Design Of Novel Hydrophobic Deep Eutectic Solvents And Their Application In Extraction,Separation And Analysis Of Trace Contaminants

Liquid-liquid extraction is one of the main methods to remove environmental pollutants.However,toxic,harmful,and volatile traditional organic solvents are often used in the liquid-liquid extraction process.In recent years,with the gradual improvement of public awareness of environmental protection,the concept of"green chemistry"has been increasingly popular.Therefore,people are eager to find some green solvents that can replace traditional volatile organic solvents.Among them,the most widely known ionic liquids are considered to be a kind of"green"solvent due to their excellent physical and chemical properties such as non-volatile,good solubility and diverse structure.However,with the further studies on ionic liquids,it has been found that the synthesis of ionic liquid is difficult and sensitive to the presence of impurities,and even some ionic liquids are more toxic than traditional organic solvents.Deep eutectic solvents are a new class of green solvents discovered in recent years and are called analogs of ionic liquids.Deep eutectic solvents have some advantages similar to ionic liquids,such as low vapor pressure,wide electrochemical window,wide liquid range,good biocompatibility and dissolution performance,etc.They also have the advantages of simple synthesis,100%atomic utilization,and adjustable performance.However,the current research work is mainly on the application of hydrophilic eutectic solvents in non-aqueous systems.Hydrophilic eutectic solvents are very water-soluble,which greatly limits their application in the aqueous phase.Based on this,several novel hydrophobic deep eutectic solvents were designed and synthesized in this paper,their physical and chemical properties were studied,and they were directly applied to the enrichment,separation and determination of pollutants in actual samples as extraction agents.The main research contents were as follows:1.A new family of paraben/quaternary ammonium salt hydrophobic deep eutectic solvents was designed and synthesized.The values of density,viscosity,melting point,stability and hydrophobicity for each hydrophobic deep eutectic solvent were measured,and then they were directly used to extract Cr(VI)from water.The results showed that the hydrophobic deep eutectic solvent could extract Cr(VI)at a molar ratio of 1:1,the extraction amount was up to 66.7 mg/g,and the extraction efficiency for ultra-trace Cr(VI)(0.51g/L)was still higher than 90%.When the concentration of inorganic metal ions and organic molecules was 2000 times that of Cr(VI),the extraction efficiency of DES for Cr(VI)was still more than 90%.The hydrophobic deep eutectic solvent was used for enrichment of Cr(VI)in actual water samples,and the extraction recovery was between 93%～108%.The possible extraction mechanism of Cr(VI)by hydrophobic deep eutectic solvent was studied by FT-IR and ~1H NMR.2.When low-toxicity parabens were used as extractants,they could form a hydrophobic deep eutectic solvent with the fluorescent whitening agent 52 through hydrogen bonding.Based on this,a new method was proposed to extract and enrich fluorescent whitening agent 52 in foods by forming in situ hydrophobic deep eutectic solvent.The effects of extraction agent type,dosage,extraction time,p H value,temperature,coexisting compounds and other factors on extraction efficiency were investigated.Under the optimal experimental conditions,the extractant could be used to extract ultratrace(0.05μg/L)fluorescent whitening agent 52,and common inorganic salts and organic compounds had little effect on extraction.The method had a good linear range of 0.20～25μg/L and a low detection limit of 0.045μg/L.In addition,the new method was used directly to enrich,separate and determine fluorescent whitening agent 52 in actual food samples(noodles,fish balls,mushrooms)and food contact materials(paper cups).The extraction recovery was 82%～113%,and the relative standard deviation(RSD)was 4.7%～9.9%.3.Two novel types of low-viscosity hydrophobic deep eutectic solvents were designed and synthesized with octyl paraben as the hydrogen bond donor and chloraniline and ethyl n-phenylcarbamate as the hydrogen bond acceptors.Their physicochemical properties such as melting points,densities,and viscosities were characterized.The hydrophobic deep eutectic solvents were directly used in the analysis and determination of benzotriazole and benzophenone ultraviolet filters in actual samples.The hydrophobic deep eutectic solvents had low viscosities,and the extraction equilibration time was 1 minute.Common high-concentration inorganic salt ions,organic compounds and metal ions had little effect on extraction.This method could be used for analysis and determination of ultraviolet filters in actual water samples and sunscreens,and the extraction recovery was 90%～107%.The possible extraction mechanism of the hydrophobic deep eutectic solvents for ultraviolet filters was studied by FT-IR.