Electrochemical detection of heavy metals and chloramphenicol using a Nafion/graphene quantum dot modified electrode

Graphene quantum dots (GQDs) with a uniform particle size were successfully synthesized using a simple in-situ electrolytic graphite rod method at a specific current density. Nafion/GQD-modified glassy carbon electrodes (nafion/GQDS/GCE) were then fabricated. Anodic stripping voltammetry and differential pulse voltammetry were utilized for the detection of heavy metals, specifically Pb(II) and Cd(II), as well as chloramphenicol. The results indicated that the dissolution currents for Pb(II) and Cd(II) increased with their concentrations, showing a strong linear relationship. The linear range for Pb(II) was 4.82 × 10⁻⁸ to 9.65 × 10⁻⁷ mol/L (R² = 0.9923), and for Cd(II), it was 1.07 × 10⁻⁷ to 1.96 × 10⁻⁶ mol/L (R² = 0.9912), with detection limits of 1.61 × 10⁻⁸ mol/L for Pb(II) and 3.57 × 10⁻⁸ mol/L for Cd(II). The nafion/GQDS/GCE exhibited significant electrocatalytic activity towards chloramphenicol, with an irreversible reaction involving 6 electrons and an electron transfer rate constant (KS) of 105.4 s⁻¹. The catalytic reduction current for chloramphenicol at the modified electrode ranged from 5.00 × 10⁻⁷ to 2.50 × 10⁻³ mol/L, showing a good linear relationship, and the detection limit (S/N = 3) was 1.67 × 10⁻⁷ mol/L. The nafion/GQDS/GCE also demonstrated excellent anti-interference, stability, and reproducibility, yielding satisfactory results for the detection of actual samples.