CATECHOL SENSOR-BASED ON ASCORBATE OXIDASE IMMOBILIZED POLYMER-MODIFIED GRAPHITE ELECTRODE

A selectivity and sensitivity enhanced catechol sensor based on a poly mer-modified graphite electrode was fabricated by immobilizing ascorba te oxidase (AO) into a poly(N-vinyl pyrrolidone) (PNVP) membrane. AO w as immobilized between two PNVP membrane layers as a sandwiched struct ure by cross-linking PNVP with gamma radiation. The sensor responses t o catechol and ascorbic acid were evaluated by cyclic voltammetry. The sensor showed a selective response to catechol even in the presence o f ascorbic acid, which was due to blocking ascorbic acid access to the electrode surface by the enzymatic activity of AO immobilized in the polymer membrane. Compared to a bare electrode without modification wi th the PNVP membrane, an enhanced response of the sensor to catechol w as observed, which was due to preconcentration of catechol into the PN VP membrane. The enzymatic activity of AO immobilized on the sensor su rface did not change for at least four days.