A deep eutectic solvent-based one-step microextraction and hydrolysis of antioxidant precursors in extra virgin olive oil coupled to capillary electrophoresis analysis

This paper proposes a one-step microextraction and hydrolysis approach for the capillary electrophoresis determination of the antioxidants hydroxytyrosol (HTy) and tyrosol (Ty) in extra virgin olive oil released from their antioxidant precursors. This method, based on the use of ethaline (a deep eutectic solvent obtained from choline chloride and ethylene glycol in a 1:2 M ratio) to which sulfuric acid was added at a 1 M concentration, allows the release of these phenolic compounds from their antioxidant precursors in which they are present as linked species in complex chemical structures. The performance of the developed method was evaluated by initially using fortified seed oil samples and subsequently using samples of extra virgin olive oil (EVOO). Under the optimized conditions identified throughout our tests it was possible to obtain satisfactory results for the hydrolysis process conducted in ethaline with yields of approximately 94 ± 7% and detection limits for their electrophoresis determination, estimated for a signal to noise ratio of 3, equal to 40 μM for HTy and 60 μM for Ty. The results obtained by the proposed procedure were compared with those provided by an extraction and hydrolysis method followed by HTy and Ty chromatographic determination reported in the literature. The developed method allows the rapid and efficient extraction of antioxidants from oils using minimal amounts of reagents in significantly shorter times than conventional methods and, above all, avoiding any risk of solvent evaporation. It may therefore represent a valid alternative to the conventional methods currently used. • DESs enable micro-extraction and hydrolysis to be conducted efficiently. • The risk of evaporation and excessive concentration due to heating is prevented. • CE makes it possible to separate Ty and HTy quickly without using solvents. • Integrating these two approaches represents an innovative advance in food analysis. • The method aligns with the principles of green and white analytical chemistry.