TMB (3,3',5,5'-TETRAMETHYL BENZIDINE) DIHYDROCHLORIDE Grade:HIGH PURITY GRADE CAS Number: 64285-73-0Synonym(s): None Molecular Weight: 313.30Molecular Formula: C16H20N2 • 2HCl Storage Condition: COLD CodeSizePriceQuantity 0759-1G 0759-5G TMB is a sensitive substrate for the detection of horseradish peroxidase (HRP) activity in solution-based assays. In the presence of HRP and hydrogen peroxide, a blue oxidation product with absorbance maxima at 370 nm and 652 nm is produced. The addition of acid stops the reaction and changes the end-product to yellow, with an absorbance maximum at 450 nm.