Sensitive detection of citric acid in real samples based on Nafion/ZnO–CuO nanocomposites modified glassy carbon electrode by electrochemical approach

Abstract

In this approach, the citric acid (CA) in fruit juices was measured in enzyme-free buffer medium using a GCE (glassy carbon electrode) modified with ZnO/CuO nanocomposites (ZnO/CuO NCs) by DPV (differential pulse voltammetry) and CV (cyclic voltammetry) electrochemical methods respectively. The prepared ZnO/CuO NCs are characterized in detail with XRD (X-ray Diffraction), XPS (X-ray photoelectron spectroscopy), FTIR (Fourier-transform infrared spectroscopy), UV–vis. (Ultraviolet visible spectroscopy), FESEM (Field emission scanning electron microscopy) and EDS (Energy dispersive X-ray spectroscopy) analyses. Both DPV and CV, these techniques were applied with ZnO/CuO NCs/Nafion/GCE to analyze CA in the commercial and natural fruit juices. The current data obtained from electrochemical analysis of CA was plotted against the corresponding concentration of CA and found to distribute on the straight-line in the concentration range of 0.15–1.05 mM of CA, which labeled as a linear dynamic range (LDR) for CA detection. The sensor analytical parameters were calculated by considering the active surface area of GCE (0.0316 cm2) of fabricated electrode over the slope of LDR in both cases (CV and DPV). It was found as 0.4358 μAμM−1cm−2 for DPV and 0.4357 μAμM−1cm−2 for CV respectively. Similarly, the lower limits of detection (DL) applying signal/noise (S/N) ratio 3 are also identical as 21.78 ± 1.09 μM for both electrochemical approaches. The sensor parameters (reproducibility, long-time stability in analyzing and response time) were obtained with good and satisfactory results. Besides this, the proposed sensor was performed trustfully in an analysis of the fruit samples. In this consequence, this electrochemical method with binary mixed metal oxide as sensing substrate to develop a portable sensor might be efficient in the sensor technology.