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1.
Linsinger TP Gawlik BM Trapmann S Lamberty A Emons H 《Analytical and bioanalytical chemistry》2004,378(5):1168-1174
Over the years, the nature of CRMs has changed considerably. Recently, more and more CRMs have been certified in their "natural" form, that is processed as little as possible, with analytes at their natural concentration level. This and the trend towards certified properties other than the concentrations of clearly defined molecules/elements have made guaranteeing stability of CRMs and estimating a shelf life an even more important issue for reference material producers than it has been before. One way to meet this challenge is to take more care in processing, storage and dispatch of CRMs. At IRMM, approximately 20 % of the RMs are stored at –20 °C or below and about 10% require cooled transportation. In addition, increased efforts for assessing stability are needed. Shelf lives are estimated using addition of an uncertainty component based on real-temperature stability studies rather than by accelerated stability studies. These pre-certification efforts are complemented by a stability-monitoring program, which at IRMM includes 80 % of the non-nuclear and non-isotopic materials. Although the costs for these efforts are high in absolute terms, they are only a minor and indispensable contribution to the total costs of CRM production. 相似文献
2.
Homogeneity and stability of reference materials 总被引:6,自引:0,他引:6
T. P. J. Linsinger J. Pauwels A.M.H. van der Veen H. Schimmel A. Lamberty 《Accreditation and quality assurance》2001,6(1):20-25
Homogeneity and stability are two crucial characteristics of any certified reference material (CRM). Utmost care must be
taken during preparation to create materials as homogeneous and stable as possible. Degradation can generally be minimised
by reducing the water activity of the material to a level between 0.15 and 0.35. However, careful preparation by itself is
not enough. Positive demonstration of homogeneity and stability is required from the perspective of implementing uncertainty
calculus according to the Guide to the Expression of Uncertainty in Measurement (GUM). In many cases, homogeneity and stability studies fail to give sufficient quantitative information on homogeneity and
stability, mainly because of a lack of measurement repeatability and insufficient number of replicates. In this work, some
solutions to these problems and their implications are presented.
Received: 25 April 2000 / Accepted: 12 September 2000 相似文献
3.
Near infrared spectroscopy (NIRS) is an analytical technique that can be very useful for stability studies in particular because of its non destructive analytical capability. However, the spectral interpretation and treatment of this kind of multivariate data remains difficult without the use of chemometrics. In this article, a recent chemometrics method, analysis of variance - principal component analysis (ANOVA-PCA), was used for NIRS stability studies of sunflower and bread wheat external reference materials (ERM). It provided a practical tool for the study of the significance of various storage conditions according to an experimental design. Thus, the effect of the temperature, the nature of the atmosphere in the packaging and the storage duration were tested. ANOVA-PCA highlighted the influence of temperature and storage duration on the stability of the sunflower materials. For the bread wheat materials, the storage conditions did not have a significant effect on stability. Consequently, by applying ANOVA-PCA to near infrared spectral data, the sunflower materials were found to be considered stable for the time length of the study, i.e. 18 months stored in a cold room, while the bread wheat materials were found to be considered stable for the time length of the study, i.e. 12 months under the same conditions. 相似文献
4.
Vanderléa de Souza Janaína Marques Rodrigues Raquel Duarte da C. Cunha Bandeira Laura A. das Neves Valente Marcus Vinícius Barreto Sousa Viviane Fernandes da Silva Rafael Agostinho Lemos da Silva 《Accreditation and quality assurance》2008,13(12):717-721
This study simulated the transport and storage conditions of ethanol in water certified reference material (CRM) produced
by the Chemical Metrology Division of Inmetro—DQUIM with the purpose of estimating the measurement uncertainty related to
stability. The short-term stability study was performed on five different mass fractions (w) in terms of mg ethanol/g solution of the ethanol in water CRM. The nominal values are w = 0.5, 0.9, 1.1, 3.8 and 4.6 mg/g, at temperatures of 4 and 60 °C. On the other hand, the long-term stability study was developed
on four different mass fractions (nominal values): w = 0.5, 0.9, 1.1 and 4.6 mg/g, at a temperature of 20 °C. This paper will show the data from the long-term stability study
that took place over 52 weeks. The method used complies with ISO Guide 35, the BCR Guideline for Feasibility Studies and ISO
Guide 34. According to the statistical parameters used in both studies, the stability of ethanol in water CRM was confirmed
for all of the mass fractions studied. 相似文献
5.
