Graphene Oxide-Consecutive Guanine DNA Composite Membrane Modified Electrode for Determination of Dopamine

5 μL of 1 g·L^-1 graphene oxide solution was dipped onto the surface of the polished and cleaned glassy carbon electrode. After dring under infrared light, the electrode was deposited in a 0.1 mol·L^-1 KH₂PO₄ solution at -0.9 V for 600 s. Then the electrode was immersed in 100 μmol·L^-1 continuous guanine DNA solution for 1 h to obtain a graphene oxide-continuous guanine DNA composite membrane modified electrode. The modified electrode was characterized by transmission electron microscopy, scanning electron microscopy and electrochemical method. The electrochemical behavior of dopamine at the modified electrode was studied. It was found that the modified electrode showed obvious electrocatalytic effect on the redox of dopamine. In phosphate buffer solution (pH 7.0), the differential pulse voltammograms of dopamine at the modified electrode were recorded at a scan rate of 50 mV·s^-1. Linear relationships were found between the oxidation peak current and the concentration of dopamine in the ranges of 5.0×10^-7-9.0×10^-6mol·L^-1, 9.0×10^-6-5.0×10^-5mol·L^-1, respectively, and the detection limit (3s/k) was 3.5×10^-8mol·L^-1. The method was used for determining the content of dopamine in body fluids and medicines, giving values of recovery obtained by standard additiom method between 88.0% and 106%, and RSDs (n=5) less than 5.0%.