转基因棉花Mon15 985 质粒标准物质多家验证实验研究及不确定度分析

对转基因棉花Mon15985实时荧光定量PCR方法进行了方法确认,组织多家实验室进行协同实验验证,对该标准物质参考值进行测定。经统计分析,得出Mon15985质粒分子的参考值为1.02,扩展不确定度为0.04（k=2）。质粒分子与转基因棉花Mon15985的基因组DNA相比,无论是扩增斜率还是线性相关性,均具有可替代性,该棉花转基因Mon15985质粒标准物质,可作为分析检测标准提供相关部门使用。     

转基因油菜Ms8质粒分子外/内源基因比值的不确定度评定

数字PCR是一项不依赖校准物的DNA绝对定量技术,通过统计(泊松分布)反应室中的阳性信号来定量DNA的拷贝数。该文对转基因油菜Ms8质粒分子进行构建和纯度分析后,采用荧光定量PCR对质粒分子的可替代性、均匀性和稳定性进行考察,采用数字PCR对质粒分子进行定值,并对测量结果进行不确定度评定。结果表明,数字PCR测得pMs8的外源基因和内源基因的比值及其不确定度为1.12±0.13,k=2。     

实验室新进人员比对方案及实施

本文针对实验室新进人员的比对,以数字压力计为例,详细介绍人员比对的方案和实施,包括比对样品的选取、标准器的选择、参考值的确定、不确定度的评定方法、比对结果的评价方法等.     

转基因番木瓜pUC57-Papaya质粒标准分子的构建与适用性研究

构建了含番木瓜2个内标准基因、4个筛选靶标及3个转化体特异性片段的质粒分子pUC57-Papaya,进行了适用性验证实验。应用普通PCR和实时荧光定量PCR对其进行互换性评估;使用质粒分子对2个样品进行转基因含量测定。结果显示：质粒分子全部9个目的片段按照设计排列,序列完全一致;全部9个基因片段普通PCR和实时荧光PCR方法均能正确扩增得到预期结果,特异性、灵敏度与基因组DNA一致;全部9个基因构建标准曲线做定量测试时,与基因组DNA标准曲线斜率无显著差异,线性相关系数均大于0.99,其中内标准基因Papain、NOS终止子、YK1601与55-1事件特异性片段的截距无差异;利用质粒分子测量2个样品的Papain、NOS终止子、YK1601与55-1事件特异性片段拷贝数,计算转基因含量,结果与基因组DNA一致;测序结果显示各片段拷贝数比值为1,质粒DNA拷贝数浓度为(2.54±0.10)×10⁶ copies/μL。构建的标准质粒分子可代替基因组DNA用于定量检测,也可作为转基因番木瓜定性和定量检测用标准物质。     

全血中血红蛋白检测方法的建立和验证

建立了基于氰化高铁血红蛋白定量检测人全血中血红蛋白的方法。该方法在0.3～1.8g/L范围内,线性相关系数为0.9994;日内精密度、日间精密度和重复性实验相对标准偏差分别为0.93%、1.14%和1.97%。用所建立的方法对Hb标准品进行了检测,检测值为116.67g/kg,符合Hb标准品证书值(119.7g/kg,不确定度为3.7g/kg,k=2)。本方法参与了由德国联邦物理技术研究院主导的血红蛋白国际比对,测试结果显示,样品浓度为124.36g/kg,扩展不确定度为2.14g/kg(k=2),比对结果与参考值等效一致。此方法操作简单,测量精确度高,重复性好,可作为全血中Hb标准物质的定值方法,为全血中Hb的日常检测提供参考。     

从验证比对试验结果的评定与分析谈对测量结果不确定度的评定

《中国计量》２０００年第６期刊登了《广东省砝码验证比对试验结果及分析》一文 ,文中用Ｅｎ 值法评定比对结果。Ｅｎ＝式中 :ｘｌａｂ———参加比对实验室的测量结果 ;ｘＲｅｆ———参考实验室的测量结果（参考值） ;Ｕｌａｂ———参加比对实验室的测量结果的扩展不确定度 ,置信概率Ｐ＝９９ % ;ＵＲｅｆ———参考实验室的测量结果的扩展不确定度 ,置信概率Ｐ＝９９ %。Ｅｎ值在０和 +１之间时表示参加比对的实验室测量结果与参考值之间是一致的 ;超过这个范围则说明参加比对的实验室的测量结果与参考值之间是不一致的 ,应对该测量进…     

