Study On Hexafluoroisopropanol/non-ionic Surfactant Based Novel Solvents And Their Application In Liquid-phase Microextraction

The miniaturization of extraction technology and the greening of extraction solvents are the development trend of green analytical chemistry.As a new generation of green solvents,supramolecular solvent（SUPRAS）and deep eutectic solvent（DES）have been rapidly developed in the liquid-liquid extraction（LLE）field.SUPRAS is a flexible,efficient and safe extraction solvent with its chemical composition and structure controllability,restricted entry characteristics to biomacromolecules,and non-volatile and non-flammable properties.DES is easy to prepare,low in cost,high in purity,and has excellent properties such as low volatility,good biocompatibility and environmental friendliness.However,the existing SUPRASs have the problems of strict formation conditions and difficulty in collecting the small amount of low-density extraction phase,and the development of existing DES still has the following shortcomings:most of DESs are miscible with water and are not in liquid state under room temperature;the extraction efficiency for non-polar compounds is poor.Therefore,it is of great significance to study SUPRAS with high density and mild extraction conditions and hydrophobic DESs with a low freezing point for the development of new green solvents in the field of LLE.In this paper,HFIP（with several superior properties）and nonionic surfactants（environmentally friendly）were used as the main research objects.The green solvents SUPRAS and DES based on HFIP/non-ionic surfactant were prepared and the physicochemical properties of the solvents were characterized,and the LLMEs based on SUPRAS and DES were proposed,respectively.The specific research contents are as follows:（1）The HFIP/Brij-35/H₂O SUPRAS system was successfully developed,HFIP/Brij-35 SUPRAS-based LPME was coupled with HPLC-DAD for the extraction and quantitative detection of parabens in water samples,pharmaceuticals and personal care products.The phase behavior,microstructure and the formation mechanism of HFIP/Brij-35 SUPRAS were systematically studied.The results show that a little amount of HFIP（0.4%-1.7%,v/v）can drastically reduce the cloud point（>100 ^oC）of Brij-35 aqueous solution and rapidly induce the formation of a stable,low-volume（the phase ratio was between 0.013-0.111）,high-density SUPRAS over a wide range of conditions（0.5-10%Brij-35,g/m L）at room temperature（even 0 ^oC）.The HFIP/Brij-35 SUPRAS consists of micelle aggregates（2-8μm）and can generate strong hydrogen-bonding and hydrophobic interactions with target analytes.In addition,the volume and composition of HFIP/Brij-35 SUPRASs are environmentally responsive,and the SUPRAS with specific volume and composition could be synthesized over a wide liquid-liquid two-phase region,which undoubtedly beneficial for the optimization of extraction conditions in real applications.The optimal extraction conditions were obtained by constructing the response surface model by Plackett-Burman design（PBD）and central composite design（CCD）.Under the optimal conditions,the linear correlation coefficient was good in the range of 2-400 times LOQs,（R>0.9990）,the LODs were ranged from 0.042 to 0.167μg/L,and the enrichment factors were 26-193.The recoveries of the analytes ranged from 92.9%to 108.1%,and the intra-day and inter-day precision（RSDs,n=3）were less than 6.8%and 7.9%,respectively.The recoveries for the spiked real samples were in the range of 90.2%–112.4%with relative standard deviation less than 8.9%.Except for tap water,one or several paraben（s）were detected in all the other real samples.The method was a simple and fast（extraction time is 3 min）,environmental friendly（organic solvent consumption is 0.3 m L）sample preparation method with high sensitivity.（2）New hydrophobic DESs were synthesized using HFIP as a hydrogen bond donor and nonionic surfactants（Brij-35,PONPE-7.5,Triton X-100,Triton X-114）as hydrogen bond acceptors,vortex-assisted DES based LPME coupled with HPLC was introduced to determine five Sudan dyes in tomato chili sauces.The physical and chemical properties of DESs were studied and the results showed that the freezing point of these DESs was lower than-10 ^oC,which can be stably existed at room temperature,the viscosities and polarities of DESs were adjustable,and the densities of DESs were higher than water.Through observation of the microstructure of DES-rich phase,a DES/water/DES like composite emulsion structure was in sight,which strengthen the hydrophobic and hydrogen bonding interactions between DESs and analytes.One-variable-at-a-time（OVAT）,significant factor screening experiments and response surface methodology（RSM）were used to obtain the best extraction condition.The internal standard curve was plotted for method evaluation and the quantitative detection of Sudan in five real samples.For the five Sudan dyes,under 0.04-2μg/g concentrations,the regression coefficients were higher than 0.999,the LODs were between 0.0045-0.0118μg/g,and the recoveries of the three spiked samples were in the range of 91.6%-104.5%,and the intra-day and inter-day precision（RSDs）were less than 8.0%.The method was applied to the detection of five kinds of tomato samples,the recovery was between 87.5%-110.1%,and the RSD was less than 7.1%,and Sudan I was detected in one sample.The proposed method requires a short extraction time and consumes less organic solvent,which is a simple,environmentally friendly and efficient sample preparation method.