"A trustworthy partner for the IVD industry and R&D labs seeking premium immunoassay components."Henrik Christensen, CEO and owner of Kem-En-Tec Diagnostics

OPD, DAB & Fast RED Tablets


OPD Tablets for colorimetric detection of Horseradish Peroxidase activity in ELISAs.

Ortho-Phenylenediamine (OPD) is a water soluble chromogenic substrate that produces a yellow color during the enzymatic degradation of hydrogen peroxide by horseradish peroxidase (HRP) with an absorption maximum at 450 nm. After addition of sulfuric acid a very stable orange end solution is obtained that can be read at 490 nm.

Kem-En-Tec Diagnostics offers:

  • Fizzing OPD tablets: 2 mg tablets are available as fizzing, buffer-containing tablets (#4110-100)


Catalog number Tablet type Tablet size Package size
4110-100 Fizzing OPD tablets 2 mg 100 tablets/vial


DAB, pH 5.0 & pH 7.0

DAB (3,3-diaminobenzidine tetrahydrochloride), is used as a chromogen substrate in immunoblotting & immunohistochemistry.

DAB produces a brown color during the enzymatic degradation of H2O2 by horseradish peroxidase.

1 tablet dissolved in 40 ml of distilled water will give a solution with pH 5.0 +0.1 and a concentration of 0.25 mg/ml DAB buffered with 20 mM phosphate.

Standard package size is 50 tablets/vial.

  • Each tablet contains 10 mg of DAB
  • Dissolves in distilled water in less than 5 minutes



FAST RED is a sensitive chromogenic substrate for use in immuno-histochemistry and immunoblotting procedures.

FAST RED offers an Alkaline Phosphatase immunostaining system which produces a red stain precipitate at the site of the antigens.

Each tablet contains:

  • 2 mg FAST RED chromogen
  • 0.5 mg naphthol phosphate
  • 0.4 mg levamisole (an inhibitor of endogenous enzyme activity).

1 tablet is dissolved in 2 ml of 0.1M TRIS Buffer.

Standard package size is 50 tablets/vial.


  • Stable and robust
  • Negligible batch-to-batch variation
  • Development time: 5-30 minutes


  • 18 -24 months at 2-8° C
  • For long term storage Fast Red tablets should be kept at -20°C


All products are available as OEM components or under our own Kem-En-Tec Diagnostics A/S label.