Evaluation of the combined measurement uncertainty in isotope dilution by MC-ICP-MS

The combination of metrological weighing, the measurement of isotope amount ratios by a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) and the use of high-purity reference materials are the cornerstones to achieve improved results for the amount content of lead in wine by the reversed isotope dilution technique. Isotope dilution mass spectrometry (IDMS) and reversed IDMS have the potential to be a so-called primary method, with which close comparability and well-stated combined measurement uncertainties can be obtained.This work describes the detailed uncertainty budget determination using the ISO-GUM approach. The traces of lead in wine were separated from the matrix by ion exchange chromatography after HNO(3)/H(2)O(2) microwave digestion. The thallium isotope amount ratio ( n((205)Tl)/ n((203)Tl)) was used to correct for mass discrimination using an exponential model approach. The corrected lead isotope amount ratio n((206)Pb)/ n((208)Pb) for the isotopic standard SRM 981 measured in our laboratory was compared with ratio values considered to be the least uncertain. The result has been compared in a so-called pilot study "lead in wine" organised by the CCQM (Comité Consultatif pour la Quantité de Matière, BIPM, Paris; the highest measurement authority for analytical chemical measurements).The result for the lead amount content k(Pb) and the corresponding expanded uncertainty U given by our laboratory was:k(Pb)=1.329 x 10-10mol g-1 (amount content of lead in wine)U[k(Pb)]=1.0 x 10-12mol g-1 (expanded uncertainty U=kxuc, k=2)The uncertainty of the main influence parameter of the combined measurement uncertainty was determined to be the isotope amount ratio R(206,B) of the blend between the enriched spike and the sample.     

直读光谱法测量镁合金中锰含量的测量不确定度评定

根据GB/T13748.21-2009镁及镁合金化学分析方法(光电直读发射光谱分析方法测定元素含量)对镁合金中锰元素含量进行了分析,对锰含量测量的不确定度来源进行了分析,并对测量过程中产生的不确定度进行了评定.此外,指出了该方法影响锰元素测量不确定度的主要原因,以期为镁合金中锰元素含量的光谱分析提供参考.     

Dry mass determination: what role does it play in combined measurement uncertainty?

Elemental mass fractions are normally reported on a dry-mass basis. In addition, producers of reference material state their property values for dry masses and relate them to a defined dry mass determination method. This paper describes how biases and uncertainties in dry mass correction factors may affect values reported as ‘concentration per dry mass’. The influence of the use of different drying methods, accuracy of drying temperature, length of drying, environmental humidity, and the sample mass used for dry mass determination have been evaluated using two candidate International Atomic Energy Agency reference materials. Deviation from proposed drying methods was observed to lead to differences of up to 5% in dry mass correction factors. In addition, the heterogeneity of sample moisture as well as hygroscopic behaviour during weighing play an important role in the uncertainty estimation. Proposals are made regarding which sources of uncertainty arising from dry mass determination should be considered and included in the combined uncertainty of analytical results.     

Immunochemical determination of dioxins in sediment and serum samples

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are considered highly toxic contaminants and the environmental and biological monitoring of these compounds is of great concern. Immunoassays may be used as screening methods to satisfy the growing demand for rapid and low cost analysis. In this work, we describe the application of an immunoassay that uses 2,3,7-trichloro-8-methyldibenzo-p-dioxin (TMDD) as a surrogate standard for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to sediment and human serum samples. Sample extraction and preparation methods were developed with the aim to establish the simplest, cost-effective and efficient removal of the matrix interferences in the enzyme-linked immunosorbent assay (ELISA). The overall method for sediments is based on a hexane extraction; clean up by a multilayered silica gel column and an activated carbon column; an organic solvent exchange with DMSO–Triton X-100 and ELISA measurement. The gas chromatography–high resolution mass spectrometry (GC–HRMS) validation studies (n = 13) revealed that the method is suitable for the toxic equivalents (TEQ) screening of dioxin in sediments with a method detection limit of about 100 pg g⁻¹ dry sediment with a precision of 13–33% R.S.D. The analysis of a large number of samples originating from different sources would be required to establish more precisely the screening level, as well as the number of false positives and negatives of dioxin TEQ by the immunoassay for sediments. The immunoassay method for sediment analysis offers improvement in speed, sample throughput, and cost in comparison to GC–HRMS. Dioxins were determined in serum samples after a simple liquid–liquid extraction and solvent exchange into DMSO–Triton X-100 without further dilution. The current method (approximate method LOQ of 200 pg ml⁻¹ serum) is not sufficiently sensitive for the determination of dioxins in serum to measure acceptable exposure limit.     

