Hexafluoroisopropanol/alkyl Carboxylic Acid Based Supramolecular Microextraction And Its Application

Supramolecular solvent is one of the most popular materials.Supramolecular solvent microextraction is a simple,fast,easy,quick,environmentally-friendly novel liquid-liquid extraction method with low toxicity and cost.Alkyl carboxylic acid is an amphiphilic molecule with low toxicity and density;it is also a biosurfactant with low ultraviolet absorption.Supramolecular solvent systems based on alkyl carboxylic acid,including alkyl carboxylic acid-tetrahydrofuran(THF)and alkyl carboxylic acid-tetrabutylammonium hydroxide supramolecular systems,have been reported recently.They have shown high efficiency in extraction and elimination of matrix effects,and have been widely applied to determine various analytes in different matrix.However,these alkyl carboxylic acid based supramolecular systems have some drawbacks as follow:? The collection of supramolecular solvent phase is difficult due to its low density and small volume.? Large volume of THF(generally above 20%,v/v)was consumed.Based on the properties of hexafluoroisopropanol(HFIP),such as high density(1.596 g/cm3),high hydrophobicity(logP 1.57),strong dissolving capacity and strong hydrogen bond donor(1.96),we firstly introduced HFIP as a novel solvent of alkyl carboxylic acid,supramolecular solvent inducer and density modifier.As a result,HFIP-alkyl carboxylic acid-H2O supramolecular solvent system were developed,and applied to the extraction of trace analytes in different food matrix.The main works are as follows:(1)HFIP-Alkyl carboxylic acid-H2O supramolecular system was developed.The phase behavior,phase composition and supramolecular solvent phase microstructure of the system were detailly investigated.In addition,the mechanism of HFIP-alkyl carboxylic acid supramolecular solvent microextraction was explained.The results showed large supramolecular solvent region in the phase diagram,which provides solid foundation for further application.The contetnt of octanoic acid and HFIP,and pH of aqueous solution have great influence on the formation of supramolecular solvent;ionic strength below 50 mM and methanol addition below 1%(v/v)have no influence on the formation of supramolecular solvent.Supramolecular solvent was composed of large percentage of HFIP and water,low percent of alkyl carboxylic acid and alomost no chloride ion;increasing the addition of HFIP in the system,the mass fraction of water showed linear increasement,while the mass percentages of HFIP and alkyl carboxylic acid decreased.In the system of octanoic acid(1%,v/v)-HFIP(5-15%,v/v)-H2O,about 69-91%(w/w)of octanoic acid entered into the supramolecualr phase after phase separation,which is favor of the high extraction efficiency for analytes.HFIP-octanoic acid supramolecular solvent is composed of spherical droplets,which are reverse micelle assemblies with a wide size distribution(100 nm-5 ?m).Preliminary extraction experiments proved that the main interaction between HFIP-octanoic acid supramolecular solvent and analytes are hydrogen bond and hydrophobicity,and the extraction for nonpolar analytes showed better performance than for polar analytes.(2)HFIP-Octanoic acid supramolecular solvent system coupled HPLC-UV was developed for the determination of trace dyes adulterated illegally in various beverages.The effects of different factors(including supramolecular solvent composition,extraction condition etc)on the extraction efficiency were investigaed.This supramolecular solvent provides enrichment factor of 45 and extraction rate of 19%for rhodamine B,while the enrichment factors of 141-167 and extraction rates of 59-70%for sudan dyes.The LOD of rhodamine B,sudan ??G?????? are between 0.027-1.050 ng/mL,LOQ are between 0.091-3.499 ng/mL.Relative recoveries are between 81,35-116.28%,intraday and interday precisions are below 9.55%.Recoveries for analysis of practical samples are between 80.27-119.71%with RSD less than 9.98%.(3)HFIP-Octanoic acid supramolecular solvent extraction system coupled HPLC-UV was developed for the determination of trace phthalates in liquid foods migrated from disposable plastic cups.Two food simulants(water and alcohol)were used.The effects of various conditions,such as standing time,temperature,status and washing time,on the migrating amount of phthalates in waer and alcohol simulants were systematically investigated.In water simulant,LOD of phathlates are between 0.146-0.277 ng/mL,LOQ are between 0.487-0.923 ng/mL;Relative recoveries are between 89.6%-113.2%,intraday and:interday percisions are below 7.70%;enrichment factors for phthalates are between 252and 284.In alcohol simulant(15%,v/v,ethanol aqueous solution),LOD of phathlates are between 0.34-2.79 ng/mL,LOQ are between 1.15-9.32 ng/mL;Relative recoveries are between 84.34-109.52%,intraday and interday percision are below 9.97%;enrichment factors for phthalates are in range of 104-164.Butyl Benzyl Phthalate(BBP),Dibutyl phthalate(DBP),and Di(2-Ethylhexyl)phthalate(DEHP)were detected in water and alcohol simulants filled in real disposable plastic cup.Different conditions and food matrix have influence on phthlates migration behavior,to a different extent.