Oxygen Dependence in a Dual-Phase Electrochemical Biosensing System
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Oxygen dependence of a tyrosinase-based electrochemical biosensor for determination of phenol in aqueous and organic media was systematically investigated. The result demonstrated that the enzymatic coupling reaction rate of tyrosinase (deoxy form) and O2 to regenerate tyrosinase (oxy form) is a kinetically fast reaction, and the significant change of O2 concentration in aqueous solution did not affect the coupling reaction. The further increase of O2 concentration did not increase the overall oxidation reaction rate of the substrate at low substrate concentration (e.g.,<10 mM phenol) when O2 concentration was greater than 8.9 ppm. The oxygen dependence was observed in the case of high substrate concentration due to insufficient amount of O2 available for the regeneration of tyrosinase. In other words, the upper linear range is oxygen dependent for tyrosinase biosensors. The phenol biosensors employing microelectrodes had wider upper linear ranges than macroelectrodes in both aqueous and organic phase, which can be explained by the oxygen dependence.
Copyright 2005 John Wiley & Sons, Ltd. Self-archiving of the author-manuscript version is not yet supported by this publisher. Please refer to the journal link for access to the definitive, published version or contact the author for more information.