Virgin olive oil phenols-spectroscopic evaluation in basic medium: Analysis of total content of hydroxytyrosol

Abstract

Here a spectrophotometric technique in the visible region combined with an environmental friendly ultra-pure water based liquid-liquid extraction procedure has been described for the determination of total hydroxytyrosol in virgin olive oils regardless of whether it is free or combined. Determination of total hydroxytyrosol was carried out where the absorption peak of the colored compounds formed with autopolymerization of quinones that occured following the oxidation of hydroxytyrosol and its secoiridoid derivatives in a basic medium was measured as an analytical signal. The method was linear in a concentration range of 0.2-15.0 mg L-1 with a correlation coefficient of 0.9990. Detection and quantification limits were 0.05 and 0.18 mg L-1, respectively. Intra-day and inter-day precision studies indicated that the proposed method was repeatable. In addition, the liquidliquid extraction procedure was quite efficient with recovery values between 108 and 117%. Finally, the proposed method was successfully applied to the analysis of total hydroxytyrosol in a virgin olive oil and the results were compared with those obtained by a method existing in the literature for the determination of total hydroxytyrosol based on acid hydrolysis of secoiridoid aglycons followed by liquid chromatography-tandem mass spectrometry. © 2020, Universitatea Babes-Bolyai, Catedra de Filosofie Sistematica. All rights reserved.