“…In addition to the type and activity of the peroxidase, the lower detection limit of the enzymatic reaction is influenced by the chromogenic or fluorogenic substrate used, as the properties of the detected reaction product play a crucial role. A variety of organic compounds are used as chromogenic substrates, for example, aromatic amines like o-phenylenediamine (OPD), [1] 3,3'-5,5'-tetramethylbenzidine (TMB), [2] and also 2,2'-azinobis(3-ethylbenzothiazolin)-6-sulfonate as the diammonium salt (ABTS) [3] . In case of the more sensitive fluorogenic methods the p-hydroxyphenylcarboxylic acids, especially phydroxyphenylacetic acid (pHPA), have found widespread application.…”