IL-USA-DLLME Method to Simultaneously Extract and Determine Four Phenylurea Herbicides in Water Samples

An ionic-liquid ultrasound-assisted dispersive liquid-liquid microextraction method (IL-USA-DLLME) was introduced to determine four phenylurea herbicides (i.e., isoproturon, monolinuron, linuron, and diuron) in water samples with high performance liquid chromatography (HPLC). The ionic liquid of 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIMPF6] was dispersed into the aqueous sample solution in fine droplets by ultrasound and was used as the extraction solvent; the phenylurea herbicides were concentrated into the ionic liquid phase. The extraction conditions, such as the volume of the extraction solvent, sonication and centrifugation time, ionic strength, and the emulsification-extraction temperature, were optimized. Under the optimized conditions, the linear correlation coefficient ranged from 0.9954 to 0.9969 for concentration levels of 2-100 μgL-1. The good recovery (68-100%) of target analytes was obtained from the water samples. The relative standard deviations (RSDs, n=6) ranged from 2.3-9.5%, and the limits of detection (LODs) for the herbicides were between 0.10 μgL-1 and 0.24 μgL-1. The applicability of the proposed method was evaluated by the extraction and determination of phenylurea herbicides from several natural water samples.