The influencing mechanism of acidity on the oxidation peak currents of guanine and uric acid: hydrogen bond catalysis and degree of auxiliary electrode reduction reaction

• The simultaneous determination of G and UA is achieved at the 316L-PAIUCPE.
• The reason of peak current increase is explained based on hydrogen bond catalysis.
• The effect of pH on the degree of anode-cathode reaction was detailedly explored.

In this paper, a pre-anodized inlaying ultrathin carbon paste electrode with 316L stainless steel as a matrix (316L-PAIUCPE) was constructed by a simple and fast electrochemical method. Taking uric acid (UA) and guanine (G) as the target compounds, it was discussed in detail to illustrate the dependent of the peak currents intensity of (ip) of UA and G upon the pH on the basis of the charge properties of the electrode surface active groups, the formation and catalysis of hydrogen bond, the molecular configuration of target, the degree of oxygen reduction reaction at the auxiliary electrode, the oxidation peak potential, distribution coefficient of both UA and G, and so on. A new mechanism was proposed that decreasing of the ip of UA and G with the increasing of pH might result from the degree of oxygen reduction reaction at the auxiliary electrode, although the oxidation peak potential shifted negatively. Moreover, In pH = 5.00 phosphate buffer solution, a linear relationship between oxidation peak current and concentration of UA and G was obtained in the range of 5.0 × 10−7 to 2.2 × 10−4 mol·L−1 and 2.0 × 10−7 to 1.5 × 10−4 mol·L−1 with a detection limit of 8.2 × 10−8 and 3.4 × 10−8 mol·L−1, respectively. The constructed electrode exhibited excellent reproducibility and stability. Finally, this technique was employed for simultaneous determination of UA and G in human urine with satisfactory results.

The guanine was oxidized at the 316L-PAIUCPE, while oxygen dissolved in the solution was reduced at the cathode (Pt). The H+ released in the anode reaction compensated for H+ consumed in the cathode reaction, and the effect of acidity on the degree of anode-cathode reaction was detailedly explored.Figure optionsDownload as PowerPoint slide