Application of deep eutectic solvents for the extraction of phenolic compounds from extra-virgin olive oil

A HPLC–DAD/ESI–MS method has been developed and validated for the analysis of themost representative phenolic compounds in extra-virgin olive oil (EVOO) samples usinga green extraction approach based on deep eutectic solvents (DESs) at room temperature.We examined ten DESs based on choline chloride and betaine in combination with dif-ferent hydrogen bond donors comprising six alcohols, two organic acids, and one urea.Five phenolic compounds, belonging to the classes of secoiridoids and phenolic alcohols,were selected for the evaluation of extraction efficiency. A betaine-based DES with glycerol(molar ratio 1:2) was found to be the most effective for extracting phenolic compounds ascompared to a conventional solvent. The optimization of the extraction method involvedthe study of the quantity of water to be added to the DES and evaluation of the sample-to-solvent ratio optimal condition. Thirty percent of water added to DES and sample tosolvent ratio 1:1 (w/v) were selected as the best conditions. The chromatographic methodwas validated by studying LOD, LOQ, intraday and interday retention time precision, andlinearity range. Recovery values obtained spiking seed oil sample aliquots with standardcompounds at 5 and 100μg/g concentration were in the range between 75.2% and 98.7%.