Abstract: Hemoglobin exhibits such a slow rate of electron transfer that no useful current is observed at conventional electrodes, even with the application of relatively large overpotentials, for reasons ascribed to its extented three-dimensional structure and the resulting in accessibility of the electroactive center or to its adsorption onto and subsequent passivation of the electrode surface.Only a few papers dealing with the hemoglobin redox behaviour at solid electrodes have been reported.In the present work, the carbon paste electrode modified with a new mediator cresyl fast violet shows an electro-catalytic activity to the reduction of hemoglobin.In the medium of 0.2 mol/L NaOAc-HOAc (pH = 5.5), the oxidation and reduction peak potentials of the CMEare E_pa= - 0.14 Vand E_pc=- 0.28 V (vs.SCE), respectively.The CMEshows a good stability and a good current response for hemoglobin.

Key words: Hemoglobin, Chemically modified carbon paste electrode, Electrocatalysis, Cresyl fast violet