Study On The Ionic Liquid Microextraction Of Naphthoquinones And Phenylurea Herbicides

For many years,a simple,efficient and green analysis method was pursued.However,in many cases,there are many impurities in samples.So,it is necessary to eliminate the interference of these coexisting components before instrumental analysis.In this way,different sample pretreatment methods were developed for the separation and purification of food samples,environmental samples,biological samples and various Chinese herbal medicines.Traditional sample pretreatment methods,including soxhlet extraction,chromatography,distillation and adsorption,have been widely used in various fields.However,the disadvantages of these methods are time-consuming,it is difficult to automate and a large number of organic solvents was used.The development of simple,miniature,green,highly selective and automated sample pretreatment technology is the future trend of analysis and detection.In this paper,ionic liquid was used as extraction solvent.With the help of ultrasound or microwave,ionic liquid microextraction was used as the sample pretreatment method and high performance liquid chromatography-diode array detector was used as separation and determination.The naphthoquinones in Arnebia euchroma?Royle?Johnst.and the phenylurea pesticides in food were analyzed and detected.The main contents of this paper are as follows:In Chapter 1,the structure and properties of naphthoquinones and phenylurea herbicides were introduced,and the development,application and research progress of ionic liquids were summarized.In Chapter 2,a simple,rapid and green microwave-assisted ionic liquid microextraction combined with high performance liquid chromatography was developed for the determination of three naphthoquinones in Arnebia euchroma?Royle?Johnst.,including shikonin,acetylshikonin and?,?'-dimethylacrylshikonin.A series of factors affecting the extraction yields were optimized,including size of sample particle,amount of sample,type of ionic liquid,volume of ionic liquid,microwave power and microwave time were evaluated.The results showed that good linear relationship were obtained?r>0.9999?.The LODs and LOQs were 5.0¹9.2 ng mL^-11 and 16.7⁶3.9 ng mL^-1,respectively.The recovery of spiked samples was 76.95%⁹3.55%.The precision of intra-day and inter-day were lower than 3.14%and 8.53%,respectively.Microwave extraction has the advantages of uniform heating,high thermal efficiency,low solvent consumption,energy saving and environmental protection.Compared with traditional extraction methods,microwave-assisted ionic liquid microextraction has obvious advantages in solvent amount,extraction time and other aspects.It can be used for the extraction and determination of naphthoquinone compounds in Arnebia euchroma?Royle?Johnst..In Chapter 3,five kinds of phenylurea herbicides?monuron,diuron,chlortoluron,monolinuro and isoproturon?in eight kinds of vegetable samples were analyzed and detected by solidified sedimentary ionic liquid-based ultrasonic assisted dispersive liquid liquid microextraction method.In this study,the hydrophilic ionic liquid[P₄₄₄₈]Br was used as the extraction solvent,which greatly increased the contact area and interaction between the target analytes and ionic liquid.The structure and water solubility of the ionic liquid were changed through in-situ reaction between[P₄₄₄₈]Br and the ion pair reagent NH₄PF₆.The hydrophobic ionic liquid[P₄₄₄₈]PF₆ was generated.So,the ionic liquid combined with the target analyte was easy to be separated from the aqueous phase,and they can be completely deposited and solidified at the bottom of the centrifuge tube through the ice bath.At the same time,the extraction conditions,such as amount of ionic liquid,the molar ratio of[P₄₄₄₈]Br to NH₄PF₆,concentration of NaCl,ultrasound time,ultrasound power,pH,centrifugation rate and time,bath-water temperature and time were thoroughly evaluated.Under the optimal experimental conditions,the phenylurea herbicides had a good linear relationship?r>0.9994?.The spiked recoveries at low,medium and high concentration level of eight kinds of vegetable samples were 88.19%¹08.07%.The LODs and LOQs were 1.73⁷.22?g kg^-11 and 5.76²4.07?g kg^-1,respectively.The RSD was lower than6.9%.The results showed that this method can be used for the determination of phenylurea herbicides in vegetable samples.In the Chapter 4,in order to control the residues of phenylurea pesticide in cereal samples effectively,a dynamic ultrasonic assisted matrix solid-phase dispersion ionic liquid microextraction method was established for the determination of four phenylurea herbicides in cereal samples,including monuron,chlorotoluron,isoproturon and dluron.In this study,the hydrophilic ionic liquid[P₄₄₄₈]Br was used as the extraction solvent to transfer the target analytes from grain sample to the ionic liquid aqueous solution under the assistance of matrix solid phase dispersion and dynamic ultrasound.The hydrophilic ionic liquid[P₄₄₄₈]Br was transformed into hydrophobic ionic liquid[P₄₄₄₈]PF₆ by the in-situ reaction between the ionic liquid and the ion pair reagent NH₄PF₆.The target analytes were enriched in ionic liquid and analyzed by HPLC-DAD.In this study,the factors affecting the extraction efficiency were optimized.Good linear relationship?r>0.9997?was obtained in the linear range.The LODs and LOQs of the four target analytes were 1.88⁴.94?g kg^-1and 6.26¹6.47?g kg^-1,respectively.The recovery was 84.57%¹13.52%and the RSD was less than 4.8%.The results showed that this method can be used for the separation and detection of phenylurea herbicides in cereal samples.