Thomas P.J. Linsinger 《Trends in analytical chemistry : TRAC》2011,30(6):875-886
We present results of the systematic stability monitoring of certified reference materials (CRMs) for the mass fractions of metal species. Materials are tested regularly for the mass fractions of organotin, organomercury, organolead and organoarsenic species. Evaluation is based on ratios of results on samples stored under normal conditions and under even safer conditions (“reference stock”) to eliminate the effects of laboratory-to-laboratory variation. Of all results in this study, the results of organotin measurements show the highest relative standard deviations (up to 45%). Determination of methylmercury in sediment and fish is possible with much better precision (standard deviations of reproducibility below 5%). The accuracies of determinations of trimethyllead and organoarsenic species are slightly worse but still below 10%. The data confirmed stability since production (i.e. up to 13 years). However, shelf lives cannot be extended into the future based on these data, as uncertainty contributions for stability need to be included in the uncertainty budgets of CRMs to allow positive demonstration of the validity of certificates. Estimation of typical measurement uncertainties based on the data obtained from stability monitoring shows that potential degradation is negligible compared to uncertainties typical for this kind of measurement, demonstrating that the materials are still sufficiently reliable to demonstrate laboratory proficiency. 相似文献
6.
Four approaches for estimation of reference values and their respective uncertainties of characterisation were compared using
data from the recently finalised certified reference materials ERM-EC680k and ERM-EC681k, elements in plastics. Reference
values and uncertainties of characterisation were estimated as mean of laboratory means and their respective standard deviations,
using equal weights and the weighting procedure of Mandel–Paule. In addition, two approaches taking into consideration uncertainty
information reported by the participants, namely the consistency check and simulation procedure proposed by Cox for CCQM Key
comparisons and an approach suggested by Pauwels et al. (Accred Qual Assur 3:180–184, 2000) were used. No difference between
the equally-weighted and Mandel–Paule consensus means was observed and the reference value from the Cox approach was in all
cases within ±2 u
char of each consensus mean. Uncertainties varied between the three approaches. Uncertainties derived from equally-weighted mean
of means approach are on average 14% above uncertainties using the Mandel–Paule consensus mean, 36% above the uncertainties
estimated by Pauwels et al., and 54% above the uncertainties from the Cox approach. Robustness of the uncertainty estimation
against incorrect estimation of uncertainties was assessed. Assumption of a 50% uncertainty of the individual uncertainties
resulted in an uncertainty of 30% of the uncertainty of characterisation. Differences between the four approaches are negligible
for this dataset when combined with the uncertainty contribution from heterogeneity and stability as prescribed in ISO Guide
35.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
M. Buzoianu 《Accreditation and quality assurance》2003,8(3-4):124-129
A lot of effort is being made in Romania to meet the present main strategic goal – EU integration. Since the confidence in
measurements is of considerable importance in almost every field of activity, the National Institute of Metrology (INM) is
involved in improving its calibration and measurement capabilities to provide services in accordance with the latest European
Regulation.
Within this framework the assurance of the required traceability of all measurements plays a most important role. As reliable
analytical measurements depend largely upon reference materials and the assurance of the traceability of amount measurements
is still developing in Romania, a new approach regarding the function of Certified Reference Materials (CRMs) may be emphasized.
The experience of the INM as well as new developments in Romania in preparation and certification of Reference Materials (RMs)
are described. A short review of the locally available RMs and CRMs is given. Some aspects regarding the use of RMs and CRMs,
especially for calibration, are discussed for their applicability for analytical measurements.
Received: 31 October 2002 Accepted: 24 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 M. Buzoianu 相似文献
8.
