- CAS
- 9005-64-5
- Grade
- USP
- PBST
- Often 0.05–0.1% (v/v)
Tween 20 lowers non-specific binding in a wash. It does not replace the protein blocker. Catch-Chem quotes the USP raw material.
What it is
Tween 20 (polysorbate 20, polyoxyethylene (20) sorbitan monolaurate) is a mild non-ionic surfactant. Its high HLB (about 16.7) and low critical micelle concentration let it reduce weak, non-specific hydrophobic binding without disrupting most antibody-antigen interactions.
Where it is used
- Wash buffers for ELISA and Western blot: PBST or TBST, typically 0.05–0.1% (v/v).
- Additive in blocking buffers and antibody diluents, usually at similar levels alongside BSA or casein.
- Stabilizer against surface adsorption in enzyme and protein formulations, often 0.01–0.1%.
- Mild permeabilization in some immunostaining protocols.
Handling tips
- The liquid is viscous. Prepare a 10% stock by weight for accurate dilution.
- Polysorbates form peroxides with age, heat and light. Store sealed, cool and dark, and date opened bottles.
- Solutions foam easily; mix gently.
What to specify when ordering
- Grade: USP, or a low-peroxide grade for sensitive assays.
- Neat liquid or a pre-diluted solution.
- Pack size. See why washes use Tween 20.
Properties and storage
- Formula
- —
- Molecular weight
- about 1228 (average)
- Appearance
- Pale yellow to amber viscous liquid
- Solubility
- Miscible with water
- Storage
- Room temperature, sealed, dark
- Typical packs
- 100 mL, 500 mL, 1 L, 5 L
Typical literature values. The batch COA / SDS governs.
Before you inquire
Tween 20 or Tween 80?
Washes usually use Tween 20, which has a C12 laurate chain. Tween 80 has a C18 oleate chain and is more often used as an emulsifier or formulation excipient.
Can Tween 20 replace BSA or casein?
No. It reduces weak background binding during washes but does not coat the surface the way a protein blocker does.
Is more Tween 20 better?
Not usually. Above about 0.1% it can strip weakly bound antigen or antibody from the plate or membrane.
Tween 20 or Triton X-100?
Triton X-100 is a stronger detergent used for lysis and permeabilization. Tween 20 is the gentler wash additive.
Pack sizes and catalogue numbers
Prices on request; lead time confirmed on the quotation.
Request a quote for Tween 20, USP
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Send an inquiryFor research or industrial use only. Not for human or animal diagnosis or treatment, and not for drug or food use. Grade, pack size and lead time follow the supplier batch COA / SDS. Figures on this site are general industry references, not a factory specification.