Patent ID: 8268017

Claim:
A method of suppressing nonspecific color development in a reaction liquid, the method comprising combining a dye mixture comprising a leuco dye and a different dye having an absorption spectrum not influencing a measurement wavelength of the leuco dye and not reacting with hydrogen peroxide, with hydrogen peroxide and peroxidase, wherein the molar ratio of the different dye to the leuco dye is at least 0.8:1 and no greater than 41.7:1, and wherein the mixture of the different dye with the leuco dye suppresses nonspecific color development in the reaction liquid; wherein the leuco dye comprises 10-(carboxymethylaminocarbonyl)-3,7-bis(dimethylamino)phenothiazine sodium or N,N,N′,N′,N″,N″-hexa(3-sulfopropyl)-4,4′,4″-triaminotriphenylmethane.6 sodium; and wherein the different dye is selected from the group consisting of Orange G, Food Red No. 2, Food Red No. 40, Food Red No. 102 and Food Yellow No. 4.