Simultaneous determination of guanine, adenine and thymine using a modified carbon paste electrode by TiO2 nanoparticles-magnesium(II) doped natrolite zeolite

Abstract

A novel, simple and reliable electrochemical method for simultaneous determination and direct electro-oxidation behaviors of guanine (G), adenine (A) and thymine (T) was developed at a TiO2 nanoparticles-magnesium doped zeolite Y modified carbon paste electrode (TiO2NPs-MgY/ZMCPE). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were used to examine the structure of the TiO2NPs-MgY/ZMCPE. The measurements were carried out using cyclic voltammetry in phosphate buffer solution with pH 7.2. This modified electrode exhibits potent and persistent electro-oxidation behavior followed by well-separated oxidation peaks toward G, A and T with increasing the oxidation current. The electrochemical behaviors of guanine, adenine and thymine on the modified electrode were carefully studied by cyclic voltammetry and the electrochemical parameters such as the area of the electrode (A), the electron transfer number (n), the electron transfer coefficient (α), the electrode reaction standard rate constant (ks), and the surface coverage (ГT) were calculated. Differential pulse voltammetry (DPV) was proposed for simultaneous determination of three DNA bases. Under the selected conditions the oxidation peak currents were proportional to guanine, adenine and thymine concentrations in the range from 0.1 to 100μM, 0.1 to 100μM and 8 to 1000μM respectively with the detection limit as 0.013, 0.02 and 0.878μM (3σ) and relative standard deviation (RSD%) 5.25%, 6.5% and 8.63% (n=10 for guanine, adenine and thymine respectively). The proposed method showed good selectivity to the G, A and T detection without the interferences of coexisting substances.