Widely used to detect horseradish peroxidase activity in ELISA and solution assays. Absorbs at 492 nm. Each tablet contains 15 mg of OPD. Soluble. Reaction Condition: 40 µg/ml 50 mM Sodium Citrate, 150 mM Sodium Phosphate and 0.01% H2O2, pH 6.0. Stop with 1 M H2SO4.