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1.
来自《测量不确定度表述导则》(GUM95)中的模型,是国际上第一个取得一致认同的模型,也一直被作为我国环境监测实验室不确定度评定的经典方法。但是GUM方法采用的是bottom-up技术来进行不确定度评定,其步骤繁琐,容易造成遗漏或重复,且无法反映实验室长期质控状态。本文采用Top-down不确定度的评定方法一控制图法来评定本实验室质控样铅砷的不确定度,数据主要来自实验室内质控,通过AD统计法和绘制移动极差控制图,判断数据是否具有正态性和独立性,计算获得砷铅的不确定度。Top-down方法将测量不确定度评定与实验室质控工作紧密相连,对于环境监测领域不确定度的评定,它比GUM法更实用。  相似文献   

2.
利用环境监测实验室积累的数据,通过线性拟合法、GUM法和控制图法对水中化学需氧量的不确定度进行了评定。结果表明:3种不确定度评定方法的评定结果相似。在量化过程中存在两种主要不确定度评定的类型:一种是不确定度的正向传播,另一种是模型不确定度和参数不确定度的反向评定。GUM法明显是正向的不确定度,线性拟合法和控制图法是反向不确定度。GUM法应用复杂且烦琐,操作性差;相比,控制图法和线性拟合法更加简单实用,可代替GUM法来评估监测实验室的不确定度。  相似文献   

3.
火焰原子吸收法测定水样铅含量的不确定度评定   总被引:1,自引:0,他引:1  
实验室认可和资质认定都要求检测实验室具备评定测量不确定度的能力,现依据JJF1059-1999《测量不确定度评定与表示》,对火焰原子吸收法测定水样中铅含量进行不确定度评估,分析测定过程中不确定度来源,量化不确定度分量,求出合成不确定度和扩展不确定度,给出测定结果的表示式。  相似文献   

4.
测量不确定度及其估算   总被引:5,自引:0,他引:5       下载免费PDF全文
《检测和校准实验室能力的通用要求》GB/T1 5 4 81 - 2 0 0 0发布以来 ,在实验室认可和计量认证的复核中 ,测量不确定度的评定已成为各实验室准备工作的重点。《检测和校准实验室能力的通用要求》规定 :检测和校准实验室都必须具有对测量结果进行不确定度评定的程序 ,并且还应该在具体的检测和校准工作中应用这些程序来进行测量不确定度的评定。测量不确定度在检测工作中的正确使用 ,可以衡量实验室科学管理 (质量体系的有效运行 )和检测技能 (分析质量控制和出具有效检测结果的能力 )的水平 ,也是计量认证复核和实验室认可评审的要素之…  相似文献   

5.
《测量不确定度表示指南》[简称(GUM)]采用当前国际通行的观点和方法,使涉及测量的技术领域和部门可以用统一的准则对测量结果及其质量进行评定、比较和表示.在环境监测中使用GUM不仅是不同学科之间交往的需要,也是全球市场经济发展的需要.讨论了室内空气中总挥发性有机物的测量不确定度的产生原因及其评定方法.在不确定度的所有可能来源中找出主要来源,分析其不确定度分量是一种可行的评定方法.  相似文献   

6.
阐述了厂界噪声测量的不确定度来源和对不确定度分量的评定,并且对不确定度分量评定中有关的内容进行了实例计算,为测量的不确定度在环境监测领域中的评定提供了参考.  相似文献   

7.
王梅 《环境研究与监测》2005,18(1):42-44,49
阐述了环境监测分析中不确定度的基本概念和测定不确定度的评估过程,介绍了A类不确定度估算中的贝塞尔法、组合实验标准法、极差法、最小二乘法以及B类不确定度的一般信息来源及估算,并结合环境监测分析的具体情况,举例分析操作过程中不确定度各分量的估算,建立了测量结果的溯源性,对实验室提供数据的质量保证具有十分重要的意义.  相似文献   

8.
依据现有指南和规范,在分析方法标准验证实验和报告中,常常分别评估准确度和精密度。这容易导致以加标回收率表示的准确度数据缺乏良好精密度支持的现象。基于ISO 11352原理,首次提出在不增加实验室分析人员工作量的情况下,利用自上而下技术评估方法测量不确定度,即同时考虑准确度与精密度作为一个综合性指标评估方法性能。这是标准制修订时落实测量不确定度条文一条操作性强的技术路线。利用改进后的加标回收率计算结果评估方法准确度。5组方法验证实测数据表明,用测量不确定度这一综合性指标评估方法性能比分别用准确度和精密度指标更符合实际情况。他可引导实验室分析人员在设计和处理方法验证数据时,更加重视方法精密度。在修订HJ 168—2010时,建议增加测量不确定度这一综合性指标评估方法性能。  相似文献   

