| In recent years, with the rapid development of agriculture and forestry, more and more pesticide residues in all kinds of plants, animals and nature have become a threat to the ecological balance and an invisible killer to human health. In today’s advocation of environmental protection and green life, to establish a reliable, rapid and sensitive detection method of pesticide residues is imminent. High performance liquid chromatography(HPLC) is an important branch of chromatography and a significant analytical method of pesticide residues determination, using high pressure infusion system with liquid as mobile phase. The single solvent of different polarity or the mixed solvent of different proportions and mobile phase are pumped into the column containing the stationary phase, then the separated components are detected by the detector. The phase is normal phase chromatography when the polarity of the stationary phase is greater than the mobile phase and vice versa for reverse phase chromatography. Reverse phase chromatography is the most widely used in modern liquid chromatography, accounting for about 80% HPLC applications, mainly used to separate non-polar or less polar compounds.In order to improve the sensitivity of detection, we used chromatographic separation method and fluorescence detector to analysis the components. But most pesticides do not contain fluorescence groups or fluorescence intensity, therefore they can not reach to the requirement. So they need a specific fluorescence reagent reacted with them, in order to connect to the target molecule fluorophore, thereby measuring the fluorescence derivatives. Based on the above problems and pre-column derivatization, these jobs were carried out in this thesis, as follows:Using 4-Chloro-7-nitro-1,2,3-benzoxadiazole(NBD-Cl) as derivatization reagent to react with glyphosate(GLY) and aminomethylphosphonic acid(AMPA). And the derivatization products were detected by high performance liquid chromatography and fluorescence detection(HPLC-FLD). In order to maximize sensitivity, the derivatization and chromatography conditions were optimized. The limit of detection was 24.20 μg/L and 16.80 μg/L for GLY and AMPA under optimum conditions, respectively. Then the ultrasound-assisted extraction method was compared with HPLC-FLD to obtain high valuable compounds in tea for the purpose of proving the practicability of this technology. The calculated recoveries were 82.50%~121.90% for GLY and 88.78%~116.44% for AMPA.A simple and rapid procedure has been developed and validated to measure glyphosate(GLY), glufosinate(GLU) and aminomethylphosphonic acid(AMPA) based on HPLC-FLD. Due to the lack of chromophore or fluorophore groups in the structure of these compounds, the determination was done by HPLC after pre-column derivatization with 9-fluorenylmethyl chloroformate(FMOC-Cl). In order to get the best derivatization conditions, we explored some derivatization conditions and separation conditions. Finally, the limits of detection of the method were 1.80 μg/L for GLY, 3.72 μg/L for GLU, 1.40 μg/L for AMPA, and the recoveries were 96.36%~118.33%, 85.03%~104.05% and 98.00%~111.74%, respectively.The reaction of 5-(4,6-dichlorotriazinyl) aminofluorescein(DTAF) with carbofuran have been studied by HPLC-FLD method. In order to improve the sensitivity, the hydrolysis time and temperature of carbofuran, derivatization reaction conditions such as time, p H and chromatographic separation conditions were optimized. The detection limit of carbofuran was 0.20 μg/L under optimum conditions. A solid-phase extraction(SPE) method was used to extract four samples of vegetables and fruits before derivatization and the spiked recovery was 88.00%~105.21% for carbofuran. |
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