Improved Liquid-phase Microextraction Methods And Their Application To The Analysis Of Environmental Pollutants

In the determination of environmental pollutants in real samples, liquid-liquid extraction(LLE)is a classical method for sample preparation and sample preconcentration,but it is laborious,tedious,time-consuming and requires large amounts of toxic organic solvents,which have a bad effect on human health and environment.Therefore,the method of effective,quick, less-solvent consumption or solvent-free extraction as a promising technique for sample preparation and preconcentration has attracted much attention and it becomes one of the most important research areas in modern analytical chemistry recently.Much effort had been placed on greatly reducing the amount of organic solvent to simplify the LLE extraction procedure which led to the development of liquid-phase microextraction(LPME)methodology.LPME is based on the distribution of the analytes between a microdrop of organic solvent at the tip of a microsyringe needle and aqueous sample solution.In LPME, analytes were extracted from aqueous samples by only micro-litre even nano-litre organic solvents.LPME has been developed into direct LPME (DI-LPME),headspace LPME(HS-LPME),continuous-flow LPME(CFME), hollow fiber based LPME(HF-LPME)and solvent bar microextraction(SBME). This technique combines extraction,preconcentration and sample introduction in one step,and proved to be simple,fast,low-cost,simple experimental setup, short analysis time and minimum use of solvent.It belongs to the green analytical technique and is suitable to the development trend of micromation of modern analytical science.Compared with solid-phase microextraction(SPME), LPME has a remarkable advantage that no special interface is needed when combining it with high performance liquid chromatography(HPLC).Up to now, LPME has been successfully applied to the environmental monitoring,food analysis,biological and medical analysis.However,owing to its disadvantages such as instability of microdrop;relatively low precision and sensitivity are often encountered;many modifications have been made for DI-LPME.In order to overcome these disadvantages,two new liquid-phase microextraction methods have been developed in this work.A new two-phase LPME was applied to the extraction of flumetsulam and its two analogues in soil samples,phenolic compounds in lake;a new three-phase LPME was applied to the extraction phenolic compounds in lake and landfill leachate.After optimized the extraction conditions,the extraction efficiency of our method and that of the DI-LPME was compared,and the results indicated that the proposed methods were promising approaches of sample pretreatment.