Electrochemical behavior and detection of guanine using a sodium montmorillonite-modified carbon paste electrode

Herein, a sodium montmorillonite-modified carbon paste electrode is described for the electrochemical determination of guanine. Guanine yields a well-defined and very sensitive oxidation peak at the sodium montmorillonite-modified carbon paste electrode. Compared with the unmodified carbon paste electrode, the modified electrode facilitates the electron transfer of guanine, since it notably increases the oxidation peak current and lowers the oxidation overpotential of guanine. Based on this, a simple sensitive reliable electrochemical method is proposed for the detection of guanine after all the experimental parameters, such as solution pH value, sodium montmorillonite content in the carbon paste electrode, accumulation potential, and time, are optimized. Under the optimized conditions, the oxidation peak current of guanine varies linearly with its concentration in the range 5.0 x 10(-8) to 2.0 x 10(-5) M and the detection limit (signal-to-noise = 3) is 2.0 x 10(-8) M after 4-min accumulation. This method is successfully demonstrated with urine samples.