9.
对微波消解-电感耦合等离子发射光谱法测定土壤样品中Cu、Pb、Zn、Cr、Ni的不确定度进行评估,在测定过程中,对样品称量、消解、定容体积、标准溶液的配制、曲线拟合、仪器测量重复性等影响不确定度的分量进行分析,按《测量不确定度评定与表示》(JJF 1059—1999)的规定进行合成,最终给出扩展不确定度,为电感耦合等离子发射光谱法测量土壤中重金属元素的实验室质量控制和不确定度评定提供参考依据。  相似文献   

10.
采用Top—Down不确定度评定理念,利用实验室日常质控数据,结合标准样品的线性校准方法(线性拟合法),评定水中总磷的测量不确定度,并将评定结果与GUM评定法相比较,相对偏差≤20%。指出线性拟合法适用于测量系统校准函数成线性,且实验总残差符合常数剩余标准差假定情况下的不确定度评定。  相似文献   

11.
环境监测实验室认可中应关注的若干问题   总被引:6,自引:2,他引:4       下载免费PDF全文
对《检测和校准实验室能力认可准则》(简称《准则》)实施中关于有效性评价实施不到位、关注实验室法律文本的法律性、把握不符合项的实施准确性、实验室CNAS能力验证、测量不确定度政策落实不到位等问题进行了探讨。指出,应从环境监测实验室管理实际出发,深刻理解《准则》的管理要求和作用,以《准则》规范实验室行为,不断改进和完善实验室管理体系建设,确保管理体系持续有效运行。  相似文献   

12.
Assessment of trace element contents in soils is required in Germany (and other countries) before sewage sludge application on arable soils. The reliability of measured element contents is affected by measurement uncertainty, which consists of components due to (1) sampling, (2) laboratory repeatability (intra-lab) and (3) reproducibility (between-lab). A complete characterization of average trace element contents in field soils should encompass the uncertainty of all these components. The objectives of this study were to elucidate the magnitude and relative proportions of uncertainty components for the metals As, B, Cd, Co, Cr, Mo, Ni, Pb, Tl and Zn in three arable fields of different field-scale heterogeneity, based on a collaborative trial (CT) (standardized procedure) and two sampling proficiency tests (PT) (individual sampling procedure). To obtain reference values and estimates of field-scale heterogeneity, a detailed reference sampling was conducted. Components of uncertainty (sampling person, sampling repetition, laboratory) were estimated by variance component analysis, whereas reproducibility uncertainty was estimated using results from numerous laboratory proficiency tests. Sampling uncertainty in general increased with field-scale heterogeneity; however, total uncertainty was mostly dominated by (total) laboratory uncertainty. Reproducibility analytical uncertainty was on average by a factor of about 3 higher than repeatability uncertainty. Therefore, analysis within one single laboratory and, for heterogeneous fields, a reduction of sampling uncertainty (for instance by larger numbers of sample increments and/or a denser coverage of the field area) would be most effective to reduce total uncertainty. On the other hand, when only intra-laboratory analytical uncertainty was considered, total sampling uncertainty on average prevailed over analytical uncertainty by a factor of 2. Both sampling and laboratory repeatability uncertainty were highly variable depending not only on the analyte but also on the field and the sampling trial. Comparison of PT with CT sampling suggests that standardization of sampling protocols reduces sampling uncertainty, especially for fields of low heterogeneity.  相似文献   

13.
The Workplace Analysis Scheme for Proficiency (WASP) is a proficiency testing scheme for the analysis of occupational hygiene and environmental air samples and is operated in the UK by the Health and Safety Laboratory. Since 1997, WASP has offered samples of benzene, toluene and m-xylene, at environmental levels on Tenax, and has about 35 laboratories participating, mostly from industry, local government and consultancy organisations in the UK. The results reported cover the first 10 rounds of the environmental analytes (1997-1999) and demonstrate the important role of proficiency testing in assessing the quality of laboratory performance. Estimates are obtained for within-laboratory precision and the total variability at each analyte level. The estimates of within-laboratory precision suggest that laboratories have more difficulty analysing toluene and m-xylene than benzene. Linear relationships for the reproducibility relative standard deviation (RSDT) with loading level are evident for the analytes at occupational levels. At environmental levels, the relationship between loading level and reproducibility is much less well defined. The standard deviation for the proficiency testing assessment for all three analytes at the environmental level is 14%, as derived from the benzene data. Expanded uncertainty estimates (k = 1.96), for the analysis of samples since the scheme started, are obtained from the average total variance, and are 27% for benzene, 39% for toluene and 36% for m-xylene. Although the linear trend of performance against round number was not significant at the 95% level of confidence (p = 0.23 for benzene, p = 0.3 for toluene and p = 0.32 for m-xylene), there was a general improvement in RSDT from 26-34% to about 8-13% 10 rounds later. Currently, for a laboratory to meet one of the data quality objectives in the Ambient Air Directive (indicative measurement of benzene, expanded uncertainty +/- 30% or less), it would have to achieve a level of analytical performance to satisfy the category 1 (best performance) limit of better than +/- 8.8%. In the last proficiency testing round, discussed in this paper, only 58% of laboratories obtained performance scores that indicated that they were able to consistently achieve this level of performance.  相似文献   

