Reference materials and certified reference materials for spectrometry in Romania

Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed.     

Reference materials and certified reference materials for spectrometry in Romania

Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed.     

An estimation of the measurement uncertainty for an optical emission spectrometric method

 A validation procedure based on the ISO/IEC 17025 standard was used to demonstrate the long-term stability of a calibration process and to assess the measurement uncertainty of a standard test method for optical emission vacuum spectrometric analysis of carbon and low-alloy steel (ASTM E 415–99a). The validation was used to provide documented evidence that the selected method fulfils the requirements and that the method is ”fit for purpose”. A test for drift was applied to determine statistically whether the analytical results vary systematically with time. The accuracy and traceability of the optimised method were tested by an analysis of closely matched matrix certified reference materials (CRMs). The measurement uncertainty estimations took account of the precision study, the bias and its uncertainty, and the qualification of uncertainties not considered in the overall performance studies. Received: 2 November 2002 Accepted: 2 January 2003 Acknowledgement The author expresses gratitude to Dr. Aleš Fajgelj for helpful discussions during the 3rd Central European Conference on Reference Materials and Measurements. 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 T. Drglin     

Twenty-five years of international collaboration in reference materials via ISO/REMCO

This paper looks back on a quarter century of history of the Council Committee on Reference Materials of the International Organization for Standardization – REMCO. It begins however with the period before its formation in 1976 to describe how the Committee came into being as a response to a growing need by the analytical community for the number and variety of reference materials (RMs) as well as a need for the assurance of the quality of RMs and ends with a view of REMCO activities in the near future. This is not intended as a detailed history but instead to describe the evolution of REMCO by identifying major activities and accomplishments of REMCO. Received: 21 January 2002 Accepted: 22 January 2002     

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.     

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.     

IMEP in support of the comparability of measurement results across the Romanian chemical metrology infrastructure

On the basis of quantitative chemical measurements many important decisions are made in support of legislation or in industrial processes or social aspects. For this reason it is important to improve the quality of chemical measurement results and thus make them comparable and acceptable everywhere. The measurement quality is important to enable an equivalent implementation of the European Union regulations and directives across an enlarged EU. In this context, the European Commission–Joint Research Centre–Institute for Reference Materials and Measurement (EC-JRC-IRMM) set up a programme to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries in the framework of EU enlargement. Several activities were initiated, such as training, fellowships, sponsoring of seminars, conferences and participation in interlaboratory comparisons. To disseminate measurement traceability, IRMM provides through its International Measurement Evaluation Programme (IMEP) an interlaboratory tool to enable the benchmarking of laboratory performance. IMEP emphasizes the metrological aspects of measurement results, such as traceability and measurement uncertainty. In this way it has become a publicly available European tool for MiC. The Romanian Bureau of Legal Metrology – National Institute of Metrology (BRML-INM) actively supports the participation of Romanian authorized and field laboratories in IMEP interlaboratory comparisons. This paper describes the interest of Romanian laboratories participating in this programme, the analytical and metrological problems that became relevant during these exercises and some actions for improvement. The results from Romanian laboratories participating in IMEP-12 (water), IMEP-16 (wine), IMEP-17 (human serum) and IMEP-20 (tuna fish) are presented. To conclude, the educational and training activities at national level organized jointly by the Romanian National Institute of Metrology (INM) and IRMM are also mentioned.     

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.     

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.     

Interlaboratory comparisons – demonstrating degree of equivalence

 The role of matrix reference materials in the process of demonstrating the degree of equivalence of measurement results obtained from intercomparisons is outlined, reviewing exemplary selected experience gained at BAM regarding the determination of organic contaminants in environmental matrices. The specific characteristics of reference materials employed in the process of demonstrating equivalence between laboratories in the course of proficiency testing as well as the development, comparison and validation of methods are elaborated. The demand is for series of appropriately characterised samples which are fit for the purpose and it is seen from representative examples that the utilisation of such tailor-made RM designed to tackle the specific need of an analytical problem dominates over certified matrix reference materials in this context. Concluding, the role of certified matrix reference materials in quality assurance is briefly looked at both from the user’s and providers’ points of view. Received: 9 September 2002 Accepted: 16 December 2002 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 R. Becker     

