An amperometric biosensor for the determination of hydroquinone and other polyphenolic antioxidants is presented, based on a carbon paste electrode on which tyrosinase is immobilized in a Nafion film.In a 0.1 M phosphate buffer (pH 7.0 and 25 1 C), the antioxidant capacity can be expressed as theconcentration equivalent of p-hydroquinone (HQ), according to an amperometric response ofpolyphenolic antioxidants with the carbon paste sensor at .24 V vs. Ag/AgCl/3 M KCl. In the range-1 of low HQ concentrations (up to 120 mol L ), the corresponding calibration curve follows the-1 equation I [A] = 0.0426 0.0113 c(HQ) [mol L ] with a correlation coefficient R = 0.999. The-1 limit of detection (LOD for S/N = 3) was estimated as 1.6 mol L , the repeatability was 1.2 % RSD(c = 90 M, n = 5 measurements). The biosensor can be applied to determine the phenolic antioxidantcapacity in plants and food samples in the absence of higher concentrations of ascorbic acid.
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