▎ 摘　　要

This work reports tyrosinase based electrochemical biosensors using graphene modified screen-printed carbon based electrodes for the determination of catecholamines. The enzyme has been immobilized onto the graphene modified carbon working electrodes by cross-linking with glutaraldehyde. The detection has been performed by measuring the cathodic current due to the reduction of the corresponding quinone a low potential, 0.025 V for dopamine and -0.025 V for epinephrine, respectively. The experimental conditions for the tyrosinase immobilization and the main variables that can influence the cathodic current have been optimized. Under optimum conditions, the electrochemical biosensors have been characterized. A linear response range from 0.2 up to 25 mu M of dopamine and from 1 to 27.5 mu M of epinephrine was obtained. The detection limits are in the range 2.42x10(-7) - 6.56x10(-7) M for developed biosensors. The biosensors construction was highly reproducible. Finally, the developed biosensors have been applied to the determination of dopamine and epinephrine content in pharmaceutical formulation samples.