Ionic Liquids Emulsion Phase Liquid-Liquid Microextraction Combined with High Performance Liquid Chromatography for Determination of Sulfonylurea Herbicides in Soy Milk

A green and efficient vortex-ultrasonic co-emulsification combined with ionic liquids emulsion phase liquid-liquid microextraction method was developed for extraction and enrichment of six sulfonylurea herbicides such as thifensulfuron,metsulfuron,sulfensulfuron,chlorsulfuron,benzsulfuron and pyrimisulfuron in soybean milk. High performance liquid chromatography was used for the separation and determination of target analytes. In the proposed method,ionic liquid was used as an extractant and modified montmorillonite was used as solid phase adsorbent. The synergism of vortex and ultrasound promoted the emulsification of the ionic liquid and increased the contact area between the ionic liquid and the target analyte. After dispersive liquid-liquid microextraction,the ionic liquids combined with the target analytes were adsorbed by modified montmorillonite. Subsequently,the modified montmorillonite was separated from sample solution through centrifugation. The quantitative acetonitrile solution was used to desorb the target analytes from modified montmorillonite. The desorption solution was used for chromatographic analysis after passing through the 0.22 μm filter membrane. The experimental results showed that good linearities with the correlation coefficients higher than 0.9990 were obtained under the optimum conditions. The limits of detection(LODs)and quantification(LOQs)were in the range of 1.60~3.15 and 5.34~10.12 μg/L,respectively. The intra-day precision and inter-day precision of each target analyte were 1.31%~5.07% and 1.12%~6.63%,respectively. The spiked recovery was between 81.55%~116.44% and the relative standard deviation was between 0.05%~8.91%,respectively. In the proposed method,ionic liquid was used as extraction solvent instead of organic solvent. This method combined vortex and ultrasound-assisted dispersive liquid-liquid microextraction with dispersive solid-phase extraction based on modified montmorillonite,and integrated sample extraction,separation,and purification into one step. The present method has the advantages of high extraction efficiency,simple operation and low cost,and can be used for the separation and detection of sulfonylurea herbicides in commercially available packaged soy milk.