Standardization of serum ceruloplasmin concentrations in international enzyme units with o-dianisidine dihydrochloride as substrate.

We describe a method for calculating the absorptivity (in terms of substrate consumed) of the colored solution obtained when o -dianisidine dihydrochloride is oxidized by ceruloplasmin. By oxidizing o -dianisidine dihydrochloride with known amounts of hydrogen peroxide we could determine that the molar reacting ratio of o -dianisidine to hydrogen peroxide is 2:1. So calculated, absorptivity is 9.6 ml µmol -1 cm -1 , the figure used to estimate ceruloplasmin oxidase activity in terms of International Units.

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