The Application Of Improved Dispersive Liquid-Liquid Microextraction

With the development of science and technology,the techniques for detecting sample makes unceasing progress.Sample pretreatment is one of the important steps in the process of determination.The traditional sample extraction techniques have some disadvantages,such as time-consuming operation,large amounts of toxic organic solvents used,therefore,the development time saving,high efficiency,reducing the consumption of organic solvent sample preparation technology has been a hot topic in the study of analytical chemistry field.At present,there are some new pretreatment technologies have appeared,such as solid phase microextraction and liquid phase microextraction,overcome the problems that exist in traditional method.In 2006,Assadi et al.developed a novel liquid phase microextraction technique termed dispersive liquid-liquid microextraction(DLLME).This method is now widely used in the field of trace analysis,because of its simplicity of operator,rapidity,low cost,high enrichment factors and environment-friendly.In this paper,three new pretreatment methods were studied.The thesis is divided into three chapters,the main contents are as follows:Chapter 1: Introduction.A brief overview of sample pretreatment methods is presented.Mainly introduced the research status,application and development trend of dispersive liquid-liquid microextraction,at the same time,the main background,ideas and research contents of this paper.Chapter 2: In this paper,a new extraction method based on counter current salting-out homogenous liquid-liquid extraction followed by dispersive liquid-liquid microextraction has been developed for the extraction and preconcentration of phenol in soil samples prior to it analysis by smartphone platform colorimetric method.In this method,initially,the analyte after derivative reaction,formation color solution,sodium chloride as a separation regent is filled into a small column to a narrow bore tube and a mixture of aqueous solution containing acetonitrile and 1,1,2,2-tetrachloroethane is transferred into the tube.Then open the following stopcock,during the solution though the tube,find droplets of the organic phase are produced at the interface of solution and salt which go up though the tube and form a separated layer on the aqueous phase.After a while,the collected organic phase is removed with a syringe into a centrifuge tube.In the second step,take 3 mL de-ionized injected into centrifuge for more enrichment of the analytes.Finally,sample were successfully analyzed using the development of method.Under the optimum conditions,the value of log(I0/IG)was linear in the concentration ranges of 9~400 ?g/L,the limit of detection(LOD,S/N=3)is 2.7 ?g/L.And the recovery was between 85% and 104%.This method has the advantages of simple operation,low cost and fast phase separation.It does not need to use separation equipment,and has good reproducibility and high recovery rate for analytes.Chapter 3: This present work is based on solid-based dispersive liquid-liquid microextraction followed by high performance liquid chromatography-ultra violet detection(HPLC-UV).In the proposed method,1,1,2,2-tetrachloroethane(extraction solvent)is added on a sugar cube(as a solid disperser)and it is introduced into the water sample containing the analytes.After manual shaking and centrifugation,the sediment is removed with a syringe,after that finished the extraction progress.Under the optimum conditions,the proposed method is applied for the determination of PAHs in water sample.This method is simple,low cost,and environmentally friendly.The disperser solvent and other auxiliary equipment used in conventional DLLME were not required in the proposed new method,due to sugar cube used as the pre-dispersive support.Chapter 4: In this study,an in-situ dispersive liquid liquid microextraction based on solidification of floating organic drop has been developed as a simple,rapid and eco-friendly sample extraction method for the determination of anthraquinones compounds in urine samples followed by HPLC-UV.In this extraction method,the fatty acids were converted into the hydrophilic form by adding sodium hydroxide.And then injected into the acidic sample solution,the protonation fatty acid leads to formation of tiny droplet of extractant and subsequent extraction the analytes from sample solution.In this study,the type and volume of hydrogen donors,the volume of sodium caprylate,the salt addition,and centrifugation time on the extraction efficiency were studied and systematically evaluated.Under the optimum extraction conditions,the compounds has a good linear relationship between 5-400 ng/mL,and all the correlation coefficients are larger than 0.999.The actual sample was analyzed and the recovery was between 82%-110%.The method require neither disperser solvent nor other external energy sources.Therefore,the proposed method is recommended as a simple,rapid,low-cost and environmental benignity way in sample preparation.