Application Of Deep Eutectic Solvents Combined With Dispersion Liquid-Liquid Microextraction Technology In Food And Commodity Analysis

With the improvement of people’s living standards,human have begun to pay attention to environmental protection.Extensive use of organic solvents can cause harm to the environment and human body.In 2003,Abbott introduced deep eutectic solvents(DESs)which could replace organic solvents.DES is a kind of low-toxicity,low-cost and biodegradable green solvent,which possesses excellent chemical properties.In recent years,DES has been recognized by scholars who widely apply it to medicine,chemical engi neering,biology,chemistry and other fields.Among them,scientists have published a large number of literatures on the concentrate and analysis of trace substances with DES as extractants or dispersants combined with HPLC-UV,CE,LC-MS and other detection methods,which provides the possibility for DES to replace traditional organic solvents.This thesis explored four methods DES-based dispersive liquid-liquid microextraction methods combined with HPLC-UV to determine target analytes in four different matrices.This theses is divided into six parts.Chapter 1:The concept,preparation method,physicochemical properties of DES,and judgment method of force between DES and target analytes were introduced,then the applications of DES in dispersive liquid-liquid microextraction from 2016 to 2021 were summarized.Finally the thesis elaborated thoughts and research in this work.Chapter 2:A method based on hydrophilic DES as dispersant,hydrophobic DES as extractant and vortex-assisted dispersive liquid-liquid microextraction combined with HPLC-UV was developed for the determination of four synthetic pigments in beverages,which selected the DES prepared by Ch Cl and phenol as dispersant to reduce the extraction time.The prepared DES was characterized by FT-IR and ~1H NMR.The optimized extraction conditions by optimizing the main parameters of the experiment were determined.Under optimized conditions,four synthetic pigments showed good linearities within 0.05-3.50μg/m L,RSD(n=5)less than 5.5%,and the limit of detection were within the range of0.02-0.24μg/m L.The spiked recoveries were between 80.1-111.9%.This work provided a new idea for the extraction of synthetic pigments from beverages.Chapter 3:A method of vortex-assisted dispersive liquid-liquid microextraction based on hydrophobic DES combined with HPLC-UV to determine synthetic pigments in beverages and candies was established.This method prepared a ternary hydrophobic DES as extractant.The addition of ethylene glycol in the DES increased its hydrophilicity and accelerated extraction process.The prepared DES was characterized by FT-IR.The optimized extraction conditions by optimizing the main parameters of the experiment were determined.Under the optimal conditions,five synthetic pigments showed good linearities within 0.01-10.00μg/m L,RSD(n=6)less than 3.5%,the limits of detection were between 1.08-8.84 ng/m L,and the spiked recoveries were between 83.5-114.5%.This method has lower limits of detection and higher precision.Chapter 4:A method for the determination of phenolic acids in edible oil which was based on hydrophilic DES as extractant,ethanol as dispersant and vortex-assisted dispersive liquid-liquid microextraction combined with HPLC-UV was developed.Natural DES(NADES)prepared by CHCl and ethylene glycol was used as extractant in this method,which met the standard of green chemistry.The prepared DES was characterized by FT-IR and ~1H NMR.The optimized extraction conditions by optimizing the main parameters of the experiment were determined.Under the optimal conditions,four phenolic acids showed good linearities within 0.01-3.00μg/m L,RSD(n=6)less than 7.0%.The limits of detection were between 2.87-11.82 ng/m L,and the spiked recoveries were between 72.8-118.6%.This method provided a new method of evaluating the nutritional value of edible oil.Chapter 5:A method of use methanol as the dispersant and dissolving agent,DES as the extractant and vortex-assisted dispersive liquid-liquid microextraction combined with HPLC-UV to successfully determine the content of preservatives in daily necessities metho d was established.The sample preparation was mainly divided into two steps.In the first step,methanol was added to the sample to be determined and dissolved in a vortex.After centrifugation,the supernatant was obtained and dissolved in 0.22μm micro membrane filtration for standby.In the second step,a part of the methanol solution obtained in the first step was added to water,and then DES was added in water to proceed vortex assisted dispersive liquid-liquid microextraction.Two kinds of molecular structures and the combined structures of Des were optimized by using Gauss View and Gaussian software,which proved that thymol and octanol can theoretically form DES.The prepared DES was characterized by~1H NMR.The optimized extraction conditions by opti mizing the main parameters of the experiment were determined.Under optimized conditions,three preservatives showed good linearities within 0.01-20.00μg/m L.The limits of detection were between 0.72-1.53 ng/m L.RSD(n=6)less than 2.6%,and the spiked recoveries were between 91.2-120.3%.This method provides a reference for the separation and analysis of preservatives in daily necessities.