Outline for the revision of ISO Guide 35

The production 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 measurements, such as calibration, quality control and method validation, as well as for the assignment of values to other materials. Currently, ISO Guide 35 is in its third edition after it was revised in 2006. The Guide was developed to support best practices in the value assignment to specified properties of Certified Reference Materials (CRMs). This Guide gives general guidance and explains concepts to assist the understanding and development of valid methods to assign values to the properties of a reference material, including the evaluation of their associated measurement uncertainties, and the establishment of their metrological traceability. From the outcome of a systematic review of ISO Guide 35 among the members of ISO/REMCO, the ISO Committee on Reference Materials, it followed that there is a need for revising the current edition of ISO Guide 35. The mandate for the revision is focused on editorial updates to explain the concepts in more detail. It is not envisaged that major technical changes will be introduced. This paper explains the approach and rationale for the revision of ISO Guide 35 and invites comments from the users of the current edition of ISO Guide 35.     

The use of certified reference materials in the Romanian traceability scheme

 For ensuring the traceability and uniformity of measurement results, the main objectives of national metrology programmes in chemistry are to calibrate and verify measuring instruments, to evaluate the uncertainty of measurement results and to intercompare the analytical results, etc. The concept of traceability has developed recently in chemical measurements, thus, an attempt to implement the principles of metrological traceability especially by appropriateness calibration using composition certified reference materials (CRMs) is underlined. Interlaboratory comparisons are also a useful response to the need for comparable results. The paper presents some aspects and practices in the field of spectrometric measurement regarding the metrological quality of the traceability by calibrating the instruments using suitable and reliable CRMs. The uncertainty of results, as a measure of the reliability that can be placed on them, has been adequately described in different documents and, as a consequence, some examples of evaluating the measurement uncertainty are described. The relationship between uncertainty and traceability, as two fundamental concepts of metrology which are intimately linked, is underlined. Received: 12 November 1999 / Accepted: 10 December 1999     

Certified reference materials for inorganic and organic contaminants in environmental matrices

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.     

Metrological traceability in laboratory medicine

 The establishment of a reference examination system necessary for metrological traceability of the many types of sophisticated examination result in laboratory medicine is a daunting task, which has been made mandatory by the EU Directive on in vitro diagnostic medical devices and the requirements for accreditation. Following a definition of examinand and allowed examination uncertainty, a dedicated calibration hierarchy is established from stated reference through alternating reference examination procedures and calibrators providing a traceability chain from examination result to the reference, often a definition of a measurement unit. The various types of possible calibration hierarchy are outlined in EN ISO Standards. Recent efforts by national and international stakeholders to establish a global reference examination system have led to the creation of a Joint Committee on Traceability in Laboratory Medicine with the International Committee for Weights and Measures, International Bureau of Weights and Measures, International Federation of Clinical Chemistry and Laboratory Medicine, International Laboratory Accreditation Cooperation, and World Health Organization as the principal promoters. This structure will identify reference procedures, reference materials, and reference laboratories, and seek support for further prioritised and coordinated development of the system. Received: 1 August 2002 Accepted: 22 November 2002 Based on a lecture at an IUPAC Seminar, EC JRC Institute for Reference Materials and Measurements, Geel, BE, 2001–12–18 Correspondence to R. Dybkaer     

Quality assurance of qualitative analysis in the framework of the European project ’MEQUALAN’

 The European Commission has supported the G6MA-CT-2000–01012 project on ”Metrology of Qualitative Chemical Analysis” (MEQUALAN), which was developed during 2000–2002. The final result is a document produced by a group of scientists with expertise in different areas of chemical analysis, metrology and quality assurance. One important part of this document deals, therefore, with aspects involved in analytical quality assurance of qualitative analysis. This article shows the main conclusions reported in the document referring to the implementation of quality principles in qualitative analysis: traceability, reliability (uncertainty), validation, and internal/external quality control for qualitative methods. Received: 15 October 2002 Accepted: 20 October 2002 This paper is a summary of the Quality Assurance section included in the final report of the MEQUALAN project. The authors of this paper correspond to the members of the MEQUALAN Consortium. One of them (K.H.) does not fully agree with some parts of the text. Correspondence to A. Ríos     

A need for clearer terminology and guidance in the role of reference materials in method development and validation

