Ionic Liquid-based Liquid-liquid Microextraction Of Herbicides In Soy Milk

Soybean originated in China,and its processing and consumption history has been thousands of years.As a deep-processed product of soybeans,packaged soy milk is a healthy beverage that just emerged in recent years.It contains a large amount of high-quality plant protein,soy isoflavones,vitamins and lecithin,which can reduce human cholesterol,prevent diabetes and hypertension.It is known as"green milk"because of its effects on coronary heart disease.However,a variety of herbicides are used during the planting process of soybeans to control the growth of weeds.Most of the herbicides have a long degradation cycle and are easy to remain in environmental water,soil and atmosphere.It can be absorbed by soybeans easily.After these contaminated soybeans are further processed,they will have a potential impact on the quality of packaged soy milk.Thereby,it will threaten the health of consumers.In chapter one,the structures,properties and detection methods of triazine,phenylurea and sulfonylurea herbicides were introduced.And the types,development and application researches of ionic liquids were introduced in detail as well.In chapter two,a efficient,fast,and green ionic liquid-liquid liquid microextraction based on solid phase clean-up,and temperature controlled method was established for the extraction of six triazine and phenylurea herbicides(monuron,chlorotoluron,atrazine,monolinuron,propazine and prometryn)from soy product samples.In this study,the impurities such as protein and fat in the samples were removed by solid phase clean-up.Hydrophobic low-density solidified ionic liquid([P_{4 4 4 12}]BF₄)was used as extraction solvent,which was dispersed into the samples solution and formed fine droplets with the help of water-bath and vortex method.Finally,in order to achieve the purpose of extracting the analytes,the solidified ionic liquid enriched with the targets was separated from the sample solution by changing temperature.Some extraction conditions,such as type and amount of ionic liquids,type and amount of absorbents,ionic strength of sample solution,vortex time and p H value were investigated.The experimental results showed that the target analytes exhibited good correlation coefficients(r?0.9994)in the linear range.The limits of detection(LODs)and quantification(LOQs)were in the range of 0.52?2.6?g/L and 1.7?8.6?g/L,respectively.The spiked recoveries were in the range of 82.6%?118.2%.The proposed method demonstrated simplicity,high efficiency,green and low reagent consumption,which could be successfully applied to the extraaction of triazine and phenylurea herbicide residues in soy product samples.In chapter three,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 in soy milk,including thifensulfuron,metsulfuron,sulfensulfuron,chlorsulfuron,benzsulfuron and pyrimisulfuron.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 the 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?m 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?3.04?g/L and 5.34?10.12?g/L,respectively.The intra-day precision and inter-day precision of each target analytes were 1.31-5.07%and 1.12%?6.63%,respectively.The spiked recoveries were between 81.55%and 116.44%,and the relative standard deviation was0.05%?8.91%.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.In chapter four,a new hydrophobic eutectic solvent(DES)composed of tetrabutylammonium and chloride-perfluorooctanol was used as the extractant.And the vortex assisted liquid-liquid microextraction was combined with high performance liquid chromatography was established to analyse seven kinds of triazine and phenylurea herbicides in vegetable protein liquid samples.In this method,10 different hydrophobic DESs were prepared tetrabutylammonium-chloride was used as the hydrogen bond acceptor,and perfluoroalcohols or acids with different alkyl chain lengths were used as hydrogen bond donors.After that,the extraction performance was investigated,and DES composed of tetrabutylammonium and chloride-perfluorooctanol was finally selected for the optimization of conditions,including the type of DESs,vortex time,amount of sodium chloride and p H value.The results showed that the target analytes exhibited good correlation coefficients(r?0.9993)in the linear range.The limits of detection(LODs)and quantification(LOQs)were in the range of 0.15?1.00?g/L and 0.51?3.33?g/L,respectively.The spiked recoveries were in the range of 82.11%?117.79%.In this study,it was found that DES using perfluoroalcohols as hydrogen bond donors had better extraction performance than that using alcohols with the same alkyl chain length as hydrogen bond donors.And with the increase of the perfluoroalcohol alkyl chain,the extraction performance of DES for triazine herbicides gradually increased,but its extraction performance for phenylurea herbicides decreased slightly.In conclution,the method established in this research has the advantages of low reagent consumption,simple operation and efficient extraction.It can be used in commercial high-protein liquids Detection of triazine and phenylurea herbicides in plant samples.