14.
Measurement sensitivity and bias quality control metrics are commonly reported for water-quality parameters measured in the laboratory. Less commonly recognized is that they should also be reported for field-measured parameters. Periodic evaluation helps document data quality and can help serve as early warning if there are problems with methods or techniques that could negatively affect ability to interpret threshold values and trends over time. This study focuses on traditional assessment of bias and introduces a new method for estimating measurement sensitivity of water-quality parameters measured monthly in the field. Alternative measurement sensitivity is a new data quality indicator used to demonstrate how quantifying sensitivity at the measurement level can improve understanding the uncertainty affecting each reported data value. That, in turn, can help interpret the meaning of results from many separate data points measured in the field. In this 30-month study, pH and specific conductance consistently met, and dissolved oxygen did not always meet NPS and USGS quality control standards for bias. Evaluation of dissolved oxygen bias and sensitivity during the study provided impetus to improve calibration techniques that resulted in data that later met quality goals.  相似文献   

15.
确保测量结果的计量溯源性是保障数据有效性的基本要求。为此,国家明确提出要建立健全国家生态环境监测量值溯源体系。化学测量是环境监测工作中最常用的一种测量方式。由于基体、浓度等的影响往往比较复杂,如何确保环境监测化学测量结果的计量溯源性成为环境监测领域的重要研究内容。通过总结建立环境监测化学测量结果计量溯源性的途径,对环境监测分析方法标准、国家环境标准样品、环境检测能力验证等在保证环境监测化学测量结果计量溯源性中的作用进行了分析,以期为环境监测化学测量结果计量溯源性的建立提供参考。  相似文献   

16.
实验室能力验证中的分割水平检测样品与稳健统计技术   总被引:5,自引:3,他引:2  
论述了分割水平检测样品和稳健统计技术在对实验室能力验证活动中的应用,并对导致CNAL T040水中金属元素检测能力验证计划中部分结果异常的原因进行了分析。  相似文献   

17.
To determine the heavy metal content in soil samples at contaminated locations, a static and time consuming procedure is used in most cases. Soil samples are collected and analyzed in the laboratory at high quality and high analytical costs. The demand by government and consultants for a more dynamic approach and by customers requiring performances in which analyses are performed in the field with immediate feedback of the analytical results, is growing. Especially during the follow-up of remediation projects or during the determination of the sampling strategy, field analyses are advisable. For this purpose four types of ED-XRF systems, ranging from portable up to high performance laboratory systems, have been evaluated. The evaluation criteria are based on the performance characteristics for all the ED-XRF systems such as limit of detection, accuracy and the measurement uncertainty on one hand, and also the influence of the sample pretreatment on the obtained results on the other hand. The study proved that the field portable system and the bench top system, placed in a mobile van, can be applied as field techniques, resulting in semi-quantitative analytical results. A limited homogenization of the analyzed sample significantly increases the representativeness of the soil sample. The ED-XRF systems can be differentiated by their limits of detection which are a factor of 10 to 20 higher for the portable system. The accuracy of the results and the measurement uncertainty also improved using the bench top system. Therefore, the selection criteria for applicability of both field systems are based on the required detection level and also the required accuracy of the results.  相似文献   

18.
为有效避免南宁市城市内河水质出现仅透明度超标导致黑臭等级误判的情况,通过相关性分析、方差分析和多重对应分析确定评价指标和临界值,建立基于综合水质指数法的城市内河黑臭分级评价方法。结果表明:以溶解氧、氨氮、总磷和化学需氧量为黑臭分级评价指标,水体轻度黑臭和重度黑臭综合水质指数临界值分别为6.3和8.5。该评价方法结果符合实际情况,且能反映水质的时空变化情况。  相似文献   

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