Study Of Ionic Liquid-Dispersive Liquid-Liquid Microextraction For The Determination Of Fungicide Residues

In 2006, Rezaee et al. developed a novel liquid-liquid microextraction method, dispersive liquid-liquid microextraction (DLLME). With the feature of sampling, extraction and enrichment at the same time, the new method has been widely recognized due to its simplicity, speediness, low cost and high enrichment. Unfortunately, some environmentally-unfriendly organic solvents containing halogen, such as chloroform and carbon tetrachlorideas were usually selected as extaction solvents in the traditional DLLME. Ionic liquid (IL), also named room-temperature ionic liquid, has the unique properties, such as negligible vapor pressure, nonflammability and good thermal. Instead of the traditional organic solvents as extraction solvents, IL is considered as a kind of green solvent.In the paper, the characteristics of IL, liquid-phase microextraction method and the modes of IL-DLLME were introduced first. The recent applications of IL-DLLME in the determination of pesticides residue in food and environment were emphatically reviewed. Then, temperature-controlled and vortex-assisted approaches were applied in IL-DLLME for the determination of pesticide residues in fruit juices, respectively. Finally, IL-DLLME coupled with QuEChERS was established to detect pesticide residues in the solid matrix. On the basis of that, three new detection methods were optimized, established and applied to real samples with the satisfactory results. The details and results are as follows:(1) A novel method was developed for the determination of seven fungicide (azoxystrobin, fludioxonil, triazolone, fenarimol, cyprodinil, prochloraz, diniconazole) residues in fruit juices using temperature-controlled IL-DLLME coupled to high performance liquid chromatography with photodiode array (HPLC-PDA). Parameters affecting the extraction performance such as the kind and volume of extraction and dispersive solvents, temperature, extraction time and centrifuging time were studied and optimized. Under the optimized conditions, the enrichment factors ranged from 64 to 101. The recoveries obtained by IL-DLLME spiked at three spiked levels (0.02,0.05 and 0.1 mg/L) into five fruit juices including apple, pear, grape, peach and orange juices, ranged from 70.0% to 116.2% with the relative standard deviations (RSDs) less than 9.8%. The limits of detection (LODs) were in the range of 4.3-13.0 μg/L. The results have met requirement of fungicide residues determination in various fruit juices.(2) A microextraction procedure based on vortex-assisted IL-DLLME coupled with HPLC-PDA for the preconcentration of six fungicides (triazolone, triadimenol, epoxiconazole, flusilazole, tebuconazole and diniconazole) has been developed. Parameters affected such as the kind and volume of extraction and dispersive solvents, extraction time and centrifugation time were optimized. Under the optimum extraction conditions, the enrichment factors ranged from 29 to 40. Three fortified levels at 0.05,0.1 and 0.5 mg/L were spiked into three fruit juices including apple, peach and orange juices. The recoveries ranged from 71.0%-100.7% with the RSDs between 1.4%-11.8% and the LODs were in the range of 0.4-6.7 μg/L. The results have met requirement of fungicide residues determination in various fruit juices.(3) A new, simple and rapid method named QuEChERS (quick, easy, cheap, effective, rugged, and safe) based on IL-DLLME coupled with HPLC-PDA for the determination of six fungicides (triazolone, triadimenol, epoxiconazole, flusilazole, tebuconazole and diniconazole) in fruits has been developed. Acetonitrile extract was obtained from QuEChERS and chose as dispersive solvent, DLLME method was used to purify and concentrate the target objects. After the single factor experiment, 1-Hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) was selected as extraction solvents. Other experimental parameters affected the extraction efficiency, such as the volume of extraction and dispersive solvents, extraction time and centrifugation time, were also optimized. Thereafter, a response surface method was used to optimize the significant variables affecting the extraction and built the quadratic model. Under the optimum extraction conditions, the LODs were in the range of 1.0-16.8μg/L. Three fortified levels at 0.2,0.5 and 1.0 mg/L were spiked into three real fruit samples including pear, apple and Citrus maxima. The recoveries ranged from 63.8%-119.1% with the RSDs between 1.1%-12.6%, the results have met requirement of fungicide residues determination in various fruits.