Performance Research Of Hydrophobic Fatty Acid-based Deep Eutectic Solventsliquid-liquid Microextraction

With the deepening of humanity’s knowledge and understanding of environment pollution,the concept of green chemistry has been mentioned more and more.Green solvents are an important part of green chemistry.As a new generation of green solvents,deep eutectic solvents have the advantages of green environmental protection,simple preparation process,low preparation cost,etc.,and have great application potential in sample pretreatment technology.Based on this,ten hydrophobic deep eutectic solvents were designed and synthesized in this paper and used as extraction agents for liquid-liquid microextraction methods.Combined with high performance liquid chromatography,a hydrophobic deep eutectic solvent based liquid-liquid microextraction method was established.This method is used for the analysis and determination of pollutants in environmental samples,biological samples and food samples,which has broadened the application of eutectic solvents in sample pretreatment.The main research contents are as follows:1.Four hydrophobic deep eutectic solvents composed of trioctyl methyl ammonium chloride and oleic acid were designed and prepared.Based on the hydrophobic eutectic solvent vortex-assisted liquid-liquid microextraction combined with high performance liquid chromatography,a new method for the selective enrichment and detection of nitrite ions in actual water and biological samples was established.This method is based on the diazotization-coupling reaction of nitrite with p-nitroaniline and diphenylamine under acidic conditions,and then the nitrite is quantified indirectly by measuring the obtained azo compounds.Some factors influencing the extraction efficiency,including the reaction and extraction conditions,were investigated.Under the optimized conditions,the method has a linear range of1–300μg L^-1 with a correlation coefficient of 0.9924,limit of detection of 0.2μg L^-1,limit of quantitation of 1μg L^-1,intraday and interday relative standard deviations of 4.0 and 6.0%.This method was successfully applied in determination of nitrite from three environmental water and two biological samples and the recovery was 90.5–115.2%.2.Long-chain fatty acids with different chain lengths were stirred and mixed at room temperature,and then three kinds of hydrophobic eutectic solvents with low viscosity,less than water density,and melting point close to room temperature were prepared.They were used as an extractants for suspension-solidified air-assisted liquid-liquid microextraction,and combined with high-performance liquid chromatography,a new method for detecting benzophenones and salicylates in environmental water samples is established.The response surface method was used to optimize some influencing parameters,such as the volume of the extraction solvent,the p H of the sample solution,the number of extraction cycles and the addition of salt.It was found that under optimized conditions,the detection limit and quantitation It was found that under optimal conditions,the limits of determination and quantification were 0.045-0.54μg L^-1 and 0.15-2.0μg L^-1,respectively.The relative standard deviations for inter-day（n=5）and intra-day（n=5）precision were≤4.2%,whereas the enrichment factors for the ultraviolet filters were obtained from 41 to50.Furthermore,this novel method was successfully employed for the detection of ultraviolet filters from real water samples.The recoveries were 87.5%-105.8%,whereas the RSDs were lower than 3.6%.3.Menthol was selected as hydrogen bonding acceptor while lauric acid as hydrogen bonding donor,three green hydrophobic eutectic solvents were synthesized at different molar ratios.Based on the characteristics of the hydrophobic eutectic solvent with low viscosity and melting point close to room temperature,it was used as an extractant and combined with high performance liquid chromatography,an air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent method was established to simultaneously determine bisphenols and polycyclic aromatic hydrocarbons in homemade tea drinks.The main factors affecting the extraction efficiency were screened out using Plackett-Burman design,and then the factors affecting the extraction efficiency were optimized.Under optimized conditions,the linear ranges of bisphenols and polycyclic aromatic hydrocarbons were 2.5-400μg L^-1 and 0.5-200μg L^-1,with correlation coefficients greater than 0.9928.The detection limit of bisphenols was 0.75μg L^-1,and the limit of quantification was 2.5μg L^-1.The detection limit of PAHs was0.16-0.6μg L^-1,and the limit of quantification was 0.5-2.0μg L^-1.The relative standard deviations for inter-day（n=5）were between 0.9-2.0%and intra-day（n=5）were less than 2.3%.The method was successfully applied to the determination of bisphenols and polycyclic aromatic hydrocarbons in homemade tea water,and the spiked recovery was 83.8–104.8%.