Amperometric biosensor based on polypyrrole and tyrosinase for the detection of tyramine in food samples

An electrochemical tyrosinase electrode for detection of tyramine was developed via cross-linking immobilization method over phosphate-doped polypyrrole film. The enzyme tyrosinase immobilized over the polypyrrole thin film preserves well its biocatalytic activity. Tyramine was determined by the direct reduction of biocatalytically formed dopaquinone at −0.250 V. The analytical characteristics of this biosensor, including linear range, detection limit, repeatability and storage stability are described. The kinetics of the enzymatic reaction fitted into a Michaelis–Menten type kinetic, as confirmed by the h parameter close to 1 obtained from the Hill's plot. Under the optimum conditions, the current response had a linear relationship with the concentration of tyramine in the range of 4–80 × 10−6 M, with a sensitivity of 0.1069 A M−1 and a limit of detection of 5.7 × 10−7 M. The biosensor exhibited high repeatability and long term stability. Determination of tyramine in real samples showed good recovery. The selective detection is related to specific action of tyrosinase toward phenolic group from tyramine (1-hydroxy-4-ethylaminobenzene). The developed biosensor was applied to the determination of the tyramine content in sauerkraut samples.