Calculation of the HLB – How to choose an emulsifier?

For most non-ionic emulsifiers, the HLB value can be calculated based on their theoretical composition or more accurately, based on analytical data. The theoretical composition can in fact only lead to approximate HLB values because the chemical classification is often only an approximation of the actual composition. The data obtained from an analysis of the surfactant are usually the best basis for determining the HLB. If ethylene oxide is the only component of the hydrophilic part of the emulsifier, the HLB can be calculated using the following formula:

HLB = E/5

 where E = percentage of ethylene oxide.

For emulsifiers made up of esters, fatty acids and polyols the formula is

HLB = 20 (1 – S/A)

where S = saponification value and A = acidity value of the fatty acid.

For example, for Polysorbate 20: HLB = 20 (1 – 45.5/276) = 16.7

When two or more emulsifiers are mixed together, the HLB value of the mixture can be easily calculated. For example, for a mixture containing 70% Polysorbate 80 (HLB = 15.0) and 30% Sorbitan oleate (HLB = 4.3) the HLB value is obtained in the following way:
Polysorbate 80 70% x 15.0 = 10.5
Sorbitan oleate 30% x 4.3 = 1.3
HLB of the mixture = 11.8

In the following table some of the more representative emulsifiers are listed in order of increasing HLB.