芥子气纯度测定不确定度分析与评定

采用酸碱滴定法测定芥子气纯度,对测量结果的不确定度进行评定。分析了测定过程中不确定度来源,包括滴定剂的标定、消耗滴定剂体积、样品称量等引入的不确定度及其计算方法,最后合成得到标准不确定度。当芥子气纯度测定结果为94.78%时,扩展不确定度为0.34%(k=2)。实验结果表明,样品称量引入的不确定度对测量结果的影响最大。     

多元素混合标准溶液中铜的不确定度评定

评定了多元素混合标准溶液中铜的不确定度。分析了混合标准溶液制备过程中不确定度的来源——所用铜片纯度、称量用电子天平、定容用移液管及容量瓶,并对各因素的影响进行了量化。计算结果表明影响合成不确定度的主要因素为制备过程中所用的玻璃量器。合成扩展不确定度为0.16%(k=2)。     

单扫描极谱法测定食品中苏丹红Ⅰ的不确定度评定

依据标准曲线法建立了单扫描极谱法测定食品中苏丹红Ⅰ的不确定度评定的数学模型,对影响测量结果的不确定度分量进行了分析,较全面地评定了测定结果的不确定度.单扫描极谱法测定食品中苏丹红Ⅰ的不确定度主要来源于峰电流的重复性、标准曲线的影响、样品称量、标准物质的纯度和称量、实验中量器的校准等因素,其中最主要的分量是通过标准曲线拟合求样品溶液浓度时引入的测量不确定度.     

分光光度法测定盐酸吗啡片含量的不确定度评定

采用分光光度法测定盐酸吗啡片含量,对测定结果的不确定度进行评定。依据《中国药典》2020年版二部通则0401和JJF 1059.1—2012 《测量不确定度评定与表示》,建立数学模型,分析不确定度来源。测量不确定度的主要来源包括：标准物质纯度、测量重复性、天平称量、溶液配制,其中标准物质纯度、溶液配制和天平称量对不确定度的影响较大。当置信区间为95%时,盐酸吗啡片含量测定结果为(5.003±0.028 7) mg(k=2)。盐酸吗啡片含量测量不确定度的准确评定,有助于控制药品的检测质量。     

液相原子荧光测定裙带菜中无机砷含量的不确定度评定

采用液相原子荧光测定裙带菜中无机砷含量,评定了测定过程的不确定度。通过对重复性实验引入的不确定度、标准物质和配制过程引入的不确定度、标准曲线拟合引入的不确定度、试样的称量质量引入的不确定度、仪器引入的不确定度以及定容体积引入的不确定度的计算,结果表明标准曲线的拟合是影响不确定度的主要因素,其次是重复实验和五价砷标样配制过程引入的不确定度。对某裙带菜待测样品,无机砷含量为0.080 5 mg/kg时,扩展不确定度为0.006 7 mg/kg。     

紫外可见分光光度计测定POM塑料中甲醛含量的不确定度评价

建立了分光光度法测定POM塑料中甲醛含量的不确定度评定数学模型。根据JJF 1059.1-2012标准要求与VDA 275-1994方法进行测定,从试样质量称量、重复性试验、试样水溶液的甲醛浓度、吸收液体积以及含水率测试五个方面分析测定过程中不确定度来源,并分别对其进行量化和和合成。结果表明,POM塑料中甲醛含量为5.015 mg/kg,扩展不确定度为0.254 mg/kg(k=2)。测定结果的不确定度主要来源于试样水溶液的甲醛浓度测试引入的不确定度,占比90.82%,其中线性拟合分量引入的不确定度贡献最大,占75.58%,其次是标液配制和仪器引入的不确定度分量,分别占13.41%和7.62%。因此在实际测量过程中,应重视仪器和量具的检定与核查,增加标准工作曲线的更新频次,以及规范试验操作步骤以提高测试结果的准确性;另一方面,称量、标液、含水率测试所引入的不确定度非常小,可忽略不计。     

