The deplorable state of the description of the use of certified reference materials in the literature.

A detailed survey of 26 scientific journals showed that journal editors and a majority of authors of the re- c viewed papers seem unconcerned by the importance of correctly reporting their use of certified reference materials (CRMs). Only around 55% of the abstracts surveyed mention the use of CRMs described in these papers. This, however, is of key importance as the abstract of a paper is most widely available in electronic media. Many authors mentioned the use of CRMs in passing, often in incomplete form and without giving any details of the results obtained. Some are confused about the source of the reference material used, as they fail to report the type or the producer of CRMs applied. Others use materials that do not match the samples analyzed or do not see the need to use any CRM, despite the availability of suitable materials. Even in cases where correct data were given for type and producer of the CRMs, frequently the proper use and statistical evaluation are questionable. To improve this situation it is necessary that publishers should give recommendations where and how the use of CRMs should be described.     

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     

The use of certified reference materials in the verification of analytical data and methods

An experimental design is proposed for the verification of the accuracy and precision of an analytical method by its application to certified reference materials.     

Availability of reference materials: COMAR the database for certified reference materials

COMAR is the international database for certified reference materials. A new user-friendly web-based version, COMAR², has been developed by BAM and CONET Consulting AG which will be available in December 2002. The advantages of COMAR² are briefly explained.Presented at the International ILAC/IAF Conference on Accreditation in Global Trade, 23-25 September 2002, Berlin, Germany     

The use of inductively coupled plasma mass spectrometry in the production of environmental certified reference materials

The use of inductively coupled plasma mass spectrometry (ICP-MS) in the production of environmental certified reference materials by the National Research Council of Canada is reviewed. Particular emphasis is placed on the use of isotope dilution ICP-MS. Results for fresh and saline natural waters, fish tissues and sediments are presented to illustrate the impressive capabilities of this technique.     

人参皂苷Re标准样品的研制

以藏药诃子为原料,研制诃黎勒酸国家标准样品. 诃子经60%乙醇提取,大孔树脂富集,制备液相色谱技术得到诃黎勒酸标准品. 采用高效液相色谱（HPLC）、液相色谱-质谱（LC-MS）和薄层色谱（TLC）等手段进行纯度分析. 采用紫外光谱（UV）、红外光谱（IR）、高分辨质谱（MS）和核磁共振波谱（NMR）技术进行结构确认. 最后进行均匀性、稳定性和联合定值. 结果表明,诃黎勒酸样品均匀性良好,4 ℃储存,24个月内稳定. 联合定值确定诃黎勒酸纯度标准值为99.33%,符合国家标准品的要求. 研制出的诃黎勒酸（GSB 11-3724-2020）国家标准样品,可用于含量测定、检测方法评定、相关产品的检测与质量控制.     

Accreditation and the need for certified reference materials

The comparability of data from accredited laboratories is not always as good as customers would desire. A number of reasons for this fact are given. Clients of laboratories do not specify methodology, which may lead to the application of systematically different methods or to methodology with improper performance characteristics. Laboratories do not always validate methodology sufficiently which is, however, among others provoked by a lack of reference materials. It is argued that accreditation cannot enforce comparability on itself, but needs to be embedded in a measurement infrastructure. The quality systems which underly accreditation form a basic element. In addition, adequate methods, good laboratory performance studies and certified reference materials are required.     

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.     

NIES certified reference materials for arsenic speciation

 The National Institute for Environmental Studies (NIES) recently prepared two candidate certified reference materials (CRMs) for arsenicals to meet the growing demand for the quality assurance of arsenic speciation analysis. The NIES candidate CRM No. 14 Brown Alga was prepared from Hijiki seaweed for the certification of inorganic arsenic content, and No. 15 Scallop was prepared from adductor muscle of scallop for the certification of arsenobetaine content. The preparation of the candidate CRMs is briefly described. Cooperative analyses for total arsenic content of the candidate CRMs have been underway. The preliminary speciation analysis at NIES revealed difficulty in establishing suitable conditions for extracting arsenic species from the materials. Chromatograms of arsenic species by a high performance liquid chromatography-inductively coupled plasma mass spectrometric detection system are presented to provide information about arsenic species present in these candidate CRMs.     

