茶叶中甲氰菊酯测定能力验证中结果评价方式的选择

实施茶叶中甲氰菊酯测定能力验证计划,对不同的结果评价方式进行对比。制备含甲氰菊酯的茶叶样品,经均匀性和稳定性考察合格后用于能力验证。以专家实验室结果平均值作为指定值,由再现性标准差和重复性标准差求计算出能力评定标准差,评价参加者能力。用稳健算法、经验模型法确定统计评价量,与本法测定结果进行比对。结果显示,5家专家实验室提供了呈现正态分布且等精度的结果,评价结果的满意率为88.7%。与其它评定方式相比,本法给出的满意结果区间较为严格,能够反映检验机构应达到的检测水平。     

基于迭代算法A的海水盐度能力验证结果分析

为评价海洋检验检测机构海水盐度检测能力,国家海洋标准计量中心设计并实施了2020年度海水盐度能力验证计划,制备能力验证样品并开展均匀性检验。本次能力验证采用双样品以随机组合形式发放,利用迭代算法A对62家实验室提交的能力验证数据进行统计分析处理,合理确定指定值及其不确定度,将能力验证数据转化为能力统计量,根据Z比分数评定各参加实验室能力验证结果。结果显示,双样品全部“满意”的实验室有52家,占85.5%,有3家实验室能力验证结果“不满意”,6家实验室能力验证结果“有问题”。“不满意”和“有问题”的实验室共占14.5%。本次能力验证数据的频率分布接近正态分布,通过开展双样品联合置信概率分析和仪器类型统计分析,与往年能力验证结果“满意率”进行比较,绝大多数实验室海水盐度检测能力良好,个别实验室仍需加强海水盐度检测能力建设和内部质量控制。     

食品接触材料中高锰酸钾消耗量检测能力验证实施及应用评价

面对日趋完善的食品接触材料卫生标准体系,为掌握高锰酸钾消耗量测定的技术要求,做好相应合规性判定,充分发挥能力验证对检验检测机构技术能力监督和质量提升的作用,该文进行了食品接触用塑料材料及制品中高锰酸钾消耗量的测定能力验证。通过定制棕色塑料食品包装瓶作为相关能力验证样品,依据相关标准要求进行均匀性、稳定性评价,对回收结果采用稳健统计技术算法A确定指定值和能力评定标准差,并对可能产生不满意结果的影响因素进行了分析。192家参与该项能力验证的实验室中有179家结果为满意,满意率为93.2%;12家实验室结果为不满意,占6.3%;1家实验室结果为可疑,占0.5%。总体结果较好,个别实验室出现的不合格结果可通过本次能力验证分析查找原因,达到提高实验室相应检测能力的目的。     

水产品中磺胺类药物残留量实验室间检测能力的验证结果与分析北大核心CSCD

为全面、客观、科学地了解和评价上海市有关实验室对水产品中磺胺类药物(SAs)残留量的检测能力,计划并实施了水产品中SAs残留量检测能力的验证。参加本项目的实验室达17家,通过养殖给药方式制备了阳性鱼肉样品。采用单因子方差分析法和平均值一致性检验法对样品进行均匀性和稳定性检验。对各参加实验室上报结果进行稳健统计分析,采用Z比分数评定各参加实验室的结果。17家资质实验室中获得满意结果的有15家,水产品中磺胺类药物残留检测能力总体较好。对数据结果分析表明:样品前处理和标准物质的选用是最容易引入误差的环节。     

利用能力验证结果评价参加实验室的整体检测能力

能力验证是利用实验室间比对确定实验室检测能力的活动,其评价结果多用于评估单个实验室的检测能力。行业监管部门期望掌握实验室整体能力和检测方法的相关信息,为分析参加实验室的整体检测能力和不同测试方法的差异,分析了3年航空煤油检测能力验证结果,采用满意结果百分比、|Z|值平均值随参加能力验证次数的变动情况,证实了能力验证对整体检测能力的改进作用;利用异方差t检验,比较不同测试方法结果的一致性和精密度差异;通过比较能力验证评价标准差和检测标准的精密度要求,评价参加实验室整体检测能力是否符合检测标准要求。研究表明,能力验证数据能够用于定量分析参加实验室的整体检测能力,为行业实验室监管和检测方法间比对提供依据。     

纺织品中4-氨基偶氮苯的测定能力验证分析

“P00012-2011-T07纺织品中禁用偶氮染料的测定(测试项目:4-氨基偶氮苯)”能力验证严格按照能力验证计划运作要求实施,并采用稳健统计法对测试结果进行统计,测试样品指定值为54.8 mg/kg,标准化四分位距(NIQR)为6.8941 mg/kg.共有12个省市、自治区的61家实验室参加本次能力验证,采用Z比分数对各实验室结果进行评价,结果满意率为86.9％.     

