Acid-base-governed deep eutectic solvent-based microextraction combined with magnetic solid-phase extraction for...

A sensitive method based on the use of green deep eutectic solvents (DESs) was designed for the determination of bisphenol-A, bisphenol-AF, tetrabromobisphenol-A and 4-tert.-octylphenol followed by HPLC. This method takes advantage of magnetic solid-phase extraction purification and acid-base induced DES liquid-liquid microextraction. The Mg(II)-Al(III) layered double hydroxide-coated magnetic nanoparticles were selected to purify samples. The DESs were systematically prepared by a range of medium-chain saturated fatty acids (C₈-C₁₂) and D,L-menthol. The melting point and the extraction efficiency of phenolic compounds were adjusted by changing the carbon chain length of fatty acid in suitable proportions. Acid-base induction significantly improves the extraction efficiency. The method has lower limits of detection ranging from 6 to 11 ng L^-1, good linearity (0.05-500 μg L^-1) and high enrichment factors (86-91). The method was successfully applied for the determination of four phenolic compounds in beverage samples. The recoveries ranged from 84.4 to 101.3%. Graphical abstract Schematic representation of the extraction of four phenolic compounds by medium chain (C₈-C₁₂) fatty acid-based eutectic solvent (DES) through acid-base-induction.