Electrochemical Determination of Zn 2+ ion us- ing Diphenylamine/Single Walled Carbon Nanotube/Cetyltrimethylammonium Bromide Modified Glassy Carbon Electrode

Abstract

Diphenylamine encapsulated inside a composite film of single walled carbon nano tube (SWCNT) and cationic cetyltrimethylammonium bromide (CTAB) on the surface of Glassy Carbon (GC) electrode can be converted into diphenylbenzidine on application of a potential of +0.600 V versus Ag-AgCl reference electrode for 60 seconds. This modified electrode, in tris buffer solution (pH 7.0), shows reversible cyclic voltammogram due to diphenylbenzidine / diphenylbenzidine violet redox couple. This cyclic voltammogram is observed in pure CTAB film but not observed inside the film of pure SWCNT, polyvinyl pyrollidone or TX-100. In the SWCNT + CTAB film the redox potential is ca. +0.430 V. The oxidation and reduction currents of the modified electrode decreases with the increase in the concentration of Zn 2+ ion in the electrolytic solution. The relative decrease is found to be 0.60 to 0.65. The ions such as Na + , K + , Ca 2+ and Mg 2+ , do not affect the redox currents. Diphenylbenzidine / SWCNT / CTAB modified GC electrode can determine Zn 2+ ion concentration in the range 20 × 10 -6 mol L -1 to 200 × 10 -6 mol L -1 while diphenylbenzidine/CTAB modified GC electrode can determine between 0.2 × 10 -6 mol L -1 to 2 × 10 -6 mol L -1 . A mechanism for the electrochemical inactivation of the electrode by Zn 2+ ions has been proposed.