Glucose oxidase (GOD) converts glucose to gluconic acid. Hydrogen Peroxide formed in this reaction, in presence of Peroxidase POD). Oxidatively couples with 4-aminoantipyrine and phenol to produce red quinonimine dye. This dye has absorbance maximum at 505 nm. (500-550 nm),. The intensity of the color complex is directly proportional to the concentration of glucose in a specimen.