Matthias Koch Almuth Liebich Tin Win Irene Nehls Arne Lund Kvernheim Oddvar Ringstad Frøydis Oreld 《Accreditation and quality assurance》2006,11(3):122-129
The 2-year international joint project HYCREF (Contract-No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogenous and stable water-, soil- and waste reference materials contaminated with mineral oil hydrocarbons and to test certify the mineral oil content by gas chromatographic methods. As mineral oil products are important sources for environmental contaminations, appropriate reference materials certified by using the new gas chromatographic methods (soil: ISO/FDIS 16703, waste: prEN 14039 and KW/04, water: ISO 9377-2) are highly needed. Additional to the HYCREF-results presented in part I–mineral contaminated soils–this second paper gives an overview of the feasibility study for the preparation and test certification of three waste reference materials (offshore marine sediment, building material and industrial waste). The following specifications, which had been defined in the project work plan, were reached successfully: uncertainty of the mineral oil content resulting from the certification exercise ≤5% and a between-bottle inhomogeneity of ≤3%. All three materials have been evaluated for long- and short term stability. They contain different levels and types of mineral oil and cover the full application range of ISO/FDIS 16703 and prEN 14039 (100–10,000 mg/kg). The expanded uncertainties U
cert of the three materials are about 6%. In this way, they are comparable to ERM®-CC015a (U
cert=7.1%, mineral oil in a river sediment) and are suited to close the present gap of commercially available CRM for mineral oil determination in waste. 相似文献
9.
Reference materials play a major role for the verification of the quality control of biological and chemical analysis. Due
to the poor availability of certified reference materials, external reference materials (ERM) are intensively developing in
complement and as a consequence of proficiency testing schemes (PTS). However, the use of any reference material must be time-limited,
whereas the assigned reference value may change with time and it is under the responsibility of the material producer to indicate
the date until this can be used for calibration purpose with some guarantee. This article compares different methods used
to determine the limiting date of stability (LDS) in food and food-related reference materials, using some specific analytes
(moisture, protein and oil contents) as stability-monitoring analytes. LDS is defined as the moment when the assigned values
of one or several analytes can no longer be guaranteed by the producer. For most of the ERMs used as examples (i.e., rapeseed,
bread wheat, durum wheat) the calculated periods of stability were longer than the present storage times used in BIPEA. However,
for sunflower, the rapid degradation of the monitoring analytes indicates a shorter time than forecast. 相似文献
10.
The preparation and certification of reference materials is a rapidly developing area. Many innovative reference materials
have limited homogeneity and stability, and, additionally, the uncertainty estimation of the property values must be brought
in agreement with the principles of the “Guide to the expression of uncertainty in measurement” (GUM). The results of the homogeneity and stability studies must be included to a certain extent in the uncertainty of the
property values of the reference material, in order to comply with these requirements. The basic theory needed to accomplish
this is essentially the theory of analysis of variance (ANOVA). As GUM also allows alternative evaluations other than Type
A evaluations, a reinterpretation of the theory of ANOVA is necessary to establish a model for the certification of reference
materials that is widely applicable. For this, analysis of variance can be used as a statistical technique to derive standard
uncertainties from homogeneity, stability and characterisation data.
Received: 10 May 2000 / Accepted: 29 July 2000 相似文献
11.
K. Heydorn 《Accreditation and quality assurance》1998,3(3):111-114
Stability tests are carried out on candidate reference materials in order to ascertain that the certification values continue
to be valid a reasonable time after completion of the certification analysis. These tests are also used for recommending storage
conditions, as well as the duration of storage before certification values need be rechecked. BCR (Community Bureau of Reference)
reference materials do not normally have an expiry date, but rely on stability monitoring throughout the lifetime of the certified
material. The 1997 version of the BCR Guidelines for the production and certification of reference materials does, however,
take into account the necessity of limiting the validity of a certification, when degradation of the material during storage
cannot be ignored. This paper discusses an example of significant degradation taking place between the time of completion
of the certification analysis and the issue of a formal certificate. Various options are presented together with an account
of their influence on the certified values and their uncertainties.
Received: 3 October 1997 · Accepted: 3 November 1997 相似文献
12.
