DAB/NiCl2 in PBT-I
DAB (3,3′-diaminobenzidine tetrahydrochloride; Sigma-Aldrich)
Mix 0.03 g of DAB and 0.03 g of NiCl2 in 50 mL of PBT-I. Use within 1 h of preparing and protect from exposure to light. 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.
DAB should be stored desiccated at −20°C. Warm to room temperature before weighing to prepare DAB/NiCl2 in PBT-I.
