DAB is commonly used for detection of horseradish peroxidase in membrane-bound and in Situapplications. Insoluble end product is resistant to alcohol and fading, making it ideal for immunohistochemistry. Insoluble. Reaction Condition: 6 mg in 10 ml of 50 mM Tris, 0.1 M NaCl, pH 7.6 and 0.01% H2O2. The presence of Nickel or Cobalt increases sensitivity.