Adriaan M. H. van der Veen Thomas P. J. Linsinger Andree Lamberty Jean Pauwels 《Accreditation and quality assurance》2001,6(6):257-263
To serve as a measurement standard, a (certified) reference material must be stable. For this purpose, the material should
undergo stability testing after it has been prepared. This paper looks at the statistical aspects of stability testing. Essentially,
these studies can be described with analysis of variance statistics, including variant regression analysis. The latter is
used in practice for both trend analysis and for the development of expressions for extrapolations. Extrapolation of stability
data is briefly touched upon, as far as the combined standard uncertainty of the reference material is concerned. There are
different options to validate the extrapolations made from initial stability studies, and some of them might influence the
uncertainty of the reference material and/or the shelf-life. The latter is the more commonly observed consequence of what
is called ’stability monitoring’.
Received: 6 October 2000 Accepted: 4 December 2000 相似文献
13.
Certified reference materials for inorganic and organic contaminants in environmental matrices 总被引:2,自引:0,他引:2
Ulberth F 《Analytical and bioanalytical chemistry》2006,386(4):1121-1136
Chemical measurements often constitute the basis for informed decision-making at different levels in society; sound decision-making
is possible only if the quality of the data used is uncompromised. To guarantee the reliability and comparability of analytical
data an intricate system of quality-assurance measures has to be put into effect in a laboratory. Reference materials and,
in particular, certified reference materials (CRMs) are essential for achieving traceability and comparability of measurement
results between laboratories and over time. As in any other domain of analytical chemistry, techniques used to monitor the
levels and fate of contaminants in the environment must be calibrated using appropriate calibration materials, and the methods
must be properly validated using fit-for-purpose matrix-matched CRMs, to ensure confidence in the data produced. A sufficiently
large number of matrix CRMs are available for analysis of most elements, and the group of chemicals known as persistent organic
pollutants, in environmental compartments and biota. The wide variety of analyte/level/matrix/matrix property combinations
available from several suppliers enables analysts to select CRMs which sufficiently match the properties of the samples they
analyse routinely. Materials value-assigned for the so-called emerging pollutants are scarce at the moment, though an objective
of current development programmes of CRM suppliers is to overcome this problem. 相似文献
14.
Five separate reference materials (RMs) were prepared from a mussel (Mytilus edulis) tissue containing domoic acid (DA) from scallop hepatopancreas (Pecten maximus). Homogenates were separately spiked with antibiotics, an antioxidant, or a combination of both. Control materials did not
contain any additives and were prepared from lightly cooked and autoclaved mussel tissues. Stability studies were run over
a 148-day period at three different temperature conditions: −20 °C, +4 °C and +40 °C. DA contents in all materials were characterised
by HPLC-UV. Homogeneities were demonstrated at the beginning of the study, with coefficients of variance of less than 4% (n = 9). DA was stable at −20 °C in all materials. The control materials showed significant degradation after two days at +40 °C,
and after eight days at +4 °C. Each of the materials containing additives demonstrated better stability during the initial
period of the study. In addition there was no significant degradation in any of the materials with additives stored at +4 °C
over the duration of the study. The material containing a combination of the antibiotics and the antioxidant displayed the
best stability of all the materials. There was no significant reduction in DA concentration at all temperature conditions
after eight days, and after 32 days the decrease at +40 °C was still <20 %. Following this, a DA laboratory reference material
(LRM) was prepared and, based on previous results, spiked with both the antioxidant and antibiotics. A short-term stability
study on this material gave similar results to the corresponding material in the additives study. This study shows that combined
use of the additives investigated in the preparation of a mussel tissue reference material for DA ensures analyte stability
for a period of up to eight days at temperatures of up to +40 °C, a condition that is particularly important when shipping
test materials globally.
Aliquots of individual feasibility materials used in the study 相似文献
15.
16.
