HLB method for emulsion formulation is a practical approach used in pharmaceutical formulation to select and blend surfactants by their hydrophilic-lipophilic balance. The HLB concept assigns a numerical value to surfactants that predicts their affinity for oil or water phases, aiding stable oil-in-water and water-in-oil emulsion design. B. Pharm students should grasp HLB calculation, blending formulas, typical HLB ranges, selection of nonionic surfactants (e.g., Tweens and Spans), and limitations such as temperature and ionic effects. Mastery of HLB complements skills in droplet size control, stability testing, and homogenization techniques for robust topical and oral emulsion dosage forms. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary purpose of the HLB method in emulsion formulation?
- To determine the molecular weight of surfactants
- To select surfactants by matching hydrophilic-lipophilic balance to the oil phase
- To measure the pH sensitivity of emulsions
- To calculate drug solubility in water
Correct Answer: To select surfactants by matching hydrophilic-lipophilic balance to the oil phase
Q2. What is the usual numerical range of the HLB scale used in formulation?
- 0 to 5
- 5 to 10
- 0 to 20
- 20 to 40
Correct Answer: 0 to 20
Q3. A higher HLB value for a surfactant indicates which characteristic?
- More lipophilic character
- Higher molecular weight
- More hydrophilic character
- Greater ionic charge
Correct Answer: More hydrophilic character
Q4. Which surfactant is considered relatively lipophilic and often used for W/O emulsions?
- Tween 80 (polysorbate 80)
- Span 80 (sorbitan monooleate)
- Poloxamer 188
- Sodium lauryl sulfate
Correct Answer: Span 80 (sorbitan monooleate)
Q5. Which of the following surfactants has a high HLB and is commonly used for O/W emulsions?
- Span 60
- Tween 80
- Glyceryl monostearate
- Lanolin
Correct Answer: Tween 80
Q6. Typical required HLB range for oil-in-water (O/W) emulsions is:
- 3–6
- 6–8
- 8–18
- 18–25
Correct Answer: 8–18
Q7. Typical required HLB range for water-in-oil (W/O) emulsions is:
- 0–2
- 3–6
- 8–12
- 12–18
Correct Answer: 3–6
Q8. Which formula expresses the HLB of a blend of two surfactants?
- HLBmix = HLB1 + HLB2
- HLBmix = (HLB1 × HLB2) / 2
- HLBmix = fractionA×HLBA + fractionB×HLBB
- HLBmix = HLB1 − HLB2
Correct Answer: HLBmix = fractionA×HLBA + fractionB×HLBB
Q9. If two surfactants with HLB values 4 and 16 are mixed in equal weight proportions, the resulting HLB is:
- 4
- 8
- 10
- 16
Correct Answer: 10
Q10. An oil requires HLB 10. You have two surfactants HLB 8 and HLB 12. What weight fraction of the HLB 12 surfactant is needed?
- 25%
- 50%
- 75%
- 100%
Correct Answer: 50%
Q11. The HLB method is most reliable for which class of surfactants?
- Anionic surfactants
- Cationic surfactants
- Nonionic surfactants
- Zwitterionic surfactants
Correct Answer: Nonionic surfactants
Q12. Increasing the overall HLB of an emulsifier blend generally favors formation of which emulsion type?
- Water-in-oil (W/O)
- Oil-in-water (O/W)
- Microemulsion regardless of composition
- No change in emulsion type
Correct Answer: Oil-in-water (O/W)
Q13. Phase inversion from O/W to W/O can be promoted by which change in HLB?
- Increasing overall HLB substantially
- Decreasing overall HLB below the oil’s required HLB
- Keeping HLB constant
- Switching from nonionic to ionic surfactants without HLB change
Correct Answer: Decreasing overall HLB below the oil’s required HLB
Q14. Which statement about HLB and temperature is correct?
- HLB values are absolutely constant with temperature for all surfactants
- Ethoxylated (polyoxyethylene) surfactant behavior can change with temperature
- Temperature only affects ionic surfactants, not HLB
- HLB increases linearly with temperature for all surfactants
Correct Answer: Ethoxylated (polyoxyethylene) surfactant behavior can change with temperature
Q15. Which measurement gives a direct indication of emulsion stability related to coalescence?
