New Microextraction Technique For The Analysis Of Pesticides Residual

The detection of pesticide residues and food safety problem has attracted an increasing concern of people around the world. To ensure food quality and safety, the key is establishment a fast, accurate and sensitive analysis method for pesticide residues in food. The procedure of pesticide residues analytsis includes two steps:sample preparation and detection. In which, sample pre-treatment plays a great important role. The extraction procedures of pesticide in food are difficult and complicated because of matrix interference. Therefore, we should develop a fast and efficient sample preparation method and couple it to the advanced detection techniques for analysis of pesticide residues in food.In recent years, as one of the most famous sample preparation techniques, solid-phase microextraction (SPME) has been developed rapidly and widely used for the analysis of multi-class pesticides in various complex sample matrices. The method is solvent-free or solventless and ecofriendly, it combines sampling, extraction and enrichment in one step. A variety of different types of SPME have been developed, such as polymer monolith microextraction, monolithic molecularly imprinted polymer microextraction, fiber SPME, solid-phase dynamic extraction (SPDE), microextraction by packed sorbent (MEPS), stir-bar sorptive extraction (SBSE) and so on. In addition, microwave-assisted extraction (MAE) method is another green extraction technique, the sample preparation method is simple, rapid, highly extraction efficiency, energy-saving and safe, it has been widely applied to various fields.In the present work, two novel solid phase extraction methods and a microwave-assisted extraction (MAE) combined with matrix dispersive solid-phase extraction method were proposed and used as novel sample preparation methods. And the methods coupled to GC-MS and LC-MS have been applied to analysis of the pesticides in tea samples and animal feeds. The main study contents are listed as follows:1. In the method, a polypropylene sieve with porous network structure was coated with polydimethylsiloxane (PDMS) as extraction medium. Based on the polydimethyl-siloxane(PDMS)-sieve, a rapid, simple and sensitive sorptive extraction method was established for analysis of five pyrethroids residues in tea samples. The proposed method was optimized and validated, and compared with the conventional stir bar sorptive extraction (SBSE). Finally, the method was used for the determination of pyrethroids in tea samples. The detection limits (LODs) ranged from0.8ng·g-1to19.6ng·g-1. Good repeatability was obtained with the relative standard deviation (RSDs) values lower than9.6%. Furthermore, a satisfactory recovery(81.7-110.6%) was also achieved for the five pesticides studied. And the results indicated that the method is a simple, rapid, low cost and precision technique.2. An ecofriendly, rapid and effective method for the determination and quantification of18pesticides residue in animal feeds was developed, by combining microwave-assisted extraction (MAE) with matrix dispersive solid-phase extraction. In the study, the factors that affecting the extraction efficiency was optimized by coupling it to GC-MS. Under the optimal conditions, the present method was successfully applied to the quantification analysis of the pesticides in animal feeds. The average recoveries (54.3-116.9%) and good repeatability(≤9.9%) were attained.3. A SPME-GCMS method using graphite fluoride as stationary phase of solid-phase microextraction (SPME) has been developed for the determination of a mixture of pyrethroids in different tea samples. Different factors of the method affecting the extraction efficiency were evaluated, such as the mass of graphite fluoride, ionic strength and sample pH, the flow rate of sampling, kind and volume of desorption solvent, the flow rate of desorption. The method was validated using tea samples spiked with pesticides at different concentration levels under the optimized conditions. The detection limits (LODs) of five pesticides were in the range of2.5-21.9ng·g-1. And the satisfactory recoveries of the proposed method ranged from80.2%to118.5%. The new SPME procedure has been successfully applied to analysis of pyrethroids in real tea samples.