Guidance on the contents of accompanying documentation for reference materials (RMs)

The use of reference materials (RMs) is a key activity for the improvement and maintenance of a worldwide coherent measurement system. As detailed in ISO Guide 33, RMs with different characteristics are used in measurement processes, for the purpose of precision control, bias assessment, calibration, assigning values to other materials, and maintaining conventional scales, to name a few. For the establishment of metrological traceability of measurement results to international scales or other measurement standards, proper use of certified reference materials (CRMs) is essential. From the perspective of a reference material producer, the documentation that is provided with an RM is the value-adding component of the material; for the user, the document is critical for the correct implementation and use of the RM in the measurement process. The ISO Committee on Reference Materials (ISO/REMCO) recognised the importance of the documentation that accompanies a reference material as early as 1981 when the first edition of ISO Guide 31 was published. The third edition of the Guide that was published recently considers the appropriate accompanying documentation for all types of reference materials, i.e. CRMs and non-certified RMs.     

The new ISO Guide 80: Guidance for the in-house preparation of quality control materials (QCMs)

Reference materials (RMs) are widely used in measurement laboratories for a variety of purposes, and it is important to recognise that the material most appropriate for a particular application should be used. Certified reference materials (CRMs) are used for method validation, the calibration of a measurement system and all other aspects of the evaluation of the measurement system where the trueness of the measurement result is required. For other aspects, such as quality control, precision studies, the checking of the variability between operators, where the results are compared relatively, any suitable reference material can be used. ISO/REMCO, the ISO Committee on Reference Materials, has prepared ISO Guide 80, a guidance document for the in-house preparation of quality control materials (QCMs). QCMs are mostly used to monitor the performance of laboratory methods that have already been validated over time to be able to detect change or when a method goes out of statistical control. QCMs are RMs and as such have to be sufficiently homogeneous and stable for the intended use. QCMs are usually prepared in-house by laboratory staff for in-house use only, and therefore, the requirements for “in-house” QCMs are less demanding than those for a CRM. For example, transport issues are not of concern. The quality assessment of QCMs should involve homogeneity and stability assessments, and a limited characterisation of the material to provide an indication of its relevant property values and their variation, prior to use.     

Accreditation of reference material producers: the example of IRMM's Reference Materials Unit

The potential approaches for third-party assessment of reference material producers are revisited and the activities of the Reference Materials (RM) Unit of the Institute for Reference Materials and Measurements (IRMM) to obtain accreditation to ISO Guide 34 and ISO 17025 are described. Accreditation was related to the Unit as all matrix RM activities of the institute are concentrated there. A management system was established that allows sufficient flexibility to be applicable to a wide range of RMs while being precise enough to ensure compliance with ISO Guides 30, 31 and especially 34 and 35. Accreditation was achieved in 2004 with independent scopes for testing and RM production and was confirmed and extended in 2005. The key aspects of the RM Unit's management system for RM production are presented. Presented at BERM-10, April 2006, Charleston, SC, USA     

The third edition of ISO Guide 34: what were the drivers for the revision and what is new?

After the International Laboratory Accreditation Cooperation (ILAC) had taken in 2004, the resolution to conduct accreditation of producers of reference materials according to ISO Guide 34 ‘General requirements for the competence of reference material producers’ in combination with ISO/IEC 17025 ‘General requirements for the competence of testing and calibration laboratories’, ISO/REMCO, the ISO Committee on Reference Materials, decided in 2005 to revise ISO Guide 34 to align it closer with ISO/IEC 17025 and to clarify certain issues for accreditors and producers seeking accreditation without adding new requirements. Moreover, the publication in 2007 of ISO/IEC Guide 99 ‘International vocabulary of metrology—Basic and general concepts and associated terms (VIM)’ triggered additional adaptations of the guide.     

Implementing the GUM in the certification of reference materials: the revision of ISO Guide 35

The availability of certified reference materials, certified in accordance to the GUM is an important tool for the proper estimation of measurement uncertainty in routine analysis. Many CRMs may suffer from incomplete or wrongly estimated uncertainties, mainly due to lack of guidance on how to implement the GUM in the production of CRMs. In particular the inclusion of the impact of inhomogeneity and instability in the uncertainty budget is often missing. The ongoing revision of ISO Guide 35 aims to fill this gap in providing guidance how (batch) inhomogeneity and instability can be translated into measurement uncertainty. The structure of the current ISO Guide 35 has been maintained as far as possible, but major parts underwent revision to become better aligned with GUM and ISO Guide 34 (2000). Received: 9 April 2001 Accepted: 22 October 2001     

Characterization of reference materials: proposal for a simplification of the options listed in ISO Guide 34

ISO Guide 34 and 35 list 4 approaches for the characterization of reference materials. We argue that an approach using “one method of demonstrable accuracy, performed by a network of competent laboratories” will provide method-specific values. Furthermore, as it is impossible to objectively decide whether a method is a reference method or not, the approach using “two or more independent reference methods in one or several laboratories” should be combined with the approach “two or more methods of demonstrable accuracy, performed by a network of competent laboratories.” We therefore propose to replace the four characterization approaches by three in the ongoing revision of ISO Guide 35.     

