气相色谱法测定40%毒死蜱乳油中有效成分含量的不确定度评估

分析了实验室使用气相色谱法测定40%毒死蜱乳油有效成分含量试验中各种不确定度分量的来源,并加以评定。通过分析发现对于<2mL的移液管可不考虑温度影响,本文最终结果可在同样测试条件下直接使用。     

有机氯农药混合标准溶液配制不确定度评定

标准溶液的配制和稀释所引入的各种因素都可能影响其真实浓度,从而影响检测结果的准确性。评定其中的各种分量不确定度,为提高实验室的质量控制水平、降低分析成本和检测结果的正确性提供保证。本文以实际应用的24种有机氯农药混合标准溶液为例,采用了配制混合标准溶液过程单元操作的不确定度计算方法 (top down法),分析了在配制混合标准溶液过程中的所有影响因素,评定了所引入各种分量的不确度,合成扩展不确定度,得到了最终的扩展不确定度。最终结果显示,稀释过程中由2mL移液管所引入的不确定度贡献最大,表明选择好的移液器具和尽量精准的估读移液器具的刻度是影响标准溶液稀释最重要的因素。     

植物检疫定性判定结果不确定度浅析

本文通过定量结果不确定度，探讨植物检疫定性判定结果不确定度及其存在的风险，从分析定性判定结果不确定度来源入手，提出了影响定性判定结果的抽样、人员、方法、仪器设备、环境和重复测量6个方面因子，并通过实例给出如何评估定性判定结果不确定度以及不确定度的表达方式。     

黄瓜中乙烯菌核利残留测定的测量不确定度评定

依据NY/T761—2008标准第二部分,采用气相色谱法对黄瓜中乙烯菌核利残留进行测定,分析检测过程中的各不确定度分量来源,建立了不确定度评定的数学模型,进而对各不确定分量进行合成与扩展。结果表明:黄瓜中乙烯菌核利残留测量结果的合成相对标准不确定度和扩展不确定度分别为2.78%和5.56%（k=2）,其中标准溶液的稀释与定容过程、乙烯菌核利残留的提取和净化过程所产生的回收率差异、色谱峰面积测量导致的误差是测量不确定度的主要来源。本研究结果可为客观评价蔬菜中农药残留检测结果提供参考。     

高效液相色谱法测定苹果中多菌灵残留量的测量不确定度分析

建立了评定NY/T 1680－2009“蔬菜水果中多菌灵等4种苯并咪唑类农药残留量的测定——高效液相色谱法”中影响测量不确定度的各因素的数学模型,考察了样品前处理和液相色谱测定的各个环节,并根据所建立的数学模型计算了评定测量不确定度的各分量。采用该方法测得市售苹果中多菌灵的残留量为0.23 mg/kg。分析表明:多菌灵残留量测定的不确定度主要来源于样品溶液的平行测定、样品稀释以及萃取、净化等处理过程产生的回收率差异;此外,标准溶液的配制和检测过程以及提取处理等其他环节对其也有一定影响。经计算,在置信概率P=95%时,采用该方法测定试样中多菌灵残留的扩展不确定度为0.02 mg/kg,若不考虑多菌灵残留在样品中分布的均匀性,则苹果试样中多菌灵残留的检测结果可表示为(0.23±0.02) mg/kg（包含因子k=2）。     

百草枯水剂中百草枯含量测量不确定度评估

测定农药百草枯水剂中百草枯的含量,分析评定测量过程的不确定度来源,计算合成不确定度,并给出百草枯测量不确定度表达式.     

0.02%二氢卟吩铁可溶粉剂HPLC测定方法不确定度评估

本文分析了采用高效液相色谱法测定二氢卟吩铁含量时不确定度分量的来源并加以评定,计算合成不确定度及扩展不确定度,得出了二氢卟吩铁测量不确定度表达式,适用于针对原药或制剂中二氢卟吩铁含量检测过程中产生的不确定度进行评估。     

蔬菜中毒死蜱等几种农药残留量测定不确定度分析

本文结合NY/T 761-2004农药残留分析方法,把毒死蜱、氯氰菊酯、茚虫威、烯酰吗啉等4种农药残留量测定不确定度分为称量、提取、净化、色谱测定等分量,用校正因子来表征测定过程中的重复性不确定度,并加以评定,为试验室质量管理和控制提供科学依据。结果表明,色谱定量重复性误差及同一样品的重复性误差所引入的不确定度是影响残留量测定不确定度的较大因素。     

