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。     

原子吸收光谱法测量不确定度的评定与应用

介绍了测量不确定度的一般评定方法。并以火焰原子吸收光谱法测定奶粉中铜含量为例,研究了原子吸收光谱法不确定度的评定步骤和计算过程。     

离子色谱法测定地下水中硝酸盐氮含量的不确定度评定

采用不确定度连续传递模式,讨论了不同回归方式对离子色谱法测定岩溶地下水中硝酸根分析结果不确定度评定的差异.结果表明：（1）测定结果的不确定度主要来源于标准溶液配制过程引入的不确定度、校准曲线拟合及回归过程产生的不确定度和仪器测定过程引入的不确定度三部分;（2）不同校准曲线回归方式对测定结果的不确定度评定在不同测量水平上有不同的影响,当地下水中硝酸根含量越低,差异越大.此外,对不确定度评定过程中的各个分量进行量化,通过合成得到硝酸根测定结果的不确定度评定模型.     

An assessment of contemporary atomic spectroscopic techniques for the determination of lead in blood and urine matrices

The preparation and validation of a number of clinical reference materials for the determination of lead in blood and urine is described. Four candidate blood lead reference materials (Lots, 047–050), and four candidate urine lead reference materials (Lots, 034, 035, 037 and 038), containing physiologically-bound lead at clinically relevant concentrations, were circulated to up to 21 selected laboratories specializing in this analysis. Results from two interlaboratory studies were used to establish certified values and uncertainty estimates for these reference materials. These data also provided an assessment of current laboratory techniques for the measurement of lead in blood and urine. For the blood lead measurements, four laboratories used electrothermal atomization AAS, three used anodic stripping voltammetry and one used both ETAAS and ICP-MS. For the urine lead measurements, 11 laboratories used ETAAS (most with Zeeman background correction) and 10 used ICP-MS. Certified blood lead concentrations, ±S.D., ranged from 5.9±0.4 μg/dl (0.28±0.02 μmol/l) to 76.0±2.2 μg/dl (3.67±0.11 μmol/l) and urine lead concentrations ranged from 98±5 μg/l (0.47±0.02 μmol/l) to 641±36 μg/l (3.09±0.17 μmol/l). The highest concentration blood lead material was subjected to multiple analyses using ETAAS over an extended time period. The data indicate that more stringent internal quality control practices are necessary to improve long-term precision. While the certification of blood lead materials was accomplished in a manner consistent with established practices, the urine lead materials proved more troublesome, particularly at concentrations above 600 μg/l (2.90 μmol/l).     

原子吸收光谱法测定载金碳中金含量的不确定度评定

介绍了原子吸收光谱法(AAS)测定载金碳中金含量的不确定度评定方法。建立了不确定度评定的数学模型,对不确定度来源进行分析,并对不确定度分量进行量化。测量不确定度的主要来源为测量重复性引入的标准不确定度、样品称量引入的标准不确定度、样品溶液中金含量测定值的标准不确定度、样品溶解后定容体积的不确定度,其中测量重复性引入的标准不确定度和样品溶液中金含量测定值引入的标准不确定度为不确定度主要来源。当载金碳中金含量为0.56 g/kg时,其扩展不确定度为0.02 g/kg(k=2)。     

Uncertainty estimation in chemical measurements: carbon dioxide determination at atmospheric concentration

The present work deals with the evaluation of measurement uncertainty in the determination of carbon dioxide (CO2) concentration in atmosphere, given the high relevance of this greenhouse gas that influences earth climate. In order to carry out CO2 measurements, non dispersive infrared (NDIR) analysers are usually employed as they are stable and scarcely affected by interferences from other air components or pollutants. Typical uncertainty sources are the resolution of the analyser, its time drift and the contributions due to instrument calibration, which is required in order to produce traceable measurement results. The calibration uncertainty takes into account the uncertainty of the composition of the calibration gas mixtures, the instrument repeatability and the possible or residual lack of fit of the adopted mathematical model.     

Direct determination of lead at sub-ppb levels in secondary coolants of pressurized water reactor by electrothermal atomic absorption spectrometry with multiple injections

The method of incorporating in-situ pre-concentration technique via multiple injections followed by electrothermal atomic absorption spectrometry (ETAAS) is described for the direct determination of lead at sub-ppb levels in secondary coolants of pressurized water reactor (PWR). Prior to ETAAS measurement, water samples were concentrated by means of multiple injections (9×90 ml) and evaporation in a pyrocoated graphite tube. Optimization of the in-situ pre-concentration via multiple injections with ETAAS analysis was investigated. The feasibility of the proposed method was tested for direct determination of lead in secondary coolants of pressurized water reactor. A SRM 1643c certified reference water sample has been used for quality control. The result are in good agreement with the certified value. By the use of 0.81 ml sample volume 0.012 ppb detection limit was obtained.     

