Studies On Residue Extrapolation And Group Maximum Residue Level Recommendation Of Four Pesticide In Some Kinds Of Vegetables

Maximum residue limits(MRL)were effective indicator for monitoring the safety of pesticide residues in agricultural products and foods.The MRL establishment was based on lots of residual data,but for crops the limitation of resources,it was impossible to carry out the supervised trial for each crop,especially for some minor crops.It caused serious misuse of pesticides in these crops for few products registered.Based on the crop classification,the representative with similar morphological and residual levels and economic value in the crop group or subgroup were selected to carry out the residue trial,the data obtained could be extrapolated to minor crops in the same group.It is one of the effective ways to solve the pesticide residue data missing problem.In this paper,11 vegetables were selected from four groups including cucurbitaceae vegetables(cucumber,bitter gourd,loofah,zucchini),solanaceous vegetables(tomato,cherry tomato,eggplant),legume vegetables(cowpea,kidney beans)and petiole vegetables(celery and fennel).Four pesticide(bifenthrin,difenoconazole,thiamethoxam and azoxystrobin)residues were compared on these four groups.The possiblility of extrapolation of pesticide residues between crops and recommended Group MRL were studied.The main contents are summarized as follows:QuEChERS-LC-MS/MS and GC-MS method for simultaneously analysis of azoxystrobin,thiamethoxam(metabolite clothianidin),difenoconazole and bifenthrinon in 11 vegetables were developed and validated.Three levels of fortified recoveries performed at 0.005,0.05,and 0.5 mg/kg were between 78.4 and 11.0.3%with a relative standard deviation between 1.1 and 11.4%.The limit of quantifications(LOQs)of four pesticides in 11 vegetables matrices were 0.005 mg/kg.The supervised trials of four pesticides on 11 vegetables were carried out under critical GAP conditions,and the pesticide residue content in the collected samples were determinated using the above method.The initial concentration,half-life,STMR and HR of four pesticides on 11 crops were obtained.The results showed that the azoxystrobin residues were in the range of 0.02-0.11 mg/kg and the thiamethoxam were 0.11-0.24mg/kg(its metabolite clothianidin were 0.05-0.15mg/kg).The difenoconazole were in the range of 0.11-0.18 mg/kg,bifenthrin was 0.20-0.31 mg/kg,and the residual levels were close to different Cucurbitaceae crops(cucumber,bitter gourd,loofah and zucchini).It could be concluded that it was appropriate for them in a same subgroup.From the consumption amount,cucumber could be as a representative crop.Similarly,tomato,eggplant and cherrytomato were suitable in one group.Tomato and eggplant were selected as representative crops.In the legume vegetables group,the residual level of cowpea was close to that of kidney bean,both could be as the representative crop.In the petiole vegetables group,pesticides residue levels in fennel were higher than those in celery.When PHI was 5d,the STMR values of azoxystrobin,thiamethoxam(metabolite clothianidin),difenoconazole and bifenthrin in fennel were 0.13,0.17(0.04),0.21 and 0.49 mg/kg,while the STMR values in celery were 0.11,0.15(0.03),0.18 and 0.49 mg/kg.From the residual level,fennel was more suitable as a representative crop,but considering the planting area,celery was also fit to be the representative crop.The residual level in processed products was greatly affected by raw agricultural commodities.To investigate the residue change in processed products,some samples were collected from the field where 5 times of recommended dosage was sprayed in the cucurbitaceae vegetables.The processing factors were calculated to the washing and drying processing.It was found that the processing factors obtained under the drying conditions of four pesticides could be extrapolated among cucumber,bitter gourd,sponge gourd,and summer squash.For washing,the pesticide residues gradually decreased with the increase of the cleaning time,and the processing factor was in the range of 0.74 to 0.97.After cleaning for 5min,the processing factor was higher than 0.70.It predicted that the difference in the nature of the epidermis did not result to the change of the pesticide residue levels.The standard deviation of cleaning processing factors was less than 5%.It could be concluded that the cleaning processing factors of four pesticides could be extrapolated among cucumber,bitter gourd,loofah and zucchini.Based on the residual data of four pesticides on 11 vegetables,the maximum residue levels of crop group were calculated by OECD calculator and JMPR Report extrapolation method,and then the acute and chronic risk assessments were evaluated.It indicated that the chronic risk quotient RQc of four pesticides and their metabolites in four crop groups were between 0.02 and 7.41%,and there was no chronic dietary risk,the acute risk quotient RQa were between 0.2 and 12.9%,there was no acute risk to the health of consumers.Based on the research and radar chart data analysis,some principles on residue extrapolation and group MRL recommendation were summarized.The research was helpful to promote the MRL establishement of pesticides in minor crop.