加速溶剂萃取-气相色谱法测定茶叶中八氯二丙醚残留量及其不确定度评估

建立了加速溶剂萃取-气相色谱(ASE-GC)法测定茶叶中八氯二丙醚残留量的方法。茶叶样品经加速溶剂萃取仪用正己烷-丙酮(1∶1,体积比)提取,经硅藻土-浓硫酸(10 g∶4.0 mL )净化,以正己烷洗脱并定容,GC-ECD检测,外标法定量。此外,对测定过程中可能引入的不确定度进行了分析和评定。结果表明:在质量浓度为0.010~0.40 mg/L范围内,峰面积与八氯二丙醚的质量浓度成良好的线性关系,相关系数r=0.999 1;八氯二丙醚的添加水平在5~30 ng/g范围内,平均回收率为90.2%,相对标准偏差(RSD)为4.7%,方法的检出限(LOD)为0.005 mg/kg;当茶叶中八氯二丙醚含量为0.053 1 mg/kg时,取置信概率为95%,包含因子k=2,则其扩展不确定度U=0.003 6 mg/kg。通过对不确定度的分析,发现影响测定结果不确定度的主要来源有回收率、测量重复性和标准溶液的配制过程。     

三种基质中15种农药及其代谢物的不确定度评估

依据GB 23200.113—2018《食品安全国家标准植物源性食品中208种农药及其代谢物残留量的测定气相色谱-质谱联用法》中的QuEChERS方法,建立了一种气相色谱-串联质谱法(GC-MS/MS)测定茶叶、普通白菜和苹果3种基质中15种农药及其代谢物残留量的数学模型,通过分析测定过程的主要不确定度来源,对各个分量进行评估。结果表明：工作曲线拟合和回收率所引入的不确定度较大,其次为标准溶液配制和样品制备,而测量重复性和仪器引入的不确定度相对较小;不同基质对工作曲线拟合、回收率和测量重复性所引入的不确定度存在一定差异;不匹配基质校正曲线会对部分农药造成一定程度的基质增强或抑制效应。该方法适用于GC-MS/MS法测定植物源性食品中农药残留量的不确定度评估,可为农药残留测量结果的准确性提供科学可靠的依据。     

A model of the decision‐support scheme for express pest risk analysis using a Bayesian network implemented in Excel

A model was developed to accompany the EPPO decision support scheme for express pest risk analysis (PRA) and provide a calculated overall risk and uncertainty for the PRA and so act as a reference for the judgement of overall risk and uncertainty provided by expert working groups. Implemented in Excel, it is readily accessible to PRA practitioners and offers: (a) a consistent and explained weighting of the different risk factors and a rationale for the way they are combined, (b) a calculated integration of the risk factor distributions to facilitate judgement of overall uncertainty, and (c) an account of the interaction between the rating and the uncertainty score so that, for example, an overall rating of moderate is not necessarily used to reflect uncertainty about assessments in which the risk is neither obviously high nor low. Of the nine published express PRAs examined, the rating and uncertainty predicted by the model were: in agreement with five; differed in both rating and uncertainty in one case; differed in rating only in one case; and differed in uncertainty only in two cases. Possible reasons for these differences were examined and the interpretation of model results to inform assessments is discussed.     

室温及低温制备生菜样本过程的不确定度和25种农药残留的稳定性

以毒死蜱为内标,对农药残留分析中生菜样本的两种制备方法——室温处理和低温加干冰处理结果的不确定度进行了比较研究;进一步采用统计学t-检验,对25种农药在两种制备方法中的稳定性进行了评价。采用QuEChERS(quick,easy,cheap,effective,rugged,safe)方法对处理后样本进行提取、净化,以乙腈为提取剂,N-丙基乙二胺键合固相吸附材料PSA(primary secondary amine)为分散净化剂,采用GC-MS方法分析。结果显示,两种制备方法结果的不确定度接近(室温5.2%,低温5.4%);低温处理过程会提高某些农药的稳定性,降低分解率,如甲萘威和残杀威在低温处理时稳定性明显提高,而敌敌畏和百菌清则在两种处理条件下都会分解。表明农药的稳定性既与农药本身的理化性质有关,也受处理过程中的操作条件等影响。     

Effect of pesticide fate parameters and their uncertainty on the selection of 'worst-case' scenarios of pesticide leaching to groundwater

