Abstract
SummaryThe oxidation mechanism of all-trans-retinol (vitamin A1) and its several esters in non-aqueous, aqueous organic mixture, and pure aqueous media was investigated by cyclic voltammetry. The oxidation occurred in several irreversible steps. The calculated highest density of electrons in retinoid molecules which are delocalized over carbon atoms of the five conjugated double bonds (C5-C14) was found in the part of the molecule involved in oxidation processes. The most sensitive oxidation peak (at +0.8 V vs. Ag/AgCl) was used for development of new direct voltammetric method based on differential pulse voltammetry for the determination of retinol at carbon paste electrode modified with surfactant sodium dodecyl sulfate (CPE/SDS). The results show that 30% (by mass) of modifier SDS exhibited optimal sensitivity and shape of voltammograms. Compared to commonly used glassy carbon electrode (GCE), the CPE/SDS showed significant progress in the retinol electroanalysis. The linear ranges for retinol determination were 1.5·10−6–1.8·10−4 M for CPE/SDS and 4.4·10−6–7.0·10−4 M for GCE with the detection limits of 1.3·10−6 and 4.6·10−7 M, respectively.
Highlights
IntroductionKnown as vitamin A1, belongs to the group of fat-soluble vitamins generally classified as vitamin A (carotenoids), D (cholecalciferols), E (tocopherols) and K (naphthoquinones)
Retinol, known as vitamin A1, belongs to the group of fat-soluble vitamins generally classified as vitamin A, D, E and K
The study of electrochemical behaviour of several retinoids in CH2Cl2 containing 0.2 M Bu4NPF6 using cyclic voltammetry (CV) at glassy carbon electrode (GCE) confirmed that retinal, retinoic acid, retinyl palmitate and retinyl acetate are oxidized in similar manner as retinol [27]
Summary
Known as vitamin A1, belongs to the group of fat-soluble vitamins generally classified as vitamin A (carotenoids), D (cholecalciferols), E (tocopherols) and K (naphthoquinones). Deficiency (avitaminosis) of vitamin A leads to the night blindness or keratinization of cells. It is often a disease of children, especially occurring in the developing countries. Its surplus (hypervitaminosis) can cause poisoning, especially teratogenesis. It is important that the content of vitamin A in foodstuff and food supplements is very low [1,2]. The poisoning caused by overdosing is rare
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