Sustainable uric acid sensor based on a lab-fabricated electrode modified with rice straw-derived carbon materials

Abstract

A novel and facile electrochemical sensor for the quantification of uric acid has been fabricated through the strategic modification of a screen-printed carbon electrode (SPCE) using mesoporous carbon-zinc oxide (MC-ZnO) synthesized from rice straw waste. The MC-ZnO materials, generated via a controlled pyrolysis process, exhibit homogeneous dispersion and a substantial electroactive surface area of 0.1286 cm². The electrochemical oxidation of uric acid exhibits a distinct peak at 0.18 V in differential pulse voltammetry (DPV), indicative of efficient charge transfer kinetics. A linear range spanning 20 to 225 µM was obtained with a limit of detection (LOD) of 3.76 µM, signifying exceptional analytical sensitivity. Furthermore, the sensor demonstrates robust selectivity toward uric acid in the presence of typical interferents, underscoring its applicability for precise uric acid determination in complex biological matrices. The sensor's analytical performance was validated by quantifying uric acid in spiked urine samples, yielding recovery rates between 97.9% and 114.8% and relative standard deviations (RSD) below 4.92%, affirming its accuracy and precision. This platform heralds a promising avenue for clinical diagnostics, leveraging sustainable materials for uric acid detection.

Keywords: Agricultural waste; Biomass; Eco-friendly sensor; Modified electrode; Voltammetry.

Fig. 1

Schematic representation of the fabrication and working principle of the electrochemical sensor for uric acid detection.

Fig. 2

XRD patterns of ZnCl₂-activated carbons.

Fig. 3

SEM images of bare SPCE (a) and MC-ZnO/SPCE (b), EDS spectra of bare SPCE (c) and MC-ZnO/SPCE (d), and TEM image of MC-ZnO (e).

Fig. 4

Cyclic voltammograms (a) and Nyquist plots (b) of bare SPCE and MC-ZnO/SPCE in 10 mM ferri-ferrocyanide.

Fig. 5

The pH optimization for uric acid detection using MC-ZnO/SPCE consisted of DPV peaks of 0.1 mM uric acid in phosphate buffer solutions across a range of pH values (a), oxidation potential as a function of pH (b), anodic peak current and phosphate buffer pH (c), and proposing an electrochemical mechanism for uric acid oxidation and product formation (d).

Fig. 6

Cyclic voltammograms of 0.1 mM uric acid in phosphate buffer (pH 7.0) recorded at varying scan rates (a) and Linear correlation between the oxidation current and the square root of the scan rate (b).

Fig. 7

DPV peaks of varying uric acid concentrations (a) and Linear calibration plot for the determination of uric acid (b).