This solution contains 3,3’,5,5’-tetramethylbenzidine which is a substrate for horseradish peroxidase in our ELISA kits. The TMB substrate solution is ready-to-use and in concert with SPP conjugate (CT357), the substrate produces a soluble blue end product that can be read spectrophotometrically at 370 or 655 nm. The reaction can be stopped by adding 0.18M sulfuric acid (resulting in a yellow solution which can be read at 450 nm). Upon ordering, you will receive TMB substrate solution for 240 ELISA determinations.