3,3,5,5-Tetramethylbenzidine (TMB) chromogenic peroxidase sensitive dye. TMB is a noncarcinogenic substitute (Ames test negative) for benzidine suitable as peroxidase substrate for use in ELISA procedures. The substrate produces a soluble end product that is pale blue in color and can be read spectrophotometrically at 370 or 620-650nm. The TMB reaction may be stopped with 2M H2SO4 (resulting in a yellow color), and read at 450nm. A sensitive and specific reagent for the detection of blood, assay of haemoglobin and assay of horseradish peroxidase (HRP). - Chemical. CAS: 54827-17-7. Formula: C16H20N2. MW: 240.34. 3,3,5,5-Tetramethylbenzidine (TMB) chromogenic peroxidase sensitive dye. TMB is a noncarcinogenic substitute (Ames test negative) for benzidine suitable as peroxidase substrate for use in ELISA procedures. The substrate produces a soluble end product that is pale blue in color and can be read spectrophotometrically at 370 or 620-650nm. The TMB reaction may be stopped with 2M H2SO4 (resulting in a yellow color), and read at 450nm. A sensitive and specific reagent for the detection of blood, assay of haemoglobin and assay of horseradish peroxidase (HRP).