| Castanea mollissima Blume was Castanea in the Fagaceae family. In recent years, the cultivation area of Castanea mollissima Blume in China had expanded rapidly and the output had also increased. The cultivated area had reached 1.25 million hectares, which was 38% of the world total cultivated area. Its total output was about 825,000 tons, accounting for about three-quarters of the world total.In the production process of Castanea mollissima Blume, insect pest occurs rampantly. It causes trees growth weak, yield and quality reduce. Furthermore, it can make trees lifespan reduce and even die. Thus seriously impact on the value of the goods and the exports. Therefore insect pest had became an important limiting factor to improve the production and quality of Castanea mollissima Blume. To ensure its production and quality, a large number of pesticides were applied to control pests, which causes serious pesticide residues pollution and even endanger people's health. So it was very necessary to build analysis methods of pesticide residues in Castanea mollissima Blume.Thiophanate-methyl, Tebuconazole, Prochloraz and Flusilazole are widely used in Castanea mollissima Blume growth process. In this paper, the above four fungicides in Castanea mollissima Blume were extracted, purified, and determined by HPLC. The details are as follows:1. Establish a rapid sample pre-treatment method of pesticide residues in Castanea mollissima Blume.Castanea mollissima Blume belongs to nuts. It has low grease content and high starch content. Its protein content was generally 4%~5%, and pigment content was not much. Combining with the characteristic of pesticides, we made this study. We used methanol as solvent in sample pretreatment process, which reduced the solubility of starch and protein. The extract didn't need purification. After membrane filtration, HPLC analysis was carried out. The HPLC analysis spectrogram showed rarely chromatographic baseline noise, suggesting that the method was feasible. Due to the simplification of pre-treatment steps, the analysis rate was greatly improved. The recovery experiment was carried out and average recoveries of the four pesticides were 78.8%~96.6% with the spiked concentration at 0.05,1.0,10.0mg/kg, and the RSD of the determination were 1.7%~13.9%. It indicated that the method had a good precision and accuracy to achieve the requirements of trace analysis. 2. Establish a HPLC UV detection method for Thiophanate-methyl, tebuconazole, Prochloraz and flusilazole.Chromatographic column: Hypersil ODS(4.6mm×150mm,5μm) made by Dalian Elite Analytical instruments Co, Ltd.Mobile phase: For tebuconazole and Prochloraz, methanol and water volume ratio was 7:3. For Thiophanate-methyl and flusilazole, methanol and water volume ratio was 6:4; Mobile phase flow rate: 1mL/min; Detection wavelength was 225nm. Column temperature was 25℃. The injection volume was 20μL.At concentration of 0.1~10mg/L range, the four pesticides had good linear relationships (R2≧ 0.99). Detection limits were 0.063~0.091mg/kg, which satisfied the requirements of analysis.This method had the advantages of easy to pretreat and fast to perform. It could meet the demands of pesticide residues analysis. It was unnecessary to purify, so the sample pretreatment steps had been simplified and the analysis time had been saved. It operates accurately and efficiently. In addition, we used less organic solvent in pretreatment process, which was very economical and environmentally friendly. It provided technical support for Castanea mollissima Blume on its production safety and the determination of pesticide residues in export products. |
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