Enzyme electrode for phenol

An enzyme electrode is described for quantitative determination of phenol at micromolar concentrations. Immobilized phenol hydroxylase is attached to the surface of a Clark oxygen electrode. The maximum rate of oxygen consumption is linearly dependent on phenol concentration over the 0.5-50 microM range. The electrode can be used for at least 150 assays without an activity loss. Readout is very rapid--within 30 sec of sample addition. The electrode response is independent of pH between pH 6.5 and 9.5. The response increases linearly with temperature in the interval 10-40 degrees C. It is necessary to incubate the enzyme electrode in a buffer containing NADPH for a few minutes before the addition of sample. This is to make the electrode response independent of the diffusion rate of this cosubstrate. This and other diffusional effects on the performance of the phenol electrode are discussed.