Water-based green deep eutectic solvent: Application in liquid-liquid microextraction of trace bisphenol A in edible oils

In this study, tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide (TBAB), and choline chloride (ChCl) were innovatively applied in the liquid-liquid microextraction (LLME) of bisphenol A (BPA) from edible oil by forming water-based deep eutectic solvent (WDES). The presence of water is not only used in the synthesis of WDES, but also modulates the viscosity of DES and improve its diffusion and mass transfer properties. Several crucial parameters affecting the extraction efficiency were examined, including the type and amount of WDES and the extraction time. The results indicated that TBAC-H₂O (molar ratio 1: 5) WDES exhibited the best extraction ability, the optimal extractant dosage was 100 μL and the extraction time was 3 min. Under the optimized experimental conditions, the proposed method showed a low detection limit (0.2 ng mL^-1), good linearity (R² = 0.997), precisions (RSDs ≤5.1 %) and was successfully employed to detect BPA in edible oil with excellent recoveries (90.6-102.6 %). The formation of the WDES was confirmed by ¹H NMR, differential scanning calorimetry (DSC). The extraction mechanism was explored through theoretical calculations and Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR) analysis. The results revealed that the separation of BPA by WDESs was primarily dominated by hydrogen bonds, and the hydrogen bond interaction between TBAC-BPA was stronger than that of TBAB-BPA and ChCl-BPA. This work provides a valuable reference for the determination of trace BPA in edible oils or similar samples in food safety monitoring and screening.