HLB – Sense or Nonsense?

The Hydrophilic/Lipophilic Balance (HLB) concept as introduced by Griffin in 1949 means assigning a single number between 0 and 20 to fatty alcohol ethoxylates in order to describe their hydrophilicity/lipophilicity and assuming that this number is useful to predict the applicability as emulsifier. This approach has severe limitations as it ignores crucial parameters such as temperature, presence of the oil phase, pH, salt, or processing during emulsion manufacturing. However, despite these deficiencies, HLB values are still given today by the surfactant manufacturers in their brochures and product documentations. The only meaningful purpose of the HLB value is that it provides (especially in case it has been determined experimentally) a rough guesstimate of the water solubility or dispersability of an emulsifier. All other properties, often a consequence of the molecular architecture especially of polymeric emulsifiers, cannot be predicted by a single HLB value. This paper critically discusses the limitations of the HLB concept in order to avoid misconceptions, especially when dealing with non-fatty-alcohol-ethoxylate amphiphiles.