Functionalized Ionic Liquid/Ionic Liquid Dispersive Liquid-Liquid Microextraction for Determination of Phenoxy Acid Herbicides in Water Samples

Functionalized ionic liquid/ionic liquid ultrasound-assisted dispersive liquid-liquid microextraction (FIL/IL-DLLME) was developed for the determination of four phenoxy herbicides in water samples. The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C(6)HyMIMTf(2)N], dispersed entirely into sample solution with the help of hydrophilic [C4MIMBF4]. The introduction of ion-pairing agent ([LiTf2N]) was beneficial to the improvement of the extraction efficiency. The main parameters relevant to this method were investigated and optimized as follows: 100 mu L of [C(6)HyMIMTf(2)N] and 100 mu L of [C4MIMBF4] were used as extraction solvent and dispersion, the ultrasonic time was fixed for 2 min at 30 degrees C, 6% [LiTf2N] was added and the pH of sample solution was adjusted to 2. Under the optimum conditions, the linear correlation coefficient ranged from 0.9953 to 0.9996 for concentration levels of 5-500 mu g/L and the limits of detection (LODs) for the herbicides were between 0.05 mu g/L and 0.2 mu g/L. The recoveries (70.2%-107.5%) of the target analytes were obtained in tap water, river water and field water at two spiked levels of 10 and 20 mu g/L, the relative standard deviations (RSDs, n = 6) were less than 10%, The results indicated that the proposed method was effective for the determination of phenoxy acid herbicides in water samples.