Hydrophobic liquid-polymer-based deep eutectic solvent for extraction and multi-residue analysis of pesticides in water samples

Abstract

Three new polymer-based deep eutectic solvents (DES), including [polyethylene glycol]:[thymol], [polyacrylic acid]:[menthol], and [polyacrylic acid]:[thymol], and were prepared and examined as extraction solvent in dispersive liquid–liquid microextraction of 16 pesticides for the first time. The extracted analytes were quantitatively analyzed by the GC-µECD technique. Among these DESs, [polyethylene glycol]:[thymol] in the molar ratio of 2:1 showed the highest extraction efficiency. Another new DES, [ethylene glycol]:[thymol], was also prepared and tested. Comparison of the efficiency of polymeric ([PEG]:[Thy]) and non-polymeric ([EG]:[Thy]) DESs indicated that the extraction efficiencies obtained by [PEG]:[Thy] DES were much higher (2 to 16 times) than those of [EG]:[Thy] DES. The chemical structure of [PEG]:[Thy] DES was characterized by ATR-FTIR spectroscopy. Moreover, its hydrophobicity and effect on the pH of aqueous phase was studied. The influence of significant parameters such as extraction solvent (type and volume), disperser solvent (type and volume), pH of the sample solution, and ionic strength was investigated. Under the optimum conditions, the limits of detection and quantification were obtained in the ranges 0.001–0.02 and 0.004–0.070 µg L-1, respectively. The linear range for most pesticides was in the range of 0.004–100 µg L-1 and for aldrin and dieldrin was 0.011–50 µg L-1. The enrichment factors were between 14 and 70. The method was applied to detect pesticide residues in environmental water samples, and the relative recoveries were found between 60.5 and 105.0% with RSD%less than10.5.