Patent ID: 8574896

Claim:
A reagent useful for a colorimetric method comprising: transferring an electron from an analyte to a coloring reagent that produces color by reduction via a mediator by using an oxidoreductase; and performing qualitative or quantitative analysis of the analyte by measuring color produced in the coloring reagent, and; the reagent comprising: an oxidoreductase; a mediator; and a coloring reagent for producing color by reduction, wherein the mediator is at least one selected from the group consisting of a copper complex, an iron complex, an osmium complex, and a ruthenium complex, wherein iron complex has a at least one ligand selected from the group consisting of ammonia, an imidazole compound, a phenanthroline compound, a triazine compound, a biquinoline compound, a pyridylazo compound, a nitroso compound, an oxine compound, a benzothiazole compound, and a derivative of each of the compounds, or the iron complex is selected from the group consisting of Fe(4,4′-dimethyl-2,2′-bipyridyl) 3 , Fe(4,4′-diphenyl-2,2′-bipyridyl) 3 , Fe(4,4′-diamino-2,2′-bipyridyl) 3 , Fe(4,4′-dihydroxy-2,2′-bipyridyl) 3 , Fe(4,4′-dicarboxy-2,2′-bipyridyl) 3 , Fe(4,4′-dibromo-2,2′-bipyridyl) 3 , Fe(5,5′-dimethyl-2,2′-bipyridyl) 3 , Fe(5,5′-diphenyl-2,2′-bipyridyl) 3 , Fe(5,5′-diamino-2,2′-bipyridyl) 3 , Fe(5 5′-dihydroxy-2,2′-bipyridyl) 3 , Fe(5,5′-dicarboxy-2,2′-bipyridyl) 3 , and Fe(5,5′-dibromo-2,2′-bipyridyl) 3 , and wherein the copper complex, the osmium complex, and the ruthenium complex have at least one ligand selected from the group consisting of ammonia, a bipyridyl compound, an imidazole compound, a phenanthroline compound, a triazine compound, a biquinoline compound, a pyridylazo compound, a nitroso compound, an oxine compound, a benzothiazole compound, and a derivative of each of the compounds.