DAB-NiCl2
3,3′-diaminobenzidine tetrahydrochloride (DAB)
Mix 0.03 g of DAB and 0.03 g of NiCl2 in 50 mL of PBTX. Keep the solution protected from light, and use it within 1 h of preparing. (The DAB should be stored desiccated at −20°C, and warmed to room temperature before weighing.)
During immunohistochemistry procedures, the nickel enhances the sensitivity of the color reaction and produces a slate-gray to purple precipitate. If necessary, vary the amount of nickel to alter the intensity of the color. Cobalt can be substituted for nickel.
