MCM法和GUM法评定氨气检测仪示值误差不确定度的对比

氨气检测仪广泛应用于涉氨作业场所,为确保其测量结果准确可靠必须定期对其检定校准。针对其检定过程中示值误差的测量不确定度,对测量不确定度表示指南方法(GUM)和蒙特卡罗法(MCM)进行了对比研究。建立了氨气检测仪示值误差模型,分析了模型中各个变量的概率分布,利用MCM Alchimia软件进行了测量模型模拟计算,给出了模拟最佳值、不确定度及其包含区间,实现了氨气检测仪示值误差测量不确定度的蒙特卡洛法评定。与GUM法相比,蒙特卡洛法评定氨气检测仪示值误差测量不确定度具有通用性强、过程简单、结果可靠等优点,适合氨气检测仪示值误差的不确定度评价。     

自适应蒙特卡洛法测量复合肥料中缩二脲的不确定度

建立自适应蒙特卡洛法测量复合肥料中缩二脲的不确定度评定方法。依据ISO 18643:2016,使用高效液相色谱法对复合肥料中缩二脲含量进行测定,再利用计算机编程语言(Python)编写计算程序,使用自适应蒙特卡洛(MCM)法,通过建立测量模型、分解独立输入量、评估输入量概率分布、大量采样带入计算程序等步骤完成对缩二脲含量的测量不确定度评定。评定结果表明,复合肥料样品中缩二脲含量(质量分数)为(0.1054±0.0019)%(95%包含概率)。蒙特卡罗法计算过程简单直观,与传统方法JJF 1059.1—2012《测量不确定度评定与表示》(GUM)相比,避免了复杂的数学运算评定过程,无需进行多次重复测定,是GUM法的重要补充。     

蒙特卡洛法评定橡胶门尼黏度测量的不确定度

根据高聚物流变学原理,建立了门尼黏度测量模型,分析了模型中各个变量的概率分布,利用Mathcad软件进行了测量模型的门尼黏度模拟,给出了模拟最佳值、不确定度及其包含区间,实现了门尼黏度测量不确定度的蒙特卡洛法评定。与GUM法相比,蒙特卡洛法评定门尼黏度测量不确定度具有编程模式化,过程简单等优点,适合多变量测量模型的不确定度评价。     

基于R语言的蒙特卡洛法在不确定度评定中的应用

以盐酸溶液浓度标定试验为例,研究了基于R语言的蒙特卡洛法(MCM)在测量不确定度评定中的实际应用.将基于R语言的MCM计算结果和《测量不确定度表示指南》GUM法进行比较分析,两种方法的计算结果基本一致.MCM算得输出量的概率密度函数(PDF)与理论正态分布函数基本重合,且输出量PDF半宽与标准不确定度的比值k=1.95...     

基于自适应蒙特卡洛法评定测量不确定度程序开发与应用

进行了基于自适应蒙特卡洛法评定测量不确定度的程序开发与应用。基于Python语言,设计开发自适应蒙特卡洛法评定测量不确定度程序,包含评定过程框架、自定义变量名称模块、过程参数关联计算模块以及蒙特卡洛法采样计算模块。程序界面简洁,操作简单,计算准确,适用于任意多个独立变量、任意多个过程参数及单一被测量的数学模型,为利用自适应蒙特卡洛法评定测量不确定度提供了方便。     

渗透压摩尔浓度测定仪示值误差测量结果的不确定度评定

利用国家标准物质对渗透压摩尔浓度仪器的示值误差进行了重复检测,通过建立数学模型,对示值误差测量结果不确定度进行了评定,主要包括测量重复性、标准物质、仪器分辨力引入的不确定度。当测量点为200,400,500,600,700 mOsmol/kg时,相对扩展不确定度分别为0.95%,1.0%,0.7%,0.6%,0.5%(k=2)。     

辉光放电质谱仪的校准

建立了辉光放电质谱仪的校准方法。校准项目包括检测器噪声、分辨率、灵敏度、检出限、示值误差及重复性。经多家实验室的共同试验比对,提出并验证了计量性能指标,对示值误差进行了不确定度评定。其中,检测器噪声不大于1 c/s。在中分辨率模式下,分辨率不小于3500,灵敏度不小于1×10^(9) c/s。在高分辨率模式下,分辨率不小于8000,灵敏度不小于1×10^(8) c/s。检出限不大于7×10^(–7)%。示值误差不大于±20%。重复性不大于10%。该方法为辉光放电质谱仪的计量性能评价提供参考,推动相关计量技术规范的制定。     

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。     

浊度仪检定结果的不确定度评定

按照JJG 880-2006<浊度计检定规程>对浊度仪进行示值误差的检定,对检定结果的不确定度来源进行了分析,对各不确定度分量进行了评定并合成了标准不确定度.当浊度仪的示值误差为5.0%时,检定结果的扩展不确定度U=3.8% (k=2).     

