| Residue analysis method of fenbutatin xoide and spirodiclofen-pyridaben was established in citrus fruits and soil. Base on it, the residue rule of the two pesticides in citrus fruits and soil was studied. The dietary risk of fenbutatin xoide and spirodiclofen-pyridaben in citrus fruits as well as the level of protection for consumers provided by current limits was also studied. The results were shown as follows:The fenbutatin oxide residue in citrus fruits and soil was detected by UPLC-MS-MS. Samples were extracted with acetonitrile (add0.1%acetic acid if the matrix was soil), cleaned up with C18, and then analyzed by UPLC-MS-MS in multiple reaction monitoring mode. The precursor ion/product ion transitions were m/z517.3>461and m/z517.3>194.8at the mode of multi-reaction monitor and m/z517.3>194.8was used for quantification. The limit quantitation of the method and instrument were2.0μg/kg and1.0μg/kg, respectively. The linearity of fenbutatin oxide was satisfied between the ranges of0.001～1.0mg/L. At three spiked levels (0.01mg/kg,0.1mg/kg and0.2mg/kg), the average recoveries in different matrices (citrus pulp, peel, whole fruits and soil) were74.0%～97.7%with relative standard deviations (RSDs) of2.3%～6.9%. The accuracy and precision of the method could meet the requirements for quick qualitative and quantitative analysis of trace fenbutatin oxide residue in citrus fruits.The spirodiclofen and pyridaben residue in citrus fruits and soil was detected by optimized QuEChERS combined with UPLC-MS/MS. The sample was extracted with acetonitriles, cleaned up with PSA, and then analyzed by UPLC-MS-MS in multiple reaction monitoring mode. For spirodiclofen, the precursor ion/product ion transitions were m/z411.1>71.2and m/z411.1>313.0and m/z411.1>313.0was used for quantification. For pyridaben, the precursor ion/product ion transitions were m/z365.1>147.1and m/z365.1>309.1and m/z365.1>309.1was used for quantification. The limit quantitation of method and instrument were2.0μg/kg while1.0μg/kg, respectively. The linear relation of spirodiclofen and pyridaben was satisfied in the range of0.001～1.0mg/L. At three spiked levels (0.01mg/kg,0.1mg/kg and0.2mg/kg), the average recoveries of spirodiclofen and pyridaben in different matrices (citrus pulp, peel, whole fruits and soil) were79.8%～92.6%and81.3-92.5%with relative standard deviations (RSDs) of2.8%～5.2%and2.5%～6.2%, respectively. Residual trial of fenbutatin oxide and spirodiclofen-pyridaben were conducted in Beibei Chongqing, Zhanjiang Guangdong and Wuhan Hubei in2012and2013. The results were shown as follows:Citrus plants and soil were treated with300mg ai/L fenbutatin oxide one time when the fruits were half of the mature size. The residual of fenbutatin oxide in whole fruits decreased gradually after treated and the dissipation kinetics of fenbutatin oxide in citrus was in accord with the first-degree reaction pattern. However, the dissipation kinetics of fenbutatin oxide in soil wasn’t in accord with the first-degree reaction pattern. The results of final residual trial revealed that when the citrus plants was sprayed at2-3times successively at the200mg ai/L and300mg ai/L, the residues mostly distributed in the peel of citrus and all soil was detected with fenbutatin oxide, and30days after treatment some pulp samples did not detected with fenbutatin oxide. Citrus plants were treated with101.25mg ai/L spirodiclofen-pyridaben (18%spirodiclofen and9%pyridaben) one time when the fruits were half of the mature size. The results showed that the degradation rate of spirodiclofen and pyridaben in both citrus fruits and soil followed the first-order kinetics equation C=A-eBt. In the final residual trial, the citrus plants were sprayed at1-2times successively at the concentration of67.5mg ai/L and101.25mg ai/L, about half of the pulp samples that treated at the low concentration did not detected with spirodiclofen or pyridaben.According to residual test results during the two years and the MRLs about fenbutatin oxide, spirodiclofen and pyridaben that established in china and other countries or organizations, the recommended dosage of fenbutatin oxide applied on citrus are100-200mg ai/L, the maximum treatment was2times and the plastochrone between two treatments was10days, and the harvest intervals was recommended at14days. The recommended dosage of spirodiclofen-pyridaben applied on citrus were54-67.5mg ai/L, the maximum treatment was1times and the plastochrone between two treatments was7days, and the harvest intervals was recommended at14days.According to the medium residuals gained form our study and the MRLs about fenbutatin oxide, spirodiclofen and pyridaben that established in china and other countries or organizations. Based on the principle and method on pesticides residue dietary and risk assessments proposed by Joint Meeting on Pesticide Residues (JMPR) an Codex Committee on pesticide residues (CCPR), combined with the 《Dietary Group Cookbook for different Populations in China Consumer》 released by ministry of health in2002, a risk assessment of fenbutatin oxide, spirodiclofen and pyridaben dietary intake was carried out and the results shows that the RQC values of fenbutatin oxide, spirodiclofen and pyridaben were0.066,0.035and0.758, respectively. All the values were less than1, which means that their chronic risk was acceptable. The CPLC values of fenbutatin oxide, spirodiclofen and pyridaben were5.625,25and1.101, respectively. All the values were greater than 1, it indicated that the MRLs standards for them were at an accepttable level. |
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