Dispersive solid phase extraction combined with solidification of floating organic drop–liquid–liquid microextraction using in situ formation of deep eutectic solvent for extraction of phytosterols from edible oil samples

In this study, a dispersive solid phase extraction method was combined with solidification of floating organic drop–liquid–liquid microextraction based on in situ synthesis of deep eutectic solvent. It was used for the extraction of some phytosterols from edible oil samples. The extracted analytes were quantified by gas chromatography–mass spectrometry. In this procedure, the sample lipids are saponified with sodium hydroxide and then the analytes are adsorbed onto an octadecylsilane sorbent. After that the analytes are desorbed from the sorbent with ethanol as an elution solvent and the eluant is diluted with deionized water to obtain a homogenous solution. Then, a few amounts of choline chloride and n-butyric acid are dissolved in the solution and transferred into a water batch adjusted at 75 ⁰C for 5 min. During this period Choline chloride and n-butyric acid form a deep eutectic solvent (extraction solvent) dispersed in whole parts of the solution. The obtained cloudy solution is placed into an ice bath. The extraction solvent is collected and solidified on the top of the solution. Finally, it is removed and allows melted at room temperature and an aliquat of the solution is injected into the separation system. Validation of the method showed that limits of detection and quantification were in the ranges of 0.52–1.6 and 1.7–5.6 ng mL–1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 312 to 375 and 75–90%, respectively. The method had a proper percision with relative standard deviations less than ≤8.2% for intra– (n = 6) and inter–day (n = 6) precisions at a concentration of 15 ng mL–1 of each analyte. Finally the method was successfully used for determination of the analytes in some edible oil samples.