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1.
Nahar Singh VN Ojha Nijhuma Kayal Tarushee Ahuja Prabhat K Gupta 《Chemistry Central journal》2011,5(1):17
Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate
and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about
the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance
is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability
of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis.
The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the
main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various
potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of
Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling
by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples
so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties.
The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the
final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis,
weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that
during the period from 31st Jan. 2008 to 7th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m3 with 95% confidence level (k = 2). 相似文献
2.
In the EURACHEM/CITAC draft ”Quantifying uncertainty in analytical measurement” estimations of measurement uncertainty in
analytical results for linear calibration are given. In this work these estimations are compared, i.e. the uncertainty deduced
from repeated observations of the sample vs. the uncertainty deduced from the standard residual deviation of the regression.
As a result of this study it is shown that an uncertainty estimation based on repeated observations can give more realistic
values if the condition of variance homogeneity is not correctly fulfilled in the calibration range. The complete calculation
of measurement uncertainty including assessment of trueness is represented by an example concerning the determination of zinc
in sediment samples using ICP-atomic emission spectrometry.
Received: 9 February 2002 Accepted: 17 April 2002 相似文献
3.
Using Plackett-Burman experimental design the parameters of different ways of sampling (design and materials of the sampling
mold, conditions of solidification of samples) that influence on the homogeneity of copper-titanium-zinc alloy samples in
the production of titanium zinc were determined.
Based on these results, the homogeneity of samples taken with two different sampling molds was investigated with GD-OES technique
regarding alloyed elements (Cu and Ti) and impurities (Fe, Pb, Cd, Sn, Al) and was evaluated with analysis of variance (ANOVA).
For Cu, Ti and Fe an overall (combined) uncertainty for different sampling approaches were estimated and compared to the expanded
uncertainty evaluated without including the uncertainty due to sampling.
Received: 28 October 2002 Accepted: 2 January 2003
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 B. Kokliˇc 相似文献
4.
M. Thompson 《Accreditation and quality assurance》1998,3(3):117-121
Uncertainty of sampling is the contribution from sampling errors to the combined uncertainty associated with an analytical
measurement when the measurand is the concentration of the analyte in the 'target', the total bulk of material that the sample
is meant to represent. Of the errors considered to contribute to uncertainty, random errors of sampling, characterised by
precision, are much more accessible to investigation than those due to bias. Where an approximation to random sampling can
be achieved, realistic precisions can normally be estimated. In some instances reproducibility precision is significantly
greater than repeatability precision, and the contribution of between-sampler variations to sampling uncertainty must be acknowledged.
However, the collaborative trial of a sampling method is an expensive and difficult exercise to execute. A system of internal
quality control for routine sampling can be introduced. Fitness for purpose has been defined in terms of the required combined
uncertainty of sampling and analysis.
Received: 4 November 1997 · Accepted: 26 November 1997 相似文献
5.
《Spectrochimica Acta Part B: Atomic Spectroscopy》1996,51(2):229-244
The combined uncertainty in the analytical results of solid materials for two methods (ET-AAS, analysis after prior sample digestion and direct solid sampling) are derived by applying the Guide to the Expression of Uncertainty in Measurement from the International Standards Organization. For the analysis of solid materials, generally, three uncertainty components must be considered: (i) those in the calibration, (ii) those in the unknown sample measurement and (iii) those in the analytical quality control (AQC) process. The expanded uncertainty limits for the content of cadmium and lead from analytical data of biological samples are calculated with the derived statistical estimates. For both methods the expanded uncertainty intervals are generally of similar width, if all sources of uncertainty are included. The relative uncertainty limits for the determination of cadmium range from 6% to 10%, and for the determination of lead they range from 8% to 16%. However, the different uncertainty components contribute to different degrees. Though with the calibration based on reference solutions (digestion method) the respective contribution may be negligible (precision < 3%), the uncertainty from a calibration based directly on a certified reference material (CRM) (solid sampling) may contribute significantly (precision about 10%). In contrast to that, the required AQC measurement (if the calibration is based on reference solutions) contributes an additional uncertainty component, though for the CRM calibration the AQC is “built-in”. For both methods, the uncertainty in the certified content of the CRM, which is used for AQC, must be considered. The estimation of the uncertainty components is shown to be a suitable tool for the experimental design in order to obtain a small uncertainty in the analytical result. 相似文献
6.
