HLb

HLB, in the context of chemistry and formulation science, most commonly refers to Hydrophilic-Lipophilic Balance. It is a numerical scale used to predict the emulsifying behavior of surfactants and their blends, guiding the selection of surfactants for oil-in-water (O/W) versus water-in-oil (W/O) emulsions.

The concept was developed in the mid-20th century by William Griffin to quantify the balance between a surfactant’s hydrophilic (water-loving) and lipophilic (oil-loving) portions. The number typically ranges from 0 to 20, where lower values indicate lipophilicity and higher values indicate hydrophilicity. Surfactants assigned higher HLB values tend to favor forming O/W emulsions, while those with lower values favor W/O systems.

Calculation and use: The HLB of a surfactant is determined either by group-contribution methods (such as Griffin’s or Davies’ approaches) or by experimental calibration. For formulators, missing HLB targets can be achieved by blending surfactants to reach a desired effective HLB. As a rule of thumb, oil-in-water emulsions generally use surfactants with HLB values around 8 to 12 or blends that yield an effective HLB in that range; water-in-oil emulsions typically require lower HLB values, roughly 3 to 6.

Limitations and scope: HLB is an approximate guide that assumes ideal mixing and does not fully capture dynamic interfacial phenomena, concentration effects, temperature dependence, or the presence of electrolytes and polymers. It is most reliable for nonionic surfactants and can be less predictive for complex mixtures or highly polar oils.

In common practice, HLB informs surfactant selection and formulation design in cosmetics, food, pharmaceuticals, and industrial emulsions, offering a practical starting point for achieving stable emulsions.