can reduce droplet size and improve stability during primary emulsion formation?

• High-shear homogenization or ultrasonication
• Slow stirring at ambient speed only
• Heating above 300°C
• Adding sugar crystals

Correct Answer: High-shear homogenization or ultrasonication

Q13. Which property measured by zeta potential is most relevant for emulsion stability?

• Surface charge that predicts electrostatic repulsion between droplets
• Magnetic susceptibility of droplets
• Thermal expansion coefficient
• Optical density at 600 nm

Correct Answer: Surface charge that predicts electrostatic repulsion between droplets

Q14. Phase inversion in emulsions refers to:

• Change of continuous phase from oil to water or vice versa
• Complete solidification of droplets
• Polymerization of surfactants
• Formation of gas bubbles within droplets

Correct Answer: Change of continuous phase from oil to water or vice versa

Q15. Membrane emulsification is advantageous because it:

• Produces narrow, controlled droplet size distributions
• Eliminates the need for any surfactants
• Requires no equipment and is spontaneous
• Is only suitable for gas-in-liquid systems

Correct Answer: Produces narrow, controlled droplet size distributions

Q16. Which surfactant combination is typically used to stabilize W/O/W multiple emulsions?

• Low HLB (lipophilic) for inner interface and high HLB (hydrophilic) for outer interface
• High HLB surfactants only for both interfaces
• No surfactant in inner interface and polymer in outer
• Only ionic surfactants with identical HLB values

Correct Answer: Low HLB (lipophilic) for inner interface and high HLB (hydrophilic) for outer interface

Q17. Which application is a common pharmaceutical use of multiple emulsions?

• Controlled release of hydrophilic drugs
• Immediate dissolution of hydrophobic tablets
• Sterilization of injection vials
• Replacing enteric coatings for all drugs

Correct Answer: Controlled release of hydrophilic drugs

Q18. How does increasing oil phase viscosity generally affect multiple emulsion stability?

• It reduces droplet coalescence and creaming, improving stability
• It always destabilizes emulsions by increasing Ostwald ripening
• It converts the system into a solid gel instantly
• It has no effect on emulsion stability

Correct Answer: It reduces droplet coalescence and creaming, improving stability

Q19. Electrical conductivity measurement of a multiple emulsion primarily indicates:

• Continuity of the aqueous phase and leakage of internal water
• Optical clarity of the emulsion
• Oil phase polarity only
• Presence of volatile organic solvents

Correct Answer: Continuity of the aqueous phase and leakage of internal water

Q20. Which parameter directly affects release kinetics from inner aqueous droplets of W/O/W emulsions?

• Partition coefficient of drug between inner and outer phases
• Color of the oil phase
• Electrical conductivity of oil
• Magnetic properties of surfactant

Correct Answer: Partition coefficient of drug between inner and outer phases

Q21. Which is a typical preservative concern in multiple emulsions?

• Limited access of preservative to inner aqueous phase leading to microbial growth
• Preservatives always increase stability without drawbacks
• Preservatives crystallize and form solids only
• Preservatives neutralize surfactants and cause inversion

Correct Answer: Limited access of preservative to inner aqueous phase leading to microbial growth

Q22. Entrapment of enzymes in multiple emulsions is primarily used for:

• Protecting enzyme activity and controlling release
• Denaturing them faster
• Increasing viscosity without functional benefit
• Improving gas solubility

Correct Answer: Protecting enzyme activity and controlling release

Q23. Which test can visually assess the internal droplet structure of multiple emulsions?

• Confocal laser scanning microscopy
• pH meter measurement
• Thermogravimetric analysis
• Refractometry

Correct Answer: Confocal laser scanning microscopy

Q24. What is the effect of electrolytes (e.g., NaCl) on ionic surfactant-stabilized multiple emulsions?

