Electrochemical oxidation behavior of guanosine-5´-monophosphate on a glassy carbon electrode modified with a composite film of graphene and multi-walled carbon nanotubes, and its amperometric determination

The electrochemical oxidation of guanosine-5′-monophosphate (GMP) was studied with a glassy carbon electrode modified with a composite made from graphene and multi-walled carbon nanotubes. GMP undergoes an irreversible oxidation process at an oxidation peak potential of 987 mV in phosphate buffer solution. Compared to other electrodes, the oxidation peak current of GMP with this electrode was significantly increased, and the corresponding oxidation peak potential negatively shifted, thereby indicating that the modified material exhibited electrochemical catalytic activity towards GMP. Chronocoulometry demonstrates that the material also effectively increases the surface area of the electrode and increases the amount of GMP adsorbed. Under the optimum conditions, the oxidation current is proportional to the GMP concentration in the range from 0.1 to 59.7 μM with a correlation coefficient of 0.9991. The detection limit is 0.025 μM (at S/N = 3). We have developed an electrochemical method for sensitive determination of guanosine-5’-monophosphate (1) based on graphene and multi-walled carbon nanotubes modified glassy carbon electrode by amperometry.