Study On A New Method Of Dispersive Liquid-liquid Microextraction Combined With Capillary Electrophoresis

Nowadays,people have higher and higher requirements for diet quality.Therefore,food safety issues such as excessive use of food additives and drug residues cannot be underestimated.This kind of problem has always been a hot issue in food safety,so it is particularly important to extract and detect additives and residual drugs in different foods.As a new type of liquid phase separation technology,capillary electrophoresis(CE)has the advantages of green,environmental protection,fast and efficient,and small amount,but it also has the shortcomings of short detection optical path,small injection volume,and "electroosmosis" phenomenon.Dispersive liquid-liquid microextraction(DLLME),as a new liquid phase microextraction technology,can extract and enrich the analyte to be tested.In view of the above characteristics,this thesis combines and studies the nw methods of liquid-liquid dispersion micro-extraction technology with capillary electrophoresis technology.The experiment is mainly carried out from the following three systems:1.In order to determine the residual fluoroquinolone compounds in actual samples such as milk,honey and environmental waters,this experiment established a new combined method based on deep eutectic solvent(DES)salting-out assisted dispersive liquid-liquid micro-extraction-back-extraction(SA-DLLME-BE)and micellar electrokinetic capillary chromatography(MECC).IIn the experiment,we used6 FQs such as enrofloxacin as the target analytes,and systematically investigated the extraction conditions(DES volume,Vortex time,centrifugation time),stripping conditions(hydrochloric acid concentration,hydrochloric acid and ethanol volume ratio),the type and amount of salt,the p H and volume of the sample solution.Under optimized conditions,this experiment further determined the FQs in actual samples such as milk,honey and environmental water,and verified the feasibility of the combined method for the determination of fluoroquinolone compounds in actual samples of mixed matrix through the evaluation of method performance.2.In this experiment,a combined method of ultrasonic-assisted dispersive liquid-liquid microextraction(UA-DLLME)and micellar electrokinetic capillary chromatography(MECC)was established to detect bisphenol compounds(BPs)in edible oils.This study is the first time to detect and analyze the bisphenol compounds in edible oil by combined ultrasonic-assisted liquid-liquid dispersion microextraction(UA-DLLME)with micellar capillary electrokinetic chromatography(MECC).In this experiment,bisphenol A,bisphenol F,and bisphenol S are used sa the target analytes,and the effects of many factors such as capillary electrophoresis separation conditions(water column injection time,electric injection time,SDS concentration in sample solution,acetonitrile concentration,isopropanol concentration,SDS concentration in buffer solution)and ultrasonic-assisted dispersive liquid-liquid microextraction conditions(DES molar ratio and volume,extracted phase volume ratio and total volume,auxiliary extraction method,ultrasonic time,centrifugal time)on the recovery rate are systematically investigated.3.In order to determine whether there are traces of pyrazine compounds in actual samples such as milk tea and coffee,this system cleverly combines salting-out auxiliary dispersive liquid-liquid microextraction(SA-DLLME)with capillary electrophoresis(CE).In this experiment,8 BPs such as tetramethylpyrazine are used as target analytes.The effect of buffer p H and concentration on migration has been systematically studied.A series of experimental parameters such as the type and volume of organic solvent,the type and amount of salt have been optimized.Under optimized conditions,this experiment successively carried out the determination of 8pyrazine compounds in actual samples such as milk tea and coffee.The experimental results show that the combined method of SA-DLLME and MECC can detect pyrazine compounds quickly and efficiently,and the analysis results are accurate.