| Ginseng as a valuable Chinese herb which planting area is very large in China, exports accounted for first in the world, but the economic benefits are very low. The main reason is the problem of pesticide residues. Unreasonable use of pesticides in the process of ginseng pest control, not only pollute the environment, and ecology have been seriously damaged, more serious, China ginseng had bad reputation and low competitiveness in the international market for excessive pesticide residues in ginseng, eventually lead to lower output value of China’s ginseng. So it is of great significance that studying on the use of pesticides technology, regulating the use of pesticides, establishing the use standard of pesticides in ginseng and residual limits as soon as possible for improving the quality of ginseng products in China, enhancing the competitiveness of Chinese ginseng in international market, and promoting China’s ginseng industry toward green and sustainablethe direction of development. Pyrimethanil is one of the most effective and commonly used for controlling ginseng gray mold which is caused by Botrytis cinerea. In this study, LC-MS/MS method was used to study dynamics and the final residue of pyrimethanil in ginseng root, stem and soil so that laid the foundation for the safe use techniques and residual standard-setting of pyrimethanil in ginseng. This dissertation is mainly concerned with the following aspects:1. LC-MS/MS method was established for the determination of pyrimethanil in the ginseng root, stem, leaf and soil. Samples for this study were extracted with acetone and purified with ProElut GPR solid phase extraction column and determined by LC-MS/MS method. The analysis was carried out in the multiple reaction monitoring (MRM) mode by employing the external standard method. The calibration curve was linear (R2=0.9985) in the range of0.01μg/mL～0.5μg/mL The limits of detection (LOD) for pyrimethanil were0·01mg/kg. The recoveries of the method for pyrimethanil varied between85.7%and94.5%at spiking levels of0.01-0.2mg/kg, the relative standard deviations varied from3.11%to8.12%. The average recoveries and the relative standard derivations (RSDs) of pyrimethanil could meet the requirements for the detection of residues.2.Residual decline and final residues of Pyrimethanil40%SC in ginseng and soil were studied. Spraying at a dose of1000g a.i./hm2and one time in one season, original deposition of Pyrimethanil were0.2043mg/kg in ginseng root,0.6809mg/mg in ginseng stem,0.9362mg/mg in leaves and0.2679mg/kg in soil,respectively. Half-life were1.4d in ginseng root,1.7d in ginseng stem,9.4d in ginseng leaves and2.2d in soil, respectively; Spraying at a dose of1000g a.i./hm2and two times in one season, Pyrimethanil original depositions were0.6085mg/kg in root,0.9574mg/kg in stem,0.9787mg/mg in leaves and0.3617mg/kg in soil, respevtivelly. Half-lifes were1.2d in roots,1.7d in stems,1.8d in leaves and2.6d in soil, repectivelly.Spraying at a dose of2000g a.i./hm2and one time in one season, original depositions of Pyrimethanil were0.2979mg/kg in roots,0.7872mg/mg in stems,1.0426mg/mg in leaves and0.2766mg/kg in soil, respectively. Half-lifes were1.4d in roots,1.7d in stems,3.1d in leaves and3.0d in soil, respectively; Spraying at a dose of1000g a.i./hm2and two times in one season, original depositions of Pyrimethanil were0.7447mg/kg in root,1.0000mg/mg in stem,1.0213mg/mg in leaves and0.3830mg/kg in soil, respectively. Half-lifes were1.4d in roots,1.8d in stems,5.4d in leaves and2.8d in soli, respectivelly.Results for residual dynamic test showed:the degradation trends of Pyrimethanil in ginseng root, stem, leaf and soil were line with a kinetic equation of Ct=C0e-Kt, half-lifes of Pyrimethanil in roots, stems, leaves and soil were between1.2d and9.4d, and were relatively short (T1/2≤30d). Pyrimethanil is readily biodegradable pesticide.Results for final residual tests showed that:spraying at a dose of1000g a.i./hm2and one time in one season and collection at spraying28d,35d later and harvest, residues in ginseng root were0.0234mg/kg,0.0138mg/kg, and0.0015mg/kg, respectively, residues in stems were0.0660mg/kg,0.0468mg/kg and0.0109mg/kg, respectively, residues in leaves were0.7660mg/kg,0.5532mg/kg and0.5106mg/kg, respectively, residues in soil were0.0532mg/kg,0.0340mg/kg and0.0194mg/kg, respectively; Spraying two times in one season, residues in roots were0.0200mg/kg,0.0153mg/kg,0.0068mg/kg, respectively, residues in stems were0.1170mg/kg,0.0745mg/kg and0.0617mg/kg, respectively, residues in leaves were0.8085mg/kg,0.6838mg/kg and0.0049mg/kg, respectively, residues in soil were0.0723mg/kg,0.0681mg/kg and0.0319mg/kg, respectively.Spraying at a dose of2000g a.i./hm2and one time in one season, Application rate of2000g. ai/hm2and collection at after spraying28d,35d later and harvest, residues in roots were0.0277mg/kg,0.0123mg/kg and0.0043mg/kg, respectively, residues in stem were0.0745mg/kg,0.0638mg/kg and0.0170mg/kg, respectively, residues in leaves were0.8723mg/kg, 0.4894mg/kg and0.0702mg/kg, respectively, residues in soil were0.0596mg/kg,0.0574mg/kg and0.0383mg/kg, respectively; Spraying two times in one season, residues in roots were0.0340mg/kg,0.0189mg/kg and0.0111mg/kg, respectively, residues in stems were0.1064mg/kg0.0809mg/kg and0.0234mg/kg, respectively, residues in leaves were0.7447mg/kg,0.5532mg/kg and0.2766mg/kg, respectively, residues in soil were0.0851mg/kg,0.0702mg/kg and0.0319mg/kg, respectively.When the sprayed doses were1000and2000g a.i./hm2, all residues of Pyrimethanil in root, stem of ginseng and soil were much less than the MRLs of Korean (1.0mg/kg) at harvest. Reference to South Korea, EU and other countries, MRLs of Pyrimethanil in the ginseng root and soil were proposed to be of1.0mg/kg based on integrated considering including results of field trial and residual dection at a dose of2000g a.i./hm2and application two times in one season, the safe intervals should be14d in ginseng, the proposed MRLs value was tentatively scheduled for0.7mg/kg. |
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