Principle
Cholesterol esters in the sample are hydrolyzed by cholesterol esterase to release free cholesterol. The free cholesterol is oxidized by cholesterol oxidase to release hydrogen peroxide. Phenol + 4-AAP + hydrogen peroxide, in the presence of peroxidase produces a quinoneimine dye that is measured at 500nm. The absorbance at 500nm is proportional to the concentration of cholesterol in the sample.