| The pre-treatment of the samples has a decisive role in the whole sample analysis,especially for the analysis of complex sample matrix, and it has a direct impact on theresults of the analysis. Therefore, the development of a rapid, efficient, sensitive andenvironmentally friendly sample preparation technique has been the the goal which theresearchers to pursue. In recent years, the questions about pesticides residue exceedingstandard the excess pesticide were widely supposed to concerned by governments andall circles society. Due to excessive use of various pesticides or the illegal use, thephenomenon of food poisoning caused by excessive pesticide residues has happenedfrequently. In order to ensure the health and safety of the people, the Governmentsrequirements for pesticide residue limits are more stringent, so it is very important toestablish a kind of effective way to monitor the pesticide residues in environmental andfood matrices. Solvent-free microwave-assisted extraction (SFME) increases theextraction rate by using microwave radiation which can heat something evenly and hasstrong penetration; meanwhile, SPME method doesn’t need to add any organic solvents.This method has the advantages of convenient, a wide range of application, not using oforganic solvents, high extraction efficiency, time-saving, environmental protection andso on. The liquid-phase micro-extraction was based on a miniaturized liquid-liquidextraction and the use of solvent was the level of microliter or nanoliter. The basicprinciple of LPME is that the balance between the sample and the extraction solvent. Itcombines extraction, concentration and sampling together as a whole, and has beenconsidered to be a high sensitivity, fast, simple and low-costing sample preparationmethod. In this paper, a new sample pretreatment technology based on the SPME andLPME has been developed, and combined this new method with High PerformanceLiquid Chromatography (HPLC) to rapidly analyze the volatile or semi-volatilepesticide residues in various complex samples matrix. The main contents of this paperare summarized as follows:a) Based on summaring of characteristics of solvent-free microwave-assisted andliquid-phase micro-extraction, the device of SFME-LPME was established in chapter2by coupling microwave oven and the volatile oil extraction devices which have beenchanged and improved. And its performance has been investigated preliminary; theresults show that the devices were able to meet the basic requirements of trace components analysis.b) Dichlorvos in vegetables was selected as study object and has been determinedby the method of solvent-free microwave-assisted-liquid microextraction together withHPLC analysis in third chapter. The factors affecting the extraction (such as the type ofsolvent extraction, microwave radiation power and time, pH value, etc.) were carriedout a series of studies. In optimization conditions, the detection limit (S/N=3) was0.05μg/kg, the average recoveries were ranged from79.3%to98.8%and the methodshows a good linear relationship. Compared with other pre-treatment methods, it hasbeen proved that the extraction technology is simpler, better selectivity, easier to operate,fast and environment-friendly.c) In the fourth chapter, DDT pesticide residue in soil and food was analyzed bySFME-LPME-HPLC technology. Various extraction factors which influenced extractingefficiency, including the type of extraction solvent, extraction time, microwave heatingpower and pH were investigated. Under the optimized conditions, the limit of detection(LOD, S/N=3) and the limits of quantification (LOQ, S/N=10) was0.18μg/kg and0.59μg/kg, respectively. The recoveries of target analyte spiked in real soil sample were87.34%~96.41%. The relative standard deviations (RSDs) were5.75%~6.72%.d) SFME-LPME coupled with HPLC has been used for the determination of HBCresidues in soil and tea. Extraction solvent, microwave irradiation power, extractiontime and so on were investigated. Butyl acetate were extraction solvent, microwaveradiated power of80W, extraction time30s, pH=6. Linear range was from40to800g/L, R2=0.996. The method shows a good linear relationship, the average recovery of78.2%to90.9%. Under the optimized experimental conditions, the method wassuccessfully applied to the extraction of HBC in soil and tea samples. |
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