| Pesticide plays an important role in preventing and controlling plant diseases and insect pests during the process of vegetable production. However, the pesticide residue problems caused by the improper use seriously affect the quality of the vegetables. It is urgent to study degradation pattern and influence factors of pesticide residue. The experiment methods of degradation of rotenone and dinotefuran residues in different kinds of vegetables were established. The effect of growing environment, colors, degree of maturity, edible parts on the degradation of rotenone and dinotefuran was reported in this study. And a preliminary study on natural antioxidant to delay the residue and degradation of pesticide. These studies will play guidance from the character of biology itself to solve the problem of pesticide residues and complete the trace standard of pesticide.Residues of rotenone in samples were extracted with acetonitrile, cleaned up with Florisil column and determined by high performance liquid chromatography(HPLC) with UV-detector. The limit of quantification(LOQ) of rotenone in the samples was 0.01mg/kg,the average recoveries and coefficient of variations of the method were 85.04%~108.61%, 1.48~8.46%. Dinotefuran was extracted with acetonitrile, cleaned with primary secondary amine(PSA) and graphitized carbon black(GCB) and determined by HPLC. The limit of quantification(LOQ) of rotenone in the samples was 0.05mg/kg,the average recoveries and coefficient of variations of the method were 80.54%~107.04%,1.19~7.62%.These results showed the residue analytical methods were adhered to the requirements of pesticide residues.Digestion dynamics of 2.5% rotenone EC: field experiments was establish to study the degradation dynamics of rotenone residue in amaranth,cabbage,pepper and eggplant.As the results showed that rotenone degradation in vegetables under field faster than vegetable greenhouses and indoor,rotenone degradation in green varieties faster than red,the disintegration of rotenone pesticide and the growth rate of vegetables is positive correlation.The light and rainfall accelerate the degradation of rotenone,but melatonin has delayed effects for rotenone dissipation.Digestion dynamics of 20% dinotefuran SG: field experiments was establish to study the degradation dynamics of dinotefuran residue in cabbage,pepper and tomato. As the results showed that dinotefuran degradation in cabbage with root-irrigation application had slowly half life compare spray application.The dinotefuran degradation on tomato in growth stage was fater than mature period,the dinotefuran residue in peel was higher than pulp. The dinotefuran residue at different edible parts has difference.2.5% rotenone EC in cabbage and pepper in the final residue test: the effects of spraying concentration, spraying times and vegetable color on rotenone residues in harvest period were studied. After spraying 3 to 4 times with recommend dose and the recommended dose of 2 times. Results showed: 3 days after application, the rotenone residue in red cabbage was 0.505 mg/kg to higher than the State formulates the MRL values. Pesticide residues in vegetable greenhouses planting were higher than outdoor planting. The 6 days safe interval was suggested of rotenone application in cabbage.According to the results of this study, we should take the maximum instead of mean value when estimate pesticide residue on vegetable harvesting to avoid the pesticide residue exceeding standard in the part of vegetables. Delay 1day for harvest when applied rotenone EC on red cabbage and extend interval days on greenhouse planting.Considering the MRL value of dinotefuran in cabbage in Japan and the intake of cabbage in our country,the MRL value of dinotefuran was suggested as 1 mg/kg with 5days safety interval after application. |
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