A Review on Electrochemical Microsensors for Ascorbic Acid Detection: Clinical, Pharmaceutical, and Food Safety Applications

Abstract

Nowadays, micro-sized sensors have become a hot topic in electroanalysis. Because of their excellent analytical features, microelectrodes are well-accepted tools for clinical, pharmaceutical, food safety, and environmental applications. In this brief review, we highlight the state-of-art electrochemical non-enzymatic microsensors for quantitative detection of ascorbic acid (also known as vitamin C). Ascorbic acid is a naturally occurring water-soluble organic compound with antioxidant properties and its quantitative determination in biological fluids, foods, cosmetics, etc., using electrochemical microsensors is of wide interest. Various electrochemical techniques have been applied to detect ascorbic acid with extremely high sensitivity, selectivity, reproducibility, and reliability, and apply to in vivo measurements. This review paper aims to give readers a clear view of advances in areas of electrode modification, successful strategies for signal amplification, and miniaturization techniques used in the electroanalytical devices for ascorbic acid. In conclusion, current challenges related to the microelectrodes design, and future perspectives are outlined.

Keywords: electroanalysis; microelectrodes; sensors; vitamin C.

Figure 1

Electrocatalytic oxidation of ascorbic acid.

Figure 2

The potential (A1) and typical response current (A2) of CV; the potential waveform (B1) and voltammogram (B2) of DPV. In the potential waveform, T is the waveform period, and S1 and S2 are the two current sampling points; the typical potential waveform (C1) of SWV, ∆E is the potential increment, T is the potential period. The response current consists of forward (anodic current) and reverse (cathodic current) components (dashed line in (C2)), and their difference results in a net current (solid line in (C2)). Reproduced from Ref. [22]. Licensee 2022 MDPI.

Figure 3

SEM images of (A) CF, (B) VACNT-CF, and the tips of VACNT-CF (C) before and (D) after electrochemical treatment in 1.0 M NaOH. Reprinted with permission from [26]. Copyright 2014 American Chemical Society.

Figure 4

Schematic representation of the array composed by the ascorbate nanocomposite microsensor (left), the glutamate microbiosensor (right), and the micropipette (center) used for local application of solutions in the extracellular space of the rat hippocampus. Reproduced with permission from [27]. Copyright 2018 Elsevier.

Figure 5

(A) Schematic illustration of the in vivo setup for determining AA in rat brain. (B) Optical images before and after the stereotaxic implant into the brain. (C) DPVs recorded at the e−CNF microelectrode in the striatum of a normal rat (I) and the rat brain model of AD (II). (D) DPV responses recorded at the e−CNF microelectrode in the striatum of the rat brain model of AD before (I) and after (II) injection of ascorbate oxidase. Reproduced with permission from [23]. Copyright 2017 American Chemical Society.

Figure 6

Schematic illustration of in vivo microinjection and the designed RECS for selective measurement of cerebral AA in brain microdialysate. Reproduced with permission from [37]. Copyright 2020 American Chemical Society.

Figure 7

(a) Low-magnification SEM image of Ni₆MnO₈ nanoflakes; inset: SEM image of the modified acupuncture needle. (b,c) High-magnification SEM images of the Ni₆MnO₈ nanoflakes. Reproduced from Ref. [45] with permission from the Royal Society of Chemistry.

Figure 8

Design and structure of cMOF−based wearable sweat sensors. (a) Photograph of the wearable sweat sensor that self-adheres to the sweaty skin of humans. (b) Configuration of the layered film sensor, which comprises cMOF, electrode, cellulose, and insulation layers (Ecoflex was used as an insulating layer to encapsulate the interconnected area and avoid contact of the conductive interconnected path with the skin and perspiration). (c) SEM image of the prepared BNC membrane. (d,e) Sectional view and top view SEM images, respectively, of the Ni₃HHTP₂−based working electrode. (f) Current–voltage characteristic of Ni₃HHTP₂ measured using the two-contact probe method. (g) Schematic illustration of the oxidation mechanism of AA and UA catalyzed by Ni₃HHTP₂. (h) The free energy diagrams for AA electrocatalytic oxidation on Ni−based cMOFs using DFT calculations. Reproduced with permission from [47]. Copyright 2022 John Wiley and Sons.

Figure 9

Use of the (Au–Pt–Ag/AgCl) electrochemical microcell for the skin analysis. Reproduced with permission from [50]. Copyright 2013 Elsevier.