Ethylene glycol-based dispersive liquid-liquid microextraction of bisphenols in edible oil samples

This study compares, for the firt time, the use of three different ethylene glycol-based extractant solvents in dispersive liquid-liquid microextraction (DLLME) for the determination of four bisphenols (i.e., BPF, BPA, BPAP, and BPAF) in edible oils by liquid chromatography-diode array detector (LC-DAD). The extractants studied were: pure ethylene glycol (EG), a deep eutectic solvent or DES (i.e., chlorine chloride (ChCl) and EG, 1:2 M ratio), and a magnetic deep eutectic solvent or MDES (i.e., ChCl, EG and iron chloride hexahydrate (FeCl₃·6H₂O), 1:4:1 M ratio). Two-step multivariate optimization was performed for EG and DES, while one-step optimization was applied for MDES. The optimal conditions for EG and DES were similar with 50 μL of extractant volume and 1 min of extraction time, except for centrifugation conditions which were 3 min and 370 g-force and 3 min and 832 g-force for EG and DES, respectively. The use of MDES required a higher volume of extractant (i.e., 75 μL) and a longer extraction time (i.e., 4.5 min). The most satisfactory results were achieved using EG, exhibiting adequate linearity (r ≥ 0.990), lower limits of detection (LODs) (i.e., 0.3 μg kg^-1), excellent repeatability (RSD ≤3.2 %) for all analytes and non-significant matrix effects in real edible oil samples (i.e., relative recovery values: 71-121 %). Therefore, pure ethylene glycol is the most suitable extractant when compared to ethylene glycol-based eutectic mixtures and their magnetic variant. This finding underscores the necessity for further exploration of the pure constituents of mixtures as potential extractants.