[Horseradish peroxidase: reagent for stopping the catalytic conversion of the substrates H2O2 and 2,2'-azino-di(3-ethyl-benzathiazoline-sulphonic acid-(6)) (ABTS)].

Catalytic conversion of H2O2 and 2,2'-azino-di(3-ethyl-benzthiazoline-sulphonic acid-(6)) (ABTS) by peroxidase is stopped immediately and completely by the addition of a secondary alkyl sulphate (Teepol-610) or sodium dodecyl hydrogensulphate. The resulting colour intensity of the oxidized ABTS+ is thereby stabilized and can be determined photometrically within 60 min. These stop reagents have special practical importance for the enzyme-(peroxidase)-immunological determination by the ELISA technique; but the activity of the indicator enzyme must be measured by the two point method, owing to the heterogeneity of the test system and the slow reaction rate.