Ellman’s Reagent

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SKU: BC87-XX Category:
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5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB)
Ellman’s reagent is a versatile, water-soluble compound for quantifying free sulfhydryl groups in solution. It reacts with a free sulfhydryl group to yield a mixed disulfide and 2-nitro-5-thiobenzoic acid (NTB), a measurable yellow colored product at 412nm.
Ellman’s reagent is very useful as a free sulfhydryl assay reagent due to its high specificity for -SH groups at neutral pH, high molar extinction coefficient and short reaction time.
Synonyms: DTNB; 5,5′-Dithio-bis(2-nitrobenzoic acid); Ellman’s Reagent; 3-Carboxy-4-nitrophenyl disulfide
PubChem Chemical ID: 6254
Yellow crystalline powder that is used for the colorimetric determination of thiol groups in biological samples. DTNB is fairly soluble in water.
Store at 2-8°C and protect from light and humidity.



  • Highly stable and water soluble
  • Quick and simple assay
  • CAS#: 69-78-3
  • Molecular Formula:  C14H8N2O8S2
  • Molecular Weight: 396.36 g/mol 



  • Quantification of free sulfhydryl residues



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