对钢卷尺比对中体现问题的探讨

描述了一次完整的钢卷尺检定装置比对项目的实施和评价.包括该计量比对实施的背景、意义;所选取的实验样品、稳定性考核、参考值及不确定度的确定过程;参加实验室的分组情况;对参加实验室的结果予以图示后,着重展示此次比对中能体现典型问题的实验室图示,对其结果判定为不满意产生的原因进行探讨,并提出建议.     

比对参考值与等效度计算方法探讨

介绍了计算比对参考值的平均法和考虑了比对实验室量值与参考值的相关性的等效度不确定度计算方法,提出采用加权平均法计算参考值时应考虑比对传递或修正环节引入的不确定度对权重的影响,指出在分析计算参考值的不确定度或外部独立量值的最佳估计值的不确定度时应考虑实验室量值间的相关性的影响。     

缩宫素纯度测量的国际比对及国际互认

为实现缩宫素测量结果的溯源性、准确性、一致性和可比性，中国计量科学研究院与国际计量局联合主导了缩宫素纯度测量的国际比对，即CCQM-K115.b/P55.2.b。该比对于2016年开始，2020年完成，历时4年。国际计量局、中国、巴西、英国、日本、土耳其、墨西哥、马来西亚、加拿大等9个国家/国际组织的计量机构参加了该比对，采用质量平衡法、水解法、定量核磁法、元素分析法等4种方法完成了缩宫素比对样品的测量。经国际计量委员会蛋白质分析工作组讨论，参考值为（787.2±12.9）mg/g。在关键比对中，我国报告的质量平衡法结果为（796.5±6.5）mg/g，取得等效，且不确定度最小。基于该国际比对结果，我国申报了通用校准与测量能力，覆盖含单个二硫键、分子量小于5000道尔顿的多肽纯度测量，并于2021年发布在国际计量局的关键比对数据库，表明该能力取得国际互认。     

实验室比对数据处理中卡方统计量研究

卡方统计量是实验室比对数据处理的关键统计分析工具,可用于比对数据的一致性核验和参考值不确定度的估计.本研究在比对量具有相同期望及比对数据服从正态分布的条件下,提出了一种包含一般线性估计的卡方统计量,研究了该统计量的性质及分布.该统计量可以实现一般线性参考值估计的一致性检验和不确定度估计,为更广泛的线性参考值估计提供统计工具,可用于比对数据分析或多实验室定值测量.作为示例,针对算术平均值使用传统卡方检验需基于各实验室宣称相同不确定度的局限,对任意不确定度组合下的算术平均值给出卡方统计量,为这种常用线性参考值估计的扩展应用提供了新统计分析方法.     

Evaluation of digital PCR for absolute DNA quantification

The emerging technique of microfluidic digital PCR (dPCR) offers a unique approach to real-time quantitative PCR for measuring nucleic acids that may be particularly suited for low-level detection. In this study, we evaluated the quantitative capabilities of dPCR when measuring small amounts (<200 copies) of DNA and investigated parameters influencing technical performance. We used various DNA templates, matrixes, and assays to evaluate the precision, sensitivity and reproducibility of dPCR, and demonstrate that this technique can be highly reproducible when performed at different times and when different primer sets are targeting the same molecule. dPCR exhibited good analytical sensitivity and was reproducible outside the range recommended by the instrument manufacturer; detecting 16 estimated targets with high precision. The inclusion of carrier had no effect on this estimated quantity, but did improve measurement precision. We report disagreement when using dPCR to measure different template types and when comparing the estimated quantities by dPCR and UV spectrophotometry. Finally, we also demonstrate that preamplification can impose a significant measurement bias. These findings provide an independent assessment of low copy molecular measurement using dPCR and underline important factors for consideration in dPCR experimental design.     

