3,3′,5,5′-Tetramethylbenzidine may be used as a substrate for the analysis of diclofenac in water samples and dextromethorphan and its major metabolite dextrorphan in urine samples using enzyme-linked immunosorbent assay (ELISA) and gas chromatography coupled to mass spectrometry (GC-MS).
3,3′,5,5′-Tetramethylbenzidine (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 620-650 nm. The TMB reaction may be stopped with 2 M H2SO4 (resulting in a yellow color), and read at 450 nm. A sensitive and specific reagent for the detection of blood, assay of hemoglobin, assay of peroxidases.