橡胶拉伸强度能力验证计划和统计分析

采用稳健统计技术对全国84家实验室橡胶拉伸强度能力验证结果进行统计分析,结果显示全部满意的实验室78家,结果可疑的实验室有6家,并对实验室结果出现可疑的原因进行了分析。     

食品毒理学测试能力验证的研究

介绍了CNALT0158“食品添加剂毒性测试能力验证计划”,其中包括测试项目的选定、测试样品的制备及测试样品均匀性、稳定性检测方法,并对参试实验室测试结果进行了统计评价。影响半数致死量(LD50)的因素有很多,对于CNALT0158计划中LD50测试结果可能产生显著影响的因素是:实验动物的健康状况、试验环境温度的控制、受试动物的分组等。     

《分析测试统计方法和质量控制》书讯

<正>曹宏燕等编著。《分析测试统计方法和质量控制》全书分十三章,七十三万余字,介绍了分析测试及其试验研究中常用的数理统计方法,包括误差和误差的分布、统计检验、方差分析、正交设计、回归分析等统计方法的理论与实践。本书紧密结合国际标准(ISO)、国家标准(GB)及中国合格评定国家认可委员会(CNAS)等有关实验室管理规范、标准和认可要求,阐述了实验室协同试验和管理中测量结果精密度试验和应用、能力验证及其稳健统计、测量不确定度评定、标准物质研制及应用、分析方法的评价及分析结果的表     

《分析测试统计方法和质量控制》书讯

<正>曹宏燕等编著。《分析测试统计方法和质量控制》全书分十三章,七十三万余字,介绍了分析测试及其试验研究中常用的数理统计方法,包括误差和误差的分布、统计检验、方差分析、正交设计、回归分析等统计方法的理论与实践。本书紧密结合国际标准(ISO)、国家标准(GB)及中国合格评定国家认可委员会(CNAS)等有关实验室管理规范、标准和认可要求,阐述了实验室协同试验和管理中测量结果精密度试验和应用、能力验证及其稳健统计、测量不确定度评定、标准物质研制     

The certification of a new paint reference material

The use of paint as a coating for toys intended for sale on the European market is controlled by a European Standard (EN 71-3: 1994-European Standard for the Safety of Toys, Part 3—Migration of Elements). This work is the result of a preliminary study organised by the European Commission to produce a new paint reference material which can be used to validate the test methods given in the European Standard. The migration of elements from painted panels and comminuted paint produced by the Laboratory of the Government Chemist, (U.K.) was studied. Several methods were used in this certification exercise and this work reports the recults of neutron activation analysis and inductively coupled plasma mass spectrometry to determine the migration of As, Ba, Cd, Cr, Hg, Pb, Se and Sb into a simulated stomach environment. Replicate extracts obtained from paint samples gave a precision of within 10% for most elements by both analytical techniques for the paint panels and for the comminuted paint sample. This preliminary study has shown that the standard method can provide reproducible results for each of the paint materials studied and indicates that the study should be continued to produce a fully certified paint reference material.     

CNAL/T0086水溶液pH值测定能力验证分析

2003年5～8月期间,中国实验室国家认可委员会组织了CNAL／T0086水溶液的pH值测定能力验证。本次能力验证由中国实验室国家认可委员会组织,国家标;住物质研究中心负责协调及实施。能力验证的目的是评价各实验室水溶液pH值测定的测试能力和测试水平。对测试结果的统计采用方便并为国际和区域承认的方法——稳健统计法,根据Z比分数评判各实验室的测试结果。     

Practical uses of proficiency testing as valuable tools for validation and performance assessment in environmental analysis

Besides their role as an external quality control tool, PT results or samples could be used as an alternative to fulfil some of the quality assurance requirements such as analytical precision, uncertainty assessment, and internal quality control. This additional use of proficiency testing could help laboratories to reduce the financial impact of their quality assurance process. The purpose of this paper is to highlight some practical uses of PT results or samples in the environmental analytical field, which have been implemented at ISSeP (Institut Scientifique de Service Public), either for method validation or for internal quality control.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia     

Comparability of analytical results obtained in proficiency testing based on a metrological approach

A “yes–no” type of criterion is proposed for the assessment of comparability of proficiency testing (PT) results when the PT scheme is based on a metrological approach, i.e. on the use of a reference material as the test sample, etc. The criterion tests a null hypothesis concerning the insignificance of a bias of the mean of the results from a traceable value certified in the reference material used for the PT. Reliability of such assessment is determined by the probabilities of not rejecting the null hypothesis when it is true, and rejecting it when it is false (the alternative hypothesis is true). It is shown that a number of chemical, metrological and statistical reasons should be taken into account for careful formulation of the hypotheses, enabling the avoidance of an erroneous assessment of the comparability. The criterion can be helpful for PT providers and laboratory accreditation bodies in analysis of PT results.     

The role of proficiency testing in method validation

The general principle of using data collected during proficiency testing (PT) for the additional purpose of assessing method performance is discussed. Particular attention is paid to the similarities and differences in conduct of traditional interlaboratory method performance studies and proficiency testing. Recommendations are made for implementing PT-based method performance studies, including statistical assessment of the data. It is concluded that, properly implemented, PT-based method performance study provides essentially equivalent information to that obtained from traditional collaborative study and may be used in appraising candidate methods with a view to their adoption as standard methods.     

