Sample Preparation Techniques In The Analysis Of Pesticide Residues In Tea With Chromatographic Determination

China has the largest area of tea plantation and thus is one of the largest tea exportersin the world. Since more and more maximum residue limits (MRLs) for the pesticide intea from exporting countries were established, pesticide residues in tea has been a clog tothe export. Therefore, development of fast and sensitive methods for pesticidemultiresidue analysis in tea is of great significance. The analysis of pesticide residues intea is usually difficult owing to the matrix interference from tea samples, which containcomplex components including pigments, greases, etc. Thurs sample preparationtechniques are all-important for the determination of pesticide residues in tea.The thesis consists of the following four parts:In the first part, there was a summarization about pre-treatment methods of thepesticide residues in tea, especially about solid phase extraction (SPE), solid phasemicroextraction (SPME) and so on. In addition, detection technologies including gaschromatography (GC), gas chromatography-mass spectrometry (GC-MS),high-performance liquid chromatography (HPLC) were also introduced. Finally, researchcontent and working significance in this thesis were summarized.In the second part, a method using SPE-GC for simultaneous determination oforganochlorine and pyrethroid pesticide residues in tea was established. The analyteswere extracted by sonication-assisted extraction (SAE) and then purified using self-madeFlorisil/PestiCarb SPE cartridges. At the spiked level of4.93~201.00ng/g, therecoveries for most pesticides were between68.9％~112.2％. The relative standarddeviations were less than15.8％and the limits of detection reached2.52ng/g. Thismethod is suitable for the determination of pesticide residues in the tea samples forexport.In the third part, SPME pre-treatment technique combined with GC-MS was usedfor the determination of pesticide residues in tea. With the self-made single-walled carbonnanotubes SPME coating fiber, the conditions of extraction and adsorption wereoptimized in details. Method precision was satisfactory and detection limits at thepicogram per millilitre level were achieved. Compared to other pre-treatments, this method has more advantages including low solvent-consumption, less time andnonspecific instrument demanded.In the last part, a method has been developed for the determination of6pesticideresidues in tea using SPME pre-treatment technique combined with HPLC. A newpoly(1-hexadecene-co-TMPTMA) SPME coating fiber has been prepared and applied toextract pesticides in tea samples for the first time. This SPME fiber showed highextraction efficiency of pesticides along with good solvent resistance. The linear rangeswere between1.7~500ng/mL and the limits of detection reached ng/mL level. Thedetection limit, precision and recovery of this method can meet the requirements ofroutine analysis of pesticide residues in tea.