大气采样器计量标准的测量不确定度

对大气采样器计量标准的测量不确定度来源如计量标准、流量示值误差、流量重复性、温度计示值误差进行了分析和评定,计算得合成标准不确定度和扩展不确定度分别为0.65%和1.30%.对测量不确定度的合理性进行了验证.     

Estimation of the standard uncertainty of a calibration curve: application to sulfur mass concentration determination in fuels

The construction of a calibration curve using least square linear regression is common in many analytical measurements, and it comprises an important uncertainty component of the whole analytical procedure uncertainty. In the present work, various methodologies are applied concerning the estimation of the standard uncertainty of a calibration curve used for the determination of sulfur mass concentration in fuels. The methodologies applied include the GUM uncertainty framework, the Kragten numerical method, the Monte Carlo method (MCM) as well as the approximate equation calculating the standard error of prediction. The standard uncertainty results obtained by all methodologies agree well (0.172?C0.175?ng???L^?1). Aspects of inappropriate use of the approximate equation of the standard error of prediction, which leads to overestimation or underestimation of calculated uncertainty, are discussed. Moreover, the importance of the correlation between calibration curve parameters (slope and intercept) within GUM, MCM and Kragten approaches is examined.     

化学计量中不确定度评定研究进展

测量不确定度是表征合理地赋予被测量之值的分散性的参数。本文针对化学计量不确定度评定基础模型仅适用于线性模型、概率分布为正态分布或缩放位移t分布等局限,介绍了近年来不确定度评定的研究热点:蒙特卡罗方法(Monte Carlo Method,MCM),不确定度评定的来源、评定概念、评估方法及其发展过程,扩大了测量不确定度评定与表示的适用范围。     

Comparison of ISO-GUM and Monte Carlo methods for the evaluation of measurement uncertainty: application to direct cadmium measurement in water by GFAAS

The propagation stage of uncertainty evaluation, known as the propagation of distributions, is in most cases approached by the GUM (Guide to the Expression of Uncertainty in Measurement) uncertainty framework which is based on the law of propagation of uncertainty assigned to various input quantities and the characterization of the measurand (output quantity) by a Gaussian or a t-distribution. Recently, a Supplement to the ISO-GUM was prepared by the JCGM (Joint Committee for Guides in Metrology). This Guide gives guidance on propagating probability distributions assigned to various input quantities through a numerical simulation (Monte Carlo Method) and determining a probability distribution for the measurand.In the present work the two approaches were used to estimate the uncertainty of the direct determination of cadmium in water by graphite furnace atomic absorption spectrometry (GFAAS). The expanded uncertainty results (at 95% confidence levels) obtained with the GUM Uncertainty Framework and the Monte Carlo Method at the concentration level of 3.01 μg/L were ±0.20 μg/L and ±0.18 μg/L, respectively. Thus, the GUM Uncertainty Framework slightly overestimates the overall uncertainty by 10%. Even after taking into account additional sources of uncertainty that the GUM Uncertainty Framework considers as negligible, the Monte Carlo gives again the same uncertainty result (±0.18 μg/L). The main source of this difference is the approximation used by the GUM Uncertainty Framework in estimating the standard uncertainty of the calibration curve produced by least squares regression. Although the GUM Uncertainty Framework proves to be adequate in this particular case, generally the Monte Carlo Method has features that avoid the assumptions and the limitations of the GUM Uncertainty Framework.     

Implementation in MATLAB of the adaptive Monte Carlo method for the evaluation of measurement uncertainties

The ISO 98:1995 Guide to the expression of uncertainty in measurement (GUM) presents important application limitations. For its improvement, different supplements are being developed that will progressively enter into effect. The first of these supplements describes an alternative method for calculating uncertainties, the Monte Carlo method (MCM), which is not restricted to the conditions of the method described in the GUM: the linearity of the model and the application of the central limit theorem. MCM requires computer calculation systems for generating pseudo-random numbers and for evaluating the model a large number of times. There are software applications that have been specifically developed for calculating uncertainties, some of which include MCM; but they do not allow the user to control all factors in the process, particularly the result stabilization criteria. On the contrary, its implementation in a mathematical program for general purposes such as MATLAB, enables total control over the process, is simple and benefits from its calculation speed. This article details programming in MATLAB for the implementation of the adaptive MCM method.     

