A Sensitive Enzyme Electrode for Phenol Monitoring

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Abstract
Tyrosinase (EC.1.14.18.1) was immobilized onto graphite electrodes, which had been modified with tetracyanoquinodimethane (TCNQ). The response time, 12 or 35 s, was dependent on the enzyme immobilization technique used. The electrodes showed a linear calibration function up to 25 or 65 μM phenol, and a sensitivity of 0.36 or 2.2 A/M was achieved which was also dependent on the enzyme immobilization technique used. The detection limit for phenol was 0.23 μM. The electrodes acted from potentials of -200 to +180 mV (vs. a saturated Ag/AgCl electrode). The electrode signal was independent of pH within the pH range 4.5 – 6.0. The enzyme electrode responded to phenol (100 %), p-cresol (93 %) and catechol (330 %), but not to o-cresol and L-tyrosine. The electrodes showed a stability for more than one week. The electrodes can be utilized for the sensitive assay of phenol in water.