• Electrolytes can screen charges and reduce repulsion, promoting coalescence
• They always stabilize emulsions by increasing zeta potential
• They transform emulsions into microcrystals
• They have no effect if surfactants are present

Correct Answer: Electrolytes can screen charges and reduce repulsion, promoting coalescence

Q25. A major drawback of multiple emulsions for oral delivery is:

• Potential instability and drug leakage during GI transit
• Their inability to encapsulate hydrophilic drugs
• They are always toxic and cannot be used orally
• Lack of any surfactant requirement

Correct Answer: Potential instability and drug leakage during GI transit

Q26. Which release mechanism is most common for drugs from multiple emulsions?

• Diffusion through the oil layer and outer aqueous phase
• Immediate vaporization from inner droplets
• Conversion to gas and rapid ejection
• Solid-state diffusion through crystals

Correct Answer: Diffusion through the oil layer and outer aqueous phase

Q27. The HLB system helps formulators to:

• Select appropriate surfactants for desired oil/water emulsification
• Measure droplet size directly
• Determine pH of the internal phase
• Calculate polymer molecular weight

Correct Answer: Select appropriate surfactants for desired oil/water emulsification

Q28. Which oil property should be considered to reduce diffusion of hydrophilic drugs out of inner droplets?

• Low water solubility and high viscosity
• High refractive index
• High volatility
• High melting point above 200°C

Correct Answer: Low water solubility and high viscosity

Q29. Which of the following can be used as a polymeric stabilizer in multiple emulsions?

• Polyvinyl alcohol (PVA)
• Calcium carbonate powder
• Pure ethanol
• Gaseous CO2

Correct Answer: Polyvinyl alcohol (PVA)

Q30. Which parameter indicates the potential for creaming in an emulsion?

• Density difference between dispersed droplets and continuous phase
• Zeta potential only
• Type of preservative used
• Presence of UV light

Correct Answer: Density difference between dispersed droplets and continuous phase

Q31. Which type of multiple emulsion is more suitable for encapsulating lipophilic drugs?

• O/W/O
• W/O/W
• W/W/W
• G/O/W

Correct Answer: O/W/O

Q32. Spontaneous emulsification relies mainly on:

• Interfacial turbulence and rapid mixing due to composition changes, not high shear
• High temperature above boiling point
• Mechanical milling of solids
• Gamma irradiation

Correct Answer: Interfacial turbulence and rapid mixing due to composition changes, not high shear

Q33. A common strategy to improve long-term stability of multiple emulsions is:

• Using a combination of surfactants and polymers to strengthen interfaces
• Removing all water from the formulation
• Adding strong acids to denature proteins
• Storing at extremely high temperatures only

Correct Answer: Using a combination of surfactants and polymers to strengthen interfaces

Q34. Which parameter is NOT directly used to characterize multiple emulsions?

• Melting point of external container
• Droplet size distribution
• Zeta potential
• Encapsulation efficiency

Correct Answer: Melting point of external container

Q35. Leakage of solute from inner phase is often accelerated by:

• High partition coefficient favoring transfer to outer phase and osmotic gradients
• Complete absence of surfactants only
• Addition of insoluble salts that never dissolve
• Lowering temperature to absolute zero

Correct Answer: High partition coefficient favoring transfer to outer phase and osmotic gradients

Q36. What is the expected effect of adding a cosurfactant like sorbitan monooleate to the oil phase?

• Enhances stability of W/O primary emulsion by lowering interfacial tension
• Instantly converts the system into a solid
• Removes all water from inner droplets
• Increases electrical conductivity of oil

Correct Answer: Enhances stability of W/O primary emulsion by lowering interfacial tension

Q37. Which instability involves aggregation of droplets without fusion?

• Flocculation
• Coalescence
• Ostwald ripening
• Crystallization

Correct Answer: Flocculation

Q38. Which excipient can be used to control osmotic differences between internal and external aqueous phases?

• Sorbitol or sucrose as tonicity agents
• Magnesium oxide to raise pH dramatically
• Pure sodium metal
• Liquid nitrogen

Correct Answer: Sorbitol or sucrose as tonicity agents

Q39. Which industrial consideration is critical for scaling up multiple emulsion production?