Production and evaluation of a reference material for moisture,ash, and total fat mass fractions,and titratable acidity in whole milk powder

Given the importance of reference materials (RM) in the structuring and maintenance of quality management systems for food analysis laboratories, RM were produced for the measurement of moisture, ash, total fat, and titratable acidity in whole milk powder. Two types of packaging and three storage temperatures were evaluated. The RM were considered homogeneous. The materials that were packaged in the pouches and those packaged in the amber glass bottles with screw caps (stored at room temperature) were not stable for moisture. Nevertheless, considering the four measurands, the amber glass bottles under refrigeration and freezing temperatures were the best packaging and storage conditions, respectively. Homogeneity and stability studies were carried out according to the ISO Guide 35, IUPAC harmonized protocol, and ISO 13528, considering the potential applicability of the produced materials as certified reference materials or even as RM for use in proficiency testing schemes. For homogeneity, despite the different criteria, there was agreement between the results. Considering the stability, the agreement depended on the evaluation of the regression assumptions, which is not required by the ISO Guide 35. The contribution of uncertainty associated with homogeneity was greater than that related to stability. The results indicated that the produced materials, i.e., the candidate certified RMs, were suitable for assessing trueness and could be submitted to further inter-laboratory characterization.     

New developments in the production and use of CRMs in Romania

 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     

对新版ISO导则34的理解

标准物质在实现测量结果溯源性以及不同时空测量结果的可比性方面具有广泛的应用。面对标准物质需求的不断增长和标准物质生产者数量的不断增加,新版ISO导则34：2009《标准物质生产者能力的通用要求》于2009年发布,以在促进该领域研究发展的同时,确保各种不同来源标准物质的质量。针对新版ISO导则34所涉及的相关名词术语以及一些重要原则进行了讨论,以促进对该导则的理解和在我国的推广应用。     

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 establishment of a quality evaluation system of reference materials

Reference materials have been applied widely to ensure the traceability, comparability and reliability of measurement results. To achieve this purpose, the quality of reference materials (RMs) themselves is surely an important aspect to be pay attention to. A quality evaluation system of RMs has been established through the project “The National Sharing Platform of Reference Materials” in China to give a reliable assessment on the quality of RMs from various sources including the accuracy and comparability of their property values, which is very useful to promote the appropriate selecting and using of RMs in China. Through the application of National Metrology Institute calibration and measurement capabilities on the basis of the international mutual recognition arrangement, it can also provide a powerful supplement to the current activities such as the accreditation of RM producers in the construction of a global harmonized quality control and assurance system of RMs.     

The Japanese traceability system and the role of uncertainty evaluation in measurement

 The new traceability system of measurement standards based on the Japanese Measurement Law has been established since November 1993. Some reference materials such as metal standard solutions, pH standard solutions and standard gas mixtures are included in the system together with relevant physical quantities. In this system, primary measurement standard instruments or primary reference materials are designated by the regulation for each quantity. For the practical dissemination of each quantity, accreditation of calibration bodies is recognized by the steering committee under the supervision of the government. In the course of assessment of a candidate calibration body, the concepts of ISO/IEC Guide 25 and ISO/IEC Guide 58 are effectively introduced. For the estimation of reliability, the concept of how to introduce the statistical approach is effectively considered. The method of uncertainty evaluation described in the ISO document entitled "Guide to the expression of uncertainty in measurement" is adopted.     

Recent developments in food-matrix Reference Materials at NIST

Since 1996, the National Institute of Standards and Technology (NIST) has developed several food-matrix Standard Reference Materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM 1846 Infant Formula, and SRM 2383 Baby Food Composite. Three additional materials--SRM 1946 Lake Superior Fish Tissue, SRM 2384 Baking Chocolate, and SRM 2385 Spinach--are in preparation. NIST also recently assigned values for proximate (fat, protein, etc.), individual fatty acid, and total dietary fiber concentrations in a number of existing SRMs and reference materials (RMs) that previously had values assigned for their elemental composition. NIST has used several modes for assignment of analyte concentrations in the food-matrix RMs, including the use of data provided by collaborating laboratories, alone and in combination with NIST data. The use of data provided by collaborating food industry and contract laboratories for the analysis of food-matrix RMs has enabled NIST to provide assigned values for many analytes that NIST does not have the resources or analytical expertise to measure.     

Comparability of reference values

Summary Harmonization of certified values in Reference Materials (RMs) can be carried out by applying nuclear analytical techniques to RMs of various matrix types and concentration levels. Although RMs generally should not be used as primary standards the cross evaluation of concentrations in RMs leads to better compatibility of reference values and thus to a greater agreement between analytical results from different laboratories using these RMs for instrument calibration and quality assurance.     

Accreditation of reference material producers

 The use of reference materials is the most pragmatic means by which the analyst can achieve comparability of data. Reference material producers therefore need to have adequate quality systems in place for ensuring the reliability of their materials. In order to provide guidance to both producers and assessors, ISO Guide 34 has recently been produced detailing the quality system requirements for the production of reference materials. CITAC, REMCO and ILAC are now collaborating in the revision of this guide to produce a free-standing document detailing the general requirements for the competence of reference material producers. This paper discusses some of the more important issues described in these documents. The possible formation of an international register containing details of a reference material producer's quality system status is also discussed.     