Rod G. Gullberg 《Accreditation and quality assurance》2006,11(11):562-568
The evidentiary weight attributed to forensic breath alcohol results in drunk-driving prosecutions requires that measurement uncertainty be established and shown to be fit-for-purpose. The principal components contributing to breath alcohol measurement uncertainty include: (1) biological/sampling, (2) instrumental, (3) traceability and (4) the water/air partition coefficient for control standards. Employing duplicate breath results from over 92,000 subjects to estimate the biological/sampling component and assuming reasonable forensic values for the other components, the combined and expanded uncertainty is determined for a practical example. The combined uncertainty for an unbiased single determination breath alcohol measurement was: . Employing the expanded uncertainty (k = 2.58), the 99% confidence interval for a mean breath alcohol concentration of 0.0935 g/210 L was 0.0866 to 0.1004 g/210 L. The proportion of combined uncertainty associated with each component was determined to be: biological/sampling 73%, analytical 10%, traceability 13% and water/air partition coefficient 4%. These are forensically acceptable estimates and demonstrate fitness-for-purpose of breath alcohol measurement when employing appropriate elements of quality control. 相似文献
7.
In this work, the method of isotope dilution thermal ionization mass spectrometry able to trace to SI was developed to accurately measure trace amount of Cd, Pb, Zn and Cu in sediment, rice, wine, and human serum samples for interlaboratory comparisons. The research focuses on how to apply the primary method correctly, uncertainty evaluation of measurement results, and how to achieve the meaning of traceability to SI by using ID-TIMS. As a result, the measurement results of Cu and Zn in the human serum 1 and 2 with 0.94, 0.83 and 0.49% combined uncertainty, respectively, were accepted by EC-JRC-IRMM as the certified values of the serum samples. The measurement results of Cd and Pb in CCQM-K13 and CCQM-K24 with 3.96, 1.62 and 1.03% combined uncertainty, respectively, are within the degrees of the equivalence. These comparisons at the highest level of measurement are proof that traceability of chemical measurement can be achieved as the traceability chain of ID-TIMS established in this work was used. 相似文献
8.
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. 相似文献
9.
J. Vogl D. Liesegang M. Ostermann J. Diemer M. Berglund C. R. Quétel P. D. P. Taylor K. G. Heumann 《Accreditation and quality assurance》2000,5(8):314-324
The present paper describes the certification of the amount content of Cd, Cr and Pb in two different polyethylene materials
within the third phase of the Polyethylene Elemental Reference Material (PERM) project. The analytical procedure to establish
the reference values for Cd, Cr and Pb amount contents in these materials is based on isotope dilution mass spectrometry used
as a primary method of measurement. Cd and Pb were measured with inductively coupled plasma-mass spectrometry and Cr with
positive thermal ionization-mass spectrometry. The decomposition of the polymer matrix was carried out using a high pressure
asher. Reference values for amount content, traceable to the SI-system, have been obtained for these three elements in both
of the polyethylene samples of PERM. For each of the certified amount content values an uncertainty budget was calculated
using the method of propagation of uncertainties according to ISO and EURACHEM guidelines. The measurement procedures, as
well as the uncertainty calculations, are described for all three elements. In order to keep the whole certification process
as transparent as possible, the preparations of various reagents and materials as well as the sample treatment and blending
are described in detail. The mass spectrometry measurements and the data treatment are also explained carefully. The various
sources of uncertainty present in the procedure are displayed in the uncertainty budgets. The obtained combined uncertainties
for the amount content values were less than 2% relative (k=1) for all investigated elements. The amount contents were in
the μmol/kg range, corresponding to mg/kg levels.
Received: 21 October 1999 / Accepted: 29 January 2000 相似文献
10.
Schoenberger T 《Analytical and bioanalytical chemistry》2012,403(1):247-254
This paper discusses the technique for high-precision quantification using 1H-NMR to determine the purity of analytical standard samples. The procedure described is based on the use of internal reference
samples in an 1H NMR experiment in our laboratories. The sample preparation and all relevant NMR parameters were optimized for minimum uncertainty.
The validation of accuracy and precision was performed by comparing different certified reference materials. It was shown
that the high-precision measurement is applicable even for relatively small sample amounts down to 2.5 mg. The relative combined
uncertainty of measurement was found to be 0.15%. Two different approaches for uncertainty calculation were compared; a complete
uncertainty budget was calculated. 相似文献
11.
