Production Of Reference Materials Research Articles

Certified Reference Materials for the Characterisation of Multifunctional Materials

Multifunctional materials are created by intimately integrating different materials. The assessment of the local properties and composition of the different components of such a multifunctional material necessarily relies on techniques with sufficient spatial resolution. The increased use of these microanalysis or microprobe techniques has created a demand for appropriate quality assurance tools, such as reference materials. In this paper a number of issues related to the certification of reference materials for multifunctional materials are discussed. Examples of reference materials are shown to illustrate the particular challenges the reference material producer is faced with such as micro-homogeneity, minimum sample intake and stability.

Certification of Charpy V-Notch Reference Test Pieces at IRMM

Abstract The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC) of the European Commission (EC) is one of the reference materials producers which certifies reference test pieces for the indirect verification of Charpy pendulum impact machines. The certification approach taken at IRMM consists of two main steps. In a first step, a Master Batch of reference test pieces is certified for each of a number of chosen nominal energy levels (currently 30 J, 60 J, 80 J, 120 J, and 160 J). The certified absorbed energy value of these Master Batches is determined in an international round-robin. In the second step of the certification process, the Master Batch test pieces are used to determine the certified value of Secondary Batches of reference test pieces of the same nominal energy. This is achieved by comparing samples of Master and Secondary Batch under repeatability conditions. In this paper, this Master Batch — Secondary Batch approach is critically assessed in terms of traceability and uncertainty of the certified absorbed energy. It is shown that the produced reference test pieces are fit-for-purpose: they meet the requirements of their intended use (indirect verification).

A technical review of the feasibility of producing certified reference materials for the measurement of gaseous pollutants in ambient air

Abstract Within the frame of the EU sponsored project ‘Cermatair’ (Certified Reference Materials for the Measurement of Gaseous Pollutants in Ambient Air, contract G6RD-CT-2001-00517) the feasibility of preparing and certifying reference materials for the measurement of sulphur dioxide, nitrogen dioxide, carbon monoxide and benzene in ambient air was studied. The project focused on measurements at concentration levels corresponding to limit values given in EU Ambient Air Quality Directives and covered reference materials for the reference methods specified in these Directives and for alternative methods based on diffusive sampling. State-of-the-art technologies for the production and certification of the reference materials were identified through literature surveys. Limited batches of reference materials were prepared and, wherever appropriate, tested for homogeneity. The reference materials were subsequently tested in small-scale external verifications, performed by 2–4 laboratories other than the preparation laboratory, aimed at identifying possible discrepancies between concentration values from the preparation processes and experimental values. The results of these verifications revealed possible mechanisms of certification (based on preparation or measurements). The remaining materials were subjected to a one-year stability study.

First results of GEN-AU: Cloning of Deoxynivalenol- and Zearalenone-inactivating UDP-glucosyltransferase genes fromArabidopsis thaliana and expression in yeast for production of mycotoxin-glucosides

First results of the GEN-AU pilot project "Fusarium virulence and plant resistance mechanisms" are reported. Employing genetically engineered yeast strains we have been able to clone genes from the model plantArabidopsis thaliana encoding UDP-glucosyltransferases which can inactivate deoxynivalenol (DON) and zearalenone (ZON). The structure of the metabolites produced by the transformed yeast strains were determined by LC-MS/MS as DON-3O-glucoside and ZON-4O-glucoside, respectively. ZON and derivatives added to glucosyltransferase expressing yeast cultures are converted into the corresponding glucosides in very high yield, opening an efficient way to produce reference materials for these masked mycotoxins.

Polymer Reference Materials: Round-Robin Tests for the Determination of Molar Masses

This article reports round-robin tests dealing with static light scattering (LS), size exclusion chromatography (SEC), and viscometry measurements of 10 reference materials of various polymer classes: poly(styrene)s (PS), poly(methyl methacrylate)s (PMMA), poly(ethylene oxide)s (PEO), and poly(lactide)s (PLA). In the certificates, molar masses and intrinsic viscosities as well as their uncertainties are specified. Additional values from nuclear magnetic resonance (NMR), infrared spectroscopy (IR), differential scanning calorimetry (DSC), melt flow index (MFR), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), which were determined exclusively in BAM laboratories are given, as well. These results represent the base for the BAM certification work of creating polymer reference materials according to the BAM Guidelines for the Production and Certification of BAM Reference Materials, a version of the European guidelines (BCR/01/97). These samples are available for third-party user.

