Fig. 10. DPV curves of SMZ and TMP mixture on CPE/SiO₂-GOQDs (a) and CPE (b), and linear relationship between peak currents and the concentrations of the analytes (inset). The analytes were present in a mixture (5 : 1) with the following concentrations of SMZ: (a) 4.0, 8.0 and 20 μmol L⁻¹; (b) 4.0 μmol L⁻¹. Supporting electrolyte: 0.04 mol L⁻¹ of BRbs (pH 5.8), 0.5 mol L⁻¹ of NaNO₃.