Electrochemical Determination of Zn2+ Ion Using Diphenylamine/Single Walled Carbon Nanotube/Cetyltrimethylammonium Bromide Modified Glassy Carbon Electrode

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 Zn²⁺ ion in the electrolytic solution. The relative decrease is found to be 0.60 to 0.65. The ions such as Na⁺, K⁺, Ca²⁺ and Mg²⁺, do not affect the redox currents. Diphenylbenzidine/SWCNT/CTAB modified GC electrode can determine Zn²⁺ 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 Zn²⁺ ions has been proposed.