Simultaneous voltammetric determination of guanine and adenine by using a glassy carbon electrode modified with a composite consisting of carbon quantum dots and overoxidized poly(2-aminopyridine)

A composite consisting of carbon quantum dots (CQDs) and overoxidized poly(2-aminopyridine) (PAPox) was deposited on a glassy carbon electrode (GCE) through electrochemical polymerization and electrochemical oxidation. The modified GCE was used for the simultaneous determination of guanine and adenine. Electrochemical responses to guanine and adenine were investigated by cyclic voltammetry and differential pulse voltammetry. Owing to the synergistic effect of CQDs and PAPox, two oxidation peaks can be observed, with peaks at 0.81 and 1.13 V (vs. SCE) for guanine and adenine, respectively. The current at the respective peaks has a linear dependence on the concentrations of guanine in the range from 1.0 to 65 μM, and of adenine in the range from 2.0 to 70 μM. The respective detection limits are 0.51 and 0.39 μM (at an S/N ratio of 3). The modified GCE is selective, reproducible and stable.