Merck, P3804-50TAB, o-Phenylenediamine dihydrochloride

General description
o-Phenylenediamine dihydrochloride (OPD) is a chromogenic substrate that can be used in enzyme-linked immunosorbent assay (ELISA) procedures as it utilizes horseradish peroxidase conjugates. The substrate produces a soluble end product that is orange-brown and can be read spectrophotometrically at 450 nm. The OPD reaction may be stopped with 3N HCl or 3M H2SO4 and read at 492 nm.
Application
o-Phenylenediamine dihydrochloride has been used:
as a chromogenic substrate in indirect enzyme-linked immunosorbent assay (ELISA) to detect immunoglobin G (IgG) antibodies against certain recombinant antigens/proteins
as a streptavidin-horseradish peroxidase (HRP) substrate sandwich ELISA to analyze human interleukin (IL)-17A, IL-23, and IP-10
as a substrate in ELISA for determination of IgG-class antibodies to Mycobacterium bovis in serum

Packaging
16 mg total tablet weight
Preparation Note
Dissolve one tablet in 0.05 M phosphate-citrate buffer, pH 5.0, to the desired concentration (typically an OPD concentration of 0.4 mg/ml is used). Add 40 μl of fresh 30% hydrogen peroxide per 100 ml of substrate buffer solution, immediately prior to use.