Electrochemical Detection of Ascorbic Acid in Oranges at MWCNT-AONP Nanocomposite Fabricated Electrode

Abstract

Ascorbic acid (AA) is an essential vitamin in the body, influencing collagen formation, as well as norepinephrine, folic acids, tryptophan, tyrosine, lysine, and neuronal hormone metabolism. This work reports on electrochemical detection of ascorbic acid (AA) in oranges using screen-print carbon electrodes (SPCEs) fabricated with multi-walled carbon nanotube- antimony oxide nanoparticle (MWCNT-AONP) nanocomposite. The nanocomposite-modified electrode displayed enhanced electron transfer and a better electrocatalytic reaction towards AA compared to other fabricated electrodes. The current response at the nanocomposite-modified electrode was four times bigger than the bare electrode. The sensitivity and limit of detection (LOD) at the nanocomposite modified electrode was 0.3663 [AA]/µM and 140 nM, respectively, with linearity from 0.16-0.640 μM and regression value R² = 0.985, using square wave voltammetry (SWV) for AA detection. Two well-separated oxidation peaks were observed in a mixed system containing AA and serotonin (5-HT); and the sensitivity and LOD were 0.0224 [AA]/µA, and 5.85 µΜ, respectively, with a concentration range from 23 to 100 µM (R² = 0.9969) for AA detection. The proposed sensor outperformed other AA sensors reported in the literature. The fabricated electrode showed great applicability with excellent recoveries ranging from 99 to 107 %, with a mean relative standard deviation (RSD) value of 3.52 % (n = 3) towards detecting AA in fresh oranges.

Keywords: antimony oxide nanoparticles; ascorbic acid; electrochemical sensors; nanocomposite; oranges.

Figure 1

Comparative cyclic voltammograms at modified and bare electrode for (a) AA detection, (b) comparative currents response between bare and modified electrode, (c) scan rate study (10–350 mVs⁻¹), and (d) shows a linear relationship between Ipa vs. v^1/2.

Scheme 1

AA redox mechanism pathway.

Figure 2

(a) AA detection within the 0.16–0.640 μM linear range, and (b) corresponding linear plots.

Figure 3

(a) Detection of AA from 23 to 100 μM concentration range in the presence of 0.5 mM 5-HT, (b) corresponding linear curves, and (c) simultaneous detection of 0.5 mM (AA and 5-HT) at the proposed electrode.

Figure 4

(a) Reproducibility study and (b) shelve-life study carried out at the constructed sensor.