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A9941 Sigma-Aldrich

2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt

tablet, 10 mg substrate per tablet

Synonym: AzBTS-(NH4)2, Diammonium 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate)

  • CAS Number 30931-67-0

  • Empirical Formula (Hill Notation) C18H24N6O6S4

  • Molecular Weight 548.68

  •  Beilstein/REAXYS Number 7329461

  •  EC Number 250-396-6

  •  MDL number MFCD00010404

  •  PubChem Substance ID 24891410



Related Categories Alphabetical Listing, Biochemicals and Reagents, Colorimetric, Core Bioreagents, Detection,
form   tablet
solubility   deionized water: 100 mL
storage temp.   room temp
SMILES string   [NH4+].[NH4+].CCN1C(\Sc2cc(ccc12)S([O-])(=O)=O)=N\N=C3/Sc4cc(ccc4N3CC)S([O-])(=O)=O
InChI   1S/C18H18N4O6S4.2H3N/c1-3-21-13-7-5-11(31(23,24)25)9-15(13)29-17(21)19-20-18-22(4-2)14-8-6-12(32(26,27)28)10-16(14)30-18;;/h5-10H,3-4H2,1-2H3,(H,23,24,25)(H,26,27,28);2*1H3/b19-17-,20-18-;;


General description

ABTS mainly used in ELISA (enzyme-linked immunosorbent assay) procedures.
ABTS, 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), is a chromogenic substrate used:
• For a reaction with laccase or bilirubin oxidase
• For a reaction with peroxidase enzymes: (like HRP for example). ABTS in combination with hydrogen peroxide
A peroxidase reaction of ABTS in the presence of hydrogen peroxide produces a green soluble end product which can be read spectrophotometrically at 405nm. The reaction may be stopped with 1% sodium dodecyl sulfate (SDS).
ABTS, 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt is light sensitive, and water soluble chemical compound


• 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, ABTS, has been used as a substrate in ELISA (enzyme-linked immunosorbent assay).†
• ABTS is also used to measure glucose concentrations in different solutions including blood serum.
• The food industry uses ABTS to measure the antioxidant capacities within different foods.
• Since it is less readily oxidized than TMB and OPD substrates, ABTS is less sensitive for ELISA applications. Thus ABTS has some advantageous over TMB and OPD in cases of large background results
• It is recommended for ELISA (microwell) procedures, not recommended for membrane applications.

2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) is a peroxidase substrate suitable for use in ELISA procedures. This substrate produces a soluble end product that is green in color and can be read spectrophotometrically at 405 nm. The reaction may be stopped with 1% sodium dodecyl sulfate (SDS). Recommended for ELISA (microwell) procedures, not recommended for membrane applications.


Dissolve 1 tablet in 100 ml of 0.05 M phosphate-citrate buffer, pH 5.0 (Tablets available as Sigma Product No. P4809). Add 25 μl of fresh 30% hydrogen peroxide

Safety & Documentation

Safety Information

Personal Protective Equipment 
NONH for all modes of transport
WGK Germany 
Flash Point(F) 
Not applicable
Flash Point(C) 
Not applicable


Certificate of Analysis (COA)

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Certificate of Origin (COO)

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Protocols & Articles


Colorimetric Alkaline Phosphatase and Peroxidase Substrate Detection Systems

Nitroblue Tetrazolium (NBT) is used with the alkaline phosphatase substrate 5-Bromo- 4-Chloro-3-Indolyl Phosphate (BCIP) in western blotting and immunohistological staining procedures. These substrat...
BioFiles 2008, 3.4, 6.
Keywords: Enzyme-linked immunosorbent assay, Immunohistochemistry, Western blot


Enzymatic Assay of Alcohol Oxidase (EC

The continuous spectrophotometric rate determination (A405, Light path = 1 cm) is based on the following reactions:
Keywords: Extinction coefficient

Enzymatic Assay of Peroxidase (EC 2,2'-Azino-bis(3-Ethylbenzthiazoline-6-Sulfonic Acid) as a Substrate

Replaces SPABTS02. Procedure updated to conform to current QUMAS formatting guidelines. Refer to CR SOP-DEK-ENZ42.
Keywords: Extinction coefficient

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