Stop Solution for TMB Substrates (STOPT) is a ready-to-use liquid acidic stop solution suitable for use with our TMB substrates. TMB substrates react with peroxidase, yielding a soluble blue reaction product. When the TMB-peroxidase reaction is stopped using Stop Solution for TMB Substrates, the chromogen changes from blue to yellow. This product is suitable for all endpoint ELISAs using a TMB substrate for color development.