Simultaneous detection of guanine, adenine, thymine and cytosine at choline monolayer supported multiwalled carbon nanotubes film.

A rapid, convenient and accurate method for the simultaneous detection of guanine (G), adenine (A), thymine (T) and cytosine (C) was developed at a multiwalled carbon nanotube (MWCNT)/choline (Ch) monolayer-modified glassy carbon electrode (GCE). X-ray photoelectron spectroscopy data demonstrated that Ch was covalently immobilised on the surface of GCE through oxygen atom. The Ch monolayer provides a positively charged surface with -N(+)(CH(3))(3) polar groups, so that it can attract negatively charged MWCNTs to the surface. Consequently, the MWCNT/Ch film exhibited remarkable electrocatalytic activities towards the oxidation of G, A, T and C due to the advantages of high electrode activity, large surface area, prominent antifouling property, and high electron transfer kinetics. All purine and pyrimidine bases showed well-defined catalytic oxidation peaks at MWCNT/Ch/GCE. The peak separations between G and A, A and T, and T and C are 270, 200, and 190 mV, respectively, which are sufficiently large for their potential recognition and simultaneous detection in mixture. Under the optimum conditions, the designed MWCNT/Ch/GCE exhibited low detection limit, high sensitivity and wide linear range for simultaneous detection of G, A, T and C. Moreover, the proposed method was successfully applied to the assessment of G, A, T and C contents in a herring sperm DNA sample with satisfactory results.