The measurement uncertainty of the result of chemical oxygen demand determination in wastewater was evaluated. The major
sources of uncertainty of the result of measurement were identified as the purity of reagents, volumetric operations, gravimetric
operations, bias, and the repeatability of the method. Identification and evaluation of uncertainty sources was followed by
combined uncertainty calculations. The combined uncertainty was compared to the experimentally determined variation and good
agreement was found, indicating that the major uncertainty sources had been identified. The results show that the major sources
of uncertainty arose from repeatability at high concentration level and volumetric steps at low concentration level, thus
revealing the target operations for reducing the measurement uncertainty of this determination.
Received: 5 August 2002 Accepted: 5 November 2002
Acknowledgements This research was supported by the Ministry of Education, Science and Sport of the Republic of Slovenia (Project Z2–3530).
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 A. Drolc 相似文献
12.
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. 相似文献
13.
Anna Maria Orani Petko Mandjukov 《International journal of environmental analytical chemistry》2017,97(8):710-729
Analytical procedure for the determination of As, Cd, Cu, Ni, Co and Cr in marine biota samples using solid sampling high-resolution continuum source atomic absorption spectrometry (HR CS AAS) and accelerated fast temperature programmes has been developed. Calibration technique based on the use of solid certified reference materials similar to the nature of the analysed sample and statistics of regression analysis were applied. A validation approach in line with the requirements of ISO 17025 standard and Eurachem guidelines was followed. Accordingly, blanks, selectivity, calibration, linearity, working range, trueness, repeatability and reproducibility, limits of detection and quantification and expanded uncertainty for all investigated elements were assessed. The major contributors to the combined uncertainty of the analyte mass fractions were found to be the homogeneity of the samples and the microbalance precision. Traceability to the SI system of units of the obtained with the proposed analytical procedure results was also demonstrated. The potential of the proposed analytical procedure based on solid sampling HR CS AAS technique was demonstrated by direct analysis of marine reference biota samples. Overall, the use of solid sampling HR CS AAS permits obtaining significant advantages for the determination of selected trace elements in marine biota samples, such as straightforward calibration, a high sample throughput, sufficient precision, a suitable limit of detection and reduced risk of analyte loss and contamination. 相似文献
14.
I. Papadakis Christophe R. Quétel Philip D. P. Taylor Paul De Bièvre 《Accreditation and quality assurance》2000,5(5):198-204
Metrological certification through a primary method of measurement and how it can be achieved is demonstrated in this paper,
using the example of re-certification of cadmium and lead content in a biological material, the Bureau Communataire de Reference,
reference material CRM-278R mussel tissue. The measurement method used was isotope dilution in combination with inductively
coupled plasma mass spectrometry. Microwave digestion was applied to the samples prior to the measurements. A detailed uncertainty
budget was evaluated according to the International Organisation of Standardisation, Guide to the Expression of Uncertainty
and EURACHEM Guide, resulting in an expanded uncertainty.
Received: 20 August 1999 / Accepted: 3 January 2000 相似文献
15.
Gyeonghee Nam Chu-Shik Kang Hun-Young So JongOh Choi 《Accreditation and quality assurance》2009,14(1):43-47
After a measurement, a measured value and a measurement uncertainty are produced as a measurement result. By a repeated measurement,
another measurement result is produced. Between the individual results of the two measurements, it is shown that there may
be a significant correlation. A correlation coefficient can be determined when a GUM-compliant uncertainty budget for a measurement
is available. Utilizing the correlations between the N individual results, an equation is derived to combine the N individual uncertainties of N measurements. Using the newly derived equation including the correlation coefficient, three measurement uncertainties of
three measurement results are combined as an example. The combined uncertainty is compared with the uncertainty of a measurement
which treats the three individual measurements as one process.
Papers published in this section do not necessarily reflect the opinion of the editors, the editorial board, or the publisher. 相似文献
16.
用ISO《测量不确定度表达指南》评估ICP-AES法测定不确定度 总被引:11,自引:0,他引:11
用国际通用的方法评估出ICP-AES法测定不确定度,考虑不确定度的主要来源包括仪器的精密度、标准物质标称值的不确定度以及制备溶液过程中引起的不确定度,推导出各种传播系数表达式,计算出各种不确定度分量并将其合成,并以测定钢铁中磷含量为例,提供了计算过程所需的各参数的采集和计算方法,所用的方法同样适用于以线性回归标准曲线法获得测定结果不确定度的评估。 相似文献
17.