高效液相色谱法测定化妆品中吡硫鎓锌等19种组分的不确定度评定

对采用高效液相色谱法测定吡硫鎓锌等19种组分含量，建立了方法的数学模型，分析了检测过程中的不确定度的来源，进行不确定度评定。测量不确定度主要来源包括：标准物质称量、玻璃量器移液定容、标准曲线、样品称量、样品定容、重复性、液相色谱仪。被测化妆品中吡硫鎓锌等19种组分的含量范围为0.004 4%～0.183 7%，当取置信概率为95%，包含因子k=2时，相应的扩展不确定度范围为0.000 1%～0.007 4%。标准物质称量、玻璃量器移液定容和标准曲线引入的不确定度分量为合成不确定度的主要贡献量，建议通过增加系列标准工作溶液实验点数，定期对仪器及量器进行检定和维护等方法减小测量结果的不确定度。     

茶叶中敌敌畏残留量检测的不确定度评定

依据SN/T 1950-2007方法,对茶叶中敌敌畏残留量的测量不确定度进行分析和评定.该检测过程所产生的测量不确定度主要来源于测量重复性、标准物质纯度、标准物质称量、标准溶液稀释、样品称量、定容体积、标样溶液峰面积和样品溶液峰面积的测量.分析结果表明:茶叶中敌敌畏残留量为0.050 mg/kg时,其扩展不确定度为0....     

原子荧光光度法测定铜精矿中汞含量不确定度评定

对原子荧光光度法测定铜精矿中汞含量的不确定度进行评定。不确定度分量分别来源于样品的重复性测量、标准溶液配制、标准曲线拟合、样品称量。实验过程中引入不确定度贡献较大的是标准曲线拟合和标准溶液配制过程,其次是样品的重复性测量。结果表明,铜精矿样品中汞含量（质量分数）测定结果为（0.001 86±0.000 04）%,k=2。     

红外吸收法测定碳含量的测量不确定度评定

对CCS-140型高频感应炉燃烧红外吸收法测定碳含量的不确定度进行了评定,分析了测量不确定度的主要来源,包括仪器的精密度引入的不确定度,标准物质标准值的不确定度,试样称量的不确定度,以及坩埚、助熔剂等引起的空白不确定度。当碳含量为0.366%时,测量结果的扩展不确定度为0.010%。     

蒸馏法测定化肥中氮含量的测量不确定度评定

对蒸馏法测定化肥中氮含量的测量不确定度进行了评定。分析了蒸馏法测定化肥中氮含量的不确定度的主要来源,通过数学模型对各不确定度分量进行了评定,采用蒸馏法测定化肥中氮含量的扩展不确定度为0．07％。     

气相色谱法测定人体血液中乙醇含量的测量不确定度评定

对气相色谱法测定人体血液中乙醇含量的测量不确定度进行评定。人体血液中乙醇含量测量结果的测量不确定度主要来源于相对定量校正因子、检材量、检材中添加内标物叔丁醇的体积、检材中乙醇峰面积的平均值与添加内标物叔丁醇峰面积的平均值之比、无水乙醇的纯度及密度等参数引起的不确定度。当检材中乙醇的含量为0．915mg／mL时,扩展不确定度为O．030mg/mL(k=2)。     

氮中多元标准混合气体的制备

研究用重量法制备氮中多元标准混合气体，对其制备原理、制备装置、气体称量装置，制备过程以及组分气体纯度的分析方法进行了介绍。分析了重量法制备氮中多元标准混合气体定值不确定度的来源，其定值的扩展不确定度小于3％。     

Uncertainty of nitrogen determination by the Kjeldahl method

 The uncertainty of the Kjeldahl method for determination of nitrogen in insulin was evaluated according the procedure described in the Guide to the Expression of Uncertainty in Measurement. The relative standard uncertainty of the method was found to be 0.19%, compared to the relative intermediate precision experimentally found to be 0.085%. The uncertainty components were organized in Tables, which allowed an easy overview and evaluation. The largest contribution to the uncertainty came from volumetric equipment. Systematic uncertainty budgets such as the design presented here facilitate the uncertainty evaluation process and makes it easier to compare uncertainty evaluations performed by different analysts. Received: 5 April 1999 / Accepted: 31 August 1999     

Effects of Nitrogen Composition on Fermentation Performance of Brewer's Yeast and the Absorption of Peptides with Different Molecular Weights

