Polysorbate 20 (commonly known as Tween 20) is a non‑ionic surfactant widely used as an emulsifier, solubilizer, and stabilizer in pharmaceuticals, cosmetics, and food products. It is a clear, viscous liquid derived from sorbitan monolaurate with about 20 ethylene oxide units.

🔬 Chemical Identity

• IUPAC name: Polyoxyethylene (20) sorbitan monolaurate
• CAS number: 9005‑64‑5
• Molecular formula: C₅₈H₁₁₄O₂₆
• Molar mass: ~1226–1228 g/mol
• Appearance: Clear, yellow to yellow‑green viscous liquid
• Density: ~1.1 g/mL
• HLB value: 16.7 (highly hydrophilic, ideal for oil‑in‑water emulsions)

⚙️ Properties & Mechanism

• Surfactant type: Non‑ionic, amphipathic (hydrophilic PEG chain + hydrophobic laurate tail).
• Micelle formation: Above its Critical Micelle Concentration (CMC ~55 μM), it self‑assembles into micelles that encapsulate hydrophobic substances, enabling solubilization in aqueous solutions.
• Viscosity: ~400 mPa·s at 25 °C.
• pH (1% solution): 5.0–7.0.

🧴 Applications

• Pharmaceuticals:
  • Emulsifier and stabilizer in biopharmaceutical formulations.
  • Solubilizing agent for poorly water‑soluble drugs.
  • Used in protein stabilization and cell lysis buffers.
• Biotechnology:
  • Washing agent in immunoassays (Western blot, ELISA).
  • Prevents non‑specific antibody binding.
  • Coating microplates with proteins (e.g., BSA).
• Cosmetics & Personal Care:
  • Emulsifier in creams, lotions, and shampoos.
  • Provides smooth texture and stability.
• Food Industry:
  • Wetting agent in flavored mouth drops and beverages.
  • Approved as food additive E432.

⚠️ Safety & Regulatory Notes

• WHO acceptable daily intake: 0–25 mg/kg body weight for polyoxyethylene sorbitan esters.
• Hazards: Classified as an irritant; handle with care in concentrated form.
• Flash point: ~110 °C.