Standards related to Reference Material

ISO Guide

The ISO Guide is designed basically for use within the ISO Committee. However, it is actually used as a guide for the member organizations. The ISO Guides concerning reference materials refer to Guide 30-35 at present. They were designated as the Japan Industrial Standard (JIS) , which is now being translated into Japanese.

*ISO Guide 30, Terms and definitions used in connection with reference materials
*ISO Guide 31, Reference materials --- Contents of certificates and labels
*ISO Guide 32, Calibration in analytical chemistry and use of certified reference materials
*ISO Guide 33, Uses of certified reference materials
*ISO Guide 34, General requirements for the competence of reference material producers
*ISO Guide 35, Reference materials --- General and statistical principles for certification

(1) ISO Guide 30 --- 1992 (Second edition)
"Terms and definitions used in connection with reference materials"

The 1981 first edition of Guide 30 was compiled jointly by REMCO, EEC, OIML, IUPAC, IFCC, and WHO. Dr. D.A. Lowe of WHO and Professor R. Neider of BAM wrote most parts of the guide. For the second edition, Dr. A.J. Head of IUPAC contributed greatly. The guide includes the following: table of contents, foreword, introduction, scope, terms related to materials, terms related to measurement and testing, terms related to certification and issuance of reference materials, and an annex (A: additional terms, B: bibliography). The section "Terms related to materials" provides a definition of reference materials, certified reference materials (CRM), primary standard, secondary standard, characterization, homogeneity, stability and sample. The section "Terms related to measurement and testing" provides definitions of certified value, uncertified value, consensus value, uncertainty of a certified value, precision, accuracy, accepted reference value, traceability, inter-laboratory test, and referring method. The section "Terms related to certification and issuance of reference materials" provides definitions of certification of reference materials, certificate of reference materials, certification report, certifying body and certified reference material producers. As for additional terms, definitions are provided for production batch, value of a quantity, true value of a quantity, systematic error, random error, level of confidence, repeatability, and reproducibility
According to this guide, the definition of reference material is: "Material or substance one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials." The definition of certified reference material is: "Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realisation of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence."

(2) ISO Guide 31 --- 2000
"Reference materials --- Contents of certificates and labels"

Mr. T.W. Steele of the National Institute for Metallurgy (SABS) wrote the first draft of this text. It is not possible to write detailed information on the label attached to the container of reference materials. The reference material report, on the other hand, generally contains quite detailed information. The certificate of reference materials is a document that contains summarized descriptions of all the information on the reference material. This guide shows all the items to be written in the table of contents of the certificate of reference materials. It contains descriptions on a total of 26 items: introduction, scope and field of application, certificate heading, name and address of the certifying organization, title of the document, status of the certificate, name of material, sample number (and batch number), date of certification, availability of other forms or sizes of the reference materials, source of the reference material (raw material), supplier and preparer of the reference material, descriptions on the reference material, intended use, stability, transportation and storage constructions, instructions for the correct use of the reference material, method of preparation of the reference material, state of homogeneity, certified property value and confidence limits, uncertified value, value obtained by individual testing and/or calibration laboratories or methods, estimator and confidence limits of the certified value, measurement techniques used for certification, names of the analyst, investigators and participating laboratories, legal notice, reference, signature or name of certifying officers, and an annex.

(3) ISO Guide 32 --- 1997
"Calibration in analytical chemistry and use of certified reference materials"

This guide contains general recommendations for those who are involved in quality assurance of testing and/or calibration laboratories, and assessments which are conducted in line with Guide 25. It was endorsed at the 18th meeting of REMCO in 1995. Dr. A. Marschal of LNE authored the text. This guide consists of an introduction (purpose of the guide and basic considerations), selection of calibration procedures in chemical analysis (Method 1, Method 2, Method 3, and other methods), calibration procedures (Method 1, Method 2, and Method 3), selection of CRMs, use of internal RMs, general remarks, and an annex. When the text was drafted, Method 1, Method 2, and Method 3 were called the calculable method, relative method and comparative method, respectively.

(4) ISO Guide 33 --- 2000
"Uses of certified reference materials"

In this guide, various terms concerning statistics are defined to express the uncertainty of the results of measurement or analysis in the form of confidence in the certified value.
It is composed of an introduction, Section 1: General (scope, definitions, statistical considerations, Section 2: Assessment of measurement process (the cases to be considered, requirements of limits, choices of CRM, carrying out the experiments, general remarks), Section 3: Defining and realizing conventional scales (general principles, the international practical temperature scale, the pH scale, the octane-number measuring scale, soluble solids content based on the refractive index method, unit of turbidity, hardness scale, and caking power of coal by Roga method), and an annex.
Section 2.4, "Carrying out the experiments" contains descriptions on checking the precision and trueness of a measurement by one laboratory (number of replicate measurements, assessment of precision and trueness), assessment of the measuring process by an inter-laboratory measurement program (number of laboratories and number of replicate measurements per laboratory), assessment of precision (within laboratory precision and inter-laboratory precision), and assessment of trueness (among other descriptions on the handling of statistical procedures). As an example, determination of total iron in iron ore is given.

(5) ISO Guide 34 --- 2009
"General requirements for the competence of reference material producers"

ISO Guide 34 specifies general requirements in accordance with which a reference material producer has to demonstrate that it operates.
The first edition of ISO Guide 34 set out specific guidelines on the interpretation of ISO/IEC Guide 25 and the international standards prepared by ISO/TC 176 in the context of reference materials production. The more general requirements of these international standards were omitted.Since the first edition of ISO Guide 34 was published in 1996, the assessment of the competence of reference material producers has gained considerable impetus.
The second edition of ISO Guide 34 published in 2009 set out all the general requirements in accordance with which a reference material producer has to demonstrate that it operates.
The second edition makes these requirements mandatory and in line with ISO/IEC 17025:2005 in view of its use for the assessment of the competence of reference material producers applying for accreditation.

(6) ISO Guide 35 --- 2006
"Reference materials --- General and statistical principles for certification"

ISO Guide 35 has been developed to support best practice in the production and certification of reference materials.
The purpose of this Guide is to assist in understanding and developing valid methods to assign values to properties of a reference material, including the evaluation of their associated uncertainty, and establish their metrological traceability. Most of the contents of this Guide can be applicable to the production of reference materials (RMs) other than CRMs.
Reference materials (RMs) that underwent all steps described in this Guide are usually accompanied by a certificate and called certified reference material (CRM).