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 and limit of detections (LODs) are in the range of 0.05-0.50 μg L. Relative standard deviation (RSD) values for intra-day and inter-day of the method based on seven replicate measurements of 200 μg L of diazinon and endosulfan, 100 μg L of phosalone, 50.0 μg L 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.