Development of a liquid-phase microextraction based on the freezing of a deep eutectic solvent followed by HPLC-UV for sensitive determination of common pesticides in environmental water samples

In this research, a new extraction method based on liquid-phase microextraction and the freezing of deep eutectic solvent (LPME-FDES) has been developed for the determination of common pesticides in water samples prior to their analysis by high performance liquid chromatography-ultraviolet detection (HPLC-UV). In this method, a green solvent consisting of 1-octyl-3-methylimidazolium chloride and 1-undecanol was used as an extraction solvent, yielding the advantages of material stability, low density, and a suitable freezing point near room temperature. Under the optimum conditions, enrichment factors and extraction recoveries are in the range of 150–180 and 75–90%, respectively. The calibration graphs are linear in the range of 0.2–500 μg L(−1) and limit of detections (LODs) are in the range of 0.05–0.50 μg L(−1). Relative standard deviation (RSD) values for intra-day and inter-day of the method based on seven replicate measurements of 200 μg L(−1) of diazinon and endosulfan, 100 μg L(−1) of phosalone, 50.0 μg L(−1) of atrazine, desethylatrazine and deisopropylatrazine in water were in the range of 1.3–2.5% and 2.2–3.6%, respectively. The relative recoveries of well, tap and river water samples which have been spiked with different levels of target pesticides are 97–106, 90–108 and 95–107%, respectively. The extraction methodology is simple, rapid, cheap and green since small amounts of non-toxic solvents are necessary.