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。     

火焰原子吸收光谱法测定水中锰的不确定度评定

为建立并运用火焰原子吸收光谱法测定生活饮用水中锰的不确定度评定方法,根据《不确定度评定与表示》,并参考《化学分析测量不确定度的评定指南》,对火焰原子吸收法测定生活饮用水中锰进行了不确定度的分析和评价。结果表明,合成不确定度0.006 7 mg/L,扩展不确定度0.013 mg/L。运用该不确定度评定分析方法对测量过程中的关键环节进行重点质量控制,可有效降低引入的不确定度,保证测定结果准确。     

原子吸收光谱法测定铜阳极泥中Bi的不确定度评定

探讨了用原子吸收光谱法测定铜阳极泥中铋的不确定度的评定,阐述了测量结果不确定度主要来源于样品称量、试液定容体积和测量试液中铋的浓度产生的不确定度,计算了这些不确定的分量,最后计算出合成标准不确定度和扩展不确定度.通过评估,得出影响铋量测量不确定度的主要因素是测量试液中铋浓度时所引起的不确定度.     

An approach to detection capabilities estimation of analytical procedures based on measurement uncertainty

Detection capabilities are important performance characteristics of analytical procedures. There are several conceptual approaches on the subject, but in most of them a level of ambiguity is presented. It is not clear which conditions of measurements should be used, and there is a relative lack of definition concerning blanks. Moreover, there are no systematic experimental studies concerning the influence of uncertainty associated with bias evaluation. A new approach based on measurement uncertainty is presented for estimating quantities that characterize capabilities of detection. It can be applied to different conditions of measurement and it is not necessary to perform an additional experiment with blanks. Starting from a modelling process of the combined uncertainty of concentration, it is possible to include in the estimated quantities the effects due to random errors and the uncertainty associated to evaluation of bias. The detection capabilities are then compared with the results obtained using some other relevant approaches. Slightly higher values were obtained with the measurement uncertainty approach due to inclusion of uncertainty associated with bias.     

Preconcentration of trace amounts of cadmium in aqueous samples on minicolumns packed with Chromosorb series gas chromatographic stationary phases and its determination by electrothermal atomic absorption spectrometry.

The adsorption characteristics of five commercially available Chromosorb GC stationary phases towards Cd2+ and their application to the preconcentration and ETAAS determination of Cd2+ in several water samples were studied. The experimental results indicated that although all of the five Chromosorb GC stationary phases studied can retain Cd2+ quantitatively from aqueous solutions at appropriate pH values without adding chelating reagent. Chromosorb 105 displayed the highest adsorption capacity. A highly sensitive, simple methodology for preconcentration and ETAAS determination of trace amounts of cadmium in natural water samples using a Chromosorb 105 packed minicolumn is proposed. Conditions for quantitative and reproducible preconcentration, elution and subsequent ETAAS determination were established. The high retention efficiency (> 95%) for Cd2+ provides a sensitivity enhancement of 100-fold for a 200 mL sample volume with a detection limit of 6.2 ng L(-1) (3 sigma).     

Cloud point extraction for the determination of As(III) in water samples by electrothermal atomic absorption spectrometry

Cloud point extraction was applied as a preconcentration step for electrothermal atomic absorption spectrometry (ETAAS) determination of As(III) in aqueous solutions. After complexation with ammonium pyrrolidinedithiocarbamate, the analyte was quantitatively extracted to the surfactant-rich phase in the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) after centrifugation. 0.1 mol L⁻¹ HNO₃ in methanol was added to the surfactant-rich phase before ETAAS determination. The precision (R.S.D.) for 11 replicate determinations of 5.0 μg L⁻¹ of As(III) was 3.0%. The concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for ETAAS determination and in the initial solution, was 36 for As(III). The linear concentration range was from 0.1 to 20 μg L⁻¹. The developed method was applied to the determination of As(III) in lake water and river water.     

电感耦合等离子体质谱法测定岩石中47种元素的不确定度评定

采用封闭酸溶电感耦合等离子体质谱(ICP-MS)法测定岩石样品,分别对47种元素的测量结果不确定度进行评定。通过分析测试方法和测量条件,得到测量结果的不确定度主要由样品称量、样品溶液定容和样品溶液中元素浓度测量引入。在实验室质控条件下,对各不确定度分量进行评定和计算,其中随机因素导致的不确定度采用期间精密度试验综合评价,即采用A类方法评定。共完成了16个岩石国家标准物质(GBW 07103~GBW 07123)47种元素测量结果的不确定度合成,并参照GB/T 6379.2-2004,建立了含量w与扩展不确定度U之间的关系模型,运用这一关系模型可得到测量结果的不确定度估计值,只要测量过程本身或所使用的设备未变化,就不需要再重复进行不确定度评估。     

5-Br-PADAP光度法测钒钛磁铁矿中钒的不确定度评定

5-Br-PADAP光度法是测钒钛磁铁矿中钒的主要方法之一。根据其分析过程的操作步骤确定了其影响因素。建立数学模型,并根据数学模型把不确定度分解为称样质量、溶液含量、钒标准工作曲线和重复测定引入的各不确定度,对影响测量结果的各个分量进行了分析评定和计算。结果表明,钒的标准工作曲线的建立是影响样品分析误差的重要因素。     

