When a sample is mixed with the Choromogen Reagent, the alpha-formof glucose in the sample is converted to beta-form by mutarotase. beta-DGlucoseis oxidized and yields hydrogen peroxide by glucose oxidase(GOD). In the presence of peroxidase (POD), the formed hydrogen peroxideyields a red pigment by quantitative oxidation condensation withphenol and 4-aminoantipyrine. The glucose concentration is obtained bymeasuring absorbance of the red pigment.