• Reproducible droplet size control and shear conditions
• Color matching with packaging only
• Use of household blenders exclusively
• Ignoring surfactant quality

Correct Answer: Reproducible droplet size control and shear conditions

Q40. Which technique helps to quantify the amount of drug in the inner phase after preparation?

• Phase separation followed by analytical assay (e.g., HPLC) of separated phases
• Measuring viscosity of the whole emulsion only
• Estimating by color alone
• Using taste as the only metric

Correct Answer: Phase separation followed by analytical assay (e.g., HPLC) of separated phases

Q41. Which factor is least likely to increase coalescence in multiple emulsions?

• High interfacial film strength
• Insufficient emulsifier concentration
• Mechanical stress during handling
• Presence of destabilizing electrolytes

Correct Answer: High interfacial film strength

Q42. What is the likely effect of increasing temperature during storage on multiple emulsions?

• Acceleration of destabilization processes like coalescence and Ostwald ripening
• Permanent solidification and rigidification of interfaces beneficially
• Complete removal of surfactants making them safer
• No effect at all irrespective of formulation

Correct Answer: Acceleration of destabilization processes like coalescence and Ostwald ripening

Q43. Which is an advantage of multiple emulsions in topical formulations?

• Sustained release and localized delivery of actives
• Instant systemic absorption through skin always
• Guaranteed sterilization of skin upon application
• Complete prevention of all skin irritation

Correct Answer: Sustained release and localized delivery of actives

Q44. What is the primary role of the outer hydrophilic surfactant in a W/O/W emulsion?

• Stabilize oil droplets in the outer aqueous continuous phase
• Make the oil phase evaporate faster
• Convert water into oil chemically
• Bind covalently to drug molecules

Correct Answer: Stabilize oil droplets in the outer aqueous continuous phase

Q45. For parenteral multiple emulsions, which concern is most critical?

• Sterility and pyrogenicity control
• Color matching with injection syringe
• Ability to foam excessively during injection
• High sugar content only

Correct Answer: Sterility and pyrogenicity control

Q46. Which parameter would you adjust to slow drug diffusion through the oil membrane?

• Increase oil viscosity and decrease drug solubility in oil
• Decrease oil viscosity and increase drug solubility in oil
• Increase temperature to above boiling
• Add gas to the oil phase

Correct Answer: Increase oil viscosity and decrease drug solubility in oil

Q47. In microencapsulation via multiple emulsions, which step is essential before solvent removal?

• Create a stable primary emulsion and disperse into secondary phase to form multiple emulsion
• Evaporate all water immediately at room temperature
• Add free radicals to initiate polymerization uncontrollably
• Freeze the system below -200°C

Correct Answer: Create a stable primary emulsion and disperse into secondary phase to form multiple emulsion

Q48. Which parameter best indicates successful entrapment of a hydrophilic drug in inner aqueous droplets?

• High encapsulation efficiency and low concentration in outer phase
• Low viscosity of the whole emulsion only
• Complete absence of any surfactant signal in analysis
• High electrical conductivity of oil phase

Correct Answer: High encapsulation efficiency and low concentration in outer phase

Q49. Which surfactant type is generally avoided in W/O primary emulsions when the inner aqueous phase contains proteins?

• Strongly denaturing surfactants such as SDS (sodium dodecyl sulfate)
• Nonionic surfactants like Tween at mild concentrations
• Biocompatible polymeric stabilizers
• Glycerol as a tonicity agent

Correct Answer: Strongly denaturing surfactants such as SDS (sodium dodecyl sulfate)

Q50. Which formulation approach can improve taste masking using multiple emulsions in oral products?

• Encapsulating bitter drug in inner aqueous droplets within a lipophilic oil barrier
• Adding sugar on top of outer phase only
• Using only volatile solvents with no encapsulation
• Reducing droplet size to zero

Correct Answer: Encapsulating bitter drug in inner aqueous droplets within a lipophilic oil barrier

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