2011年约稿： 电感耦合等离子体原子发射光谱法测定铜合金中锆量的不确定度评定

讨论了采用电感耦合等离子体发射光谱法测定铜合金中锆量分析结果不确定度产生的原因。建立了数学模型,对测量重复性,标准溶液,标准曲线变动性,试液体积,试样称量,数字修约等引起的不确定分量进行评定,计算了合成标准不确定度和扩展不确定度,并给出铜合金中锆量测定结果的报告。评定结果表明：测量重复性,标准曲线线性回归引起的不确定度对总不确定度影响最大。所以,在测定中应进行多次平行测定,特别注意标准曲线的校正和绘制校准曲线所用标准样品的选择。     

Uncertainty due to volumetric operations is often underestimated

Fifteen international titration standards were evaluated to determine minimum and maximum combined standard uncertainties. Assuming most thorough performance of the analyses revealed minimum values, whereas maximum values of uncertainty were obtained assuming that the analyses had been done under high time pressure. Minimum and maximum uncertainties were compared with the corresponding reproducibility standard deviations. Since the combined standard uncertainty is expected to lie between the reproducibility standard deviation and the maximum combined standard uncertainty, realistic standard uncertainties of individual influence quantities of volumetric and weighing procedures could be calculated. This top-down approach revealed up to 4 times higher uncertainties for volumetric operations compared to the bottom-up approach according to the current literature. Hence, uncertainty due to volumetric operations is obviously strongly underestimated. The present study additionally contains a ranking of the contributions to the uncertainty of titrimetric results.     

Uncertainty budget for high temperature heat flux DSCs

This study addresses the lack of published information regarding uncertainty for high temperature heat flux differential scanning calorimeters. No data were found in the existing literature stating an uncertainty budget for temperatures above 1,000 °C. The presented results identify the main influencing factor for uncertainty with the instruments used—measurement repeatability—up to a temperature of 1,400 °C. Results show findings from analyzing a series of repeated baseline and sapphire measurements and the influence from different working equations. The uncertainty budget for temperature calibration of DSCs is crucial in cases where accuracy in temperature is significant. Data are also provided from repeated temperature calibrations on the melting point of pure metals from a supplied standard set that comes with the instrument. In addition, carbon eutectics have been used to address an issue resulting from the lack of available calibration materials for high temperatures up to 1,500 °C (above the melting point of gold).     

Repeatability: some aspects concerning the evaluation of the measurement uncertainty

Various publications stress the importance of the repeatability (i.e. precision) of the calculation of the measurement of uncertainty. We reveal by detailing an example from production control in the pharmaceutical industry that the effect of other influence quantities should not be neglected, because their magnitude is even larger than the contribution of repeatability. We review the role of repeatability within the calculation of measurement uncertainty for several common validation and day-to-day measurement scenarios. They show that measurement models need to consider the measurement sequences of the various scenarios. Otherwise the size and effect of the repeatability might be overestimated. At the end Monte Carlo simulations were used to investigate the determination of the repeatability under certain restrictions. The simulation uncovered a significant bias toward the common formula for calculating the standard deviation when it is based on a duplicated measurement of a sample. Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher     

高效液相色谱法测定车内非金属材料中甲醛含量的不确定度评估

依据测量不确定度评定与表示的方法,建立了高效液相色谱法测定车内非金属材料中甲醛含量的测量不确定度评定的数学模型,并对测试过程中各个不确定度分量的来源进行了分析和合成.结果表明,标准曲线的拟合和试验重复性对结果有较大影响.通过规范标准溶液配制的操作,降低测量结果的不确定度,有利于提高检测的准确性和一致性.     

高效液相色谱法测定氨基酸口服液中L-色氨酸的不确定度评定

采用高效液相色谱法测定氨基酸口服液中L-色氨酸的含量,对测量结果的不确定度进行评定。结果表明,标准曲线校准和测量重复性是测量过程中不确定度的主要来源,其中标准曲线校准对合成不确定度的影响最大。当氨基酸口服液中L-色氨酸的测定结果为8.8μg/mL时,其扩展不确定度为1.1μg/mL。     

原子荧光法测定水中总锑含量的不确定度评定

根据原子荧光光度法,用AFS-9700双道原子荧光光度计测定水样中的总锑含量,并且分析了主要的测量不确定度来源,即标准溶液引入的不确定度、建立工作曲线引入的不确定度、回收率引入的不确定度和重复测量样品引入的不确定度,对测量不确定度进行计算和评定,合成测得总锑含量的不确定度为0.10?g/L。     

高效液相色谱法测定马来酸氯苯那敏含量的测量不确定度

分析了高效液相色谱法测定马来酸氯苯那敏含量测量不确定度的来源,评定了马来酸氯苯那敏含量测量过程中测量的重复性、天平、吸管、容量瓶、马来酸氯苯那敏对照品的纯度、对照品色谱峰面积和供试品色谱峰面积等因素对马来酸氯苯那敏含量测定不确定度的影响,计算得测定结果的相对扩展不确定度为2．0％。     

