Organic solvent-free elevated temperature liquid–liquid extraction combined with a new switchable deep eutectic solvent-based dispersive liquid–liquid microextraction of three phenolic antioxidants from oil samples

An organic solvent-free extraction procedure using elevated temperature liquid–liquid extraction/ dispersive liquid–liquid microextraction based on deep eutectic solvent has been performed for the extraction of three synthetic phenolic antioxidants from oil samples. In the developed approach, firstly the antioxidants were extracted into an aqueous alkaline solution in an elevated temperature. Then, a few microliters of deep eutectic solvent formed from tetrabutylammonium chloride and hydroquinone was dissolved in the alkaline solution and a homogenous solution was obtained. In the following it was dispersed into an acidic solution. In this step, an acid–base reaction was occurred and the analytes were migrated into the fine droplets of the deep eutectic solvent. The extracted analytes were determined by gas chromatography-flame ionization detector. Validation data showed that low limits of detection (0.13–0.42 ng/mL) and quantification (0.36–1.41 ng/mL), high extraction recovery (74–89%) and enrichment factor (370–445), and good precision (relative standard deviation ≤ 7.4%) can be obtained by the developed method. Finally, the method was used for quantification of the antioxidants in several edible oil samples.