Amperometric biosensor for polyphenol based on horseradish peroxidase immobilized on gold electrodes

Horseradish peroxidase (HRP) is covalently immobilized on a self-assembled monolayer of mercaptopropionic acid on vapor-deposited gold electrode. The electrode allows the polyphenol detection down to 2 muM with a linear relat ionship up to 25 muM. The reduction current of oxidized polyphenols, formed during the enzymatic oxidation of polyphenolic compounds in the presence o f H2O2, is proportional to their concentration. The sensitivity of the dete ction of various polyphenols by the present method depends on both the elec tron-donating properties of polyphenols and the electron-accepting properti es of oxidized polyphenols. The total amounts of polyphenols in several win e and tea samples detected by the present method are well correlated with t hose determined by the Folin-Ciocalteu method. In addition, this method has several advantages over the Folin-Ciocalteu method: shorter detection time , smaller sample volume, and more torelant to interference substances.