Behaviour of deep eutectic solvent based on terpenoid and long-chain alcohol during dispersive liquid-liquid microextraction: Determination of zearalenone in cereal samples

In recent years, the numerous articles have been devoted to the application of hydrophobic deep eutectic solvents based on natural terpenoids and long-chain alcohols as extraction solvents in dispersive liquid–liquid microextraction. Typically, the microextraction procedure assumes injection of deep eutectic solvent solution in a dispersive solvent (polar organic solvent) into aqueous phase. The decomposition of deep eutectic solvent in the extraction system can be observed due to the partial dissolution of its precursors in aqueous phase containing the dispersive solvent. In this work, the process of dispersive liquid–liquid microextraction with the use of deep eutectic solvents based on terpenoids and long-chain alcohols was investigated. The extraction systems were applied to the mycotoxin (zearalenone) determination in cereal samples as a model analytical task. The solvent based on dl-menthol and 1-hexanol provided high extraction recovery (93 ± 4) % and satisfactory enrichment factor (15.8 ± 0.7). The limit of detection evaluated from the signal-to-noise ratio was 2 μg/kg. The stability of the deep eutectic solvent in acetonitrile–water mixture was studied using gas chromatography-flame ionization detection and Karl Fisher method. It was shown that the formation of terpenoid-rich phase (60 % (m/m) of menthol) took place during the dispersive liquid–liquid microextraction, and the deep eutectic solvent based on terpenoid and long-chain alcohol cannot be considered as the extraction solvent.