Electroactivated Disposable Pencil Graphite Electrode – New, Cost‐effective, and Sensitive Electrochemical Detection of Bioflavonoid Hesperidin

Abstract

In this paper, for the first time, electroactivated disposable pencil graphite electrode (ePGE) was used for the detection of bioflavonoid hesperidin with cyclic and differential pulse voltammetry. The electroactivation efficiency of the pencil graphite electrode (PGE) was examined employing electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) and the enhancement of electron transfer kinetics of the PGE after the electroactivation was found. Hesperidin is irreversibly oxidized on the ePGE and its oxidation was the most pronounced at pH=5.0. Two electrode processes were detected, on one hand, a mixed diffusion and adsorption control was observed for the first electrode process. On the other hand, only diffusion control was observed in the second electrode process. Linear dependence between the peak current and the hesperidin concentration was obtained in the concentration range from 5×10−7 mol dm−3 to 1×10−5 mol dm−3 and the determined lower limit of detection (LOD) was 2×10−7 mol dm−3. Moreover, hesperidin in pharmaceutical formulation (containing active substance, hesperidin, and excipients) was quantified using ePGE. A good correlation was obtained between experimentally obtained hesperidin concentration by voltammetric analysis and concentration determined by standard HPLC technique (R2=0.9462).

Rapid Voltammetric Screening Method for the Assessment of Bioflavonoid Content Using the Disposable Bare Pencil Graphite Electrode

“…Despite the fact that it was beyond the aim of our study to establish an exact mechanism for HESP voltammetric behavior at H type PGE, correlating the cyclic voltammetric results with the data existing in the literature [5,16,21,23,25], it was concluded that, also similar to diosmin [19], peak a2 was due to the irreversible oxidation of the guaiacol moiety (3 -OH, 4 -OCH 3 , the o-methoxyphenol group in ring B (Figure 1)) to o-benzoquinone. However, recent theoretical calculations regarding the relationship between the first anodic peak potential and the changes in the electronic structure of flavonoids pointed out that the electrochemical oxidation of these compounds, including HESP, start with the abstraction of an electron [39].…”

“…The first electrochemical investigations of flavonoids were based on their reduction at mercury electrodes, but the presence of the hydroxyl groups in their structure enables also their electrooxidation. This was investigated since the 1980s, starting with the glassy carbon electrode (GCE) [16] and employing many other electrodes either bare [5,[17][18][19], electroactivated [20,21] or modified with different carbon based materials like carbon nanotubes [22][23][24] or graphene derivatives [25][26][27][28], nanomaterials [26,[28][29][30], polymeric films [27,28,31], etc. Unfortunately, most of the electrodes encounter problems due to the electroactive surface fouling during the electrochemical investigations, especially when these are based on the oxidation of phenolic compounds, which can generate phenoxy radicals able to polymerize and produce a film covering the electrode surface.…”

“…These drawbacks can be minimized by using simple, cost-effective, and easy renewable working electrodes, like the pencil graphite electrode (PGE). Therefore, despite the fact that there is a huge number of papers published regarding the use of PGEs as working electrodes for the electroanalysis of very different species, only a recent paper [21] describes a differential pulse voltammetry (DPV) method for HESP determination using an electroactivated PGE. However, the present work brings forward a simpler and even more sensitive DPV assay using an unmodified and non-activated PGE.…”

“…However, the present work brings forward a simpler and even more sensitive DPV assay using an unmodified and non-activated PGE. The current electroanalytical method is eco-friendly due to the reduced consume of reagents, more rapid (no required electroactivation or other electrode surface modification steps), and has a lower limit of detection (8.58 × 10 −8 mol/L compared to 2.00 × 10 −7 mol/L [21]) and a wider linear range (1.00 × 10 −7 -1.20 × 10 −5 mol/L vs. 5.00 × 10 -7 -1.00 × 10 -5 mol/L [21]) achieved by the proper selection of the graphite pencil lead type and supporting electrolyte. The limit of detection was further decreased (1.90 × 10 −8 mol/L) by exploiting HESP reduction signal after the analyte adsorptive accumulation at positive potentials, being thus better than LODs attained with some modified working electrodes [30,32].…”

An Electrochemical Sensor Based on Amino Magnetic Nanoparticle-Decorated Graphene for Detection of Cannabidiol

“…The slope of the equation was ~−0.053 V pH −1 , similar to the theoretical Nernstian slope of 0.059 V pH −1 . This parameter corresponded to an oxidation mechanism that included the exchange of an equal number of protons and electrons in the reaction [ 40 ].…”