Four kinds of worts with different nitrogen compositions were used to examine their effects on fermentation performance of brewer's yeast. The absorption pattern of peptides with different molecular weights (Mw) in yeast cells during wort fermentation was also investigated. Results showed that both the nitrogen composition and level had significant impacts on the yeast biomass accumulation, ethanol production, and free amino nitrogen and sugars consumption rates. Worts supplemented with wheat gluten hydrolysates increased 11.5% of the biomass, 5.9% of fermentability, and 0.6% of ethanol content and decreased 25.6% of residual sugar content during wort fermentation. Moreover, yeast cells assimilated peptides with various Mw differently during fermentation. Peptides with Mw below 1 kDa decreased quickly, and the rate of assimilation was more than 50% at the end of fermentation, while those with Mw above 10 kDa almost could not be assimilated by yeast. All these results further indicated that the level and composition of wort nitrogen had significant impacts on the growth and fermentation performances of brewer's yeast, and peptides with Mw below 1 kDa were one of preferred nitrogen sources for brewer's yeast.     

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction (XRD), N2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature (<300 ?C) were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ?C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4+ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4+ and Pd2+ species on the surface, which might be favorable for the formation of active sites.     

Uncertainty calculation and implementation of the static volumetric method for the preparation of NO and SO2 standard gas mixtures

 The European Reference Laboratory of Air Pollution implements the static volumetric method for the preparation of nitrogen monoxide and sulphur dioxide reference standard gas mixtures. According to the new ISO guide for the expression of uncertainty, the uncertainty of these standards is up to 0.8% for nitrogen monoxide in the range 100 to 600 ppbv, and up to 0.4% for sulphur dioxide in the range 200 to 400 ppbv. The values presented in the present paper suggest that there is a 95% probability of the true value lying within the interval specified. To attain such low uncertainty values, the standard procedure for the implementation of the static volumetric method must be rigorously followed, and instruments must be carefully maintained. Received: 26 June 1997 · Accepted: 23 August 1997     

氧化燃烧发光法测定石油产品中氮含量的不确定度评定

对SH/T 0657-2007法测定石油产品中总氮含量的测量不确定度进行评定。分析了标准物质、分析操作、曲线回归、重复性测定等方面对不确定度的影响。结果表明,曲线回归及重复性测定对不确定度影响最大。当样品中总氮含量为3.40 mg/L时,总氮含量的扩展不确定度为0.11 mg/L(k=2)。     

Determination of Toluene and Ethanol in Urine by Headspace and Cryotrapping Gas Chromatography–Mass Spectrometry

Toluene is the major volatile organic compound found in glue and is often used as a hallucinogenic for abusers. Use with alcohol increases the risk of adverse effects from toluene exposure. In this study, a headspace and cryotrapping gas chromatography–mass spectrometry method was developed and validated for the determination of toluene and ethanol in urine. Experimental and instrumental variables were investigated to optimize the method for sensitivity. Excess sodium sulfate was used as the salting-out reagent before the headspace protocol. Linear least squares regression with a 1/x weighting factor was used to construct calibration curves from 0.002 to 0.4?µg?mL^?1 for toluene and 10 to 2000?µg?mL^?1 for ethanol. The correlation coefficients exceeded 0.9993. The limits of detection were 0.0005?µg?mL^?1 for toluene and 0.21?µg?mL^?1 for ethanol. Intraday and interday precisions were within 5.4 and 11.5%, while intraday and interday accuracies were between ?11.3 to ?4.0% and ?11.0 to 1.2%, respectively. The method validation results for selectivity and stability were satisfactory. The validation results were used to estimate the expanded uncertainty and the contribution of individual steps in the method for the quantification of toluene and ethanol. The relative expanded uncertainties were 14.1% for toluene and 4.6% for ethanol.     

元素分析仪测定土壤氮、碳含量的不确定度评定

用实例对元素分析仪测定土壤氮、碳含量不确定度进行评定.分析讨论了测定过程中不确定度的来源、不确定度分量的计算.结果表明,影响土壤碳、氮含量测定不确定度的主要因素是标准物质的引入和标准曲线的绘制.