Application Of Dispersive Liquid-liquid Microextraction Coupled With High Performance Liquid Chromatography In The Analysis Of Pesticide Residues

The quality and safety of fruit and vegetables is crucial to human's health,The Presence of Pesticide residue in fruit and vegetables has become one of the serious questions that has extremely attracted government and organization's concerns.As the maximum residue levels of pesticides adopted by the legislation in the world become more and more heavy-handed, it is very significant to form simple, fast and efficient analytical methods.Traditionally, in the screening of pesticide residues in environmental samples, liquid-liquid extraction(LLE) is the classical method for pesticide extraction and preconcentration, but it is time-consuming tedious,laborious and requires large amounts of toxic organic solvents, which have a great threaten on human health and environmental protection. accordingly,solvent- free extraction as a promising technique for sample preparation and pretreatment has become one of the most important research areas in modern analytical chemistry and caused much attention recently.More recently, efforts have been placed on miniaturizing the LLE extraction procedure by extraordinary decreasing the solvent to aqueous phase ratio, leading to the development of liquid-phase microextraction (LPME) methodology. DLLME is based on the distribution effect of the analytes between a microdrop of organic solvent and aqueous sample solution. In LPME,analytes were extracted from small volume of samples to only microlitre even nano- litre organic solvents.This technique belongs to the green analytical technique and is suitable to the development of modern analytical science.lt combines extraction, preconcentration and sample introduetion in one step,and proved to be a simple,fast and low- cost sample preparation method.This dissertation focused on the studies of analytical methods on pesticide residue of Carbamate Pesticides. After grading-up the analytical conditions of Dispersive Liquid-liquid Microextraction Method Coupled With HPLC, the method for the residue determination of pesticides in fruit and vegetables have been established. The dissertation consisted of three fraction.In the first fraction, The development history and toxieology theory of pesticides were simply intro-duced. Current Progress of multiclass pesticide residue analysis in fruit and vegetables were summarized with emphasis on various detection methods for pestieide residue.Finally, the idea and plan of this dissertation as well as the aim and content of the research work was also dissussed.In the second fraction, a novel method for the determination of Carbamate Pesticides residues in tomato Samples by dispersive liquid—liquid microextraction (DLLME)coupled with HPLC-fluorescence detector was developed. Some basilic Parameters that effect the extraction efficiency, such as the kind of the extraction and disperser solvent, their volume and the extraction time, Were investigated.Under the optimum conditions, as high as20.4to24.3-fold enrichment factors were achieved. A good linear relati-onship was obtained in the range of 50～500μg/kg of the analytes with the correlation coefficients (r) of 0.9977～0.9998 and the detection limits of 8.0～20.0μg/kg(S/N=3:1), depending on compounds. This method has been successfully applied for the determination of pyrethroid pesticide residues in real tomato Samples and tomato's leaf with satisfaetory results. The recoveries ranged from 79.1%～to 98.6% and the relative standard deviations fell between 3.5% and 8.5%.In the third fraction, A new method for the determination of four carbamate pesticides in grape samples has been developed using ionic liquid-based dispersion liquid phase microextraction coupled with high performance liquid chromatography,The influence of extraction partemeters including concentraction of buffer solution, the PH of buffer solution, extraction time ect was investigated. The proposed method provided enrichment folds of 317,430,545 and 625 for Aldicarb, Carbofuran, Carbaryl and Isoprocarb. The method have good linear range of 0.01-10μg/mL and the limits of detection of the four pesticides were in the range of 0.12～0.43μg/L, S/N=3. The RSD of samples were 5.4%,5.3%,5.5% and 5.4%.