Polysorbate

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Polysorbates are a class of emulsifiers used in some pharmaceuticals and food preparation. They are often used in cosmetics to solubilize essential oils into water-based products. Polysorbates are oily liquids derived from PEG-ylated sorbitan (a derivative of sorbitol) esterified with fatty acids. Surfactants that are esters of plain (non-PEG-ylated) sorbitan with fatty acids are usually referred to by the name Span.

[edit] Examples

Polysorbate 20 (Tween 20 or polyoxyethylene (20) sorbitan monolaurate)
Polysorbate 40 (Tween 40 or polyoxyethylene (20) sorbitan monopalmitate)
Polysorbate 60 (Tween 60 or polyoxyethylene (20) sorbitan monostearate)
Polysorbate 80 (Tween 80 or polyoxyethylene (20) sorbitan monooleate)

The number 20 following the polyoxyethylene part refers to the total number of oxyethylene -(CH₂CH₂O)- groups found in the molecule. The number following the polysorbate part is related to the type of fatty acid associated with the polyoxyethylene sorbitan part of the molecule. Monolaurate is indicated by 20, monopalmitate is indicated by 40, monostearate by 60 and monooleate by 80. The same numbering is followed in their Span equivalents (Span 20, Span 40, Span 60 and Span 80).