BACKGROUND: For the registration of pesticides in the European Union, model simulations for worst‐case scenarios are used to demonstrate that leaching concentrations to groundwater do not exceed a critical threshold. A worst‐case scenario is a combination of soil and climate properties for which predicted leaching concentrations are higher than a certain percentile of the spatial concentration distribution within a region. The derivation of scenarios is complicated by uncertainty about soil and pesticide fate parameters. As the ranking of climate and soil property combinations according to predicted leaching concentrations is different for different pesticides, the worst‐case scenario for one pesticide may misrepresent the worst case for another pesticide, which leads to ‘scenario uncertainty’. RESULTS: Pesticide fate parameter uncertainty led to higher concentrations in the higher percentiles of spatial concentration distributions, especially for distributions in smaller and more homogeneous regions. The effect of pesticide fate parameter uncertainty on the spatial concentration distribution was small when compared with the uncertainty of local concentration predictions and with the scenario uncertainty. CONCLUSION: Uncertainty in pesticide fate parameters and scenario uncertainty can be accounted for using higher percentiles of spatial concentration distributions and considering a range of pesticides for the scenario selection. Copyright © 2010 Society of Chemical Industry     

Accounting for uncertainty in pedotransfer functions in vulnerability assessments of pesticide leaching to groundwater

A simulation tool for site-specific vulnerability assessments of pesticide leaching to groundwater was developed, based on the pesticide fate and transport model MACRO, parameterized using pedotransfer functions and reasonable worst-case parameter values. The effects of uncertainty in the pedotransfer functions on simulation results were examined for 48 combinations of soils, pesticides and application timings, by sampling pedotransfer function regression errors and propagating them through the simulation model in a Monte Carlo analysis. An uncertainty factor, f(u), was derived, defined as the ratio between the concentration simulated with no errors, c(sim), and the 80th percentile concentration for the scenario. The pedotransfer function errors caused a large variation in simulation results, with f(u) ranging from 1.14 to 1440, with a median of 2.8. A non-linear relationship was found between f(u) and c(sim), which can be used to account for parameter uncertainty by correcting the simulated concentration, c(sim), to an estimated 80th percentile value. For fine-textured soils, the predictions were most sensitive to errors in the pedotransfer functions for two parameters regulating macropore flow (the saturated matrix hydraulic conductivity, K(b), and the effective diffusion pathlength, d) and two water retention function parameters (van Genuchten's N and alpha parameters). For coarse-textured soils, the model was also sensitive to errors in the exponent in the degradation water response function and the dispersivity, in addition to K(b), but showed little sensitivity to d. To reduce uncertainty in model predictions, improved pedotransfer functions for K(b), d, N and alpha would therefore be most useful.     

实验室农药残留检测的测量不确定度评定——以GB 23200.8—2016测定草莓中4种农药残留为例

自2018年《CNAS-GL006化学分析中不确定度的评估指南》颁布后,不确定度计算方法的需求日益增强。本研究依据GB 23200.8-2016《水果和蔬菜中500种农药及相关化学品残留量的测定气相色谱-质谱法》,采用气相色谱-质谱法,结合内标定量法,对草莓中丙溴磷、亚胺硫磷、五氯硝基苯和氯氟氰菊酯的残留进行了测量不确定度的详细评定,共涉及标准品纯度、储备液配制、工作液配制、称样量和前处理过程5个B类评定分量,以及标准溶液峰面积、样品溶液峰面积和添加回收率3个A类评定分量。结果显示:在0.08 mg/kg添加水平下,丙溴磷、亚胺硫磷、五氯硝基苯和氯氟氰菊酯的测量合成相对标准不确定度依次为3.55%、3.22%、2.20%和3.66%,样品溶液峰面积和添加回收率2个A类不确定度分量对4种农药合成不确定度的贡献较高,其中丙溴磷、亚胺硫磷和氯氟氰菊酯均超过60%,五氯硝基苯超过31%。本研究中4种农药在草莓样品中的测量结果在95%的置信限(k=2)内可表示为:丙溴磷,0.085±0.006 mg/kg;亚胺硫磷,0.084±0.005 mg/kg;五氯硝基苯,0.079±0.003 mg/kg;氯氟氰菊酯,0.082±0.006 mg/kg。不确定度评定结果将最大限度地减少待测物在最大残留限量附近的残留值判定可能存在的争议。     

Descriptive assessment of uncertainties of qualitative real‐time PCR for detection of plant pathogens and quality performance monitoring

In most cases, plant pest diagnostic methods are interpreted as providing qualitative data. However, although qualitative, it is still important to identify all the sources and components of uncertainty in the diagnostic process and to ensure that appropriate measures are taken to reduce the uncertainty and that the form of reporting the result does not give the wrong impression of the uncertainty. This process was illustrated using real‐time PCR testing of grapevine yellows phytoplasma. Some additional quality performance monitoring of real‐time PCR is also described. This approach has been used by the National Institute of Biology, Slovenia, since 2012, in support of accreditation under ISO 17025, and it can also be applied to other detection methods and other pests.