Tween 20 (polysorbate 20, CAS 9005-64-5) is a non-ionic surfactant. ELISA wash buffers often contain 0.05–0.1% (v/v) in PBS, called PBST, to remove unbound antibody and lower background. Blocking is still a protein step, typically BSA or casein. Catch-Chem quotes Tween 20 as a USP raw material; the 0.05–0.1% range is common laboratory practice.
See Tween 20, BSA and ELISA / IVD. TMB is the HRP chromogen, read at 450 nm after an acid stop.
Related questions
Is 0.05% a fixed specification?
No. It is a common lab range; follow your protocol.
How do I make PBST?
Add Tween 20 USP to PBS at about 0.05–0.1%.
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