Development of a sustainable dispersive liquid–liquid microextraction based on novel hydrophobic and hydrophilic natural deep eutectic solvents for the analysis of multiclass pesticides in water

A novel green dispersive liquid–liquid microextraction (DLLME) technique based on two new natural deep eutectic solvents (NaDESs) was developed and applied to the extraction of multiclass pesticides in different environmental waters. A hydrophobic NaDES based on monoterpene thymol and myristyl alcohol was prepared in 2:1 M ratio and used as an extraction phase. Additionally, a ternary hydrophilic NaDES composed of alanine, kojic acid, and water in a 1:2:5 M ratio was prepared and applied as disperser solvent. The NaDESs were characterized by ATR-FTIR spectroscopy, NMR spectroscopy, and octanol–water partition coefficient (Kow). The analyses were performed by GC-µECD. The effect of significant parameters influencing extraction efficiency was investigated through a one-at-a-times strategy. The optimized method was validated by matrix-matched calibration, repeatability, and recovery. The method was linear in the concentration ranges of 0.003–100 μg L−1 for 14 pesticides and 0.013–50 μg L−1 for two pesticides with the determination coefficients > 0.9712. The accuracy was assessed by recovery evaluation at the spike levels of 10 and 20 µg/L, in the range of 63.7–104.5%, with RSD ≤ 9.7%. The method was applied to the analysis of five environmental water samples, and various pesticide residues were detected in river water and groundwater samples in the concentrations range of 0.36–1.10 μg L−1. The greenness of the procedure was assessed using the Analytical Eco-Scale. This paper represents the first application of these novel natural deep eutectic solvents in DLLME and, also the first time, for the analysis of multiclass pesticides in water samples.