MWNT-Based Electrode for the Voltammetric Quantification of Carvacrol
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MWNT-Based Electrode for the Voltammetric Quantification of Carvacrol Guzel Ziyatdinova 1
&
Herman Budnikov 1
Received: 28 June 2020 / Accepted: 14 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWNTs) dispersed in anionic surfactant sodium dodecylsulfate (MWNTs/GCE) has been developed for the carvacrol quantification. The electrode modification provides electrocatalytic effect to carvacrol oxidation (the cathodic shift of the oxidation potential on 121 mV and 1.7-fold increase of the oxidation currents vs. GCE). The electrodes are characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The 8.4-fold higher effective surface area has been obtained for the modified electrode (75 ± 2 mm2 for MWNTs/GCE vs. 8.9 ± 0.2 mm2 for GCE). EIS data have shown 6-fold lower charge transfer resistance in comparison to GCE. The irreversible diffusion-controlled oxidation of carvacrol with participation of one electron and one proton has been proved. The parameters of electrooxidation have been calculated. Differential pulse voltammetric quantification in phosphate buffer pH 6.5 can be performed in the ranges of 0.1–25 and 25–150 μM of carvacrol. The detection limit of 0.075 μM has been achieved. The method developed has been successfully applied for the determination of total isopropylmethylphenols in oregano spices. The results obtained have been compared to independent spectrophotometric method data. Keywords Voltammetry . Modified electrodes . Carbon nanotubes . Carvacrol . Isopropylmethylphenols . Oregano . Food analysis
Introduction Carvacrol (5-isopropyl-2-methylphenol) is a natural phenolic monoterpenoid isolated from aromatic plants in particular their essential oils (De Vincenzi et al. 2004). Origanum vulgare, Thymus vulgaris, Lepidium flavum, Citrus aurantium bergamia are the main sources of carvacrol (De Vincenzi et al. 2004; Friedman 2014; Ziyatdinova and Budnikov 2018a). Like another isopropylmethylphenol thymol, carvacrol has shown an antimicrobial, antioxidant, and anticancer activities that can provide positive health effect (Sharifi-Rad et al. 2018). These properties of carvacrol allowed its application Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12161-020-01895-0) contains supplementary material, which is available to authorized users. * Guzel Ziyatdinova [email protected] 1
Analytical Chemistry Department, A.M. Butlerov Institute of Chemistry, Kazan Federal University, Kremlyevskaya 18, Kazan, Russian Federation 420008
as a natural food preservative and flavoring additive. Nevertheless, antioxidant activity of carvacrol is dosedependent that is typical for the natural phenolic antioxidants (Ziyatdinova and Budnikov 2015). High concentration of low-molecular antioxidants provides pro-oxidant action. Thus, carvacrol level in plant sources including spices has to be con
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