X射线荧光法测定天然铀产品中铀含量的不确定度评定

利用X射线荧光法测定天然铀产品中铀含量,对测定结果的不确定度进行评定.建立了数学模型,分析了不确定度来源,计算合成标准不确定度和扩展不确定度.结果表明,标准曲线拟合、测量重复性、天平称量和标准样品量值对测定结果影响较大,当样品中铀的质量分数为84.736％时,其扩展不确定度U=0.078％(k=2).     

测定血清中Na 含量不确定度的评定

对血清中Na离子含量的测量不确定度进行评定。不确定度的来源主要包括Na离子标准工作液的配制过程、血清样品的定容消化制备、标准曲线拟合、钠离子各分量不确定度的合成等引入的不确定度计算出各分量的不确定度,通过合成得到测量结果的合成不确定度、扩展不确定度及测试结果的报告形式。     

The determination of substituted aromatic amines in water and sediment samples

Summary Certain substituted aromatic amines (anilines and benzidines) are known to possess high toxicological potential. They are classical environmental pollutants by virtue of their high degree of water solubility and the large amounts produced annually in the chemical industry for the synthesis of dyes, pesticides and pharmaceuticals.The present paper describes a method for the determination of at least thirty-one of these compounds at lower g/l or g/kg (ppb) ranges in water or sediment samples.Capillary column gas chromatography is employed with NFI- or MS-detection.Dedicated clean-up procedures are described for the substituted anilines and benzidines in aqueous and sedimentary matrices. In addition, quality assurance aspects of the individual single component identification by NFI- or MS-detection are discussed.

---

Bestimmung substituierter, aromatischer Amine in Wasser- und Sedimentproben

---

Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

A fast method for the determination of plutonium in soil and sediment samples

A so-called hour method for the determination of plutonium based on extraction chromatography is validated by its application to several certified soil and sediment samples from the International Atomic Energy Agency's Seibersdorf Laboratory. The results are in good agreement with the reference values. Chemical yields range between 47%–66%, with a mean value of (56±6)%. The possible use of this method for²⁴¹Pu determination is also demonstrated.     

Evaluation of measurement uncertainty in the determination of 210Pb and 210Po using beta counting and alpha spectrometry

 Measurement uncertainties in the determination of ²¹⁰Pb and ²¹⁰Po in Reference Material IAEA-300 (Baltic Sea Sediment) were evaluated. ²¹⁰Pb and ²¹⁰Po were separated from the matrix using an Sr resin column. The chemical yield of ²¹⁰Pb was determined gravimetrically in PbSO₄ form. Precipitation was followed by beta proportional counting after ²¹⁰Bi ingrowth. ²¹⁰Po was determined by alpha spectrometry after its spontaneous deposition on a Cu planchet. The major source of uncertainty was identified as the statistical counting uncertainty, which was also expected and is almost impossible to reduce without extension of the time required for an analysis. The expanded uncertainties were determined as 7.4% and 12.2% for ²¹⁰Pb and ²¹⁰Po, respectively. Received: 3 September 2002 Accepted: 3 December 2002 Acknowledgement This work was financially supported by Ministry of Education, Science and Sport, Republic of Slovenia (Project group PO-0106–0532). Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia Correspondence to P. Vreˇcek     

Evaluation of measurement uncertainties for the determination of total metal content in soils by atomic absorption spectrometry

