Peroxidase-Based Amperometric Sensor for the Determination of Total Phenols Using Two-Stage Peroxidase Reactions

A new method of measuring the total phenolic compounds in wine and tea is proposed. The method is based on the fact that the decreased amount of H₂O₂ caused by the action of peroxidase is proportional to the oxidized amount of phenolic compounds in the solution. Decrease in H₂O₂ was sensitively detected with a semipermeable-membrane-covered, horseradish-peroxidase-entrapped, and ferrocene-embedded carbon paste electrode. This electrode allows the detection of (+)-catechin down to 0.3 µM and the response is linear up to 15 µM. The content of total phenolic compounds in wine and tea samples determined by the present method agrees well with results obtained by the Folin-Ciocalteu method. Advantages of the proposed method over the Folin-Ciocalteu method include shorter detection time, smaller sample volume, one order of magnitude higher sensitivity, lesser degree of interference from coexisting SO₂ and glucose, and applicability to colored, turbid, or colloidal samples. The method is not influenced by the oxygen level in samples. Samples require pretreatment if ascorbic acid is present.