Electrochemical Behaviour of Tocopherols: Possibilities of Their Simultaneous Voltammetric Detection

Granit Jashari,Radovan Metelka,Lucie Korecká,Amir M Ashrafi,Milan Sýs,Gylxhane Kastrati

doi:10.3390/app11178095

Granit Jashari, Radovan Metelka + Show 4 more

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https://doi.org/10.3390/app11178095

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Abstract

An electroanalytical study for possible simultaneous detection of three naturally occurring isomers of vitamin E (α, γ, and δ-tocopherol) was performed. This research includes several optimization steps, such as selection of electrode material, composition of working medium, selection of electrochemical technique, and parameters of square-wave voltammetry (SWV), to reach a well-defined recognition of peaks. A glassy carbon electrode, 99.9% acetonitrile containing 0.1 mol L−1 lithium perchlorate, SWV at the potential step of 1 mV, potential amplitude of 25 mV, and frequency of 25 Hz were decided as the most suitable working conditions. Nevertheless, the corresponding anodic peaks were not sufficiently separated due to their overlapping. Thus, four standard evaluation methods (polynomial or linear baseline, zero base, and deconvolution) were compared, and the last-mentioned method was chosen as optimum. Similar linear ranges from 3.0 × 10−6 to 1.0 × 10−5 mol L−1 were obtained for α, γ, and δ-tocopherol, characterized by determination coefficient of 0.998, 0.985, and 0.994, quantification limits of 11.28, 2.70, and 3.67 × 10−6 mol L−1 and detection limits of 3.72, 0.89, and 1.21 × 10−6 mol L−1, respectively. A recovery from 72.0 to 128.5% for different concetration ratios of tocopherols has been achieved. This recovery range is in the accordance with values reported for liquid chromatography.

Highlights

IntroductionTocopherols as major forms of vitamin E (VE) are considered as naturally occurring lipophilic phenolic antioxidants, especially in vegetable oils such as corn, soybean, cottonseed, and sesame [1]
It has been suggested that the biggest role of vitamin E (VE) in the human body is the protection from different aggressive processes such as cancer, especially hepatocellular carcinoma (HCC), and prevention of the progression of pre-cancerous lesions, cataracts, and different cardiovascular diseases
The lithium perchlorate, 99.99% surfactants such as Triton X-100, 98% sodium dodecyl sulfate (SDS), 99–102.0% cetylpyridinium chloride (CPC), 99% cetyltrimethylammonium bromide (CTAB), and analytical standards of (+)-α-tocopherol, (+)-γ-tocopherol and (+)-δtocopherol were purchased from Merck KGaA (Darmstadt, Germany)

Summary

Introduction

Tocopherols as major forms of vitamin E (VE) are considered as naturally occurring lipophilic phenolic antioxidants, especially in vegetable oils such as corn, soybean, cottonseed, and sesame [1]. Often, they are found in pharmaceuticals and cosmetics products due to their biological activity [2,3,4], which consists of polyunsaturated fatty acids and their esters, renowned for inhibiting free-radical chain auto-oxidation [5,6,7,8,9]. Its deficiency may contribute to the most common circulatory disorders [3,10,11,12,13], such as fertility disorder, Alzheimer’s disease, etc. [14]

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