OPD EASY-tablets

white to light pink powder

o-Phenylenediamine dihydrochloride has been used as a substrate for horseradish-peroxidase-conjugated secondary antibody in enzyme-linked immunosorbent assay (ELISA).

o-Phenylenediamine is a peroxidase substrate suitable for use in ELISA procedures. The substrate produces a soluble end product that is orange-brown in color and can be read spectrophotometrically at 450 nm. The OPD reaction may be stopped with 3 N HCl or 3 M H₂SO₄ and read at 492 nm.

Brownish-yellow crystals. Slightly soluble in water. Used in the manufacture of dye.

Slightly soluble in water.

Acidic organic/inorganic salts, such as OPD EASY-tablets, are generally soluble in water. The resulting solutions contain moderate to high concentrations of hydrogen ions and have pH's of less than 7.0. They react as acids to neutralize bases. These neutralizations generate heat, but less or far less than is generated by neutralization of inorganic acids, inorganic oxoacids, and carboxylic acid. They usually do not react as either oxidizing agents or reducing agents but such behavior is not impossible. Many of these compounds catalyze organic reactions.

Crystallise the salt from dilute HCl (60mL conc HCl, 40mL water, with 2g stannous chloride), after treatment of the hot solution with charcoal by adding an equal volume of conc HCl and cooling in an ice-salt mixture. The crystals are washed with a small amount of conc HCl and dried in a vacuum desiccator over NaOH. [Beilstein 13 IV 38.]