Scientific and methodical Service of Reference Materials (NSC “Institute of Metrology”) has developed by the method of translation the DSTU-N ISO Guide 35:2018 (ISO Guide 35:2017, IDT) Reference materials. Recommendations on characterization and evaluation of homogeneity and stability.

The concept of reference material (eng. reference material - material of reference) is the basis of the international system of reflection of features that characterize the particularities of the investigated material objects, as a mean of reproduction, storage and transfer of qualitative and quantitative characteristics of the properties of these objects with the creation of an unbroken chain of transfer of SI units and nominal (qualitative) properties. The term "reference material" covers a wide range of properties carriers, which are defined in the description or performance of measurements and other research of the properties of material objects. Today, to describe the properties of material objects, there are used the concepts that go beyond the usual values - from the usual physical quantities to the concepts related to the measurements in chemistry, biochemistry, molecular biology, performance of forensic examinations, up to nominal quantities (values of such nominal properties, such as the scale of colors, the classification of species (taxa) in biology, the classification of diseases in medicine, the sequence of amino acids in polypeptides and DNA nucleotides, the taxa of HIV-antibodies, hepatitis A virus, individual types of pathogens microorganisms, parasites, etc.).

Until now the reference materials of the composition and properties of substances and materials are not equal to what is meant by reference material. Because, on the one hand, taking into account the provision of GOST 8.315-97 "Standard reference materials of the composition and properties of substances and materials. The main provisions of its certification procedure, the term "reference material" should correspond to the term "certified reference material", which should be accompanied by data on uncertainty and traceability when used for calibration and verification of correctness, at the same time, the term "standard reference material" is widely is used also for control materials for precision testing, for which no requirements for traceability and uncertainty are established, this term does not cover reference materials-candidates, etc. Therefore, in the DSTU-N ISO Guide 35: 2018 instead of the term "reference material" specified in the Law of Ukraine "On Metrology and Metrological Activity" (from 06/05/2014, No. 1314-VII, Article 1, Sections 1, 6 ), the key terms "reference material" and "certified reference material" are used directly,  based on the original document of ISO Guide 30: 2015 (E) and the Ukrainian translation of the International Vocabulary of Metrology. Basic and General Concepts and Related Terms (VIM) "(ISO / IEC Guide 99: 2007) - such as, in contrast to the previously used term" reference material ", in the proper way correspond to the original reference material of English text of ISO Guide 35: 2017, IDT International Standard), and it is not appropriate to use the term "reference material" in relation to the newly created reference materials.

Reference materials (RMs) must be used at all stages of the measurement process: during validation (evaluation of suitability) and verification (verification of conformity, approval) of measurement methods, during performing the calibration and in checking the calibration of measuring instruments and measurement systems, for assigning values to others materials, in the control of precision and accuracy of measurements for evaluating the qualifications of laboratories by performing interlaboratory comparisons, etc., since they are a source metrological traceability - a basic condition for ensuring comparability of measurement results and their use.

The DSTU-N Guide 35: 2018 gives the concepts and provides an understanding of homogeneity and stability evaluation and characterization in the certification of reference materials, contains specific technical recommendations on technical issues and explains the approach to the following aspects of the production of reference materials:

- homogeneity evaluation;

- Stability evaluation and risk management associated with possible stability issues associated with properties of interest;

- characterization and assignment of the value of the properties of the reference material;

- uncertainty evaluation for certified values;

- metrological traceability of certified values of properties.

This document provides a brief guide as for the need for evaluating commutativity, but without providing technical details. A brief introduction to characterizing qualitative properties is presented together with short recommendations for the selection of such materials for homogeneity tests. However, statistical methods for assessing homogeneity and stability do not cover reference materials for qualitative properties. This document also does not apply to multidimensional values, such as spectral data.

The new international standard ISO Guide 35: 2017 replaced the previously existing international standard ISO Guide 35:2009. In Ukraine, the DSTU-N ISO Guide 35:2018 is approved to replace the DSTU-N ISO Guide 35: 2006, effective until December 31, 2019.

Leading researcher                                                                                   A.Ivkov