Polymelamine/gold nanoparticle-modified carbon paste electrode as voltammetric sensor of uric acid

Uric acid (UA), a vital biological substance, should be accurately detected in clinical monitoring and diagnosis. An electrochemical sensor was developed for UA determination based on polymelamine/gold nanoparticle-modified carbon paste electrode (AuNPs/PM/CPE). Carbon paste electrode (CPE) was made by mixing carbon and paraffin powder at a ratio of 7:3. PM/CPE was made using 1 mM melamine electropolymerisation in 0.1 M NaOH solution on the CPE surface with the cyclic voltammetry (CV) technique with a potential range of 0 to +1.6 V, and a scan rate of 100 mV/s. AuNPs/PM/CPE electrodes were made using Au electrodeposition on the PM/CPE surface using a 1 mM HAuCl4 solution containing 0.1 M Na2SO4. Electrodeposition was performed by CV in the potential range of-0.6 to +1.5 V, with a scan rate of 50 mV/s. The electrocatalytic activity towards UA was systematically studied by CV techniques on the surface of CPE, PM/CPE, AuNPs/CPE, and AuNPs/PM/CPE in phosphate-buffered solution (PBS) at pH 7 with the potential of 0 V to + 1 V, and a scan rate of 100 mV/s. The effect of pH and the analysis of real samples using baby urine that had been diluted and spiked with UA were also studied. The results for bare CPE, and AuNPs/PM/CPE showed a 5-fold increase in anodic peak currents for UA. The optimum conditions were pH 5 (PBS 0.1 M) with the scan rate of 100 mV/s. Under this optimised condition, the modified electrode demonstrated high catalytic activity of UA oxidation. The differential pulse voltammetry (DPV) technique was used for quantitative analysis. The performance of AuNPs/PM/CPE electrodes has a linearity range, detection limit, sensitivity, precision, and accuracy of 0.1-11 µM, 0.0647 µM, 7.8592 µA/µM, 0.1107-0.3930%, and 82.45-107.23%, respectively. The results of the UA analysis in the baby urine show that the recovery of the disposed sample was 99.41 ± 0.06%, indicating that these electrodes have good accuracy.