化学需氧量在线自动监测仪示值误差的检定

介绍化学需氧量(COD)在线自动监测仪示值误差的检定方法及注意事项。选取基准试剂邻苯二甲酸氢钾,依次配制零点溶液和质量浓度分别为50,150,500 mg/L的COD标准物质溶液,用于检定COD maxⅡ型在线监测仪的示值误差。直接配制溶液为100 mg/L的COD标准溶液,与相同浓度的标准物质溶液GBW(E)082219进行比较,结果符合检定规程JJG 1012–2006的要求。检定结果表明:以重铬酸钾为氧化剂时,邻苯二甲酸氢钾的COD氧化值呈线性关系,可直接配制100 mg/L的COD标准溶液;检定COD maxⅡ型在线监测仪,每次需要的标准溶液体积为100 m L,综合考虑,进行示值误差检定时,每种浓度至少配制500 m L。作为还原性标准物质用于检定仪器示值误差,邻苯二甲酸氢钾可能无法准确反映水体中有机物的真实还原情况,具有一定的局限性。     

在线酸度仪校准装置的研制

为了提高在线酸度监测仪表的计量精度,使计量校准实现动态测量,研究了在线式酸度监测仪的校准方法,并根据校准方法研制了一种在线动态计量检定校准装置,该装置利用国家一级标准物质进行量值传递。整套装置模拟了在线酸度仪的工作状态,工作流速30－250mL／min,校准结果的不确定度为0．01pH,满足校准的要求。     

Reference measurement procedure for Δ9-tetrahydrocannabinol in serum

An isotope dilution gas chromatography/mass spectrometry (ID-GC/MS) reference measurement procedure for Δ9-tetrahydrocannabinol (THC) in serum was developed and validated. The method complies with the concept of a ratio primary reference measurement procedure. The uncertainty was determined for two concentrations of THC in serum (1 ng/mL and 2.4 ng/mL). The calculation procedure is based on the Guide to the Expression of Uncertainty in Measurement (GUM). The relative expanded uncertainty was found to be less than 2% for both concentration levels, corresponding to a 95% confidence interval. For the reference method, it was shown that the measurement of THC within the concentration range covered by the current threshold values is very accurate. The method has the potential to provide traceability for the methods used in practical forensics.     

基于气相色谱法危废品仓库中非甲烷总烃在线监测系统研制

研制了一套基于气相色谱法的危废品仓库中非甲烷总烃的在线监测系统。该系统采用气相色谱原理对样品进行分离,经火焰离子化检测器电离形成微电流,通过信号放大器检测并换算成烃类含量。经联动调试检测显示,系统的示值误差小于±2.5%,零点漂移小于±5%F.S.(传感器满量程误差的百分数),量程漂移小于±5%F.S.,响应时间小于300 s,系统各项技术性能指标均满足并优于《上海市固定污染源非甲烷总烃在线监测系统验收及运行技术要求》,具备推广和应用价值。     

石油产品微量残炭测定仪的校准

通过分析石油产品微量残炭测定仪的工作原理,参考相应的国家技术规范,建立石油产品微量残炭测定仪的校准方法,提出了示值误差、重复性等校准项目。采用残炭值为2.03%的油品残炭标准物质对石油产品微量残炭测定仪进行校准,其示值误差为0.04%,重复性为0.03%,对石油产品微量残炭测定仪示值误差测量结果的不确定度进行了评定,其扩展不确定度为0.15%(k=2)。该校准方法切实可行,可用于石油产品微量残炭测定仪的校准。     

大体积进样-浓缩柱在线富集-离子色谱法测定水中痕量及超痕量溴酸盐

建立了一种测定水中痕量及超痕量溴酸盐的在线富集大体积进样离子色谱法。采用实验室常备的柱容量较高的Dionex IonPac AG23保护柱作为浓缩柱,连接在定量环处富集溴酸盐。淋洗液自动发生装置在线生成高纯度氢氧化钾淋洗液进行梯度洗脱,抑制电导检测。实验结果表明:溴酸盐质量浓度范围在0.05~51.2 μg/L之间时线性关系良好,相关系数r≥0.9995,方法检出限为0.01 μg/L。与常规进样相比,进样量可高达5 mL,浓缩因子约为240倍。本方法成功应用于市售纯净水中溴酸盐的测定,2个加标水平的回收率在90%~100%之间,RSD(n=6)为2.1%~6.4%。该方法无需前处理,操作简单,准确度和精密度良好。通过大体积进样实现高倍富集,适用于痕量及超痕量溴酸盐的分析。