engleski

Tyrosinase Enzyme-Biosensor For L-Ascorbic Acid Determination

Tyrosinase is a copper-containing enzyme which catalyzes, in the presence of molecular oxygen two reactions: the transformation of o- mono-phenols into catechols and the oxidation of catechol to o- quinone. Various inhibitors of tyrosinase are know so as cyanide, herbicides and phenolic compounds. The inhibitory action of L-Ascorbic acid on enzymatic activity of tyrosinase have been studied. An amperometric biosensor based on enzyme kinetics of tyrosinase for L-Ascorbic acid was developed. Graphite electrode was applied as transductor. The biosensor was constructed by using gelatin or CSA and crosslinking agent glutaraldehyde to immobilise tirosinase (Mushroom tyrosinase) on carbon disk electrode. Electrode surface was previously modified with K2NiII[FeII(CN)6] in order to catalize the oxidation or reduction of solute species electrocatalytic activity. Measurements are generally carried out by Flow-injection analisyis (FIA). The proposed electrochemical procedure was successfully applied to determination of vitamin C in soft drinks and fruit juces. A detection limit of 4.5· ; 10– 5 mol L– 1 was obtained. The results were compared by a reference spectrophotometric method.

L-ascorbic acid; tyrosinase; amperometric biosensor

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