BCIP (5-Bromo-4-chloro-3-indoxyl phosphate, disodium salt) is the most widely used chromogenic phosphatase substrate, which forms a dark blue (λmax 615 nm) precipitate on enzymatic hydrolysis. It is often used with the oxidant NBT (nitro blue tetrazolium chloride), which facilitates the precipitation. White solid soluble in water Store at 4°C and protect from light C8H4BrClNNa2O4P MW: 370.5 [102185-33-1]