Accreditation of reference material producers: an update

Accreditation of reference material producers: an update

Possibilities of Production of New Reference Material ? Preparation of Gaseous Standard Mixtures Using Thermal Decomposition of Immobilized Compounds ? the Effect of Selected Parameters on the Amount of Released Analyte

The paper presents the results of research on a novel type of matrix-free reference materials for volatile organic compounds based upon thermal decomposition of appropriate immobilized compounds. The effect of parameters such as the kind of support (silica gel, porous glass, glass fiber) and the method of chemical modification of the support surface on the amount of chloromethane released as the analyte has been investigated. It was demonstrated that the amount of chloromethane released during thermal decomposition of immobilized compounds formed on the surface of silica gel and porous glass was larger when trimethylamine rather than N-morpholine was used for the preparation of immobilized compound. Reproducibility of the chemical modification procedure using silica gel and the stability of support with the immobilized compound were also examined. The full uncertainty budget of determination of liberated amount of chloromethane has been calculated.

Certified Reference Materials for Micro-Analysis of Carbon and Nitrogen

Quantitative analysis by electron probe micro analysis (EPMA) is usually carried out by reference to materials of known composition (standards) but because of the low X-ray yield arising from electron bombardment of low atomic number elements there is a particular problem when analysing these elements. This paper addresses the problem by describing briefly the production and certification of reference materials for two elements, carbon and nitrogen. Cementite (Fe3C), a line compound, was chosen as a suitable material for carbon and γ′-Fe4N for nitrogen. The compounds were produced by, respectively, carburising or nitriding pure iron under carefully controlled conditions. Particular emphasis is placed on a homogeneity study, background correction methods and methodology validation using these reference materials. A linear relationship was established between the certified content of the material and zero. Certified values (6.69±k 0.13 wt% C and 5.77±k 0.094 wt% N) were assigned for the composition, where k is the coverage factor.

Reference material requirements for laboratories and the role of accreditation bodies

It is now over two years since ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories was published. The standard places increased emphasis on the demonstration of traceability of measurements made by laboratories. In the areas of chemical and biological metrology, the introduction of this standard has brought new challenges for laboratories to grapple with. This paper will examine the requirements regarding traceability for chemical and biological measurements, with specific reference to the use of reference materials by laboratories. This will be explored from the perspective of both accreditation bodies and a laboratory which is both a user and producer of certified reference materials. Moreover, the paper will describe mechanisms that are being used to improve the use of reference materials by accredited laboratories and hence the traceability of measurements. Finally the role of accreditation programs for reference material producers in assisting with this aspect will be examined.

Teaching reference material preparation: the PHARE-country experience

The paper presents an overview about the outcome of two hands-on courses on environmental reference material production organised by the European Commission’s Environment Institute within the context of its PHARE-AQUACON activities. Two plant reference materials, i.e. TP-28 (black tea) and TP-29 (mallow) were prepared and characterised by the course participants. Data on homogeneity and information values about the contents of inorganic and organic pollutants are presented. Furthermore, information about the AQUACON-Project are given, too.

Improvements in efficiency of production and traceability for certification of reference materials

Issues of current interest to certified reference material producers are addressed. Alternative strategies for certification of matrix reference materials are discussed and the benefits of adopting a flexible, cost-effective approach are described. The difficulty of undertaking homogeneity testing where certification is to be carried out with definitive techniques capable of providing very small measurement uncertainty is discussed. Methodology is described which combines conventional screening of the candidate material for homogeneity with an additional, precise assessment of homogeneity based on isotope dilution mass spectrometry measurements. A systematic procedure for evaluating the commutability (horizontal traceability or scope) of matrix reference materials has been evaluated and shows that in some circumstances matrix effects may be less pervasive than is generally believed. This offers the possibility, especially for trace analysis applications, of more efficient use of existing reference materials without compromising measurement reliability. Vertical traceability of matrix reference material data is of growing interest but is difficult to achieve with present interlaboratory certification exercises. A modification is described which attempts to address this issue. It also offers the possibility of improved identification of outliers and reduced variation of data between the participating laboratories.

Emerging needs for sustained production of laboratory reference materials

Many different analytes are determined on a daily basis in many different matrices and the quality control (QC) for these determinations requires the use of reference materials (RMs), not only certified RMs (CRMs) but also laboratory RMs (LRMs) for routine purposes (e.g. control charting). In some cases, such materials are not available and the possibility of producing them in-house has to be considered. This article provides two examples showing that LRMs can be prepared by following a systematic approach without a very complex infrastructure: fly ash from cement manufacture; and, contaminated estuarine sediment.

