Electrochemical detection of adenine and guanine using a self-assembled copper(II)-thiophenyl-azoimidazole complex monolayer modified gold electrode

Electrochemical detection of adenine (A) and guanine (G) using the self-assembled monolayer of copper(II)-thiophenyl-azo-imidazole modified gold electrode (Cu2+-IATP-Au) is reported. The self-assembled momolayer of 4-(2'-imidazolylazo) thiophenol (IATP) on a gold electrode surface was prepared by covalent immobilization of imidazole onto a 4-aminothiophenol monolayer modified gold electrode by a diazotization-coupling reaction. The catalyst was formed by immobilizing Cu(II) ion on the IATP modified gold electrode. The modified gold electrode was characterised by Field emission scanning electron microscopy, Energy dispersive X-ray analysis, Infrared spectroscopy, Cyclic voltammetry and Electrochemical Impedance spectroscopic techniques. The Cu2+-IATP-Au electrode exhibits excellent electrocatalytic activity towards the oxidation of A and G. Without separation or pre-treatment, the modified electrode can detect A and G simultaneously in a mixture and DNA samples. In the presence of excess common interferents such as ascorbic acid, citric acid, cysteine, glucose, Na+, K+, Cl-, SO42- had no effect on the peak current of A and G. In differential pulse voltammetry measurement, the oxidation current response of A and G was increased linearly in the concentration range 10-60 mu M and the detection limit was found to be 0.06 mu M and 0.01 mu M (S/N = 3), respectively. The proposed method was applied to determine adenine and guanine in herring sperm DNA and the result was satisfactory.