Application Of Ionic Liquid-based Dispersion Liquid-liquid Micro-extraction In Pesticide Residue Analysis And Detection

With the large-scale use of pesticides worldwide,the problem of pesticide residues cannot be ignored.Pesticide residues have always been a hot topic in food safety,and it is especially important to determine the amount of pesticide residues in different foods.Dispersive liquid-liquid microextraction?DLLME?is a new green and environmentally friendly sample pretreatment technology.Compared with other methods,the dispersive liquid-liquid microextraction has incomparable advantages in the process of enrichment pesticide residues,and is widely used in the pre-concentration of pesticide residues in different foods.In this paper,dispersive liquid-liquid microextraction about pyrethroid pesticides and neonicotinoid insecticides has been developed,respectively.The matrix effect in the detection of neonicotinoid insecticides was also studied.The main research include the following aspects:The extraction performances of conventional,temperature-controlled?TC?and ultrasoundassisted?UA?dispersive liquid-liquid microextraction for pyrethroid insecticides were compared.Temperature-controlled?TC?dispersive liquid-liquid microextraction was found to provide the best extraction efficiency.Various parameters that affect extraction efficiency in the extraction process were optimized,including type and amout of extraction and disperser solvent,ionic strength,pH value,temperature,water bath time and centrifugal time.A temperature-controlled dispersive liquid-liquid microextraction?TC-DLLME?combined with ultra-high performance liquid chromatography?UPLC?was successfully established to pre-concentrate and detect six pyrethroid insecticides in fruit juice samples.Under optimized conditions,good extraction efficiency was achieved by using hydrophobic ionic liquid3-methyl-1-octylimidazoliumhexafluorophosphate?[C₈MIM][PF₆]?as microextraction solvent.The enrichment factor of developed methods ranged from 60to 153,and the limit of detections?LOD?ranged from 0.30 to 0.80?g L^-1.Good recoveries?6.2–102.5%?and RSD?1.1–6.4%?were obtained by analysis real juice samples spiked with three concentrations of 10,50 and 100?g L^-1.An efficient in-situ ionic liquid dispersive liquid-liquid microextraction followed by ultra-performance liquid chromatography was developed to determine four neonicotinoid insecticides in wild and commercial honey samples.In this method,a hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate formed by in-situ reaction between Potassium hexafluorophosphate and1-Butyl-3-methylimidazolium bromide in sample solution was used as the extraction solvent.In comparison with traditional dispersive liquid-liquid microextraction method,the developed method required no dispersive solvent.To achieve high extraction efficiency and enrichment factor,the effects of various experimental parameters were studied in detail.Under the optimized conditions,the limits of detection and quantification were in the ranges of 0.30–0.62 and 1.20–2.50?g L^-1,respectively.The method showed high enrichment factors,74–115 with the recoveries between 81.0%and 103.4%.The proposed method was finally applied to different wild and commercial honey samples.The effects of ionic liquids on the liquid chromatography and mass spectrometry signals of neonicotinoid insecticides were investigated.The results showed that the ionic liquid had a matrix depression effect in the mass spectrometry detection process of neonicotinoid insecticides,and with the ionic liquid increased,the matrix inhibition effect was more obvious.Dilution and back-extraction methods can be used to reduce the proportion of ionic liquids in the system and improve the mass spectrometry response of neonicotinoid insecticides.