M. H. Ramsey 《Accreditation and quality assurance》2002,7(7):274-280
Appropriate sampling, that includes the estimation of measurement uncertainty, is proposed in preference to representative
sampling without estimation of overall measurement quality. To fulfil this purpose the uncertainty estimate must include contribution
from all sources, including the primary sampling, sample preparation and chemical analysis. It must also include contributions
from systematic errors, such as sampling bias, rather than from random errors alone. Case studies are used to illustrate the
feasibility of this approach and to show its advantages for improved reliability of interpretation of the measurements. Measurements
with a high level of uncertainty (e.g. 50%) can be shown to be fit for some specified purposes using this approach. Once reliable
estimates of the uncertainty are available, then a probabilistic interpretation of results can be made. This allows financial
aspects to be considered in deciding upon what constitutes an acceptable level of uncertainty. In many practical situations
”representative” sampling is never fully achieved. This approach recognises this and instead, provides reliable estimates
of the uncertainty around the concentration values that imperfect appropriate sampling causes.
Received: 28 December 2001 Accepted: 25 April 2002 相似文献
18.
M. Buzoianu 《Accreditation and quality assurance》2000,5(6):231-237
In practice there are three aspects that need to be considered in order to achieve the required traceability according to
its definition: the 'stated reference', the 'unbroken chain of calibrations' and the "stated uncertainty". For a certain chemical
result, each of these aspects highly depends on the measurement uncertainty, both on its magnitude and how it was estimated.
Therefore, the paper describes the experience of the Romanian National Institute of Metrology in estimating measurement uncertainty
during the certification of reference materials (RMs), in metrological activities (calibration, pattern approval, periodical
verification, etc.), as well as during the analytical measurement process. Practical examples of estimation of measurement
uncertainty using RMs or certified reference materials are discussed for their applicability in spectrophotometric and turbidimetric
analysis. Use of the analysis of variance to obtain some additional information on the components of measurement uncertainty
and to identify the magnitude of individual random effects is described.
Received: 12 November 1999 / Accepted: 25 February 2000 相似文献
19.
Uncertainty estimates from routine sampling and analytical procedures can be assessed as being fit for purpose using the optimised uncertainty (OU) method. The OU method recommends an optimal level of uncertainty that should be reached in order to minimise the expected financial loss, given a misclassification of a batch as a result of the uncertainty. Sampling theory can used as a predictive tool when a change in sampling uncertainty is recommended by the OU method. The OU methodology has been applied iteratively for the first time using a case study of wholesale butter and the determination of five quality indicators (moisture, fat, solids-not-fat (SNF), peroxide value (PV) and free fatty acid (FFA)). The sampling uncertainty (s(samp)) was found to be sub-optimal for moisture and PV determination, for 3-fold composite samples. A revised sampling protocol was devised using Gy's sampling theory. It was predicted that an increase in sample mass would reduce the sampling uncertainty to the optimal level, resulting in a saving in expectation of loss of over pounds 2000 per 20 tonne batch, when compared to current methods. Application of the optimal protocol did not however, achieve the desired reduction in s(samp) due to limitations in sampling theory. The OU methodology proved to be a useful tool in identifying broad weaknesses within a routine protocol and assessing fitness for purpose. However, the successful routine application of sampling theory, as part of the optimisation process, requires substantial prior knowledge of the sampling target. 相似文献
20.
Tatjana Tomi? Nada Uzorinac Nasipak Sandra Babi? 《Accreditation and quality assurance》2012,17(3):291-300
In every measurement procedure, it is important to know the components of measurement uncertainty affecting the quality of measured result and reliability of quantified result. The procedure for recognizing measurement uncertainty is not universal but depends on the method and sample type. It has to be made according to good laboratory practice. This paper aims at showing the comparison of measurement uncertainty component estimations for three methods using the high-performance liquid chromatography techniques: determination of the type and content of aromatic hydrocarbons in diesel fuels and petroleum distillates by normal phase high-performance liquid chromatography, determination of nitrates in water samples by ion chromatography, and determination of molecular weights of polystyrene by size exclusion chromatography technique. Both similarity and differences were found during the measurement uncertainty component estimation, and conclusions about influences of certain components on the result uncertainty were made. 相似文献