Determination Of Pesticide Residue Using Liquid Phase Microextraction

This thesis mainly researched two detection methods to detect organophosphorus pesticides residues in the samples.These two methods are dispersed liquid phase microextraction and ultrasound-assisted liquid phase microextraction.A rapid and sensitive method based on dispersive liquid-liquid microextraction(DLLME)and gas chromatography-flame photometric detection(GC-FPD)has been successfully applied to the determination of organphosphorus pesticides residues(OPPs)in apples.The factors that influenced the extraction were optimized in the experiment.The optimum conditions:5.0mL apple sample was placed in 10.0mL centrifuge tube,then the mixture of 1.5mL acetone(disperser)and 30?L 1,2-dichlorobenzene(extracter)was injected into the sample solution rapidly.Vibrate for 1 minute then centrifuge at the rate of 3500r-min-1 for 5minutes,the extract phase was sedimented at the bottom of the centrifuge tube,transfer 1?L to GC system for analysis.Under the optimum condition,based on signal-to-noise ratio(S/N)of 3,limits of detection ranged form 1.32 to 3.58?g·mL-1.The relative relative standard deviations(RSD,n=3)were between 11.06 and 15.39%.Correlation coefficients varied from 0.9773 to 0.9976.The developed method was successfully applied in the analysis of apple samples.In order to evaluate the matrix effects of the samples,organophosphorus pesticide was added to the apples by using three different concentrations.The recoveries were ranged from 64.0%to 89.0%,and no matrix effect was observed.The results show that the method is comparatively simple,fast and effective.The process of the ultrasound assisted liquid phase microextraction(USALPME)combined with Flame Photometry Detector gas chromatography,a new method is used to detect three kinds of organophosphorus pesticides.Sumithion,chlorpyrifos,fenamiphos which are included in potable water.The factors that influenced the extraction were optimized in the experiment.In a centrifugal test tubes with 5mL water,and the 30 ? L chlorobenzene(extraction solvent)were injected into the test tubes quickly.Then keep these tubes to the ultrasonic bath 10 min,ice bath 10 min,centrifuge at the rate of 3500 r·min-1 for 5 min.Finally,1.0?L of the extractant was injected into GC for analysis.In the optimum condition,three pesticides limits of detection ranged from 0.41 to 0.83?g·mL-1,the relative standard deviations were between 11.94%and 16.73%,the correlation coefficients varied from 0.9957 to 0.9997.