| Conventional sample preparation methods, such as liquid-liquid extarction and solid phase exrtaction, are time- and solvent- consuming and often involve several complicated procedures. In 2006, Assadi and co-workers developed a novel liquid-phase microextraction technique, named dispersive liquid-liquid microextraction (DLLME). The method is based on the use of a ternary component solvent system. The advantages of DLLME method are environmental friendliness, simplicity of operation, rapidity, low-cost, high-recovery and high enrichment factor.In the first part of this thesis, the progress of the analytical methods for pesticides and sample pre-treatment technologies are summarized. A detailed review concerning the development of DLLME and its applications are presented.In the second part, a novel method for the determination of pyrethroid pesticide residues in water samples by dispersive liquid-liquid microextraction (DLLME) coupled with capillary gas chromatography with electron capture detection (GC-ECD) was developed. Some important parameters that influence 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 as 708 to 1087-fold enrichment factors were achieved. Usingα-benzene hexachloride as the internal standard, a good linear relationship was obtained in the range of 0.8～600μg/L of the analytes with the correlation coefficients (r) of 0.9990～0.9999 and the detection limits of 0.10～0.04μg/L (S/N= 3:1), depending on compounds. This method has been successfully applied for the determination of pyrethroid pesticide residues in real water samples (tap water, well water and river water) with satisfactory results. The recoveries ranged from 76.0% to 116.0% and the relative standard deviations fell between 3.1% and 7.2 %.In the third part, a new method was developed for the determination of fungicides in apples by DLLME coupled with GC-ECD. Some experimental parameters that influence the extraction efficiency were studied and optimized to obtain the best extraction results. Under the optimum conditions, high enrichment factors were achieved ranging from 824 to 912 for the compounds. The recoveries of fungicides in apples at spiked levels of 20.0μg/kg and 70.0μg/kg were 96.0%～103.0% and 96.7%~99.1%, respectively. The limits of detection were in the range between 6.0 and 8.0μg/kg (S/N =3:1). The linearity of the method ranged from 10 to 100μg/kg for the three fungicides, with the correlation coefficients (r) varying from 0.9996 to 0.9999. The obtained results showed that the DLLME combined with GC-ECD could satisfy the requirements for the determination of fungicides in apple samples.In the fourth part, a simple and rapid dispersive liquid-liquid microextraction technique (DLLME) coupled with capillary gas chromatography with electron capture detection (GC-ECD) was developed for the extraction and analysis of fungicides from grape samples. Some important parameters that affect the extraction efficiency of DLLME, i.e., the type of extraction solvent, the kind and volume of disperser solvent, extraction time, were studied systematically. Under the optimum conditions, the enrichment factors and extraction recoveries were ranged between 788~876 and 92.3%～106.1%, respectively. The linear range was 10～150μg/kg and the limits of detection were between 6.0 and 8.0μg/kg (S/N = 3:1) for the three fungicides, with the correlation coefficients (r) varying from 0.9990 to 0.9995. Some grape samples were successfully analyzed using the proposed method.
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