 The fact that various definitions and terminology applied to measurements in analytical chemistry are not always consistent and straightforward, by not only answering the question ”what”, but also ”how”, leads to their various interpretations. This results in non-uniform implementation of very basic and essential metrological principles in chemistry. Such a diverse situation is not conducive to the endorsement of harmonised measurements all across the world, to serve as a tool for improving the quality of life in its broadest sense for all its citizens. The discussion in this paper is focused on problems associated with terminology and definitions of ’reference material’ and ’validation’. The role of reference materials in measurement processes for purposes other than calibration and validation principles in analytical chemistry are also discussed in this paper. Where possible, potential solutions are proposed, but more often, questions of essential importance are raised in order to initiate international discussion which will hopefully lead to equally understandable answers. Received: 2 November 2002 Accepted: 3 February 2003 Acknowledgements   The author is grateful to Aleš Fajgelj for his comprehensive comments on the topic described in this paper. Sincere thanks also to Philip Taylor, Ewa Bulska, Emilia Vassileva, Miloslav Suchanek and Margreet Lauwaars for their contribution during fruitful discussions on validation. Presented at the 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 N. Majcen     

Double molecular imprinting--a new sensor concept for improving selectivity in the detection of polycyclic aromatic hydrocarbons (PAHs) in water

It is now well recognised that the quality control (QC) of all types of analyses, including environmental analyses depends on the appropriate use of reference materials. One of the ways to check the accuracy of methods is based on the use of Certified Reference Materials (CRMs), whereas other types of (not certified) Reference Materials (RMs) are used for routine quality control (establishment of control charts) and interlaboratory testing (e.g. proficiency testing). The perception of these materials, in particular with respect to their production and use, differs widely according to various perspectives (e.g. RM producers, routine laboratories, researchers). This review discusses some critical aspects of RM use and production for the QC of environmental analyses and describes the new approach followed by the Measurements & Testing Generic Activity (European Commission) to tackle new research and production needs.     

The traceability scheme in chemical measurement

 Traceability is an essential property of a measurement result. However, it is recognized that the results of chemical measurements can be lacking in this property. In this paper we try to show how to understand and establish traceability in chemical measurement. The traceability connotation and the necessity of tracing back to SI units are described by means of comparability well-known. The roles and interrelationships of quality assurance, accreditation, calibration, reference material, analytical method, comparison and uncertainty in establishing traceability are explained with the aid of a block diagram. The paper also includes diagrams illustrating the Chinese situation and experience of establishing traceability for chemical measurement in China.     

Double molecular imprinting – a new sensor concept for improving selectivity in the detection of polycyclic aromatic hydrocarbons (PAHs) in water

It is now well recognised that the quality control (QC) of all types of analyses, including environmental analyses depends on the appropriate use of reference materials. One of the ways to check the accuracy of methods is based on the use of Certified Reference Materials (CRMs), whereas other types of (not certified) Reference Materials (RMs) are used for routine quality control (establishment of control charts) and interlaboratory testing (e.g. proficiency testing). The perception of these materials, in particular with respect to their production and use, differs widely according to various perspectives (e.g. RM producers, routine laboratories, researchers). This review discusses some critical aspects of RM use and production for the QC of environmental analyses and describes the new approach followed by the Measurements & Testing Generic Activity (European Commission) to tackle new research and production needs.     

The role of certified reference materials in ensuring the quality of spectrochemical measurements – the present status in Romania

 The objective of quality assurance programme for spectrochemical measurements is to reduce the measurement errors to accepted limits. Reference materials are being widely used as measurement standards in the fields of industrial production, environmental protection and clinical chemistry, and are playing an important role in ensuring the quality of measurement results. This paper presents some aspects, practices and examples of the activity of the Reference Materials Laboratory of the National Institute of Metrology, Bucharest, in the field of spectrochemical measurements. An attempt to describe the role and use of reliable certified reference materials to ensure the quality of spectrochemical measurements is presented. A short review of the locally available certified reference materials used in spectrochemical measurements is given. The use of reference materials data in estimating the measurement uncertainty is discussed. An interlaboratory comparison, recently organized in Romania, is also presented as a useful response to the need for quality assurance of spectrochemical results. Received: 20 March 1999 / Accepted: 25 February 2000