Simultaneous detection of ascorbic acid and dopamine on nickel (II) tetra amino phthalocyanine, iron oxide decorated graphene oxide nanosheets modified glassy carbon electrode

Abstract

Ascorbic acid and dopamine are biomolecules found in humans. They both have important functions in the body and cause numerous side effects at high concentrations. An electrochemical sensor based on nickel( II) tetra amino phthalocyanine conjugated to iron oxide doped graphene oxide nanosheets was developed.FTIR,UV- vis, cyclic voltammetry ( CV) and electrochemical impedence spectroscopy (EIS) were used for characterisation of electrode modifiers.FTIR was used to ascertain that a chemical linkage between NiTAPc ,GONs and iron oxide had occurred.CV, chronoamperometry ,linear sweep and differential pulse voltammetry were used to assess the electrocatalytic oxidation of ascorbic acid and dopamine. The surface area of NiTAPc-GONs-Fe 2 O 3/GCE was 0.208 cm2. The limit of detection and limit of quantification of ascorbic acid were found to be 8.6× 10 -8 M and be 2.6 × 10 -7 M respectively and LOD and LOQ for dopamine was found to be 2.58 x 10 -8 M and 6.8 ×10 -8 M. The catalytic rate constant was found to be 2.59 ×102M-1s-1 for ascorbic acid and 1.56 ×102 M-1s-1 for dopamine. The adsorption equilibrium constant for ascorbic acid and dopamine was 6.4 x 102 M-1 and 8.05 x 102 M-1 respectively. Gibbs free energy for ascorbic acid and dopamine was found to be - 16.01 kJ and -16.57 kJ respectively. Interference studies were done and the electrode displayed the ability to detect both ascorbic acid, dopamine and citric acid simultaneously. The electrode displayed good reproducibility with lower oxidation potentials at 0.8 V for ascorbic acid and V for dopamine. NiTAPc-GONs-Fe 2O3-GCE showed high sensitivity and stability towards the detection of dopamine and ascorbic acid.