Assessment of uncertainty in calibration of a gas mass flowmeter

 A primary calibration system was set up in Rafael some years ago, based on volumetric flow rate. The primary standard measures volumetric flow by means of the volume change of a dual piston over a specific time interval. This system serves to calibrate secondary standards of the thermal mass flowmeter type. Calibration procedures were prepared and validated. The paper describes the tests and calibration procedure conducted for the uncertainty assessment, the different components contributing to the measurement uncertainties, and the formulas involved with volumetric flow fates and with thermal mass flowmeters. Received: 10 July 1999 / Accepted: 15 February 2000     

Uncertainty of carboxyhaemoglobin determination in putrefied blood by headspace gas chromatography

The uncertainty of carboxyhaemoglobin (COHb) determination in post-mortem blood samples by headspace gas chromatography with the use of methanizer and flame ionization detector was estimated. Four main components of uncertainty were identified, i.e. calibration, measurement repeatability, standard solutions preparation and sample preparation, and their contributions to the combined uncertainty were determined. The calibration step was the dominating source of uncertainty, counting for more than 39 % of overall variance. The contribution of remaining sources to the combined uncertainty was lower than 31 % (measurement repeatability), 21 % (standards preparation) and 12 % (sample preparation). The calculated absolute expanded uncertainty in samples containing 3.8–82 % mass fraction of COHb ranged between 2.2 % and 2.6 % (coverage factor 2), depending only slightly on the analyte level in the analysed sample.     

丙酮中除虫脲溶液标准物质研制

采用重量-容量法制备丙酮中除虫脲溶液标准物质。准确称量国家二级标准物质除虫脲溶解到色谱纯丙酮中,通过A级容量瓶定容至500 mL,摇匀后分装到2 mL安瓿瓶内共460瓶,每瓶为1 mL,保持低温迅速封口,配制过程中室温保持在(20±2)℃。采用液相色谱法进行均匀性、稳定性检验和定值结果验证。从样品中随机抽取16瓶进行均匀性检验,经F检验表明,在95%的置信区间范围内该标准物质均匀性良好;采用t检验对标准物质稳定性进行检验,标准物质在12月内稳定性良好。对该标准物质的不确定度进行了评定,研制的丙酮中除虫脲溶液标准物质定值结果为100μg/mL,相对扩展不确定度为2%(k=2)。结果表明,该标准物质均匀性与稳定性良好,量值准确,可用于日常分析检测中的方法评价和仪器校准。     

镍水质在线自动监测仪校准方法

通过分析镍水质在线自动监测仪工作原理及结构,探讨其计量特性和校准方法。提出了校准项目和技术指标,示值误差:当镍的质量浓度c≤0.05 mg/L时为±0.01 mg/L,当0.05 mg/Lc≤0.2 mg/L时为±10%,当c0.2mg/L时为±5%;重复性不大于5%;稳定性不大于5%。对示值误差测量结果不确定度进行了评定,相对扩展不确定度为1.6%(k=2)。用所建校准方法对不同厂家的监测仪进行校准试验,示值误差、重复性、稳定性满足校准项目技术指标要求。该校准方法可以用于评价镍水质在线自动监测仪的性能。     

Estimation of the measurement uncertainty of the high-performance anion-exchange chromatographic determination of carbohydrates in soluble (instant) coffee

The measurement uncertainty of the determination of free and total carbohydrates in soluble (instant) coffee using high-performance anion exchange chromatography with pulsed amperometric detection according to AOAC Method 995.13 and ISO standard 11292 was calculated. This method is important with regard to monitoring several carbohydrate concentrations and is used to assess the authenticity of soluble coffee. We followed the recommendations of the ISO, Eurachem, and Valid Analytical Measurement (VAM) guides: individual uncertainty contributions u(x) were identified, quantified, and expressed as relative standard deviations related to each specific source u(x)/x or RSD(x). Eventually, they were combined to yield the standard uncertainty and the relative standard uncertainty of a given carbohydrate concentration, c, that is respectively u(c) and u(c)/c. As a result of our study, we could demonstrate that the overall repeatability of the carbohydrate determination in duplicate, RSD(r); the repeatability of the integration of the peak area of the carbohydrate standards, RSD(r(area)(ST)); and the uncertainty of the linear calibration model used in our laboratory, RSD (linST), are the most significant contributions to the total uncertainty. The u(c)/c values thus determined differ for each carbohydrate and depend on their concentrations. The least standard uncertainties that can be achieved are about 2.5%. The question of trueness in the total carbohydrate assay (determination of monosaccharides obtained upon hydrolysis of coffee oligo- and polysaccharides) was addressed. For this purpose, we analyzed the data of 2 different collaborative trials in which our laboratory took part.     

硫氰酸盐光度法测定低合金钢中钼的测量不确定度评定

用硫氰酸盐分光光度法测定低合金钢中钼的含量,对测定过程中的不确定分量进行了分析和评定.测量不确定度主要来源于试料称量、标准溶液、校准曲线拟合、玻璃仪器的使用及测量重复性.当钼的含量为0.181%时,其扩展不确定度为0.0064%(k=2).     

