Tween (Polysorbates)

Tween (Polysorbates)

(Non-ionic Surfactant)

General Description:

Tween, also known as Polysorbates, is a non-ionic surfactant with a characteristic odor, a warm and slightly bitter taste. It is a series of partial fatty acid esters of polyoxyethylene sorbitan. Widely used as emulsifiers and solubilizers for oily substances, Polysorbates are generally regarded as non-toxic and non-irritating materials. According to WHO evaluations, a daily intake of up to 25 mg/kg of body weight is considered safe.

Names:

• Generic Name: Polysorbates (Polyoxyethylene sorbitan fatty acid esters)

• English Name: Polyoxyethylene Sorbitan Fatty Acid Esters

• Other Names: Tween, Polysorbates, Polysorbatum

Classification:

• Emulsifier

• Non-ionic Surfactant

• Solubilizer

• Wetting Agent

• Dispersant / Suspending Agent

Properties:

• Appearance: Viscous liquid ranging from pale yellow to amber (varies depending on molecular weight)

• Odor & Taste: Characteristic odor, warm and slightly bitter

• pH: ~6–8 (5% w/v aqueous solution)

• Flash Point: 149°C

• Stability: Stable in presence of electrolytes, weak acids, and weak alkalis. Gradually undergoes saponification with strong acids or bases.

• Other Characteristics:

  • Hygroscopic

  • May form peroxides over prolonged storage

  • Oxidizable acid groups

  • Should be dried if necessary

Mechanism:

Due to a high content of hydrophilic polyoxyethylene groups, Polysorbates are strongly hydrophilic and function as non-ionic surfactants.

Applications:

1. Biological Research:

   • Used to emulsify proteins without disrupting their structure

   • Tween (e.g., Tween-20) and Triton X-100 are non-ionic detergents that maintain protein integrity, unlike ionic detergents such as SDS that denature proteins.

2. Blocking Agent in Assays:

   • Used in biological assays like Western blotting to block non-specific binding sites.

   • Does not replace membrane-bound target proteins or interfere with antibodies/reagents.

   • Enhances antigen specificity (refolding effect).

   • Common blocking agents: BSA, non-fat milk, casein, gelatin, Tween-20 (0.05–0.1% solution).

3. Emulsifier in O/W Formulations:

   • Helps disperse substances uniformly in oil-in-water emulsions.

   • Common in pesticides, food products, and cosmetics.

   • Enhances emulsion stability when combined with other emulsifiers like sodium lauryl sulfate or Span-type surfactants.

   • Used to emulsify essential oils into water for full functional performance.

   • Tween-20 is milder, while Tween-80 offers stronger emulsification.

4. Pharmaceutical Use:

   • Acts as a solubilizer for certain drugs.

   • Has hemolytic properties (least with Tween-80).

   • Aqueous solutions may become cloudy when heated and clear again when cooled, without quality loss.

   • May interfere with the action of preservatives in solutions.