Polysorbate 80 — Frequently Asked Questions

Polysorbate 80 has an HLB of about 15. HLB, the hydrophilic-lipophilic balance, runs from low values for oil-soluble emulsifiers to high values for water-soluble ones. An HLB of 15 suits oil-in-water emulsions and solubilising oils in water. It is often blended with a low-HLB sorbitan ester to match the required HLB of a specific oil phase.

The oleic acid chain in polysorbate 80 contains a double bond that can oxidise in air, forming peroxides and aldehydes. These can degrade sensitive active ingredients, cause odour and discoloration, and affect stability. Peroxide value measures this oxidation. Pharmaceutical users specify low peroxide values, and all users should store the product sealed, cool and away from light.

Polysorbate 80 is based on oleic acid (C18, unsaturated) and polysorbate 20 on lauric acid (C12, saturated). Polysorbate 80 has an HLB of about 15 and is better for emulsifying heavier oils. Polysorbate 20 has an HLB of about 16.7, is more hydrophilic and suits solubilising light oils and fragrances. Polysorbate 20 is also less prone to oxidation.

Polysorbate 80 becomes more viscous and can cloud or partly solidify at low temperatures. This is usually reversible: warm the container gently and mix before use. If cloudiness persists at room temperature, or the product has darkened or developed an odour, it may have absorbed water or oxidised; check it against the specification before use.

Polysorbates are generally treated as polymers under EU REACH and UK REACH. Polymers are exempt from registration themselves, but the monomers and reactants used to make them must be registered by the manufacturer or importer. An importer should confirm how these are covered for the specific import and keep that confirmation on file.