It is very necessary to develop a sensitive and selective method for the determination of trace catecholamine due to its physiological function and the diagnosis of some disease in clinical medicine. In this research the application of nanomaterials is proposed such as multiwall carbon nanotubes (MWCNTs) and ferrite nickle nanoparticles (NiFe 2 O 4 ) for the modification of glassy carbon electrode to measure epinephrine and methyldopa. The electrochemical behavior of the modified electrode with the nanomaterials in an aqueous buffer solution is studied for the determination of epinephrine (EP) and methyldopa (MD) using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The results showed that the chemically modified electrode exhibits efficient synergic activity in the oxidation of EP and MD. The different parameters on the response of the electrode to measure EP and MD were studied. Under the optimized conditions and by DPV, two linear segments were obtained: the first segment was from 0.9 to 40.0 mM and the second part was from 40.0 to 800.0 mM EP with a detection limit of 0.09 mM. The relative standard deviation for 6 repeated measurements for 50.0 mM EP was obtained 0.9%. The interference of foreign substances on the EP was investigated too. The calibration curve for MD was linear in the concentration range of 0.5 to 900.0 mM MD? with a limit of detection of 0.08 mM MD. The relative standard deviation for 50.0 mM MD was 1.2%. The interference of foreign substances in the determination of MD was investigated too. Finally the proposed sensor was successfully used for the determination of MD and EP in real sample such as human urine? tablet and plasma.