不锈钢1Cr18Ni9Ti中铬含量测量不确定度的评定

采用国际通用的方法研究了过硫酸铵氧化容量法测定铬含量的不确定度,分析了容量法中摩尔质量、样品质量、溶液的体积、温度等因素对测量不确定度的影响,评估了各参数的标准不确定度、合成标准不确定度和扩展不确定度。找出了影响容量法测定铬含量准确度的主要原因。     

The Japanese traceability system and the role of uncertainty evaluation in measurement

 The new traceability system of measurement standards based on the Japanese Measurement Law has been established since November 1993. Some reference materials such as metal standard solutions, pH standard solutions and standard gas mixtures are included in the system together with relevant physical quantities. In this system, primary measurement standard instruments or primary reference materials are designated by the regulation for each quantity. For the practical dissemination of each quantity, accreditation of calibration bodies is recognized by the steering committee under the supervision of the government. In the course of assessment of a candidate calibration body, the concepts of ISO/IEC Guide 25 and ISO/IEC Guide 58 are effectively introduced. For the estimation of reliability, the concept of how to introduce the statistical approach is effectively considered. The method of uncertainty evaluation described in the ISO document entitled "Guide to the expression of uncertainty in measurement" is adopted.     

Uncertainty evaluation in the analysis of biological samples by sector field inductively coupled plasma mass spectrometry. Part A: measurements of Be,Cd, Hg,Ir, Pb,Pd, Pt,Rh, Sb,U, Tl and W in human serum

A protocol that utilises data (trueness/recovery, precision and robustness) from validation tests to calculate measurement uncertainty was described and applied to a sector field inductively coupled plasma mass spectrometry (SF‐ICP‐MS)‐based method for the determination of Be, Cd, Hg, Ir, Pb, Pd, Pt, Rh, Sb, U, Tl and W in human serum. The method was validated according to criteria issued by international bodies such as AOAC, Eurachem and ISO and the uncertainty in the analytical measurements was estimated following the Eurachem/Citac guide. The methodology was based on dilution of human serum with water and analysis by serum‐matched standard calibration. The method quantification limits ranged 0.02 µg/L (Tl, Ir) to 0.26 µg/L (Hg). The coefficients of regression were greater than 0.9991 over a range of two orders of magnitude of concentration. The mean trueness was 101% and the mean recovery on three levels of fortification (1‐, 1.5‐, and 2‐times the baseline serum level) ranged between 93.3% and 106%. The maximum relative standard deviation values for repeatability and within‐laboratory reproducibility were 12.8% and 13.5%. The method was robust to slight variations of some critical factors relevant to the sample preparation and SF‐ICP‐MS instrumentation. The relative expanded uncertainty over three levels of concentration ranged from 11.6% (Hg) to 27.6% (Pt), and the uncertainty on the within‐laboratory reproducibility, which included factors such as time, analyst and calibration, represented the main contribution to the overall uncertainty. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of measurement uncertainty for the determination of triazines in groundwater from validation data

Laboratories are increasingly urged to submit full uncertainties of their analytical results rather than only standard deviations. The determination of measurement uncertainties in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) is demonstrated using the validation approach explicitly endorsed by the recent edition of the EURACHEM guide for the determination of measurement uncertainty. Measurement uncertainty was split into uncertainty of the sample mass, uncertainty of the concentration of the stock standard solution, uncertainty of the calibration and uncertainty connected to within- and between-series precision. Uncertainties of sample mass and of the concentration of the stock standard solution were 0.26 and 1.14% for all analytes, which is negligible compared with the contributions of precision and calibration. Uncertainty of calibration was estimated from the calibration graph. Relative uncertainty of calibration was found to be strongly concentration dependent and to be the main uncertainty contribution below 0.2 microgram L-1. Precision was split into within-series and between-series standard deviation, which dominate the combined standard uncertainty at higher concentrations. The results obtained from these calculations are compared with results for a certified reference material and with the performance in an interlaboratory comparison. It was found that all results agreed within their uncertainty with the target values, showing that the estimated uncertainties are realistic.     

复混肥料中氯离子含量测量不确定度的评定

对硫氰酸铵滴定法测定复混肥料中氯离子含量的测量不确定度进行了评定。分析了测量重复性、滴定管、标准溶液浓度等因素对氯离子含量测量不确定度的影响。计算得复混肥料中氯离子含量测定结果的扩展不确定度为0．049％。     

电感耦合等离子体原子发射光谱法测定铜合金中锆量的不确定度评定

讨论了采用电感耦合等离子体发射光谱法测定铜合金中锆量分析结果不确定度产生的原因。建立了数学模型,对测量重复性,标准溶液,标准曲线变动,试液体积,试样称量,数字修约等引起的不确定分量进行评定,计算了合成标准不确定度和扩展不确定度,并给出铜合金中锆量测定结果的报告。评定结果表明:测量重复性,标准曲线线性回归引起的不确定度对总不确定度影响最大。所以在测定中应进行多次平行测定,特别注意标准曲线的校正和绘制校准曲线所用标准样品的选择。