Reversed-Phase Dispersive Liquid-Liquid Microextraction with Multivariate Optimization for Sensitive HPLC Determination of Tyrosol and Hydroxytyrosol in Olive Oil

Abstract

A reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) method coupled to HPLC was developed for the extraction of hydroxytyrosol (HTy) and tyrosol (Ty) from virgin olive oil. In this first application of the RP-DLLME method to non-polar samples, the phenolic compounds were directly extracted into an aqueous micro-drop, which could be injected into a chromatography column without any further pretreatment. A glass test tube with lengthened conical bottom was fitted inside a centrifuge tube in this work for more efficient withdrawal of the sedimented phase with a microsyringe. The volumes of water and ethyl acetate, the pH of water and the centrifuge time as four effective parameters on the extraction were optimized by a central composite design (response surface) method. Five replicated analyses under the optimized conditions (i.e., 0.2 mL ethyl acetate as disperser and 100 µL water at pH 11 as the extraction solvent) resulted in recoveries of 104.3 and 97.6%, and relative standard deviations of 5.75 and 4.57 for HTy and Ty, respectively. The detection limit of the method (3σ) was 0.043 mg L(-1) for HTy and 0.032 mg L(-1) for Ty. The method was successfully applied to the determination of HTy and Ty in five olive oil samples.

Reversed‐phase vortex‐assisted liquid–liquid microextraction: A new sample preparation method for the determination of amygdalin in oil and kernel samples

“…For the clean‐up and preconcentration of extracted amygdalin by UAE, cyclohexane extract was subjected to RP‐VALLME. Similar to previous RP extraction methods , an aqueous phase was used as extracting solvent. On the other hand, 100 μL of several organic solvents such as ethanol, methanol, ACN, THF, and mixture of ACN/THF (50:50, v/v) were used as disperser solvent.…”

“…When the target analyte is hydrophilic, the extraction process can be done in reverse mode, which means the extracting solvent is aqueous phase. Recently, a new design of dispersive liquid–liquid microextraction (DLLME) termed as RP‐DLLME has been developed for the preconcentration and determination of phenolic compounds from olive processing wastewater and virgin olive oil . In other reports, several methodologies for the determination of pyrethroid pesticides, cadmium, lead, and different selenium species present in edible oils are introduced by using DLLME .…”

Paradigm Shift in the Arena of Sample Preparation and Bioanalytical Approaches Involving Liquid Chromatography Mass Spectroscopic Technique

“…74,75 The LPME procedure utilizes a very small volume of water-immiscible solvents (usually in microliters) in order to concentrate drugs from the aqueous phase. 76 It is advantageous over LLE and SPE techniques as it is fast, requires a simple set-up, and is not dependent on a commercial device. The established form of solvent-based microextraction techniques are single drop microextraction, headspace single drop microextraction, and dispersive liquid-liquid microextraction.…”

Rapid determination of hydrophilic phenols in olive oil by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and screen-printed carbon electrodes

“…After extraction (lasting a few seconds or minutes), phases are separated by centrifugation and the enriched aqueous phase is retrieved for subsequent analysis. RP-DLLME has been employed prior to LC analysis to determine hydrophilic phenols in VOO previously [18][19][20][21][22]; however, to the best of our knowledge, this miniaturized extraction technique in conjunction with electrochemical analysis has not been proposed to date.…”