A green ternary polymeric deep eutectic solvent used in dispersive liquid-liquid microextraction technique for isolation of multiclass pesticides in fruit juice samples

A green dispersive liquid-liquid microextraction procedure based on a ternary polymeric hydrophobic deep eutectic solvent (DES) for monitoring multi-residue pesticides in eleven various fruit juices was developed before Gas Chromatography coupled with micro-Electron Capture Detector (GC-µECD). Six ternary polyethylene glycol (PEG)-based DESs were synthesized, and their extraction efficiency was evaluated. Among these DESs, [thymol]:[polyethylene glycol]:[acetic acid] (1:2:2) showed the highest signal intensity. Moreover, three other binary PEG-based DESs and a non-polymeric DES were also synthesized and compared to the previous DES. The extraction yield obtained by polymeric one was much higher than non-polymeric. Some significant parameters influencing the extraction efficiency including the type and volume of DES (extraction solvent), disperser solvent, pH, and ionic strength were optimized as follows: [Thy]:[PEG]:[HOAc] (1:2:2), 400 µL of DES, ACN as disperser solvent (700 µL), no pH adjustment and no salt addition. The DES was characterized by ATR-FTIR and (1H and 13C) NMR spectroscopy. Under the optimized conditions, the limits of quantification, the linear ranges and extraction recovery were 0.009–0.182 µgL−1 0.003–50.0 µgL−1, 67.9–108.4%, respectively. The enrichment factors were 11–170. Intra-day and inter-day RSDs% were 1.4–5.1% and 2.0–12.6%, respectively. This method was applied for analyzing pesticide residues in eleven fruit juices, and the pre-concentration factor and relative extraction recoveries were in the range of 12–169 and 71–108%, respectively.