Synthesis Of Novel Hydrophobic Deep Eutectic Solvents And Their Chromatographic Applications In Sample Pretreatment Technology

In recent years,for the sake of the concept of green development,it was one of the most attractive subjects to develop sustainable and green solvents with low toxicity and cost.Deep-eutectic solvents(DESs)are a new generation of green solvents after ionic liquids and they share similar solvent properties,such as negligible vapor pressure,wide liquid range,non-flammability,and good solubility for organic and inorganic compounds.Additionally,DESs have the advantages of low cost,easy preparation and 100%utilization of reactant atoms,which makes up for the disadvantages of the complex preparation and difficulty purification of ionic liquids.These remarkable advantages make DESs to be potential alternatives of expensive ionic liquids and traditional volatile organic solvents,and therefore has attracted great interests in the past few years.However,due to the hydrogen bonding with water,most deep eutectic solvents cannot be used in aqueous systems.In an effort to overcome this,we designed and synthesized a series of new hydrophobic DESs,which are applicable for aqueous systems,by selecting different types of hydrogen bonding donors(HBDs)and hydrogen bonding acceptors(HBAs).Their physicochemical parameters,such as density,viscosity,melting point,thermal stability and hydrophobicity,were obtained by various techniques.The extraction behavior of some typical pollutants,such as phthalate esters and bisphenols,was studied by using self-made hydrophobic DESs as extractant.Some important factors during the extraction process,such as the type of DESs,the volume of the sample,extraction time,ionic strength,p H value of the solution and so on,were systematically investigated,and the relevant mechanism was elucidated with the study of chromatography.On this basis,the synthesized hydrophobic DESs were used as an addictive to prepare poly(dimethylsiloxane)(PDMS)fiber coating using sol-gel method,and combined with gas chromatography to detect the volatile benzene series in water media.The new hydrophobic DESs was used as extraction solvent to enrich and separate the phthalates and bisphenols from the leaching solution of food contaced plastic samples.Finally,new green separation and analysis methods for environmental pollutants in aqueous media were established.The main contents and conclusions of this thesis are listed as following.(1)A series of hydrophobic DESs were prepared by mixing ethylparaben as hydrogen bond donors and methyl trioctyl ammonium chloride as hydrogen bond acceptors.In order to characterize their solvent properties,the density,viscosity,and contact angle of these DESs were determined,and their molecular structure and thermal stability were evaluated by Fourier Transform Infrared(FTIR)and Thermogravimetric Analyzer(TGA).As-prepared DESs were doped into PDMS sol system to prepare hydrophobic DESs mediated PDMS fiber coatings.Scanning Electron Microscope(SEM)results showed that the addition of hydrophobic DES could generate a lot of neat pores in the PDMS fiber surface,effectively increase the specific surface area and control the dry crack of the sol-gel coating,and thus significantly improving the performance of PDMS fiber coating.The feasibility of PDMS-DES fiber coation adopted for head space solid phase microextraction was evaluated by gas chromatography with hydrogen flame ionization detector(GC-FID)for the extraction and determination of volatile organic compounds,such as toluene,ethylbenzene and o-xylene.The results showed that the linear range with PDMS-DES fiber lied between 10-1000?g L^-1,and the limit of detection(LOD)was in the range from0.005 to 0.025?g L^-1.Compared with homemade PDMS fiber,the peak area of signal response for the PDMS-DES fiber was 3 times higher.At the same time,the LOD for the proposed method was much lower than the commercial 100?m-PDMS fiber coating.(2)Eight hydrophobic deep eutectic solvents(DESs)with low viscosity have been designed and prepared from two kinds of quaternary ammonium salts and six kinds of water-insoluble fatty alcohols/acids.Several physical properties of these DESs such as melting point,density and viscosity were measured to investigate their adaptability as solvents,and their molecular structure were evaluated by FTIR.The results showed that the prepared hydrophobic DESs have low viscosity.On this basis,these DESs are used as extraction solvents in a vortex-assisted liquid-liquid microextraction method for the extraction and preconcentration of phthalate esters from water samples by using gas chromatography.The effects of some main extraction parameters on the extraction efficiency were investigated.Under the best conditions,the analytic method developed in this work exhibits wide linear range of 5-1000?g L^-1,and the limit of detections for target analytes is as low as 1?g L^-1.Finally,the proposed method has been successfully used for the determination of PEs from food-contacted plastics.(3)Three types of hydrophobic DESs were synthesized by simple mixing of trioctylmethyl ammonium chloride(used as hydrogen bond acceptor)with decanoic acid,ketoprofen and gemfibrozil(hydrogen bond donors),respectively,at different molar ratios.In order to evaluate the solvent characteristics of these DESs,some of the physical properties such as melting point,density,viscosity,and water contact angle were determined,and their molecular structure were characterized by FTIR in order to explore their adaptability as solvent.Then,these hydrophobic DESs were used for the vortex-assisted liquid-liquid microextraction of bisphenol-type contaminants in water,followed by quantitative determination of bisphenols contents with high performance liquid chromatography(HPLC-FLD)coupled with fluorescence detection.For this purpose,four bisphenols were selected as model contaminants.It was found that the enrichment factors of the proposed method were in the range from 97 to 112,depending on the structure of the analytes.Under optimal experimental conditions,the linearity ranges of the method varied from 0.3 to 700?g L^-1with linear correlation coefficients(R²)higher than 0.996.The limit of detections(LODs)and limit of quantifications(LOQs)were in the range of 0.3-0.5?g L^-1and 0.06-0.08?g L^-1,respectively.Furthermore,the developed method was successfully used in the extraction and determination of four bisphenols from food-contacted plastic samples.The obtained recovery was between81.4%and 109.2%.