Value assignment of nutrient concentrations in five standard reference materials and six reference materials

A number of food-matrix reference materials (RMs) are available from the National Institute of Standards and Technology (NIST) and from Agriculture Canada through NIST. Most of these materials were originally value-assigned for their elemental composition (major, minor, and trace elements), but no additional nutritional information was provided. Two of the materials were certified for selected organic constituents. Ten of these materials (Standard Reference Material [SRM] 1,563 Cholesterol and Fat-Soluble Vitamins in Coconut Oil [Natural and Fortified], SRM 1,566b Oyster Tissue, SRM 1,570a Spinach Leaves, SRM 1,974a Organics in Mussel Tissue (Mytilus edulis), RM 8,415 Whole Egg Powder, RM 8,418 Wheat Gluten, RM 8,432 Corn Starch, RM 8,433 Corn Bran, RM 8,435 Whole Milk Powder, and RM 8,436 Durum Wheat Flour) were recently distributed by NIST to 4 laboratories with expertise in food analysis for the measurement of proximates (solids, fat, protein, etc.), calories, and total dietary fiber, as appropriate. SRM 1846 Infant Formula was distributed as a quality control sample for the proximates and for analysis for individual fatty acids. Two of the materials (Whole Egg Powder and Whole Milk Powder) were distributed in an earlier interlaboratory comparison exercise in which they were analyzed for several vitamins. Value assignment of analyte concentrations in these 11 SRMs and RMs, based on analyses by the collaborating laboratories, is described in this paper. These materials are intended primarily for validation of analytical methods for the measurement of nutrients in foods of similar composition (based on AOAC INTERNATIONAL's fat-protein-carbohydrate triangle). They may also be used as "primary control materials" in the value assignment of in-house control materials of similar composition. The addition of proximate information for 10 existing reference materials means that RMs are now available from NIST with assigned values for proximates in 6 of the 9 sectors of the AOAC triangle. Five of these materials have values assigned for total dietary fiber-the first such information provided for materials available from NIST.     

Trends in the certification of reference materials

The certification of reference materials is still a rapidly developing area. Mostly driven by demands from laboratories, new reference materials are produced, and even new categories of materials are developed, such as genetically modified organism materials or materials for qualitative analysis. Even in more classical areas, such as the certification of chemicals for purity, there are important new insights, in particular in modelling the measurements and the property values. Laboratories are asking increasingly for uncertainty budgets of reference materials that are compatible with the concepts of the Guide to the expression of uncertainty in measurement, thus putting stronger demands to improve not only the quality of the materials, but also of the science and technology behind a certification. Three important issues are highlighted to exemplify these trends: the further interpretation of homogeneity and stability data, the appreciation of asymmetry due to mathematical constraints (relevant for, e.g., purity and trace analysis), and the certification of reference materials for qualitative measurement.Presented at BERM-9—9th International Symposium on Biological and Environmental Reference Materials, 15–19June 2003, Berlin, Germany     

Reference materials and certified reference materials for water and food microbiology

Summary The concept of Certified Reference Materials (CRMs) for the verification of the accuracy of analytical methods and the traceability of the results to a CRM, is well accepted in chemistry. The use of Reference Materials (RMs) for intra-laboratory quality control schemes or for round-robin and proficiency testing is well established and follows from certain norms (ISO 9000 and EN 45000 series). For microbiology such concepts have not been fully defined and RMs are only rarely used. CRMs do not exist. To fill this gap the Commission of the European Community, through the BCR programme, has launched projects in collaboration with the RIVM (National Institute of Public Health and Environmental Protection) in Bilthoven (NL). Following fundamental considerations and feasibility studies, several intercomparisons have been held using selected laboratories working with food or water microbiology. Various microbiological strains have been subject of studies: Salmonella typhimurium, Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus for food, Escherichia coli, Enterococcus faecium, Enterobacter cloacae and Staphylococcus warneri for water. To produce materials for interlaboratory studies, a set of milk powders was prepared by spray-drying. Separate portions were contaminated with one of the strains mentioned. The materials were then encapsuled in gelatine. It has been demonstrated that if protected in milk powder matrices, bacteria maintain the ability to be revived, but do not multiply. The modes of evaluation of the results for homogeneity and stability differ from those commonly used in chemistry.     

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.     

Accreditation system for reference material producers and certified reference materials for iron and steel in Japan

  ISO 9000 series strictly requires traceability to national or international measurement standards. It is becoming more necessary to make clear the concept of traceability of measurement standards with respect to chemical composition and to accredit the reference material producers. In Japan, the accreditation system for reference material producers is considered to satisfy the requirement of ISO Guide 34, ISO 9000 series and ISO/IEC Guide 25, while the producer fulfills the concept of traceability of measurement standards. This paper describes the production of iron and steel reference materials in Japan relating to the international standardization of methods (written standards) and accreditation of reference material producers. Received: 11 October 1996 Accepted: 5 December 1996