Which HLB range is suitable for stabilizing oil-in-water emulsions?

• A. 3.8 to 8
• B. 12 to 20
• C. 8 to 16
• D. 20 to 30

Answer: (C)

For oil-in-water emulsions, you want a surfactant that is more hydrophilic so it stabilizes droplets dispersed in the water phase. The HLB scale ranges from about 0 (lipophilic) to about 20 (hydrophilic). Higher HLB values mean the surfactant prefers water, which helps form and stabilize an oil-in-water system by creating a protective shell around oil droplets and lowering interfacial tension with the aqueous phase.

The typical range for stabilizing oil-in-water emulsions is around 8 to 16. This band includes most common hydrophilic emulsifiers and blends that effectively stabilize oil droplets in water. Range values much lower tend toward water-in-oil emulsions, while very high ranges can still work but are less commonly used and can lead to excessive water solubility or other issues. Thus, 8–16 is the best general fit for O/W stabilization.

In short, emulsions with water as the continuous phase are best stabilized by surfactants with relatively high HLB values, roughly 8–16.