A hydroxyl functionalized ionic liquid-based ultrasound-assisted surfactant-enhanced emulsification microextraction for the determination of herbicides in water samples

Abstract

This paper describes a hydroxyl functionalized ionic liquid (FIL), 1-hydroxyl hexyl-3-methylimidazoliumbis[(trifluoromethyl)sulfonyl] imide [HHyMIMTf₂N] as an extraction solvent for the extraction and preconcentration of seven herbicides from water samples by ultrasound-assisted surfactant-enhanced emulsification microextraction combined with high-performance liquid chromatography. The FIL was dispersed into the aqueous samples with the assistance of ultrasound. Moreover, the addition of a surfactant as an emulsifier enhanced the speed of the mass-transfer from aqueous samples to the FIL, and it also caused the FIL to not stick to the centrifuge tube wall. The effects of experimental parameters, such as FIL volume, the type and concentration of surfactant, ultrasound extraction and centrifugation time, sample pH and salt addition were investigated and optimized for this method. Under the optimized conditions, the linear correlation coefficient ranged from 0.9904 to 0.9998 for the concentration levels of 0.2–400 μg L⁻¹. Good recoveries (66.7–102.3%) of the target analytes were obtained from the water samples. The relative standard deviations (RSDs, n = 6) ranged from 1.5–10.3%, and the limit of detection (LOD) for the herbicides were between 0.005 μg L⁻¹ and 0.084 μg L⁻¹. The applicability of the proposed method was evaluated based on the extraction and determination of seven herbicides from several real water samples.