ELECTROCHEMICAL STUDY OF POLYPHENOLS WITH AMPEROMETRIC TYROSINASE BASED BIOSENSORS

摘要

This paper describes the preparation of a novel biosensor based on tyrosinase immobilized onto single wall carbon nanotubes screen-printed electrodes modified with iron(II) phthalocyanine, and its application for measuring the polyphenols compounds in vegetables samples. The tyrosinase preserves its biocatalytic activity within the carbonaceous matrix. A noticeably defined reduction peak proportional to the catechin concentration was observed in cyclic voltammetry, which correspond to the reduction of enzymatically produced quinone at the electrode surface. Different analytical parameters influencing the biosensor performance have been studied such as applied potential and pH. In the optimal conditions, the biosensor presented a linear response range for catechin from 5 to 250 M, applying a potential of 0.15V versus Ag/AgCl, with a sensitivity of 0.094. A M' anda detection limit of 0.89 M. The biosensor was used in the polyphenols determination in green tea extracts and the results were compared with the Folin-Ciocalteau method and the biosensor demonstrated suitability to the quantification of the total polyphenols.