3,3',5,5' - Tetramethylbenzidine as an Ames test negative chromogen for horse-radish peroxidase in enzyme-immunoassay

The use of 3,3',5,5' - tetramethylbenzidine as non-mutagenic chromogen for the end point determination in enzyme-immunoassay (EIA) is described. In sandwich EIAs for HCG and HBsAg and in a competitive EIA for testosterone, the colour yield with TMB was superior to that obtained with o-phenylene diamine (OPD), which was by far the best chromogen for horse-radish peroxidase until now. This led to an improvement of sensitivity and precision of the assays and makes EIA even more competitive with other types of immunoassays.