| Tomato(Solanum lycopersicum L.)is the largest vegetable crop in the world.China is one of the major tomato producing countries,and its output accounts about 1/3 of the world.Tomato fruits are rich in carbohydrates,organic acids,lycopene,carotene,vitamin C and other nutrients.They are suitable for both fresh food and tomato paste and juice products,and have high nutritional value and high added value.But the disease and insect pest of tomato is an important factor affecting the production and management benefit of tomato.The prevention and control of diseases and pests is mainly based on the application of various chemical pesticides.The extensive,large and long-term use of chemical pesticides is easy to cause the increase of pesticide residues in tomatoes and the increase of insecticide resistance.In this paper,a Qu ECh ERS-UPLC-MS/MS method was established for rapid detection of tomato and soil of thiamethoxam and its metabolite(clothianidin),spirotetramat and its four metabolites(BYI08330-enol-glucoside,BYI08330-mono-hydroxy,BYI08330-enol and BYI08330-ketohydroxy)residues,storage stability of the 7 kinds of pesticides in tomato were studied,researched 30% spirotetramat and thiamethoxam residue in tomato and soil degradation dynamics and final residues of pesticide residue,and through the calculation of data analysis of spirotetramat and thiamethoxam pesticides on human chronic and acute risk,studied 30% spirotetramat and thiamethoxam different concentration,different times of application on tomato quality,the soluble solids,vitamin C,flavonoids,carotenoids and other quality.They were aimed at providing a scientific basis for the safety of the use of the compound pesticide of spirotetramat and thiamethoxam.The main results are as follows:1.Qu ECh ERS-UPLC-MS/MS method was established for rapid detection of spirotetramat and its four metabolites(BYI08330-enol-glucoside,BYI08330-mono-hydroxy,BYI08330-enol and BYI08330-ketohydroxy),thiamethoxam and its metabolites(clothianidin)in tomato and soil residues.The residues in samples were extracted with acetonitrile,removed the water with anhydrous magnesium sulfate and sodium chloride,then the extract was purified by primary secondary amine(PSA)sorbent and C18,and detected by ultra-performance liquid chromatography-tandem mass spectrometry(UPLC-MS / MS)under the multi-reactive ion monitoring mode(MRM)with external standard method.The results showed that the method has good linearity(r2?0.9992)when the concentrations ofthiamethoxam,clothianidin,spirotetramat,BYI08330-enol-glucoside,BYI08330-mono-hydroxy,BYI08330-enol and BYI08330-ketohydroxy were ranged from 0.2 to 2000 ?g/L.The limit of quantification(LOQ)of was 0.002 mg/kg in tomatoes.When the fortified levels in tomatoes were ranged from 0.002 to 2.00 mg/kg,the average fortified recoveries were in the range of 79.9% to 104% and the relative standard deviations were 0.94% to 6.4%.The limit of quantification(LOQ)of was 0.02 mg/kg in soil.When the fortified levels in soil were ranged from 0.02 to 2.00 mg/kg,the average fortified recoveries were in the range of 70.9% to 92.5% and the relative standard deviations were 1.0% to 5.1%.The method is rapid and simple with high sensitivity and good reproducibility,which is suitable for determination of thiamethoxam,clothianidin,spirotetramat and its four metabolites residues in tomatoes and soil.2.The storage stability tests of thiamethoxam,clothianidin,B-glu,B-mono and B-keto were added to the blank tomato samples.The results showed that the 5 kinds of pesticides were stable in storage period of 24 weeks,and the pesticides were almost not degraded during the first 8 weeks' storage period.In addition to the rapid degradation of thiamethoxam,the overall gap of other pesticide degradation was not significant.The stable storage data of spirotetramat and B-enol in tomato found in EFSA showed that the stability of spirotetramat and B-enol in tomato could be up to 18 months.In summary,the shortest storage period of 7 pesticides in tomatoes is 24 weeks.As long as the actual sample from the sample to the end of the test is not more than 24 weeks,it shows that the test data is reliable.3.The residue digestion test of spirotetramide and thiamethoxam pesticides was conducted in 2015 and 2016 in Beibei district of Chongqing municipality,Beijing and Fanchang county of Anhui province.The results showed that the degradation of the two insecticides met the first-order kinetic model.The speed of digestion of spirotetramat in tomato and soil was similar.The half-life of digestion in tomato was 3.0-9.8 d,and the half-life in soil was 4.2-5.6 d.The dissolution rate of thiamethoxam in tomato and soil was quite different.Among them,the digestion rate in tomato is faster and the half-life is 4.6 to 11.7 days.Digestion in the soil is slower and the half-life is 13.1 to 17.8 days.4.Field trials of the final residue of spirotetramidine and thiamethoxam suspension in tomato and soil were in Chongqing,Beijing and Anhui for two years.The test results show that,under the premise that all pesticides do not exceed the stipulated MRLs,it is recommended that the pesticide be applied at low doses(45 g ai/hm2)three times with a safety interval of 7 days.Chronic risk quotient and acute risk quotient were calculated from the maximum residue data of pesticides in tomato.The results showed that the average long-term chronic risk of spirotetramat and B-enol was 0.838%,and the average long-term chronic risk of spirotetramat and its four metabolites was 1.370%.The average short-term acute risk of spirotetramat and B-enol was 0.280%,and the average short-term acute risk of spirotetramat and its four metabolites was 0.625%.Thiamethoxam(including clothianidin)has an average long-term chronic risk of 0.710% and an acute short-term risk of 1.573%.That is,the use of the spirotetramat-thiamethoxam mixture does not pose any chronic or acute risk to humans.5.The application of 30% spirotetramat-thiamethoxam pesticides will affect tomato soluble solids,vitamin C,flavonoids,and carotenoids.According to the test results,the relatively high concentration of low concentration and less frequent application of multiple times will significantly increase the quality of most of the tomato fruit parameters.However,the effect of this law is not yet clear,it need to increase the amount of samples and test areas.The significance of the P value at the 0.05 level was analyzed by the data and the results showed that there was no significant difference in all the data. |
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