The TMB High Sensitivity (TMB HS) Substrate solution is an one-step working solution for HRP (horse-radish peroxidase) labeled conjugates. TMB HS substrate solution provides high signal and high sensitivity for ELISA. It is recommended for cytokine ELISA reagent sets. The substrate can be catalyzed with peroxidase to produce a pale blue color which can be read spectrophotometrically at 370 or 620-650 nm. The TMB reaction may be stopped with 2N H₂SO₄ or 1M H₃PO₄ (resulting in a yellow color), and read at 450 nm.