TMB Substrate for ELISA is a peroxidase substrate containing 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide in an aqueous buffer formulation. This product is supplied as a one component ready-to-use reagent. Intact/unreacted substrate is clear colorless to slightly yellowish in appearance. Reaction with peroxidase results in converting substrate into soluble blue (~ 650 nm) product which after stopping with strong acid further turns to super-oxidized soluble yellow product. Yellow product can be measured at 450 nm (measuring at 450 nm vs. 620-650 nm reference wavelength will additionally improve readout pattern in ELISA.