A new sensitive colorimetric assay for peroxidase using 3,3′-diaminobenzidine as hydrogen donor

A new simple colorimetric assay for measurement of peroxidase activity using 3,3′-diaminobenzidine tetrahydrochloride as hydrogen donor is described. The DAB is stable under the usual assay conditions, and its rate of auto-oxidation is negligible. Under optimal conditions, a linear relationship is found between peroxidase concentration and the rate of oxidation of 3,3′-diaminobenzidine tetrahydrochloride (ΔA 405nm /min). Using horseradish peroxidase, the DAB method appears more sensitive than the o -dianisidine and the guaiacol assays for peroxidase. This method can also be used for measurement of peroxidase activity in tissue fractions.