SIGMAFAST™ OPD (o-Phenylenediamine dihydrochloride) tablets have been developed for use as a soluble substrate for the detection of peroxidase activity in enzyme immunoassays (EIA). OPD is the EIA substrate of choice as it exhibits high sensitivity. EIA applications utilizing OPD may be read in timed assays or stopped with dilute acid solutions for delayed readings.
SIGMAFAST OPD has been used in saliva- virus-like particles (VLP) binding assay. It has also been used to develop enzyme linked immunosorbent assay (ELISA) plates for the detection of rituximab in rat serum samples.
Each tablet set dissolved in 20 mL deionized water yields a ready-to-use buffered solution containing OPD and urea hydrogen peroxide.
One OPD tablet and one urea hydrogen peroxide/buffer tablet, dissolved in 20 ml of water, provides 20 ml of ready-to-use substrate. When the tablet is dissolved in this manner, the final concentrations will be 0.4 mg/ml OPD, 0.4 mg/ml urea hydrogen peroxide, and 0.05 M phosphate-citrate, pH 5.0. Tablets are individually packaged in foil packets.