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. It is often required to quantitate Polysorbate (Polysorbate/Tween 20, Polysorbate/Tween 40, Polysorbate 60/Tween 60 and Polysorbate 80) by HPLC in various formulations. Polysorbates exist in form of oligomers.