Quantification of the expected shelf-life of certified reference materials

Stability testing and -monitoring are of the highest importance for the certification of reference materials. However, in general the results of these measurements are only assessed in a qualitative way, and no effort is made to quantify the period of certification or the shelf-life of the CRM. However, the revised ISO Guide 31 “Contents of Certificates, Certification Reports and Labels of Reference Materials” will most probably contain the explicite obligation to mention an expiry date “for all CRMs where instability has been demonstrated or is considered possible”. Therefore a method is proposed for quantifying the expected shelf-life on the basis of linear regression and determination of the intersection of the lower confidence limit of the certified value with the 95% lower confidence bound of the mean degradation curve.     

Quantification of the expected shelf-life of certified reference materials

Stability testing and -monitoring are of the highest importance for the certification of reference materials. However, in general the results of these measurements are only assessed in a qualitative way, and no effort is made to quantify the period of certification or the shelf-life of the CRM. However, the revised ISO Guide 31 “Contents of Certificates, Certification Reports and Labels of Reference Materials” will most probably contain the explicite obligation to mention an expiry date “for all CRMs where instability has been demonstrated or is considered possible”. Therefore a method is proposed for quantifying the expected shelf-life on the basis of linear regression and determination of the intersection of the lower confidence limit of the certified value with the 95% lower confidence bound of the mean degradation curve. Received: 18 September 1997 / Revised: 26 November 1997 / Accepted: 24 December 1997     

The present situation of Japanese certified reference materials registered in the COMAR database

 In the field of reference materials, COMAR (Code d'Indexation des Matériaux de Référence) is now internationally known as a reliable directory. In order to improve the quality of COMAR, a document which covers general requirements for the registration of reference material has recently been adopted by the Japanese coding centre, NITE. This paper describes the general requirements for reference materials and the current status of the COMAR database coded by the National Institute of Technology and Evaluation (NITE), Japan. The concept of the requirements is fundamentally based on the ISO Guides 30, 31, 33, 34 and 35. Certifications of reference materials are divided into the following three categories in the newly adopted document. 1. Certifications based on the results of interlaboratory comparisons 2. Certifications in accordance with the Measurement Law 3. Certifications in accordance with the measurement results of national institutions An example of an uncertainty evaluation is also presented in the paper. Received: 14 October 1996 Accepted: 3 December 1996     

The determination of the uncertainty of reference materials certified by laboratory intercomparison

A pragmatic method is proposed for the implementation of the Guide to the expression of uncertainty in measurement in the certification of reference materials by laboratory intercomparison. It is based on the establishment of a full uncertainty budget for each laboratory result and the estimation of the impact of various laboratory standard uncertainties and of between-units variability on the certified reference material (CRM) uncertainty.     

Non-destructive determination of zinc in biological certified reference materials

Non-destructive neutron activation analysis was employed to determine zinc in ten biological standard reference materials from the National Bureau of Standards and the National Research Council of Canada. The use of a 4 h. irradiation at a medium neutron flux allows excellent accuracies, precision and sensitivities to be attained for all the samples analyzed. It is suggested that neutron activation analysis be one of the benchmark methods for the determination of zinc in biological reference materials for concentrations as low as the one part per million level.     

Are certified reference materials a victim of quality systems? The need for working matrix-certified reference materials

The use of natural matrix-certified reference materials by commercial environmental laboratories is increasing rapidly. These materials are now an essential component of the quality systems of most commercial environmental laboratories. The use is increasing faster than existing producers, principally government agencies, can meet. The use of data from well established laboratory proficiency schemes is shown to be one alternative way of producing natural matrix-certified reference materials designed for use as day-to-day within-batch control materials.