- pH measurement
- Droplet size distribution
- Viscosity alone
- Colorimetric assay
Correct Answer: Droplet size distribution
Q16. Why are surfactant blends often used instead of a single surfactant?
- Blends are always cheaper
- To reach a target HLB and achieve synergistic interfacial properties
- To avoid regulatory requirements
- To increase drug solubility only
Correct Answer: To reach a target HLB and achieve synergistic interfacial properties
Q17. Which statement is true about required HLB of an oil phase?
- Required HLB is a fixed universal constant for all oils
- Required HLB depends on the oil’s chemical composition and affects surfactant selection
- Required HLB equals surfactant HLB
- Required HLB is irrelevant for emulsion stability
Correct Answer: Required HLB depends on the oil’s chemical composition and affects surfactant selection
Q18. Which of the following is a high-HLB surfactant commonly used for O/W emulsions?
- Polysorbate 80 (Tween 80)
- Sorbitan tristearate (Span 65)
- Stearic acid
- Beeswax
Correct Answer: Polysorbate 80 (Tween 80)
Q19. A key limitation of the HLB method is:
- It accounts for electrolyte and pH effects too precisely
- It predicts chemical stability of drugs in emulsions
- It does not fully account for electrolyte, temperature, and co-solvent effects
- It renders experimental testing unnecessary
Correct Answer: It does not fully account for electrolyte, temperature, and co-solvent effects
Q20. Which experimental alternative method is commonly used alongside HLB to select emulsifiers?
- Loss on drying
- Phase inversion temperature (PIT) method
- Karl Fischer titration
- Thin-layer chromatography
Correct Answer: Phase inversion temperature (PIT) method
Q21. The HLB method is less predictive when formulating with which surfactant type?
- Nonionic surfactants
- Anionic or cationic (ionic) surfactants
- Polyglycerol esters
- Polymeric emulsifiers
Correct Answer: Anionic or cationic (ionic) surfactants
Q22. For microemulsion systems, the HLB approach is generally:
- Highly accurate and sufficient alone
- Not suitable alone; microemulsions require different selection strategies
- Identical to macroemulsion formulation
- Only used for ionic surfactants
Correct Answer: Not suitable alone; microemulsions require different selection strategies
Q23. If the required HLB of an oil increases, what is the practical implication for surfactant selection?
- Use more lipophilic surfactants
- Increase the proportion of hydrophilic surfactant(s)
- Reduce surfactant concentration to zero
- Switch to solid dispersions
Correct Answer: Increase the proportion of hydrophilic surfactant(s)
Q24. To prepare a blend with target HLB 10 using Span 80 (HLB 4.3) and Tween 20 (HLB 16.7), the approximate weight fraction of Tween 20 required is:
- ~20%
- ~33%
- ~46%
- ~75%
Correct Answer: ~46%
Q25. Co-surfactants are added to an emulsion primarily to:
- Increase oil viscosity only
- Reduce interfacial tension and improve interfacial packing
- Serve as preservatives
- Adjust the pH to neutral
Correct Answer: Reduce interfacial tension and improve interfacial packing
Q26. Zeta potential measurement in emulsions is most useful to assess:
- Electrostatic stabilization and likelihood of flocculation
- HLB value directly
- Drug content uniformity
- Water activity
Correct Answer: Electrostatic stabilization and likelihood of flocculation
Q27. A practical concentration range of surfactants commonly used in pharmaceutical emulsions is:
- 0.001–0.01% w/w
- 0.05–0.5% w/w
- 1–10% w/w
- 30–50% w/w
Correct Answer: 1–10% w/w
Q28. Which homogenization technique is most suitable to produce nanosized emulsions for drug delivery?
- Simple magnetic stirring
- Manual shaking
- Microfluidization / high-pressure homogenization
- Gentle overhead stirring
Correct Answer: Microfluidization / high-pressure homogenization
Q29. An emulsion formulated with a predominance of high-HLB surfactant will most likely have which continuous phase?
- Oil continuous (W/O)
- Water continuous (O/W)
- Solid continuous
- Gas continuous
Correct Answer: Water continuous (O/W)
Q30. Which simple laboratory test most directly indicates whether an emulsion is O/W or W/O?
- Viscosity measurement
- Electrical conductivity test
- Thin-layer chromatography
- Infrared spectroscopy
Correct Answer: Electrical conductivity test
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.
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