Preservation of sensitive CRMs and monitoring their stability at IRMM.

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 degrees 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.

Implementation of ISO Guide 34: Accreditation for reference material production

The National Analytical Reference Laboratory of the Australian Government Analytical Laboratories was initially accredited to ILAC Guide G 12:2000 in January 2000 and is currently accredited to ISO Guide 34 (2000) for the production of a range of pure organic substance reference materials. This paper discusses the practical challenges and rewards of developing and implementing a quality system for reference material production and discusses some of the barriers, and potential solutions, to more general implementation of third-party accreditation.

Certification of reference materials and accreditation of reference material producers: Questionable terminology leads to confusion

In the view of the Deutscher Kalibrierdienst (DKD) , a certifying body for reference materials can be considered to be a calibration laboratory. Therefore, accreditation of calibration laboratories in accordance with ISO/IEC 17025 is the most appropriate way to establish confidence in certificates for reference materials. If necessary, the criteria of ISO/IEC 17025 can be tailored to specific cases. There is no need to provide any new kind of reference-material specific accreditation. However, in view of the variety of reference materials and the practice existing in other countries, accreditation of testing laboratories and product certification bodies may optionally be acceptable as long as the same stringent principles with respect to traceability and measurement uncertainty are applied. Such accreditations but not accreditations of reference material producers (ISO Guide 34) are also covered by existing international mutual recognition arrangements (MRA).

Stand alone accreditation of RM producers: arguments against it

Accreditation has a special responsibility in the European conformity assessment system. Before starting a new activity like stand alone accreditation of reference material producers, the consequences for the market place should be considered.

Preparation, homogeneity and stability studies of a candidate LRM for Se speciation.

A laboratory reference material (LRM) was prepared from Brazil nuts (Bertholletia excelsa) for quality control (QC) purposes of selenium speciation. The preparation of this LRM led through the usual operation steps applied during routine reference material production from biota samples-preparation of the raw material, homogenisation, storage design, checking of homogeneity, microbiological status and possible irradiation effects, and monitoring the species stability vs time at different storage temperatures. The selenium speciation studies to check species stability were carried out on a HPLC-UV-HG-AFS measurement set-up. Special attention was paid to the correct identification of selenium species by applying independent HPLC separation techniques (ion-pairing and anion-exchange chromatography). The concentration of selenomethionine (SeMet) and total Se content were quantified (79.9 microg g(-1) (calculated as Se) and 82.9 microg g(-1), respectively). The homogeneity and stability of this candidate reference material passed the relevant tests recommended by Bureau Communautaire de Référence (BCR).

Accreditation of reference material producers: Let's get it right!

The accreditation of testing and calibration laboratories to ISO/IEC 17025 is increasingly calling for the accreditation of reference material (RM) producers. Two international guides, ISO Guide 34 (2000) "General requirements for the competence of reference material producers" issued by the ISO Committee on Reference Materials and ILAC-G 12 "Guidelines for the requirements for the competence of reference material producers" issued by the International Laboratory Accreditation Cooperation (ILAC), are already in use for this purpose. Recently however initiatives have been launched to accredit RM producers to ISO 17025 as calibration laboratories and it has been suggested that a combination of ISO/IEC 17025 "General requirements for the competence of testing and calibration laboratories" and ISO Guide 34 may be the best option. This publication is an expression of the position of the ISO Committee on Reference Materials (ISO/REMCO) on the standards and guides currently in use in the accreditation of RM producers. The paper discusses the advantages and disadvantages of these standards and guides from the perspective of benefit to RM producers and RM users. In conclusion, the use of ISO Guide 34 alone or in combination with ILAC-G 12 is the preferred system for the accreditation of RM producers. Therefore ISO/REMCO strongly encourages all accreditation bodies to adopt ISO Guide 34.

The accreditation of reference material producers ? EUROLAB's position

A third-party assessment of reference materials (RMs) and their production is not of the highest priority for RM users. But if RM producers do want a third-party involvement this should be realised within the frame of existing conformity assessment schemes. Nevertheless, the right and responsibility of the laboratories to select the most appropriate RMs for their tasks must not be restricted by accreditation bodies or other interested parties.

Accreditation of reference material producers or certification of reference materials?

Accreditation of reference material producers or certification of reference materials?