QuEChERS-气相色谱-串联质谱法测定结球甘蓝中甲基毒死蜱农药残留不确定度评估

目的对QuEChERS-气相色谱-串联质谱法测定结球甘蓝中甲基毒死蜱农药残留进行不确定度评估。方法运用气相色谱-串联质谱法对结球甘蓝中甲基毒死蜱残留量进行测定,通过建立数学模型,分析测定过程的主要不确定度来源,对各个分量进行评估。结果不确定性的主要来源是标准溶液的配制、工作曲线的拟合及加标回收率引入。当甲基毒死蜱的残留量为0.041 mg/kg时,扩展不确定度为0.003 mg/kg (k=2)。结论该方法适用于气相色谱-串联质谱法测定甲基毒死蜱残留量的不确定度分析,可为农药残留测量结果的准确性提供科学可靠的依据。     

Modelling biological efficacy decrease and rate of degradation of chlorpyrifos-methyl on wheat stored under controlled conditions

Insecticide residue degradation and pest survival were observed in wheat treated with a low dose of chlorpyrifos-methyl. Treated wheat was stored in small batches at three controlled temperatures and two levels of moisture content of grain, in equilibrium with r.h. in order to stabilise the water activity in the grain during a storage period of 126 d after insecticide application. Every 3 weeks, samples were taken from treated and untreated control grain in each storage condition. Chlorpyrifos-methyl residues declined regularly with time of storage and an exponential negative regression was fitted with high correlation coefficients in most situations of storage temperature and grain water activity (Aw). A multivariate model to show the respective influence of controlled variables involved in the model of residues breakdown (time, Aw, and temperature) was built up through a multiple regression. This model showed the respective importance of the water activity of grain kernels, temperature and formulation of chlorpyrifos-methyl and their combinations on the decline of residues. Simultaneously, the effectiveness of the residues was checked through bioassays with two target species: Sitophilus oryzae and Tribolium castaneum. Taking into account the intentionally low initial applied dose of chlorpyrifos-methyl, the period after application achieving complete kill of the two test insects was rather short and did not exceed 105 d for S. oryzae in the best conditions for control, i.e. low moisture content and temperature. For high Aw (0.8) and storage temperature 30°C, T. castaneum was effectively controlled (more than 95% kill) only on the day after the treatment, survival occurring at the next test date 21 d after the application. High moisture content and temperature and their interactions were the main variables influencing the decrease in the biological effectiveness with time. The concentration threshold for insect survival was slightly below 1 ppm chlorpyrifos-methyl and was influenced by storage and grain conditions. Implications of these findings on storage pest management practices and on the ability to predict the period of biological effectiveness of residues of chlorpyrifos-methyl are discussed.     

Experimental determination of pesticide processing factors during extraction of seed oils

ABSTRACT

Processing Factors (PFs) reflect the concentration or dilution of pesticide residues resulting from food processing. PFs are key elements to demonstrate the compliance of processed foods with Maximum residue levels (MRLs) as set by Regulation 396/2005. While efforts have been made by the European Food Safety Authority (EFSA) and by national authorities to compile PFs from processing studies, such PFs are not available for all pesticides/processed product combinations. The EU vegetable oil and proteinmeal industry association (FEDIOL) has therefore developed a theoretical approach to approximate MRLs in crude vegetable oils and fats, based on the partition coefficient (log P_ow) of the pesticides and on the oil content of the raw materials. To substantiate this approach, a pilot-scale processing study was initiated with rapeseeds spiked with selected pesticides and the experimental PFs for these pesticides determined. The aims of this study were (i) to study the reliability of pilot-scale conditions for PF determination and (ii) to assess the experimental PFs obtained in comparison to the theoretical PFs proposed by FEDIOL. This study demonstrated that production yields obtained for crude oil and meal in this processing study are similar to those in industrial processes even if differences were observed in the individual production steps (mechanical or solvent extraction steps). The experimental PFs obtained confirmed that the chosen fat-soluble pesticides did concentrate in the oil fraction. For metalaxyl-M having a log P_ow lower than 3, a partitioning between the oil and the meal was observed, as expected. By comparing the experimental PFs and theoretical PFs, it can be concluded that the FEDIOL approach can be recommended as a suitable tool when PFs derived from specific processing studies are missing. Similar studies on pesticides with wider ranges of log P_ow are required in order to complete our conclusions on default PFs for vegetable oils.     

Effects of processing on pesticide residues in peaches intended for baby food

Peaches containing added residues of chlorpyrifos-methyl, fenitrothion, procymidone and vinclozolin were used for simulated industrial processing in the manufacture of baby food puree. Residues were determined in raw material, in intermediate products at crucial steps of the processing procedure and in final products. Determination of residues was performed by an analytical method, distinguished by high sensitivity, based on acetone extraction, a two-step clean-up/pre-concentration on graphitized carbon and SAX/PSA sorbent, and GC-ECD. The results of the study were interpreted with respect to enforcement of the stringent Maximum Residue Limit (MRL) of 0.01 mg kg^-1 established by the European Commission (EC) for any pesticide in baby food. Peeling was identified as the most effective procedure in reducing residues. Thermal treatment (concentration and sterilisation) substantially reduced organophosphate (chlorpyrifos-methyl, fenitrothion) residues, whereas procymidone and vinclozolin residue levels were increased in peach puree.     

番茄、辣椒、茄子中甲基毒死蜱残留量测定

采用高效液相色谱-二极管阵列检测器对番茄、辣椒和茄子中甲基毒死蜱残留量进行测定。样品用乙腈提取后,经Carb/NH2固相萃取小柱净化,用C8液相色谱柱、二极管阵列检测器,对甲基毒死蜱残留量的测定可取得满意的结果。该方法样品平均加标回收率为80.7%～92.4%,相对标准偏差为1.1%～4.6%;蔬菜中甲基毒死蜱检出下限为0.02mg/kg。     

甲基毒死蜱的开发研究

目前甲胺磷等高毒农药正处于停止生产,停止使用阶段。本文从投资到应用,从产品特性到生产工艺进行论述从而说明甲基毒死蜱是替代这些高毒农药的好品种。     

气相色谱法测定大豆中甲基毒死蜱残留量

目的 建立气相色谱法测定大豆中甲基毒死蜱的残留量的分析方法。方法 使用乙腈萃取样品, 经中性氧化铝柱去除杂质, VF-5毛细管柱分离, 气相色谱仪定量分析甲基毒死蜱在大豆中的残留量。同时, 与SN/T 2324-2009中的方法进行对比, 考察了本方法的线性、回收率、精密度、重现性。结果 本方法中甲基毒死蜱在0.15~25.0 μg/mL范围内的线性关系良好, 曲线方程为: Y=6.6185X?0.0090, r2=0.99910, 甲基毒死蜱的检出限为0.01 mg/kg, 定量限为0.03 mg/kg, 加标回收率为89.7%~97.0%, 相对标准偏差为1.92%~5.11%。结论 与国标方法对比, 本方法灵敏度高, 定量准确, 具有简单实用、效率高、成本低等优点, 适合大豆中甲基毒死蜱残留量的检测。