In this work estimation of measurement uncertainties associated with the total metal content in soils was done by an intralaboratory approach based on method validation and quality control data, and using two certified reference materials (CRM). CRM and soil samples were analyzed following procedures based on the methods that are applied to silicate materials. All elements were determined by atomic absorption spectrometry following a quality assurance program previously established. Quality control actions were implemented in order to provide reliable data. The precision under within-laboratory reproducibility conditions was estimated from triplicate analysis. The trueness component was determined as recovery of the analyte from CRMs: soil sample, SO-2 and river clay sediment, LGC 6139. Combined measurement uncertainty was expressed in terms of precision and recovery uncertainties and the later further split on CRM replicate analysis and uncertainty of the certified value components. The results obtained are critically discussed on the basis of the different contributions. For the selection of the reference material, the CRM dependent terms are critically compared in order to fulfill specific requirements. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

光电直读发射光谱法测定镁合金中钙含量的测量不确定度评定

通过光电直读发射光谱法对镁合金中钙元素含量的测量不确定度进行了分析,来源包括直读光谱仪校准时示值误差引入的不确定度、标准样品引入的不确定度、测量重复性引起的不确定度、标准曲线校准时引入的不确定度,同时对各分量不确定度进行了评定.     

火焰原子吸收光谱法测定镁及镁合金中镉含量不确定度评定

采用火焰原子吸收光谱法测定镁及镁合金中镉含量,对测定结果不确定度进行评定.建立数学模型,分析不确定度来源,计算合成标准不确定度和扩展不确定度.当镁及镁合金中镉含量为0.00418％时,其扩展不确定度为0.00034％(k=2).火焰原子吸收光谱法测定镁及镁合金中镉含量不确定度主要来源于样品称量、样品消解溶液定容、标准工...     

Prompt gamma-ray neutron activation analysis for multi-element determination in sediment samples

A facility for the irradiation of internal targets has been installed at the research reactor FRG-of the GKSS Research Center. Thermal-neutron induced prompt gamma radiation was detected by pair spectrometer. With this experimental arrangement concentrations of the major and mino elements Na, Al, Si, K, Ca, Ti, Mn, Fe, Zn, Cl, and S, as well as of the trace constituents Cr Ni, Cu Cd, and Hg of samples from a sediment core of the Elbe River could be determined. The results indicate, that prompt gamma-ray neutron activation analysis (PGNAA) is a powerful instrumental tool for a complete characterization of the main sediment constituents and for the detection of the trace elements Cd and Hg which are of considerable ecological relevance.     

Evaluation of measurement uncertainty components associated with the results of complexometric determination of calcium in ceramic raw materials using EDTA

Calcium is an important constituent of mineral like calcite, dolomite, gypsum and bio-ceramic raw material like hydroxyapatite. Those are frequently used for the manufacture of cement, mortar, glass, synthetic ceramic bone supplement, dental enamel, etc. Determination of exact quantity of calcium in those materials is therefore very essential. The calcium content has been determined complexometrically in a ceramic raw material at pH 12, using di-sodium salt of EDTA. The major sources of uncertainty of the results of measurement are contributions from repeatability, standardization of EDTA, volume measurement by volumetric flask, burette, pipette and end point detection. Sources of uncertainty have been identified and combined by following the EURACHEM guidelines. The results show that the major sources of uncertainty arise from standardization, repeatability of the experiment and end point detection by burette. Cause–effect diagram has been drawn to explain the uncertainty budget.     

石墨炉原子吸收光谱法测定土壤中铅量的测量不确定度评定

通过石墨炉原子吸收光谱法对土壤中的铅量进行了测定,对影响测量结果的不确定度分量进行了量化的计算.从而得出影响铅量测量不确定度的主要因素是测量样品消解液中的铅的质量浓度引起的不确定度.     

