Simultaneous and Ratiometric Electrochemical Determination of Uric Acid and Hypoxanthine Based on In Situ Carbonized Polydopamine Graphene Paper

High levels of uric acid (UA) and xanthine (XA) in the human body can lead to various illnesses, highlighting the crucial need to detect UA and XA levels in the body. In this work, a ratiometric electrochemical detection platform was constructed for the simultaneous determination of UA and XA. Polydopamine (PDA) was initially modified in situ on graphene paper (Gp) and carbonized to fabricate the cPDA-Gp electrode. Methylene blue (MB) is coupled to cPDA-Gp as an internal reference and is designated as MB/cPDA-Gp. The electrochemical behavior of UA and XA on MB/cPDA-Gp was studied by cyclic voltammetry and differential pulse voltammetry. There were distinct anodic peaks on the electrode that corresponded to the oxidation of UA and XA in the concentration ranges of 0.6–350 and 2–160 μM, with detection limits of 0.2 and 0.67 μM, respectively (S/N = 3). For simultaneous detection of changes in UA and XA concentrations, the response range was 1–300 μM, with detection limits of 0.34 and 0.67 μM (S/N = 3), respectively. The sensing platform has been successfully utilized to detect UA and XA in real samples with satisfactory results, indicating that it can be a reliable sensor for detecting these analytes.