Dichlorofluorescein (DCF) is an organic dye of the fluorescein family, being substituted at the 2 and 7 positions by chloride.
It is used as an indicator for argentometry by Fajans method.
When used as an indicator, upon reaching the equivalence point of a titration reaction the color shifts from colorless towards a faint pink.
It is also used in the cellular antioxidant activity (CAA) assay. Dichlorofluorescin (DCFH) is a probe that is trapped within cells and is easily oxidized to fluorescent dichlorofluorescein (DCF). The method measures the ability of compounds to prevent the formation of DCF by 2,2'-Azobis(2-amidinopropane) dihydrochloride (ABAP)-generated peroxyl radicals in human hepatocarcinoma HepG2 cells. By itself, dichlorofluorescin (DCFH) also quantifies intracellular hydrogen peroxide as well as cellular oxidative stress.