Evaluation of the expanded measurement uncertainty in the determination of the net flux of nutrients and carbon atoms through the liver in ruminants

In in vivo metabolic studies, quantifying the flux of a nutrient and/or the carbon atoms through the liver implies the analytical determination of nutrient concentrations before and after crossing the liver and of blood or plasma flux. There is a measurement uncertainty (MU) associated with each input quantity, which may compromise accurate physiological interpretations of the results. The objective of this work was to calculate the expanded MU of net fluxes of nutrients and carbon atoms through the liver of ruminants and to identify the main components that affect MUs. To this end, all quantities (i.e., nutrient concentrations, para-aminohippuric acid concentrations, hematocrit, time of infusion, and others) that influenced the final results were identified and quantified. Their associated MUs were calculated with Type A or Type B approaches. An expanded MU model was developed by combining these two approaches. In general, the relative expanded MU of the net flux of nutrients calculated in plasma was lower than that in blood. For both plasma and blood fluxes, the main components that increased MUs were identified. The net hepatic flux of carbon atoms, for example, was estimated to be (63 ± 229) mmol min^?1. This high expanded MU was mainly a result of acetate concentration measurements in hepatic and portal veins. Priority strategies to reduce MUs, such as selecting an adequate matrix or using more accurate measurement methods, were identified.     

Rapid method for determination of protein content in cereals and oilseeds: validation, measurement uncertainty and comparison with the Kjeldahl method

The objective of this research was to test suitability of the Dumas combustion method to completely substitute the Kjeldahl method in routine laboratory determination of crude protein content in cereals and oilseeds. The validation of the method demonstrated that it is able to determine crude protein content in cereals and oilseeds in an efficient and accurate manner, with a detection limit w(N) = 0.006%, quantification limit w(N) = 0.019%, repeatability precision RSD _r = 0.41%, intra-laboratory reproducibility precision RSD _R = 0.74%, trueness, expressed in terms of bias b = 0.43%, and linear response between (2.36–19.2) mg N. Measurement uncertainty, expressed as relative expanded uncertainty (coverage factor k = 2, confidence level 95%), was calculated from validation data (U _rel = 2.24%). In order to examine the relationship between two methods, 15 cereal grain and oilseed samples were analyzed using Dumas and Kjeldahl procedure. The Kjeldahl procedure gave slightly lower w(N) values than the Dumas procedure: w _K(N) = 0.9905 w _D(N) = 0.0376 (R ²  = 0.9996). Relative standard deviations and results of homogeneity test obtained during analysis of complex cereal products (cereal breakfast and muesli bars) show that the Dumas combustion method may be less suitable for analysis of such samples compared to Kjeldahl method.     

Evaluation of measurement uncertainty for thermometers with calibration equations

The method recommended by Eurachem did not mention the effect of adequateness of calibration equations on the measurement uncertainty. In this work, the sources of measurement uncertainty for two types of thermometer were evaluated. Three calibration equations were adopted to compare its predictive performance. These sources of combined uncertainty include predicted values of calibration equation, nonlinearity and repeatability, reference source, and resolution source. The uncertainty analysis shows that the predicted uncertainly of calibration equations is the main source for two types of thermometer. No significant difference of the uncertainty was found between the classical method and the inverse method. However, the calculation procedure of the inverse method was simpler and easier than that of the classical method.     

Validation of the uncertainty evaluation for the determination of metals in solid samples by atomic spectrometry

 Every analytical result should be expressed with some indication of its quality. The uncertainty as defined by Eurachem ("parameter associated with the result of a measurement that characterises the dispersion of the values that could reasonably be attributed to the, . . ., quantity subjected to measurement") is a good tool to accomplish this goal in quantitative analysis. Eurachem has produced a guide to the estimation of the uncertainty attached to an analytical result. Indeed, the estimation of the total uncertainty by using uncertainty propagation laws is components-dependent. The estimation of some of those components is based on subjective criteria. The identification of the uncertainty sources and of their importance, for the same method, can vary from analyst to analyst. It is important to develop tools which will support each choice and approximation. In this work, the comparison of an estimated uncertainty with an experimentally assessed one, through a variance test, is performed. This approach is applied to the determination by atomic absorption of manganese in digested samples of lettuce leaves. The total uncertainty estimation is calculated assuming 100% digestion efficiency with negligible uncertainty. This assumption was tested. Received: 3 November 1997 · Accepted: 2 January 1998     

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.