|Molar mass||1227.54 g/mol|
|Appearance||Clear, yellow to yellow-green viscous liquid.|
|Density||1.1 g/mL (approximate)|
|Boiling point||> 100 °C|
|Flash point||110 °C (230 °F; 383 K)|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Polysorbate 20 (common commercial brand names include Alkest TW 20 and Tween 20) is a polysorbate surfactant whose stability and relative non-toxicity allows it to be used as a detergent and emulsifier in a number of domestic, scientific, and pharmacological applications. It is a polyoxyethylene derivative of sorbitan monolaurate, and is distinguished from the other members in the polysorbate range by the length of the polyoxyethylene chain and the fatty acid ester moiety. The commercial product contains a range of chemical species.
In biological techniques and sciences, Polysorbate 20 has a broad range of applications. For example, it is used:
- as a washing agent in immunoassays, such as Western blots and ELISAs. It helps to prevent non-specific antibody binding. In this major application, it is dissolved in Tris-Buffered Saline or Phosphate buffered saline at dilutions of 0.05% to 0.5% v/v. These buffers are used for washes between each immunoreactions, to remove unbound immunologicals, and eventually for incubation solutions of immunoreagents (labeled antibodies) to reduce unspecific background.
- to saturate binding sites on surfaces (i.e., to coat polystyrene microplates, generally combined with proteins such as BSA).
- to stabilize proteins purified protein derivative (PPD) solution used in skin testing for tuberculosis exposure
- as a solubilizing agent of membrane proteins
- for lysing mammalian cells, at a concentration of 0.05% to 0.5% v/v, generally combined with other detergents, salts and additives.
Industrial and domestic applications
Polysorbate 20 is also used by philatelists to remove stamps from envelopes and to remove residues from stamps, without harming the stamp itself.
Polysorbate 20's cmc is 8.04×10-5 M at 21 °C. This corresponds to 0.0987 g/L or approximately 0.01% w/v. Polysorbate 20's hydrophile-lipophile balance (HLB) is: 16.7. HLB number is a measure of how much a surfactant will move into the water and oil phase. A high HLB number like 16.7 indicates that the surfactant will travel into the water phase. 
Tween® and Tween 20® are registered trademarks of Croda Americas
- Ayorinde FO, Gelain SV, Johnson JH Jr, Wan LW. (2000). "Analysis of some commercial polysorbate formulations using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry". Rapid Communications in Mass Spectrometry 14 (22): 2116–2124. doi:10.1002/1097-0231(20001130)14:22<2116::AID-RCM142>3.0.CO;2-1. PMID 11114018.
- Joint FAO/WHO Expert Committee on Food Additives (1974). "Toxicological evaluation of some food additives including anticaking agents, antimicrobials, antioxidants, emulsifiers and thickening agents". WHO Food Additives Series No. 5. World Health Organization.
- Chunhee Kim, You-Lo Hsieh (2001). "Wetting and absorbency of nonionic surfactant solutions on cotton fabrics". Colloids and Surfaces A 187: 385–397. doi:10.1016/S0927-7757(01)00653-7.