Supramolecular deep eutectic solvents based ferrofluid for vortex-assisted liquid-liquid microextraction of alkylphenols from water and beverage samples

A novel supramolecular deep eutectic solvent based ferrofluid for vortex-assisted liquid-liquid microextraction (SUPRADES-FF-VA-LLME) method was developed firstly for extraction of Alkylphenols (APs) from water and beverage samples. In this method, the SUPRADES composed of hydroxyethyl-β-cyclodextrin, thymol and caprylic acid was firstly designed, synthesized and then used as carrier liquid for ferrofluid. The influencing parameters were screened by a plackett-burman design and optimized by a central composite design. Under optimal conditions, the linear range of 4-heptylphenol, 4-octylphenol and 4-nonylphenol was 0.3–400, 0.2–400 and 5–400 μg L −1 , respectively, with R 2  ≥ 0.9990. And the limit of detection and the quantification of this method were 0.05–1.5 μg L −1 and 0.2–5 μg L −1 , respectively. Both intra-day and inter-day precision ( n  = 5) were ≤2.1 %, and the enrichment factor were 22–24. After microextraction, phase separation was quickly completed with the help of an external magnet, without the need of centrifugation equipment, greatly simplifying the operation steps and shortening the extraction time (∼2 min). Additionally, due to the introduction of hydroxyethyl-β-cyclodextrin, the encapsulation effect between its hydrophobic cavity and APs significantly enhances its molecular recognition ability, the method modification resulting in 19–29 % increase in extraction efficiency. Extraction mechanism was also studied by density functional theory. Combined with high performance liquid chromatography-fluorescence, this method was used for determination of APs in environmental water and beverages with spiked recovery of 98.4–102.4 %. The SUPRADES-FF-VA-LLME provides a new technique for the selective separation of pollutants, which is expected to be widely used in the field of food analysis and environmental monitoring.