Measurements of the Calorific Value of Methane with the New GERG Reference Calorimeter

A new reference calorimeter has been developed under a European research project and set-up by Physikalisch-Technische Bundesanstalt (PTB) in Germany. The objective of the project is to measure the superior calorific value (SCV) of methane and other pure gases with a measurement uncertainty of less than 0.05 %. This paper presents the measurement results obtained for methane. Nine repeatability measurements were made. The molar SCV obtained when the measurements were averaged is 890.578 kJ·mol^?1. This value agrees very accurately with the value of 890.63 kJ·mol^?1 specified by ISO 6976 [Natural Gas—Calculation of Calorific Values, Density, Relative Density and Wobbe Index from Composition. International Standard ISO 6976, corrected and reprinted 1996-02-01]. Twice the standard deviation determined for the measurements is 0.023 % and is thus clearly lower than in previous experiments. Two independent uncertainty analyses confirm that the envisaged total uncertainty of 0.05 % is achieved (95 % confidence level).     

Temperature-Resolved Infrared Spectral Emissivity of SiC and Pt–10Rh for Temperatures up to 900°C

This article reports the first comprehensive results obtained from a fully functional, recently established infrared spectral-emissivity measurement facility at the National Institute of Standards and Technology (NIST). First, sample surface temperatures are obtained with a radiometer using actual emittance values from a newly designed sphere reflectometer and a comparison between the radiometer temperatures and contact thermometry results is presented. Spectral emissivity measurements are made by comparison of the sample spectral radiance to that of a reference blackbody at a similar (but not identical) temperature. Initial materials selected for measurement are potential candidates for use as spectral emissivity standards or are of particular technical interest. Temperature-resolved measurements of the spectral directional emissivity of SiC and Pt–10Rh are performed in the spectral range of 2–20 μm, over a temperature range from 300 to 900°C at normal incidence. Further, a careful study of the uncertainty components of this measurement is presented.     

Quality Assurance of Rice and Paddy Moisture Measurements in Thailand

A bilateral comparison in moisture measurement between the National Institute of Metrology Thailand (NIMT) and the Central Bureau of Weights and Measures (CBWM) was organized for quality assuring of rice and paddy moisture measurement in Thailand. The bilateral comparison was conducted by using the same batch of sample and moisture meter as transfer device. It consisted of two parts: moisture measurement in rice and in paddy. A rice moisture meter belonging to CBWM and rice standards prepared at the nominal moisture content of 10 %, 12 %, 14 % and 16 % at NIMT, were used for rice moisture comparison, while a paddy moisture meter belonging to NIMT and paddy standards prepared at the nominal moisture content of 12 %, 14 %, 16 % and 18 % at CBWM, were used for paddy moisture comparison. Both laboratories measured the moisture content of a sample by using the standard method in ISO 712 and used that sample to calibrate a moisture meter by means of the method based on ISO 7700-1. Since the moisture content of the sample can change during the comparison, correction values in moisture content between the standard value and the reading value from the moisture meter are used as calibration results for the comparison evaluation. For the rice moisture comparison, differences in the correction value measured by the two laboratories vary from 0.18 % to 0.46 %, with their combined comparison uncertainty of 0.37 % (\(\hbox {k}= 2)\). The main contribution to the difference comes from the standard values from both laboratories differing from 0.27 % to 0.53 %, as the rice standard was found to drift in moisture content less than 0.05 %. Similarly to the rice moisture comparison, differences in the correction value for the paddy moisture measurement range from 0.08 % to 0.56 % with the combined comparison uncertainty of 0.38  % (\(\hbox {k} = 2)\), whereas the stability in moisture content of the paddy sample at NIMT was found to be within 0.12 %.     

CMM尺寸测量的不确定度评定模型研究

研究了坐标测量机(CMM)尺寸测量的不确定度评定方法。建立了符合ISO国际标准的测量不确定度评定黑箱模型。利用测量系统分析的方法,对6项量值特性指标引入的不确定度分量进行量化分析或实验标定,依据产品几何技术规范给出了各不确定度分量的评定模型。最后,通过工件直径测量的不确定度评定实例验证该方法的可行性。实验结果表明CMM尺寸测量的不确定度主要来源是偏倚和线性,不确定度分量为1.88μm,是所有其他分量合成的2倍以上,而温度补偿引入的不确定度分量仅为0.04μm,在实际测量中可忽略不计。     

