AMPEROMETRIC BIOSENSOR FOR THE DETERMINATION OF PHENOLIC-COMPOUNDS USING A TYROSINASE GRAPHITE ELECTRODE IN A FLOW-INJECTION SYSTEM

Selective and sensitive devices for the monitoring of phenol and phenolic compounds are required in clinical and environmental analysis. This paper describes a biosensor for the analysis of phenolic compounds in a flow injection system. The enzyme electrode is based on the use of immobilized tyrosinase and the amperometric detection of the enzymatic product at -50 mV vs. SCE. The enzyme is covalently immobilized on the surface of a carbodiimide-activated graphite electrode. The biosensor responds to a variety of phenolic substrates with different conversion efficiencies. The detection limit for phenol is 0.003 mu M (S/N = 3), a quantification limit of 0.01 mu M (rsd 3.7%), and an extended dynamic range up to 5 mu M is achieved with a sample frequency of 110 samples per hour.