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[Display omitted] • An acid–induced dispersive liquid–liquid microextraction is developed. • Analytes are extracted by in situ formation of deep eutectic solvents with formed fatty acids. • The method is successfully used for detection of bisphenol A and alkylphenols. • The method is simple, rapid, sensitive, low cost, and environmentally friendly. • The new method expands the application pathway and scope of deep eutectic solvents. This study describes the development of an acid induced dispersive liquid–liquid microextraction method based on the in situ formation of hydrophobic deep eutectic solvents for the extraction of bisphenol A and alkylphenols from environmental water and beverage samples. Hydrochloric acid altered the hydrophilic-hydrophobic state of fatty acid salts to obtain hydrophobic fatty acids, which formed hydrophobic deep eutectic solvents with analytes in situ to extract the analytes. Under optimized conditions, the limits of detection and limits of quantitation were 0.03–0.1 μg L-1 and 0.12–0.3 μg L-1, the intraday and interday relative standard deviations were less than 3.9 %, and the enrichment factor was 29–32. The recoveries of bisphenol A and alkylphenols were 95.9–104.9 % and 86.9–105.0 %, respectively. The extraction process used only hydrochloric acid and fatty acid salts, and the extraction process required less than 1 min. This method has the advantages of simplicity, speed, low cost and environmental friendliness. [ABSTRACT FROM AUTHOR]

• One-step derivatization and TC-VA-LLME-SFDES method was developed. • Hydrophobic DESs were used as both reducing agent and extraction solvent. • Only 2 min was needed for derivatization and extraction process. • The method was applied for analysis of total Fe in water and food samples. • The method opened up the application of solid DESs in LLME technique. In our work, hydrophobic thymol-based deep eutectic solvents (DESs) with strong reducibility, a lower density than water, and a slightly higher melting point than room temperature were synthesized. Based on these solid DESs, one-step derivatization and temperature-controlled vortex-assisted liquid-liquid microextraction based on the solidification of a floating DES (TC-VA-LLME-SFDES) via UV–Vis spectrophotometry for the rapid determination of total iron was developed. The derivatization and TC-VA-LLME were carried out simultaneously by the addition of DES as both the reducing agent and extraction solvent. After optimization, the calibration curve (5–250 μg L−1, R2 = 0.9982), limit of detection (1.5 μg L−1), limit of quantitation (5.0 μg L−1), precision (≤4.0%) and enrichment factor (92) was obtained. This method was applied for the determination of total iron in water and food samples with satisfactory recoveries (85.4–106.2%). One-step derivatization and TC-VA-LLME only required 2 min. Furthermore, this method opened up the application of solid DESs in liquid–liquid microextraction. [ABSTRACT FROM AUTHOR]

• DESs with low viscosity, density and melting point near room temperature were designed and used. • A centrifugation-free AA-LLME-SFDES method was developed. • Placket-burman design and central composite design were used for the method optimization. • This method was used for simultaneous analysis of bisphenols and PAHs in 15 tea infusions samples. • This method may be developed as a fully automated AA-LLME method. Deep eutectic solvents (DESs) are a new class of green "designer solvent"; its physicochemical properties can be easily tuned by adjusting DES′ constituents, chemical ratio and water content. In this study, three hydrophobic DESs with low viscosity, low density, and melting points close to room temperature were designed and synthesized. Based on these DESs, an air-assisted liquid–liquid microextraction technique was developed based on the solidification of floating DESs for the simultaneous determination of bisphenols and polycyclic aromatic hydrocarbons (PAHs) via HPLC. The microextraction parameters were optimized via the Plackett-Burman design and response surface methodologies. The method shows satisfactory linearity (R2 ≥ 0.9928), a low limit of detection (0.16–0.75 μg L−1) and satisfactory precision (≤2.3%), and was successfully applied for the simultaneous determination of bisphenols and PAHs from tea infusions with satisfactory recoveries (82.0–116.6%). This method is simple, rapid, economical, environmentally compatible, dispersive solvent-frees and centrifugation-free, and has promising applications in food safety. [ABSTRACT FROM AUTHOR]

• A method for separating FWA52 from foods by in situ formation of hydrophobic DES was established. • High concentration of inorganic salts and organic compounds had no effect on the separation process. • This strategy could be used directly to extract FWA52 at ultra-trace level (0.05 μg/L) • The established method was simple, rapid and environment-friendly. Fluorescent brightener 52 (FWA52) is a coumarin-based compound, and it is difficult to degrade owing to its high chemical stability. Up to now, several methods have been developed to extract and determine FWAs, but toxic, volatile and harmful organic solvents are often used. In this paper, a novel method for the extraction and analysis of FWA52 is proposed for the first time by in situ formation of hydrophobic deep eutectic solvent (DES) with parabens in aqueous solution. The effects of paraben structure, solution pH, system temperature, extractant dosage and initial FWA52 concentration on the extraction recovery were investigated systematically. It is shown that FWA52 can be extracted by 2-ethylhexyl 4-hydroxybenzoate at ultra-trace level (0.05 μg/L FWA52) at room temperature without using harmful organic solvents, and various coexisting inorganic ions and organic compounds have little effect on the extraction efficiency. Based on these results, a novel and simple strategy is developed for the accurate determination of FWA52 in water. It is found that under the optimal experimental conditions, the linear range of this method is 0.20~25 μg/L (R2 = 0.9995), and the detection limit and the quantity limit are 0.045 μg/L and 0.20 μg/L respectively. This method has been successfully applied for the determination of FWA52 in actual food samples and food contact materials, such as noodles, fish balls, mushroom and paper cups, with a recovery from 82 to 113% and a relative standard deviation (RSD) from 4.7 to 9.9%. In addition, the separation mechanism was investigated by FT-IR and 1H NMR, and was discussed from strong hydrogen bonding between FWA52 and 2-ethylhexyl 4-hydroxybenzoate and the formation of corresponding DES. [ABSTRACT FROM AUTHOR]