Patent ID: 7550273

Claim:
A colorimetric method comprising: transferring an electron from an analyte to a mediator by using an oxidoreductase; transferring the electron from the mediator to a coloring reagent that produces color by reduction; and performing qualitative or quantitative analysis of the analyte by measuring color produced in the coloring reagent; wherein the coloring reagent is a tetrazolium salt, the mediator is a transition metal complex that receives an electron from the analyte and transfers the received electron to the coloring reagent, the transition metal complex is at least one selected from the group consisting of a copper complex, an iron complex, an osmium complex, and a ruthenium complex, and the iron complex comprises at least one ligand selected from the group consisting of ammonia, a bipyridyl compound, an imidazole compound, a phenanthroline compound, amino acid, a triazine compound, a biquinoline compound, a pyridylazo compound, a nitroso compound, an oxine compound, a benzothiazole compound, an acetylacetone compound, an anthraquinone compound, a xanthene compound, oxalic acid, and a derivative of each of the compounds.