Contral tasks for modern laboratories include ensuring the reliability of chemical and instrumental analysis results and meeting quality requirements. For this purpose, laboratories use certified reference materials (CRMs). According to the definition of the ISO 17034:2016 standard, CRMs are reference materials for which one or more properties have been characterized by a metrologically recognized procedure, and should be accompanied by a certificate specifying the value of the listed properties and the associated uncertainty, and confirming the maintenance of metrological traceability ^[1]. This means that CRMs are materials with an exceptional degree of homogeneity and a very well-selected and defined composition that serve as a reference point for laboratories worldwide ^[2].

Laboratories use CRMs in several key ways to ensure the accuracy and reliability of analytical results. They are used for (a) instrument calibration, ensuring measurement accuracy and traceability over time (including the development of new methods), (b) validation of new analytical methods, confirming that the methods produce reliable and accurate results, (c) routine quality control to monitor the performance of analytical methods and instruments, (d) proficiency testing and interlaboratory comparisons, where laboratories analyze the same CRM and compare results to ensure traceability, consistency, and accuracy across different laboratories, (e) training laboratory personnel, ensuring they can accurately perform analyses and interpret results, (f) procedure uncertainty estimation, (g) demonstration of regulatory compliance of results, (h) troubleshooting and detection of potential issues with instruments or reagents, and (i) stability studies for analytical instrumentation. Additionally, their usage in the above-mentioned areas supports the evaluation of laboratories and audits carried out by regulatory bodies.

The standardized system of units, known as the International System of Units (SI), was approved in 1960 at the General Conference on Weights and Measures. Since then, the standards or definitions associated with it have officially set reference points in many areas of life. Although it is straightforward to refer to a mass standard in classical gravimetric methods or a volume standard in volumetry, it is much more challenging to refer to SI units in instrumental techniques that rely, for example, on determining the interaction of electromagnetic radiation with matter. In these methods, the recorded signals from samples are compared with signals previously obtained for well-known reference materials. In this case, there arises a need for reference materials that, on the one hand, allow for the calibration of the apparatus, and on the other, prove it is operating correctly. This situation and the need for standardization have prompted various institutions to take actions to produce appropriate materials. Alongside the development of the market and producers, systemic development has progressed, requiring the establishment of universal standards. The International Organization for Standardization (ISO) has been involved for years in processes aimed at standardizing rules to ensure the metrological recognition of CRM systems. Further sections describe the standards system developed by the organization with the most important sets of guidelines—ISO Guide 30, ISO 33401:2024, ISO 33405:2024 ^[3][4][5], and ISO 17034:2016 ^[1], which replaced ISO Guide 34 ^[6]. According to ISO 17034 ^[1], reference material producers must meet a range of requirements regarding quality management, documentation, traceability, and certification. The process of producing reference standards must be strict and controlled to ensure that the resulting products comply with specified specifications and standards. Laboratories analyze very different samples, operating in various areas of industry and science, and therefore require different reference materials. Hence, producers offer CRMs in various forms with certified physical or chemical properties (biological, solution-based, solid, liquid, metal alloys, and many others). Whenever possible, laboratories choose CRMs with compositions corresponding to the real samples they analyze. In this context, it is often necessary to use matrix certified reference materials (mCRMs), i.e., those in which the matrix is defined and relevant from the point of view of the analytical methods used. Such materials are often used in the area of solid sample analysis and techniques where various matrix effects occur. Given the great diversity of analyzed materials, it cannot be expected that mCRMs will be commercially available for all types of matrices. Furthermore, the production process for matrix standards is complicated and often takes many years, resulting in limited offerings and a constant race in which standard producers strive to keep up with new materials produced in the industry. As a result of systemic changes and introduced standards (laboratories with a quality system implemented in accordance with ISO/IEC 17025 ^[7] are required to use certified reference materials produced by a manufacturer meeting the requirements of ISO 17034 ^[1]), interest in CRMs is steadily increasing. In the Scopus database, 75 documents were found under the keyword “Matrix certified reference materials” in the period of 1998–2025, with a significant increase in the number of scientific documents observed after 2018. By subject area, chemistry accounts for as much as 40% of all articles since the initiation of Scopus, followed by biochemistry (15.2%), engineering (9%), physics and astronomy (8.3%), chemical engineering (6.2%), and environmental sciences (5.5%). Other subject areas account for less than 5% ^[8]. Therefore, there is a need to ensure the availability of sufficient quantities of these materials. Among mCRM producers that compete on the global market, the following should be mentioned: NIST (National Institute of Standard and Technology, USA), LGC Standards (UK), BAM (Bundesanstalt für Materialforschung und-Prüfung, Germany), RIST (Research Institute of Industrial Science and Technology, Republic of Korea), KTR (Korea Testing and Research Institute), IRMM (Institute for Reference Materials and Measurements, European Union), and NMIJ (National Metrology Institute of Japan). Certified reference materials can be found by searching the Internet, but with the growth of the CRM market and the diversity of producers, finding the right choice has become difficult. This is why using a reference material database such as COMAR (platform of BAM) or CNRM (The National Sharing Platform for Reference Materials of China) can help users find materials more easily. For example, the COMAR database has 2030 CRMs with additional division by ISO 17034-accreditedCRMs (1218) ^[1] and CRMs from NMIs (national metrology institutes) (285). Moreover, it offers the function to search for CRMs by producer, material, properties, or fragments. In turn, the CNRM database can be divided by category or subcategory: ferrous metals (carbon steel, low-alloy steel, ferro-alloy, etc.), non-ferrous metals and gases (heavy metals and their alloys, light metals and their alloys, gases in metals, rare-earth element ores), geological materials (ore, rock), energy resources (coal, fuel, petroleum products), and many others. All of these are designed to help choose the right material.