K. Ishikawa N. Hanari Y. Shimizu T. Ihara T. Maeda A. Nomura T. Yarita K. Kato K. Chiba 《Accreditation and quality assurance》2008,13(7):397-408
Certified reference materials (CRMs) are playing an increasingly important role in environmental monitoring in Japan. The
National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) has been
developing CRMs of organic calibration solutions since 2003, and has issued several NMIJ CRMs. The development of these materials
was conducted at the NMIJ in cooperation with candidate material producers. The freezing-point depression method was principally
adopted for assessment of the purity of starting materials to give reliable certified values. Gas chromatography with flame
ionization detection (GC–FID) and/or high-performance liquid chromatography (HPLC), which are based on independent principles
and whose levels of accuracy are well evaluated, were applied in combination with other methods to avoid any possible analytical
bias. Purity assessment is outlined for two typical examples, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDD) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDT), which were used as starting materials for a CRM under development. Methods adopted for gravimetric preparation and
ampouling of solutions were qualified and optimized to reduce the uncertainties of certified values due to these factors.
Furthermore, a new experimental scheme for assessment of stability and preparation variation is proposed for the proper estimation
of uncertainties.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
17.
This article discusses the requirements for reference materials (RMs) for measuring the size of nanoparticles (NPs). Such RMs can be used for instrument calibration, statistical quality control or interlaboratory comparisons. They can come in the form of suspensions, powders or matrix-embedded materials [i.e. NPs integrated in a natural matrix (e.g., food, soil, or sludge)].At present, uncertainty about the most suitable form of material, the most relevant measurands and the most useful metrological-traceability statement inhibits the production of NP RMs. In addition, the lack of validated methods and qualified laboratories to produce NP RMs present formidable challenges.Metal, inorganic and organic NPs are available, but most of them are intended to be laboratory chemicals. With the exception of latex materials, certified RMs are not available, although some metrology institutes have started to develop such materials for colloidal gold and silica particles. 相似文献
18.
G. Price 《Accreditation and quality assurance》1996,1(2):57-66
National measurement systems are infrastructures to ensure, for each nation, a consistent and internationally recognised
basis for measurement. Such complex systems have historical, technical, legal, organisational and institutional aspects to
connect scientific metrology with practical measurements. Underlying any valid measurement is a chain of comparisons linking
the measurement to an accepted standard. The ways the links are forged and the etalons (measurement standards) to which they
connect are defining characteristics of all measurement systems. This is often referred to as traceability which aims at basing
measurements in common measurement units – a key issue for the integration of quantitative chemical analysis with the evolving
physical and engineering measurement systems. Adequate traceability and metrological control make possible new technical capabilities
and new levels of quality assurance and confidence by users in the accuracy and integrity of quantitative analytical results.
Traceability for chemical measurements is difficult to achieve and harder to demonstrate. The supply of appropriate etalons
is critical to the development of metrology systems for chemical analysis. An approach is suggested that involves the development
of networks of specialised reference laboratories able to make matrix-independent reference measurements on submitted samples,
which may then be used as reference materials by an originating laboratory using its practical measurement procedures.
Received: 31 July 1995 Accepted: 19 August 1995 相似文献
19.
Analyses of freshwater are routinely performed by a number of organisations to monitor the levels of major elements. In order to improve and control the quality of such determinations, the Community Bureau of Reference (BCR) has organised a certification campaign to produce two reference materials (CRM 398, low element content and CRM 399, high element content) certified for their contents of Al, Ca, Cl, Fe, Mg, Mn, K, Na, P and S. These materials were carefully prepared (addition of the elements mentioned in the form of ammonium salts or nitrates to silica free deionised water) and their homogeneity and long term stability were verified. This paper presents the certification work performed. 相似文献
20.
Ilona Šperlingová Ludmila Dabrowská Vladimír Stránský Jan Kučera Miloň Tichý 《Accreditation and quality assurance》2006,11(5):231-235
The candidate reference material (RM) was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to toluene. Homogeneity testing yielded no significant differences of urinary concentrations of o-cresol and phenol in 15 randomly selected units of RM. Stability testing showed no significant changes of concentrations of the above analytes over a period of 6 months. Property (pre-certified) values of phenol and o-cresol concentrations and their uncertainties (9.06±0.47 mg l−1 and 1.03±0.06 mg l−1, respectively) were estimated from results of a small-scale interlaboratory comparison in which two laboratories participated using four different analytical methods. 相似文献