Thermo Scientific Pierce OPD is a water-soluble substrate for horseradish peroxidase (HRP) that produces a yellow-orange product detectable at 492nm by ELISA plate readers.
OPD yields a water soluble yellow-orange product when reacted with peroxidase with an absorbance maximum of 492. OPD can easily be dissolved in a substrate buffer such as Stable Peroxide Substrate Buffer (Part No. 34062).
Assay development and ELISA technical guide
ELISA substrate selection guide