Adiabatic Calorimetry as Support to the Certification of High-Purity Liquid Reference Materials

The certification of high-purity liquid reference materials is supported by several analytical techniques (e.g., gas chromatography, liquid chromatography, Karl Fischer coulometry, inductively coupled plasma mass spectrometry, differential scanning calorimetry, adiabatic calorimetry). Most of them provide information on a limited set of specific impurities present in the sample (indirect methods). Adiabatic calorimetry [1] complementarily provides the overall molar fraction of impurities with sensitivity down to few μmol · mol⁻¹ without giving any information about the nature of the impurities present in the sample (direct method). As the combination of adiabatic calorimetry with one (or more than one) indirect chemical techniques was regarded as an optimal methodology, NMi VSL developed an adiabatic calorimetry facility for the purity determination of high-purity liquid reference materials [2]. Within the framework of collaboration with NMIJ, a benzene-certified reference material (NMIJ CRM 4002) from NMIJ was analyzed by adiabatic calorimetry at NMi VSL. The results of this measurement are reported in this paper. Good agreement with the NMIJ-certified purity value (99.992 ± 0.003) cmol · mol⁻¹ was found. The influence of different data analysis approaches (e.g., extrapolation functions, melting ranges) on the measurement results is reported. The uncertainty of the measured purity was estimated.     

气相色谱内标法测定塑料制品中乙苯和苯乙烯含量的不确定度评定

目的 对气相色谱内标法测定塑料制品中乙苯和苯乙烯含量进行不确定度评定，为塑料制品中乙苯、苯乙烯含量测定的准确性提供参考。方法 依据GB 31604.16—2016采用气相色谱内标法对塑料制品中乙苯和苯乙烯含量进行测定，根据相应的测量模型，分析不确定度主要影响因素的来源，并对各影响因素引入的相对标准不确定度进行评估。结果 测量塑料制品中乙苯、苯乙烯的扩展不确定度分别为(23.83±1.50)、(23.90±1.26)mg/kg(P=95%、k=2)。结论 结果表明，混标工作液配制、试样重复测量、气相色谱仪性能是影响乙苯和苯乙烯含量测量不确定度的主要因素，应选择精度高且量程合适的量具，加强气相色谱仪的期间核查，提高实验人员操作的熟练水平，进一步减小测量不确定度，使测量结果更为准确、可靠。     

Detection of aneuploidy with digital polymerase chain reaction

The widespread use of genetic testing in high-risk pregnancies has created strong interest in rapid and accurate molecular diagnostics for common chromosomal aneuploidies. We show here that digital polymerase chain reaction (dPCR) can be used for accurate measurement of trisomy 21 (Down syndrome), the most common human aneuploidy. dPCR is generally applicable to any aneuploidy, does not depend on allelic distribution or gender, and is able to detect signals in the presence of mosaics or contaminating maternal DNA.     

动态谐振法测量纵向压电应变常数的不确定度评定

基于阻抗分析仪和Labview平台建立了d33动态谐振法自动测量系统,选择柱状压电陶瓷NCE51进行特征参数的测试,通过分析压电常数测量的数学模型,对测量频率步长进行优化,对测试结果进行不确定度评定。结果表明,不同厚度的试样,频率步长要求不同,厚度为15mm的试样,在频率步长为50Hz时,纵向压电常数扩展不确定度为0.96% (k=2）,可以满足目前商用准静态测量仪2%～5%的测量不确定度量传需求。     

Preparation of Honey Reference Material for Water Content by Karl Fisher and Refractometric Methods

Certified reference materials are essential tools for calibration of measuring instruments, validation of analytical methods and assuring quality of measurement results. However, in the case of water content in honey, which is used to determine the quality and the marketability of honey, there is a lack of matrix reference materials. Certified reference material for water content in honey has been developed by the National Institute of Standards, Egypt. This article describes production of the material from processing to value assignment. Characterization of the material was carried out by refractometric and Karl Fisher titration procedures, where homogeneity and stability studies were carried out by Karl Fisher titration method. The measurement results were statistically analysed and weighted mean was calculated as assigned value. The certified value and expanded uncertainty were found 16.24 ± 0.33 g/100 g, respectively.