The Application Of Switchable-solvent Dispersive Liquid-liquid Microextration For The Rapid Determination And Separation Technique

Dispersive liquid-liquid microextraction?DLLME?technology has been widely used for its excellent performance,such as excellent green chemistry index and hundreds of times.It is a three element extraction system composed of extractant,dispersant and aqueous solution.This paper from the perspective of extractant gives a new interpretation for the dispersive liquid-liquid microextraction technology.The switchable-solvent dispersive liquid-liquid microextraction technology combined with rapid determination and separation techniques was used for water samples,urine samples and oil samples in the detection of harmful substances.The thesis is divided into four chapters,the contents are as follows:Chapter 1: The concept of dispersive liquid-liquid microextraction,the classification of extractant in dispersive liquid-liquid micro-extraction,and the purpose,content and significance of this work were elaborated.Chapter 2: In this study,a switchable-solvent dispersive liquid-liquid microextraction technique combined with smart-phone three primary color method was first used for determining thiram in water samples.Thiram and Cu²⁺ can form a stable yellow hydrophobic chelate under an alkaline condition.m-chloroaniline,which was used as a basic extractant,is soluble in acid.Then sodium hydroxide was added into the sample aqueous to adjust the pH of the solution so that the colored hydrophobic analyte can be extracted into the organic phase that is insoluble in alkaline solution.The whole process was achieved without the help of any dispersant and was completed in a few seconds.The procedure of smart-phone measurement was finished in a collapsible homemade case,which was simple,rapid and economical.Under the optimum conditions,the value of log?v0/vB?was linear in the concentration ranges of 0.08¹.5 ?g/m L,the limit of detection?LOD,S/N=3?was 0.076 ?g/m L.Then,this method was used for the determination of thiram in actual water samples and the recovery was between 80% and 119%.Low-cost and convenient as that method was,it offers the possibility of the on-site determination of thriam in wild water.Chapter 3: In order to explore the applicability of switchable-solvent dispersive liquid-liquid microextraction and capillary electrophoresis technique,this paper put forward acid–base reaction-based dispersive liquid–liquid microextraction coupled with transient isotachophoresis for the analysis of four anilines in urine samples.In this method,a basic organic solvent?m-chloroaniline?was used as an extraction solvent.It was dissolved in acidified deionized water and then injected into an alkaline aqueous sample solution.After injection,an acid–base reaction occurred and deprotonation of the organic solvent led to formation of tiny droplets of the extractant and subsequent extraction of the analytes from sample solution.After centrifugation,extractant phase was dissolved in 1:1 methanol / buffer solution,forming homogeneous solution,and can be directly into the capillary electrophoresis in large volume.Under the optimum extraction conditions,the developed method showed good performance,the standard curve of 4 kinds of aniline has a good linear relationship in the 0.005 ?g/m L-1.5 ?g/m L,0.02 ?g/m L-8 ?g/m L,0.02 ?g/mL-8 ?g/m L,0.04 ?g/m L-8 ?g/mL,with correlation coefficients of greater than 0.999.The low limits of detection was 0.97-3.22 ng/mL,relative standard deviations of less than 2.40% for the extraction each aniline were obtained for intra-?n = 6?and inter-day?n = 4?precisions,enrichment factor was between 28 and 127.It was a good solution to the problem of compatibility between hydrophobic extractant and background electrolyte solution,and different urine samples were successfully analyzed using the proposed method.It provided a promising means for determining anilines in some samples at ng/ mL levels.Chapter 4: In order to further expand the applicable sample kinds of switchable-solvent dispersive liquid-liquid microextraction coupled with large-volume-injection based capillary electrophoresis,a two-step extraction method was proposed,which was composed of normal phase extraction based on the new ‘green' solvent-deep eutectic solvent,and reverse phase extraction based on switchable-solvent dispersive liquid-liquid microextraction.The aniline compounds from the heated vegetable oil were analyzed to demonstrate the feasiblility of the two-step etraction method for treating oil sample.In the first step,the normal-phase extraction was accomplished with hydrohilic deep eutectic solvent synthesized from chloline chloride and ethylene glycol,and the polar analytes from oil samples were extracted.In the second step,the target polar compounds were released from the deep-eutectic-solvent extract into the alkaline aqueous solution,and the released compounds were extracted by chloroaniline injected into the system.After extraction,the target analyte was extracted into the organic phase.Then finish extract was dissolved in background electrolyte solution,which can be directly injected into the capillary.In the optimal condition,the two step extraction technology showed good performance,the correlation coefficient R2 > 0.999,the linear range of two analytes were 0.0025 ?g/mL-1.0 ?g/mL and 0.01 ?g/m L-6 ?g/m L,the detection limit was 0.97-3.22 ng/mL and RSD% < 2.49,n=3.The above mentioned extraction technology had a good sensitivity and stability,which opened a new way for the determination of polar compounds in ng/m L samples.