Evaluation of the long-term performance of water-analyzing laboratories

After 7 years of successful operation, the database of the proficiency testing (PT) scheme for water analysis organized by the Institute for Agrobiotechnology (IFA), Tulln contains nearly 4,000 data sets from over 300 interlaboratory comparison samples. About 70 analytical parameters (major ions, metals, trace ions, herbicides, volatile halogenated hydrocarbons, organochlorine pesticides and polycyclic aromatic hydrocarbons) were covered by the PT scheme. The data were evaluated using robust statistics in order to determine a set of coefficients of variation (CV) for each analytical parameter. Concentration and time dependence of the CV were checked. The CV were combined to obtain standard deviations for proficiency assessment (Z-score criteria). Furthermore, a viewer program was designed to facilitate monitoring of the analytical performance of participating laboratories.     

Acrylamide analysis: assessment of results from six rounds of Food Analysis Performance Assessment Scheme (FAPAS) proficiency testing

Six proficiency tests have now been completed in an ongoing program of the UK Food Analysis Performance Assessment Scheme (FAPAS) for the analysis of acrylamide in a range of food matrixes. Homogeneous test material samples were requested by laboratories throughout the world, with 29 to 45 submitting results for each test. Results were analyzed by appropriate statistical procedures, and z-scores were awarded for reported values. In the absence of both legislation and collaborative trial data, the target standard deviation was derived from the Horwitz equation, although it is acknowledged that there is a need to establish a "fit for purpose" target standard deviation specifically for acrylamide analysis. Participants were encouraged to use the analytical method routinely used in their own laboratory and to provide details of their procedure. Close examination of the data submitted indicates that performance is generally acceptable in terms of accuracy. There is no significant difference between results submitted by gas chromatography and liquid chromatography (GC and LC) methods, and no method dependency on the use of internal standards or sample size. However, choice of extraction solvent may be important, with indications that plain water is an acceptable extraction method. There is evidence from the most recent test that direct (underivatized) GC methodology may present problems, but more data are required and this aspect will be monitored in the continuing proficiency testing program.     

Note on the bimodal distribution of PT results

The practitioner’s report "Treatment of bimodality in proficiency test of pH in bioethanol matrix" by Sarmanho et al. deals with a proficiency test (PT) for the measurement of pH in bioethanol. One group of 19 participating laboratories used an electrode that contained saturated LiCl and the other one KCl. The results of the LiCl group are biased, and those of the KCl group are unbiased as compared with the assigned reference value \(y_\mathrm{{RM}}\), and hence, the distribution of the laboratory means is bimodal. In order to deal with this situation, Sarmanho et al. present and carry out two different methods of fitting the bimodal distribution of the laboratory means: a fit by a mixture of two normal distributions and a Gaussian kernel estimation. Since this rather advanced statistical analysis does not help to solve the practical problem, some recomendations of ISO 17043 are discussed that might be useful for the coordinator of the PT and as well for the participating laboratories.     

The influence of a quality system according to ISO/IEC 17025 on the performance of Brazilian laboratories in proficiency testing in the environmental area

This paper presents a performance analysis of laboratories in proficiency testing (PT) with the main objective of evaluating whether having accreditation to ISO/IEC 17025 or not having an implemented quality system has an influence on the performance of these laboratories. This research was conducted with data from an accredited PT scheme of physical–chemical water analyses. Nine metals were considered in the analysis, with a total of 896 results. The performance indicator was z-score. The proposed analysis was conducted through statistical methods of analysis of variance, Dunnett’s test, Chi-square and cross-tabulation. It was verified that there is a significant difference between the performance of accredited laboratories, recognised laboratories, and laboratories that do not have an implemented quality system. It was established that an accredited or recognised quality system has a positive influence on the laboratory performance, resulting in a lower z-score (in module) and in a larger percentage of satisfactory results.     

Comparability and compatibility of proficiency testing results in schemes with a limited number of participants

Comparability and compatibility of proficiency testing (PT) results are discussed for schemes with a limited number of participants (less than 20–30) based on the use of reference materials (RMs) as test items. Since PT results are a kind of measurement/analysis/test result, their comparability is a property conditioned by traceability to measurement standards applied in the measurement process. At the same time, metrological traceability of the certified value of the RM (sent to PT participants as test items) is also important, since the PT results are compared with the RM certified value. The RM position in the calibration hierarchy of measurement standards sets the degree of comparability for PT results, which can be assessed in the scheme. However, this assessment is influenced by commutability (adequacy or match) of the matrix RM used for PT and routine samples. Compatibility of PT results is a characteristic of the collective (group) performance of the laboratories participating in PT that can be expressed as closeness of the distribution of the PT results to the distribution of the RM data. Achieving quality-of-measurement/analysis/test results in the framework of the concept “tested once, accepted everywhere” requires both comparability and compatibility of the test results.