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.
This work reports on the successful synthesis of antimony oxide nanoparticles (AONPs) by hydrothermal method, acid treatment of multi-walled carbon nanotubes (f-MWCNTs), and fabrication of a MWCNT-AONP nanocomposite on screen-printed carbon electrodes (SPCE) to detect serotonin (5-HT) in tomatoes. The synthesized nanomaterials were all characterized with x-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV–vis) spectroscopy, and transmission electron microscopy (TEM). The electro-analytic and electrocatalytic experiments were performed utilizing square wave voltammetry (SWV) and cyclic voltammetry (CV) methods. The SPCE-MWCNT-AONP modified electrodes showed better electron transport and improved current response towards detection of 5-HT when compared to other electrodes studied. The current response decreased in this manner, the SPCE-MWCNT-AONP (84.13 μA) > SPCE-fMWCNTs (33.49 μA) > SPCE-AONPs (24.40 μA) > SPCE-bare (2.89 μA). The sensitivity, limit of detection (LoD) and limit of quantification (LoQ) for the SPCE-MWCNT-AONP modified electrode towards 5-HT detection was 0.2863 μA μM−1, 24 .6 nM, and 74 nM respectively, with linearity from 0.016–0.166 μM (R2 = 0.9851) utilizing SWV. The acquired LoD value for the proposed sensor compared favorably with other chemically modified electrodes from literature. Furthermore, the proposed sensor showed good reproducibility and excellent anti-interference behavior. Real-sample analysis of 5-HT in tomatoes showed excellent recoveries ranging from 91.32 to 108.28%, with an average RSD (%) value of 2.57 (n = 3). The obtained results strongly suggest that the proposed novel sensor could be applicable in diagnosing point-of-care diseases and therapeutics.
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