Practical estimation of the uncertainty of analytical measurement standards

Nowadays, a lot of time and resources are used to determine the quality of goods and services. As a consequence, the quality of measurements themselves, e.g., the metrological traceability of the measured quantity values is essential to allow a proper evaluation of the results with regard to specifications and regulatory limits. This requires knowledge of the measurement uncertainties of all quantity values involved in the measurement procedure, including measurement standards. This study shows how the uncertainties due to the preparation, as well as the chemical and compositional stability of a chemical measurement standard, or calibrator, can be estimated. The results show that the relative standard uncertainty of the concentration value of a typical analytical measurement standard runs up to 2.8% after 1 year. Of this, 1.9% originates from the preparation of the measurement standard, while 2.0 and 0.53% originate from the chemical and compositional stability during storage at −20 °C. The monthly preparation of working calibrators stored at 4 °C and used on a weekly basis, results in an additional standard uncertainty of the analyte concentration value of 0.35% per month due to compositional stability. While the preparation procedure is the major contributor to the total measurement uncertainty, the uncertainties introduced by the stability measurements are another important contributor, and therefore, the measurement procedure to evaluate stability is important to minimize the total measurement uncertainty.     

Determination of ultratrace elements in natural waters by solid-phase extraction and atomic spectrometry methods

A study was carried out on the preconcentration of ultratrace amounts of cadmium, lead, manganese, copper and iron from high-salinity aqueous samples and determination by atomic spectrometry methods. Sample volume, amount of resin, loading flow rate, and elution volume were optimized in order to obtain the simultaneous preconcentration of all the analytes. Quantitative recoveries were obtained by using 200 mg of iminodiacetic resin with a loading flow rate of 2 mL min(-1), elution volume of 3 mL and sample volume of 50-450 mL. Only copper in seawater samples was not completely retained by the resin (60-70% recovery), due to unfavorable competition of iminodiacetic-active groups with organically bound metal.To quantify the metals in the eluates, two atomic spectrometry techniques were compared: electrothermal atomization atomic absorption spectrometry (ETAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) with simultaneous CCD detection system. Both techniques are suitable for sample analysis with detection limits of 1.0, 4.7, 3.3, 6.8, and 53 ng L(-1) using ETAAS and 12, 122, 3.4, 17, and 21 ng L(-1) using ICP-OES for Cd, Pb, Mn, Cu, and Fe, respectively. Relative standard deviations of the procedures ranged from 1.7 to 14% at the sub-microg L(-1) concentration level. The accuracy of both methods was verified by analyzing various certified reference materials (river water, estuarine water, coastal and off-shore seawater).     

恒电流电解-BCO分光光度法测定纯铜中铜含量不确定度的评定

对采用恒电流电解-BC0分光光度法测定纯铜中铜含量的不确定度进行了评定.对测量重复性、电解重量法、光度法等影响测量结果的不确定度分量进行了分析和量化.当纯铜中铜的质量分数为99.93%时,扩展不确定度为0.01%,k=2.     

Measurement uncertainty and its meaning in legal metrology of environmental chemistry and public health

 The need for reliability of measurements supporting legal decisions in environmental policy or medical diagnosis and treatment is well known and widely accepted. This prerequisite can be met only by ensuring that legal measurements are accurate and traceable to national or international standards. Consequently, an outline of the organizational structure of the Romanian National Institute of Metrology (INM) for ensuring uniformity, consistency and accuracy of all measurements including legal measurements performed in chemical laboratories is presented. Since reliable measurements can only be accomplished within an appropriate traceability chain, the experience of the INM in identification and evaluation of measurement uncertainty in legal activities concerning the environment and health is reviewed. Practical examples of measurement uncertainty evaluation in spectrophotometric determination of five analytes, commonly determined in environmental and clinical chemistry are described. The implications of measurement uncertainty for interpretation of regulatory compliance are discussed. Received: 3 January 1998 · Accepted: 9 June 1998     

Chemometric investigation of systematic error in the analysis of biological materials by flame and electrothermal atomic absorption spectrometry

Systematic errors observed when using flame atomic absorption spectrometry (FAAS) and electrothermal atomic spectrometry (ETAAS) for the analysis of biological solid materials (seafood products) were evaluated. The effect of the sample pre-treatment method (microwave-assisted acid digestion, ultrasound-assisted acid leaching and slurry sampling) as well as the number of times that a certain pre-treatment process is repeated, were two factors evaluated. They give information about the effect of the sample pre-treatment on the uncertainty in the analysis. In addition, the number of measurements (i.e., number of times that an acid digest, an acid leachate or aqueous slurry are analysed) and the calibration technique used (aqueous calibration method or standard addition technique) were other two variables taken into account. This last factor gives information about the effect of the calibration on the results, while the replicate measurements showed the repeatability. A fifth variable named as sample matrix tests the influence of the matrix sample on the systematic error through the use of different reference materials. This variable allows the study of the effect of the trace element concentrations on the uncertainty because the trace elements contents are different in each reference material. Experimental design and principal component analysis approaches were used as chemometric tools. It has been found that the use of the slurry sampling technique in ETAAS and FAAS and the determination of high element concentrations by ETAAS have led to poor precision.