The Application Of Adjustable Deep Eutectic Solvents In Food And Water Samples

Deep eutectic solvent（DES）is a eutectic mixture formed by mixing hydrogen bond donors and hydrogen bond acceptors in a certain proportion.Under normal circumstances,the composition and proportion of hydrogen bond acceptors and hydrogen bond donors are changed to adjust the properties of DES,such as hydrophobicity and viscosity.DES has some advantages of low raw material cost,simple synthesis method,adjustable chemical properties and good bio-compatibility,which has caused extensive researches.In this thesis,the adjustable DES was combined with aqueous two-phase extraction technology and back extraction method,which was applied to detect different target analytes in food and water samples.The thesis is divided into five chapters:Chapter 1:The classification,synthesis and physicochemical properties of DES were introduced.DES has been applied in aqueous two-phase system,back extraction and in situ liquid-liquid microextraction.The research ideas and contents of this article were proposed.Chapter 2:A DES/K₂HPO₄aqueous two-phase extraction system combined with capillary electrophoresis was established for the determination of phenolic acids in red wine,vinegar and beverages.The hydrophilic DES formed by choline chloride and polyethylene glycol 200 was used as the extractant.K₂HPO₄was added to form an aqueous two-phase after centrifugation.The phenolic acid was successfully extracted into the upper phase DES.Parameters affecting the extraction efficiency were optimized,such as the type and amount of DES,the type and amount of inorganic salts and the p H of the solution.DES was characterized by Fourier transform infrared spectroscopy.Under the optimal conditions,the recoveries were from 88.3 to 99.4%,the linear range was 0.9～40.0μg/m L,and limit of detection（LOD）was 0.03～0.14μg/m L.The sample preparation method is greener.This method was successfully applied to the determination of phenolic acid in food.Chapter 3:A DES/Na₂CO₃aqueous two-phase system combined with a spectrophotometer to simultaneously determine lemon yellow and brilliant blue in beverages and candies was established.The hydrophilic DES synthesized by polypropylene glycol 400and tetrabutylammoniumbromide was used as extractant,and Na₂CO₃was used as the phase separation agent.The absorbance values of lemon yellow and brilliant blue were measured at417 nm and 633 nm.The factors affecting extraction recovery were investigated,such as the types and volumes of DES,the types and volumes of phase separators and the effects of interfering ions.Under the optimal conditions,the extraction recoveries of lemon yellow and brilliant blue reached 99.5%and 96.0%;the linear ranges were 2.0～25.0μg/m L,0.5～12.0μg/m L,and the limits of detection were 0.07μg/m L,0.03μg/m L.The greenness value of this method（AES=85）was calculated.The sample preparation process required less phase-separating agents and faster phase separation speed.It was successfully applied to the determination of lemon yellow and brilliant blue in food.Chapter 4:A hydrophobic DES back extraction combined with capillary transient isotachophoresis was developed to separate aromatic amines in water samples.The effects of the type and dosage of DES,p H of solution and injection time on peak area were investigated.Under the best conditions,the linear range was 10.0～1000.0 ng/m L,and the limit of detection was 0.83～2.89 ng/m L.This method solved the problem of the mismatch between the hydrophobic DES and the capillary electrophoresis matrix;Through the differences between the mobility of the lead electrolyte and the trailing electrolyte,the instantaneous isokinetic enrichment of the capillary was realized,and the problem of the short optical path and high limit of detection the UV detector was made up successfully.The method was applied to the determination of aromatic amines in water samples.Chapter 5:In this thesis,the in-situ synthesis of DES liquid-liquid micro-extraction combined with capillary transient isotachophoresis was established to determine the aromatic amines in different water samples and packaging bags.The hydrogen bond donors and hydrogen bond acceptors were added to the sample solution and vortexed to achieve synthesis and extraction in one step.Under the optimal conditions,the linear range was 10.0～1000.0ng/m L,and the limit of detection was 1.32～2.77 ng/m L.DES was characterized by Fourier transform infrared spectroscopy,and the extraction mechanism was discussed.This method achieved the one-step completion of synthesis and extraction,combined with capillary electrophoresis to realize enrichment,which was successfully applied to the determination of aromatic amines in water samples and packaging bags.