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Item # Unit Size
1 g

For Research Use Only Products

Chemical Name: 5,5'-Dithiobis(2-nitrobenzoic acid)
CAS: 69-78-3

Appearance: pale yellow crystalline powder
Molar absorptivity: ≥12,000 at 305 nm
MW: 396.35, C14H8N2O8S2

Storage Condition: ambient temperature
Shipping Condition: ambient temperature

Product Description
DTNB is known as Ellman’s reagent. It is used for the colorimetric determination of thiol groups in biological samples. It is fairly soluble in water. Colorless DTNB is converted to yellow 5-Mercapto-2- nitrobenzoic acid in the presence of thiol compounds (Fig. 1). As 5-Mercapto-2-nitrobenzoic acid has an absorption maximum at 412 nm, the absorption spectrum of DTNB does not interfere with thiol detection (Fig. 2).

Fig. 1 DTNB reaction with thiol compound

Fig. 2 Absorption spectra of DTNB and reduced DTNB
1) D. R. Grassetti, et al., Determination of Sulfhydryl Groups with 2, 2 E or 4, 4 EDithiodipyridine. Arch Biochem Biophys. 1967;119:41-49.
2) R. E. Humphrey, et al., Spectrophotometric Determination of Sulfite with 4, 4 EDithiodipyridine and 5, 5 EDithiobis-(2-nitrobenzoic acid). Anal Chem. 1970;42:698-702.
3) R. E. Humphrey, et al., Spectrophotometric Determination of Cyanide with Organic Disulphides. Talanta. 1971;18:491-497.
4) T. Uete, et al., Spectrophotometric Micromethod for Measuring Cholinesterase Activity in Serum or Plasma. Clin Chem. 1972;18:454-458.